Presence of phosphorylated hepatocyte growth factor receptor/c-Met is associated with tumor progression and survival in patients with conventional renal cell carcinoma

Targeting c-Met in the treatment of urologic neoplasms: Current status and challenges

At present, studies have found that c-Met is mainly involved in epithelial-mesenchymal transition (EMT) of tumor tissues in urologic neoplasms. Hepatocyte growth factor (HGF) combined with c-Met promotes the mitosis of tumor cells, and then induces motility, angiogenesis, migration, invasion and drug resistance. Therefore, c-Met targeting therapy may have great potential in urologic neoplasms. Many strategies targeting c-Met have been widely used in the study of urologic neoplasms. Although the use of targeting c-Met therapy has a strong biological basis for the treatment of urologic neoplasms, the results of current clinical trials have not yielded significant results. To promote the application of c-Met targeting drugs in the clinical treatment of urologic neoplasms, it is very important to study the detailed mechanism of c-Met in urologic neoplasms and innovate c-Met targeted drugs. This paper firstly discussed the value of c-Met targeted therapy in urologic neoplasms, then summarized the related research progress, and finally explored the potential targets related to the HGF/c-Met signaling pathway. It may provide a new concept for the treatment of middle and late urologic neoplasms.

c-Met and EPHA7 Receptor Tyrosine Kinases Are Related to Prognosis in Clear Cell Renal Cell Carcinoma: Focusing on the Association with Myoferlin Expression

Receptor tyrosine kinases (RTKs) are important targets for clear cell renal cell carcinoma (ccRCC) treatment. Myoferlin is a strong regulator of RTKs. To identify myoferlin-associated RTKs and their prognostic implications in ccRCC, we investigated the expression of RTKs and myoferlin using proteome-based evaluation and immunohistochemical staining in tissue microarray. Multivariate Cox analysis adjusted for TNM stage and WHO grade was performed (n = 410 and 506). Proteomic analysis suggested c-Met and EPHA7 as novel candidates for myoferlin-associated RTKs. We immunohistochemically validated the positive association between c-Met and myoferlin expression. High c-Met expression was independently associated with overall (hazard ratio (HR) = 1.153-2.919) and cancer-specific survival (HR = 1.150-3.389). The prognostic effect of high c-Met expression was also determined in an independent cohort (overall survival, HR = 1.503-3.771). Although expression of EPHA7 and myoferlin was not correlated, EPHA7 expression was independently associated with progression-free (HR = 1.237-4.319) and cancer-specific survival (HR = 1.214-4.558). In addition, network-based prioritization showed co-functional enrichment of c-Met and myoferlin, suggesting a novel regulatory function of myoferlin in c-Met signaling. This study indicates that c-Met and EPHA7 might be useful prognostic biomarkers, and the presumed myoferlin/c-Met pathway could be a novel therapeutic target in ccRCC.

cMET - a prognostic marker in papillary renal cell carcinoma?

BACKGROUND

The tyrosine-protein kinase c-Met plays a decisive role in numerous cellular processes, as a proto-oncogene that supports aggressive tumor behavior. It is still unknown whether c-Met could be relevant for prognosis of papillary RCC (pRCC).

PATIENTS AND METHODS

Specimen collection were a collaboration of the PANZAR consortium. Patients' medical history and tumor specimens were collected from n=197 and n=110 patients with type 1 and 2 pRCC, respectively. Expression of cMET was determined by immunohistochemistry (IHC).

RESULTS

In total, cMET staining was evaluable in of 97/197 type 1 and 63/110 type 2 of pRCC cases. Five-years overall survival reviled no significant difference in dependence of cMET positivity (cMET^- vs. cMET⁺: pRCC type 1: 84.8 % vs. 80.3 %, respectively (p=0.303, log-rank); type 2: 71.4 % vs. 64.4 % respectively (p= 0.239, log-rank)). Interestingly, the subgroup analyses showed a significant difference for cMET expression in T stage and metastases of the pRCC type 2 (p=0.014, p=0.022, chi-square). The cMET positive type 2 collective developed more metastases compared to the cMET negative cohort (pRCC Typ 2 M+: cMET^-: 2 (4.3%) vs. cMET⁺: 12 (19%)).

CONCLUSION

CMET expression did not qualify as a prognostic marker in pRCC for overall survival.

68Ga-EMP-100 PET/CT-a novel ligand for visualizing c-MET expression in metastatic renal cell carcinoma-first in-human biodistribution and imaging results

Background

⁶⁸Ga-EMP-100 is a novel positron emission tomography (PET) ligand that directly targets tumoral c-MET expression. Upregulation of the receptor tyrosin kinase c-MET in renal cell carcinoma (RCC) is correlated with overall survival in metastatic disease (mRCC). Clinicopathological staging of c-MET expression could improve patient management prior to systemic therapy with for instance inhibitors targeting c-MET such as cabozantinib. We present the first in-human data of ⁶⁸Ga-EMP-100 in mRCC patients evaluating uptake characteristics in metastases and primary RCC.

Methods

Twelve patients with mRCC prior to anticipated cabozantinib therapy underwent ⁶⁸Ga-EMP-100 PET/CT imaging. We compared the biodistribution in normal organs and tumor uptake of mRCC lesions by standard uptake value (SUV_mean) and SUV_max measurements. Additionally, metastatic sites on PET were compared to contrast-enhanced computed tomography (CT) and the respective, quantitative PET parameters were assessed and then compared inter- and intra-individually.

Results

Overall, 87 tumor lesions were analyzed. Of these, 68/87 (79.3%) were visually rated c-MET-positive comprising a median SUV_max of 4.35 and SUV_mean of 2.52. Comparing different tumor sites, the highest uptake intensity was found in tumor burden at the primary site (SUV_max 9.05 (4.86–29.16)), followed by bone metastases (SUV_max 5.56 (0.97–15.85)), and lymph node metastases (SUV_max 3.90 (2.13–6.28)) and visceral metastases (SUV_max 3.82 (0.11–16.18)). The occurrence of visually PET-negative lesions (20.7%) was distributed heterogeneously on an intra- and inter-individual level; the largest proportion of PET-negative metastatic lesions were lung and liver metastases. The highest physiological ⁶⁸Ga-EMP-100 accumulation besides the urinary bladder content was seen in the kidneys, followed by moderate uptake in the liver and the spleen, whereas significantly lower uptake intensity was observed in the pancreas and the intestines.

Conclusion

Targeting c-MET expression, ⁶⁸Ga-EMP-100 shows distinctly elevated uptake in mRCC patients with partially high inter- and intra-individual differences comprising both c-MET-positive and c-MET-negative lesions. Our first clinical results warrant further systemic studies investigating the clinical use of ⁶⁸Ga-EMP-100 as a biomarker in mRCC patients.

Novel Pyridine Bioisostere of Cabozantinib as a Potent c-Met Kinase Inhibitor: Synthesis and Anti-Tumor Activity against Hepatocellular Carcinoma

Two novel bioisosteres of cabozantinib, 3 and 4, were designed and synthesized. The benzene ring in the center of the cabozantinib structure was replaced by trimethylpyridine (3) and pyridine (4), respectively. Surprisingly, the two compounds showed extremely contrasting mesenchymal-epithelial transition factor (c-Met) inhibitory activities at 1 μM concentration (4% inhibition of 3 vs. 94% inhibition of 4). The IC₅₀ value of compound 4 was 4.9 nM, similar to that of cabozantinib (5.4 nM). A ligand-based docking study suggested that 4 includes the preferred conformation for the binding to c-Met in the conformational ensemble, but 3 does not. The anti-proliferative activity of compound 4 against hepatocellular carcinoma (Hep3B and Huh7) and non-small-cell lung cancer (A549 and H1299) cell lines was better than that of cabozantinib, whereas 3 did not show a significant anti-proliferative activity. Moreover, the tumor selectivity of compound 4 toward hepatocellular carcinoma cell lines was higher than that of cabozantinib. In the xenograft chick tumor model, compound 4 inhibited Hep3B tumor growth to a much greater extent than cabozantinib. The present study suggests that compound 4 may be a good therapeutic candidate against hepatocellular carcinoma.

