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The standard targeted therapy for HER2-overexpressing breast cancer is the HER2 monoclonal antibody, trastuzumab. Although effective, many patients eventually develop trastuzumab resistance. The dual EGFR/HER2 small molecule tyrosine kinase inhibitor lapatinib is approved for use in trastuzumab-refractory metastatic HER2-positive breast cancer. How...
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... human epidermal growth factor receptor (HER) tyrosine kinase family is comprised of four members: HER1 (human epidermal growth factor receptor, EGFR), HER2, HER3, and HER4. Upon ligand binding, receptor dimerization activates multiple signaling pathways including the mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI3K) pathways [1–3]. HER2 is overexpressed in about 20% of metastatic breast cancers and is associated with a poor prognosis [4,5]. Trastuzumab (Herceptin), a monoclonal antibody targeted against the extracellular domain of HER2, is a highly effective treatment for patients with HER2-overexpressing breast cancers. However, as is the case with many targeted therapies, a majority of patients will eventually develop resistance to trastuzumab, resulting in disease progression. The dual EGFR/HER2 tyrosine kinase inhibitor lapatinib (Figure 1) (Tykerb) is approved for use in trastuzumab-refractory tumors. Lapatinib binds to the ATP-binding pocket of HER2, thereby preventing receptor phosphorylation and subsequent activation of downstream pathways. However, response to single agent lapatinib in trastuzumab-resistant cancers is less than 25% [6,7]. Understanding the molecular mechanisms that lead to lapatinib resistance may ultimately improve the clinical benefit that patients received from lapatinib-based treatment. Previous studies have focused primarily on the role of PI3K/mTOR signaling in lapatinib resistance [8–10]. However, inhibition of MEK appears to also play a critical role in mediating lapatinib cytotoxicity. Tanizaki et al. [11] showed that lapatinib-mediated inhibition of MEK is critical for induction of apoptosis. Lapatinib treatment of HER2- overexpressing cells inhibited MEK/ERK signaling, leading to up-regulation of the pro- apoptotic protein Bcl-2-interacting mediator of cell death (BIM). Further, transfection of oncogenic Ras into HER2-overexpressing, lapatinib-sensitive SKBR3 and BT474 cells has been shown to activate MEK/ERK signaling and abrogate response to lapatinib [12]. The Forkhead box transcription factor M1 (FOXM1) is downstream of the MEK signaling pathway and its up-regulation is associated with HER2 overexpression [13–15]. Upon MEK/ ERK phosphorylation, FOXM1 is activated and translocates to the nucleus to stimulate proliferation and cell survival by modulating expression of cell cycle and apoptosis regulators including the cyclin-dependent kinase inhibitor p27 kip1 and the anti-apoptotic protein survivin [16]. In the current study, we examine the role of MEK/ERK signaling in HER2-positive trastuzumab-resistant cells that exhibit reduced response to lapatinib. We demonstrate that an inability to block ERK phosphorylation is associated with reduced response to lapatinib. Pharmacologic inhibition or knockdown of MEK in combination with lapatinib induced cell cycle arrest and/or apoptosis in association with reduced expression of nuclear FOXM1 in resistant cells. Further, knockdown or pharmacologic inhibition of FOXM1 increased response of resistant cells to lapatinib, whereas transfection of FOXM1 into sensitive cells resulted in resistance. Finally, co-treatment of xenografts of HER2-positive, trastuzumab- resistant breast cancer cells with lapatinib and the MEK inhibitor selumetinib suppressed tumor growth, reduced Ki-67 staining, suppressed ERK phosphorylation, and reduced expression of FOXM1 in comparison to xenografts treated with single agents or vehicle control. Thus, MEK inhibition should be studied further as a strategy for increasing response to lapatinib in HER2-positive breast cancers that have progressed on trastuzumab. Lapatinib was purchased from Santa Cruz Biotechnology (Santa Cruz, CA). Selumetinib (Figure 1) was purchased from LC Laboratories (Woburn, MA). PD0325901 was purchased from Cayman Chemical (Ann Arbor, MI). Thiostrepton was purchased from Sigma-Aldrich (St. Louis, MO). All drugs were dissolved in DMSO at a stock concentration of 10 mM except thiostrepton, which was dissolved at a stock concentration of 50 mM. Lapatinib for vivo studies was purchased from the Winship Cancer Institute pharmacy and dissolved in a buffer containing 1% Tween-80 and 5% hydroxypropyl methylcellulose just before ...
