A tumor suppressor gene, CADM1, encoding an immunoglobulin superfamily cell adhesion molecule, is inactivated in various cancers, including non-small-cell lung cancer (NSCLC). Although promoter methylation is one of t...A tumor suppressor gene, CADM1, encoding an immunoglobulin superfamily cell adhesion molecule, is inactivated in various cancers, including non-small-cell lung cancer (NSCLC). Although promoter methylation is one of the mechanisms to suppress CADM1 expression, about half of tumors lacking CADM1 expression do not show methylation of the gene promoter. We herein investigated the possible involvement of microRNA (miRNA) in the down-regulation of CADM1. Using computational algorithms, miR-214 and miR-375 were identified as candidate miRNAs targeting CADM1. A luciferase reporter assay demonstrated that miR-214 and miR-375 repressed the promoter activity through 3’-UTR of CADM1. Quantitative RT-PCR analysis demonstrated that miR-214 and miR-375 was highly expressed in 21 (62%) and 17 cases (50%) of 34 primary NSCLCs. Notably, increased expression of miR-214 was preferentially observed in tumors with advanced pathological stages and in those lacking CADM1 expression but were not associated with the promoter methylation, suggesting that miR-214-mediated silencing would be another mechanism to suppress CADM1 expression. On the other hand, introduction of miR-214 or miR-375 into NSCLC cells decreased CADM1 protein expression. Furthermore, overexpression of miR-214 enhanced anchorage-independent growth of NSCLC cells, A549, whereas transfection of miRNA inhibitor, miR-214 or miR-375, significantly suppressed the in vitro wound healing activity of HCC827 cells. These findings suggest that overexpression of miR-214 and miR-375 could participate in the malignant features of NSCLC through down-regulating CADM1 and would provide a potential target for the treatment of a subset of NSCLC.展开更多
Objective: Targeting mutated EGFR by EGFR-tyrosine kinase inhibitors (EGFR-TKI) is a potent approach to a subset of non-small cell lung cancer (NSCLC). However, the response to EGFR-TKI varies in individual cases even...Objective: Targeting mutated EGFR by EGFR-tyrosine kinase inhibitors (EGFR-TKI) is a potent approach to a subset of non-small cell lung cancer (NSCLC). However, the response to EGFR-TKI varies in individual cases even among tumors carrying the same?EGFR?mutation, suggesting the involvement of modifying factors. To characterize possible modifiers, we examined mutation state of the?EGFR?and the?KRAS?genes in Japanese NSCLC and compared them with the methylation state of lung tumor suppressors, the?CADM1 and?4.1B,?whose products have potentials to modify the functions of EGFR or KRAS. Materials and methods: A total of 103 Japanese NSCLC and 11 NSCLC cell lines were examined. Genomic DNA of exons 18–21 of the?EGFR?and exons 1 and 2 of the?KRAS?were amplified by polymerase chain reaction (PCR), followed by single-strand conformation polymorphism analysis and direct sequencing. Methylation status of gene promoters in NSCLC cells were examined by methylation-specific PCR. Results: Mutations of the?EGFR?and?KRAS?were detected mutually exclusively in 27 and 11 out of 103 NSCLC cases, respectively.?EGFR?mutations were observed exclusively in adenocarcinoma (27 of 69, 41%) and preferentially in tumors from female and non-smokers (p < 0.00001). Eight (30%) and 12 (44%) of 27 tumors carrying mutated?EGFR?and 4 (36%) and 8 (73%) of 11 tumors carrying mutated?KRAS?showed methylation of the?CADM1 and 4.1B, respectively.?EGFR-mutated tumors with methylation of either?CADM1 or 4.1B?showed more malignant features than those with unmethylated?CADM1 and 4.1B?(p < 0.05). Conclusion: Methylation state of the?CADM1 and?4.1B?are independent of the mutation status of the?EGFR?or?KRAS?but play roles in the malignant progression of NSCLC. Integration of epigenetic information would be useful for identifying possible modifiers to predict the response or recurrence of lung adenocarcinoma to the EGFR-TKI therapy.展开更多
文摘A tumor suppressor gene, CADM1, encoding an immunoglobulin superfamily cell adhesion molecule, is inactivated in various cancers, including non-small-cell lung cancer (NSCLC). Although promoter methylation is one of the mechanisms to suppress CADM1 expression, about half of tumors lacking CADM1 expression do not show methylation of the gene promoter. We herein investigated the possible involvement of microRNA (miRNA) in the down-regulation of CADM1. Using computational algorithms, miR-214 and miR-375 were identified as candidate miRNAs targeting CADM1. A luciferase reporter assay demonstrated that miR-214 and miR-375 repressed the promoter activity through 3’-UTR of CADM1. Quantitative RT-PCR analysis demonstrated that miR-214 and miR-375 was highly expressed in 21 (62%) and 17 cases (50%) of 34 primary NSCLCs. Notably, increased expression of miR-214 was preferentially observed in tumors with advanced pathological stages and in those lacking CADM1 expression but were not associated with the promoter methylation, suggesting that miR-214-mediated silencing would be another mechanism to suppress CADM1 expression. On the other hand, introduction of miR-214 or miR-375 into NSCLC cells decreased CADM1 protein expression. Furthermore, overexpression of miR-214 enhanced anchorage-independent growth of NSCLC cells, A549, whereas transfection of miRNA inhibitor, miR-214 or miR-375, significantly suppressed the in vitro wound healing activity of HCC827 cells. These findings suggest that overexpression of miR-214 and miR-375 could participate in the malignant features of NSCLC through down-regulating CADM1 and would provide a potential target for the treatment of a subset of NSCLC.
文摘Objective: Targeting mutated EGFR by EGFR-tyrosine kinase inhibitors (EGFR-TKI) is a potent approach to a subset of non-small cell lung cancer (NSCLC). However, the response to EGFR-TKI varies in individual cases even among tumors carrying the same?EGFR?mutation, suggesting the involvement of modifying factors. To characterize possible modifiers, we examined mutation state of the?EGFR?and the?KRAS?genes in Japanese NSCLC and compared them with the methylation state of lung tumor suppressors, the?CADM1 and?4.1B,?whose products have potentials to modify the functions of EGFR or KRAS. Materials and methods: A total of 103 Japanese NSCLC and 11 NSCLC cell lines were examined. Genomic DNA of exons 18–21 of the?EGFR?and exons 1 and 2 of the?KRAS?were amplified by polymerase chain reaction (PCR), followed by single-strand conformation polymorphism analysis and direct sequencing. Methylation status of gene promoters in NSCLC cells were examined by methylation-specific PCR. Results: Mutations of the?EGFR?and?KRAS?were detected mutually exclusively in 27 and 11 out of 103 NSCLC cases, respectively.?EGFR?mutations were observed exclusively in adenocarcinoma (27 of 69, 41%) and preferentially in tumors from female and non-smokers (p < 0.00001). Eight (30%) and 12 (44%) of 27 tumors carrying mutated?EGFR?and 4 (36%) and 8 (73%) of 11 tumors carrying mutated?KRAS?showed methylation of the?CADM1 and 4.1B, respectively.?EGFR-mutated tumors with methylation of either?CADM1 or 4.1B?showed more malignant features than those with unmethylated?CADM1 and 4.1B?(p < 0.05). Conclusion: Methylation state of the?CADM1 and?4.1B?are independent of the mutation status of the?EGFR?or?KRAS?but play roles in the malignant progression of NSCLC. Integration of epigenetic information would be useful for identifying possible modifiers to predict the response or recurrence of lung adenocarcinoma to the EGFR-TKI therapy.
