[Show abstract][Hide abstract] ABSTRACT: About 50-70% of breast cancers are estrogen receptor α (ERα) positive and most of them are sensitive to endocrine therapy including tamoxifen. However, one third of these patients will eventually develop resistance and relapse. We found that the expression of miR-15a and miR-16 were significantly decreased in tamoxifen resistant ER positive breast cancer cell lines. Exogenous expression of miR-15a/16 mimics re-sensitized resistant cells to tamoxifen by inhibiting Cyclin E1 and B cell lymphoma-2 (Bcl-2) to induce cell growth arrest and apoptosis respectively. Further, we identified that a repressive member of E2F family, E2F7, was responsible for the suppression of miR-15a/16 cluster by competing with E2F1 for E2F binding site at the promoter of their host gene DLEU2. Moreover, high expression of E2F7 is correlated with high risk of relapse and poor prognosis in breast cancer patients receiving tamoxifen treatment. Together, our results suggest that overexpression of E2F7 represses miR-15a/16 and then increases Cyclin E1 and Bcl-2 that result in tamoxifen resistance. E2F7 may be a valuable prognostic marker and a therapeutic target of tamoxifen resistance in breast cancer.
[Show abstract][Hide abstract] ABSTRACT: Long noncoding RNA NBAT1 (neuroblastoma associated transcript 1) regulates cell proliferation and invasion by interacting with PRC2 (polycomb repressive complex 2) member EZH2 (enhancer of zeste 2). Decreased expression of NBAT1 is associated with poor clinical outcome in neuroblastomas. However, the roles of NBAT1 in other cancers remain unknown. Here, we report that NBAT1 is down-regulated in various types of cancer. Particularly, reduced NBAT1 in breast cancer is associated with tumor metastasis and poor patient prognosis. In vitro, ectopic NBAT1 inhibits migration and invasion of breast cancer cells. Mechanistic study shows that NBAT1 is associated with PRC2 member EZH2 and regulates global gene expression profile. Among them, DKK1 (dickkopf WNT signaling pathway inhibitor 1) is found to be regulated by NBAT1 in a PRC2 dependent manner, and is responsible for NBAT1's effects in inhibiting migration and invasion of breast cancer cells. Taken together, our study demonstrates that long noncoding RNA NBAT1 is a potential breast cancer prognostic marker, as well as a potential therapeutic target to inhibit breast cancer metastasis.
[Show abstract][Hide abstract] ABSTRACT: BRMS1L (breast cancer metastasis suppressor 1 like, BRMS1-like) is a component of Sin3A-histone deacetylase (HDAC) co-repressor complex that suppresses target gene transcription. Here we show that reduced BRMS1L in breast cancer tissues is associated with metastasis and poor patient survival. Functionally, BRMS1L inhibits breast cancer cells migration and invasion by inhibiting epithelial-mesenchymal transition. These effects are mediated by epigenetic silencing of FZD10, a receptor for Wnt signalling, through HDAC1 recruitment and histone H3K9 deacetylation at the promoter. Consequently, BRMS1L-induced FZD10 silencing inhibits aberrant activation of WNT3-FZD10-β-catenin signalling. Furthermore, BRMS1L is a target of miR-106b and miR-106b upregulation leads to BRMS1L reduction in breast cancer cells. RNA interference-mediated silencing of BRMS1L expression promotes metastasis of breast cancer xenografts in immunocompromised mice, whereas ectopic BRMS1L expression inhibits metastasis. Therefore, BRMS1L provides an epigenetic regulation of Wnt signalling in breast cancer cells and acts as a breast cancer metastasis suppressor.
