A Phase 1 Study of Cabozantinib and Trifluridine/Tipiracil in Metastatic Colorectal Adenocarcinoma

INTRODUCTION

This study determined the safety and recommended phase 2 dose (RP2D) of the multikinase inhibitor cabozantinib in combination with trifluridine/tipiracil (FTD/TPI) in refractory metastatic colorectal carcinoma (mCRC).

PATIENTS AND METHODS

Single institution investigator-initiated phase 1 study using 3+3 design. Eligible mCRC patients had received prior standard regimens. Cabozantinib was given orally (p.o.) at 20 mg (dose level [DL] 0) or 40 mg (DL 1) daily on days 1-28, and FTD/TPI p.o. at 35 mg/m2 on days 1-5 and 8-12 every 28 days. Prophylactic growth-factor support was allowed.

RESULTS

Fifteen patients were enrolled. Median age 56 years (31-80), male (12/15), ECOG 0/1 = 9/6. Three patients were treated at DL 0 and another nine were treated at DL 1, none exhibiting a DLT. Most common any grade (G) treatment related adverse events (TRAE) were diarrhea (50%), nausea (42%), neutropenia (42%), fatigue (33%), and rash (25%). G3-4 TRAE were neutropenia (25%) and thrombocytopenia, hypokalemia, and weight loss (each 8%). No serious TRAE or G5 were reported. The RP2D was determined to be DL 1. Median PFS was 3.8 months (95% CI 1.9-6.8) and disease control rate was 86.7%.

CONCLUSION

The combination of cabozantinib and FTD/TPI is feasible and tolerable at standard doses with the use of growth factors and showed encouraging clinical activity in refractory mCRC.

CLINICALTRIALS

GOV: NCT04868773.

Cholinergic signaling via muscarinic M1 receptor confers resistance to docetaxel in prostate cancer

Docetaxel is the most commonly used chemotherapy for advanced prostate cancer (PC), including castration-resistant disease (CRPC), but the eventual development of docetaxel resistance constitutes a major clinical challenge. Here, we demonstrate activation of the cholinergic muscarinic M1 receptor (CHRM1) in CRPC cells upon acquiring resistance to docetaxel, which is manifested in tumor tissues from PC patients post- vs. pre-docetaxel. Genetic and pharmacological inactivation of CHRM1 restores the efficacy of docetaxel in resistant cells. Mechanistically, CHRM1, via its first and third extracellular loops, interacts with the SEMA domain of cMET and forms a heteroreceptor complex with cMET, stimulating a downstream mitogen-activated protein polykinase program to confer docetaxel resistance. Dicyclomine, a clinically available CHRM1-selective antagonist, reverts resistance and restricts the growth of multiple docetaxel-resistant CRPC cell lines and patient-derived xenografts. Our study reveals a CHRM1-dictated mechanism for docetaxel resistance and identifies a CHRM1-targeted combinatorial strategy for overcoming docetaxel resistance in PC.

Low co-expression of PD-L1 and oncogenic receptor tyrosine kinases HER2 and cMET in urothelial carcinoma is associated with discordant expression between primary and metastatic sites

OBJECTIVES

Novel regimens targeting immune checkpoints and the cMET or HER2 pathways are under investigation in metastatic urothelial carcinoma (mUC) though co-expression of these molecular targets has not been defined. We sought to characterize the protein co-expression rates of PD-L1, cMET and HER2 in primary and metastatic mUC lesions and agreement rates in paired biopsies.

MATERIALS AND METHODS

We assessed PD-L1, cMET and HER2 protein expression by immunohistochemistry (IHC) in archival mUC samples identified from an institutional database (n = 143). Correlation of expression between primary and metastatic biopsies was performed in patients with available paired biopsies (n = 79). Protein expression levels by predefined thresholds were measured, and Cohen's kappa statistics (κ) were utilized to assess the agreement in expression between paired primary and metastatic samples.

RESULTS

In primary tumors (n = 85), high expression of PD-L1, cMET, and HER2 was observed in 14.1%, 34.1%, and 12.9%, respectively. In metastatic samples (n = 143), high expression of PD-L1, cMET and HER2 was detected in 9.8%, 41.3%, and 9.8%, respectively. Expression agreement rates between paired specimens (n = 79) were PD-L1: 79.7% (κ = 0.09), cMET: 69.6% (κ = 0.35), HER2: 84.8% (κ = 0.17). High PD-L1/cMET co-expression was observed in only 5.1% (n = 4) of primary and 4.9% (n = 7) of metastatic specimens. High co-expression of PD-L1/HER2 occurred in 3.8% (n = 3) of primary samples and no metastatic samples. The overall co-expression agreement between paired samples was 55.7% (κ = 0.22) for PD-L1/cMET and 67.1% (κ = 0.06) for PD-L1/HER2, but agreement for high co-expression between paired samples was very low (2.5% for PD-L1/cMET and 0% for PD-L1/HER2).

