MET gene amplification or EGFR mutation activate MET in lung cancers untreated with EGFR tyrosine kinase inhibitors

Knockdown of the epidermal growth factor receptor gene to investigate its therapeutic potential for the treatment of non-small-cell lung cancers

BACKGROUND

Epidermal growth factor receptor (EGFR) is often overexpressed in non-small-cell lung cancer (NSCLC). Anti-EGFR agents, including EGFR-tyrosine kinase inhibitors are considered to be effective when a drug-sensitive EGFR mutation is present. However, inherent and acquired resistances are major problems of EGFR-targeting therapies. In this study, we performed EGFR knockdown by using small interfering RNAs in NSCLC cell lines to examine the significance of targeting EGFR for NSCLC therapy.

METHODS

We treated 13 NSCLC cell lines, including 8 EGFR mutant and 5 EGFR wild type by using gefitinib or small interfering RNAs against EGFR (siEGFR). Three cell lines (PC-9-GR1, RPC-9, and HCC827-ER) were experimentally established with acquired resistance to EGFR-tyrosine kinase inhibitors. The antitumor effect was determined by using an 3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium, inner salt (MTS) or colony formation assay. The protein expression was evaluated by using Western blotting.

RESULTS

All 13 cell lines expressed EGFR protein, and siEGFR downregulated EGFR protein expression in all. The cell viability was suppressed by siEGFR in 6 of 8 EGFR-mutant cell lines (suppressed 57%-92% of control cells), including PC-9-GR1 and RPC-9. The NCI-H1650 and HCC827-ER harbored EGFR mutations but were not suppressed. Of note, PTEN (phosphatase and tensin homolog) was deleted in NCI-H1650, and c-MET was amplified in HCC827-ER. It was not suppressed in any of the EGFR wild-type cells except in the NCI-H411, in which EGFR is phosphorylated, which indicates its activation.

CONCLUSIONS

Analysis of the results indicated that EGFR can be a therapeutic target in NSCLCs with EGFR activation. In contrast, targeting EGFR is not appropriate for tumors in which EGFR is not activated, even if EGFR is expressed.

Clinical implications of high MET gene dosage in non-small cell lung cancer patients without previous tyrosine kinase inhibitor treatment

INTRODUCTION

Recently, two studies revealed that MET amplification was associated with secondary epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) resistance in non-small cell lung cancer (NSCLC) patients. But it remains uncertain whether MET amplification could be related to primary TKI resistance in NSCLC because of limited data.

MATERIALS AND METHODS

MET gene dosage of the tumor tissues from 208 NSCLC patients was investigated by real time quantitative polymerase chain reaction and compared with molecular and clinical features, including EGFR mutations, KRAS mutations, EGFR gene copy numbers, and patient survivals. Three copies were used as the cutoff. Among them, 25 patients were also evaluable for EGFR TKI responsiveness.

RESULTS

The proportion of high MET gene dosage was 10.58% (22/208) with higher incidence in squamous cell carcinoma (11.86%) and smokers (16.18%), although the differences with adenocarcinoma and nonsmokers were nonsignificant. Coexisting EGFR mutations were identified, and the incidence (8.54%) was similar to wild type (12.0%). High MET gene dosage was significantly associated with higher tumor stage (stage I + II versus stage III + IV; p = 0.0254) and prior chemotherapy for stage III + IV adenocarcinoma patients (35.71% versus 7.41%; p = 0.0145) but not correlated with primary TKI resistance. Among the 155 surgically resectable patients (stage I to IIIA), high MET gene dosage was significantly associated with shorter median survival (21.0 months versus 47.1 months; p = 0.042) by univariate analysis.

CONCLUSIONS

High MET gene dosage was not related to primary TKI resistance and the incidence was increased after chemotherapy, suggesting high MET gene dosage may also be related to chemotherapy resistance.

