Rsk4 And Abnormal Brca1 Gene Methylation In The Pathogenesis Of Breast Cancer Research

Part1The P90ribosomal S6kinase4is epigenetically inactivated by promoter methylation in human breast canerObjective:The P90ribosomal S6kinase4is one of family members of serine/threonine kinases. It is activated or inhibited by downstream of the Ras-MAPKs pathway. RSK4may be involved in the occurrence of breast cancer, but RSK4what is an oncogene or tumor suppressor gene, is still inconclusive. The study was aimed to investigate the relationship between RSK4gene expression and its methylation status, and its potential role in ras signaling in breast cancer and adjacent noncancerous tissues.Methods:The expression difference of RSK4mRNA in paired breast cancer, adjacent normal tissues were detected by the method of Real-time PCR. RSK4gene methylation exent in paired breast cancer, adjacent normal tissues were analyzed by BSP (bisulfite sequencing PCR). Correlation of RSK4methylation status with clinicopathologic characteristic was evaluated in breast cancer tissues.Results:RSK4mRNA expression in49breast cancer tissues were lower than those in paired adjacent tissues. There is a significant statistical difference (p=0.002). RSK4mRNA expression was related with in breast primary tumor size (p=0.022) and clinical stage (p=0.002),while there was no relation between RSK4mRNA expression with age, menopause, pathological type, lymph node metastasis, ER, PR, CerbB-2state and Ki-67index size. Frequentcy of RSK4promoter methylation in breast cancers was significantly hinger than adjacent tissues (p=0.009); RSK4gene methylation status was negatively correlated with mRNA expression (p=0.005);RSK4methylation was also associated with all clinicopathological featuresConclusions:These results indicate that silencing of RSK4due to promoter hypermethylation is a frequent event. RSK4may be a valuable biomarker for the study of breast cancer carcinogenesis and progression. Part2Frequent epigenetic inactivation of breast cancer susceptibility gene1by promoter methylation in human breast cancerObjective:BRCA1is a susceptibility gene that has a genetic predisposition for breast cancer, BRCA1gene mutations are closely related with familial hereditary breast, but rarely found mutations of the BRCA1gene in sporadic breast cancer. Accroding by our former studies, decreased expression of BRCA1mRNA and protein were dected in some sporadic breast cancers. Abbrent methylation of DNA promoter CpG islands is one of the mechanisms that tumor suppressor gene expression and function loss. The aim of the present study was to investigate BRCA1gene expression profile, methylation status and clinical significances in sporadic breast cancers.Methods:The expression difference of BRCA1mRNA in paired breast cancer, adjacent normal tissues were detected by the method of Real-time PCR. BRCA1gene methylation exent in paired breast cancer, adjacent normal tissues were analyzed by BSP (bisulfite sequencing PCR). Correlation of BRCA1methylation status with clinicopathologic characteristic was evaluated in breast cancer tissues.Results:BRCA1mRNA expression in49breast cancer tissues were lower than those in paired adjacent tissues. There is a significant statistical difference (p=0.001). BRCAlmRNA expression was not related with age, menopause, primary tumor size, clinical stage, lymph node metastasis, ER, PR, CerbB-2state and Ki-67index size. Frequentcy of BRCAl promoter methylation in breast cancers was significantly hinger than adjacent tissues (p=0.007); BRCA1gene methylation status was negatively correlated with mRNA expression (p>=0.029); BRCA1methylation was also associated with all clinicopathological features.Conclusions:The expression silence of BRCA1gene in part of sporadic breast cancers may due to promoter CpG island methylation rather than gene mutations. The subset of patients with hypermethylated BRCA1displayed more favorable clinical status. BRCA1gene is not only in family of hereditary breast cancers but also in sporadic breast cancer may still be a valuable molecular marker. Part3Detection of promoter methylation of RSK4and BRCA1in plasma DNA of sporadic breast cancerObjective:Detecting epigenetic molecular markers of important genes in circling DNA is studied by many researchers. The aim of this study is to investigate methylation status of RSK4and BRCA1genes with different carcinogenic mechanisms; to evaluate the relationship between the main clinicopathological features and them in sporadic breast cancers.Methods:Using BPS method, we analyzed methylation status of RSK4and BRCA1genes in60plasma DNA samples including45sporadic breast tumors and15benign breast diseases.Results:The slight difference of methylation status in plasma DNA samples of RSK4and BRCA1genes in breast tumors and benign breast diseases was detected; Methylation status in plasma DNA samples of RSK4and BRCA1genes both were not correlation with main clinicopathological features. Combination detection methylation of RSK4and BRCA1in plasma DNA were not use for screening breast cancer risk.Conclusions:Methylation of the two genes were slightly different between breast caners and benign diseases in plasma DNA, and n linked to various clinicopathological features of breast cancer; both genes methylation in breast tumors may indicate a aggressive phenotype. Detection of hypermethylation in plasma DNA using a combination of epigenetic markers may be useless for identifying patients at higll risk for breast cancer at present.