CONCLUSIONS

Tumor co-expression of high cMET or HER2 and PD-L1 is low in this cohort. Agreement of high co-expression between primary and metastatic sites is rare. Biomarker-based strategies used in selection of patients for contemporary trials testing combinations of immune checkpoint inhibitors with either cMET or HER2-targeted agents should account for discordant biomarker expression between primary and metastatic sites.

Quinacrine inhibits HIF-1α/VEGF-A mediated angiogenesis by disrupting the interaction between cMET and ABCG2 in patient-derived breast cancer stem cells

BACKGROUND

Breast cancer stem cells (BCSCs) have a critical role in progression of breast cancer by inducing angiogenesis. Several therapeutic strategies have been designed for the treatment of breast cancer by specifically preventing angiogenesis. But there is a dearth of study regarding the treatment procedure which can specifically target and kill the BCSCs and cause lesser harm to healthy cells of the body. A plant-based bioactive compound Quinacrine (QC) specifically kills cancer stem cells (CSCs) without harming healthy cells and also inhibits cancer angiogenesis but the detailed mechanistic study of its anti-CSCs and anti-angiogenic activity is yet to explore.

HYPOTHESIS

Earlier report showed that both cMET and ABCG2 play an essential role in cancer angiogenesis. Both are present on the cell surface of CSCs and share an identical ATP-binding domain. Interestingly, QC a plant based and bioactive compound which was found to inhibit the function of CSCs marker cMET and ABCG2. These relevant evidence led us to hypothesize that cMET and ABCG2 may interact with each other and induce the production of angiogenic factors, resulting in activation of cancer angiogenesis and QC might disrupt the interaction between them to stop this phenomena.

METHODS

Co-immunoprecipitation assay, immunofluorescence assay, and western blotting were performed by using ex vivo patient-derived breast cancer-stem-cells (PDBCSCs) and human umbilical vein endothelial cells (HUVECs). In silico study was carried out to check the interaction between cMET and ABCG2 in presence or absence of QC. Tube formation assay using HUVECs and in ovo Chorioallantoic membrane (CAM) assay using chick fertilized eggs were performed to monitor angiogenesis. In vivo patient-derived xenograft (PDX) mice model was used to validate in silico and ex vivo results.

RESULTS

Data revealed that in a hypoxic tumor microenvironment (TME), cMET and ABCG2 interact with each other and upregulate HIF-1α/VEGF-A axis to induce breast cancer angiogenesis. In silico and ex vivo study showed that QC disrupted the interaction between cMET and ABCG2 to inhibit the angiogenic response in endothelial cells by reducing the secretion of VEGF-A from PDBCSCs within the TME. Knockdown of cMET, ABCG2 or both, significantly downregulated the expression of HIF-1α and reduced the secretion of pro-angiogenic factor VEGF-A in the TME of PDBCSCs. Additionally, when PDBCSCs were treated with QC, similar experimental results were obtained.

CONCLUSION

In silico, in ovo, ex vivo and in vivo data confirmed that QC inhibited the HIF-1α/VEGF-A mediated angiogenesis in breast cancer by disrupting the interaction between cMET and ABCG2.

Quinacrine inhibits cMET-mediated metastasis and angiogenesis in breast cancer stem cells

