No abstract

b-Catenin is an essential element for the transcriptional activation of target genes in the Wnt signaling cascade and is also a cell adhesion molecule that couples with cadherins. Although plakoglobin (c-catenin), a closely related homologue of b-catenin, is also known to be a cell adhesion molecule, its function as a transcriptional factor has not been revealed in detail. Using a human malignant mesothelioma cell line, NCI-H28, in which we have identified a homozygous deletion of the b-catenin gene, we studied whether plakoglobin has a T-cell factor/ lymphocyte enhancer factor (TCF/LEF) family-dependent transcriptional activity. Transfection with the wildtype plakoglobin expression vector induced accumulation of plakoglobin in the nucleus. Immunoprecipitation assay with cotransfection of plakoglobin and either TCF-4 or LEF-1 detected binding of plakoglobin to TCF-4 or LEF-1. Luciferase reporter assay demonstrated transcriptional activity of the wild-type plakoglobin when transfected with TCF/LEF, although plakoglobin showed less activity than b-catenin. Exogenous plakoglobin was also shown to promote entrance of exogenous b-catenin into the nuclei. Furthermore, small interfering RNA directed against plakoglobin suppressed expression of endogenous plakoglobin and its transcriptional activity, suggesting that endogenous plakoglobin has a weak transcriptional activity. These results suggest that plakoglobin can activate the Wnt signaling cascade directly without interaction of b-catenin, and that plakoglobin has multiple functions as a transcriptional activator and a cell adhesion molecule like b-catenin.

Malignant pleural mesothelioma (MPM) is a fatal thoracic malignancy, the epigenetics of which are poorly defined. We performed high-throughput methylation analysis covering 6,157 CpG islands in 20 MPMs and 20 lung adenocarcinomas. Newly identified genes were further analyzed in 50 MPMs and 56 adenocarcinomas via quantitative methylation-specific PCR. Targets of histone H3 lysine 27 trimethylation (H3K27me3) and genetic alterations were also assessed in MPM cells by chromatin immunoprecipitation arrays and comparative genomic hybridization arrays. An average of 387 genes (6.3%) and 544 genes (8.8%) were hypermethylated in MPM and adenocarcinoma, respectively. Hierarchical cluster analysis showed that the two malignancies have characteristic DNA methylation patterns, likely a result of different pathologic processes. In MPM, a separate subset of genes was silenced by H3K27me3 and could be reactivated by treatment with a histone deacetylase inhibitor alone. Integrated analysis of these epigenetic and genetic alterations revealed that only 11% of heterozygously deleted genes were affected by DNA methylation and/or H3K27me3 in MPMs. Among the DNA hypermethylated genes, three (TMEM30B, KAZALD1, and MAPK13) were specifically methylated only in MPM and could serve as potential diagnostic markers. Interestingly, a subset of MPM cases (4 cases, 20%) had very low levels of DNA methylation and substantially longer survival, suggesting that the epigenetic alterations are one mechanism affecting progression of this disease. Our findings show a characteristic epigenetic profile of MPM and uncover multiple distinct epigenetic abnormalities that lead to the silencing of tumor suppressor genes in MPM and could serve as diagnostic or prognostic targets. [Cancer Res 2009;69(23):9073-82]

Malignant pleural mesothelioma (MPM) is an asbestos-related

No abstract

Malignant pleural mesothelioma (MPM) is an aggressive neoplasm associated with asbestos exposure. Although expression and activation of receptor tyrosine kinases (RTKs), including MET, have been reported in most MPM, specific RTK inhibitors showed less than the expected response in MPM cells. To determine whether the lack of response of MET inhibitors was due to cooperation with other RTKs, we determined activation status of MET and other RTKs, including epidermal growth factor receptor (EGFR) family of 20 MPM cell lines, and tested whether dual RTK inhibition is an effective therapeutic strategy. We detected MET upregulation and phosphorylation (thus indicating activation) in 14 (70%) and 13 (65%) cell lines, but treatment with MET-specific inhibitors showed weak or modest effect of suppression in most of the cell lines. Phospho-RTK array analysis revealed that MET was simultaneously activated with other RTKs, including EGFR, ErbB2, ErbB3 and platelet-derived growth factor receptor-beta. Combination of MET and EGFR inhibitors triggered stronger inhibition on cell proliferation and invasion of MPM cells than that of each in vitro. These results indicated that coactivation of RTKs was essential in mesothelioma cell proliferation and/or survival, thus suggesting that simultaneous inhibition of RTKs may be a more effective strategy for the development of molecular target therapy for MPM.

ObjectivesImmunological parameters and nutritional status influence the outcome of patients with malignant tumors. A prognostic nutritional index, calculated using serum albumin levels and peripheral lymphocyte count, has been used to assess prognosis for various cancers. This study aimed to investigate whether this prognostic nutritional index affects overall survival and the incidence of postoperative complications in patients with completely resected non-small cell lung cancer.MethodsWe retrospectively reviewed the medical records of 409 patients with non-small cell lung cancer who underwent complete resection between 2005 and 2007 at the Aichi Cancer Center.ResultsThe 5-year survival rates of patients with high (≥50) and low (<50) prognostic nutritional indices were 84.4% and 70.7%, respectively (p = 0.0011). Univariate analysis showed that gender, histology, pathological stage, smoking history, serum carcinoembryonic antigen levels, and prognostic nutritional index were significant prognostic factors. Multivariate analysis identified pathological stage and the prognostic nutritional index as independent prognostic factors. The frequency of postoperative complications tended to be higher in patients with a low prognostic nutritional index.ConclusionsThe prognostic nutritional index is an independent prognostic factor for survival of patients with completely resected non-small cell lung cancer.

No abstract