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

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.

Genome-wide association between single nucleotide polymorphisms with beef fatty acid profile in Nellore cattle using the single step procedure

Background

Saturated fatty acids can be detrimental to human health and have received considerable attention in recent years. Several studies using taurine breeds showed the existence of genetic variability and thus the possibility of genetic improvement of the fatty acid profile in beef. This study identified the regions of the genome associated with saturated, mono- and polyunsaturated fatty acids, and n-6 to n-3 ratios in the Longissimus thoracis of Nellore finished in feedlot, using the single-step method.

Results

The results showed that 115 windows explain more than 1 % of the additive genetic variance for the 22 studied fatty acids. Thirty-one genomic regions that explain more than 1 % of the additive genetic variance were observed for total saturated fatty acids, C12:0, C14:0, C16:0 and C18:0. Nineteen genomic regions, distributed in sixteen different chromosomes accounted for more than 1 % of the additive genetic variance for the monounsaturated fatty acids, such as the sum of monounsaturated fatty acids, C14:1 cis-9, C18:1 trans-11, C18:1 cis-9, and C18:1 trans-9. Forty genomic regions explained more than 1 % of the additive variance for the polyunsaturated fatty acids group, which are related to the total polyunsaturated fatty acids, C20:4 n-6, C18:2 cis-9 cis12 n-6, C18:3 n-3, C18:3 n-6, C22:6 n-3 and C20:3 n-6 cis-8 cis-11 cis-14. Twenty-one genomic regions accounted for more than 1 % of the genetic variance for the group of omega-3, omega-6 and the n-6:n-3 ratio.

Conclusions

The identification of such regions and the respective candidate genes, such as ELOVL5, ESSRG, PCYT1A and genes of the ABC group (ABC5, ABC6 and ABC10), should contribute to form a genetic basis of the fatty acid profile of Nellore (Bos indicus) beef, contributing to better selection of the traits associated with improving human health.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2511-y) contains supplementary material, which is available to authorized users.

The pan-HDAC inhibitor panobinostat acts as a sensitizer for erlotinib activity in EGFR-mutated and -wildtype non-small cell lung cancer cells

BACKGROUND

The receptor tyrosine kinase (RTK) EGFR is overexpressed and mutated in NSCLC. These mutations can be targeted by RTK inhibitors (TKIs) such as erlotinib. Chromatin-modifying agents may offer a novel therapeutic approach by sensitizing tumor cells to TKIs.

METHODS

The NSCLC cell lines HCC827 (EGFR mutant, adenocarcinoma), A549 (EGFR wt, adenocarcinoma) and NCI-H460 (EGFR wt, large cell carcinoma) were analyzed by SNP6.0 array. Changes in proliferation after panobinostat (LBH-589, PS) and erlotinib treatment were quantified by WST-1 assay and apoptosis by Annexin V/7-AAD flow cytometry. Abundance of target proteins and histone marks (acH3, H3K4me1/2/3) was determined by immunoblotting.

RESULTS

As expected, the EGFR wt cell lines A549 and NCI-H460 were quite insensitive to the growth-inhibitory effect of erlotinib (IC50 70-100 μM), compared to HCC827 (IC50<0.02 μM). All three cell lines were sensitive to PS treatment (IC50: HCC827 10 nM, A549 20 nM and NCI-H460 35 nM). The combination of both drugs further reduced proliferation in HCC827 and in A549, but not in NCI-H460. PS alone induced differentiation and expression of p21WAF1/CIP1 and p53 and decreased CHK1 in all three cell lines, with almost no further effect when combined with erlotinib. In contrast, combination treatment additively decreased pEGFR, pERK and pAKT in A549. Both drugs synergistically induced acH3 in the adenocarcinoma lines. Surprisingly, we also observed induction of H3K4 methylation marks after erlotinib treatment in HCC827 and in A549 that was further enhanced by combination with PS.

CONCLUSION

PS sensitized lung adenocarcinoma cells to the antiproliferative effects of erlotinib. In these cell lines, the drug combination also had a robust, not previously described effect on histone H3 acetylation and H3K4 methylation.

Antitumor effect of afatinib, as a human epidermal growth factor receptor 2-targeted therapy, in lung cancers harboring HER2 oncogene alterations

Human epidermal growth factor receptor 2 (HER2) is a member of the HER family of proteins containing four receptor tyrosine kinases. It plays an important role in the pathogenesis of certain human cancers. In non-small-cell lung cancer (NSCLC), HER2 amplification or mutations have been reported. However, little is known about the benefit of HER2-targeted therapy for NSCLCs harboring HER2 alterations. In this study, we investigated the antitumor effect of afatinib, an irreversible epidermal growth factor receptor (EGFR)-HER2 dual inhibitor, in lung cancers harboring HER2 oncogene alterations, including novel HER2 mutations in the transmembrane domain, which we recently identified. Normal bronchial epithelial cells, BEAS-2B, ectopically overexpressing wild-type HER2 or mutants (A775insYVMA, G776VC, G776LC, P780insGSP, V659E, and G660D) showed constitutive autophosphorylation of HER2 and activation of downstream signaling. They were sensitive to afatinib, but insensitive to gefitinib. Furthermore, we examined the antitumor activity of afatinib and gefitinib in several NSCLC cell lines, and investigated the association between their genetic alterations and sensitivity to afatinib treatment. In HER2-altered NSCLC cells (H2170, Calu-3, and H1781), afatinib downregulated the phosphorylation of HER2 and EGFR as well as their downstream signaling, and induced an antiproliferative effect through G1 arrest and apoptotic cell death. In contrast, HER2- or EGFR-non-dependent NSCLC cells were insensitive to afatinib. In addition, these effects were confirmed in vivo by using a xenograft mouse model of HER2-altered lung cancer cells. Our results suggest that afatinib is a therapeutic option as a HER2-targeted therapy for NSCLC harboring HER2 amplification or mutations.

Responses to the multitargeted MET/ALK/ROS1 inhibitor crizotinib and co-occurring mutations in lung adenocarcinomas with MET amplification or MET exon 14 skipping mutation

INTRODUCTION

Genomic aberrations involving ALK, ROS1 and MET can be driver oncogenes in lung adenocarcinomas. Identification of tyrosine kinase inhibitors (TKIs) with activity against these tumors and of preclinical systems to model response are warranted.

METHODS

We analyzed cases with lung adenocarcinomas for representative genomic aberrations, evaluated the response to the multitargeted MET/ALK/ROS1 crizotinib TKI in cases with MET aberrations and profiled lung cancer cell lines with the aforementioned genomic changes.

