Functional expression and mutations of c-Met and its therapeutic inhibition with SU11274 and small interfering RNA in non-small cell lung cancer

Tissue array analysis of expression microarray candidates identifies markers associated with tumor grade and outcome in serous epithelial ovarian cancer

Molecular profiling is a powerful approach to identify potential clinical markers for diagnosis and prognosis as well as providing a better understanding of the biology of epithelial ovarian cancer. On the basis of the analysis of HuFL expression data, we have previously identified genes that distinguish low malignant potential and invasive serous epithelial ovarian tumors. In this study, we used immunohistochemistry to monitor a subset of differently expressed candidates (Ahr, Paep, Madh3, Ran, Met, Mek1, Ccne1, Ccd20, Cks1 and Cas). A tissue array composed of 244 serous tumors of different grades (0-3) and stages (I-IV) was used in this analysis. All markers assayed presented differential protein expression between serous tumors of low and high grade. Significant differences in Ccne1 and Ran expression were observed in a comparison of low malignant potential and grade 1 tumor samples (p<0.01). In addition, irrespective of the grade, Ccne1, Ran, Cdc20 and Cks1 showed significant differences of expression in association with the clinical stage of disease. While high level of Ccne1 have previously been associated with poor outcomes, here we found that high level of either Ran or Cdc20 appear to be more tightly associated with a poor prognosis (p<0.001, 0.03, respectively). The application of these biomarkers in both the initial diagnosis and prognostic attributes of patients with epithelial ovarian tumors should prove to be useful in patient management.

A transforming MET mutation discovered in non-small cell lung cancer using microarray-based resequencing

We have designed resequencing microarrays to test the performance of this platform when interrogating a large number of exons (164 total) from genes associated with cancer. To evaluate false positive and negative rates, dideoxy sequencing was done for 335,420 bases interrogated by the arrays. From the array data, calls could be made for approximately 97.5% of the bases, and false positive rates were very low with only a single mutation reported from the array dataset for which the corresponding dideoxy trace had a clean wildtype sequence. For the nucleotide positions where array calls were made, false negative rates were 1.41% for heterozygous mutations. All the homozygous mutations were detected, but 8.11% were erroneously reported as heterozygous changes from the reference sequence by the array analysis software. In addition, 20 non-small cell lung cancer (NSCLC) samples were analyzed using the arrays, and both somatic and germline mutations were found. The most interesting findings were two MET mutations that have recently been implemented in NSCLC. Large scale MALDI-TOF genotyping indicated that one of these mutations (T1010I) might represent a true cancer-causing genotype, whereas the other (N375S) appears to be a common germline polymorphism.

Evidence that MIG-6 is a tumor-suppressor gene

Mitogen-inducible gene 6 (MIG-6) is located in human chromosome 1p36, a locus frequently associated with human lung cancer. MIG-6 is a negative regulator of epidermal growth factor (EGF) signaling, and we show that Mig-6 - like EGF - is induced by hepatocyte growth factor/scatter factor (HGF/SF) in human lung cancer cell lines. Frequently, the receptors for both factors, EGFR and Met, are expressed in same lung cancer cell line, and MIG-6 is induced by both factors in a mitogen-activated protein kinase-dependent fashion. However, not all tumor lines express MIG-6 in response to either EGF or HGF/SF. In these cases, we find missense and nonsense mutations in the MIG-6 coding region, as well as evidence for MIG-6 transcriptional silencing. Moreover, germline disruption of Mig-6 in mice leads to the development of animals with epithelial hyperplasia, adenoma, and adenocarcinoma in organs like the lung, gallbladder, and bile duct. These data suggests that MIG-6 is a tumor-suppressor gene and is therefore a candidate gene for the frequent 1p36 genetic alterations found in lung cancer.

Prospects of RNA interference therapy for cancer

RNA interference (RNAi) is a powerful gene-silencing process that holds great promise in the field of cancer therapy. The discovery of RNAi has generated enthusiasm within the scientific community, not only because it has been used to rapidly identify key molecules involved in many disease processes including cancer, but also because RNAi has the potential to be translated into a technology with major therapeutic applications. Our evolving understanding of the molecular pathways important for carcinogenesis has created opportunities for cancer therapy employing RNAi technology to target the key molecules within these pathways. Many gene products involved in carcinogenesis have already been explored as targets for RNAi intervention, and RNAi targeting of molecules crucial for tumor-host interactions and tumor resistance to chemo- or radiotherapy has also been investigated. In most of these studies, the silencing of critical gene products by RNAi technology has generated significant antiproliferative and/or proapoptotic effects in cell-culture systems or in preclinical animal models. Nevertheless, significant obstacles, such as in vivo delivery, incomplete suppression of target genes, nonspecific immune responses and the so-called off-target effects, need to be overcome before this technology can be successfully translated into the clinical arena. Significant progress has already been made in addressing some of these issues, and it is foreseen that early phase clinical trials will be initiated in the very near future.