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... human epidermal growth factor receptor (HER) tyrosine kinase family is comprised of four members: HER1 (human epidermal growth factor receptor, EGFR), HER2, HER3, and HER4. Upon ligand binding, receptor dimerization activates multiple signaling pathways including the mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI3K) pathways [1–3]. HER2 is overexpressed in about 20% of metastatic breast cancers and is associated with a poor prognosis [4,5]. Trastuzumab (Herceptin), a monoclonal antibody targeted against the extracellular domain of HER2, is a highly effective treatment for patients with HER2-overexpressing breast cancers. However, as is the case with many targeted therapies, a majority of patients will eventually develop resistance to trastuzumab, resulting in disease progression. The dual EGFR/HER2 tyrosine kinase inhibitor lapatinib (Figure 1) (Tykerb) is approved for use in trastuzumab-refractory tumors. Lapatinib binds to the ATP-binding pocket of HER2, thereby preventing receptor phosphorylation and subsequent activation of downstream pathways. However, response to single agent lapatinib in trastuzumab-resistant cancers is less than 25% [6,7]. Understanding the molecular mechanisms that lead to lapatinib resistance may ultimately improve the clinical benefit that patients received from lapatinib-based treatment. Previous studies have focused primarily on the role of PI3K/mTOR signaling in lapatinib resistance [8–10]. However, inhibition of MEK appears to also play a critical role in mediating lapatinib cytotoxicity. Tanizaki et al. [11] showed that lapatinib-mediated inhibition of MEK is critical for induction of apoptosis. Lapatinib treatment of HER2- overexpressing cells inhibited MEK/ERK signaling, leading to up-regulation of the pro- apoptotic protein Bcl-2-interacting mediator of cell death (BIM). Further, transfection of oncogenic Ras into HER2-overexpressing, lapatinib-sensitive SKBR3 and BT474 cells has been shown to activate MEK/ERK signaling and abrogate response to lapatinib [12]. The Forkhead box transcription factor M1 (FOXM1) is downstream of the MEK signaling pathway and its up-regulation is associated with HER2 overexpression [13–15]. Upon MEK/ ERK phosphorylation, FOXM1 is activated and translocates to the nucleus to stimulate proliferation and cell survival by modulating expression of cell cycle and apoptosis regulators including the cyclin-dependent kinase inhibitor p27 kip1 and the anti-apoptotic protein survivin [16]. In the current study, we examine the role of MEK/ERK signaling in HER2-positive trastuzumab-resistant cells that exhibit reduced response to lapatinib. We demonstrate that an inability to block ERK phosphorylation is associated with reduced response to lapatinib. Pharmacologic inhibition or knockdown of MEK in combination with lapatinib induced cell cycle arrest and/or apoptosis in association with reduced expression of nuclear FOXM1 in resistant cells. Further, knockdown or pharmacologic inhibition of FOXM1 increased response of resistant cells to lapatinib, whereas transfection of FOXM1 into sensitive cells resulted in resistance. Finally, co-treatment of xenografts of HER2-positive, trastuzumab- resistant breast cancer cells with lapatinib and the MEK inhibitor selumetinib suppressed tumor growth, reduced Ki-67 staining, suppressed ERK phosphorylation, and reduced expression of FOXM1 in comparison to xenografts treated with single agents or vehicle control. Thus, MEK inhibition should be studied further as a strategy for increasing response to lapatinib in HER2-positive breast cancers that have progressed on trastuzumab. Lapatinib was purchased from Santa Cruz Biotechnology (Santa Cruz, CA). Selumetinib (Figure 1) was purchased from LC Laboratories (Woburn, MA). PD0325901 was purchased from Cayman Chemical (Ann Arbor, MI). Thiostrepton was purchased from Sigma-Aldrich (St. Louis, MO). All drugs were dissolved in DMSO at a stock concentration of 10 mM except thiostrepton, which was dissolved at a stock concentration of 50 mM. Lapatinib for vivo studies was purchased from the Winship Cancer Institute pharmacy and dissolved in a buffer containing 1% Tween-80 and 5% hydroxypropyl methylcellulose just before ...
