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Breast cancer (BC) is among the most prevalent type of malignancy affecting females worldwide. BC is classified into different types according to the status of the expression of receptors such as estrogen receptor (ER), human epidermal growth factor receptor 2 (HER2), and progesterone receptor (PR). Androgen receptor (AR) appears to be a promising therapeutic target of breast cancer. Binding of 5α-dihydrotestosterone (DHT) to AR controls the expression of microRNA (miRNA) molecules in BC, consequently, affecting protein expression. One of these proteins is the transmembrane glycoprotein cluster of differentiation 44 (CD44). Remarkably, CD44 is a common marker of cancer stem cells in BC. It functions as a co-receptor for a broad diversity of extracellular matrix ligands. Several ligands, primarily hyaluronic acid, can interact with CD44 and mediate its functions. CD44 promotes a variety of functions independently or in cooperation with other cell-surface receptors through activation of varied signaling pathways like Rho GTPases, Ras-MAPK, and PI3K/AKT pathways to regulate cell adhesion, migration, survival, invasion, and epithelial-mesenchymal transition. In this review, we present the relations between AR, miRNA, and CD44 and their roles in BC.
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Breast Disease 1(2019) 1–12 1
DOI 10.3233/BD-190409
IOS Press
Role of CD44 in breast cancer
Nihad Al-Othmana,, Ala’ Alhendia, Manal Ihbaishaa, Myassar Barahmeha, Moath Alqaralehband
Bayan Z. Al-Momanyb
aDivision of Anatomy, Biochemistry, and Genetics, Faculty of Medicine and Health Sciences, An-Najah National
University, Nablus, Palestine
bSchool of Science, The University of Jordan, Amman, Jordan
Abstract. Breast cancer (BC) is among the most prevalent type of malignancy affecting females worldwide. BC is classified into
different types according to the status of the expression of receptors such as estrogen receptor (ER), human epidermal growth
factor receptor 2 (HER2), and progesterone receptor (PR). Androgen receptor (AR) appears to be a promising therapeutic target
of breast cancer. Binding of 5α-dihydrotestosterone (DHT) to AR controls the expression of microRNA (miRNA) molecules in
BC, consequently, affecting protein expression. One of these proteins is the transmembrane glycoprotein cluster of differentiation
44 (CD44). Remarkably, CD44 is a common marker of cancer stem cells in BC. It functions as a co-receptor for a broad diversity
of extracellular matrix ligands. Several ligands, primarily hyaluronic acid, can interact with CD44 and mediate its functions.
CD44 promotes a variety of functions independently or in cooperation with other cell-surface receptors through activation of
varied signaling pathways like Rho GTPases, Ras-MAPK, and PI3K/AKT pathways to regulate cell adhesion, migration, survival,
invasion, and epithelial–mesenchymal transition. In this review, we present the relations between AR, miRNA, and CD44 and
their roles in BC.
Keywords: Breast cancer, CD44, miRNA, hyaluronic acid, matrix metalloproteinase
1. Introduction
BC is the most prominent cause of mortality among
women in most developed countries[1]. It is deemed
to be a greatly heterogeneous group of cancers that
develop from varied cell types, each having its particu-
lar clinical consequences[2] and is composed of sev-
eral biologically various entities with discrete patho-
logical features and response to treatment[3,4]. There-
fore, the precise grouping of BC into clinically related
subtypes is of real importance for therapeutic deci-
sion[5]. Conventional Immunohistochemistry (IHC)
markers including estrogen receptor (ER), human epi-
dermal growth factor receptor 2 (HER2), and proges-
terone receptor (PR) are applied to patient progno-
sis and management[6,7]. The forthcoming of high-
throughput schemesof gene expression profiling have
*Corresponding author: Nihad Al-Othman, Division of Anatomy,
Biochemistry, and Genetics, Faculty of Medicine and Health Sci-
ences, An-Najah National University, Nablus, Palestine. Tel.: +970
598776995; E-mail:
revealed that tumor cell response to treatment is not
entrenched using anatomical predicted features, rather
fundamental molecular features that can be explored
using molecular techniques[4,8]. Therefore, during the
past 15 years, modulation of BC classifications has
been in progress from histopathological typing to the
molecular classification[5]. For instance, ER-positive
and ER-negative BCs comprise different diseases[9].
Besides, the existence of four essential subtypes of
BC including luminal A, luminal B, HER2-enriched,
and basal-like has been established[10]. The Cancer
Genome Atlas Network (TCGA) has designated a broad
profiling for BC at the DNA, RNA, and protein lev-
els[10] whereby the luminal BC subtype can be divided
into at least two subgroups, each with a distinctive
mRNA profile[11]. Each subtype manifests differ-
ent prognosis, incidence, treatment response, preferred
metastatic sites, and disease-free survival rates[12].
CD44 is an integral membranous protein with a
multi-structure and multi-functions. It been found to
play a role in tethering cells to the extracellular matrix
(ECM) via mediating complex formation between
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Effect of different exon number on CD44v characteristics
Variant exon number Features added to CD44
V1 Not expressed in human CD44 variants.
V2 Gives additional sites for O- and N-glycosylation[122].
V3 - Gives a motif for GAGs addition (as heparan sulfate that confers CD44 the ability to bind to heparin-binding
growth factors and chemokines)[122].
- Mediates cell-cell adhesion that was dependent on HA[123].
- Mediates Met receptor activation and binding to its ligands (SF/ HGF)[124]
V4 - Enhances phosphorylation of CD44 cytoplasmic tail[26]
V5 - Enhances malignancy and invasiveness of some tumors[125].
- Enhances phosphorylation of CD44 cytoplasmic tail[26].
V6 - Broadens the ligand specificity to include GAGs other than HA[126].
- Makes CD44 able to form a complex with hepatocyte growth factor (HGF) and its receptor Met[14].
- Enhances phosphorylation of CD44 cytoplasmic tail[26].
V7 - Mediates cell survival by osteopontin[127].
- Enhances phosphorylation of CD44 cytoplasmic tail[26].
V8 - Gives additional sites of O-lycosylation (its extensive O-glycosylation inhibits CD44 binding HA[122].
V9 - Gives additional sites of O-lycosylation (its extensive O-glycosylation inhibits CD44 binding HA[122].
V10 - Gives additional sites of O-lycosylation (its extensive O-glycosylation inhibits CD44 binding HA[122].
extracellular components and intracellular cytoskeletal
elements. This role is no less important than its function
in cellular signaling and cell-cell communication[13].
It senses the changes in ECM and cell’s microenvi-
ronment that in turn influences many cell aspects, for
example and not as a limitation: cell survival, growth,
differentiation and motility[14].
2. CD44 structure
As mentioned previously, CD44 consists of three
domains: the extracellular domain (ECD), trans-
membrane domain (TMD), and intracellular domain
(ICD)[15]. The ECD includes the amino termi-
nal globular domain where HA, glycosaminoglycans
(GAGs) and other ligands bind such as hyaluronic acid
(HA)[16]. The TMD is sponsible for CD44 oligomer-
ization[17]. Palmitoylation can occur reversibly for
that domain. Several studies reported that this mod-
ification could impair signal transduction in lympho-
cytes and promote CD44 association with ankyrin and
ezrin, radixin, and moesin (ERM) proteins[18,19].
The cytoplasmic domain, also called the ICD, has two
configurations, short- and long-tail configurations[20].
This domain is essential in many cellular aspects
including subcellular localization of CD44 into the
basolateral side of polarized epithelia[21] and lead-
ing edge of lamellipodia during cell migration, sig-
naling, cytoskeletal organization and gene transcrip-
tion[22]. A number of factors, such as mitogens and
membrane-type 1 matrix MMP (MT-1 MMP), promote
the cleavage of cytoplasmic tail[20]. Translocation of
that cleaved tail into the nucleus influences the tran-
scription of many genes including CD44 itself in a pos-
itive feedback pattern[23]. The cytoplasmic domain
displays a divergent role in signaling. It alters CD44
affinity to bind ligands “inside-out signaling” and also
mediates downstream signaling upon CD44 binding
ligands “outside-in signaling”[19].