High-throughput mutational analysis of the human cancer genome

Cancer is essentially a genetic disease. Recent high-throughput mutational analyses of gene families in human colorectal, breast and lung cancer, myeloproliferative disorders, and other tumor types have identified a number of kinases and phosphatases that are mutated in the human cancer genome. This approach has been proven to be an efficient way to catalog tumor-specific mutations in human cancers. Although there are still some technical hurdles to overcome, it is not a far-reaching goal to perform genome-wide mutational analysis in all different tumor types. Systematic cataloging of tumor-specific mutations in the human cancer genome not only will lead to new insights into the mechanisms of tumorigenesis, but also provide unprecedented opportunities in the design of novel therapeutics for cancer patients. Personalized cancer therapy based on tumor-specific mutations will be a realistic goal in the near future.

Treatment of non-small-cell lung cancer and pharmacogenomics: where we are and where we are going

PURPOSE OF REVIEW

This review highlights the numerous molecular biology findings in the field of lung cancer with potential therapeutic impact in both the near and distant future.

RECENT FINDINGS

Abundant preclinical and clinical data indicate that BRCA1 mRNA expression is a differential modulator of chemotherapy sensitivity. Single nucleotide polymorphisms in the excision repair cross-complementing 1 gene (ERCC1) influence survival with cisplatin-based chemotherapy. For the first time, epidermal growth factor receptor (EGFR) mutations have been shown to predict dramatic responses in metastatic lung adenocarcinomas. The crosstalk between estrogen and EGFR pathways have also been revealed. MicroRNAs control the expression of cognate target genes and predict relapse in surgically resected non-small-cell lung cancer patients. Overexpression of the Wingless-type (Wnt) genes and methylation of Wnt antagonists have been documented in non-small-cell lung cancer.

SUMMARY

Understanding the relevance of these findings can help to change the clinical practice in oncology towards customizing chemotherapy and targeted therapies, leading to improvement both in survival and in cost-effectiveness.

Functional analysis of c-Met/hepatocyte growth factor pathway in malignant pleural mesothelioma

c-Met receptor tyrosine kinase (RTK) has not been extensively studied in malignant pleural mesothelioma (MPM). In this study, c-Met was overexpressed and activated in most of the mesothelioma cell lines tested. Expression in MPM tissues by immunohistochemistry was increased (82%) in MPM in general compared with normal. c-Met was internalized with its ligand hepatocyte growth factor (HGF) in H28 MPM cells, with robust expression of c-Met. Serum circulating HGF was twice as high in mesothelioma patients as in healthy controls. There was a differential growth response and activation of AKT and extracellular signal-regulated kinase 1/2 in response to HGF for the various cell lines. Dose-dependent inhibition (IC50 < 2.5 micromol/L) of cell growth in mesothelioma cell lines, but not in H2052, H2452, and nonmalignant MeT-5A (IC50 > 10 micromol/L), was observed with the small-molecule c-Met inhibitor SU11274. Furthermore, migration of H28 cells was blocked with both SU11274 and c-Met small interfering RNA. Abrogation of HGF-induced c-Met and downstream signaling was seen in mesothelioma cells. Of the 43 MPM tissues and 7 cell lines, we have identified mutations within the semaphorin domain (N375S, M431V, and N454I), the juxtamembrane domain (T1010I and G1085X), and an alternative spliced product with deletion of the exon 10 of c-Met in some of the samples. Interestingly, we observed that the cell lines H513 and H2596 harboring the T1010I mutation exhibited the most dramatic reduction of cell growth with SU11274 when compared with wild-type H28 and nonmalignant MeT-5A cells. Ultimately, c-Met would be an important target for therapy against MPM.

