Genetic and epigenetic mechanisms involved in regulation of STEAP1 gene expression in LNCaP prostate cancer cells

• Autor(a) principal: Sousa, Inês Margarida Marques de
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/6289
• topic: Cancro da Próstata; Epigenética; Genética; Steap1; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Química

Prostate cancer is the second most frequently diagnosed type of cancer and the fifth leading cause of cancer death in men worldwide. Prostate carcinogenesis is characterized by progressive alterations in genetic and epigenetic mechanisms that deregulate gene expression. The Six Transmembrane Epithelial Antigen of the Prostate 1 (STEAP1) gene encodes a protein with six transmembrane domains. In normal tissues, STEAP1 expression is very low but is overexpressed in several human cancers, mainly in prostate cancer. Some studies have indicated that STEAP1 overexpression seems to promote cell growth, suggesting that STEAP1 may act as an oncogene. Previous studies demonstrated that STEAP1 mRNA and protein have higher stability in LNCaP prostate cancer cell lines when compared with PNT1A non-neoplastic prostate cell lines, possibly due to post-transcriptional and post-translational modifications. However, these alterations do not justify the overexpression of STEAP1 in tumor cells, suggesting that other mechanisms may be involved. Therefore, the aim of this study was to explore the hypothesis that genetic and / or epigenetic alterations may be involved in overexpression of STEAP1. In order to evaluate genetic alterations in the STEAP1 gene sequence, the promoter region of STEAP1 in LNCaP and PNT1A cells was sequenced. To study the involvement of epigenetic mechanisms, the methylation patterns of STEAP1 in PNT1A and LNCaP cells were compared. In addition, the effect of treatment with DNA methyltransferases (DNMT) and histone deacetylases (HDAC) inhibitors on STEAP1 mRNA expression in PNT1A cells was evaluated. The sequence analysis of the promoter region of STEAP1 revealed some differences in both PNT1A and LNCaP cells when compared with the available genomic sequence. In silico analysis of the identified variants revealed several alterations in the transcription factors (TF) that can bind to each allelic variant including the binding of transcriptional activators to the altered allele of the variants. The analysis of the methylation pattern of STEAP1 gene in PNT1A and LNCaP cells showed differences in the promoter region near the transcription start site. The treatment with 5-Aza-2’-deoxycytidine (DNMT inhibitor) induced a slight increase in STEAP1 mRNA expression (3 fold-variation in comparison with control group, p<0.01) while the treatment with both 5-Aza-2’-deoxycytidine and TSA (HDAC inhibitor) induced a marked increase in STEAP1 mRNA expression (15 fold-variation relatively to control, p<0.001). The difference in the methylation pattern of STEAP1 between PNT1A and LNCaP cells, along with the increased STEAP1 mRNA expression in response to DNMT and HDAC inhibitors, indicates that STEAP1 gene expression seems to be regulated by epigenetic mechanisms.