A trans-membrane receptor tyrosine kinase, cMET, belonging to the MET proto-oncogene family, is responsible for cancer metastasis and angiogenesis. But not much is known about the role of cMET in growth and progression of cancer stem cells (CSCs). Earlier studies have shown that Quinacrine (QC), a bioactive agent, has anti-CSCs activity. Here, the role of QC in deregulation of cMET-mediated metastasis and angiogenesis has been systematically evaluated in vitro in highly metastatic breast CSCs (mBCSCs), ex vivo in patient-derived breast cancer stem cells (PDBCSCs) and in vivo in xenograft mice model systems. Cell proliferation, migration, invasion and representative metastasis markers were upregulated in cMET-overexpressed cells and QC exposure inhibited these processes in both mBCSCs and PDBCSCs. Interestingly, metastasis was significantly inhibited by QC in cMET-overexpressed cells but comparatively lesser significant alteration of the process was noted in cMET-silenced cells. Increase in vascularization (in in ovo CAM assay), and cell-cell tube formation (in HUVECs), and enhanced MMP9 and MMP2 enzymatic activities (in gelatin zymography) were noted after cMET overexpression but these processes got reversed after cMET knockdown or QC treatment in cMET-overexpressed cells. QC inhibited angiogenesis significantly in cMET-overexpressed cells, but lesser significant change was observed in cMET-silenced cells. Reduction in tumor volume and decreased expression of metastatic and angiogenic markers were also noted in xenograft mice after QC treatment. Furthermore, QC inhibited cMET activity by dephosphorylation of its tyrosine residues (Y1234 and Y1356) and downregulation of its downstream cascade. Thus, QC inhibited the cMET-mediated metastasis and angiogenesis in in vitro, in ovo, in vivo and ex vivo model systems. Ligand (HGF) binding leads to receptor dimerization and phosphorylation of tyrosine kinase domain of cMET. This activates the cMET signaling cascade. The representative downstream metastasis and angiogenesis-related proteins get upregulated and induce the metastasis and angiogenesis process. But after the QC treatment, cMET get dephosphorylated and inactivated. As a result, the downstream signaling proteins of cMET along with the other representative metastatic and angiogenic factors get downregulated. These lead to inhibition of cMET-mediated metastasis and angiogenesis. (Created with BioRender.com).

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.

cMET promotes metastasis and epithelial-mesenchymal transition in colorectal carcinoma by repressing RKIP

Increasing evidence indicates that c-mesenchymal-epithelial transition factor (cMET) plays an important role in the malignant progression of colorectal cancer (CRC). However, the underlying mechanism is not fully understood. As a metastasis suppressor, raf kinase inhibitory protein (RKIP) loss has been reported in many cancer types. In this study, the expression levels of cMET and RKIP in CRC tissues and cell lines were determined, and their crosstalk and potential biological effects were explored in vitro and in vivo. Our results showed that cMET was inversely correlated with RKIP. Both cMET upregulation and RKIP downregulation indicated poor clinical outcomes. Moreover, the MAPK/ERK signaling pathway was implicated in the regulation of cMET and RKIP. Overexpression of cMET promoted tumor cell epithelial-mesenchymal transition, invasion, migration, and chemoresistance, whereas the effects could be efficiently inhibited by increased RKIP. Notably, small hairpin RNA-mediated cMET knockdown dramatically suppressed cell proliferation, although no RKIP-induced influence on cell growth was observed in CRC. Altogether, cMET overexpression may contribute to tumor progression by inhibiting the antioncogene RKIP, providing preclinical justification for targeting RKIP to treat cMET-induced metastasis of CRC.

Prognostic relevance of longitudinal HGF levels in serum of patients with ovarian cancer

The pleiotropic protein hepatocyte growth factor (HGF) is the only known ligand of the tyrosine kinase mesenchymal–epithelial transition (cMET) receptor. The HGF/cMET pathway mediates invasion and migration of ovarian cancer cells, and upregulation of HGF/cMET pathway components has been associated with poor prognosis. This study investigated the clinical relevance of circulating HGF in serum of patients with ovarian cancer. Serum HGF (sHGF) was determined by enzyme‐linked immunosorbent assay in a total of 471 serum samples from 82 healthy controls and 113 patients with ovarian cancer (88.5% with ≥ FIGO III). Patient samples were collected at primary diagnosis and at four follow‐up time points throughout treatment and at disease recurrence. Patients with ovarian cancer showed elevated median sHGF levels at primary diagnosis, and sHGF levels transiently increased after surgery and normalized in the course of chemotherapy, even dropping below initial baseline. Higher levels of sHGF were an independent predictor for shorter overall survival (OS) (a) at primary diagnosis (HR = 0.41, 95% CI: 0.22–0.78, P = 0.006), (b) at longitudinal follow‐up time points (after surgery and before/during/after chemotherapy), (c) along the patients’ individual dynamics (HR = 0.21, 95% CI: 0.07–0.63, P = 0.005), and (d) among a subgroup analysis of patients with BRCA1/2 wild‐type ovarian cancer. This is the first study proposing sHGF as an independent prognostic biomarker for ovarian cancer at primary diagnosis and in the course of platinum‐based chemotherapy, irrespective of the postoperative residual disease after surgical debulking. sHGF could be implemented into clinical diagnostics as a CA125 auxiliary tumor marker for individualized prognosis stratification and sHGF‐guided therapy monitoring.