Inhibition of the met receptor in mesothelioma

BACKGROUND

Expression of the Met receptor and its ligand, hepatocyte growth factor (HGF), has been observed in 74% to 100% and 40% to 85% of malignant pleural mesothelioma (MPM) specimens, respectively. HGF stimulation has been shown to enhance MPM cell proliferation, migration, cell scattering, and invasiveness.

EXPERIMENTAL DESIGN

To investigate a potential therapeutic role for the Met receptor in MPM, we examined the effects of PHA-665752, a specific small-molecule inhibitor of the Met receptor tyrosine kinase, in a panel of 10 MPM cell lines.

RESULTS

Two of the cell lines, H2461 and JMN-1B, exhibited autocrine HGF production as measured by ELISA (3.9 and 10.5 ng/mL, respectively, versus <0.05 ng/mL in other cell lines). Evaluation of PHA-665752 across the 10 MPM cell lines indicated that despite Met expression in all cell lines, only in cell lines that exhibited a Met/HGF autocrine loop, H2461 and JMN-1B, did PHA-665752 inhibit growth with an IC(50) of 1 and 2 micromol/L, respectively. No activating mutations in Met were detected in any of the cell lines. Consistent with observed growth inhibition, PHA-665752 caused cell cycle arrest at G(1)-S boundary accompanied by a dose-dependent decrease in phosphorylation of Met, p70S6K, Akt, and extracellular signal-regulated kinase 1/2. Growth of H2461 cells was also inhibited by neutralizing antibodies to HGF and by RNA interference knockdown of the Met receptor, confirming that growth inhibition observed was through a Met-dependent mechanism. PHA-665752 also reduced MPM in vitro cell migration and invasion.

CONCLUSIONS

Taken together, these findings suggest that inhibition of the Met receptor may be an effective therapeutic strategy for patients with MPM and provides a mechanism, the presence of a HGF/Met autocrine loop, by which to select patients for PHA-665752 treatment.

Functional analysis of HGF/MET signaling and aberrant HGF-activator expression in diffuse large B-cell lymphoma

Inappropriate activation of MET, the receptor tyrosine kinase for hepatocyte growth factor (HGF), has been implicated in tumorigenesis. Although we have previously shown that HGF/MET signaling controls survival and proliferation of multiple myeloma (MM), its role in the pathogenesis of other B-cell malignancies has remained largely unexplored. Here, we have examined a panel of 110 B-cell malignancies for MET expression, which, apart from MM (48%), was found to be largely confined to diffuse large B-cell lymphomas (DLBCLs) (30%). No amplification of the MET gene was found; however, mutational analysis revealed 2 germ-line missense mutations: R1166Q in the tyrosine kinase domain in 1 patient, and R988C in the juxtamembrane domain in 4 patients. The R988C mutation has recently been shown to enhance tumorigenesis. In MET-positive DLBCL cells, HGF induces MEK-dependent activation of ERK and PI3K-dependent phosphorylation of PKB, GSK3, and FOXO3a. Furthermore, HGF induces PI3K-dependent α4β1 integrin-mediated adhesion to VCAM-1 and fibronectin. Within the tumor microenvironment of DLBCL, HGF is provided by macrophages, whereas DLBCL cells themselves produce the serine protease HGF activator (HGFA), which autocatalyzes HGF activation. Taken together, these data indicate that HGF/MET signaling, and secretion of HGFA by DLBCL cells, contributes to lymphomagenesis in DLBCL. (Blood. 2006;107:760-768)

Gefitinib response of erlotinib-refractory lung cancer involving meninges—role of EGFR mutation

BACKGROUND

A 70-year-old Japanese-American woman who had never smoked was diagnosed with stage IV non-small-cell lung cancer with rib metastases. She had previously been well and she had no family history of malignancy. While receiving treatment with erlotinib, an epidermal growth factor receptor small-molecule inhibitor, she progressed and developed new brain metastases. She failed further chemotherapy treatments and subsequently developed extensive symptomatic leptomeningeal carcinomatosis associated with diplopia, hemiparesis, weight loss, and incontinence.

INVESTIGATIONS

Chest X-ray, head and chest CT scan, R2 lymph-node biopsy, histopathology, immunohistochemistry, MRI of head and spine, lumbar puncture, laser microdissection and EGFR genomic DNA sequencing of the R2 lymph node and cerebrospinal fluid tumor cells.

DIAGNOSIS

Erlotinib-refractory stage IV lung adenocarcinoma and end-stage symptomatic leptomeningeal metastases with a novel double L858R + E884K somatic mutation of the EGFR.