Citations
... The reduction in growth rate as an apparent additional feature of MEK inhibition in nonsmall cell lung cancer tumour initiating cells was already mentioned in (Lundholm et al. 2014), but there we did not have any tool to measure it quantitatively. Another example of reduced colony size was reported after combined MEK and EGFR/HER2 inhibition in breast cancer cells (Gayle et al. 2013). The quantitative description was possible to perform when using the software presented here. ...
The clonogenic cell survival assay is a basic method to study the cytotoxic effect of radiation and chemical toxins. In large experimental setups, counting of colonies by eye is tiresome and prone to bias. Moreover, it is often interesting to quantify the size of individual colonies. Such analyses are largely facilitated by computerised image analysis systems. Although a number of such systems exist, they all focus on enumerating colonies and not on analysing the colony size. We have developed a new software package for both counting colonies and plotting their size distributions. The software called count and Plot HIstograms of Colony Size (countPHICS) consists of two parts: (1) a macro written for ImageJ which analyses computerised images of cell culture dishes or 6-well plates, counts colonies, estimates their size and saves the results in a text file; (2) a program written with QT Creator which reads the text file, plots histograms of colony size distribution and fits the best function. The full program is freely available at: http://www.fuw.edu.pl/~bbrzozow/FizMed/countPHICS.html. In conclusion, our new publically available software will facilitate colony counting and provide additional information on the colony growth rate, which is relevant especially for radiosensitisation studies.
... Upon PEPD G278D treatment (25 nM, 48 hours), all the cell lines except MCF-7 showed profound loss of HER2 and EGFR (both expression and phosphorylation), loss of phosphorylation (inactivation) of all key downstream signaling partners analyzed, including SRC, AKT, and ERK (extracellular signal-regulated kinase), and loss of phosphorylation of RTKs which heterodimerize with HER2, including IGF1R (insulin-like growth factor 1 receptor) and MET (c-MET) (Fig. 1C). SRC, AKT, ERK, IGF1R, and MET all play important roles in HER2-BC resistance to current HER2 inhibitors (10,11,30,31). PEPD G278D -induced changes in SRC, AKT, ERK, IGF1R, and MET apparently resulted from the inhibition of HER2 and EGFR because none of the changes occurred in MCF-7 cells (Fig. 1C). ...
Resistance to current human epidermal growth factor receptor 2 (HER2) inhibitors, such as trastuzumab (Ttzm), is a major unresolved clinical problem in HER2-positive breast cancer (HER2-BC). Because HER2 remains overexpressed in drug-resistant HER2-BC cells, we investigated whether PEPD G278D can overcome the resistance. PEPD G278D is a recombinant enzymatically inactive mutant of human peptidase D, which strongly inhibits HER2 in cancer cells by binding to its extracellular domain. Here, we show that PEPD G278D is highly active in preclinical models of HER2-BC resistant to Ttzm and other HER2 inhibitors and also enhances the therapeutic efficacy of paclitaxel. The therapeutic activity is underscored by its ability to bind to HER2 and free it from protection by mucin 4, disrupt its interplay with other receptor tyrosine kinases, and subsequently direct HER2 for degradation. PEPD G278D also down-regulates epidermal growth factor receptor, which contributes to drug resistance in HER2-BC. In contrast, Ttzm, whose therapeutic activity also depends on its binding to the extracellular domain of HER2, cannot perform any of these functions of PEPD G278D . PEPD G278D inhibits HER2-BC cells and tumors that carry clinically relevant molecular changes that confer resistance to Ttzm. Our results show that HER2 remains a critical target in drug-resistant HER2-BC and that PEPD G278D is a promising agent for overcoming drug resistance in this disease.