PD-1/PD-L1 inhibitors-based treatment for advanced renal cell carcinoma: Mechanisms affecting efficacy and combination therapies

With the widespread use of PD-1/PD-L1 monoclonal antibodies (mAbs) in the treatment of multiple malignant tumors, they were also gradually applied to advanced renal cell carcinoma (aRCC). Nowadays, multiple PD-1/PD-L1 mAbs, such as nivolumab, avelumab, and pembrolizumab, have achieved considerable efficacy in clinical trials. However, due to the primary, adaptive, and acquired resistance to these mAbs, the efficacy of this immunotherapy is not satisfactory. Theories also vary as to why the difference in efficacy occurs. The alterations of PD-L1 expression and the interference of cellular immunity may affect the efficacy. These mechanisms demand to be revealed to achieve a sustained and complete objective response in patients with aRCC. Tyrosine kinase inhibitors have been proven to have synergistic mechanisms with PD-1/PD-L1 mAb in the treatment of aRCC, and CTLA-4 mAb has been shown to have a non-redundant effect with PD-1/PD-L1 mAb to enhance efficacy. Although combinations with targeted agents or other checkpoint mAbs have yielded enhanced clinical outcomes in multiple clinical trials nowadays, the potential of PD-1/PD-L1 mAbs still has a large development space. More potential mechanisms that affect the efficacy demand to be developed and transformed into the clinical treatment of aRCC to search for possible combination regimens. We elucidate these mechanisms in RCC and present existing combination therapies applied in clinical trials. This may help physicians' select treatment options for patients with refractory kidney cancer.

A novel Apigenin derivative suppresses renal cell carcinoma via directly inhibiting wild-type and mutant MET

MET, the receptor of hepatocyte growth factor (HGF), is a driving factor in renal cell carcinoma (RCC) and also a proven drug target for cancer treatment. To improve the activity and to investigate the mechanisms of action of Apigenin (APG), novel derivatives of APG with improved properties were synthesized and their activities against Caki-1 human renal cancer cell line were evaluated. It was found that compound 15e exhibited excellent potency against the growth of multiple RCC cell lines including Caki-1, Caki-2 and ACHN and is superior to APG and Crizotinib. Subsequent investigations demonstrated that compound 15e can inhibit Caki-1 cell proliferation, migration and invasion. Mechanistically, 15e directly targeted the MET kinase domain, decreased its auto-phosphorylation at Y1234/Y1235 and inhibited its kinase activity and downstream signaling. Importantly, 15e had inhibitory activity against mutant MET V1238I and Y1248H which were resistant to approved MET inhibitors Cabozantinib, Crizotinib or Capmatinib. In vivo tumor graft study confirmed that 15e repressed RCC growth through inhibition of MET activation. These results indicate that compound 15e has the potential to be developed as a treatment for RCC, and especially against drug-resistant MET mutations.

Metabolomic Analysis to Elucidate Mechanisms of Sunitinib Resistance in Renal Cell Carcinoma

Metabolomics analysis possibly identifies new therapeutic targets in treatment resistance by measuring changes in metabolites accompanying cancer progression. We previously conducted a global metabolomics (G-Met) study of renal cell carcinoma (RCC) and identified metabolites that may be involved in sunitinib resistance in RCC. Here, we aimed to elucidate possible mechanisms of sunitinib resistance in RCC through intracellular metabolites. We established sunitinib-resistant and control RCC cell lines from tumor tissues of RCC cell (786-O)-injected mice. We also quantified characteristic metabolites identified in our G-Met study to compare intracellular metabolism between the two cell lines using liquid chromatography-mass spectrometry. The established sunitinib-resistant RCC cell line demonstrated significantly desuppressed protein kinase B (Akt) and mesenchymal-to-epithelial transition (MET) phosphorylation compared with the control RCC cell line under sunitinib exposure. Among identified metabolites, glutamine, glutamic acid, and α-KG (involved in glutamine uptake into the tricarboxylic acid (TCA) cycle for energy metabolism); fructose 6-phosphate, D-sedoheptulose 7-phosphate, and glucose 1-phosphate (involved in increased glycolysis and its intermediate metabolites); and glutathione and myoinositol (antioxidant effects) were significantly increased in the sunitinib-resistant RCC cell line. Particularly, glutamine transporter (SLC1A5) expression was significantly increased in sunitinib-resistant RCC cells compared with control cells. In this study, we demonstrated energy metabolism with glutamine uptake and glycolysis upregulation, as well as antioxidant activity, was also associated with sunitinib resistance in RCC cells.

CUL4B promotes aggressive phenotypes of renal cell carcinoma via upregulating c-Met expression

Cullin 4B (CUL4B), encoding a scaffold protein in Cullin RING ubiquitin-ligase complexes (CRL4B), is overexpressed and serves as an oncogene in various solid tumors. However, the roles and the underlying mechanisms of CUL4B in renal cell carcinoma (RCC) are still unknown. In this study, we demonstrated that CUL4B was significantly upregulated in RCC cells and clinical specimens, and its overexpression was correlated with poor survival of RCC patients. Knockdown of CUL4B resulted in the inhibition of proliferation, migration and invasion of RCC cells. Furthermore, we found that the expression of CUL4B is positively correlated with c-Met expression in RCC cells and tissues. Konckdown of c-Met or treatment with c-Met inhibitor, SU11274, could block the increase in cell proliferation, migration and invasion induced by CUL4B-overexpression. We also showed that CUL4B overexpression significantly accelerated xenograft tumor growth, and administration of SU11274 could also abrogate the accelerated tumor growth induced by CUL4B overexpression in vivo. These findings shed light on the contribution of CUL4B to tumorigenesis in RCC via activating c-Met signaling and its therapeutic implications in RCC patients.

Immuno-PET Detects Changes in Multi-RTK Tumor Cell Expression Levels in Response to Targeted Kinase Inhibition

Receptor tyrosine kinase (RTK) coexpression facilitates tumor resistance due to redundancies in the phosphatidylinositol-3′-kinase/protein kinase B and KRAS/extracellular-signal–regulated kinase signaling pathways, among others. Crosstalk between the oncogenic RTK hepatocyte growth factor receptor (MET), epidermal growth factor receptor (EGFR), and human epidermal growth factor receptor 2 (HER2) are involved in tumor resistance to RTK-targeted therapies. Methods: In a relevant renal cell carcinoma patient–derived xenograft model, we use the ⁸⁹Zr-labeled anti-RTK antibodies (immuno-PET) onartuzumab, panitumumab, and trastuzumab to monitor MET, EGFR, and HER2 protein levels, respectively, during treatment with agents to which the model was resistant (cetuximab) or sensitive (INC280 and trametinib). Results: Cetuximab treatment resulted in continued tumor growth, as well as an increase in all RTK protein levels at the tumor in vivo on immuno-PET and ex vivo at the cellular level. Conversely, after dual MET/mitogen-activated protein kinase inhibition, tumor growth was significantly blunted and corresponded to a decrease in RTK levels. Conclusion: These data show the utility of RTK-targeted immuno-PET to annotate RTK changes in protein expression and inform tumor response to targeted therapies.