MANAGEMENT

Carboplatin, paclitaxel and erlotinib, whole-brain radiotherapy, temozolomide with and without irinotecan, and gefitinib.

Somatic mutations lead to an oncogenic deletion of met in lung cancer

Activating mutations in receptor tyrosine kinases play a critical role in oncogenesis. Despite evidence that Met kinase is deregulated in human cancer, the role of activating mutations in cancers other than renal papillary carcinoma has not been well defined. Here we report the identification of somatic intronic mutations of Met kinase that lead to an alternatively spliced transcript in lung cancer, which encodes a deletion of the juxtamembrane domain resulting in the loss of Cbl E3-ligase binding. The mutant receptor exhibits decreased ubiquitination and delayed down-regulation correlating with elevated, distinct Met expression in primary tumors harboring the deleted receptor. As a consequence, phospho-Met and downstream mitogen-activated protein kinase activation is sustained on ligand stimulation. Cells expressing the Met deletion reveal enhanced ligand-mediated proliferation and significant in vivo tumor growth. A hepatocyte growth factor competitive Met antagonist inhibits receptor activation and proliferation in tumor cells harboring the Met deletion, suggesting the important role played by ligand-dependent Met activation and the potential for anticancer therapy. These results support a critical role for Met in lung cancer and somatic mutation-driven splicing of an oncogene that leads to a different mechanism for tyrosine kinase activation through altered receptor down-regulation in human cancer.

Met/Hepatocyte growth factor receptor ubiquitination suppresses transformation and is required for Hrs phosphorylation

The Met receptor tyrosine kinase (RTK) regulates epithelial remodeling, dispersal, and invasion and is deregulated in many human cancers. It is now accepted that impaired down-regulation, as well as sustained activation, of RTKs could contribute to their deregulation. Down-regulation of the Met receptor involves ligand-induced internalization, ubiquitination by Cbl ubiquitin ligases, and lysosomal degradation. Here we report that a ubiquitination-deficient Met receptor mutant (Y1003F) is tumorigenic in vivo. The Met Y1003F mutant is internalized, and undergoes endosomal trafficking with kinetics similar to the wild-type Met receptor, yet is inefficiently targeted for degradation. This results in sustained activation of Met Y1003F and downstream signals involving the Ras-mitogen-activated protein kinase pathway, cell transformation, and tumorigenesis. Although Met Y1003F undergoes endosomal trafficking and localizes with the cargo-sorting protein Hrs, it is unable to induce phosphorylation of Hrs. Fusion of monoubiquitin to Met Y1003F is sufficient to decrease Met receptor stability and prevent sustained MEK1/2 activation. In addition, this rescues Hrs tyrosine phosphorylation and decreases transformation in a focus-forming assay. These results demonstrate that Cbl-dependent ubiquitination is dispensable for Met internalization but is critical to target the Met receptor to components of the lysosomal sorting machinery and to suppress its inherent transforming activity.

Genetic Classification of Lung Adenocarcinoma Based on Array-Based Comparative Genomic Hybridization Analysis: Its Association with Clinicopathologic Features

The array-based comparative genomic hybridization using microarrayed bacterial artificial chromosome clones allows high-resolution analysis of genome-wide copy number changes in tumors. To analyze the genetic alterations of primary lung adenocarcinoma in a high-throughput way, we used laser-capture microdissection of cancer cells and array comparative genomic hybridization focusing on 800 chromosomal loci containing cancer-related genes. We identified a large number of chromosomal numerical alterations, including frequent amplifications on 7p12, 11q13, 12q14-15, and 17q21, and two homozygous deletions on 9p21 and one on 8p23. Unsupervised hierarchical clustering analysis of multiple alterations revealed three subgroups of lung adenocarcinoma that were characterized by the accumulation of distinct genetic alterations and associated with smoking history and gender. The mutation status of the epidermal growth factor receptor (EGFR) gene was significantly associated with specific genetic alterations and supervised clustering analysis based on EGFR gene mutations elucidated a subgroup including all EGFR gene mutated tumors, which showed significantly shorter disease-free survival. Our results suggest that there exist multiple molecular carcinogenesis pathways in lung adenocarcinoma that may associate with smoking habits and gender, and that genetic cancer profiling will reveal previously uncharacterized genetic heterogeneity of cancer and be beneficial in estimating patient prognosis and discovering novel cancer-related genes including therapeutic targets.