Therapeutic Strategies and Biomarkers to Modulate PARP Activity for Targeted Cancer Therapy

Poly-(ADP-ribose) polymerase 1 (PARP1) is commonly known for its vital role in DNA damage response and repair. However, its enzymatic activity has been linked to a plethora of physiological and pathophysiological transactions ranging from cellular proliferation, survival and death. For instance, malignancies with BRCA1/2 mutations heavily rely on PARP activity for survival. Thus, the use of PARP inhibitors is a well-established intervention in these types of tumors. However, recent studies indicate that the therapeutic potential of attenuating PARP1 activity in recalcitrant tumors, especially where PARP1 is aberrantly overexpressed and hyperactivated, may extend its therapeutic utility in wider cancer types beyond BRCA-deficiency. Here, we discuss treatment strategies to expand the tumor-selective therapeutic application of PARP inhibitors and novel approaches with predictive biomarkers to perturb NAD⁺ levels and hyperPARylation that inactivate PARP in recalcitrant tumors. We also provide an overview of genetic alterations that transform non-BRCA mutant cancers to a state of "BRCAness" as potential biomarkers for synthetic lethality with PARP inhibitors. Finally, we discuss a paradigm shift for the use of novel PARP inhibitors outside of cancer treatment, where it has the potential to rescue normal cells from severe oxidative damage during ischemia-reperfusion injury induced by surgery and radiotherapy.

Crizotinib sensitizes the erlotinib resistant HCC827GR5 cell line by influencing lysosomal function

In non-small cell lung cancer, sensitizing mutations in epidermal growth factor receptor (EGFR) or cMET amplification serve as good biomarkers for targeted therapies against EGFR or cMET, respectively. Here we aimed to determine how this different genetic background would affect the interaction between the EGFR-inhibitor erlotinib and the cMET-inhibitor crizotinib. To unravel the mechanism of synergy we investigated the effect of the drugs on various parameters, including cell cycle arrest, migration, protein phosphorylation, kinase activity, the expression of drug efflux pumps, intracellular drug concentrations, and live-cell microscopy. We observed additive effects in EBC-1, H1975, and HCC827, and a strong synergism in the HCC827GR5 cell line. This cell line is a clone of the HCC827 cells that harbor an EGFR exon 19 deletion and has been made resistant to the EGFR-inhibitor gefitinib, resulting in cMET amplification. Remarkably, the intracellular concentration of crizotinib was significantly higher in HCC827GR5 compared to the parental HCC827 cell line. Furthermore, live-cell microscopy with a pH-sensitive probe showed a differential reaction of the pH in the cytoplasm and the lysosomes after drug treatment in the HCC827GR5 in comparison with the HCC827 cells. This change in pH could influence the process of lysosomal sequestration of drugs. These results led us to the conclusion that lysosomal sequestration is involved in the strong synergistic reaction of the HCC827GR5 cell line to crizotinib-erlotinib combination. This finding warrants future clinical studies to evaluate whether genetic background and lysosomal sequestration could guide tailored therapeutic interventions.

EGFR, KRAS, BRAF, ALK, and cMET genetic alterations in 1440 Sardinian patients with lung adenocarcinoma

Background

Lung cancer is one of the most incident neoplastic diseases, and a leading cause of death for cancer worldwide. Knowledge of the incidence of druggable genetic alterations, their correlation with clinical and pathological features of the disease, and their interplay in cases of co-occurrence is crucial for selecting the best therapeutic strategies of patients with non-small cell lung cancer. In this real-life study, we describe the molecular epidemiology of genetic alterations in five driver genes and their correlations with the demographic and clinical characteristics of Sardinian patients with lung adenocarcinoma.

Methods

Data from 1440 consecutive Sardinian patients with a histologically proven diagnosis of lung adenocarcinoma from January 2011 through July 2016 were prospectively investigated. EGFR mutation analysis was performed for all of them, while KRAS and BRAF mutations were searched in 1047 cases; ALK alterations were determined with fluorescence in situ hybridization in 899 cases, and cMET amplifications in 788 cases.

Results

KRAS mutations were the most common genetic alterations involving 22.1% of the cases and being mutually exclusive with the EGFR mutations, which were found in 12.6% of them. BRAF mutations, ALK rearrangements, and cMET amplifications were detected in 3.2, 5.3, and 2.1% of the cases, respectively. Concomitant mutations were detected only in a few cases.