RESULTS

Lung cancer cell lines with ALK rearrangement, ROS1 rearrangement or MET amplification had expected in vitro responses to crizotinib and the ALK/ROS1 TKI ceritinib. However, a commercially-available cell line with MET exon 14 skipping mutation and co-occurring PIK3CA-p.Glu545Lys mutation did not respond to crizotinib; suggesting the latter abrogated response. 10% of MET exon 14 skipping mutation co-occurred with PIK3CA mutation in the TCGA cohort. Putative crizotinib-responsive somatic mutations (ALK rearrangements, ROS1 rearrangements, high level MET amplification or MET exon 14 skipping mutations) were present in 10% of lung adenocarcinomas analyzed at our service and in 9.5% of the TCGA lung adenocarcinoma database. One patient each whose advanced tumors harbored high level MET amplification with wild-type PIK3CA or MET exon 14 skipping mutation with PIK3CA-p.Glu542Lys had significant responses to crizotinib; suggesting that PIK3CA co-mutation did not affect clinical response.

CONCLUSIONS

Approximately 10% of lung adenocarcinomas harbor aberrations that are targetable using the approved multitargeted TKI crizotinib. MET exon 14 skipping mutation predicts for response to MET TKIs in human lung adenocarcinomas but co-occurrence of PIK3CA mutation needs to be better evaluated as a modifier of response to TKI therapy. MET TKIs should not be omitted from MET exon 14 skipping mutated tumors until further preclinical and clinical data can confirm or refute mechanisms of primary or acquired resistance to crizotinib and other MET TKIs in these recalcitrant cancers.

Integrative Genomics Implicates EGFR as a Downstream Mediator in NKX2-1 Amplified Non-Small Cell Lung Cancer

NKX2-1, encoding a homeobox transcription factor, is amplified in approximately 15% of non-small cell lung cancers (NSCLC), where it is thought to drive cancer cell proliferation and survival. However, its mechanism of action remains largely unknown. To identify relevant downstream transcriptional targets, here we carried out a combined NKX2-1 transcriptome (NKX2-1 knockdown followed by RNAseq) and cistrome (NKX2-1 binding sites by ChIPseq) analysis in four NKX2-1-amplified human NSCLC cell lines. While NKX2-1 regulated genes differed among the four cell lines assayed, cell proliferation emerged as a common theme. Moreover, in 3 of the 4 cell lines, epidermal growth factor receptor (EGFR) was among the top NKX2-1 upregulated targets, which we confirmed at the protein level by western blot. Interestingly, EGFR knockdown led to upregulation of NKX2-1, suggesting a negative feedback loop. Consistent with this finding, combined knockdown of NKX2-1 and EGFR in NCI-H1819 lung cancer cells reduced cell proliferation (as well as MAP-kinase and PI3-kinase signaling) more than knockdown of either alone. Likewise, NKX2-1 knockdown enhanced the growth-inhibitory effect of the EGFR-inhibitor erlotinib. Taken together, our findings implicate EGFR as a downstream effector of NKX2-1 in NKX2-1 amplified NSCLC, with possible clinical implications, and provide a rich dataset for investigating additional mediators of NKX2-1 driven oncogenesis.

Analytical and Clinical Validation of a Digital Sequencing Panel for Quantitative, Highly Accurate Evaluation of Cell-Free Circulating Tumor DNA

Next-generation sequencing of cell-free circulating solid tumor DNA addresses two challenges in contemporary cancer care. First this method of massively parallel and deep sequencing enables assessment of a comprehensive panel of genomic targets from a single sample, and second, it obviates the need for repeat invasive tissue biopsies. Digital Sequencing^TM is a novel method for high-quality sequencing of circulating tumor DNA simultaneously across a comprehensive panel of over 50 cancer-related genes with a simple blood test. Here we report the analytic and clinical validation of the gene panel. Analytic sensitivity down to 0.1% mutant allele fraction is demonstrated via serial dilution studies of known samples. Near-perfect analytic specificity (> 99.9999%) enables complete coverage of many genes without the false positives typically seen with traditional sequencing assays at mutant allele frequencies or fractions below 5%. We compared digital sequencing of plasma-derived cell-free DNA to tissue-based sequencing on 165 consecutive matched samples from five outside centers in patients with stage III-IV solid tumor cancers. Clinical sensitivity of plasma-derived NGS was 85.0%, comparable to 80.7% sensitivity for tissue. The assay success rate on 1,000 consecutive samples in clinical practice was 99.8%. Digital sequencing of plasma-derived DNA is indicated in advanced cancer patients to prevent repeated invasive biopsies when the initial biopsy is inadequate, unobtainable for genomic testing, or uninformative, or when the patient’s cancer has progressed despite treatment. Its clinical utility is derived from reduction in the costs, complications and delays associated with invasive tissue biopsies for genomic testing.

Mechanisms of resistance to EGFR tyrosine kinase inhibitors

Since the discovery that non-small cell lung cancer (NSCLC) is driven by epidermal growth factor receptor (EGFR) mutations, the EGFR tyrosine kinase inhibitors (EGFR-TKIs, e.g., gefitinib and elrotinib) have been effectively used for clinical treatment. However, patients eventually develop drug resistance. Resistance to EGFR-TKIs is inevitable due to various mechanisms, such as the secondary mutation (T790M), activation of alternative pathways (c-Met, HGF, AXL), aberrance of the downstream pathways (K-RAS mutations, loss of PTEN), impairment of the EGFR-TKIs-mediated apoptosis pathway (BCL2-like 11/BIM deletion polymorphism), histologic transformation, ATP binding cassette (ABC) transporter effusion, etc. Here we review and summarize the known resistant mechanisms to EGFR-TKIs and provide potential targets for development of new therapeutic strategies.

Long non-coding RNA: A new paradigm for lung cancer

Lung cancer is the leading cause of cancer-related deaths worldwide. Recent advances in whole genome transcriptome analysis have enabled the identification of numerous members of a novel class of non-coding RNAs, i.e., long non-coding RNAs (lncRNAs), which play important roles in a wide range of biological processes and whose deregulation causes human disease, including cancer. Herein we provide a comprehensive survey of lncRNAs associated with lung cancer, with particular focus on the functions that either facilitate or inhibit the progression of lung cancer and the pathways involved. Emerging data on the use of lncRNAs as biomarkers for the diagnosis and prognosis of cancer are also discussed. We cast this information within the wider perspective of lncRNA biogenesis and molecular functions in the cell. Relationships that exist between lncRNAs, genome-wide transcription, and lung cancer are discussed. Deepening our understanding on these processes is critical not only from a mechanistic standpoint, but also for the development of novel biomarkers and effective therapeutic targets for cancer patients.