Pathological roles of c-Met in bladder cancer: Association with cyclooxygenase-2, heme oxygenase-1, vascular endothelial growth factor-A and programmed death ligand 1

c-Met is a receptor tyrosine kinase that binds a specific ligand, namely hepatocyte growth factor (HGF). The HGF/c-Met system is important for malignant aggressiveness in various types of cancer, including bladder cancer (BC). However, although phosphorylation is the essential step required for biological activation of c-Met, pathological roles of phosphorylated c-Met at the clinical and molecular levels in patients with BC are not fully understood. In the present study, the expression levels of c-Met and the phosphorylation of two of its tyrosine residues (pY1234/pY1235 and pY1349) were immunohistochemically examined in 185 BC tissues. The associations between these expression levels and cancer cell invasion, metastasis, and cyclooxygenase-2 (COX-2), heme oxygenase-1 (HO-1), VEGF-A and programmed death ligand 1 (PD-L1) levels were investigated. c-Met was associated with muscle invasion (P=0.021), as well as the expression levels of HO-1 (P=0.028) and PD-L1 (P<0.001), whereas pY1349 c-Met was associated with muscle invasion (P=0.003), metastasis (P=0.025), and COX-2 (P=0.017), HO-1 (P=0.031) and PD-L1 (P=0.001) expression. By contrast, pY1234/1235 c-Met was associated with muscle invasion and metastasis (P=0.006 and P=0.012, respectively), but not with the panel of cancer-associated molecules. Furthermore, COX-2 and PD-L1 expression were associated with muscle invasion and metastasis, respectively (P=0.045 and P=0.036, respectively). Hence, c-Met serves important roles in muscle invasion by regulating HO-1 and PD-L1, whereas its phosphorylation at Y1349 is associated with muscle invasion and metastasis via the regulation of COX-2, HO-1 and PD-L1 in patients with BC. Furthermore, phosphorylation at Y1234/1235 may lead to muscle invasion and metastasis via alternate mechanisms associated with c-Met and pY1349 c-Met.

MMPs, tyrosine kinase signaling and extracellular matrix proteolysis in kidney cancer

Patients diagnosed with metastatic renal cell carcinoma (RCC) have ∼12% chance for 5-year survival. The integrity of the extracellular matrix (ECM) that surrounds tumor cells influences their behavior and, when disturbed, it could facilitate local invasion and spread of tumor cells to distant sites. The interplay between von Hippel-Lindau/hypoxia inducible factor signaling axis and activated kinase networks results in aberrant ECM and tumor progression. Matrix metalloproteinases (MMPs) are proteolytic enzymes implicated in ECM remodeling, tumor angiogenesis, and immune cell infiltration. Understanding the cross-talk between kinase signaling and ECM proteolysis in RCC could provide insights into developing drugs that interfere specifically with the process of invasion. In this review, we discuss changes in the MMPs/ECM axis in RCC, prominent kinase signaling pathways implicated in MMPs induction, and comment on emerging extracellular regulatory networks that modulate MMPs activity.

Dysregulation of Type II Transmembrane Serine Proteases and Ligand-Dependent Activation of MET in Urological Cancers

Unlike in normal epithelium, dysregulated overactivation of various proteases have been reported in cancers. Degradation of pericancerous extracellular matrix leading to cancer cell invasion by matrix metalloproteases is well known evidence. On the other hand, several cell-surface proteases, including type II transmembrane serine proteases (TTSPs), also induce progression through activation of growth factors, protease activating receptors and other proteases. Hepatocyte growth factor (HGF) known as a multifunctional growth factor that upregulates cancer cell motility, invasiveness, proliferative, and anti-apoptotic activities through phosphorylation of MET (a specific receptor of HGF). HGF secreted as inactive zymogen (pro-HGF) from cancer associated stromal fibroblasts, and the proteolytic activation by several TTSPs including matriptase and hepsin is required. The activation is strictly regulated by HGF activator inhibitors (HAIs) in physiological condition. However, downregulation is frequently observed in cancers. Indeed, overactivation of MET by upregulation of matriptase and hepsin accompanied by the downregulation of HAIs in urological cancers (prostate cancer, renal cell carcinoma, and bladder cancer) are also reported, a phenomenon observed in cancer cells with malignant phenotype, and correlated with poor prognosis. In this review, we summarized current reports focusing on TTSPs, HAIs, and MET signaling axis in urological cancers.

MET targeting: time for a rematch

MET, the receptor tyrosine kinase (RTK) for hepatocyte growth factor, is a proto-oncogene involved in embryonic development and throughout life in homeostasis and tissue regeneration. Deregulation of MET signaling has been reported in numerous malignancies, prompting great interest in MET targeting for cancer therapy. The present review offers a summary of the biology of MET and its known functions in normal physiology and carcinogenesis, followed by an overview of the most relevant MET-targeting strategies and corresponding clinical trials, highlighting both past setbacks and promising future prospects. By placing their efforts on a more precise stratification strategy through the genetic analysis of tumors, modern trials such as the NCI-MATCH trial could revive the past enthusiasm for MET-targeted therapy.

Circ-AKT3 inhibits clear cell renal cell carcinoma metastasis via altering miR-296-3p/E-cadherin signals

BACKGROUND

Circular RNA (circRNA) is a type of circular endogenous RNA produced by special selective splicing and participates in progression of diverse diseases. However, the role of circRNA in clear cell renal cell carcinoma (ccRCC) is still rarely reported.

METHODS

We detected lower circ-AKT3 expression in ccRCC using the circular RNA microarray. Then, qPCR array was applied to verify the expression of circ-AKT3 in between 60 ccRCC tissues and adjacent normal tissues, as well as ccRCC cell lines and human normal kidney cell (HK-2). We investigated the function of circ-AKT3 in ccRCC in vitro and in vivo and detected underlying mechanisms by Western blotting, bioinformatic analysis, RNA pull-down assay and luciferase reporter assay.

RESULTS

Circ-AKT3 was verified significantly downregulated in ccRCC. Knockdown of circ-AKT3 promoted ccRCC migration and invasion, while overexpression of circ-AKT3 suppressed ccRCC metastasis. Further, circ-AKT3/miR-296-3p/E-cadherin axis was shown responsible for circ-AKT3 inhibiting ccRCC metastasis.

CONCLUSION

Circ-AKT3 suppresses ccRCC metastasis by enforcing E-cadherin expression through competitively binding miR-296-3p. Circ-AKT3 may therefore serve as a novel therapeutic to better suppress ccRCC metastasis.

C-Met as a Key Factor Responsible for Sustaining Undifferentiated Phenotype and Therapy Resistance in Renal Carcinomas

C-Met tyrosine kinase receptor plays an important role under normal and pathological conditions. In tumor cells’ overexpression or incorrect activation of c-Met, this leads to stimulation of proliferation, survival and increase of motile activity. This receptor is also described as a marker of cancer initiating cells. The latest research shows that the c-Met receptor has an influence on the development of resistance to targeted cancer treatment. High c-Met expression and activation in renal cell carcinomas is associated with the progression of the disease and poor survival of patients. C-Met receptor has become a therapeutic target in kidney cancer. However, the therapies used so far using c-Met tyrosine kinase inhibitors demonstrate resistance to treatment. On the other hand, the c-Met pathway may act as an alternative target pathway in tumors that are resistant to other therapies. Combination treatment together with c-Met inhibitor reduces tumor growth, vascularization and pro-metastatic behavior and results in suppressed mesenchymal phenotype and vascular endothelial growth factor (VEGF) secretion. Recently, it has been shown that the acquirement of mesenchymal phenotype or lack of cell differentiation might be related to the presence of the c-Met receptor and is consequently responsible for therapy resistance. This review presents the results from recent studies identifying c-Met as an important factor in renal carcinomas being responsible for tumor growth, progression and metastasis, indicating the role of c-Met in resistance to antitumor therapy and demonstrating the pivotal role of c-Met in supporting mesenchymal cell phenotype.

