肿瘤转移抑制基因LASS2/TMSG1S248A突变体通过增加ATP6V0C表达促进前列腺癌的侵袭

目的: 探讨LASS2/TMSG1及其突变体在前列腺癌细胞增殖、迁移和侵袭中的分子作用机制。方法: 构建表达LASS2/TMSG1全长及其4个突变体的pcDNA3真核表达载体,并稳定转染到高转移潜能前列腺癌PC-3M-1E8细胞系中;采用qPCR和Western blot法鉴定稳定转染效果,并分析不同点突变体对LASS2/TMSG1和ATP6V0C表达量的影响;采用生长曲线测定、四甲基偶氮唑蓝(MTT)掺入实验、软琼脂集落形成实验、细胞划痕修复实验、Matrigel穿膜侵袭实验和流式细胞术研究LASS2/TMSG1及其4个点突变体的细胞生物学功能,并通过免疫双重荧光染色分析LASS2/TMSG1不同突变体和ATP6V0C的相互作用情况。结果: qPCR和Western blot检测显示LASS2/TMSG1 S248A组较LASS2/TMSG1野生型组ATP6V0C表达增加了3倍(P<0.05), 且免疫双重荧光染色结果显示LASS2/TMSG1 S248A组ATP6V0C表达明显增加;与LASS2/TMSG1野生型组相比,LASS2/TMSG1 S248A组的细胞增殖能力、锚着不依赖生长能力、细胞迁移能力 (细胞迁移率从35.3%±3.2%增加到70.3%±3%)和侵袭能力(穿膜细胞数从50.0±3.2增加到203.0±6.5)明显提高(P<0.05), G0/G1期比例增加(从51.0%增加到85.4%,P<0.05),但细胞凋亡率亦明显升高(从7%增加到15.1%,P<0.05)。结论: LASS2 /TMSG1第248位丝氨酸突变为丙氨酸后(S248A)能促进前列腺癌细胞增殖、迁移和侵袭能力,其分子机制可能是LASS2/TMSG S248A使ATP6V0C表达量增加,进而促进前列腺癌的侵袭,提示LASS2/TMSG1蛋白第248位丝氨酸是抑制前列腺癌侵袭的重要功能位点。

Novel tumor metastasis suppressorgene LASS2/TMSG1 S248A mutant promotes invasion of prostate cancer cells through increasing ATP6V0C expression

Objective: LASS2/TMSG1 gene is a novel tumor metastasis suppressor gene cloned from human prostate cancer cell line PC-3M in 1999 by Department of Pathology,Peking University of Basic Medical Sciences. It was found out that protein encoded by LASS2/TMSG1 could interact with the c subunit of vacuolar-ATPase (ATP6V0C). In this study, we explored the effect of LASS2/TMSG1 and its mutants on proliferation, migration and invasion of human prostate cancer cells and its molecular mechanism.Methods: We constructed four LASS2/TMSG1 mutants and stably transfected the variants to human prostate cancer cell line PC-3M-1E8 cell with high metastatic potential. The stable transfectants were identified by qPCR and Western blot through analyzing the expression of LASS2/TMSG1 and ATP6V0C, the cell biology functions of LASS2/TMSG1 and its four mutants were studied using growth curve,MTT assay, soft agar colony formation assay, wound migration assay, Matrigel invasion study and flow cytometry. Furthermore, immunofluorescence was used to analysis the interaction of LASS2/ TMSG1 mutants and ATP6V0C.Results: LASS2/TMSG1 mRNA and protein in LASS2/TMSG1 group and Mut1-Mut4 groups were higher than that in Vector group; Western blot showed that ATP6V0C protein in LASS2/TMSG1 wild group was lower than that in Vector group, but ATP6V0C protein in LASS2/TMSG1 S248A group was obviously higher than that in Vector group. MTT test and growth curve assay showed growth ability in LASS2/TMSG1 S248A group was increasing compared with other groups from day 5. Soft Agar colony formation experiment showed anchor independent growth ability in LASS2/TMSG1 S248A group was higher than those in the other groups (P<0.05), Cell migrations (from 35.3%±3.2% to 70.3%±3%) in LASS2/TMSG1 S248A group was increasing compared with LASS2/TMSG1 wild group (P<0.01), and more cells passed through Matrigel in LASS2/TMSG1 S248A group compared with LASS2/TMSG1 wild group (from 50±3.2 to 203±6.5, P<0.01), the apoptosis rate in LASS2/TMSG1 S248A group was obviously higher than that in LASS2/TMSG1 wild group (from 7% to 15.1%, P<0.05), and the G0/G1 ratio in LASS2/TMSG1 S248A group was obviously higher than that in LASS2/TMSG1 wild group (from 51.0% to 85.4%). Furthermore, double immunofluorescent staining observed the colocalization between ATP6V0C and LASS2/TMSG1 protein and its mutations, the expression of ATP6V0C in LASS2/TMSG1 S248A group increased significantly compared with the other groups.Conclusion: LASS2/TMSG1 S248A promotes proliferation, migration and invasion of prostate cancer cells through increasing ATP6V0C expression, suggesting that aa248-250 is an important function site for LASS2/TMSG1 in invasion suppression of prostate cancer cells.