... FoxM1 was also shown to be transactivated by HSF1, which promoted the survival of glioma cells under heat shock stress [52]. An increasing number of studies have reported that FoxM1 mediates drug resistance in many types of cancers, including gastric cancer [53], breast cancer [54,55] and glioblastoma [56], by regulating the expression of downstream targets. Together with these Fig. 4 Gli1 regulates CRC cell proliferation depending on FoxM1. ...
Background
Recent evidence suggests that the aberrant activation of Hedgehog (Hh) signaling by Gli transcription factors is characteristic of a variety of aggressive human carcinomas, including colorectal cancer (CRC). Forkhead box M1 (FoxM1) controls the expression of a number of cell cycle regulatory proteins, and FoxM1 expression is elevated in a broad range of human malignancies, which suggests that it plays a crucial role in tumorigenesis. However, the mechanisms underlying FoxM1 expression are not fully understood. Here, we aim to further investigate the molecular mechanism by which Gli1 regulates FoxM1 in CRC. Methods
Western blotting and immunohistochemistry (IHC) were used to evaluate FoxM1 and Gli1 protein expression, respectively, in CRC tissues and matched adjacent normal mucosa. BrdU (5-bromo-2′-deoxyuridine) and clone formation assays were used to clarify the influence of FoxM1 on CRC cell growth and proliferation. Chromatin immunoprecipitation (ChIP) and luciferase experiments were performed to explore the potential mechanisms by which Gli1 regulates FoxM1. Additionally, the protein and mRNA expression levels of Gli1 and FoxM1 in six CRC cell lines were measured using Western blotting and real-time PCR. Finally, the effect of Hh signaling on the expression of FoxM1 was studied in cell biology experiments, and the effects of Hh signaling activation and FoxM1 inhibition on the distribution of CRC cells among cell cycle phases was assessed by flow cytometry. ResultsGli1 and FoxM1 were abnormally elevated in human CRC tissues compared with matched adjacent normal mucosa samples, and FoxM1 is a downstream target gene of the transcription factor Gli1 in CRC and promoted CRC cell growth and proliferation. Moreover, the aberrant activation of Hh signaling promoted CRC cell proliferation by directly binding to the promoter of FoxM1 and transactivating the activity of FoxM1 in CRC cells. Conclusion
The dysregulation of the Hh-Gli1-FoxM1 axis is essential for the proliferation and growth of human CRC cells and offers a potent target for therapeutic intervention in CRC.
... For example, both HER2 and FOXM1 are involved in the signal pathways of Ras-MAPK and PI3K-Akt, and they are also closely related to tumor angiogenesis, invasion and metastasis. Recently, some studies have showed FOXM1 was a key target of trastuzumab, lapatinib and gefitinib [30][31][32]. ...
Background:
The human epidermal growth factor receptor 2 (HER2) and transcription factor forkhead box protein M1 (FOXM1) are proto-oncogenes and have expressed in various kinds of human solid malignancies. However, the clinical significance of HER2 and FOXM1 in colorectal cancer (CRC) remains controversial, and there is no related report of the connection between HER2 and FOXM1 in colorectal cancer. This study aims to investigate the clinical values based on the connection of HER2 with FOXM1 in colorectal cancer.
Material/methods:
We retrospectively investigated HER2 and FOXM1 expressions of 130 paraffin embedded CRC and their adjacent paraneoplastic tissues through immunohistochemical assay. Western blot and RT-PCR assays were applied to measure the relative expressions of HER2 and FOXM1 in mRNA and the protein levels of 30 fresh CRC and the adjacent paraneoplastic tissues.
Results:
HER2 and FOXM1 expressions were significantly higher in colorectal cancer than those in paraneoplastic tissues (P<0.001). Similarly, the relative expression levels of HER2 and FOXM1 in mRNA and protein were also significantly higher in CRC tissues than those in paraneoplastic tissues (P<0.05). The HER2 expression was closely correlated with tumor size, degree of differentiation, presence of vascular invasion, lymph node metastasis, distant metastases, advanced TNM stage, and prognosis (P<0.05). The FOXM1 expression was related to tumor invasion, vascular invasion, lymph node metastasis, distant metastases, TNM stage, and prognosis (P<0.05). Besides, FOXM1 was an independent prognostic factor in CRC. There was a significant correlation between FOXM1 and HER2 expressions in colorectal cancer (r=0.335; P<0.01).