Dysregulated HAI-2 Plays an Important Role in Renal Cell Carcinoma Bone Metastasis through Ligand-Dependent MET Phosphorylation

MET, a c-met proto-oncogene product and hepatocyte growth factor (HGF) receptor, is known to play an important role in cancer progression, including bone metastasis. In a previous study, we reported increased expression of MET and matriptase, a novel activator of HGF, in bone metastasis. In this study, we employed a mouse model of renal cell carcinoma (RCC) bone metastasis to clarify the significance of the HGF/MET signaling axis and the regulator of HGF activator inhibitor type-2 (HAI-2). Luciferase-transfected 786-O cells were injected into the left cardiac ventricle of mice to prepare the mouse model of bone metastasis. The formation of bone metastasis was confirmed by whole-body bioluminescent imaging, and specimens were extracted. Expression of HGF/MET-related molecules was analyzed. Based on the results, we produced HAI-2 stable knockdown 786-O cells, and analyzed invasiveness and motility. Expression of HGF and matriptase was increased in bone metastasis compared with the control, while that of HAI-2 was decreased. Furthermore, we confirmed increased phosphorylation of MET in bone metastasis. The expression of matriptase was upregulated, and both invasiveness and motility were increased significantly by knockdown of HAI-2. The significance of ligand-dependent MET activation in RCC bone metastasis is considered, and HAI-2 may be an important regulator in this system.

C-met inhibition blocks bone metastasis development induced by renal cancer stem cells

Cancer stem cells (CSCs) are key players in bone metastasis. In some renal tumors CSCs overexpress the HGF receptor c-MET, speculating that c-MET targeting could lead to bone metastasis inhibition. To address this hypothesis we isolated renal CD105+/CD24−CSCs, expressing c-MET receptor from a primary renal carcinoma. Then, to study their ability to metastasize to bone, we injected renal CSCs in NOD/SCID mice implanted with a human bone and we tested the effect of a c-MET inhibitor (JNJ-38877605) on bone metastasis development. JNJ-38877605 inhibited the formation of metastases at bone implant site. We showed that JNJ-38877605 inhibited the activation of osteoclasts induced by RCC stem cells and it stimulated osteoblast activity, finally resulting in a reduction of bone turnover consistent with the inhibition of bone metastases. We measured the circulating levels of osteotropic factors induced by RCC stem cells in the sera of mice treated with c-Met inhibitor, showing that IL-11 and CCL20 were reduced in mice treated with JNJ-38877605, strongly supporting the involvement of c-MET in the regulation of this process. To address the clinical relevance of c-MET upregulation during tumor progression, we analysed c-MET in renal cancer patients detecting an increased expression in the bone metastatic lesions by IHC. Then, we dosed CCL20 serum levels resulting significantly increased in patients with bone metastases compared to non-metastatic ones. Collectively, our data highlight the importance of the c-MET pathway in the pathogenesis of bone metastases induced by RCC stem cells in mice and humans.

Clinicopathological impacts of high c-Met expression in renal cell carcinoma: a meta-analysis and review

c-Met overexpression has been observed in renal cell carcinoma (RCC). However, its clinicopathological impacts remain uncertain. We performed this meta-analysis to evaluate the pathologic and prognostic impacts of high c-Met expression in patients with RCC. A systematic computerized search of the electronic databases PubMed and Embase was performed. From 12 studies, 1,724 patients with RCC were included in the meta-analysis. Compared with RCCs showing low c-Met expression, tumors with high c-Met expression showed significantly higher nuclear grade (odds ratio = 2.45 [95% CI: 1.43-4.19], P = 0.001) and pT stage (odds ratio = 2.18 [95% CI: 1.27-3.72], P = 0.005). In addition, patients with c-Met-high RCC showed significantly worse overall survival than those with c-Met-low tumor (hazard ratio = 1.32 [95% CI: 1.12-1.56], P = 0.0009). In conclusion, this meta-analysis demonstrates that high c-Met expression correlate with significantly worse pathological features and overall survival, indicating c-Met overexpression is a potential adverse prognostic marker for patients with RCC.

Honokiol inhibits c-Met-HO-1 tumor-promoting pathway and its cross-talk with calcineurin inhibitor-mediated renal cancer growth

Honokiol (HNK) is a small molecule with potent anti-inflammatory and anti-tumorigenic properties; yet the molecular targets of HNK are not well studied. Hyperactivation of the receptor tyrosine kinase c-Met and overexpression of the cytoprotective enzyme heme oxygenase-1 (HO-1) play a critical role in the growth and progression of renal cell carcinoma (RCC). Interestingly, the calcineurin inhibitor (CNI) cyclosporine A (CsA), an immunosuppressant used to prevent allograft rejection, can also increase the risk of RCC in transplant patients. We studied the potential role of c-Met signaling axis on CNI-induced renal tumor growth and tested the anti-tumor efficacy of HNK. Importantly, CNI treatment promoted c-Met induction and enhanced c-Met-induced Ras activation. We found that HNK treatment effectively down-regulated both c-Met phosphorylation and Ras activation in renal cancer cells. It inhibited the expression of both c-Met- and CNI-induced HO-1, and promoted cancer cell apoptosis. In vivo, HNK markedly inhibited CNI-induced renal tumor growth; and it decreased the expression of phospho-c-Met and HO-1 and reduced blood vessel density in tumor tissues. Our results suggest a novel mechanism(s) by which HNK exerts its anti-tumor activity through the inhibition of c-Met-Ras-HO-1 axis; and it can have significant therapeutic potential to prevent post-transplantation cancer in immunosuppressed patients.

The role of c-Met in prognosis and clinicopathology of renal cell carcinoma: Results from a single-centre study and systematic review

BACKGROUND AND OBJECTIVES

The c-Met proto-oncogene pathway plays an important role in the progression of various cancers. However, the effect of the c-Met pathway on renal cell carcinoma (RCC) remains controversial. We decided to clarify the role of c-Met in prognosis and clinicopathology of RCC.

METHODS

A total of 10 pairs of tumour and adjacent tissues were obtained from patients with primary RCC between 2013 and 2014 and tissue microarrays to assess c-Met expression in tumour tissues from 90 patients with RCC by Western blot and immunohistochemical staining. We also presented a meta-analysis to explore the correlation between c-Met and pathological grade and stage of RCC. The two-tailed Pearson's χ² and Fischer exact tests were used to compare categorical variables. Multivariate analysis was performed using the multivariate Cox proportional hazards model.

RESULTS

C-Met protein levels were increased in 8 of 10 RCC tissue samples compared with their adjacent normal tissue and c-Met expression levels were positively associated with a high nuclear grade (P = 0.008) and pT stage (P = 0.002). Multivariate analysis showed that a high expression of c-Met was an independent predictor of disease-specific survival (P = 0.017). A meta-analysis found that increased c-Met expression in RCC tissues was closely correlated with high tumour grade (P<0.001) and high pT stage (P = 0.001). Most importantly, c-Met expression was significantly correlated with disease-specific survival (P<0.001).

CONCLUSIONS

Because c-Met is strongly associated with pathological grade, stage and disease-specific survival, c-Met levels may have potential to predict patient prognosis and to guide clinical diagnosis and treatment.