3. CD44 isoforms
The mechanisms that account for heterogeneity of
CD44 are alternative splicing, N-glycosylation, O-
glycosylation and palmitoylation[24,25]. CD44 gene is
composed of 20 exons. Exons (1–5), (16–18) and (20)
produce CD44s (the long-tail configuration), which is
the smallest compared to other isoforms. Exons 6–15,
designated as (v1-10), are variable with various combi-
nations produced by alternative splicing The addition of
one or more of the exons (v2-v10) to CD44s generates
other CD44 isoforms with larger molecular mass (up
to 381 amino acids long). Take into consideration that
expressing v1 exon would yield a truncated protein
due to presence of a stop codon and therefore, it is
not expressed in human CD44v[26]. Table1 displays
the different features of CD44v depending on its exon
Whether post translation modification or the alter-
native splicing affects the binding affinity of CD44 or
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increases its affinity for its ligands is not clear. How-
ever, what is clear is that both processes are depen-
dent on cell type, cell growth condition, environment,
and oncogenic pathways such as the Ras-MAPK cas-
cade[24,27]. Though, CD44s is expressed remarkably
in most tissues, whereas CD44 variants are expressed
mainly in tumor cells[15,24]. On the other hand, other
studies have reported that CD44 variants are expressed
in normal and the tumor cells at different levels sug-
gesting that they are also necessary for normal cellu-
lar functions[28,29]. CD44s and its variants take part
in cancer invasiveness. For instance, CD44v8-10 and
CD44v9 are expressed in high amounts in pancreatic
and colorectal cancers respectively[20]. CD44v6 and
soluble (cleaved) CD44 were seen in prostate cancer
cell derived from bone metastasis. Switching between
CD44 isoforms, as observed in prostate cancerous
cells when CD44s is replaced by CD44v6, promotes
adhesion and survival[30]. Comparing benign with
the malignant forms of prostate cancer, CD44v5 and
CD44s are highly expressed in these forms, respec-
tively[31]. A few studies showed that CD44v promotes
some cancer types progression and metastasis[32,33],
while others indicated that they are tumor suppressors
in other types of cancers[34,35]. This discrepancy
of findings may stem from applying different means
for detecting CD44 (e.g. polymerase chain reaction or
IHC) or using different primary anti-CD44 antibod-
ies that may not recognize the CD44v epitopes[29].
For more detailed information regarding some cancer
type’s relation with CD44v, see Table2.
4. CD44 ligands
Several ligands can interact with CD44 and mediate
its functions. Osteopontin, collagens, growth factors,
fibronectin and MMP can bind to CD44, although HA
is the principal one[20].
4.1. HA
HA is one of the mucopolysaccharides or GAGs
found mainly in the ECM, pericellular matrix, and can
be found intracellularly[36]. It is an unbranched, non-
sulfated, anionic heteropolysaccharide with a molec-
ular weight up to 10,000KDa[24]. HA is composed
of a repeated units of disaccharide; β-D-glucuronic
acid and D-N-acetylglucosamine and is abundant in
soft connective, epithelial and neural tissues[36]. It is
synthesized by an integral membrane enzyme called
hyaluronic acid synthase (HAS) followed by a direct
release into the ECM[37]. Many cells have the abil-
ity to synthesize HA, but mesenchymal cells are the
main ones[38]. Using CD44-nul COS-7 cells trans-
fected with human CD44s plasmids, cells gained HA-
binding ability and were able to internalize a conjugated
HA[39,40]. This experiment strengthens the idea that
HA turnover and internalization correlate with CD44
expression level. Researchers exploit that notion in their
attempt to improve cancer treatment by conjugating
drugs to HA to improve its delivery and internaliza-
tion into cancerous cells that have high expression of
The enzymes that are involved in HA degradation
are hyaluronidases (HYALs), β-d-glucuronidase, and
β-N-acetyl-hexosaminidase[37]. These enzymes are
found intracellularly and in the serum. HYALs cleave
high molecular weight HA (HMW) into smaller lower
molecular weight (LMW) oligosaccharides while β-
d-glucuronidase and β-N-acetylhexosaminidase addi-
tionally degrade the oligosaccharide fragments[36].
Some studies defined HMW HA as HA molecule
with a molecular mass >500KDa. Human HYALs are
encoded by six genes: hyall1, hyal2, and hyal3[37].
HYAL1 and HYAL2 are the main hyaluronidases in
most tissues; HYAL2 is responsible for cleaving HMW
HA that is bound to CD44 receptor. The resulting HA
fragments are further degraded by HYAL1 generating
HA oligosaccharides[42].
HA can perform many functions. It binds to a num-
ber of keratin sulfate and chondroitin sulfate molecules
and from proteoglycan aggregates in the ECM. If it
is not linking with other molecules, it will bind to
water and maintains tissue hydration and osmotic bal-
ance[36]. HA contributes in many other physiolog-
ical and pathological cellular processes such as cell
adhesion, migration, cancer progression and inflam-
mation[36,38]. CD44 can bind HA and mediates a
host of cellular functions[36]. Furthermore, most of
HA functions in most tissues are related to CD44-HA
interactions[36]. Based on CD44 affinity to HA, CD44
can be classified into three forms: the low affinity form
that is expressed in normal cells[43], the inflammation-
induced high affinity form, and the constitutive high
affinity form that is expressed all the time in cancerous
In addition, several studies have reported that many
of HA effects are related to its molecular weight.
HMW-HA provokes distinct effects compared to those
mediated by LMW-HA on the same cell. For exam-
ple, LMW-HA reduces CD44 clustering and increases
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Contribution of CD44v in different type of cancer
Cancer type CD44 isoform Isoform contribution
Colorectal Cancer CD44v3 - Activates invasion and resistance to apoptosis.
CD44v6 - Associated with tumor metastasis.
- Essential for their migration and generation of metastatic tumors[30,128,129].
CD44v8–10 - Has a role in metastasis[130].
CD44v2 - Is overexpressed & upregulated in CRC.
- Significantly worse prognosis[131].
Lung cancer CD44v5
- Promotes squamous cell carcinoma metastasis In[132,133].
- Are expressed in non-small cell lung carcinomas[134,135].
- CD44v6 is associated with lymph node metastasis and poor survival[136,137].
Breast Cancer CD44v3, CD44v5, and
- Promotes metastasis[138].
CD44v5, CD44v6, and
- Are associated with axillary lymph node metastasis[139].
CD44v3 - Enhances metastases to the lymph nodes[140].
- High expression is correlated to positive steroid receptor status, low proliferation,
and luminal A subtype[114].
CD44v8-10 - Is correlated to positive EGFR, negative/low HER2 status, and basal-like
Leukemia CD44v3,
CD44v6, CD44v9, and
- Are expressed in bone marrow progenitors[141].
CD44v3, CD44v6, and
- Are expressed in lymphocytes and monocytes following stimulation with
inflammatory cytokines[141].
lymphoma and myeloma
CD44v6, CD44v9, and
- Are overexpressed and associated with poor prognosis[142].
Acute myeloid leukemia CD44v6 - Is associated with poor prognosis and shorter survival rate[142].
Pancreatic Cancer CD44v6 - Is expressed in primary and metastatic human pancreatic CA[143].
CD44v5 - Is strongly expressed on adenocarcinomas[144].
CD44v6 And
- Are expressed on tumor cells and correlated with decreased overall survival[145].
- Promotes metastasis
- CD44v6 is a risk factor affecting overall survival[146].
CD44v9 - Their expression is upregulated[147].
Head and Neck Cancer CD44v3 - Leads to a significant increase in migration[148].
CD44v3, CD44v6, and
- Are associated with lymph node metastasis, perineural invasion, decreased
survival, distant metastasis and radiation failure[149,150].
