探討Securin及miR-1246在人類大腸癌細胞的功能

Abstract

Securin被認為是一種人類的前致癌基因，然而securin在調控腫瘤形成及轉移作用仍不清楚。在本研究中，我們主要探討securin在調控大腸癌所扮演的角色。我們利用人類cDNA微陣列分析法，篩選分析在野生型、securin基因缺失型及p53基因缺失型的HCT116人類大腸癌細胞中，從29,187個基因的表現差異，選出具有潛力的securin下游基因caveolin-1。比較野生型及securin基因剔除的大腸癌細胞，我們發現在securin基因缺失的細胞中，致癌因子caveolin-1的表達量會明顯下降。過度表現securin時會增加磷酸化caveolin-1的表現並促進caveolin-1由細胞膜轉位至細胞質的作用。相反的， 在securin基因缺失的大腸癌細胞中，抑癌基因E-cadherin的表達量會明顯上升，而在大腸癌細胞中過度表現securin時，E-cadherin的表現量會受到抑制，我們驗證caveolin-1和E-cadherin在大腸癌的腫瘤形成及轉移過程中扮演相反的角色。此外我們利用人類微小RNA之微陣列方法，發現在securin基因剔除的大腸癌細胞中，miR-1246的表現會明顯降低，而大量表現miR-1246時會促進大腸癌細胞的細胞凋亡作用，且會抑制細胞生長，此外，miR-1246會抑制securin及N-cadherin的表現但增加p53的表達，我們推測miR-1246在大腸癌細胞的角色為腫瘤抑制因子。本研究對securin及miR-1246在大腸癌的調控提出了新的觀點，將可應用未來發展有潛力的大腸癌之治療策略。

Securin has been proposed as a human proto-oncogene; however, the regulation of securin in tumorigenesis and metastasis remains poorly understood. In this study, we investigate the precise role of securin in regulating the human colorectal cancer (CRC). We have screened a potential securin downstream gene, caveolin-1, using the differential gene expression profiles from 29,187 genes in HCT116 wild-type, securin-knockout and p53-knockout CRC cells by human cDNA microarrays. The oncogenic caveolin-1 was reduced in the securin-knockout cells by comparison with the wild-type CRC cells. Over-expression of securin induced the level of phosphorylated caveolin-1 and promoted the translocation of caveolin-1 proteins from the cell membrane to cytoplasm. Conversely, the tumor suppressor E-cadherin was elevated in the securin-knockout CRC cells. The over-expression of securin reduced the E-cadherin expression in CRC cells. These findings indicate that securin can regulate caveolin-1 and E-cadherin, which display the opposite role on the tumorigenesis and metastasis in CRC. In addition, we found a novel miR-1246 that down-regulated in the securin-knockout CRC cells using the differential expression of human miRNA arrays. Over-expression of miRNA-1246 induced apoptosis and growth inhibition in CRC cells. Besides, miR-1246 mediated the down-regulation of securin and N-cadherin but conversely up-regulated the p53 expression. We suggest the role of miR-1246 that is a tumor suppressor in CRC. This study provides the novel insight on the regulation of securin and miR-1246 in CRC that may develop the potential applications in the CRC therapy.