MET expression and copy number status in clear-cell renal cell carcinoma: prognostic value and potential predictive marker

Multiple targeted therapy for advanced clear-cell renal cell carcinoma (RCC) has substantially improved patient outcome, but complete remission is uncommon and many tumors eventually develop resistance. Mechanistic, preclinical, and early clinical data highlight c-Met / hepatocyte growth factor receptor as a promising target for RCC therapeutic agents.We have examined MET expression, frequency of MET gene copy gains and MET gene mutation in a large, hospital-based series of renal cell carcinomas with long-term follow-up information.Out of a total of 572 clear-cell RCC, only 17% were negative for MET expression whereas 32% showed high protein levels. High MET expression and MET copy number gains were associated with an aggressive phenotype and an unfavorable patient outcome. Elevated protein levels in absence of gene amplification were not attributed to mutations, based on results of targeted next-generation sequencing.Our data reveal that clear-cell RCC with MET upregulation show an aggressive behavior and MET copy number increase is evident in a substantial percentage of patients with high-grade carcinomas and metastatic disease. Diagnostic assessment of MET expression and amplification may be of predictive value to guide targeted therapy against MET signaling in patients with clear-cell RCC.

c-Met in chromophobe renal cell carcinoma

c-Met plays a role as a prognostic marker in clear cell renal cell carcinoma. In addition, recently the tyrosine kinase inhibitor cabozantinib targeting c-Met was approved for the treatment of advanced renal cell carcinoma (RCC). In contrast to clear cell RCC, little is known about c-Met expression patterns in rarer RCC subtypes. The aim of this study was to evaluate the prevalence, distribution and prognostic impact of c-Met expression on chromophobe (ch)RCC. Patients who underwent renal surgery due to chRCC were retrospectively evaluated. Tumor specimens were analyzed for c-Met expression by immunohistochemistry. Expression data were associated with clinicopathological parameters including patient survival. Eighty-one chRCC patients were eligible for analysis. Twenty-four (29.6%) patients showed a high c-Met expression (c-Met^high, staining intensity higher than median). Our results showed an association between c-Met^high expression and the existence of lymph node metastasis (p = 0.007). No further significant clinicopathological associations with c-Met were identified, also regarding c-Met expression and overall survival. In conclusion, to our knowledge this is the first study evaluating the prognostic impact of c-Met in a considerably large cohort of chRCC. High c-Met expression is associated with the occurrence of lymph node metastasis. This indicates that c-Met might be implicated into metastatic progression in chRCC.

The prospect of precision therapy for renal cell carcinoma

The therapeutic landscape of renal cell carcinoma (RCC) has greatly expanded in the last decade. From being a malignancy orphan of effective therapies, kidney cancer has become today a tumor with several treatment options. Renal cell carcinoma (RCC) is a metabolic disease, being characterized by the dysregulation of metabolic pathways involved in oxygen sensing (VHL/HIF pathway alterations and the subsequent up-regulation of HIF-responsive genes such as VEGF, PDGF, EGF, and glucose transporters GLUT1 and GLUT4, which justify the RCC reliance on aerobic glycolysis), energy sensing (fumarate hydratase-deficient, succinate dehydrogenase-deficient RCC, mutations of HGF/MET pathway resulting in the metabolic Warburg shift marked by RCC increased dependence on aerobic glycolysis and the pentose phosphate shunt, augmented lipogenesis, and reduced AMPK and Krebs cycle activity) and/or nutrient sensing cascade (deregulation of AMPK-TSC1/2-mTOR and PI3K-Akt-mTOR pathways). In this complex scenario it is important to find prognostic and predictive factors that can help in decision making in the treatment of mRCC.

Bone Metastasis from Renal Cell Carcinoma

About one-third of patients with advanced renal cell carcinoma (RCC) have bone metastasis that are often osteolytic and cause substantial morbidity, such as pain, pathologic fracture, spinal cord compression and hypercalcemia. The presence of bone metastasis in RCC is also associated with poor prognosis. Bone-targeted treatment using bisphosphonate and denosumab can reduce skeletal complications in RCC, but does not cure the disease or improve survival. Elucidating the molecular mechanisms of tumor-induced changes in the bone microenvironment is needed to develop effective treatment. The “vicious cycle” hypothesis has been used to describe how tumor cells interact with the bone microenvironment to drive bone destruction and tumor growth. Tumor cells secrete factors like parathyroid hormone-related peptide, transforming growth factor-β and vascular endothelial growth factor, which stimulate osteoblasts and increase the production of the receptor activator of nuclear factor κB ligand (RANKL). In turn, the overexpression of RANKL leads to increased osteoclast formation, activation and survival, thereby enhancing bone resorption. This review presents a general survey on bone metastasis in RCC by natural history, interaction among the immune system, bone and tumor, molecular mechanisms, bone turnover markers, therapies and healthcare burden.

Understanding and Targeting MET Signaling in Solid Tumors - Are We There Yet?

The MET signaling pathway plays an important role in normal physiology and its deregulation has proved critical for development of numerous solid tumors. Different technologies have been used to investigate the genomic and proteomic status of MET in cancer patients and its association with disease prognosis. Moreover, with the development of targeted therapeutic drugs, there is an urgent need to identify potential biomarkers for selection of patients who are more likely to derive benefit from these agents. Unfortunately, the variety of technical platforms and analysis criteria for diagnosis has brought confusion to the field and a lack of agreement in the evaluation of MET status as a prognostic or predictive marker for targeted therapy agents. We review the molecular mechanisms involved in the deregulation of the MET signaling pathway in solid tumors, the different technologies used for diagnosis, and the main factors that affect the outcome, emphasizing the urge for completing analytical and clinical validation of these tests. We also review the current clinical studies with MET targeted agents, which mostly focus on lung cancer.

Design and characterization of the tumor vaccine MGN1601, allogeneic fourfold gene-modified vaccine cells combined with a TLR-9 agonist

The tumor vaccine MGN1601 was designed and developed for treatment of metastatic renal cell carcinoma (mRCC). MGN1601 consists of a combination of fourfold gene-modified cells with the toll-like receptor 9 agonist dSLIM, a powerful connector of innate and adaptive immunity. Vaccine cells originate from a renal cell carcinoma cell line (grown from renal cell carcinoma tissue), express a variety of known tumor-associated antigens (TAA), and are gene modified to transiently express two co-stimulatory molecules, CD80 and CD154, and two cytokines, GM-CSF and IL-7, aimed to support immune response. Proof of concept of the designed vaccine was shown in mice: The murine homologue of the vaccine efficiently (100%) prevented tumor growth when used as prophylactic vaccine in a syngeneic setting. Use of the vaccine in a therapeutic setting showed complete response in 92% of mice as well as synergistic action and necessity of the components. In addition, specific cellular and humoral immune responses in mice were found when used in an allogeneic setting. Immune response to the vaccine was also shown in mRCC patients treated with MGN1601: Peptide array analysis revealed humoral CD4-based immune response to TAA expressed on vaccine cells, including survivin, cyclin D1, and stromelysin.

Targeting MET and AXL overcomes resistance to sunitinib therapy in renal cell carcinoma

Antiangiogenic therapy resistance occurs frequently in patients with metastatic renal cell carcinoma (RCC). The purpose of this study was to understand the mechanism of resistance to sunitinib, an antiangiogenic small molecule, and to exploit this mechanism therapeutically. We hypothesized that sunitinib-induced upregulation of the prometastatic MET and AXL receptors is associated with resistance to sunitinib and with more aggressive tumor behavior. In the present study, tissue microarrays containing sunitinib-treated and untreated RCC tissues were stained with MET and AXL antibodies. The low malignant RCC cell line 786-O was chronically treated with sunitinib and assayed for AXL, MET, epithelial-mesenchymal transition (EMT) protein expression and activation. Co-culture experiments were used to examine the effect of sunitinib pretreatment on endothelial cell growth. The effects of AXL and MET were evaluated in various cell-based models by short hairpin RNA or inhibition by cabozantinib, the multi-tyrosine kinases inhibitor that targets vascular endothelial growth factor receptor, MET and AXL. Xenograft mouse models tested the ability of cabozantinib to rescue sunitinib resistance. We demonstrated that increased AXL and MET expression was associated with inferior clinical outcome in patients. Chronic sunitinib treatment of RCC cell lines activated both AXL and MET, induced EMT-associated gene expression changes, including upregulation of Snail and β-catenin, and increased cell migration and invasion. Pretreatment with sunitinib enhanced angiogenesis in 786-0/human umbilical vein endothelial cell co-culture models. The suppression of AXL or MET expression and the inhibition of AXL and MET activation using cabozantinib both impaired chronic sunitinib treatment-induced prometastatic behavior in cell culture and rescued acquired resistance to sunitinib in xenograft models. In summary, chronic sunitinib treatment induces the activation of AXL and MET signaling and promotes prometastatic behavior and angiogenesis. The inhibition of AXL and MET activity may overcome resistance induced by prolonged sunitinib therapy in metastatic RCC.