Molecular mechanisms contributing to resistance to tyrosine kinase-targeted therapy for non-small cell lung cancer

One of the most important pathways in non-small cell lung cancer (NSCLC) is the epidermal growth factor receptor (EGFR) pathway. This pathway affects several crucial processes in tumor development and progression, including tumor cell proliferation, apoptosis regulation, angiogenesis, and metastatic invasion. Targeting EGFR is currently being intensely explored. We are witnessing the development of a number of potential molecular-inhibiting treatments for application in clinical oncology. In the last decade, the tyrosine kinase (TK) domain of the EGFR was identified in NSCLC patients, and it has responded very well with a dramatic clinical improvement to TK inhibitors such are gefitinib and erlotinib. Unfortunately, there were primary and/or secondary resistance to these treatments, as shown by clinical trials. Subsequent molecular biology studies provided some explanations for the drug resistance phenomenon. The molecular mechanisms of resistance need to be clarified. An in-depth understanding of these targeted-therapy resistance may help us explore new strategies for overcoming or reversing the resistance to these inhibitors for the future of NSCLC treatment.

Activity of crizotinib (PF02341066), a dual mesenchymal-epithelial transition (MET) and anaplastic lymphoma kinase (ALK) inhibitor, in a non-small cell lung cancer patient with de novo MET amplification

Crizotinib is a dual MET and ALK inhibitor. Currently, clinical development of crizotinib is focused primarily on ALK rearranged non-small cell lung cancer (NSCLC). Here we report an NSCLC patient with de novo MET amplification but no ALK rearrangement who achieved a rapid and durable response to crizotinib indicating is also a bona fide MET inhibitor.

Co-existence of positive MET FISH status with EGFR mutations signifies poor prognosis in lung adenocarcinoma patients

MET, a receptor tyrosine kinase for hepatocyte growth factor, is associated with tumor progression and acquired resistance to epidermal growth factor tyrosine kinase inhibitors (EGFR-TKI). Therefore, MET gene alterations could be both prognostic and predictive. Fluorescence in situ hybridization (FISH) is one method for assessing gene alteration, but the frequency of positive cases varies due to a lack of standardized criteria. We evaluated MET gene copy number in lung adenocarcinoma and its association with clinicopathological characteristics. FISH was applied to evaluate high MET gene copy number and true amplification in 138 lung adenocarcinoma patients using two criteria: the Cappuzzo scoring system and PathVysion. MET positive cases according to the Cappuzzo scoring system evidenced both aneuploidy and true amplification, whereas PathVysion revealed only amplification. Proportion of MET FISH positive cases was 15% and 4% determined by the Cappuzzo system and PathVysion, respectively. PathVysion demonstrated higher frequencies of MET FISH positives among men and smokers and evidenced no MET FISH positives in patients with bronchioloalveolar carcinoma. Prognosis was significantly associated with MET FISH positive only as defined by the PathVysion system (gene amplification), not by the Cappuzzo system. However, progression-free survival time of patients with both EGFR mutations and MET FISH positive defined by the Cappuzzo scoring system was significantly shorter than with EGFR mutations alone. These results suggest that MET FISH is a potential prognostic factor and coexistence of MET FISH with EGFR mutations signifies worse prognosis.

Mechanisms of resistance to EGFR TKIs and development of a new generation of drugs in non-small-cell lung cancer

Gefitinib and erlotinib, which are epidermal growth factor receptor- (EGFR-) specific tyrosine kinase inhibitors (TKIs), are widely used as molecularly targeted drugs for non-small-cell lung cancer (NSCLC). Currently, the search for EGFR gene mutations is becoming essential for the treatment of NSCLC since these have been identified as predictive factors for drug sensitivity. On the other hand, in almost all patients responsive to EGFR-TKIs, acquired resistance is a major clinical problem. Mechanisms of acquired resistance reported in the past few years include secondary mutation of the EGFR gene, amplification of the MET gene, and overexpression of HGF; novel pharmaceutical agents are currently being developed to overcome resistance. This review focuses on these mechanisms of acquired resistance to EGFR-TKIs and discusses how they can be overcome.

Molecular profiles of EGFR, K-ras, c-met, and FGFR in pulmonary pleomorphic carcinoma, a rare lung malignancy

BACKGROUND

Pulmonary pleomorphic carcinoma (PPC) is a rare type of lung cancer characterized by the poor response to conventional chemotherapy and subsequent disappointing outcomes. Therefore, it is paramount to delineate the molecular characteristics of this disease entity.