Conclusions:
The overexpressions of HER2 and FOXM1 protein in colorectal cancer correlate with their clinicopathological characteristics and prognosis. HER2 and FOXM1 are important diagnostic markers for colorectal cancer. Furthermore, FOXM1 may be a potential target for therapy especially in HER2-targeted therapy-resistant cancers.
... The p38α pharmacological inhibitior has also been shown to be able to combine with cisplatin to decrease colony formation and viability of cancer cells and strongly increase Bax-dependent apoptotic cell death by activating FOXO3 in colorectal cancer (CRC) cells [32]. Furthermore, overexpression of FOXM1 or downregulation of FOXO3 also reduces the sensitivity of EGFR/HER2 overexpressing breast cancer cells to tyrosine-kinase receptor inhibitors, such as gefitinib and lapatinib, while inhibition of FOXM1 or re-expression of FOXO3 restores sensitivity to these inhibitors in resistant breast cancer cells [33,34]. ...
... Activated FOXO3 antagonises FOXM1 and thus competes for binding to its effectors, for example, vascular endothelial growth factor (VEGF), a key factor implicated with metastasis and angiogenesis in malignancies [17]. In addition, overexpression of FOXM1 reduces the sensitivity of HER2-positive breast cancer cells to lapatinib, while inhibition of FOXM1 rescues resistance to lapatinib resistance [33,34]. Similarly, gefitinib attenuates EGFR signal transduction and is correlated with FOXM1 suppression [36]. ...
The FOXO3 and FOXM1 forkhead box transcription factors, functioning downstream of the essential PI3K-Akt, Ras-ERK and JNK/p38MAPK signalling cascades, are crucial for cell proliferation, differentiation, cell survival, senescence, DNA damage repair and cell cycle control. The development of resistance to both conventional and newly emerged molecularly targeted therapies is a major challenge confronting current cancer treatment in the clinic. Intriguingly, the mechanisms of resistance to 'classical' cytotoxic chemotherapeutics and to molecularly targeted therapies are invariably linked to deregulated signalling through the FOXO3 and FOXM1 transcription factors. This is owing to the involvement of FOXO3 and FOXM1 in the regulation of genes linked to crucial drug action-related cellular processes, including stem cell renewal, DNA repair, cell survival, drug efflux, and deregulated mitosis. A better understanding of the mechanisms regulating the FOXO3-FOXM1 axis, as well as their downstream transcriptional targets and functions, may render these proteins reliable and early diagnostic/prognostic factors as well as crucial therapeutic targets for cancer treatment and importantly, for overcoming chemotherapeutic drug resistance.
... Many clinical and preclinical studies are currently investigating the importance of targeting PI3K in HER2-positive breast cancer, however the MEK/MAPK pathway has also been recently established as a potential target for therapy in oncology patients [12]. Interestingly studies by Cheng et al have found that PIK3CA mutated HER2-positive breast cancer tumours escape PIK3CA dependence by activating MAPK/MEK signalling pathways [13]. ...
... [10,14,24]. However little attention has been paid to targeting the MEK/MAPK pathway in HER2-positive breast cancer despite the fact that it is also frequently activated in this disease and has been recently established as a potential target for therapy [12]. In fact a recent article by Cheng et al (2016) found that PIK3CA 75 Table 1). ...
Purpose
The MEK/MAPK pathway is commonly activated in HER2-positive breast cancer, but little investigation of targeting this pathway has been undertaken. Here we present the results of an in vitro preclinical evaluation of refametinib, an allosteric MEK1/2 inhibitor, in HER2-positive breast cancer cell lines including models of acquired resistance to trastuzumab or lapatinib.