MET Expression in Primary and Metastatic Clear Cell Renal Cell Carcinoma: Implications of Correlative Biomarker Assessment to MET Pathway Inhibitors

Aims. Inhibitors of the MET pathway hold promise in the treatment for metastatic kidney cancer. Assessment of predictive biomarkers may be necessary for appropriate patient selection. Understanding MET expression in metastases and the correlation to the primary site is important, as distant tissue is not always available. Methods and Results. MET immunofluorescence was performed using automated quantitative analysis and a tissue microarray containing matched nephrectomy and distant metastatic sites from 34 patients with clear cell renal cell carcinoma. Correlations between MET expressions in matched primary and metastatic sites and the extent of heterogeneity were calculated. The mean expression of MET was not significantly different between primary tumors when compared to metastases (P = 0.1). MET expression weakly correlated between primary and matched metastatic sites (R = 0.5) and a number of cases exhibited very high levels of discordance between these tumors. Heterogeneity within nephrectomy specimens compared to the paired metastatic tissues was not significantly different (P = 0.39). Conclusions. We found that MET expression is not significantly different in primary tumors than metastatic sites and only weakly correlates between matched sites. Moderate concordance of MET expression and significant expression heterogeneity may be a barrier to the development of predictive biomarkers using MET targeting agents.

Genetic and Chromosomal Aberrations and Their Clinical Significance in Renal Neoplasms

The most common form of malignant renal neoplasms is renal cell carcinoma (RCC), which is classified into several different subtypes based on the histomorphological features. However, overlaps in these characteristics may present difficulties in the accurate diagnosis of these subtypes, which have different clinical outcomes. Genomic and molecular studies have revealed unique genetic aberrations in each subtype. Knowledge of these genetic changes in hereditary and sporadic renal neoplasms has given an insight into the various proteins and signalling pathways involved in tumour formation and progression. In this review, the genetic aberrations characteristic to each renal neoplasm subtype are evaluated along with the associated protein products and affected pathways. The potential applications of these genetic aberrations and proteins as diagnostic tools, prognostic markers, or therapeutic targets are also assessed.

Evaluation of tyrosine kinase receptors in brain metastases of clear cell renal cell carcinoma reveals cMet as a negative prognostic factor

AIMS

Brain metastases (BMs) of clear cell renal cell carcinoma (ccRCC) are associated with a dismal prognosis, with limited treatment options. Tyrosine kinases are relevant 'druggable' biomarkers. The aim of this study was to evaluate the tyrosine kinase receptors anaplastic lymphoma kinase (ALK), epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor-α (PDGFRA) and cMet in a large series of ccRCC BMs.

METHODS AND RESULTS

ALK, EGFR, PDGFRA and cMet protein expression was determined by immunohistochemistry in 53 ccRCCs BMs and 12 matched primary tumours. ALK and MET gene status and copy number alterations of chromosome 7 were studied with fluorescence in-situ hybridization (FISH). Data on the expression of hypoxia-inducible factor 1α (HIF1α) and Ki67 and microvessel density were available from previous studies. ALK was negative in all analysed specimens. EGFR was overexpressed in 41 of 51 (80.4%) BMs and in seven of eight primary tumours, PDGFRA was overexpressed in all BMs except one and in all primary tumours, and cMet was expressed in 26 of 50 (52%) BMs and in two of seven primary tumours, and did not correlate with MET amplification or polysomy 7. cMet was the only parameter associated with significantly shorter BM-specific survival (median 8 months versus 33 months, P = 0.005, Cox regression).

CONCLUSIONS

EGFR, PDGFRA and cMet are commonly overexpressed in ccRCC BMs. cMet overexpression correlates with significantly shorter BM-specific survival.

Novel roles of c-Met in the survival of renal cancer cells through the regulation of HO-1 and PD-L1 expression

The receptor tyrosine kinase c-Met is overexpressed in renal cancer cells and can play major role in the growth and survival of tumor. We investigated how the c-Met-mediated signaling through binding to its ligand hepatocyte growth factor (HGF) can modulate the apoptosis and immune escape mechanism(s) of renal cancer cells by the regulations of novel molecules heme oxygenase-1 (HO-1) and programmed death-1 ligand 1 (PD-L1). We found that HGF/c-Met-mediated signaling activated the Ras/Raf pathway and down-regulated cancer cell apoptosis; and it was associated with the overexpression of cytoprotective HO-1 and anti-apoptotic Bcl-2/Bcl-xL. c-Met-induced HO-1 overexpression was regulated at the transcriptional level. Next, we observed that c-Met induction markedly up-regulated the expression of the negative co-stimulatory molecule PD-L1, and this can be prevented following treatment of the cells with pharmacological inhibitors of c-Met. Interestingly, HGF/c-Met-mediated signaling could not induce PD-L1 at the optimum level when either Ras or HO-1 was knocked down. To study the functional significance of c-Met-induced PD-L1 expression, we performed a co-culture assay using mouse splenocytes (expressing PD-L1 receptor PD-1) and murine renal cancer cells (RENCA, expressing high PD-L1). We observed that the splenocyte-mediated apoptosis of cancer cells during co-culture was markedly increased in the presence of either c-Met inhibitor or PD-L1 neutralizing antibody. Finally, we found that both c-Met and PD-L1 are significantly up-regulated and co-localized in human renal cancer tissues. Together, our study suggests a novel mechanism(s) by which c-Met can promote increased survival of renal cancer cells through the regulation of HO-1 and PD-L1.

Matriptase and MET are prominently expressed at the site of bone metastasis in renal cell carcinoma: immunohistochemical analysis

High MET expression in renal cell carcinoma (RCC) and MET activation in bone metastases are reportedly important in progression of several cancers. To find new treatment targets in bone metastasis, we immunohistochemically analyzed expression levels of MET and matriptase (specific cellular activator of hepatocyte growth factor). We obtained nephrectomy specimens from 17 RCC patients with metastasis, and bone metastases specimens from 7 RCC patients who underwent metastasectomies, and who were treated at our hospital between 2008 and 2012. We tested the samples with anti-human MET polyclonal antibody and anti-human matriptase polyclonal antibody, and compared postoperative overall survival (OS) rates between positive and negative groups. High MET expression was seen at primary sites in 8/17 (47 %) nephrectomy specimens, and 6/7 (86 %) bone specimens. Matriptase was expressed in 6/17 (35 %) nephrectomy specimens, and all 7 (100 %) bone specimens. Interestingly, matriptase was strongly expressed in osteoclasts of 5/7 bone specimens. Postoperative OS rate was significantly higher in the MET⁻ group than the MET⁺ group. The high MET and matriptase expression seen in RCC cells in bone metastasis accompanied by matriptase expression in osteoclasts indicates their importance in bone metastasis.

Microvesicles derived from human Wharton's jelly mesenchymal stem cells promote human renal cancer cell growth and aggressiveness through induction of hepatocyte growth factor

In our previous study, microvesicles (MVs) released from human Wharton's jelly mesenchymal stem cells (hWJ-MSCs) retard the growth of bladder cancer cells. We would like to know if MVs have a similar effect on human renal cell carcinoma (RCC). By use of cell culture and the BALB/c nu/nu mice xeno-graft model, the influence of MVs upon the growth and aggressiveness of RCC (786-0) was assessed. Cell counting kit-8 (CCK-8) assay, incidence of tumor, tumor size, Ki-67 or TUNEL staining was used to evaluate tumor cell growth in vitro or in vivo. Flow cytometry assay (in vitro) or examination of cyclin D1 expression (in vivo) was carried out to determine the alteration of cell cycle. The aggressiveness was analyzed by Wound Healing Assay (in vitro) or MMP-2 and MMP-9 expression (in vivo). AKT/p-AKT, ERK1/2/p-ERK1/2 or HGF/c-MET expression was detected by real-time PCR or western blot. Our data demonstrated that MVs promote the growth and aggressiveness of RCC both in vitro and in vivo. In addition, MVs facilitated the progression of cell cycle from G_0/1 to S. HGF expression in RCC was greatly induced by MVs, associated with activation of AKT and ERK1/2 signaling pathways. RNase pre-treatment abrogated all effects of MVs. In summary, induction of HGF synthesis via RNA transferred by MVs activating AKT and ERK1/2 signaling is one of crucial contributors to the pro-tumor effect.