Full-text · Article · Nov 2014 · Nature Communications
[Show abstract][Hide abstract] ABSTRACT: Phyllodes tumors (PTs) of breast, even histologically diagnosed as benign, can recur locally and have metastatic potential. Histological markers only have limited value in predicting the clinical behavior of PTs. It remains unknown what drives the malignant progression of PTs. We found that the expression of myofibroblast markers, α-SMA, FAP and SDF-1, is progressively increased in the malignant progression of PTs. Microarray showed that miR-21 was one of the most significantly upregulated microRNAs in malignant PTs compared with benign PTs. In addition, increased miR-21 expression was primarily localized to α-SMA-positive myofibroblasts. More importantly, α-SMA and miR-21 are independent predictors of recurrence and metastasis, with their predictive value of recurrence better than histological grading. Furthermore, miR-21 mimics promoted, while miR-21 antisense oligos inhibited, the expression of α-SMA, FAP and SDF-1, as well as the proliferation and invasion of primary stromal cells of PTs. The ability of miR-21 to induce myofibroblast differentiation was mediated by its regulation on Smad7 and PTEN, which regulate the migration and proliferation respectively. In breast PT xenografts, miR-21 accelerated tumor growth, induced myofibroblast differentiation and promoted metastasis. This study suggests an important role of myofibroblast differentiation in the malignant progression of PTs that is driven by increased miR-21.
[Show abstract][Hide abstract] ABSTRACT: Breast cancer stem-like cells (BCSC) have been implicated in tumor growth, metastasis, drug resistance and relapse but druggable targets in appropriate subsets of this cell population have yet to be identified. Here we identify a fundamental role for the prolyl isomerase Pin1 in driving BCSC expansion, invasiveness and tumorigenicity, defining it as a key target of miR-200c which is known to be a critical regluator in BSCS. Pin1 overexpression expanded the growth and tumorigenicity of BCSC and triggered epithelial-mesenchymal transition (EMT). Conversely, genetic or pharmaacological inhibition of Pin1 reduced the abundance and self-renewal activity of BCSC. Moreover, moderate overexpression of miR-200c-resistant Pin1 rescued the BCSC defect in miR-200c-expressing cells. Genetic deletion of Pin1 also decreased the abundance and repopulating capability of normal mouse mammary stem cells. In human cells freshly isolated from reduction mammoplasty tissues, Pin1 overexpression endowed BCSC traits to normal breast epithelial cells, expanding both luminal and basal/myoepithelial lineages in these cells. In contrast, Pin1 silencing in primary breast cancer cells isolated from clinical samples inhibited the expansion, self-renewal activity and tumorigenesis of BCSC in vitro and in vivo. Overall, our work demonstrated that Pin1 is a pivotal regulator acting downstream of miR-200c to drive BCSC and breast tumorigenicity, highlighting a new therapeutic target to eradicate BCSC.
[Show abstract][Hide abstract] ABSTRACT: The prognostic value of serum tumor markers (STMs) in nonmetastatic breast cancer patients with different molecular subtypes (luminal A, luminal B, and nonluminal) remains unknown. It is our institutional policy to assess the STMs in nonmetastatic patients. This retrospective single-center study is to investigate the association between STMs and clinical outcomes in nonmetastatic patients and the impact of molecular subtypes.
A total of 368 patients with available clinical outcomes, tumor node metastasis stages, and STMs levels were included. The serum level of preoperative STMs (carcinoembryonic antigen [CEA], cancer antigen 125 [CA-125], and cancer antigen 15-3 [CA 15-3]) was analyzed and compared among distinct molecular subtypes. Univariate and multivariate analyses were used to investigate the relationship among STMs concentrations and patient outcomes.
The median levels of CA 15-3 were 10.2, 8.1 and 7.1 U/mL in patients with luminal A, luminal B, and nonluminal diseases, respectively (P = 0.015). The levels of CEA and CA-125 were similar among the subtypes. Multivariate analysis showed that higher CA 15-3 was significantly associated with worse clinical outcomes exclusively in luminal A patients (P = 0.033 for metastasis-free survival and P = 0.030 for relapse-free survival). In contrast, higher CEA was a significant prognostic factor for worse clinical outcomes (P = 0.003 for metastasis-free survival and P = 0.015 for metastasis-free survival) in nonluminal groups.
The prognostic value of preoperative STMs may be different among molecular subtypes. Patients with luminal A diseases had higher levels of CA 15-3. Higher preoperative CA 15-3 was associated with worse clinical outcomes exclusively in patients with luminal A diseases.