Conclusions

Almost all the genetic alterations studied showed a similar incidence in comparison with other Caucasian populations. Concomitant mutations were rare, and they probably have a scarce impact on the clinical management of Sardinians with lung adenocarcinoma. The low incidence of concomitant cMET amplifications at diagnosis suggests that these alterations are acquired in subsequent phases of the disease, often during treatment with TKIs.

Structure based designing of triazolopyrimidone-based reversible inhibitors for kinases involved in NSCLC

Secondary acquired mutant EGFR (L858R-T790M) overexpressed NSCLC forms one of the prevalent form of resistant NSCLC. Another subset of resistant NSCLC includes amplified cMET in mutant EGFR derived tumours. Thus, in continuation to our previous work on these two major targets of resistant NSCLC, i.e., EGFR (L858R-T790M) and cMET, we are hereby reporting reversible inhibitors of these kinases. Out of 11 lead molecules reported in our previous study, we selected triazolo-pyrimidone (BAS 09867482) scaffold for further development of small molecule dual and reversible inhibitors. Analogues of lead with different substituents on the side ring were sketched and docked in both the target kinases, followed by molecular dynamic simulations. Analogues maintaining hydrophobic interaction with M790 in secondary acquired mutant EGFR (L858R-T790M) were selected and duly synthesized. In vitro biochemical evaluation of these molecules against EGFR (L858R-T790M) and cMET kinase, along with EGFR (L858R) kinase disclosed that three molecules were having significant dual kinase inhibitory potential with IC₅₀ values well below 100 nM. Further, in vitro anti-proliferative assay against three cell lines (A549, A431 and H460) was performed. Out of all, two compounds were having significant potency against these cell lines.

Loss of SR-BI Down-Regulates MITF and Suppresses Extracellular Vesicle Release in Human Melanoma

Melanoma is a skin tumor with a high tendency for metastasis and thus is one of the deadliest cancers worldwide. Here, we investigated the expression of the scavenger receptor class B type 1 (SR-BI), a high-density lipoprotein (HDL) receptor, and tested for its role in melanoma pigmentation as well as extracellular vesicle release. We first analyzed the expression of SR-BI in patient samples and found a strong correlation with MITF expression as well as with the melanin synthesis pathway. Hence, we asked whether SR-BI could also play a role for the secretory pathway in metastatic melanoma cells. Interestingly, gain- and loss-of-function of SR-BI revealed regulation of the proto-oncogene MET. In line, SR-BI knockdown reduced expression of the small GTPase RABB22A, the ESCRT-II protein VPS25, and SNAP25, a member of the SNARE complex. Accordingly, reduced overall extracellular vesicle generation was detected upon loss of SR-BI. In summary, SR-BI expression in human melanoma enhances the formation and transport of extracellular vesicles, thereby contributing to the metastatic phenotype. Therapeutic targeting of SR-BI would not only interfere with cholesterol uptake, but also with the secretory pathway, therefore suppressing a key hallmark of the metastatic program.

MiRNA-206 inhibits hepatocellular carcinoma cell proliferation and migration but promotes apoptosis by modulating cMET expression

A close relationship between cancer progression and microRNAs (miRNAs) regulation has been demonstrated. Abnormal microRNA-206 (miR-206) expression has been shown to be related to the development of malignancies. However, the role of miR-206 in hepatocellular carcinoma (HCC) remains unclear. Here, we evaluated the function of miR-206 in HCC. Results showed that miR-206 expression was decreased in 27 human HCC tissues compared with that of adjacent normal tissues. Conversely, cMET was up-regulated in human HCC cancer tissues, and cMET levels were shown to be negatively correlated with miR-206 expression. Abnormally increased miR-206 expression in three HCC cell lines (SMMC-7721, HepG2, and Huh7) attenuated cell viability, migration, and invasion. Increased apoptosis was also observed in these miR-206 expressing cells. Furthermore, we identified that miR-206 targets the 3'-UTR of the cMET gene for silencing, and restoration of cMET expression reversed the inhibitory effect of miR-206 on HCC. Tumor cells expressing miR-206 also showed delayed growth in the in vivo experiments compared with the controls. Altogether, our findings provide new insights into the molecular mechanisms of HCC oncogenesis.