Targeting the hepatocyte growth factor/c-Met signaling pathway in renal cell carcinoma

The product of a proto-oncogene, the c-Met protein is a transmembrane receptor tyrosine kinase. Its only known ligand, hepatocyte growth factor/scatter factor, regulates cell growth, motility, migration, invasion, proliferation, and angiogenesis. Dysregulation of c-Met and hepatocyte growth factor have been observed in both clear cell and non-clear cell renal cell carcinomas (RCCs), although only papillary RCCs harbor activating mutations in the MET gene. In clear cell RCC, there is evidence of a direct link between loss of von Hippel-Lindau and up-regulation of c-Met. As in other cancers, high expression of c-Met correlates with worse outcomes in RCC. In vitro and in vivo preclinical RCC models demonstrate cancer control with small molecule and antibodies against c-Met. Given these findings, the c-Met pathway is a logical therapeutic target in RCC, and several agents are in clinical testing with early signs of efficacy.

Novel approaches targeting the vascular endothelial growth factor axis in renal cell carcinoma

In recent years, functional characterization of the von Hippel-Lindau tumor suppressor, hypoxia-induced factors, and one of their key downstream effectors, the vascular endothelial growth factor (VEGF), has revolutionized treatment of advanced renal cell carcinoma. Therapeutic strategies targeting the ligand itself (VEGF-A) or its receptor (VEGFR2) have proven successful. However, complete remissions are rare, and with time patients invariably suffer disease progression. It is understood that this is due to incomplete suppression of VEGF signaling and/or adaptive up-regulation of non-VEGF-dependent tumor-promoting stimuli. In this article, we review novel VEGF-directed agents that are being developed to address the shortcomings of current targeted drugs for the treatment of advanced renal cell carcinoma. Building on our current understanding of molecular mechanisms behind resistance, examples include next-generation multitarget tyrosine kinase inhibitors, biologics, and other compounds.

MET genetic abnormalities unreliable for patient selection for therapeutic intervention in oropharyngeal squamous cell carcinoma

Background

Identification of MET genetic alteration, mutation, or amplification in oropharyngeal squamous cell carcinoma (OPSCC) could lead to development of MET selective kinase inhibitors. The aim of this study was to assess the frequency and prognostic value of MET gene mutation, amplification, and protein expression in primary OPSCC.

Methods

A retrospective chart review was conducted of patients treated for single primary OPSCC between January 2007 and December 2009. Pre-treatment OPSCC tissue samples were analyzed for MET mutations, gene amplification, and overexpression using Sanger sequencing, FISH analysis, and immunohistochemistry respectively. Univariate and multivariate analyses were used to analyze correlations between molecular abnormalities and patient survival.

Results

143 patients were included in this study. Six cases (4%) were identified that had a genetic variation, but previously described mutations such as p.Tyr1235Asp (Y1235D) or p.Tyr1230Cys (Y1230C) were not detected. There were 15 high polysomy cases, and only 3 cases met the criteria for true MET amplification, with ≥10% amplified cells per case. Immunohistochemistry evaluation showed 43% of cases were c-MET negative and in 57% c-MET was observed at the tumor cell level. Multivariate analysis showed no significant association between MET mutation, amplification, or expression and survival.

Conclusions

Our study shows a low frequency of MET mutations and amplification in this cohort of OPSCC. There was no significant correlation between MET mutations, amplification, or expression and patient survival. These results suggest that patient selection based on these MET genetic abnormalities may not be a reliable strategy for therapeutic intervention in OPSCC.

Effective inhibition of c-MET-mediated signaling, growth and migration of ovarian cancer cells is influenced by the ovarian tissue microenvironment

The signaling mediated by c-MET and its ligand, hepatocyte growth factor (HGF), has been implicated in malignant progression of cancer involving stimulation of proliferation, invasion, and metastasis. We studied the c-MET/HGF axis as a mediator of tumor-stromal interaction in ovarian cancer and the value of targeting c-MET for the treatment of ovarian cancer. To assess c-MET signaling, we established in vitro models of the microenvironment using primary and immortalized human fibroblasts from normal ovary and tumor samples and epithelial ovarian cancer cell lines. We found that fibroblast from normal ovaries secreted high levels of HGF (1,500 to 3,800 pg/mL) as compared to tumor-derived fibroblasts (undetectable level) and could elicit cellular biological responses on c-MET expressing ovarian cancer cells including increase of cell proliferation and migration (2- to 140-fold increase). HGF secreted by fibroblasts was also found sequestered within extracellular matrices (ECMs) and when degraded this ECM-derived HGF stimulated cancer cell migration (1.5- to 24-fold). In cells containing constitutive c-MET phosphorylation, recombinant HGF and fibroblast-derived HGF negligibly affect c-MET phosphorylation on Tyr¹²³⁴ and Tyr¹⁰⁰³. However, both sources of HGF increased the phosphorylation of c-MET on Tyr¹³⁴⁹, the multi-substrate docking site, by more than 6-fold and led to activation of downstream signaling transducers. DCC-2701 (Deciphera Pharmaceuticals, LLC), a novel c-MET/TIE-2/VEGFR inhibitor was able to effectively reduce tumor burden in vivo and block c-MET pTyr¹³⁴⁹-mediated signaling, cell growth, and migration as compared to a HGF antagonist in vitro. Importantly, DCC-2701’s anti-proliferative activity was dependent on c-MET activation induced by stromal human fibroblasts and to a lesser extent exogenous HGF. Our data suggest for the first time that DCC-2701 may be superior to HGF antagonists that are in clinical trials and that pTyr¹³⁴⁹ levels might be a good indicator of c-MET activation and likely response to targeted therapy as a result of signals from the microenvironment.

Nonclinical evaluation of the serum pharmacodynamic biomarkers HGF and shed MET following dosing with the anti-MET monovalent monoclonal antibody onartuzumab

Onartuzumab, a humanized, monovalent monoclonal anti-MET antibody, antagonizes MET signaling by inhibiting binding of its ligand, hepatocyte growth factor (HGF). We investigated the effects of onartuzumab on cell-associated and circulating (shed) MET (sMET) and circulating HGF in vitro and nonclinically to determine their utility as pharmacodynamic biomarkers for onartuzumab. Effects of onartuzumab on cell-associated MET were assessed by flow cytometry and immunofluorescence. sMET and HGF were measured in cell supernatants and in serum or plasma from multiple species (mouse, cynomolgus monkey, and human) using plate-based immunoassays. Unlike bivalent anti-MET antibodies, onartuzumab stably associates with MET on the surface of cells without inducing MET internalization or shedding. Onartuzumab delayed the clearance of human xenograft tumor-produced sMET from the circulation of mice, and endogenous sMET in cynomolgus monkeys. In mice harboring MET-expressing xenograft tumors, in the absence of onartuzumab, levels of human sMET correlated with tumor size, and may be predictive of MET-expressing tumor burden. Because binding of sMET to onartuzumab in circulation resulted in increasing sMET serum concentrations due to reduced clearance, this likely renders sMET unsuitable as a pharmacodynamic biomarker for onartuzumab. There was no observed effect of onartuzumab on circulating HGF levels in xenograft tumor-bearing mice or endogenous HGF in cynomolgus monkeys. Although sMET and HGF may serve as predictive biomarkers for MET therapeutics, these data do not support their use as pharmacodynamic biomarkers for onartuzumab.

c-Met is a prognostic marker and potential therapeutic target in clear cell renal cell carcinoma

BACKGROUND

Activation of the c-Met pathway occurs in a range of malignancies, including papillary renal cell carcinoma (RCC). Its activity in clear cell RCC is less clear. We investigated c-Met expression and inhibition in a large cohort of RCC tumors and cell lines.

