Crizotinib Exhibits Antitumor Activity by Targeting ALK Signaling not c-MET in Pancreatic Cancer

Crizotinib, a c-MET/ALK inhibitor, has exhibited antitumor efficacy in different types of cancers. However, studies regarding Crizotinib in pancreatic cancer have been limited. Thus, we investigated the effect of Crizotinib on pancreatic cancer and its mechanism of action. Crizotinib strongly suppressed the growth and proliferation of pancreatic cancer cells in a dose-dependent manner. Also, it induced apoptosis by modulating its related factors. In the study, with regard to the mechanism of action, Crizotinib did not inhibit c-MET expression on pancreatic cancer cells; instead, it specifically inhibited the activity of ALK, which was identified to be highly expressed on various pancreatic cancer cells and tissues in our study. In 42 different receptor tyrosine kinase (RTKs) array, Crizotinib also strongly inhibited the expression of activated ALK in pancreatic cancer cells, modulating its downstream mediators such as STAT3, AKT, and ERK. Furthermore, Crizotinib inhibited angiogenesis in a mouse Matrigel plug assay as well as the progression of tumor growth in a mouse xenograft model. Taken together, our investigation shows that Crizotinib inhibits the ALK signaling pathway in pancreatic cancer, resulting in cell growth/angiogenesis inhibition and apoptosis induction. We suggest that Crizotinib might be used as a novel therapeutic drug for treating pancreatic cancer.     

Protein-intrinsic and signaling network-based sources of resistance to EGFR- and ErbB family-targeted therapies in head and neck cancer

Agents targeting EGFR and related ErbB family proteins are valuable therapies for the treatment of many cancers. For some tumor types, including squamous cell carcinomas of the head and neck (SCCHN), antibodies targeting EGFR were the first protein-directed agents to show clinical benefit, and remain a standard component of clinical strategies for management of the disease. Nevertheless, many patients display either intrinsic or acquired resistance to these drugs; hence, major research goals are to better understand the underlying causes of resistance, and to develop new therapeutic strategies that boost the impact of EGFR/ErbB inhibitors. In this review, we first summarize current standard use of EGFR inhibitors in the context of SCCHN, and described new agents targeting EGFR currently moving through pre-clinical and clinical development. We then discuss how changes in other transmembrane receptors, including IGF1R, c-Met, and TGF-β, can confer resistance to EGFR-targeted inhibitors, and discuss new agents targeting these proteins. Moving downstream, we discuss critical EGFR-dependent effectors, including PLC-γ; PI3K and PTEN; SHC, GRB2, and RAS and the STAT proteins, as factors in resistance to EGFR-directed inhibitors and as alternative targets of therapeutic inhibition. We summarize alternative sources of resistance among cellular changes that target EGFR itself, through regulation of ligand availability, post-translational modification of EGFR, availability of EGFR partners for hetero-dimerization and control of EGFR intracellular trafficking for recycling versus degradation. Finally, we discuss new strategies to identify effective therapeutic combinations involving EGFR-targeted inhibitors, in the context of new system level data becoming available for analysis of individual tumors.     

Updates on the hepatocyte growth factor/c-Met axis in hepatocellular carcinoma and its therapeutic implications

Hepatocellular carcinoma(HCC) is the fifth most common cancer and is the second leading cause of cancer death. Since the diagnosis of HCC is difficult, in many cases patients with HCC are diagnosed advanced stage of development. Hepatocyte growth factor(HGF)/c-mesenchymal-epithelial transition receptor(c-Met) axis is a key signaling pathway in HCC, either via canonical or non-canonical pathways. Available treatments against HCC based upon HGF/c-Met inhibition can increase patient lifespan, but do not reach the expected therapeutic benefits. In HCC, c-Met monomers can bind other receptor monomers, activating several noncanonical signaling pathways, leading to increased cell proliferation, invasion, motility, and drug resistance. All of these processes are enhanced by the tumor microenvironment, with stromal cells contributing to boost tumor progression through oxidative stress, angiogenesis, lymphangiogenesis, inflammation, and fibrosis. Novel treatments against HCC are being explored to modulate other targets such as microR NAs, methyltransferases, and acetyltransferases, which are all involved in the regulation of gene expression in cancer. This review compiles basic knowledge regarding signaling pathways in HCC, and compounds already used or showing potential to be used in clinical trials.     