Whole-exome sequencing identifies key mutated genes in T790M wildtype/cMET-unamplified lung adenocarcinoma with acquired resistance to first-generation EGFR tyrosine kinase inhibitors

PURPOSE

Lung cancer is the leading cause of cancer-related death worldwide. Lung adenocarcinoma harboring EGFR-activating mutations will inevitably acquire resistance to first-generation EGFR tyrosine kinase inhibitors (TKIs). EGFR T790M mutation and cMET amplification are common mechanisms. Further study is needed to explore unknown genomic alterations contributing to drug resistance.

METHODS

Tumor and blood samples from 69 stage IIIB-IV NSCLC patients defined as acquired resistance to first-generation EGFR TKIs (gefitinib, erlotinib or ecotinib) were collected. The cobas^® and Droplet digital PCR (ddPCR) were used to detect T790M mutations in tumor samples and plasma ctDNA. cMET amplification was evaluated by fluorescence in situ hybridization (FISH). Exome sequencing was performed in four T790M wildtype/cMET-unamplified samples.

RESULTS

The overall T790M-positive rate was 52.2% considering all testing methods. Out of 21 samples in which tumor re-biopsy was performed, 14 were T790M positive (66.7%). cMET amplification was identified in three out of seven T790M-negative samples. Exome sequencing in four T790M wildtype/cMET-unamplified samples and paired white blood cells identified a cohort of candidate key mutated genes including BRAF, FGFR1, PAK1, PCNT, PEBP4 and SOX3.

CONCLUSIONS

EGFR T790M mutation and cMET amplification are main mechanisms leading to EGFR TKI resistance in lung adenocarcinoma. These key mutated genes identified in the present study would need further validation in large number of patients.

Differential response to ablative ionizing radiation in genetically distinct non-small cell lung cancer cells

Stereotactic ablative radiotherapy (SABR) has emerged as a highly promising treatment for medically inoperable early-stage non-small cell lung cancer patients. Treatment outcomes after SABR have been excellent compared to conventional fractionated radiotherapy (CFRT). However, the biological determinants of the response to ablative doses of radiation remain poorly characterized. Furthermore, there's little data on the cellular and molecular response of genetically distinct NSCLC subtypes to radiation. We assessed the response of 3 genetically distinct lung adenocarcinoma cell lines to ablative and fractionated ionizing radiation (AIR and FIR). We studied clonogenic survival, cell proliferation, migration, invasion, apoptosis and senescence. We also investigated the effect of AIR and FIR on the expression of pro-invasive proteins, epithelial-to-mesenchymal transition (EMT), extracellular signal-regulated kinases (ERK1/2) and the transmembrane receptor cMET. Our findings reveal that AIR significantly reduced cell proliferation and clonogenic survival compared to FIR in A549 cells only. This differential response was not observed in HCC827 or H1975 cells. AIR significantly enhanced the invasiveness of A549 cells, but not HCC827 or H1975 cells compared to FIR. Molecular analysis of pathways involved in cell proliferation and invasion revealed that AIR significantly reduced phosphorylation of ERK1/2 and upregulated cMET expression in A549 cells. Our results show a differential proliferative and invasive response to AIR that is dependent on genetic subtype and independent of intrinsic radioresistance. Further examination of these findings in a larger panel of NSCLC cell lines and in pre-clinical models is warranted for identification of biomarkers of tumor response to AIR.

Double Trouble: A Case Series on Concomitant Genetic Aberrations in NSCLC

Several oncogenic drivers have been identified in non-small cell lung cancer. Targeted therapies for these aberrations have already been successfully developed and implemented in clinical practice. Owing to improved sensitivity in genetic testing, more and more tumors with multiple driver mutations are identified, resulting in dilemmas for treating physicians whether and which targeted therapy to use. In this case series, we provide an overview of patients with intrinsic double mutations in oncogenic drivers and their reported response to targeted therapies, with a focus on epidermal growth factor receptor, anaplastic lymphoma kinase, cMET, and Kirsten rat sarcoma viral oncogene. We also include an unpublished case report on a patient with an epidermal growth factor receptor L858R and cMET exon 14 skipping.

Better to be alone than in bad company: The antagonistic effect of cisplatin and crizotinib combination therapy in non-small cell lung cancer

AIM

To investigate the potential benefit of combining the cMET inhibitor crizotinib and cisplatin we performed in vitro combination studies.

METHODS

We tested three different treatment schemes in four non-small cell lung cancer (NSCLC) cell lines with a different cMET/epidermal growth factor receptor genetic background by means of the sulforhodamine B assay and performed analysis with Calcusyn.

