Hinrichsen Inga, Ernst Benjamin Philipp, Nuber Franziska, Passmann Sandra, Schäfer Dieter, Steinke Verena, Friedrichs Nicolaus, Plotz Guido, Zeuzem Stefan, Brieger Angela
Medical Clinic I, Biomedical Research Laboratory, Goethe-University, Frankfurt a,M, Germany.
Mol Cancer. 2014 Jan 24;13:11. doi: 10.1186/1476-4598-13-11.
Defects in the DNA mismatch repair (MMR) protein MLH1 are frequently observed in sporadic and hereditary colorectal cancers (CRC). Affected tumors generate much less metastatic potential than the MLH1 proficient forms. Although MLH1 has been shown to be not only involved in postreplicative MMR but also in several MMR independent processes like cytoskeletal organization, the connection between MLH1 and metastasis remains unclear. We recently identified non-erythroid spectrin αII (SPTAN1), a scaffolding protein involved in cell adhesion and motility, to interact with MLH1. In the current study, the interaction of MLH1 and SPTAN1 and its potential consequences for CRC metastasis was evaluated.
Nine cancer cell lines as well as fresh and paraffin embedded colon cancer tissue from 12 patients were used in gene expression studies of SPTAN1 and MLH1. Co-expression of SPTAN1 and MLH1 was analyzed by siRNA knock down of MLH1 in HeLa, HEK293, MLH1 positive HCT116, SW480 and LoVo cells. Effects on cellular motility were determined in MLH1 deficient HCT116 and MLH1 deficient HEK293T compared to their MLH1 proficient sister cells, respectively.
MLH1 deficiency is clearly associated with SPTAN1 reduction. Moreover, siRNA knock down of MLH1 decreased the mRNA level of SPTAN1 in HeLa, HEK293 as well as in MLH1 positive HCT116 cells, which indicates a co-expression of SPTAN1 by MLH1. In addition, cellular motility of MLH1 deficient HCT116 and MLH1 deficient HEK293T cells was impaired compared to the MLH1 proficient sister clones. Consequently, overexpression of SPTAN1 increased migration of MLH1 deficient cells while knock down of SPTAN1 decreased cellular mobility of MLH1 proficient cells, indicating SPTAN1-dependent migration ability.
These data suggest that SPTAN1 levels decreased in concordance with MLH1 reduction and impaired cellular mobility in MLH1 deficient colon cancer cells. Therefore, aggressiveness of MLH1-positive CRC might be related to SPTAN1.
DNA错配修复（MMR）蛋白MLH1的缺陷在散发性和遗传性结直肠癌（CRC）中经常被观察到。受影响的肿瘤产生的转移潜能远低于MLH1功能正常的肿瘤。尽管已表明MLH1不仅参与复制后错配修复，还参与细胞骨架组织等多个与错配修复无关的过程，但MLH1与转移之间的联系仍不清楚。我们最近鉴定出非红细胞血影蛋白αII（SPTAN1），一种参与细胞黏附和运动的支架蛋白，可与MLH1相互作用。在本研究中，评估了MLH1与SPTAN1的相互作用及其对结直肠癌转移的潜在影响。
使用9种癌细胞系以及12例患者的新鲜和石蜡包埋的结肠癌组织进行SPTAN1和MLH1的基因表达研究。通过在HeLa、HEK293、MLH1阳性的HCT116、SW480和LoVo细胞中敲低MLH1来分析SPTAN1和MLH1的共表达情况。分别比较MLH1缺陷的HCT116和MLH1缺陷的HEK293T细胞与其MLH1功能正常的姐妹细胞对细胞运动的影响。
MLH1缺陷与SPTAN1减少明显相关。此外，敲低MLH1的siRNA降低了HeLa、HEK293以及MLH1阳性的HCT116细胞中SPTAN1的mRNA水平，这表明MLH1与SPTAN1共表达。此外，与MLH1功能正常的姐妹克隆相比，MLH1缺陷的HCT116和MLH1缺陷的HEK293T细胞的细胞运动能力受损。因此，SPTAN1的过表达增加了MLH1缺陷细胞的迁移，而敲低SPTAN1则降低了MLH1功能正常细胞的细胞运动性，表明迁移能力依赖于SPTAN1。
这些数据表明，SPTAN1水平随MLH1减少而降低，且MLH1缺陷的结肠癌细胞的细胞运动性受损。因此，MLH1阳性结直肠癌的侵袭性可能与SPTAN1有关。
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