Hepatocyte growth factor inhibition: a novel therapeutic approach in pancreatic cancer

Background:

Pancreatic stellate cells (PSCs, which produce the stroma of pancreatic cancer (PC)) interact with cancer cells to facilitate PC growth. A candidate growth factor pathway that may mediate this interaction is the HGF–c-MET pathway.

Methods:

Effects of HGF inhibition (using a neutralising antibody AMG102) alone or in combination with gemcitabine were assessed (i) in vivo using an orthotopic model of PC, and (ii) in vitro using cultured PC cells (AsPC-1) and human PSCs.

Results:

We have shown that human PSCs (hPSCs) secrete HGF but do not express the receptor c-MET, which is present predominantly on cancer cells. HGF inhibition was as effective as standard chemotherapy in inhibiting local tumour growth but was significantly more effective than gemcitabine in reducing tumour angiogenesis and metastasis. HGF inhibition has resulted in reduced metastasis; however, interestingly this antimetastatic effect was lost when combined with gemcitabine. This suggests that gemcitabine treatment selects out a subpopulation of cancer cells with increased epithelial–mesenchymal transition (EMT) and stem-cell characteristics, as supported by our findings of increased expression of EMT and stem-cell markers in tumour sections from our animal model. In vitro studies showed that hPSC secretions induced proliferation and migration, but inhibited apoptosis, of cancer cells. These effects were countered by pretreatment of hPSC secretions with a HGF-neutralising antibody but not by gemcitabine, indicating a key role for HGF in PSC–PC interactions.

Conclusions:

Our studies suggest that targeted therapy to inhibit stromal–tumour interactions mediated by the HGF–c-MET pathway may represent a novel therapeutic approach in PC that will require careful modelling for optimal integration with existing treatment modalities.     

Downstream signalling and specific inhibition of c-MET/HGF pathway in small cell lung cancer: implications for tumour invasion

The c-MET receptor can be overexpressed, amplified, or mutated in solid tumours including small cell lung cancer (SCLC). In c-MET-overexpressing SCLC cell line NCI-H69, hepatocyte growth factor (HGF) dramatically induced c-MET phosphorylation at phosphoepitopes pY1230/1234/1235 (catalytic tyrosine kinase), pY1003 (juxtamembrane), and also of paxillin at pY31 (CRKL-binding site). We utilised a global proteomics phosphoantibody array approach to identify further c-MET/HGF signal transduction intermediates in SCLC. Strong HGF induction of specific phosphorylation sites in phosphoproteins involved in c-MET/HGF signal transduction was detected, namely adducin-alpha [S724], adducin-gamma [S662], CREB [S133], ERK1 [T185/Y187], ERK1/2 [T202/Y204], ERK2 [T185/Y187], MAPKK (MEK) 1/2 [S221/S225], MAPKK (MEK) 3/6 [S189/S207], RB [S612], RB1 [S780], JNK [T183/Y185], STAT3 [S727], focal adhesion kinase (FAK) [Y576/S722/S910], p38alpha-MAPK [T180/Y182], and AKT1[S473] and [T308]. Conversely, inhibition of phosphorylation by HGF in protein kinase C (PKC), protein kinase R (PKR), and also CDK1 was identified. Phosphoantibody-based immunohistochemical analysis of SCLC tumour tissue and microarray established the role of c-MET in SCLC biology. This supports a role of c-MET activation in tumour invasive front in the tumour progression and invasion involving FAK and AKT downstream. The c-MET serves as an attractive therapeutic target in SCLC, as shown through small interfering RNA (siRNA) and selective prototype c-MET inhibitor SU11274, inhibiting the phosphorylation of c-MET itself and its downstream molecules such as AKT, S6 kinase, and ERK1/2. Investigation of mechanisms of invasion and, ultimately, metastasis in SCLC would be very useful with these signal transduction molecules.     

c-MET expression in colorectal adenomas and primary carcinomas with its corresponding metastases

Background

c-MET plays an important role in tumor proliferation, invasion and metastasis. In this study we examined the expression of c-MET in colorectal adenomas, primary adenocarcinomas and their corresponding lymph node, peritoneal and liver metastases. We correlated our findings with clinicopathological features.

Methods

Twenty three cases of colorectal adenoma and 102 cases of primary colorectal carcinoma and their corresponding metastases (44 lymph nodes, 21 peritoneal deposits and 16 liver metastases) were studied to evaluate c-MET expression by immunohistochemistry. For comparison, 12 sections of adjacent healthy colorectal mucosa were examined.