RESULTS

All treatment schemes showed an antagonistic effect in all cell lines, independent of the cMET status. Despite their different genetic backgrounds, all cell lines (EBC-1, HCC827, H1975 and LUDLU-1) showed antagonistic combination indexes ranging from 1.3-2.7. These results were independent of the treatment schedule.

CONCLUSION

These results discourage further efforts to combine cMET inhibition with cisplatin chemotherapy in NSCLC.

cMET Exon 14 Skipping: From the Structure to the Clinic

The abnormal stimulation of the multiple signal transduction pathways downstream of the receptor tyrosine kinase mesenchymal-epithelial transition factor (cMET) promotes cellular transformation, tumor motility, and invasion. Therefore, cMET has been the focus of prognostic and therapeutic studies in different tumor types, including non-small cell lung cancer. In particular, several cMET inhibitors have been developed as innovative therapeutic candidates and are currently under investigation in clinical trials. However, one of the challenges in establishing effective targeted treatments against cMET remains the accurate identification of biomarkers for the selection of responsive subsets of patients. Recently, splice site mutations have been discovered in cMET that lead to the skipping of exon 14, impairing the breakdown of the receptor. Patients with NSCLC who are carrying this splice variant typically overexpress the cMET receptor and show a response to small molecule inhibitors of cMET. Here, we review the main differences at the structural level between the wild-type and the splice variants of cMET and their influence on cMET signaling. We clarify the reason why this variant responds to small molecule inhibitors and their prognostic/predictive role.

Hepatocyte growth factor and alternative splice variants - expression, regulation and implications in osteogenesis and bone health and repair

INTRODUCTION

Bone marrow-derived mesenchymal stem cells (MSCs) can differentiate into multiple cell types, including osteoblasts, chondrocytes, and adipocytes. These pluripotent cells secrete hepatocyte growth factor (HGF), which regulates cell growth, survival, motility, migration, mitogenesis and is important for tissue development/regeneration. HGF has four splice variants, NK1, NK2, NK3, and NK4 which have varying functions and affinities for the HGF receptor, cMET. HGF promotes osteoblastic differentiation of MSCs into bone forming cells, playing a role in bone development, health and repair.

AREAS COVERED

This review will focus on the effects of HGF in osteogenesis, bone repair and bone health, including structural and functional insights into the role of HGF in the body.

EXPERT OPINION

Approximately 6.2 million Americans experience a fracture annually, with 5-10% being mal- or non-union fractures. HGF is important in priming MSCs for osteogenic differentiation in vitro and is currently being studied to assess its role during bone repair in vivo. Due to the high turnover rate of systemic HGF, non-classic modes of HGF-treatment, including naked-plasmid HGF delivery and the use of HGF splice variants (NK1 & NK2) are being studied to find safe and efficacious treatments for bone disorders, such as mal- or non-union fractures.

cMET Activation and EGFR-Directed Therapy Resistance in Triple-Negative Breast Cancer

Background: EGFR expression and pathway activation are common in triple-negative breast cancer (TNBC). However, anti-EGFR therapies have not been effective in these patients. We aimed to study the efficacy of targeting MET in overcoming resistance to EGFR therapy in TNBC cell lines.

Methods: TNBC lines (MDA-MB-468, HCC-1395, and MDA-MB-231), and a hormone receptor-positive breast cancer line (T47D) were stimulated with epidermal growth factor (EGF) and hepatocyte growth factor (HGF). Lines were then treated with different concentrations of EGFR inhibitors (gefitinib or cetuximab), with or without a MET tyrosine kinase inhibitor (EMD 1214063). Proliferation was measured by MTS assay, in soft agar and with a matrigel assay. Synergy was measured with Calcusyn. Protein expression and signaling were examined with immunoblotting.

Results: There was activation of ligand-receptor-downstream signaling pathways in MDA-MB-468 and HCC-1395 upon stimulation with EGF and HGF. In these cell lines, we observed synergism when combining EGFR and MET inhibitors. These results were observed across assays. In western blotting, combination therapy resulted in abrogation of pAKT and pMAPK while monotherapy did not.

Conclusion: Our data demonstrate that dual EGFR/MET inhibition is synergistic in TNBC. Targeting both EGFR and MET receptors may provide an effective therapeutic strategy in TNBC.

