Department of Oncology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, China.
J Exp Clin Cancer Res. 2020 Jan 28;39(1):23. doi: 10.1186/s13046-019-1504-5.
Tripartite motif-containing proteins (TRIM) play a crucial role in carcinogenesis. Little attention has been focused on the possible functions of TRIM6 on carcinogenesis.
The expression levels of TRIM6 were assessed in colorectal cancer (CRC) samples. TRIM6 expression was knocked down in CRC cell lines, and subjected to Cell counting kit-8 (CCK-8), bromodeoxyuridine (BrdU) incorporation and cell cycle assays. Immunoprecipitation and proteomics analysis was performed to identify potential associated proteins of TRIM6.
TRIM6 expression was up-regulated in CRC samples and TRIM6 expression may be an independent prognostic marker for CRC. Knocking down TRIM6 expression suppressed CRC cell proliferation, induced cell cycle arrested at G2/M phase and increased sensitivity to 5-fluorouracil and oxaliplatin. TIS21, an anti-proliferative protein involved in the regulation of G2/M arrest, was identified as an interaction partner of TRIM6. Moreover, CRC cells with TRIM6 overexpression showed decreased TIS21 protein stability. TIS21 ubiquitination was increased in CRC cells overexpressing TRIM6, but not in those overexpressing TRIM6 E3 catalytic mutant (C15A). Further, Lys5 was essential for TRIM6 mediated TIS21 ubiquitination. TIS21 overexpression reversed the induced effects of TRIM6 overexpression on CRC cell proliferation, and the levels of forkhead box M1 (FoxM1), phosphorylated FoxM1, Cyclin B1 and c-Myc. Thiostrepton, a specific inhibitor for FoxM1, was less effective in anti-proliferative activity against CRC cells with lower level of TRIM6 in vitro and in vivo.
Our study suggests that TRIM6 promotes the progression of CRC via TIS21/FoxM1.
三结构域蛋白（TRIM）在致癌作用中起着至关重要的作用。TRIM6 对致癌作用的可能功能尚未得到关注。
评估结直肠癌（CRC）样本中 TRIM6 的表达水平。在 CRC 细胞系中敲低 TRIM6 表达，并进行细胞计数试剂盒-8（CCK-8）、溴脱氧尿苷（BrdU）掺入和细胞周期测定。进行免疫沉淀和蛋白质组学分析以鉴定 TRIM6 的潜在相关蛋白。
TRIM6 在 CRC 样本中表达上调，TRIM6 表达可能是 CRC 的独立预后标志物。敲低 TRIM6 表达可抑制 CRC 细胞增殖，诱导细胞周期停滞在 G2/M 期，并增加对 5-氟尿嘧啶和奥沙利铂的敏感性。TIS21 是一种参与 G2/M 期阻滞调节的抗增殖蛋白，被鉴定为 TRIM6 的相互作用伙伴。此外，过表达 TRIM6 的 CRC 细胞显示 TIS21 蛋白稳定性降低。过表达 TRIM6 的 CRC 细胞中 TIS21 的泛素化增加，但过表达 TRIM6 E3 催化突变体（C15A）的细胞中则没有。进一步的研究表明，Lys5 是 TRIM6 介导的 TIS21 泛素化所必需的。TIS21 的过表达逆转了 TRIM6 过表达对 CRC 细胞增殖的诱导作用，以及叉头框 M1（FoxM1）、磷酸化 FoxM1、细胞周期蛋白 B1 和 c-Myc 的水平。体外和体内实验表明，FoxM1 的特异性抑制剂硫氧还蛋白在 TRIM6 水平较低的 CRC 细胞中的抗增殖活性方面效果较差。
本研究表明，TRIM6 通过 TIS21/FoxM1 促进 CRC 的进展。