METHODS

In this study, we retrospectively examined the surgical specimens of 61 patients who underwent lung surgery. Mutational or gene amplification statuses of epidermal growth factor receptor (EGFR), k-ras, c-kit, c-met, and fibroblast growth factor receptor (FGFR) were examined using genomic DNA sequencing, real-time PCR and/or fluorescence in situ hybridization (FISH).

RESULTS

The median age was 61 years, and 50 patients were men and 11 were women. In the histologic review of epithelial component, adenocarcinoma were in 44 cases (72%), squamous cell carcinoma in 15 (25%) and large cell carcinoma in 2 patients (3%). Overall, 30 cases (49%) had any molecular alterations. Nine patients (15%) possessed EGFR deletion in exon 19 (n = 8) or L858R mutations in exon 21 (n = 1), while 3 other cases having atypical EGFR mutations. Six patients (9.8%) had k-ras mutations in exon 12, and 3 had c-kit mutations. High gene copy number of c-met was found in 11 patients (18.0%) and that of FGFR was in 6 patients (9.8%). No significant relationships were identified among the occurrence and type of mutations and patient survival or any other clinicopathological variables.

CONCLUSIONS

Given the diverse repertoire of mutational profiles observed in PPC samples, clinical trials based on accurate cancer-genotyping should be considered as a legitimate treatment scheme for this rare disease entity in the future.

Establishment and characterization of primary lung cancer cell lines from Chinese population

AIM

To establish and characterize primary lung cancer cell lines from Chinese population.

METHODS

Lung cancer specimens or pleural effusions were collected from Chinese lung cancer patients and cultured in vitro with ACL4 medium (for non-small cell lung carcinomas (NSCLC)) or HITES medium (for small cell lung carcinomas (SCLC)) supplemented with 5% FBS. All cell lines were maintained in culture for more than 25 passages. Most of these cell lines were further analyzed for oncogenic mutations, karyotype, cell growth kinetics, and tumorigenicity in nude mice.

RESULTS

Eight primary cell lines from Chinese lung cancer patients were established and characterized, including seven NSCLC cell lines and one SCLC cell line. Five NSCLC cell lines were found to harbor epidermal growth factor receptor (EGFR) kinase domain mutations.

CONCLUSION

These well-characterized primary lung cancer cell lines from Chinese population provide a unique platform for future studies of the ethnic differences in lung cancer biology and drug response.

Reciprocal and complementary role of MET amplification and EGFR T790M mutation in acquired resistance to kinase inhibitors in lung cancer

PURPOSE

In epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) therapy for lung cancer patients, acquired resistance develops almost inevitably and this limits the improvement in patient outcomes. EGFR T790M mutation and MET amplification are the two main mechanisms underlying this resistance, but the relationship between these two mechanisms is unclear. In this study, we explored their relationship using in vitro models and autopsy specimens.

EXPERIMENTAL DESIGN

Erlotinib-resistant HCC827 (HCC827ER) cells were developed by chronic exposure to erlotinib at increasing concentrations. HCC827EPR cells were also developed by chronic exposure to erlotinib in the presence of PHA-665,752 (a MET TKI). The erlotinib-resistant mechanisms of these cells were analyzed. In addition, 33 autopsy tumor samples from 6 lung adenocarcinoma patients harboring multiple gefitinib-refractory tumors were analyzed.

RESULTS

HCC827ER developed MET amplification, and clinically relevant resistance occurred at ≥4-fold MET gene copy number gain (CNG). By contrast, HCC827EPR developed T790M without MET CNG. Of six patients harboring gefitinib-refractory tumors, three exhibited T790M only, one exhibited MET amplification only, and the other two exhibited T790M and/or MET amplification depending on the lesion sites. In these gefitinib-refractory tumors, T790M developed in 93% (14 of 15) of tumors without MET gene CNGs, in 80% (4 of 5) of tumors with moderate MET gene CNGs (<4-fold), and in only 8% (1 of 13) of tumors with MET amplification (≥4-fold).

CONCLUSIONS

These results indicate a reciprocal and complementary relationship between T790M and MET amplification and the necessity of concurrent inhibition of both for further improving patient outcomes.

