RESUMO
Activation of the Wnt/ß-catenin signaling pathway is common in various human cancers. The aim of this study was to investigate the expression of 2 members of the Wnt family (WIF-1 and Wnt5a) in sporadic and hereditary breast cancer tissues. WIF-1, is a secreted antagonist that binds Wnt ligands, and therefore inhibits the canonical Wnt/ß-catenin pathway. Wnt5a is one of the members of the noncanonical Wnt family that mainly acts through calcium signaling pathway. The expression of WIF-1 was analyzed by methylation-specific PCR and RT-PCR, and the level of Wnt5a ligand was quantified by RT-QPCR in breast cancer tissues. Methylation of WIF-1 was detected in 71.3 % and 81.8 % of sporadic and hereditary cases, respectively. Aberrant methylation of WIF-1 was associated with advanced TNM stage and triple negative cases in sporadic breast carcinoma (p=0.001 and p=0.037, respectively). In hereditary cases, methylation of WIF-1 correlated with age at diagnosis (p=0.027) and p53 status (p=0.035). Regarding patients' survival, WIF-1 methylated promoter conferred a reduced overall survival rate, and particularly in a group of patients with advanced TNM stage (p log rank=0.006). Furthermore, aberrant CpG methylation of the WIF-1 promoter was significantly associated with transcriptional silencing of this tumor suppressor gene in sporadic breast cancer tissues (p=0.036). On the other hand, in sporadic tumor tissues, the level of Wnt5a mRNA was significantly lower compared to normal tissues (p=0.031) and lower still in those showing more aggressive behavior, suggesting that Wnt5a, a ligand involved in the noncanonical Wnt/ß-catenin pathway, could act as a tumor suppressor gene in breast cancer.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Neoplasias da Mama/genética , Metilação de DNA , Regulação Neoplásica da Expressão Gênica , Proteínas Proto-Oncogênicas/genética , Proteínas Repressoras/genética , Proteínas Wnt/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias da Mama/mortalidade , Neoplasias da Mama/patologia , Feminino , Inativação Gênica , Humanos , Técnicas Imunoenzimáticas , Masculino , Pessoa de Meia-Idade , Gradação de Tumores , Metástase Neoplásica , Estadiamento de Neoplasias , Prognóstico , Regiões Promotoras Genéticas/genética , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais , Taxa de Sobrevida , Células Tumorais Cultivadas , Tunísia , Proteína Wnt-5a , Adulto JovemRESUMO
Aberrant methylation of the CpG islands in promoter regions is one of the mechanisms for inactivation of tumor suppressor genes in many human cancers including breast carcinoma. In this study, we aimed to assess, by methylation-specific PCR, the CpG methylation pattern of the UCHL1 promoter in 94 sporadic and 44 hereditary breast cancers from Tunisian patients. The percentage of UCHL1 methylation was 67 % in sporadic and 82 % in hereditary breast cancer cases. In sporadic cases, UCHL1 methylation correlated with poor response to treatment (P = 0.042) and progesterone receptor status (P = 0.036), whereas in patients with hereditary predisposition, the only significant association was found with Her2 expression (P = 0.024). Moreover, in patients with sporadic breast cancer, the UCHL1 unmethylated pattern conferred a prolonged overall survival time in particular in the group of patients with advanced TNM stage of the disease (P log rank = 0.04). Aberrant CpG methylation of the UCHL1 promoter was significantly associated with transcriptional silencing of this tumor suppressor gene in sporadic breast cancer tissues (P = 0.001). On the other hand, the UCHL1 unmethylated pattern correlated with P53 positivity in primary sporadic tumors (P = 0.032), supporting the functional link between the two tumor suppressors in breast tumorigenesis.