Results

Statistically significant differences were present among normal tissues, colorectal adenomas and primary colorectal carcinomas (P=0.011). Normal tissues showed a negative or weak reaction in 66.67% and 33.33% of cases respectively. Expression of c-MET was positive in 47.8% of adenomas. A significant positive association was identified between c-MET high expression and degree of dysplasia (P=0.024). c-MET was highly expressed in 66.7% of primary colorectal carcinoma. Significant positive correlations were detected between c-MET expression and TNM stage (P=0.036), lymph node metastasis (LNM), peritoneal deposits and liver metastasis (P=0.038, P=0.094 and P=0.045, respectively). c-MET expression in metastatic tissues was significantly higher than that of the primary tumor.

Conclusions

c-MET expression is gradually up-regulated in the development and progression of colorectal cancer (CRC) from normal epithelium to adenoma to colorectal carcinoma to metastases.     

Role of MetMAb (OA-5D5) in c-MET active lung malignancies

Introduction: MetMAb (OA-5D5) is a one-armed monoclonal antibody developed to bind to and inhibit c-MET receptor tyrosine kinase. Though only in early clinical testing, this agent holds great promise in diseases thought to be driven by c-MET activation, as evidenced by the Phase II results in NSCLC where a benefit in overall survival was observed in patients with MET-diagnostic-positive disease. Thus far, both alone and in combination with other targeted agents, this drug has been well tolerated and no new significant safety signals have been identified.

Areas covered: This review summarizes the structure and function of the c-MET receptor and its ligand hepatic growth factor (HGF), provides an overview of select targeted monotherapies developed to interfere in the MET–HGF signaling pathway, discusses pre-clinical and clinical data surrounding MetMAb, and concludes with an expert opinion regarding this novel agent.

Expert opinion: MetMAb has been well tolerated and based on Phase II data testing it, in combination with erlotinib in advanced NSCLC, may have a role in improving survival in patients with disease driven by c-MET activation. However, Phase III validation is underway and the results of these studies will help elucidate which patients will benefit most from this novel agent.     

HGF/c-Met axis drives cancer aggressiveness in the neo-adjuvant setting of ovarian cancer

Ovarian cancer is the most lethal gynecologic malignancy. Recently, NACT (Neo Adjuvant Chemotherapy) has been tested as alternative approach for the management of ovarian cancer patients. A biological predictor helpful in selecting patients for NACT would be desirable. This study was aimed at identifying actionable mechanisms of resistance to NACT.Expression of a panel of microRNAs was screened in a discovery set of 85 patients. Analysis of the potential targets was conducted in the same RNAs by calculating significant correlations between microRNAs and genes. Quantitative fluorescent immunohistochemistry was employed in a validation set of 109 patients.MiR-193a-5p was significantly overexpressed in the NACT setting. Analysis of its potential targets demonstrated that this microRNA is also significantly correlated with HGF and MET genes. Analysis of protein expression in samples taken before and after NACT demonstrated that both HGF and c-Met are increased after NACT. Patients who relapse shortly after NACT exhibited the highest relative basal expression of both HGF and c-Met, while the opposite phenomenon was observed in the best responders.Mir-193a-5p, HGF and c-Met expression may help select eligible patients for this modality of treatment. Moreover, inhibitors of this pathway may improve the efficacy of NACT.     

Tailored therapeutic strategies for synovial sarcoma: Receptor tyrosine kinase pathway analyses predict sensitivity to the mTOR inhibitor RAD001

We examined efficacy of the mTOR inhibitor RAD001 to seek novel therapies for synovial sarcoma (SS). Although RAD001 had significant anti-tumor effects, its sensitivity differed among cell lines. Phospho-receptor tyrosine kinase (RTK) array analyses revealed c-MET phosphorylation in highly mTOR inhibitor-sensitive cells and PDGFRα (which induces intrinsic resistance to mTOR inhibitor) activation in less sensitive cells. Combined treatment with RAD001 and the PDGFR inhibitor pazopanib showed anti-tumor effects in xenograft models with less sensitive cells. Thus, evaluating activated RTKs in clinical samples may predict sensitivity to mTOR inhibitors, raising the possibility of a tailored therapy for SS.