Novel agents in the treatment of metastatic colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer death in the United States. Research has led to an explosion of knowledge into the molecular basis of CRC in the past decades. Numerous receptors and intracellular proteins have been identified and implicated in the growth and progression of metastatic CRC, thus creating novel targets for drug development. Many agents are under development and have begun to enter early and even later-stage clinical trials. Results of these agents have demonstrated some encouraging activity but in a small number of patients. Research into predictive biomarkers aims to select the patients who may benefit from these novel agents. This review will address several of these promising new agents, their potential relevance to CRC, results from early clinical studies, and their incorporation into future and ongoing CRC clinical trials. Clearly, there is an urgent need for new agents in this disease, but as we learned from the experience with epidermal growth factor receptor-targeted antibodies, patient selection will be increasingly be required for individualized therapy to become a reality in CRC.

Targeted therapy in non-small-cell lung cancer--is it becoming a reality?

Treatment outcomes in advanced or metastatic non-small-cell lung cancer (NSCLC) remain unsatisfactory, with low long-term survival rates. Palliative chemotherapy offers a median survival not exceeding 1 year. To date, various combinations of cytotoxic drugs have not improved treatment results beyond what has been observed with platinum doublets. By contrast, molecular targeted drugs may block important pathways that drive cancer progression and achieve long-term disease control. Conflicting results have demonstrated marginal benefit with EGFR inhibitors, anti-EGFR monoclonal antibodies and antiangiogenic strategies in unselected populations of patients with advanced NSCLC. However, patients with an EGFR mutation are likely to respond to agents that target this gene. Novel targeted therapies that interfere with insulin-like growth factor 1 receptor, or the EML4-ALK fusion protein have shown promising activity. Aberrations in other key signaling pathways and molecules, such as RAS/RAF/MEK, PI3K/AKT/mTOR, or MET kinase, have been identified as crucial targets, especially in resistant patients. Novel drugs aimed at these abnormalities are already in the clinic. This Review outlines the current state-of-the-art research for targeted therapy in NSCLC.

High MET gene copy number leads to shorter survival in patients with non-small cell lung cancer

INTRODUCTION

Activation of MET, either by increased gene copy number (GCN) or mutation, has been detected in various cancers. We investigate the clinicopathologic features of MET gene copy in nonsmall cell lung cancer (NSCLC).

METHODS

Tumor tissues were obtained from 180 resected NSCLCs, including 97 squamous cell carcinomas (SCCs) and 72 adenocarcinomas. No patient received epidermal growth factor receptor (EGFR)-targeted therapy. EGFR and MET GCNs were studied using fluorescence in situ hybridization (FISH) and were estimated according to the University of Colorado Cancer Center (UCCC) criteria. For MET, we also assessed GCNs using the Cappuzzo system.

RESULTS

FISH-positive MET was observed in 16.7% using the UCCC criteria; specifically, amplification was seen in 3.9% and high polysomy in 12.8%. FISH-positive MET status was significantly correlated with FISH-positive EGFR (p = 0.003). In the Cappuzzo system, high MET GCN (mean, >/=5 copies/cell) was found in 6.7% and also associated with FISH-positive EGFR (p = 0.031). MET gene copy status was not associated with gender, smoking history, histology, or stage. However, true MET amplification was more frequent in patients with SCC than in those with adenocarcinoma. FISH-positive MET status predicted worse survival in patients with NSCLC at advanced stages (p = 0.034) and in patients with SCC (p = 0.028). In multivariate analyses, increased MET GCN was significantly associated with shorter survival in patients with SCC, as analyzed using both the UCCC and Cappuzzo criteria (p = 0.019 and 0.008).

CONCLUSIONS

Our results suggest that increased MET GCN would be an independent poor prognostic factor in SCC of the lung.

Clinical implications of MET gene copy number in lung cancer

MET, the receptor for HGF, has recently been identified as a novel promising target in several human malignancies, including non-small-cell lung cancer (NSCLC). Deregulation of the HGF/MET signaling pathway can occur via different mechanisms, including HGF and/or MET overexpression, MET gene amplification, mutations or rearrangements. While the role of MET mutations in NSCLC is not yet fully understood, MET amplification emerged as a critical event in driving cell survival, with preclinical data suggesting that MET-amplified cell lines are exquisitely sensitive to MET inhibition. True MET amplification, which has been associated with poor prognosis in different retrospective series, is a relatively uncommon event in NSCLC, occurring in 1-7% of unselected cases. Nevertheless, in highly selected cohorts of patients, such as those harboring somatic mutations of the EGF receptor (EGFR) with acquired resistance to EGFR tyrosine kinase inhibitors (TKIs), MET amplification can be observed in up to 20% of cases. Preclinical data suggested that a treatment approach including a combination of EGFR and MET TKIs could be an effective strategy in this setting and led to the clinical investigation of multiple MET TKIs in combination with erlotinib. Results from ongoing and future trials will clarify the role of MET TKIs for the treatment of NSCLC and will provide insights into the most appropriate timing for their use.