CD44v6 - Is correlated with tumor invasion, lymph node metastasis, and shorter
Prostate cancer CD44v6 - Promotes cell survival[30]
cell adhesion, while HMW-HA induces CD44 clus-
tering[24,45]. It is the vast length of HMW-HA that
enables it to bind and bridge higher number of receptors
over large cell area[36]. HMW-HA stimulates Ras-
CD44 in ovarian tumor cell[46], inhibits tumor growth
in schwannomas[47] as well as inhibits neovascu-
larization in breast cancerous cells[20]. Furthermore,
HMW-HA fragments have anti-inflammatory role[48]
and support tissue integrity[36,48]. In contrast, LMW-
HA stimulates expression of genes required for inflam-
mation[49]. In cancer cells, LMW-HA suppresses anti-
apoptotic signaling pathways and inhibits the activ-
ity of transporters that enhances multidrug resistances
to some chemotherapeutic agents[50,51], inhibits
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Functions of HMW-HA and LMW-HA
LMW-HA roles HMW-HA roles
Reduces CD44 clustering[24,45]. Induces CD44 clustering[24,45].
Provokes an inflammatory response and stimulates expression of genes
required for inflammation[48,49].
Has anti-inflammatory role and supports tissue integrity[48].
Induces wound site inflammation and scar formation[38]. Induces wound healing with minimal inflammation and scar
Induces tumor regression[53]. Inhibits tumor growth in schwannomas[47].
Interrupts HA-CD44 interaction in breast CA → Inhibits cell growth,
motility, and invasion[55].
Bridges high number of receptors over large cell area[36].
Enhances CD44 break down and angiogenesis[27]. Inhibits neovascularization[152].
Suppresses anti-apoptotic signaling pathways in cancer cells[50,51]. Stimulates Ras-CD44 in ovarian tumor cell[46].
Inhibits HA synthesis[52]. Limits viral infections of further neighboring T- cells[48].
Inhibits multidrug resistances transporter[50,51].
Disassembles CD44-multidrug transporter complex and tyrosine kinase
receptor complexes[52].
HA synthesis[52] and induces tumor regression[53].
Moreover, LMW-HA leads to the “degradation of
CD44-multidrug transporter complex and receptor
tyrosine kinase (TRK) complexes, internalization of
these disassembled structures, and sapping of their
role”[52]. Furthermore, LMW-HA blocks dissemi-
nation of an ovarian cancer cells who are induced
artificially to metastasize[54]. Disaccharides of HA
compared to HMW-HA and other HA oligosaccha-
rides fragments/length shows the ability to inhibit cell
growth, motility, and invasion significantly in BC via
disturbance of the interaction of endogenous HA-CD44
complex[55]. LMW-HA enhances CD44 break down
and angiogenesis and attenuates cell adhesion in breast
cancer[20]. Note that studies that discussed LMW-
and HMW-HA cellular effects did not define the type
of receptor that is involved in their functions[24].
Table3 summarizes functions of both HMW-HA and
5. Role of CD44 and HA in cancer signaling
CD44 promotes a variety of functions independently
or in cooperation with various cell-surface receptors
through triggering a number of signaling pathways
via Rho GTPases, Ras-MAPK, and PI3K/AKT among
others[24,56]. CD44 functions as a growth or arrest
sensor according to signals from the microenviron-
ment that can influence cancer progression[57]. The
protein directly intercedessignal transduction pathways
through triggering of LMW-HA when bound to CD44.
It also recruits signaling mediators to the cytoplasmic
tail of CD44 that controls the activity of regulatory
signaling molecules such as Tiam1, p115, Rac1, Rho
GEFs, Rho-associated protein kinase, and cSrc[27].
Interactions with these signaling proteins lead to induc-
tion of the PI3K pathway that activates a number of cel-
lular behavior including cell survival and invasion[58].
In addition, CD44 stimulates RhoA independently of
HA binding, which triggers CD44 involvement with
ankyrin resulting in creation of membrane projections
and stimulation of migration[59]. Furthermore, CD44
mediates actin cytoskeleton remodeling and invasion by
interaction with ERM protein complex. The latter com-
plex induces the re-formation of the actin cytoskele-
ton and facilitates cell adhesion cell motility[60]. The
ERM proteins compete with another protein known
as merlin, which acts as a tumor suppressor. Through
binding to CD44 cytoplasmic tail, merlin can either
facilitate or inhibit cell growth and motility. In addi-
tion to HMW-HA, merlin combines with CD44 shift-
ing ERM and, subsequently, suppressing Ras path-
way[61]. Activation of PI3K leads to phosphorylation
and deactivation of merlin by p21-associated kinase
(Pak2), which obstructs merlin binding to CD44. As
a result, ankyrin and ERM proteins become free to
bind CD44 cytoplasmic tail to the actin cytoskeleton
enhancing cell invasion[62]. Several studies revealed
that collagen-embedded HMW-HA can hinder the
induction of epidermal growth factor receptor (EGFR)
and inhibitfilopodia formation in MDA-MB-231 cells
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grown on collagen[63]. Merlin attaches to CD44 and
prevents ERM, N-Wasp, and Grb2 complexing, which
leads to inactivation of Ras pathway and suppression
of cell invasion, motility, and growth[27]. Alteration
of CD44-mediated biology is a result of the expression
of differentially spliced isoforms; alternative expres-
sion has been proposed to be associated with amplified
metastatic behavior[27,64].
Furthermore, CD44 inhibits cancer progression,
whereby when it attaches to merlin, it functions as
a growth/arrest sensor in relation to signals from the
microenvironment and has a function in contact repres-
6. Androgen receptor (AR)
AR is a member of the steroid hormone nuclear
receptors family that also includes ER and PR[66–
68]. Although the main functions of androgens and
their receptor are associated with male sexual differ-
entiation, AR and its ligands, testosterone and its more
potent product, dihydrotestosterone, are critical in the
development of the mammary gland. Androgens effect
various sites throughout the body: the hypothalamus
and amygdala in the brain, breast, bone, skin, adipose
tissues, skeletal muscles, vascular and genital tissues,
and in women ovaries and extra-gonadal tissues in
which androgens are the essential precursors for estro-
gen biosynthesis[69,70]. Thus, androgens influence
sexual desire and function, mineral density in bones,
muscle mass and strength, the distribution of adipose
tissue, energy, mood and psychological well-being as
7. AR expression in BC
AR expression has been identified in 60–85% of
breast tumors[72]. However, the expression of AR is
different among the different subtypes. Approximately
70 to 90% of ER-positive cancers are AR-positive
as well[73,74]. Indeed, there is a significant associ-
ation between the expression of both ER and AR. In
addition, approximately 60% of ERBB2-positive breast
cancers overexpress AR[73,75]. On the other hand,
the prevalence of AR expression in triple-negative BC
(TNBC) is less frequently reported, ranging from 13 to
65%[76]. This variability may be due to the differences
in the techniques or criteria used to define AR positiv-
8. AR as a therapeutic target
Historically, androgens such as fluoxymesterone,
testolactone, and calusterone were used for the treat-
ment of advanced breast cancer resulting in about 18–
39% clinical responses[78]. However, the undesirable
masculinity side effects of these agents have limited
their routine use in the treatment of breast cancer
especially in the advent of newer, less toxic endocrine
agents. There is a renewed interest in the use of AR-
targeted agents in the treatment of breast cancer given
the improvement in treating prostate cancer using such
agents and the significance of AR signaling pathway in
breast cancer. This is true particularly for TNBC. The
fact that AR-positive TNBCs have preserved andro-
genic signaling suggests that AR can be used as a
possible therapeutic target similar to ER-positive breast
cancer targeting[79,80]. However, the use of AR as
a potential therapeutic target in breast cancer has yet
to be established due to the difficulties in both the
identification of the patients who might be benefit
from AR-targeted therapies and the development of the
right combination of therapeutic agents based on AR-
targeted therapies[73,75,81].
9. Androgen regulation of miRNA
miRNAs are short, single-stranded, non-coding
RNA molecules of 20–25 nucleotides that are widely
conserved among species[82]. They regulate cell func-
tion via negatively targeting the stability of mRNAs
and/or their use in protein synthesis. Interestingly, a
correlation has been found in the expression of miR-
NAs in androgen-dependent and independent prostate
cancers, in addition to benign and malignant prostate
tissues[83]. In addition, miRNAs have been found to
regulate the long AR 3’untranslated region (UTR)[84],
suggesting a functional regulation by AR. This is not
surprising given that primary function of AR as a tran-
scription regulatory protein.