Methods
A panel of HER2-positive breast cancer cells were profiled for mutational status and also for anti-proliferative response to refametinib alone and in combination with the PI3K inhibitor (PI3Ki) copanlisib and the HER2-targeted therapies trastuzumab and lapatinib. Reverse phase protein array (RPPA) was used to determine the effect of refametinib alone and in combination with PI3Ki and HER2-inhibitors on expression and phosphorylation of proteins in the PI3K/AKT and MEK/MAPK pathways. We validated our proteomic in vitro findings by utilising RPPA analysis of patients who received either trastuzumab, lapatinib or the combination of both drugs in the NCT00524303/LPT109096 clinical trial.
Results
Refametinib has anti-proliferative effects when used alone in 2/3 parental HER2-positive breast cancer cell lines (HCC1954, BT474), along with 3 models of these 2 cell lines with acquired trastuzumab or lapatinib resistance (6 cell lines tested). Refametinib treatment led to complete inhibition of MAPK signalling. In HCC1954, the most refametinib-sensitive cell line (IC50= 397 nM), lapatinib treatment inhibits phosphorylation of MEK and MAPK but activates AKT phosphorylation, in contrast to the other 2 parental cell lines tested (BT474-P, SKBR3-P), suggesting that HER2 may directly activate MEK/MAPK and not PI3K/AKT in HCC1954 cells but not in the other 2 cell lines, perhaps explaining the refametinib-sensitivity of this cell line. Using RPPA data from patients who received either trastuzumab, lapatinib or the combination of both drugs together with chemotherapy in the NCT00524303 clinical trial, we found that 18% (n=38) of tumours had decreased MAPK and increased AKT phosphorylation 14 days after treatment with HER2-targeted therapies. The combination of MEK inhibition (MEKi) with refametinib and copanlisib led to synergistic inhibition of growth in 4/6 cell lines tested (CI @ED75 = 0.39-0.75), whilst the combinations of lapatinib and refametinib led to synergistic inhibition of growth in 3/6 cell lines (CI @ED75 = 0.39-0.80).
Conclusion
Refametinib alone or in combination with copanlisib or lapatinib could represent an improved treatment strategy for some patients with HER2-positive breast cancer, and should be considered for clinical trial evaluation. The direct down-regulation of MEK/MAPK but not AKT signalling by HER2 inhibition (e.g. by lapatinib or trastuzumab), which we demonstrate occurs in 18% of HER2-positive breast cancers may serve as a potential biomarker of responsiveness to the MEK inhibitor refametinib.
... Previous studies have described that HER2 alteration and multiple bypass signaling might have a correlation with this progress. For example, the abnormal expression and/or activation of signaling molecules includes PI3K [6], RON [7], SRC [8], PP2A [9], CXCR4 [10], NF-jB [11], FOXM1 [12], PI3K/ AKT and MAPK/ERK [13], which participated in Lapatinib resistance through various mechanisms. Generally speaking, these studies demonstrated that multiple gene alterations occurred in Lapatinib-resistant cells. ...
Lapatinib, a novel oral dual tyrosine kinase inhibitor blocking HER1 and HER2 pathways, has presented beneficial effects on breast cancer with positive HER2. However, its efficacy is largely limited by the occurrence of acquired drug resistance. In this study, we aimed to explore the underlying molecular mechanisms of Lapatinib resistance using bioinformatics strategies. The gene expression profile of SKBR3-R (acquired Lapatinib-resistant) and SKBR3 (Lapatinib-sensitive) cell line was downloaded from gene expression omnibus database. Then, the differentially expressed genes (DEGs) were selected using dChip software. Furthermore, gene ontology (GO) and pathway enrichment analyses were carried out by using DAVID database. Finally, the protein–protein interaction network was constructed, and the hub genes in the network were analyzed by using STRING database. A total of 300 DEGs, such as HSPA5, MAP1LC3A and RASSF2, were screened out. GO functional enrichment analysis showed that the genes were associated with cell membrane component-related, stimulus-related and binding-related items. KEGG pathway analysis indicated that three dysfunctional pathways, including PPAR signaling pathway, cytokine–cytokine receptor interaction and pathways in cancer, were enriched. Protein–protein interaction network construction revealed that some hub genes, such as PPARG, TGFBI, TGFBR2, TIMP1, CTGF, UBA52 and JUN, might have an association with Lapatinib resistance. The present study offered new insights into the molecular mechanisms of Lapatinib resistance and identified a series of important hub genes that have the potential to be the targets for treatment of Lapatinib-resistant breast cancer.