Hepatocyte growth factor reduces susceptibility to an irreversible epidermal growth factor receptor inhibitor in EGFR-T790M mutant lung cancer

PURPOSE

The secondary T790M mutation in epidermal growth factor receptor (EGFR) is the most frequent cause of acquired resistance to the reversible EGFR tyrosine kinase inhibitors (EGFR-TKI), gefitinib and erlotinib, in lung cancer. Irreversible EGFR-TKIs are expected to overcome the reversible EGFR-TKI resistance of lung cancer harboring T790M mutation in EGFR. However, it is clear that resistance may also develop to this class of inhibitors. We showed previously that hepatocyte growth factor (HGF) induced gefitinib resistance of lung cancer harboring EGFR-activating mutations. Here, we investigated whether HGF induced resistance to the irreversible EGFR-TKI, CL-387,785, in lung cancer cells (H1975) harboring both L858R activating mutation and T790M secondary mutation in EGFR.

EXPERIMENTAL DESIGN

CL-387,785 sensitivity and signal transduction in H1975 cells were examined in the presence or absence of HGF or HGF-producing fibroblasts with or without HGF-MET inhibitors.

RESULTS

HGF reduced susceptibility to CL-387,785 in H1975 cells. Western blotting and small interfering RNA analyses indicated that HGF-induced hyposensitivity was mediated by the MET/phosphoinositide 3-kinase/Akt signaling pathway independent of EGFR, ErbB2, ErbB3, and ErbB4. Hyposensitivity of H1975 cells to CL-387,785 was also induced by coculture with high-level HGF-producing lung fibroblasts. The hyposensitivity was abrogated by treatment with anti-HGF neutralizing antibody, HGF antagonist NK4, or MET-TKI.

CONCLUSIONS

We showed HGF-mediated hyposensitivity as a novel mechanism of resistance to irreversible EGFR-TKIs. It will be clinically valuable to investigate the involvement of HGF-MET-mediated signaling in de novo and acquired resistance to irreversible EGFR-TKIs in lung cancer harboring T790M mutation in EGFR.

Multiple pathways in the FGF signaling network are frequently deregulated by gene amplification in oral dysplasias

Genetic alteration in oral premalignant lesions (OPLs), the precursors of oral squamous cell carcinomas (OSCCs), may represent key changes in disease initiation and development. We ask if DNA amplification occurs at this early stage of cancer development and which oncogenic pathways are disrupted in OPLs. Here, we evaluated 50 high-grade dysplasias and low-grade dysplasias that later progressed to cancer for gene dosage aberrations using tiling-path DNA microarrays. Early occurrences of DNA amplification and homozygous deletion were frequently detected, with 40% (20/50) of these early lesions exhibiting such features. Expression for 88 genes in 7 recurrent amplicons were evaluated in 5 independent head and neck cancer datasets, with 40 candidates found to be overexpressed relative to normal tissues. These genes were significantly enriched in the canonical ERK/MAPK, FGF, p53, PTEN and PI3K/AKT signaling pathways (p = 8.95 x 10(-3) to 3.18 x 10(-2)). These identified pathways share interactions in one signaling network, and amplification-mediated deregulation of this network was found in 30.0% of these preinvasive lesions. No such alterations were found in 14 low-grade dysplasias that did not progress, whereas 43.5% (10/23) of OSCCs were found to have altered genes within the pathways with DNA amplification. Multitarget FISH showed that amplification of EGFR and CCND1 can coexist in single cells of an oral dysplasia, suggesting the dependence on multiple oncogenes for OPL progression. Taken together, these findings identify a critical biological network that is frequently disrupted in high-risk OPLs, with different specific genes disrupted in different individuals.