More than 50% of all human gene translation is
thought to be regulated by miRNA[85]. This extra
level of gene regulation is involved in the cell signaling
pathways in both normal and tumor tissues[86,87].
Moreover, each miRNA can regulate numerous target
genes, and, vice versa, the same target gene can also
be regulated by several types of miRNAs, creating a
complex network[88–90]. It is of note that miRNA
is not always associated with inhibitory or down reg-
ulatory effects. In rare circumstances, depending on
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the cell cycle and protein co-factors, a miRNA can
activate mRNA translation and, hence, increase protein
levels[91]. The inherent complexity of this regulatory
system allows miRNAs to control the global activity
of the cell, including cell differentiation, proliferation,
stress response, metabolism, cell cycle, apoptosis, and
Different miRNA expression profiles between can-
cerous cells and paired normal tissues from the same
organ and cancer types have been documented in a
number of studies[92,93]. Some miRNAs are down-
regulated in a number of different tumors, and their re-
introduction weakens the viability of cancer cells since
they function as tumor-suppressor genes with an anti-
proliferative and pro-apoptotic activity role[92,93]. In
contrast to the tumor-suppressor miRNAs, oncogenic
miRNAs, oroncomiRs, display an antiapoptotic activity
and are over-expressed in cancer cells. Therefore, alter-
ations in the expression of these miRNAs can stimulate
In 2011, Waltering etal.examined androgen regula-
tion of miRNAs using one of the first miRNA microar-
ray showing that DHT positively regulates 17 miRNAs
in metastatic prostate VCaP tumor cells and causes
high expression in 42 miRNAs[94]. Further works
by several independent groups have demonstrated
that miRNAs such as miR-19a, miR-148, miR-27a,
miR-125b, miR-135a, MiR-32 and miR-21 are andro-
gen inducible[95–101]. Other miRNAs are down-
regulated by androgens such as the well-established
oncogenes miR-221 and miR-222, which are located
on the X chromosome and are over-expressed in pan-
creatic, breast, liver, and lung cancer[100,102,103].
Other miRNAs that are down-regulated by andro-
gens include miR-126-5p, miR-146b, miR-219-5p,
miR181b-1, miR-181c, and miR-221[104].
On the other hand, many studies have examined the
role of miRNAs in controlling the AR pathway. Using
a miRNA library, Ostling etal.reported the ability of
71 unique miRNAs to influence the function of AR
with 52 decreasing and 19 increasing its RNA and pro-
tein levels[84]. Since then, several miRNAs have been
described to have a role in the regulation of AR activity
directly or indirectly via co-regulators[105,106]. MiR-
205 was found to exhibit a negative correlation to AR
through binding to the receptor’s 3’UTR and decrease
its transcript and protein levels[107], and there is a sta-
tistically significant inverse association exists between
miR-34a and AR[84]. In addition to those examples,
let-7c determines prostate tumor suppression through
AR, and this mechanism is linked to the capability
of this tumor-suppressing miRNA to target c-MYC, a
molecule that is required for the correct transcription
of AR[108].
However, miRNAs do not only have direct effects,
rather they can use alternative routes to control andro-
gen signaling such as those mediated by the ERBB-
2 and PI3K/AKT. The tyrosine receptor ERBB-2 is
often elevated in prostate cancer, whereas the activation
of PI3K/AKT signaling is associated with prolifera-
tion, metastasis, apoptosis resistance and angiogenesis
in prostate cancer[109]. The latter study has shown
that the 3-UTR of ERBB-2 mRNA contains two spe-
cific target sites for miR-331-3p, which suppresses the
expression of ERBB-2 at both the transcript and protein
levels. The same group also illustrated that miR-331-
3p is involved in the downstream PI3K/AKT signal-
ing in multiple prostate cancer cell lines[109]. MiR-
488* directly affects AR signaling by targeting the 3-
UTR of AR and down-regulates AR protein expression
in both androgen-sensitive and -insensitive prostate
cancer cells inhibiting cellular growth and inducing
apoptosis[110]. Another miRNA miR-17-5p, has been
shown to target PCAF, a coactivator of AR, and to
support the development of prostate tumor[111].
10. AR and CD44
Treatment of breast MDA-MB-231 cancer cells with
DHT alters CD44 expression at both the RNA and
protein levels[112]. The expression of the different
variants of CD44 is regulated at the post-transcriptional
level. Moreover, MDA-MB-231 cells express elevated
levels of CD44 in contrast to other BC cell lines[113].
The high levels of CD44 could be due to the large
number of miRNA types such as miR-512-3p, miR-
328, miR-491, and miR-671 that bind to 3’UTR of
CD44 in these cells[86]. The levels of these miR-
NAs could also be regulated by DHT. Understanding
the role of CD44 in cancer progression must take in
consideration the existence of different CD44 isoforms
as the antibodies in the majority of the earlier studies
identifies an epitope located in a non-variable region of
CD44 of cancer stem cells, so they cannot differentiate
between different CD44 isoforms[114]. Not all CD44
proteins bind to HA. In facts, three isoforms of CD44
cannot interact with HA unless activated by physio-
logical stimuli, and constitutive binding[115]. CD44
switching from the inactive state (low-affinity incapable
of binding and internalizing HA) to the active state
(high-affinity with ability to bind and internalize HA)
uncorrected proof version
8N. Al-Othman etal./Role of CD44 in breast cancer
miRNAs that regulate CD44 expression in BC cells
miRNA Role in BC Experimental model Reference
miR-143 Increase in S-phase population of cancer cells
Reduces stem cell properties such as:
self-renewal and sphere formation abilities
Reduces cancer cell proliferation (in vivo)
Suppresses epithelial-mesenchymal transition
and metastasis
Tested on BT474, MDA231, MDA468, MCF7,
SUM102 and SKBR3 human breast cancer cell line
in vitro
miR-373 Increase invasion and migration by suppressing
CD44, promoting metastasis
No effect on cell cycle or cell proliferation
Tested on MCF-7 human breast cancer cell line
in vitro and in vivo (transplanted into SCID mice)
Expressed by MDA-MB-435 human breast cancer
cell line and DU-145 human prostate cancer cell
line and is responsible for their migratory ability
Overexpressed by lymph-node metastatic breast
cancer samples compared to primary tumors
miR-520c Increase invasion and migration by suppressing
CD44, promoting metastasis
No effect on cell cycle or cell proliferation
Tested on MCF-7 human breast cancer cell line
in vitro and in vivo (transplanted into SCID mice)
miR-34a Inhibits tumor growth and survival
Induces cell cycle arrest and senescence
Reduces metastasis (in vivo) and invasion
Inhibits stem cell properties like holoclone and
sphere formation
LAPC4, LAPC9 &Du145 xenograft models of
human prostate cancer in vitro
In vivo models of prostate cancer in NOD-SCID
SCID: severe combined immunodeficiency
NOD: non-obese diabetic
requires posttranslational modification including gly-
cosylation of the extracellular domain and/or phospho-
rylation of specific serine residues in the cytoplasmic
domain[26,116]. This modification is vital for cellular
migration that allows CD44 to be inserted into the
leading border of the cells and lamellipodia[117].