No preview · Article · Mar 2014 · Journal of Surgical Research
[Show abstract][Hide abstract] ABSTRACT: TGF-β has paradoxical effects on cancer cell proliferation, as it suppresses proliferation of normal epithelial and low-invasive cancer cells, but enhances that of high-invasive cancer cells. However, how cancer cells acquire the ability to evade the tumor-suppressing effects of TGF-β, yet still take advantage of its tumor-promoting effects, remains elusive. Here, we identified miR-106b as a molecular switch to determine TGF-β effects on cell proliferation. TGF-β1 enhances the transcription of miR-106b via a promoter independent of its host gene MCM7 by activating c-jun. In high-invasive breast cancer cells, miR-106b is upregulated by TGF-β1 at a much higher level than that in normal or low-invasive cancer cells. Accumulation of miR-106b counterbalances TGF-β growth-inhibiting effects by eliminating activated retinoblastoma (RB) and results in enhanced proliferation. Furthermore, miR-106b mediates TGF-β effects on tumor growth and metastasis in breast cancer xenografts. In addition, miR-106b expression is elevated in higher stage tumors and correlated with tumor progression in breast cancer patients. These findings suggest that high level of miR-106b induced by TGF-β determines the tumor-promoting effects of TGF-β in breast cancer.Oncogene advance online publication, 2 December 2013; doi:10.1038/onc.2013.525.
[Show abstract][Hide abstract] ABSTRACT: Identification of new nasopharyngeal carcinoma (NPC) biomarkers is of great clinical value for the diagnosis and treatment of NPC. HOTAIR, a cancer-related long noncoding RNA, was tested and its prognostic value for NPC was evaluated. Determined by In situ hybridization (ISH), 91 of 160 (56.87%) paraffin-embedded NPC biopsies showed high expression levels of HOTAIR (Staing Index, SI score ≥ 6). HOTAIR was up-regulated in tumors with a larger tumor (p = 0.021), more advanced clinical staging (P = 0.012) and increased lymph node tumor burden (P = 0.005). Quantified by real-time PCR, HOTAIR expression levels in fresh tissue and paraffin-embedded samples were 5.2˜48.4-fold higher compared with non-cancer tissue samples. Moreover, HOTAIR expression levels increased with clinical stage progression, which was consistent with ISH findings in the paraffin-embedded tissue. Most importantly, NPC patients with higher HOTAIR levels had poor prognosis for overall survival by univariate and multivariate analysis. In addition, HOTAIR mediated the migration, invasion and proliferation of NPC cells in vitro. HOTAIR is a potential biomarker for the prognosis of NPC, and dysregulation of HOTAIR may play an important role in NPC progression.
[Show abstract][Hide abstract] ABSTRACT: Malignant tissue contains a rare population of multi-potent cells known as cancer stem-like cells (CSCs). Autophagy is an important mechanism in cancer cell survival and tumor growth; it can both suppress malignant transformation and promote the growth of established cancers. However, the molecular mechanisms underlying the tumor-promoting and tumor-suppressing functions of autophagy in CSCs are not understood. Our work demonstrates that a prosurvival autophagic pathway is critical for breast CSC maintenance. Notably, we provide new evidence for the existence of two separate, context-dependent, autophagic programs that are regulated in opposite ways by BECN1.
[Show abstract][Hide abstract] ABSTRACT: Malignant breast tissue contains a rare population of multi-potent cells with the capacity to self-renew; these cells are known as cancer stem-like cells (CSCs) or tumor-initiating cells. Primitive mammary CSCs/progenitor cells can be propagated in culture as floating spherical colonies termed 'mammospheres'. We show here that the expression of the autophagy protein Beclin 1 is higher in mammospheres established from human breast cancers or breast cancer cell lines (MCF-7 and BT474) than in the parental adherent cells. As a result, autophagic flux is more robust in mammospheres. We observed that basal and starvation-induced autophagy flux is also higher in aldehyde dehydrogenase 1-positive (ALDH1(+)) population derived from mammospheres than in the bulk population. Beclin 1 is critical for CSC maintenance and tumor development in nude mice, whereas its expression limits the development of tumors not enriched with breast CSCs/progenitor cells. We found that decreased survival in autophagy-deficient cells (MCF-7 Atg7 knockdown cells) during detachment does not contribute to an ultimate deficiency in mammosphere formation. This study demonstrates that a prosurvival autophagic pathway is critical for CSC maintenance, and that Beclin 1 plays a dual role in tumor development.Oncogene advance online publication, 25 June 2012; doi:10.1038/onc.2012.252.