DNA copy number gains in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a highly aggressive tumor with an extremely poor prognosis. The incidence of MPM is increasing as a result of widespread exposure to asbestos. The molecular pathogenesis of MPM remains unclear. The present study analyzed the frequency of various genomic copy number gains (CNGs) in MPM using reverse transcription-quantitative polymerase chain reaction. A total of 83 primary MPMs and 53 primary lung adenocarcinomas were analyzed to compare the CNGs of EGFR, KRAS, MET, FGFR1 and SOX2. In MPM, the CNGs of EGFR, KRAS, MET, FGFR1 and SOX2 were detected in 12 (14.5%), 8 (9.6%), 5 (6.0%), 4 (4.8%) and 1 (1.2%) of the samples, respectively. In lung adenocarcinomas, the CNGs of EGFR, KRAS, MET, FGFR1 and SOX2 were detected in 21 (39.6%), 12 (22.6%), 5 (9.4%), 10 (18.9%) and 0 (0.0%) of the samples, respectively. The CNGs of EGFR, KRAS and FGFR1 were significantly less frequent in the MPMs compared with the lung adenocarcinomas (P=0.0018, 0.048 and 0.018, respectively). Overall, the MPMs exhibited these CNGs less frequently compared with the lung adenocarcinomas (P=0.0002). The differences in CNGs between the two tumor types suggested that they are genetically different.

Reversal of Warburg Effect and Reactivation of Oxidative Phosphorylation by Differential Inhibition of EGFR Signaling Pathways in Non-Small Cell Lung Cancer

PURPOSE

One of the hallmarks of cancer cells is the excessive conversion of glucose to lactate under normoxic conditions, also known as the Warburg effect. Here, we tested whether the targeted inhibition of EGFR may revert this effect and reactivate mitochondrial oxidative phosphorylation in non-small cell lung cancer (NSCLC).

EXPERIMENTAL DESIGN

Sensitive (HCC827) and resistant (H1975 and H1993) NSCLC cells were treated with a panel of EGFR or MET inhibitors, and then tested for changes of EGFR signaling, glycolytic cascade, and mitochondrial function. Silencing of key glycolytic enzymes was then performed with targeted siRNAs. Furthermore, tumor-bearing nude mice treated with EGFR inhibitors were evaluated with (18)F-FDG PET/CT and tumors were analyzed for glycolytic and mitochondrial proteins.

RESULTS

Effective inhibition of EGFR signaling in NSCLC cells induced a dramatic reduction of hexokinase II (HKII) and phospho-pyruvate kinase M2 (p-PKM2, Tyr105) levels as well as an upregulation of mitochondrial complexes subunits (OXPHOS). Accordingly, a decreased lactate secretion and increased intracellular ATP levels were also observed in response to EGFR inhibitors. Downregulation of HKII and PKM2 by targeted siRNA transfection did not cause upregulation of OXPHOS but enhanced the effects of EGFR TKIs. Conversely, selective inhibition of AKT and ERK1/2 caused OXPHOS upregulation and glycolysis inhibition, respectively. Similar findings were obtained in tumors from animals treated with appropriate EGFR inhibitors.

CONCLUSIONS

Our findings indicate that EGFR inhibitors may reactivate oxidative phosphorylation of cancer cells and provide a mechanistic clue for the rational combination of agents targeting EGFR-dependent proliferation and glucose metabolism in cancer therapy.

Comprehensive Molecular Analysis of NSCLC; Clinicopathological Associations

BACKGROUND

Selection of NSCLC patients for targeted therapy is currently based upon the presence of sensitizing mutations in EGFR and EML4/ALK translocations. The heterogeneity of molecular alterations in lung cancer has led to the ongoing discovery of potential biomarkers and targets in order to improve survival.

AIM

This study aimed to detect alterations in EGFR, KRAS, BRAF, PIK3CA, MET-gene copy number and ALK rearrangements in a large cohort of 956 NSCLC patients of Hellenic origin using highly sensitive techniques and correlations with clinicopathological characteristics.

RESULTS

Mutations were detected in EGFR 10.6% (101 out of 956 samples), KRAS 26.5% (191 out of 720 samples), BRAF 2.5% (12 out of 471 samples), PIK3CA 3.8% (7 out of 184 samples), MET gene amplification was detected in 18% (31 out of 170) and ALK rearrangements in 3.7% (4 out of 107 samples). EGFR mutations were detected in exon 19 (61.4% of mutant cases), exon 21 p.Leu858Arg (19.8%), exon 20 (15.8%), exon 18 (2.9%) and were correlated with gender histology, smoking status and TTF1 staining. p.Thr790Met mutant cases (3.9%) displayed concurrent mutations in exons 19 or 21. Negative TTF-1 staining showed strong negative predictive value for the presence of EGFR mutations. KRAS mutations were associated with histology, the most common mutation being p.Gly12Cys (38%).

DISCUSSION

In conclusion, only 89 patients were eligible for EGFR -TKIs and ALK inhibitors therapy, whereas 257 patients showed other alterations, highlighting the necessity for a detailed molecular profiling potentially leading to more efficient individualized therapies for NSCLC patients.

Dysregulation of the Met pathway in non-small cell lung cancer: implications for drug targeting and resistance

The receptor tyrosine kinase, Met, orchestrates a complex signalling network that physiologically drives a programme of 'invasive growth'. In cancer however, this process may be co-opted to promote proliferation, survival and metastasis of cancer cells. Met is thus a key therapeutic target, not least in non-small cell lung cancer (NSCLC) where it is one of the most commonly dysregulated driver oncogenes. Identifying robust biomarkers that allow the selection of patients most likely to respond to Met targeted therapies will however be essential to realising their potential. This has been underlined recently by the early termination of three pivotal phase III trials investigating Met targeted agents in NSCLC, all of which failed to show clinical benefit. In contrast to these trials, which were relatively unselective, a couple of early phase trials have recently been instigated that select patients on the basis of Met amplification. While still at an early stage, interim results are relatively encouraging and strengthen the rationale for using Met amplifaction as a biomarker. Here we will discuss this and other aberrations in Met signalling in relation to their significance in the therapeutic targeting of Met.

NVP-BEZ235 overcomes gefitinib-acquired resistance by down-regulating PI3K/AKT/mTOR phosphorylation

Background

Patients harboring activating mutations in epidermal growth factor receptors (EGFR) are particularly sensitive to EGFR tyrosine kinase inhibitors (TKIs). However, most patients develop an acquired resistance after a period of about 10 months. This study focuses on the therapeutic effect of NVP-BEZ235, a dual inhibitor of phosphatidylinositol-3-kinase/mammalian target of rapamycin (PI3K/mTOR), in gefitinib-resistant non-small cell lung cancer.

Methods

H1975 cell line was validated as a gefitinib-resistant cell model by the nucleotide-sequence analysis. We used the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to detect the growth of H1975 cell line in vitro. H1975 cells’ migration was detected by the migration assay. Xenograft models were used to investigate the growth of gefitinib-resistant non-small cell lung cancer in vivo. Western blot and immunohistochemical analysis were used to investigate the level of PI3K/protein kinase B(AKT)/mTOR signaling pathway proteins.

Results

We show that NVP-BEZ235 effectively inhibited the growth of H1975 cells in vivo as well as in vitro. Similarly, H1975 cell migration was reduced by NVP-BEZ235. Further experiments revealed that NVP-BEZ235 attenuated the phosphorylation of PI3K/AKT/mTOR signaling pathway proteins.