METHODS

c-Met protein expression was determined by automated quantitative analysis (AQUA) on a tissue microarray (TMA) constructed from 330 RCC tumors paired with adjacent normal renal tissue. c-Met expression and selective inhibition with SU11274 and ARQ 197 were studied in clear cell RCC cell lines.

RESULTS

Higher c-Met expression was detected in all RCC subtypes than in the adjacent normal renal tissue (P < 0.0001). Expression was highest in papillary and sarcomatoid subtypes, and high-grade and stage tumors. Higher c-Met expression correlated with worse disease-specific survival [risk ratio = 1.36; 95% confidence interval (CI) 1.08-1.74; P = 0.0091] and was an independent predictor of survival, maintained in clear cell subset analyses. c-Met protein was activated in all cell lines, and proliferation (and colony formation) was blocked by SU11274 and ARQ 197.

CONCLUSIONS

c-Met is associated with poor pathologic features and prognosis in RCC. c-Met inhibition demonstrates in vitro activity against clear cell RCC. Further study of ARQ 197 with appropriate biomarker studies in RCC is warranted.

Dissociation of c-Met phosphotyrosine sites in human cells in response to mouse hepatocyte growth factor but not human hepatocyte growth factor: the possible roles of different amino acids in different species

Hepatocyte growth factor (HGF) is essential for embryogenesis, tissue regeneration and tumour malignancy through the activation of its receptor, c-Met. We previously demonstrated that HGF α-chain hairpin-loop, K1 domain and β-chain are required for c-Met signalling. The sequential phosphorylation of tyrosine residues, from c-Met kinase domain to multidocking regions, is required for HGF-signalling transduction. Herein, we provide evidence that the disconcerted activation of c-Met tyrosine regions fails to induce biological functions. When human cells were incubated with 'mouse HGF', kinase domain activation (i.e. phospho-Tyr-1230/34/35) became evident, but the multidocking site (i.e. Tyr-1349) was not phosphorylated, resulting in unsuccessful induction of migration and mitogenesis. The binding ability of mouse HGF α-chain, or of β-chain, to human c-Met was lower than that of human HGF, as evidenced by HGF-chimera assay. Notably, only four amino acid positions in HGF α-chain hairpin-loop and K1 domain and six positions in β-chain differed between human HGF and mouse HGF. The human-specific amino acids (such as Gln-95 in hairpin-loop, Arg-134 in K1 domain and Cys-561 in β-chain) may be important for accurate c-Met assembly and signalling transduction.

cMET and phospho-cMET protein levels in breast cancers and survival outcomes

PURPOSE

To evaluate cMET (mesenchymal-epithelial transition factor gene) and phospho-cMET (p-cMET) levels in breast cancer subtypes and its impact on survival outcomes.

EXPERIMENTAL DESIGN

We measured protein levels of cMET and p-cMET in 257 breast cancers using reverse phase protein array. Regression tree method and Martingale residual plots were applied to find best cutoff point for high and low levels. Kaplan-Meier survival curves were used to estimate relapse-free (RFS) and overall (OS) survival. Cox proportional hazards models were fit to determine associations of cMET/p-cMET with outcomes after adjustment for other characteristics.

RESULTS

Median age was 51 years. There were 140 (54.5%) hormone receptor (HR) positive, 53 (20.6%) HER2 positive, and 64 (24.9%) triple-negative tumors. Using selected cutoffs, 181 (70.4%) and 123 (47.9%) cancers had high levels of cMET and p-cMET, respectively. There were no significant differences in mean expression of cMET (P < 0.128) and p-cMET (P < 0.088) by breast cancer subtype. Dichotomized cMET and p-cMET level was a significant prognostic factor for RFS [HR: 2.44, 95% confidence interval (CI): 1.34-4.44, P = 0.003 and HR: 1.64, 95% CI: 1.04-2.60, P = 0.033] and OS (HR: 3.18, 95% CI: 1.43-7.11, P = 0.003 and HR: 1.92, 95% CI: 1.08-3.44, P = 0.025). Within breast cancer subtypes, high cMET levels were associated with worse RFS (P = 0.014) and OS (P = 0.006) in HR-positive tumors, and high p-cMET levels were associated with worse RFS (P = 0.019) and OS (P = 0.014) in HER2-positive breast cancers. In multivariable analysis, patients with high cMET had a significantly higher risk of recurrence (HR: 2.06, 95% CI: 1.08-3.94, P = 0.028) and death (HR: 2.81, 95% CI: 1.19-6.64, P = 0.019). High p-cMET level was associated with higher risk of recurrence (HR: 1.79, 95% CI: 1.08-2.95.77, P = 0.020).

CONCLUSIONS

High levels of cMET and p-cMET were seen in all breast cancer subtypes and correlated with poor prognosis.

c-MET protects breast cancer cells from apoptosis induced by sodium butyrate

Sodium Butyrate (NaBu) is regarded as a potential reagent for cancer therapy. In this study, a specific breast cancer cell population that is resistant NaBu treatment was identified. These cells possess cancer stem cell characters, such as the capability of sphere formation in vitro and high tumor incident rate (85%) in mouse model. Forty percent of the NaBu resistant cells express the cancer stem cells marker, the CD133, whereas only 10% intact cells present the CD133 antigen. Furthermore, the endogenous expressing c-MET contributes to the survival of cancer stem cell population from the treatment of NaBu. The CD133+ group also presents a higher level of c-MET. A combination treatment of MET siRNA and NaBu efficiently prohibited the breast cancer progression, and the incident rate of the tumor decrease to 18%. This study may help to develop a new and alternative strategy for breast cancer therapy.

Detection of hepatocyte growth factor (HGF) ligand-c-MET receptor activation in formalin-fixed paraffin embedded specimens by a novel proximity assay

Aberrant activation of membrane receptors frequently occurs in human carcinomas. Detection of phosphorylated receptors is commonly used as an indicator of receptor activation in formalin-fixed paraffin embedded (FFPE) tumor specimens. FFPE is a standard method of specimen preparation used in the histological analysis of solid tumors. Due to variability in FFPE preparations and the labile nature of protein phosphorylation, measurements of phospho-proteins are unreliable and create ambiguities in clinical interpretation. Here, we describe an alternative, novel approach to measure receptor activation by detecting and quantifying ligand-receptor complexes in FFPE specimens. We used hepatocyte growth factor (HGF)-c-MET as our model ligand-receptor system. HGF is the only known ligand of the c-MET tyrosine kinase receptor and HGF binding triggers c-MET phosphorylation. Novel antibody proximity-based assays were developed and used to detect and quantify total c-MET, total HGF, and HGF-c-MET ligand-receptor interactions in FFPE cell line and tumor tissue. In glioma cells, autocrine activation of c-MET by HGF-c-MET increased basal levels of c-MET phosphorylation at tyrosine (Tyr) 1003. Furthermore, HGF-c-MET activation in glioma cell lines was verified by Surface Protein-Protein Interaction by Crosslinking ELISA (SPPICE) assay in corresponding soluble cell lysates. Finally, we profiled levels ofc-MET, HGF, and HGF-c-MET complexes in FFPE specimens of human Non-Small Cell Lung Cancer (NSCLC), Gastric Cancer, Head and Neck Squamous Cell, and Head and Neck Non-Squamous Cell carcinomas. This report describes a novel approach for the detection and quantification of ligand-receptor interactions that can be widely applied to measure receptor activation in FFPE preclinical models and archived FFPE human tissue specimens.