11. MiRNA and CD44
Seventy miRNAs control CD44 expression levels in
different tissues[118]. Different types of miRNAs reg-
ulate the expression of CD44 (Table4). A study on BC
MCF-7 cells showed another HA/CD44 signaling path-
way that is initiated by activation of protein kinase C
(PKC). The latter kinase promotes phosphorylation of
the stem cell marker Nanog, which is a transcriptional
growth factor that plays a role in the self-regeneration of
pluripotency in embryonic stem cells. Phosphorylated
Nanog can then translocate from the cytosol into the
nucleus and associate with RNAase III (DROSHA)
and the RNA helicase (p68), which together lead to
up-regulation of miRNA-21. The latter molecule then
down-regulates the tumor suppressor protein, program
cell death 4 (PDCD4), induces expression of inhibitor
of apoptosis protein (IAPs) as well as X-linked inhibitor
of apoptosis protein (XIAP), and promotes chemore-
sistance by stimulating the expression of MDR1 (P-
Recently, numerous miRNAs have been identified to
affect cancer progression; miRNA-143 directly binds
the 3’ UTR region of CD44 resulting in reduction of
its expression and the capability of BC cells to metas-
tasize. These effects are as a result of the tumor sup-
pressing activity of miRNA-143[120]. Furthermore, it
has been found that miRNA-520a-3p acts as a tumor
suppressor and CD44 gene as one of its targets in BC
tissues and numerous cell lines including MCF-7 and
MDA-MB-231 cells[121].
12. Conclusion
CD44 is an integral membranous protein with a
multi-structure and multi-functions. The multifunc-
tional glycoprotein CD44 can undergo alternative splic-
ing events to produce CD44 variant isoforms that are
more restricted in their distribution as compared to the
standard CD44 isoforms. Different CD44 isoforms are
expressed differentially in different types of cancers.
The binding of CD44 to its ligand “HA” has a major
function in BC progression, cell adhesion, behavior,
uncorrected proof version
9N. Al-Othman etal./Role of CD44 in breast cancer
motility, and morphology. In addition, various miR-
NAs regulate CD44 expression via binding of DHT
to AR. As a result, alteration in the expression of
miRNAs that control CD44 expression can influence
tumorigenicity of BC and other types of cancer.
Conflict of interest
There is no conflict of interest to declare.
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... The important domain in the formation of isoforms is the extracellular domain. Diffe rent variants arise due to alternative splicing occurring in the exons of this domain [6,7]. ...
... CD44v is associated inflammation and various types of cancer. Also up-regulation of CD44v promotes tumor progression and metastasis [6]. ...
... The decrease in CD44 suggested that it decreased the motility of the cells in both cell lines. As a matter of fact, it has been reported that there are different variants of CD44 and that CD44v5, CD44v6, CD44v8-10 from these variants show different expression in breast cancer [6]. In addition, Afifiy et al. indicated that CD44s and CD44v6 play a role in breast cancer cell adhesion, motility and invasion through their interaction with Hyaluronic acid (HA). ...
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Background. Hyaluronan receptors play a role in various types of cancer. However, the changes oc- curring in CD44 and RHAMM after rapamycin administration are waiting to be explained. We aimed to investigate the changes in the hyaluronic acid receptors CD44 and RHAMM after rapamycin was administered in MCF-7 and MDA-MB-231 cell lines. Materials and methods. MCF-7 and MDA-MB-231 cell lines were cultured un- der standard conditions. The cell lines were stained with primary antibodies of CD44 and RHAMM to show the proteins. The H-score values were determined by the intensity of immunoreactivity. QRT-PCR was used to detect the expression of CD44 and RHAMM. Results. In the MCF-7 and MDA-MB-231 cell lines, the immunoreactivity of CD44 and RHAMM decreased at the 24th hour after rapamycin administration compared to the control group. According to the qRT-PCR results, the expression of CD44 (p < 0.033), and RHAMM (p < 0.0002) decreased in the rapamycin group compared to the control group. Conclusions. Rapamycin reduced the effect of hyalorunan receptors on breast cancer cell lines. Thus, the importance of the extracellular matrix in breast cancer has emerged once again.
... CD44 alongside receptor tyrosine kinase (RKT) articulates breast CSCs differentiation and migration. Its impeding results in hindering properties of breast CSCs such as cell adhesion, malignancy, progression, metastasis, EMT, and drug resistance (Al-Othman et al., 2020). Hence CD44 is regarded as a predictive marker in breast CSCs mediated resistance. ...
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Breast cancer (BC) is the most prevalent neoplasm among women. Genetic and environmental factors lead to BC development and on this basis, several preventive – screening and therapeutic interventions have been developed. Hormones, both in the form of endogenous hormonal signaling or hormonal contraceptives, play an important role in BC pathogenesis and progression. On top of these, breast microbiota includes both species with an immunomodulatory activity enhancing the host’s response against cancer cells and species producing proinflammatory cytokines associated with BC development. Identification of novel multitargeted therapeutic agents with poly-pharmacological potential is a dire need to combat advanced and metastatic BC. A growing body of research has emphasized the potential of natural compounds derived from medicinal plants and microbial species as complementary BC treatment regimens, including dietary supplements and probiotics. In particular, extracts from plants such as Artemisia monosperma Delile, Origanum dayi Post, Urtica membranacea Poir. ex Savigny, Krameria lappacea (Dombey) Burdet & B.B. Simpson and metabolites extracted from microbes such as Deinococcus radiodurans and Streptomycetes strains as well as probiotics like Bacillus coagulans and Lactobacillus brevis MK05 have exhibited antitumor effects in the form of antiproliferative and cytotoxic activity, increase in tumors’ chemosensitivity, antioxidant activity and modulation of BC – associated molecular pathways. Further, bioactive compounds like 3,3’-diindolylmethane, epigallocatechin gallate, genistein, rutin, resveratrol, lycopene, sulforaphane, silibinin, rosmarinic acid, and shikonin are of special interest for the researchers and clinicians because these natural agents have multimodal action and act via multiple ways in managing the BC and most of these agents are regularly available in our food and fruit diets. Evidence from clinical trials suggests that such products had major potential in enhancing the effectiveness of conventional antitumor agents and decreasing their side effects. We here provide a comprehensive review of the therapeutic effects and mechanistic underpinnings of medicinal plants and microbial metabolites in BC management. The future perspectives on the translation of these findings to the personalized treatment of BC are provided and discussed.
... CD44 is a membrane receptor that interacts with several molecules and displays hyaluronic acid as its main ligand [131]. In the breast, CD44 is a marker of cancer stem cells and is related to propagation, metastasis and resistance to chemotherapy [132]. To target CD44, Alshaer et al. constructed aptamer-guided liposomes containing siRNA against the luciferase gene [133]. ...
Ligand-mediated targeting represents the cutting edge in precision-guided therapy for several diseases. Surface engineering of nanomedicines with ligands exhibiting selective or tailored affinity for overexpressed biomolecules of a specific disease may increase therapeutic efficiency and reduce side effects and recurrence. This review focuses on newly developed approaches and strategies to improve treatment and overcome the mechanisms associated with breast cancer resistance.
... In TNBC, several targets have been exploited such as the CD44 receptor, a cell adhesion membrane glycoprotein overexpressed on many cancer types including triple-negative breast cancer [176], or EGFR-1 receptors. Hyaluronic acid is a CD44 receptor ligand, and, for this reason, it is grafted on the surface of polymeric nanosystems to obtain their selective localization in these cancer cells. ...
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Breast cancer is one of the most frequently diagnosed tumors and the second leading cause of cancer death in women worldwide. The use of nanosystems specifically targeted to tumor cells (active targeting) can be an excellent therapeutic tool to improve and optimize current chemotherapy for this type of neoplasm, since they make it possible to reduce the toxicity and, in some cases, increase the efficacy of antineoplastic drugs. Currently, there are 14 nanomedicines that have reached the clinic for the treatment of breast cancer, 4 of which are already approved (Kadcyla®, Enhertu®, Trodelvy®, and Abraxane®). Most of these nanomedicines are antibody–drug conjugates. In the case of HER-2-positive breast cancer, these conjugates (Kadcyla®, Enhertu®, Trastuzumab-duocarmycin, RC48, and HT19-MMAF) target HER-2 receptors, and incorporate maytansinoid, deruxtecan, duocarmicyn, or auristatins as antineoplastics. In TNBC these conjugates (Trodelvy®, Glembatumumab-Vedotin, Ladiratuzumab-vedotin, Cofetuzumab-pelidotin, and PF-06647263) are directed against various targets, in particular Trop-2 glycoprotein, NMB glycoprotein, Zinc transporter LIV-1, and Ephrin receptor-4, to achieve this selective accumulation, and include campthotecins, calicheamins, or auristatins as drugs. Apart from the antibody–drug conjugates, there are other active targeted nanosystems that have reached the clinic for the treatment of these tumors such as Abraxane® and Nab-rapamicyn (albumin nanoparticles entrapping placlitaxel and rapamycin respectively) and various liposomes (MM-302, C225-ILS-Dox, and MM-310) loaded with doxorubicin or docetaxel and coated with ligands targeted to Ephrin A2, EPGF, or HER-2 receptors. In this work, all these active targeted nanomedicines are discussed, analyzing their advantages and disadvantages over conventional chemotherapy as well as the challenges involved in their lab to clinical translation. In addition, examples of formulations developed and evaluated at the preclinical level are also discussed.