Conclusion

Taken together, we suggest that NVP-BEZ235 inhibits gefitinib-resistant tumor growth by downregulating PI3K/AKT/mTOR phosphorylation.

MET expression plays differing roles in non-small-cell lung cancer patients with or without EGFR mutation

INTRODUCTION

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors and Met inhibitors have enabled progress in the management of advanced non-small-cell lung cancer (NSCLC). However, the clinical benefits of these agents are not uniform across the NSCLC spectrum. Thus, we evaluated the prognostic effect of mesenchymal-epithelial transition (MET) expression in Asian NSCLC patients with or without EGFR mutation.

METHODS

Frozen tumor tissues were collected from 92 patients with surgical resection and 10 with lymph node biopsy. Mutations in exons 18-21 in the EGFR-tyrosine kinase domain and MET expression were analyzed by using sequencing and immunohistochemistry, respectively.

RESULTS

The MET overexpression rate was 51% in NSCLC patients. MET-positive patients had poorer overall survival than MET-negative patients (29.8 versus 69.1 months, χ = 7.420, p = 0.006) in patients with wild-type EGFR. However, no statistically significant difference was found in EGFR mutant patients (35.0 versus 35.9 months, χ = 0.114, p = 0.735). Multivariate analysis showed that stage, MET expression, and sex were independent prognostic factors in patients with wild-type EGFR (χ = 32.896, p < 0.001).

CONCLUSIONS

These results suggest that MET expression has different prognostic significance in patients with differing EGFR mutation status. Whether MET inhibitors should be given early to NSCLC patients with EGFR wild-type needs further investigation.

Targeting the MET pathway for potential treatment of NSCLC

INTRODUCTION

The mesenchymal-epithelial transition (MET) protein is the only known receptor for hepatocyte growth factor and has recently been identified as a novel promising target in several human cancers, including NSCLC. Activation of the MET signaling pathway can occur via different mechanisms. A number of compounds targeting MET have been evaluated in clinical trials, and recent clinical data have begun to afford some insight into the tumor types and patient populations that might benefit from treatment with MET pathway inhibitors.

AREAS COVERED

We review recent publications and information disclosed at public conferences and summarize the epidemiology of dysregulation of MET signaling, and the associations thereof with other driver genes and therapeutic inhibitors useful to treat NSCLC.

EXPERT OPINION

The MET pathway is emerging as a target for advanced NSCLC that is either resistant to EGFR tyrosine kinase inhibitors or that arises de novo. MET inhibitors currently being evaluated in clinical trials have yielded compelling evidence of clinical activities when used to treat various solid tumors, especially NSCLC. Remaining challenges are the identification of patient populations who might benefit from the use of MET inhibitors, and the most effective diagnostic methods for such patients.

Setting up a wide panel of patient-derived tumor xenografts of non-small cell lung cancer by improving the preanalytical steps

With the ongoing need to improve therapy for non–small cell lung cancer (NSCLC) there has been increasing interest in developing reliable preclinical models to test novel therapeutics. Patient-derived tumor xenografts (PDX) are considered to be interesting candidates. However, the establishment of such model systems requires highly specialized research facilities and introduces logistic challenges. We aimed to establish an extensive well-characterized panel of NSCLC xenograft models in the context of a long-distance research network after careful control of the preanalytical steps. One hundred fresh surgically resected NSCLC specimens were shipped in survival medium at room temperature from a hospital-integrated biobank to animal facilities. Within 24 h post-surgery, tumor fragments were subcutaneously xenografted into immunodeficient mice. PDX characterization was performed by histopathological, immunohistochemical, aCGH and next-generation sequencing approaches. For this model system, the tumor take rate was 35%, with higher rates for squamous carcinoma (60%) than for adenocarcinoma (13%). Patients for whom PDX tumors were obtained had a significantly shorter disease-free survival (DFS) compared to patients for whom no PDX tumors (P = 0.039) were obtained. We established a large panel of PDX NSCLC models with a high frequency of mutations (29%) in EGFR, KRAS, NRAS, MEK1, BRAF, PTEN, and PI3KCA genes and with gene amplification (20%) of c-MET and FGFR1. This new patient-derived NSCLC xenograft collection, established regardless of the considerable time required and the distance between the clinic and the animal facilities, recapitulated the histopathology and molecular diversity of NSCLC and provides stable and reliable preclinical models for human lung cancer research.

Single-nucleotide polymorphism rs41736 located in MET was significantly associated with prognosis of small cell lung cancer patients

MET has been suggested to have an intimate relationship with small cell lung cancer (SCLC) and might be a promising therapeutic target. To date, relatively limited reports have been explored on MET mutational status in SCLC patients. To investigate the relationship between MET mutations and SCLC, 68 Chinese patients surgically treated for SCLC were enrolled. MET mutational analyses were performed in tumors, adjacent normal tissues as well as in lymph nodes with no metastasis nonadherent to tumor tissues using Sanger sequencing after PCR. The same mutation types were found in tumors, adjacent normal tissues as well as lymph nodes, including the only missense mutation N375S encoding semaphorin domain in exon 2 in 4 patients (5.9%), one single-nucleotide polymorphism (SNP) rs35775721: C>T also encoding semaphorin domain as heterozygous in 10 cases (14.7%) and another SNP rs41736: C>T encoding tyrosine kinase domain in exon 20 existing in 49 cases (72.1%). In survival analysis, the wild genotype CC-carriers of rs41736 conferred a significantly shorter progression-free survival (PFS) and overall survival (OS) compared to CT + TT-carriers (HR 0.455, 95% CI 0.229-0.904; HR 0.226, 95% CI 0.099-0.515, for PFS and OS, respectively) in limited-stage SCLC patients. We also found that the lymph node status was significantly associated with OS, and the shorter OS was present in positive group (HR 2.187, 95% CI 1.170-4.088). In this study, rs41736 polymorphism of MET was first found to be associated with prognosis of limited-stage SCLC patients and could be considered as a prognostic marker for limited-stage SCLC.

Redundant kinase activation and resistance of EGFR-tyrosine kinase inhibitors

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have shown dramatic effects against that tumors harboring EGFR activating mutations in the EGFR intracytoplasmic tyrosine kinase domain and resulted in cell apoptosis. Unfortunately, a number of patients ultimately developed resistance by multiple mechanisms. Thus, elucidation of the mechanism of resistance to EGFR-TKIs can provide strategies for blocking or reversing the situation. Recent studies suggested that redundant kinase activation plays pivotal roles in escaping from the effects of EGFR-TKIs. Herein, we aimed to characterize several molecular events involved in the resistance to EGFR-TKIs mediated by redundant kinase activation.