... A number of studies have been published on the causes of lapatinib resistance, but the mechanisms are still not well understood, and effective therapies remain to be developed to overcome lapatinib resistance. For example, higher expression levels of several genes, including ABCG2 [24], PA2G4 [25], BECN1 [26], ATG5 [26], MCL1 [27], ER [28], MET [29,30], SPOCK1 [31], SRC [32,33], HIF1A [34], DUSP2 [34], MST1R [35], MAP2K1 [36], MAP2K2 [36], FOXM1 [36], AXL [37] and YBX1 [38], have been shown to correlate with lapatinib resistance, but none of them can be used as diagnostic markers and neither have any therapeutic strategies been developed based on these molecules. ...
... A number of studies have been published on the causes of lapatinib resistance, but the mechanisms are still not well understood, and effective therapies remain to be developed to overcome lapatinib resistance. For example, higher expression levels of several genes, including ABCG2 [24], PA2G4 [25], BECN1 [26], ATG5 [26], MCL1 [27], ER [28], MET [29,30], SPOCK1 [31], SRC [32,33], HIF1A [34], DUSP2 [34], MST1R [35], MAP2K1 [36], MAP2K2 [36], FOXM1 [36], AXL [37] and YBX1 [38], have been shown to correlate with lapatinib resistance, but none of them can be used as diagnostic markers and neither have any therapeutic strategies been developed based on these molecules. ...
... A number of studies have been published on the causes of lapatinib resistance, but the mechanisms are still not well understood, and effective therapies remain to be developed to overcome lapatinib resistance. For example, higher expression levels of several genes, including ABCG2 [24], PA2G4 [25], BECN1 [26], ATG5 [26], MCL1 [27], ER [28], MET [29,30], SPOCK1 [31], SRC [32,33], HIF1A [34], DUSP2 [34], MST1R [35], MAP2K1 [36], MAP2K2 [36], FOXM1 [36], AXL [37] and YBX1 [38], have been shown to correlate with lapatinib resistance, but none of them can be used as diagnostic markers and neither have any therapeutic strategies been developed based on these molecules. ...
Previously we found that the estrogen receptor (ER) related factor ERRF regulates cell proliferation and tumor growth, and its expression is positively associated with ER status and better survival but inversely associated with ERBB2 (also named HER2) status in breast cancer. Here we report that ERRF also plays an important role in the response of ERBB2-positive breast cancer cells to lapatinib, a dual tyrosine kinase inhibitor that interrupts the ERBB2 and EGFR pathway. In ERBB2-positive breast cancer cell lines, lower levels of ERRF expression correlated with lapatinib resistance, restoration of ERRF expression in lapatinib-resistant cell lines JIMT-1 and MDA-MB-453 enhanced their lapatinib responses, and knockdown of ERRF in lapatinib sensitive cell lines BT-474 and SK-BR-3 caused lapatinib resistance. ERRF-enhanced lapatinib sensitivity was also confirmed in xenograft tumors of JIMT-1 cells. In patients with ERBB2-positive breast cancer, higher level of ERRF expression correlated with both pathologic complete response (pCR) to lapatinib and better survival. Mechanistically, ERRF expression in resistant cells promoted lapatinib-induced apoptosis by attenuating MCL1 and ERBB2 expression. These results suggest that ERRF plays an important role in lapatinib response of ERBB2-positive breast cancer, and further study of ERRF could lead to improved prediction and sensitivity of lapatinib response.
... Overall, single-agent MEK inhibitors have been limited as a first-line targeted therapy due to compensatory activation of other onco-genic signaling pathways (42,(47)(48)(49)(50). This has necessitated an approach whereby MEK inhibitors are being tested in combination with other agents (51)(52)(53)(54)(55)(56). Amongst the most common partners for MEK therapy are inhibitors of the PI3K/Akt pathway (50,(57)(58)(59). ...