... [12][13][14][15] CD44 facilitates the development of cancer through activating central key signaling pathways, including the renin-angiotensin system (RAS)/MAPK/ERK, Rho Rho guanosine triphosphate hydrolases (GTPases), and PI3K/ protein kinase B (AKT) pathways. 16,17 As one distinctive MAPK cascade, the MAPK/ERK cascade is primarily described as a transducer of extracellular signals and it participates in the regulation of several fundamental processes such as proliferation, migration, metabolism, differentiation, and angiogenesis. [18][19][20] Here, we focus on the expression, clinical significance, biological roles, and underlying molecular mechanisms of PDRG1 in GBM. ...
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P53 and DNA damage-regulated gene1 (PDRG1) is overexpressed in diverse carcinomas. Here, we discover that PDRG1 is overexpressed in glioblastoma multiforme (GBM). However, the clinical significance, biological role and underlying molecular mechanisms of PDRG1 in GBM remain unclear. PDRG1 was aberrantly overexpressed in glioma, especially prevalent in GBM and correlated with poor clinicopathologic features of glioma. The risk score, operational feature curve analysis, Kaplan-Meier curve, univariate and multivariate cox regression analysis indicated that PDRG1 was an independent prognostic indicator and significantly correlates with disease progression of glioma. A prognostic nomogram was constructed to predict the survival risk of individual patient. The function and pathway enrichment analysis of PDRG1 in TCGA cohort was performed. PDRG1 knockdown significantly inhibited the migration and proliferation of GBM cells in vitro and in vivo. Transcriptome sequencing analysis of PDRG1 knockdown U118 cells indicated that biological regulation adhesion, growth and death, cell motility, cell adhesion molecular and proteoglycans in cancer were significantly enriched. Importantly, we found that the expression of adhesion molecule CD44 was regulated by PDRG1 in GBM. We found that PDRG1 promoted the migration and proliferation of GBM cells via MEK/ERK/CD44 pathway. Our findings provide proof that PDRG1 upregulation predicts progression and poor prognosis in human gliomas especially in IDH wt glioma patients. The study provides new evidence that PDRG1 regulates the expression of CD44 in GBM cells and might promote the migration and proliferation viaMEK/ERK/CD44pathway. PDRG1 might be a novel diagnostic indicator and promising therapeutic target for GBM.
... The CD44 is an essential molecular marker of cancer stem cells in breast cancer. The CD44 is expressed on the surface of highly metastatic breast cancer cells as a co-receptor for a broad diversity of extracellular matrix ligands, primarily HA [41]. Recently, a paper demonstrated that the interaction of HA with CD44 activates AMPK and autophagic pathways [42]. ...
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The microenvironment for tumor growth and developing metastasis should be essential. This study demonstrated that the hyaluronic acid synthase 3 (HAS3) protein and its enzymatic product hyaluronic acid (HA) encompassed in the subcutaneous extracellular matrix can attenuate the invasion of human breast tumor cells. Decreased HA levels in subcutaneous Has3-KO mouse tissues promoted orthotopic breast cancer (E0771) cell-derived allograft tumor growth. MDA-MB-231 cells premixed with higher concentration HA attenuate tumor growth in xenografted nude mice. Human patient-derived xenotransplantation (PDX) experiments found that HA selected the highly migratory breast cancer cells with CD44 expression accumulated in the tumor/stroma junction. In conclusion, HAS3 and HA were detected in the stroma breast tissues at a high level attenuates effects for induced breast cancer cell death, and inhibit the cancer cells invasion at the initial stage. However, the highly migratory cancer cells were resistant to the HA-mediated effects with unknown mechanisms.
Background: The present study aimed to explore the impact of sulforaphane on the growth of sSCC cells, and the activation of miR-199a-5p/Sirt1 and CD44ICD signaling pathways.Methods: Cell viability, count, apoptosis, and invasion assays were performed in the sSCC cell line (SCC-13) in which miR-199a-5p was over-expressed or under-expressed. The expression levels of miR-199a-5p, Sirt1 and CD44ICD mRNA were measured by quantitative real-time polymerase chain reaction (qRT-PCR).Results: Sulforaphane significantly inhibited the cell growth and invasion of SCC-13 cells, and dramatically induced cell apoptosis. Additionally, sulforaphane also greatly increased miR-199a-5p expression and suppressed Sirt1 and CD44ICD mRNA levels. Moreover, miR-199a-5p overexpression considerably down-regulated the expressions of Sirt1 and CD44ICD mRNA, and promoted the ability of sulforaphane to represses cell growth and invasion, and to induce cell apoptosis. However, miR-199a-5p underexpression has the opposite effects.Conclusions: Sulforaphane appears to inhibit sCC progression by impacting its growth and invasion ability, and regulates miR-199a-5p/Sirt1 and CD44ICD signaling pathways, and may be utilized to develop a curative approach for sSCC.
Purpose To identify Single Nucleotide Polymorphisms (SNPs) that can predict acute radiation dermatitis (RD) in breast cancer patients (BC), and the association between SNPs and RD severity. Methods We performed the search in seven databases and the gray literature, and a meta-analysis to assess SNPs in patients with RD and to evaluate the association between SNPs and severe RD. Results We included sixteen single-arm cohort studies with 4,742 BC. The most prevalent SNPs were the TGFβ1 rs1800469 (41%), and the GSTA1 rs3957356 (36%). Seven genotypes were associated with severe RD (PTTG1 rs3811999-CC; PTTG1 rs2961950-AA; MAD2L2 rs2294638-GG; MAT1A rs2282367-GG; GSTA1 rs3957356-CT; CD44 rs8193-CT; SH3GL1 rs243336-GC) and five SNPs were associated with lower RD (PTTG1 rs2961952-GG; CD44 rs8193-CC; PTTG1 rs3811999-CT; MAT1A rs2282367-GA; OGG1 rs2075747-AA). Conclusions The genotyping of SNPs more prevalent may be a strategy for predicting RD in BC, and some genotypes (GSTA1 rs3957356-CT; MAT1A rs2282367-GG) are associated with severe RD.
3D cell models derived from patient tumors are highly translational tools that can recapitulate the complex genetic and molecular compositions of solid cancers and accelerate identification of drug targets and drug testing. However, the complexity of performing assays with such models remains a hurdle for their wider adoption. In the present study, we describe methods for processing and multi-functional profiling of tumoroid samples to test compound effects using a novel flowchip system in combination with high content imaging and metabolite analysis. Tumoroids were formed from primary cells isolated from a patient-derived tumor explant, TU-BcX-4IC, that represents metaplastic breast cancer with a triple-negative breast cancer subtype. Assays were performed in a microfluidics-based device (Pu•MA System) that allows automated exchange of media and treatments of tumoroids in a tissue culture incubator environment. Multi-functional assay profiling was performed on tumoroids treated with anti-cancer drugs. High-content imaging was used to evaluate drug effects on cell viability and expression of E-cadherin and CD44. Lactate secretion was used to measure tumoroid metabolism as a function of time and drug concentration. Observed responses included loss of cell viability, decrease in E-cadherin expression, and increase of lactate production. Importantly, the tumoroids were sensitive to romidepsin and trametinib, while showed significantly reduced sensitivity to paclitaxel and cytarabine, consistent with the primary tumor response. These methods for multi-parametric profiling of drug effects in patient-derived tumoroids provide an in depth understanding of drug sensitivity of individual tumor types, with important implications for the future development of personalized medicine.