[Targeted therapies in non-small cell lung cancer in 2014]

For several years, the identification of molecular sequencing alterations has considerably changed the perception and treatment of non-small cell lung cancer (NSCLC). These alterations have been defined as "driver mutations", such as mutations in EGFR and EML4-ALK fusion gene, and are highly sensitive to specific therapies. Other targets have also been identified recently. Personalized medicine is now a reality for patients with advanced NSCLC on the basis of routine screening for EGFR, HER2, KRAS, BRAF, PI3KCA mutations and EML4-ALK rearrangement. This article describes identified biomarkers, available targeted therapies, and the main clinical research approaches in NSCLC.

Increased MET Gene Copy Number but Not mRNA Level Predicts Postoperative Recurrence in Patients with Non-Small Cell Lung Cancer

The aim of the present study was to investigate the relationship of MET copy number (CN) and MET mRNA expression to other molecular alterations, clinicopathologic characteristics, and survival of patients with resected non–small cell lung cancer. One hundred fifty-one paired surgical samples of tumor and tumor-distant normal lung tissues were analyzed by comparative quantitative polymerase chain reaction (PCR) methods with commercially available assays and the CopyCaller software v. 1.0 for post-PCR data processing (downloadable from www.appliedbiosystems.com). MET copy gain (set as more than 3.0 copies per cell) was found in 18.5% of the samples and occurred more frequently in the adenocarcinomas (ADCs) with an increased epidermal growth factor receptor (EGFR) or human epidermal growth factor receptor 2 (HER2) CN (P = .001 and .030 for EGFR and HER2, respectively) and in the ADCs with EGFR activating mutations (P = .051) but did not correlate with KRAS dosage or mutational status. MET mRNA level was 1.76-fold higher [95% confidence interval (CI), 1.29-2.40] in the tumor compared to unaffected lung tissue and associated significantly with MET CN (beta coefficient, 1.51; 95% CI, 1.22-1.87; P < .001). In the multivariable analysis, patients diagnosed with ADC with increased MET CN had a significantly higher risk of disease recurrence (hazard ratio, 1.76; 95% CI, 1.20-2.57; P = .004). An increased MET CN in combination with histologic type appears to be a prognostic factor in patients with ADC after a curative surgery.

Tumor MET expression profile predicts the outcome of non-small cell lung cancer patients receiving epidermal growth factor receptor tyrosine kinase inhibitors

BACKGROUND

This study assesses whether MET expression in tumor tissue is associated with an increased sensitivity to epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) in non-small-cell lung cancer (NSCLC) patients.

METHODS

This retrospective study included 69 NSCLC participants with available tumor tissue and data on treatment response and survival. MET and hepatocyte growth factor expression in tumor tissue were evaluated by immunohistochemistry.

RESULTS

Positive tMET expression correlated with a shorter progression-free survival (PFS; P = 0.003) and overall survival (OS; P = 0.05). Positive pY1234/1235 expression was significantly associated with a longer PFS (P = 0.031) and OS (P = 0.012). In multivariable analyses, tMET and pY1234/1235 expression were independent factors for PFS and OS, respectively. (tMET, PFS; P = 0.02, OS; P = 0.0007 and pY1234/1234, PFS; P = 0.01, OS; P = 0.004).

CONCLUSIONS

This study suggests that total and phosphorylated MET expression in tumor tissue is potentially useful for the selection of NSCLC patients who are likely to benefit from EGFR-TKIs, irrespective of their EGFR status.

Monitoring reversal of MET-mediated resistance to EGFR tyrosine kinase inhibitors in non-small cell lung cancer using 3'-deoxy-3'-[18F]-fluorothymidine positron emission tomography

PURPOSE

MET amplification is one of the mechanisms underlying acquired resistance to EGFR tyrosine kinase inhibitors (TKI) in non-small cell lung cancer (NSCLC). Here, we tested whether 3'-deoxy-3'-[(18)F]-fluorothymidine ([(18)F]FLT) positron emission tomography/computerized tomography (PET/CT) can detect MET-mediated resistance to EGFR TKIs and monitor the effects of MET inhibitors in NSCLC.

EXPERIMENTAL DESIGN

H1993 and H820 NSCLC cells with high and low levels of MET amplification, respectively, and HCC827-expressing MET, but without gene amplification, were tested for the effects of MET inhibitors on the EGFR pathway and proliferation both in vitro and in vivo. Nude mice bearing NSCLCs with and without MET amplification were subjected to [(18)F]FLT PET/CT before and after treatment with crizotinib or erlotinib (50 mg/kg and 100 mg/kg p.o. for 3 days).

RESULTS

H1993 cells showed high responsiveness to MET inhibitors and were resistant to erlotinib. Conversely, HCC827 cells showed high sensitivity to erlotinib and were resistant to MET inhibitors. Accordingly, H1993 tumors bearing MET amplification showed a mean reduction in [(18)F]FLT uptake of 28% and 41% after low- and high-dose treatment with crizotinib for 3 days, whereas no posttherapy changes of [(18)F]FLT uptake were observed in HCC827 tumors lacking MET amplification. Furthermore, a persistently high [(18)F]FLT uptake was observed in H1993 tumors after treatment with erlotinib, whereas HCC827 tumors showed up to 39% reduction of [(18)F]FLT uptake following erlotinib treatment. Imaging findings were confirmed by Ki67 immunostaining of tumor sections.

CONCLUSIONS

[(18)F]FLT PET/CT can detect MET-mediated resistance to EGFR TKIs and its reversal by MET inhibitors in NSCLC.

Targeting MET Amplification as a New Oncogenic Driver

Certain genetically defined cancers are dependent on a single overactive oncogene for their proliferation and survival, a phenomenon known as "oncogene addiction". A new generation of drugs that selectively target such "driver oncogenes" manifests a clinical efficacy greater than that of conventional chemotherapy in appropriate genetically defined patients. MET is a proto-oncogene that encodes a receptor tyrosine kinase, and aberrant activation of MET signaling occurs in a subset of advanced cancers as result of various genetic alterations including gene amplification, polysomy, and gene mutation. Our preclinical studies have shown that inhibition of MET signaling either with the small-molecule MET inhibitor crizotinib or by RNA interference targeted to MET mRNA resulted in marked antitumor effects in cancer cell lines with MET amplification both in vitro and in vivo. Furthermore, patients with non-small cell lung cancer or gastric cancer positive for MET amplification have shown a pronounced clinical response to crizotinib. Accumulating preclinical and clinical evidence thus suggests that MET amplification is an "oncogenic driver" and therefore a valid target for treatment. However, the prevalence of MET amplification has not been fully determined, possibly in part because of the difficulty in evaluating gene amplification. In this review, we provide a rationale for targeting this genetic alteration in cancer therapy.

Gefitinib: re-emerging from the shadows

SUMMARY In the past decade, the identification of mutations in the EGFR gene and the sensitivity of activating mutations to EGF receptor–tyrosine kinase inhibitors has improved survival in a subset of non-small-cell lung cancer patients. Over 70% of patients with EGFR mutations have a response to gefitinib therapy. Gefitinib, a first-generation EGF receptor–tyrosine kinase inhibitor, is well tolerated and continues to be widely used. However, eventually most patients develop resistance to gefitinib. This article reviews the pharmacology of gefitinib and summarizes the clinical trials that have resulted in its current day indications.