[Show abstract][Hide abstract] ABSTRACT: Malignant breast tissue contains a rare population of multi-potent cells with the capacity to self-renew; these cells are known as
cancer stem-like cells (CSCs) or tumor-initiating cells. Primitive mammary CSCs/progenitor cells can be propagated in culture as
floating spherical colonies termed ‘mammospheres’. We show here that the expression of the autophagy protein Beclin 1 is higher
in mammospheres established from human breast cancers or breast cancer cell lines (MCF-7 and BT474) than in the parental
adherent cells. As a result, autophagic flux is more robust in mammospheres. We observed that basal and starvation-induced
autophagy flux is also higher in aldehyde dehydrogenase 1-positive (ALDH1þ) population derived from mammospheres than in
the bulk population. Beclin 1 is critical for CSC maintenance and tumor development in nude mice, whereas its expression limits the
development of tumors not enriched with breast CSCs/progenitor cells. We found that decreased survival in autophagy-deficient
cells (MCF-7 Atg7 knockdown cells) during detachment does not contribute to an ultimate deficiency in mammosphere formation.
This study demonstrates that a prosurvival autophagic pathway is critical for CSC maintenance, and that Beclin 1 plays a dual role in
[Show abstract][Hide abstract] ABSTRACT: Neoadjuvant chemotherapy (NAC) is increasingly being used in breast cancer treatment. Research has revealed an elevated expression of miR-221 in adriamycinresistant MCF-7/ADR cells. This study aimed to explore the potential role of miR-221 as a biomarker for chemosensitivity in breast cancer patients who previously received NAC.
The expression levels of circulating miR-221 in the plasma of 93 breast cancer patients who previously received NAC and in 32 healthy individuals were assessed. The correlations between miR-221 and clinicopathological features and chemosensitivity were also analysed.
The expression level of miR-221 was significantly associated with hormone receptor (HR) status (p = 0.008). Patients with higher plasma miR-221 levels tended to be HR-negative. Patients with different miR-221 levels had significant differences in the overall response rate (p = 0.044) but not in the pathologic complete response rate (p = 0.477).
Our results indicate that plasma miR-221 may be a predictive biomarker for sensitivity to NAC in breast cancer patients.
[Show abstract][Hide abstract] ABSTRACT: Tumor-initiating cells are resistant to chemotherapy, but how microRNAs play a role in regulating drug resistance of breast tumor-initiating cells (BT-IC) needs to be clarified.
Lentivirus-mediated miR-128 transduction was done in BT-ICs, enriched by mammosphere cultures or CD44(+)CD24(-) fluorescence-activated cell sorting. Apoptosis and DNA damage were determined upon treatment with doxorubicin. Expression of miR-128 in breast cancer tissues was examined by in situ hybridization and correlated with breast tumor response to neoadjuvant chemotherapy and patient survival.
MiR-128 was significantly reduced in chemoresistant BT-ICs enriched from breast cancer cell lines and primary breast tumors (P < 0.01), accompanied by an overexpression of Bmi-1 and ABCC5, which were identified as targets of miR-128. Ectopic expression of miR-128 reduced the protein levels of Bmi-1 and ABCC5 in BT-ICs, along with decreased cell viability (P < 0.001) and increased apoptosis (P < 0.001) and DNA damage (P < 0.001) in the presence of doxorubicin. Reduced miR-128 expression in breast tumor tissues was associated with chemotherapeutic resistance (P < 0.001) and poor survival of breast cancer patients (P < 0.05; n = 57).
Reduction in miR-128 leading to Bmi-1 and ABCC5 overexpression is a stem cell-like feature of BT-ICs, which contributes to chemotherapeutic resistance in breast cancers. Ectopic expression of miR-128 sensitizes BT-ICs to the proapoptotic and DNA-damaging effects of doxorubicin, indicating therapeutic potential.
Preview · Article · Sep 2011 · Clinical Cancer Research
[Show abstract][Hide abstract] ABSTRACT: Tumor-associated macrophages (TAMs) can influence cancer progression and metastasis, but the mechanism remains unclear. Here, we show that breast TAMs abundantly produce CCL18, and its expression in blood or cancer stroma is associated with metastasis and reduced patient survival. CCL18 released by breast TAMs promotes the invasiveness of cancer cells by triggering integrin clustering and enhancing their adherence to extracellular matrix. Furthermore, we identify PITPNM3 as a functional receptor for CCL18 that mediates CCL18 effect and activates intracellular calcium signaling. CCL18 promotes the invasion and metastasis of breast cancer xenografts, whereas suppressing PITPNM3 abrogates these effects. These findings indicate that CCL18 derived from TAMs plays a critical role in promoting breast cancer metastasis via its receptor, PITPNM3.