Drug-resistant cancer spheroids were fabricated by three-dimensional (3D) bioprinting for the quantitative evaluation of drug resistance of cancer cells, which is a very important issue in cancer treatment. Cancer spheroids have received great attention as a powerful in vitro model to replace animal experiments because of their ability to mimic the tumor microenvironment. In this work, the extrusion printing of gelatin-alginate hydrogel containing MCF-7 breast cancer stem cells successfully provided 3D growth of many single drug-resistant breast cancer spheroids in a cost-effective 3D-printed mini-well dish. The drug-resistant MCF-7 breast cancer spheroids were able to maintain their drug-resistant phenotype of CD44high/CD24low/ALDH1high in the gelatin-alginate media during 3D culture and exhibited higher expression levels of drug resistance markers, such as GRP78 chaperon and ABCG2 transporter, than bulk MCF-7 breast cancer spheroids. Furthermore, the effective concentration 50 (EC50) values for apoptotic and necrotic spheroid death could be directly determined from the 3D printed-gelatin-alginate gel matrix based on in situ 3D fluorescence imaging of cancer spheroids located out of the focal point and on the focal point. The EC50 values of anti-tumor agents (camptothecin and paclitaxel) for apoptotic and necrotic drug-resistant cancer spheroid death were higher than those for bulk cancer spheroid death, indicating a greater drug resistance. Statement of significance : This study proposed a novel 3D bioprinting-based drug screening model, to quantitatively evaluate the efficacy of anticancer drugs using drug-resistant MCF-7 breast cancer spheroids formed within a 3D-printed hydrogel. Quantitative determination of anticancer drug efficacy using EC50, which is extremely important in drug discovery, was achieved by 3D printing that enables concurrent growth of many single spheroids efficiently. This study verified whether drug-resistant cancer spheroids grown within 3D-printed gelatin-alginate hydrogel could maintain and present drug resistance. Also, the EC50 values of the apoptotic and necrotic cell deaths were directly acquired in 3D-embedded spheroids based on in situ fluorescence imaging. This platform provides a single-step straightforward strategy to cultivate and characterize drug-resistant spheroids to facilitate anticancer drug screening.
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CD44 is the primary cell surface receptor for the extracellular matrix glycosaminoglycan hyaluronan. Here we determined the relative avidities of unlabeled hyaluronan preparations for cell surface CD44 by their ability to block the binding of fluorescein-conjugated hyaluronan to a variety of cells. We show that hyaluronan binding at the cell surface is a complex interplay of multivalent binding events affected by the size of the multivalent hyaluronan ligand, the quantity and density of cell surface CD44, and the activation state of CD44 as determined by cell-specific factors and/or treatment with CD44-specific monoclonal antibody (mAb). Using low M r hyaluronan oligomers of defined sizes, we observed monovalent binding between 6 and 18 sugars. At ∼20 to ∼38 sugars, there was an increase in avidity (∼3×), suggesting that divalent binding was occurring. In the presence of the inducing mAb IRAWB14, monovalent binding avidity was similar to that of noninduced CD44, but beginning at ∼20 residues, there was a dramatic and progressive increase in avidity with increasing oligomer size (∼22 < 26 < 30 < 34 < 38 sugars). Kinetic studies of binding and dissociation of fluorescein-conjugated hyaluronan indicated that inducing mAb treatment had little effect on the binding kinetics, but dissociation from the cell surface was greatly delayed by inducing mAb.
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MicroRNA is responsible for the fine-tuning of fundamental cellular activities and human disease development. The altered availability of microRNAs, target mRNAs, and other types of endogenous RNAs competing for microRNA interactions reflects the dynamic and conditional property of microRNA-mediated gene regulation that remains under-investigated. Here we propose a new integrative method to study this dynamic process by considering both competing and cooperative mechanisms and identifying functional modules where different microRNAs co-regulate the same functional process. Specifically, a new pipeline was built based on a meta-Lasso regression model and the proof-of-concept study was performed using a large-scale genomic dataset from ~4,200 patients with 9 cancer types. In the analysis, 10,726 microRNA-mRNA interactions were identified to be associated with a specific stage and/or type of cancer, which demonstrated the dynamic and conditional miRNA regulation during cancer progression. On the other hands, we detected 4,134 regulatory modules that exhibit high fidelity of microRNA function through selective microRNA-mRNA binding and modulation. For example, miR-18a-3p, −320a, −193b-3p, and −92b-3p co-regulate the glycolysis/gluconeogenesis and focal adhesion in cancers of kidney, liver, lung, and uterus. Furthermore, several new insights into dynamic microRNA regulation in cancers have been discovered in this study.
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MicroRNAs (miRNAs) play important roles in cancer formation and progression by suppressing the production of key functional proteins at the post-transcriptional level in a sequence-specific manner. While differential expression of miRNAs is widely observed in cancers including prostate cancer (PCa), how these miRNAs are transcriptionally regulated is largely unknown. MiRNA-221 and miRNA-222 (miR-221/-222) are well-established oncogenes and overexpressed in breast, liver, pancreas, and lung cancer, but their expression and biological functions in PCa remain controversial. Both up and down regulation have been observed in patient samples. Specifically, studies have demonstrated miR-221/-222 function as oncogenes, and promote PCa cell proliferation and the development of castration-resistant prostate cancer (CRPC). However, the expression level of miR-221/-222 is downregulated in several miRNA expression profiling studies. In this study, we demonstrate miR-221/-222 are androgen receptor (AR)-repressed genes and reside in a long primary transcript (pri-miRNA). Derepression of miR-221/-222 after androgen deprivation therapy (ADT) may enhance PCa cell proliferation potential through promoting G1/S phase transition. This function is likely transient but important in the development of CRPC. Downregulation of miR-221/-222 subsequently occurs once AR activity is restored through AR overexpression in CRPC. Our findings shed light on the complexity of transcriptional regulation of miRNAs in PCa and suggest context-dependent targeting of oncogenic miRNAs.
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Purpose In the United States, 3.8 million women have a history of breast (BC) or ovarian cancer (OC). Up to 15% of cases are attributable to heritable mutations, which, if identified, provide critical knowledge for treatment and preventive care. It is unknown how many patients who are at high risk for these mutations have not been tested and how rates vary by risk criteria. Methods We used pooled cross-sectional data from three Cancer Control Modules (2005, 2010, 2015) of the National Health Interview Survey, a national in-person household interview survey. Eligible patients were adult females with a history of BC and/or OC meeting select 2017 National Comprehensive Cancer Network eligibility criteria on the basis of age of diagnosis and family history. Outcomes included the proportion of individuals reporting a history of discussing genetic testing with a health professional, being advised to undergo genetic testing, or undergoing genetic testing for BC or OC. Results Of 47,218 women, 2.7% had a BC history and 0.4% had an OC history. For BC, 35.6% met one or more select eligibility criteria; of those, 29.0% discussed, 20.2% were advised to undergo, and 15.3% underwent genetic testing. Testing rates for individual eligibility criteria ranged from 6.2% (relative with OC) to 18.2% (diagnosis ≤ 45 years of age). For OC, 15.1% discussed, 13.1% were advised to undergo, and 10.5% underwent testing. Using only four BC eligibility criteria and all patients with OC, an estimated 1.2 to 1.3 million individuals failed to receive testing. Conclusion Fewer than one in five individuals with a history of BC or OC meeting select National Cancer Comprehensive Network criteria have undergone genetic testing. Most have never discussed testing with a health care provider. Large national efforts are warranted to address this unmet need.