Characterization of a novel long noncoding RNA, SCAL1, induced by cigarette smoke and elevated in lung cancer cell lines

The incidence of lung diseases and cancer caused by cigarette smoke is increasing. The molecular mechanisms of gene regulation induced by cigarette smoke that ultimately lead to cancer remain unclear. This report describes a novel long noncoding RNA (lncRNA) that is induced by cigarette smoke extract (CSE) both in vitro and in vivo and is elevated in numerous lung cancer cell lines. We have termed this lncRNA the smoke and cancer-associated lncRNA-1 (SCAL1). This lncRNA is located in chromosome 5, and initial sequencing analysis reveals a transcript with four exons and three introns. The expression of SCAL1 is regulated transcriptionally by nuclear factor erythroid 2-related factor (NRF2), as determined by the small, interfering RNA (siRNA) knockdown of NRF2 and kelch-like ECH-associated protein 1 (KEAP1). A nuclear factor erythroid-derived 2 (NF-E2) motif was identified in the promoter region that shows binding to NRF2 after its activation. Functionally, the siRNA knockdown of SCAL1 in human bronchial epithelial cells shows a significant potentiation of cytotoxicity induced by CSE in vitro. Altogether, these results identify a novel and intriguing new noncoding RNA that may act downstream of NRF2 to regulate gene expression and mediate oxidative stress protection in airway epithelial cells.

Acquired resistance of non-small cell lung cancer to epidermal growth factor receptor tyrosine kinase inhibitors

Activation of epidermal growth factor receptor (EGFR) triggers anti-apoptotic signaling, proliferation, angiogenesis, invasion, metastasis, and drug resistance, which leads to development and progression of human epithelial cancers, including non-small cell lung cancer (NSCLC). Inhibition of EGFR by tyrosine kinase inhibitors such as gefitinib and erlotinib has provided a new hope for the cure of NSCLC patients. However, acquired resistance to gefitinib and erlotinib via EGFR-mutant NSCLC has occurred through various molecular mechanisms such as T790M secondary mutation, MET amplification, hepatocyte growth factor (HGF) overexpression, PTEN downregulation, epithelial-mesenchymal transition (EMT), and other mechanisms. This review will discuss the biology of receptor tyrosine kinase inhibition and focus on the molecular mechanisms of acquired resistance to tyrosine kinase inhibitors of EGFR-mutant NSCLC.

Establishment of patient-derived non-small cell lung cancer xenograft models with genetic aberrations within EGFR, KRAS and FGFR1: useful tools for preclinical studies of targeted therapies

BACKGROUND

Patient-derived tumor xenograft models have been established and increasingly used for preclinical studies of targeted therapies in recent years. However, patient-derived non-small cell lung cancer (NSCLC) xenograft mouse models are relatively few in number and are limited in their degree of genetic characterization and validation. In this study, we aimed to establish a variety of patient-derived NSCLC models and characterize these for common genetic aberrations to provide more informative models for preclinical drug efficacy testing.

METHODS

NSCLC tissues from thirty-one patients were collected and implanted into immunodeficient mice. Established xenograft models were characterized for common genetic aberrations, including detection of gene mutations within EGFR and KRAS, and genetic amplification of FGFR1 and cMET. Finally, gefitinib anti-tumor efficacy was tested in these patient-derived NSCLC xenograft models.

RESULTS

Ten passable patient-derived NSCLC xenograft models were established by implantation of NSCLC specimens of thirty-one patients into immunodeficient mice. Genetic aberrations were detected in six of the models, including one model with an EGFR activating mutation (Exon19 Del), one model with KRAS mutation, one model with both KRAS mutation and cMET gene amplification, and three models with FGFR1 amplification. Anti-tumor efficacy studies using gefitinib demonstrated that the EGFR activating mutation model had superior sensitivity and that the KRAS mutation models were resistant to gefitinib. The range of gefitinib responses in the patient-derived NSCLC xenograft models were consistent with the results reported from clinical trials. Furthermore, we observed that patient-derived NSCLC models with FGFR1 gene amplification were insensitive to gefitinib treatment.

CONCLUSIONS

Ten patient-derived NSCLC xenograft models were established containing a variety of genetic aberrations including EGFR activating mutation, KRAS mutation, and FGFR1 and cMET amplification. Gefitinib anti-tumor efficacy in these patient-derived NSCLC xenografts containing EGFR and KRAS mutation was consistent with the reported results from previous clinical trials. Thus, data from our panel of patient-derived NSCLC xenograft models confirms the utility of these models in furthering our understanding of this disease and aiding the development of personalized therapies for NSCLC patients.

EGF receptor activates MET through MAPK to enhance non-small cell lung carcinoma invasion and brain metastasis

MET amplification as a mechanism of acquired resistance to EGF receptor (EGFR)-targeted therapies in non-small cell lung carcinoma (NSCLC) led to investigation of novel combinations of EGFR and MET kinase inhibitors. However, promiscuous interactions between MET and ERBB family members have made it difficult to evaluate the effects of MET on EGFR signaling, both independent of drug treatment and in the context of drug resistance. We addressed this issue by establishing a 32D model cell system wherein ERBBs or MET are expressed alone and in combination. Using this model, we determined that EGFR signaling is sufficient to induce MET phosphorylation, although MET activation is enhanced by coexpression of ERBB3. EGFR-MET cross-talk was not direct, but occurred by a combined regulation of MET levels and intermediary signaling through mitogen-activated protein kinases (MAPK). In NSCLCs harboring either wild-type or mutant EGFR, inhibiting EGFR or MAPK reduced MET activation and protein levels. Furthermore, MET signaling promoted EGFR-driven migration and invasion. Finally, EGFR-MET signaling was enhanced in a highly metastatic EGFR-mutant cell subpopulation, compared with the indolent parental line, and MET attenuation decreased the incidence of brain metastasis. Overall, our results establish that EGFR-MET signaling is critical for aggressive behavior of NSCLCs and rationalize its continued investigation as a therapeutic target for tumors harboring both wild-type and mutant EGFR at early stages of progression.