Volitinib, a potent and highly selective c-Met inhibitor, effectively blocks c-Met signaling and growth in c-MET amplified gastric cancer patient-derived tumor xenograft models

PURPOSE

To investigate the incidence of cMET gene copy number changes and protein overexpression in Chinese gastric cancer (GC) and to preclinically test the hypothesis that the novel, potent and selective cMET small-molecule inhibitor volitinib, will deliver potent anti-tumor activity in cMET-dysregulated GC patient-derived tumor xenograft (PDX) models.

EXPERIMENTAL DESIGN

A range of assays were used and included; in vitro cell line panel screening and pharmacodynamic (PD) analysis, cMET fluorescence in-situ hybridization (FISH) and immunohistochemical (IHC) tissue microarray (TMA) analysis of Chinese GC (n = 170), and anti-tumor efficacy testing and PD analysis of gastric PDX models using volitinib.

RESULTS

The incidence of cMET gene amplification and protein overexpression within Chinese patient GC tumors was 6% and 13%, respectively. Volitinib displayed a highly selective profile across a gastric cell line panel, potently inhibiting cell growth only in those lines with dysregulated cMET (EC50 values 0.6 nM/L-12.5 nM/L). Volitinib treatment led to pharmacodynamic modulation of cMET signaling and potent tumor stasis in 3/3 cMET-dysregulated GC PDX models, but had negligible activity in a GC control model.

CONCLUSIONS

This study provides an assessment of tumor cMET gene copy number changes and protein overexpression incidence in a cohort of Chinese GC patients. To our knowledge, this is the first study to demonstrate anti-tumor efficacy in a panel of cMET-dysregulated gastric cancer PDX models, using a novel selective cMET-inhibitor (volitinib). Thus, the translational science presented here provides strong rationale for the investigation of volitinib as a therapeutic option for patients with GC tumors harboring amplified cMET.

cMET in triple-negative breast cancer: is it a therapeutic target for this subset of breast cancer patients?

INTRODUCTION

The identification and validation of a targeted therapy for triple-negative breast cancer (TNBC) is currently one of the most urgent needs in breast cancer therapeutics. The cMET oncogene encodes a membrane-bound tyrosine kinase implicated in the formation and/or progression of several cancer types, including TNBC. Currently, inhibitors targeting cMET are undergoing clinical trials for a variety of cancers, including TNBC. These include anti-cMET and anti-hepatocyte growth factor (HGF) monoclonal antibodies and tyrosine kinase inhibitors.

AREAS COVERED

This article reviews the structure and mode of action of cMET, the role of cMET in cancer formation/development, with particular emphasis on its role in basal/TNBC and its potential as a therapeutic target for this subtype of breast cancer.

EXPERT OPINION

Due to cancer heterogeneity, it is unlikely that all TNBC patients will be responsive to anti-cMET drugs. Therefore, if cMET is to be used as a target for treatment, it will be important to identify predictive biomarkers to select, upfront, those patients likely to benefit. Potential predictive biomarkers for anti-cMET treatments in basal/TNBC include cMET, phospho-cMET, downstream signaling proteins or HGF. These putative predictive biomarkers should be evaluated in a large panel of basal/TNBC cell lines before incorporation into clinical trials involving anti-cMET drugs.

Quantification of cell surface proteins with bispecific antibodies

Flow cytometry is an established method for fast and accurate quantitation of cellular protein levels and requires fluorescently labeled antibodies as well as calibration standards. A critical step for quantitation remains the production of suitable detection antibodies with a precisely defined ratio of antigen-binding sites to fluorophores. Problems often arise as a consequence of inefficient and unspecific labeling which can influence antibody properties. In addition, the number of incorporated fluorophores necessitates a special normalization step for quantitation. To address these problems, we constructed different mono- and bivalent bispecific antibodies with binding site(s) for the cell surface antigens, cMET, EGFR1/HER1, ErbB2/HER2 or ErbB3/HER3 and with an additional digoxigenin-binding single-chain Fv fusion. The fluorophore Cy5 was covalently coupled to digoxigenin and quantitatively bound by the bispecific antibody. A panel of tumor cell lines was assessed under different culture conditions for absolute receptor expression levels of the indicated antigens and the data were set in relation to mRNA, gene count and immunoblot data. We could reproducibly quantify these receptors, omit the otherwise required normalization step and demonstrate the superiority of a 1 + 1 bispecific antibody. The same antibodies were also used to quantify the number of proteins in intracellular vesicles in confocal microscopy. The antibodies can be stored like regular antibodies and can be coupled with different digoxigenin-labeled fluorophores which makes them excellent tools for FACS and imaging-based experiments.