CD44 is a type I transmembrane protein and member of the cartilage link protein family. It is involved in cell-cell and cell-matrix interactions and signal transduction. Several CD44 ligands have been identified. CD44 is a major cell surface receptor for hyaluronan, a component of the extracellular matrix. It is implicated in diseases such as cancer and inflammation and therefore intensely studied. A characteristic feature of CD44 is the occurrence of many isoforms that are expressed in a cell-specific manner and differentially glycosylated. Although a number of CD44 isoforms have been characterized, the structural diversity of CD44 makes it often challenging to study (isoform-specific) CD44-ligand interactions at the molecular level of detail. The structural organization and ligand binding characteristics of CD44 are focal points of this review. On the basis of recent structural and mutagenesis studies, details of the CD44-hyaluronan interaction are beginning to be understood. Proteins 2000;39:103–111. © 2000 Wiley-Liss, Inc.
Osteopontin (OPN) is a secreted glycoprotein with mineral‐ and cell‐binding properties that can regulate cell activities through integrin receptors. Previously, we identified an intracellular form of osteopontin with a perimembranous distribution in migrating fetal fibroblasts (Zohar et al., J Cell Physiol 170:88–98, 1997). Since OPN and CD44 expression are increased in migrating cells, we analyzed the relationship of these proteins with immunofluorescence and confocal microscopy. A distinct co‐localization of perimembranous OPN and cell‐surface CD44 was observed in fetal fibroblasts, periodontal ligament cells, activated macrophages, and metastatic breast cancer cells. The co‐localization of OPN and CD44 was prominent at the leading edge of migrating fibroblasts, where OPN also co‐localized with the ezrin/radixin/moesin (ERM) protein ezrin, as well as in cell processes and at attachment sites of hyaluronan‐coated beads. The subcortical location of OPN in these cells was verified by cell‐surface biotinylation experiments in which biotinylated CD44 and non‐biotinylated OPN were isolated from complexes formed with hyaluronan‐coated beads and identified with immunoblotting. That perimembranous OPN represents secreted protein internalized by endocytosis or phagocytosis appeared to be unlikely since exogenous OPN that was added to cell cultures could not be detected inside the cells. A physical association with OPN, CD44, and ERM, but not with vinculin or α‐actin, was indicated by immunoadsorption and immunoblotting of cell proteins in complexes extracted from hyaluronan‐coated beads. The functional significance of OPN in this complex was demonstrated using OPN−/− and CD−/− mouse fibroblasts which displayed impaired migration and a reduced attachment to hyaluronan‐coated beads. These studies indicate that OPN exists as an integral component of a hyaluronan‐CD44‐ERM attachment complex that is involved in the migration of embryonic fibroblasts, activated macrophages, and metastatic cells. J. Cell. Physiol. 184:118–130, 2000. © 2000 Wiley‐Liss, Inc.
CD44 is a ubiquitous cell-surface glycoprotein that displays many variant isoforms (CD44v) generated by alternative splicing of exons 2v to 10v. The expression of variant isoforms is highly restricted and correlated with specific processes, such as leukocyte activation and malignant transformation. We have herein studied CD44v expression in acute myeloid leukemia (AML) and, for comparison, in normal myelopoiesis. Protein expression of total CD44 and of CD44-3v, -6v, and -9v isoforms has been measured using specific monoclonal antibodies and flow cytometry. The composition of variant exon transcripts has been analyzed by semi-quantitative reverse transcriptase-polymerase chain reaction followed by Southern hybridization with exon-specific probes. Our data show that (1) CD44-6v isoforms are expressed on 12.0% ± 2.5% of normal CD34+ cells; this expression is sharply upregulated through monopoiesis and, inversely, downregulated during granulopoiesis. Also, CD44-3v and CD44-9v isoforms are detected on 10% and 14% of normal monocytes, respectively. (2) Sixty-nine from a total of 95 AML patients display a variable proportion (range, 5% to 80%) of CD44-6v+ leukemic cells. (3) A shorter overall survival characterizes the group of AML patients displaying more than 20% of CD44-6v+ leukemic cells (8 months v 18 months, P < .02). These data suggest, for the first time, that the protein expression of CD44-6v containing isoforms may serve as a new prognostic factor in AML.
Background: Hormone receptor signaling is critical in the progression of breast cancers, although the role of the androgen receptor (AR) remains unclear, particularly for estrogen receptor (ER)-negative tumors. This study assessed AR protein expression as a prognostic marker for breast cancer mortality. Methods: This study included 4147 pre- and postmenopausal women with invasive breast cancer from the Nurses' Health Study (diagnosed 1976-2008) and Nurses' Health Study II (1989-2008) cohorts. AR protein expression was evaluated by immunohistochemistry and scored through pathologist review and as a digitally quantified continuous measure. Hazard ratios (HR) and 95% confidence intervals (CI) of breast cancer mortality were estimated from Cox proportional hazards models, adjusting for patient, tumor, and treatment covariates. Results: Over a median 16.5 years of follow-up, there were 806 deaths due to breast cancer. In the 7 years following diagnosis, AR expression was associated with a 27% reduction in breast cancer mortality overall (multivariable HR = 0.73, 95% CI = 0.58 to 0.91) a 47% reduction for ER+ cancers (HR = 0.53, 95% CI = 0.41 to 0.69), and a 62% increase for ER- cancers (HR = 1.62, 95% CI = 1.18 to 2.22) (P heterogeneity < .001). A log-linear association was observed between AR expression and breast cancer mortality among ER- cancers (HR = 1.14, 95% CI = 1.02 to 1.26 per each 10% increase in AR), although no log-linear association was observed among ER+ cancers. Conclusions: AR expression was associated with improved prognosis in ER+ tumors and worse prognosis in ER- tumors in the first 5-10 years postdiagnosis. These findings support the continued evaluation of AR-targeted therapies for AR+/ER- breast cancers.
Triple-negative breast cancer (TNBC) is an aggressive subtype that lacks effective targeted therapeutics strategy and has poor prognosis. Targeting androgen receptor (AR) in TNBC is thought to be a promising approach. We hypothesized that AR, functioning as a transcription factor, controls cell behavior via regulating the expression of microRNA molecules (miRNAs). The expression of 84 breast cancer-specific miRNAs in MDA-MB-231 cells, a highly invasive TNBC model system, was investigated using PCR arrays following treatment of cells with 5α-dihydrotestosterone (DHT). The expression of 33 miRNAs was changed by more than 2 folds including miR-328-3p, which was up-regulated by 13 folds. Transfection of cells with either miR-328-3p mimic or anti-sense molecules decreased cell motility. DHT-mediated effect on the expression and function of CD44, a target of miR-328-3p, was investigated. CD44 expression and cell adhesion to hyaluronic acid (HA) were down-regulated when cells were treated with DHT or transfection with a miR-328-3p mimic. On the other hand, the AR antagonist, bicalutamide, or transfection of cells with miR-328-3p anti-sense molecules had the opposite effect. Cells transfected with miR-328-3p anti-sense molecules reduced the negative effect of DHT on CD44 expression and cell adhesion to HA. In addition, DHT further reduced the expression of CD44 and cell adhesion to HA in cells transfected with miR-328-3p mimic. These results strongly suggest that miRNAs can mediate AR regulation of breast cancer cells and that AR controls the expression of CD44 via miRNA-dependent and independent mechanisms.
Aims and background We designed the present study to observe CD44s and CD44v6 expressions in colorectal cancer and evaluate their clinical value. Methods CD44s and CD44v6 expression in colorectal cancer tissues were examined by an immunohistochemical test. Survival analysis was performed with the Kaplan-Meier method, and the differences between the CD44-positive and -negative groups were evaluated with the logrank test. Results The positive rates of CD44s and CD44v6 were 66.7% and 63.2%, respectively. There were significant associations between CD44s positive expression and Dukes’ stage or tumor differentiation. There were significant associations between CD44v6 positive expression and tumor differentiation, Dukes’ stage and lymph node metastasis. There was a significant difference in the 5-year survival rates between CD44v6-positive and CD44v6-negative groups (52.78% and 80.95%, respectively), but not between CD44s-positive and CD44s-negative groups (55.26% and 78.95%, respectively). Multivariate analysis indicated that CD44v6 positive expression predicts a poor prognosis. Conclusions CD44s and CD44v6 play important roles in the infiltration and metastasis of colorectal cancer. CD44v6 positive expression can be a predictor for a poor prognosis.