Acquired resistance to EGFR inhibitors is associated with a manifestation of stem cell-like properties in cancer cells

Acquired resistance to EGF receptor (EGFR) tyrosine kinase inhibitor (TKI) is a critical problem in the treatment of lung cancer. Although several mechanisms have been shown to be responsible for acquired resistance, all mechanisms have not been uncovered. In this study, we investigated the molecular and cellular profiles of the acquired resistant cells to EGFR-TKI in EGFR-mutant lung cancers. Four EGFR-mutant cell lines were exposed to gefitinib by stepwise escalation and high-concentration exposure methods, and resistant sublines to gefitinib were established. The molecular profiles and cellular phenotypes of these resistant sublines were characterized. Although previously reported, alterations including secondary EGFR T790M mutation, MET amplification, and appearance of epithelial-to-mesenchymal transition (EMT) features were observed, these 2 drug-exposure methods revealed different resistance mechanisms. The resistant cells with EMT features exhibited downregulation of miRNA-200c by DNA methylation. Furthermore, the HCC827-derived subline characterized by the high-concentration exposure method exhibited not only EMT features but also stem cell-like properties, including aldehyde dehydrogenase isoform 1 (ALDH1A1) overexpression, increase of side-population, and self-renewal capability. Resistant sublines with stem cell-like properties were resistant to conventional chemotherapeutic agents but equally sensitive to histone deacetylase and proteasome inhibitors, compared with their parental cells. ALDH1A1 was upregulated in clinical samples with acquired resistance to gefitinib. In conclusion, our study indicates that the manner of EGFR-TKI exposure influences the mechanism of acquired resistance and the appearance of stem cell-like property with EGFR-TKI treatment.

Detection and therapeutic implications of c-Met mutations in small cell lung cancer and neuroendocrine tumors

BACKGROUND

We evaluated the mutation status of c-Met in small cell lung cancer (SCLC) and neuroendocrine tumors (NET), for which relatively limited therapeutic targets have been explored.

MATERIALS AND METHODS

c-Met was re-sequenced using cell lines and clinical samples. For in vitro studies, DNA constructs containing a juxtamembrane domain (JMD) and tyrosine kinase domain (TKD) were generated. Detected mutations were introduced into the construct and effects on c-Met phosphorylation and interaction with tyrosine kinase inhibitor drugs BMS777607 and SU11274 were assessed.

RESULTS

97 specimens were analyzed: 13 SCLC and 2 pulmonary carcinoid cell lines, 46 SCLC and 36 NET clinical specimens. Mutations were only detected in the JMD. No mutations were detected in the TKD. Found mutations consisted of the previously reported R988C and T1010I mutations. One novel JMD mutation, P996S, was detected in a SCLC specimen. The mutation rate in SCLC cell lines was 25% (31% including a derivative cell line), and 6.5% in clinical specimens. The mutation rate in NET was 8.3%. In vitro, there were no differences between wild type, R988C or T1010I mutants regarding c-Met phosphorylation at Y1003, located in the JMD, and at Y1234/1235, located in the TKD. BMS777607 and SU11274 were shown to inhibit phosphorylation of c-Met in wild type and R988C and T1010I mutants in a similar fashion.

CONCLUSIONS

In SCLC and neuroendocrine tumors MET mutations are relatively rare. Detected mutations were located in the juxtamembrane domain and were of no functional relevance as they did not influence c-Met phosphorylation, regardless of TKI treatment.

Development of PI3K/AKT/mTOR pathway inhibitors and their application in personalized therapy for non-small-cell lung cancer

Lung cancer is a common disease with more than 1.6 million new cases diagnosed worldwide in 2008. Treatments for patients with advanced disease are rarely curative, and responses to therapy are often followed by relapse, which highlights the large unmet need for novel therapies. Recent advances in cancer treatment have focused on personalized therapy, whereby patients are treated with agents that best target the molecular drivers of their disease. Thus, a better understanding of the pathways that drive cancer or drug resistance is of critical importance. One such example is the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, which is activated in many lung cancer patients and represents a target for therapy. PI3K/AKT/mTOR pathway activation has also been observed in tumors resistant to agents targeting upstream receptor tyrosine kinases. Agents that target this pathway have the potential to shut down survival pathways, and are being explored both in the setting of pathway-activating mutations and for their ability to restore sensitivity to upstream signaling targeted agents. Here, we examine the frequency of mutations activating the PI3K/AKT/mTOR pathway, review the novel agents being explored to target this pathway, and explore the potential role of the inhibition of this pathway in the clinical development of these agents.

Mechanisms of resistance to reversible inhibitors of EGFR tyrosine kinase in non-small cell lung cancer

Abnormalities of epidermal growth factor receptor (EGFR) in non-small-cell lung cancer (NSCLC) patients consist of EGFR overexpression and EGFR (HER1) gene mutations. Structural dysfunction of the tyrosine kinase domain of EGFR is associated with the clinical response to tyrosine kinase inhibitors (TKI) in patients with NSCLC. The most common EGFR gene mutations occur as either deletions in exon 19 or as substitution L858R in exon 21 and cause a clinically beneficial response to gefinitib or erlotinib treatment. Unfortunately, the majority of patients finally develop resistance to these drugs. Acquired resistance is linked to secondary mutations localised in the EGFR gene, mainly substitution T790M in exon 20. Through intense research a few different mechanisms of resistance to reversible tyrosine kinase inhibitors have been identified: amplification of MET or IGF-1R genes, abnormalities of PTEN and mTOR proteins as well as rare mutations in EGFR and HER2 genes. Extensively investigated new drugs could be of significant efficiency in NSCLC patients with secondary resistance to reversible EGFR TKI.

Overcoming erlotinib resistance with tailored treatment regimen in patient-derived xenografts from naïve Asian NSCLC patients

Overall benefits of EGFR-TKIs are limited because these treatments are largely only for adenocarcinoma (ADC) with EGFR activating mutation. The treatments also usually lead to development of resistances. We have established a panel of patient-derived xenografts (PDXs) from treatment naïve Asian NSCLC patients, including those containing "classic" EGFR activating mutations. Some of these EGFR-mutated PDXs do not respond to erlotinib: LU1868 containing L858R/T790M mutations, and LU0858 having L858R mutation as well as c-MET gene amplification, both squamous cell carcinoma (SCC). Treatment of LU0858 with crizotinib, a small molecule inhibitor for ALK and c-MET, inhibited tumor growth and c-MET activity. Combination of erlotinib and crizotinib caused complete response, indicating the activation of both EGFR and c-MET promote its growth/survival. LU2503 and LU1901, both with wild-type EGFR and c-MET gene amplification, showed complete response to crizotinib alone, suggesting that c-MET gene amplification, not EGFR signaling, is the main oncogenic driver. Interestingly, LU1868 with the EGFR L858R/T790M, but without c-met amplification, had a complete response to cetuximab. Our data offer novel practical approaches to overcome the two most common resistances to EGFR-TKIs seen in the clinic using marketed target therapies.

Molecular Pathology of Non-Small Cell Lung Cancer

This review offers an overview of the molecular pathology of lung cancer, with a focus on analyses that are most commonly part of the current clinical testing paradigm. Molecular testing of lung cancer has proved integral to the success of new targeted therapies, and their use is now commonplace in treatment selection. Traditional pathologic evaluation, however, plays a major role in these advances and serves an equally critical role to aid in determining optimal therapy.