Involuntary weight loss, a part of the cachexia syndrome, is a debilitating comorbidity of cancer and currently has no treatment options. Results from a recent clinical trial at our institution showed that biliary tract cancer patients treated with a MEK inhibitor exhibited poor tumor responses but surprisingly gained weight and increased their skeletal muscle mass. This implied that MEK inhibition might be anticachectic. To test this potential effect of MEK inhibition, we utilized the established Colon-26 model of cancer cachexia and the MEK1/2 inhibitor MEK162. Results showed that MEK inhibition effectively prevented muscle wasting. Importantly, MEK162 retained its ability to spare muscle loss even in mice bearing a Colon-26 clone resistant to the MEK inhibitor, demonstrating that the effects of blocking MEK are at least in part independent of the tumor. Because single-agent MEK inhibitors have been limited as a first-line targeted therapy due to compensatory activation of other oncogenic signaling pathways, we combined MEK162 with the PI3K/Akt inhibitor buparlisib. Results showed that this combinatorial treatment significantly reduced tumor growth due to a direct activity on Colon-26 tumor cells in vitro and in vivo, while also preserving skeletal muscle mass. Together, our results suggest that as a monotherapy, MEK inhibition preserves muscle mass, but when combined with a PI3K/Akt inhibitor exhibits potent antitumor activity. Thus, combinatorial therapy might serve as a new approach for the treatment of cancer cachexia. Mol Cancer Ther; 16(2); 344–56. ©2016 AACR.
See related article by Kobayashi et al., p. 357
... 29 On the other hand, different reports have identified Erk1/2 aberrant activation as a major factor underlying lapatinib resistance. [48][49][50] Moreover, Erk1/2 activation as a compensatory mechanism, downstream of the tyrosine kinase EphA2 (EPH receptor A2), has been implicated in the development of acquired TZ resistance. 51 Here, we found that TZ and lapatinib failure to abrogate PI3K/AKT and Erk1/2 persistent activation in resistant cells, due precisely to the particular molecular traits present in these cells, results in sustained c-Myc activation and expression and, consequently, in the inability of both agents to upregulate miR-16. ...
ErbB-2 amplification/overexpression accounts for an aggressive breast cancer (BC) subtype (ErbB-2-positive). Enhanced ErbB-2 expression was also found in gastric cancer (GC) and has been correlated with poor clinical outcome. The ErbB-2-targeted therapies trastuzumab (TZ), a monoclonal antibody, and lapatinib, a tyrosine kinase inhibitor, have proved highly beneficial. However, resistance to such therapies remains a major clinical challenge. We here revealed a novel mechanism underlying the antiproliferative effects of both agents in ErbB-2-positive BC and GC. TZ and lapatinib ability to block extracellular signal-regulated kinases 1/2 and phosphatidylinositol-3 kinase (PI3K)/AKT in sensitive cells inhibits c-Myc activation, which results in upregulation of miR-16. Forced expression of miR-16 inhibited in vitro proliferation in BC and GC cells, both sensitive and resistant to TZ and lapatinib, as well as in a preclinical BC model resistant to these agents. This reveals miR-16 role as tumor suppressor in ErbB-2-positive BC and GC. Using genome-wide expression studies and miRNA target prediction algorithms, we identified cyclin J and far upstream element-binding protein 1 (FUBP1) as novel miR-16 targets, which mediate miR-16 antiproliferative effects. Supporting the clinical relevance of our results, we found that high levels of miR-16 and low or null FUBP1 expression correlate with TZ response in ErbB-2-positive primary BCs. These findings highlight a potential role of miR-16 and FUBP1 as biomarkers of sensitivity to TZ therapy. Furthermore, we revealed miR-16 as an innovative therapeutic agent for TZ- and lapatinib-resistant ErbB-2-positive BC and GC.Oncogene advance online publication, 9 May 2016; doi:10.1038/onc.2016.151.