[Show abstract][Hide abstract] ABSTRACT: Trastuzumab resistance emerges to be a major issue in anti-human epidermal growth factor receptor 2 (HER2) therapy for breast
cancers. Here, we demonstrated that miR-21 expression was up-regulated and its function was elevated in HER2+ BT474, SKBR3, and MDA-MB-453 breast cancer cells that are induced to acquire trastuzumab resistance by long-term exposure
to the antibody, whereas protein expression of the PTEN gene, a miR-21 target, was reduced. Blocking the action of miR-21 with antisense oligonucleotides re-sensitized the resistant cells to the therapeutic activities of trastuzumab by inducing
growth arrest, proliferation inhibition, and G1-S cell cycle checking in the presence of the antibody. Ectopic expression of miR-21 in HER2+ breast cancer cells confers resistance to trastuzumab. Rescuing PTEN expression with a p3XFLAG-PTEN-mut construct with deleted miR-21 targeting sequence at its 3′ UTR restored the growth inhibition of trastuzumab in the resistant cells by inducing PTEN activation
and AKT inhibition. In vivo, administering miR-21 antisense oligonucleotides restored trastuzumab sensitivity in the resistant breast cancer xenografts by inducing PTEN expression,
whereas injection of miR-21 mimics conferred trastuzumab resistant in the sensitive breast tumors via PTEN silence. Up-regulatin of miR-21 in tumor biopsies obtained from patients receiving pre-operative trastuzumab therapy was associated with poor trastuzumab
response. Therefore, miR-21 overexpression contributes to trastuzumab resistance in HER2+ breast cancers and antagonizing miR-21 demonstrates therapeutic potential by sensitizing the malignancy to anti-HER2 treatment.
[Show abstract][Hide abstract] ABSTRACT: Evidence is lacking whether the number of breast tumor-initiating cells (BT-ICs) directly correlates with the sensitivity of breast tumors to chemotherapy. Here, we evaluated the association between proportion of BT-ICs and chemoresistance of the tumors.
Immunohistochemical staining(IHC) was used to examine the expression of aldehyde dehydrogenase 1 (ALDH1) and proliferating cell nuclear antigen, and TUNEL was used to detect the apoptosis index. The significance of various variables in patient survival was analyzed using a Cox proportional hazards model. The percentage of BT-ICs in breast cancer cell lines and primary breast tumors was determined by ALDH1 enzymatic assay, CD44(+)/CD24(-) phenotype and mammosphere formation assay.
ALDH1 expression determined by IHC in primary breast cancers was associated with poor clinical response to neoadjuvant chemotherapy and reduced survival in breast cancer patients. Breast tumors that contained higher proportion of BT-ICs with CD44(+)/CD24(-) phenotype, ALDH1 enzymatic activity and sphere forming capacity were more resistant to neoadjuvant chemotherapy. Chemoresistant cell lines AdrR/MCF-7 and SK-3rd, had increased number of cells with sphere forming capacity, CD44(+)/CD24(-) phenotype and side-population. Regardless the proportion of T-ICs, FACS-sorted CD44(+)/CD24(-) cells that derived from primary tumors or breast cancer lines were about 10-60 fold more resistant to chemotherapy relative to the non- CD44(+)/CD24(-) cells and their parental cells. Furthermore, our data demonstrated that MDR1 (multidrug resistance 1) and ABCG2 (ATP-binding cassette sub-family G member 2) were upregulated in CD44(+)/CD24(-) cells. Treatment with lapatinib or salinomycin reduced the proportion of BT-ICs by nearly 50 fold, and thus enhanced the sensitivity of breast cancer cells to chemotherapy by around 30 fold.
These data suggest that the proportion of BT-ICs is associated with chemotherapeutic resistance of breast cancer. It highlights the importance of targeting T-ICs, rather than eliminating the bulk of rapidly dividing and terminally differentiated cells, in novel anti-cancer strategies.