Macroporous hydrogel micropillars for quantifying Met kinase activity in cancer cell lysates

Overactive and overexpressed kinases have been implicated in the cause and progression of many cancers. Kinase inhibitors offer a targeted approach for treating cancers associated with increased or deregulated kinase activity. Often, however, cancer cells exhibit initial resistance to these inhibitors or evolve to develop resistance during treatment. Additionally, cancers of any one tissue type are typically heterogeneous in their oncogenesis mechanisms, and thus diagnosis of a particular type of cancer does not necessarily provide insight into what kinase therapies may be effective. For example, while some lung cancer cells that overexpress the epidermal growth factor receptor (EFGR) respond to treatment with EGFR kinase inhibitors, overexpression or hyperactivity of Met kinase correlates with resistance to EGFR kinase inhibitors. Here we describe a microfluidic-based assay for quantifying Met kinase activity in cancer cell lysates with the eventual goals of predicting cancer cell responsiveness to kinase inhibitors and monitoring development of resistance to these inhibitors. In this assay, we immobilized a phosphorylation substrate for Met kinase into macroporous hydrogel micropillars. We then exposed the micropillars to a cancer cell lysate and detected substrate phosphorylation using a fluorescently conjugated antibody. This assay is able to quantify Met kinase activity in whole cell lysate from as few as 150 cancer cells. It can also detect cells expressing overactive Met kinase in a background of up to 75% non-cancerous cells. Additionally, the assay can quantify kinase inhibition by the Met-specific kinase inhibitors SU11274 and PHA665752, suggesting predictive capability for cellular response to kinase inhibitors.

T790M and acquired resistance of EGFR TKI: a literature review of clinical reports

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib are promising therapies for patients with advanced non-small-cell lung cancer (NSCLC). Patients with somatic activating mutations in the EGFR gene have dramatic response initially, but would eventually develop resistance to these TKIs. Subsequent studies found that a secondary mutation in the EGFR gene (T790M mutation) and amplification of the MET proto-oncogene could be the main resistance mechanisms involved. The current review is focused on T790M, which is thought to cause steric hindrance and impair the binding of gefitinib/erlotinib. The T790M is present as a minor allele before TKI therapy and accounts for about half of the acquired resistant cases. Conflicting results were reported for gefitinib-resistant, T790M-acquired patients who had switched to erlotinib treatment, which was proposed to be efficacious. The switch therapy was presumed to work for EGFR wild type patients and previously gefitinib responding patients. MET amplification accounts for about 20% of TKI acquired-resistant patients by a different molecular pathway from T790M; some of these patients will also concurrently have T790M mutation and might still not respond to irreversible TKI. As for the detection of T790M, polymerase chain reaction (PCR), especially mutant-enriched PCR was found to be more sensitive than direct DNA sequencing. In addition, whole genome amplification might also be useful and can be incorporated with future noninvasive method for detecting T790M. A better understanding of the mechanisms leading to TKI resistance is crucial in the development of effective treatment and the design of future clinical studies.

Anti-proliferative effect of cytohesin inhibition in gefitinib-resistant lung cancer cells

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI), such as gefitinib, have been proven to efficiently inhibit the proliferation of a subset of non small-cell lung cancers (NSCLC). Unfortunately, the majority of NSCLC expressing wild type EGFR is primarily resistant to EGFR-TKI treatment. Here, we show that the proliferation of the gefitinib-resistant NSCLC cell lines H460 and A549 is reduced by the small molecule SecinH3 which indirectly attenuates EGFR activation by inhibition of cytohesins, a class of recently discovered cytoplasmic EGFR activators. SecinH3 and gefitinib showed a synergistic antiproliferative effect, which correlated with a profound inhibition of Akt activation and survivin expression. Treating mice bearing H460 xenografts with SecinH3 showed the antiproliferative and pro-apoptotic effect of SecinH3 in vivo. Our data suggest that targeting the EGFR indirectly by inhibiting its cytoplasmic activators, the cytohesins, has the potential to improve the treatment of primarily EGFR-TKI resistant lung cancers.

Recent understanding of the molecular mechanisms for the efficacy and resistance of EGF receptor-specific tyrosine kinase inhibitors in non-small cell lung cancer

INTRODUCTION

The epidermal growth factor receptor (EGFR) and its family members are involved in many aspects of tumor biological processes. Aberrant activation of the EGFR tyrosine kinase by mutations or protein overexpression is observed in various types of human cancer, including lung cancer. EGFR tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib and erlotinib, are highly effective in lung cancer patients who harbor active mutations in the EGFR gene. However, patients who are initially sensitive to EGFR-TKIs eventually relapse within few years.

AREAS COVERED

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and is associated with a high frequency of EGFR mutations. This review describes the EGFR mutations that determine the sensitivity to EGFR-TKIs and the current understanding of the molecular mechanisms of acquired resistance to EGFR-TKIs in NSCLC. Furthermore, the authors describe recent strategies developed to overcome acquired resistance using second-generation EGFR-TKIs and combination therapies with several molecular-targeting drugs.

EXPERT OPINION

Although recent findings have contributed to our understanding of the mechanism of acquired resistance and helped the development of novel strategies to overcome such resistance, the underlying mechanisms are complex and additional research is necessary to develop effective therapeutic strategies for individual patients with lung cancer.

Correlation between MET gene copy number by silver in situ hybridization and protein expression by immunohistochemistry in non-small cell lung cancer

PURPOSE

The MET receptor is involved in the pathogenesis and progression of non-small cell lung cancer (NSCLC). Clinical trials with MET inhibitors in NSCLC are planned with patient selection based on immunohistochemistry (IHC) and/or gene copy number assessment. Therefore, a detailed understanding of relationship between these markers and prognosis is essential.

METHODS

This study included tumors from 189 patients with NSCLC who underwent pulmonary resection (median follow-up, 5.3 years). MET expression was evaluated by IHC on tissue microarrays and scored according to hybrid (H) score (range: 0-400) and by scoring system used in the MetMAb trial (≥ 50% of cells with moderate or strong staining). MET gene copy number was assessed by silver in situ hybridization (n =140 patients).

RESULTS

Median MET IHC H score was 60 (range: 0-400; n =174). There were no associations between clinical and pathological characteristics, disease-free survival, and overall survival according to median value (p =0.36 and p =0.38, respectively), or other cut-points. According to MetMAb scoring criteria, IHC positivity rate was 25%, again with no associations to clinicopathological features or survival. In 140 tumors evaluable for MET copy number, 3 (2.1%) showed gene amplification and 14 (10%) had tumors with average of 5 or more copies per nucleus. There were no associations of MET copy number with clinical characteristics, disease-free survival, or overall survival with any analyzed cut-points. Correlation between MET copy number and protein expression was significant (Pearson's r =0.42, p < 0.0001).

CONCLUSIONS

There is a significant correlation between MET protein expression and MET gene copy number in operable NSCLC, but neither is associated with prognosis.

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.