Clinical Research Unit, Department of Obstetrics and Gynecology, Technical University of Munich, Ismaninger Str, 22, Munich 81675, Germany.
Mol Cancer. 2012 Aug 24;11:62. doi: 10.1186/1476-4598-11-62.
Rab proteins constitute a large family of monomeric GTP-binding proteins that regulate intracellular vesicle transport. Several Rab proteins, including rab31, have been shown to affect cancer progression and are related with prognosis in various types of cancer including breast cancer. Recently, the gene encoding rab31 was found to be overexpressed in estrogen receptor-positive breast cancer tissue. In a previous study we found a significant association of high rab31 mRNA expression with poor prognosis in node-negative breast cancer patients. In the present study, we aimed to investigate the impact of rab31 (over)-expression on important aspects of tumor progression in vitro and in vivo.
Breast cancer cells displaying low (MDA-MB-231) or no (CAMA-1) endogenous rab31 expression were stably transfected with a rab31 expression plasmid. Batch-transfected cells as well as selected cell clones, expressing different levels of rab31 protein, were analyzed with regard to proliferation, cell adhesion, the invasive capacity of tumor cells, and in vivo in a xenograft tumor model. Polyclonal antibodies directed to recombinantly expressed rab31 were generated and protein expression analyzed by immunohistochemistry, Western blot analysis, and a newly developed sensitive ELISA.
Elevated rab31 protein levels were associated with enhanced proliferation of breast cancer cells. Interestingly, weak to moderate overexpression of rab31 in cell lines with no detectable endogenous rab31 expression was already sufficient to elicit distinct effects on cell proliferation. By contrast, increased expression of rab31 in breast cancer cells led to reduced adhesion towards several extracellular matrix proteins and decreased invasive capacity through Matrigel(TM). Again, the rab31-mediated effects on cell adhesion and invasion were dose-dependent. Finally, in a xenograft mouse model, we observed a significantly impaired metastatic dissemination of rab31 overexpressing MDA-MB-231 breast cancer cells to the lung.
Overexpression of rab31 in breast cancer cells leads to a switch from an invasive to a proliferative phenotype as indicated by an increased cell proliferation, reduced adhesion and invasion in vitro, and a reduced capacity to form lung metastases in vivo.
Rab 蛋白构成了一个庞大的单体 GTP 结合蛋白家族，调节细胞内囊泡运输。几种 Rab 蛋白，包括 rab31，已被证明影响癌症的进展，并与各种类型的癌症包括乳腺癌的预后相关。最近，发现 rab31 基因在雌激素受体阳性乳腺癌组织中过度表达。在之前的研究中，我们发现 rab31 mRNA 表达水平高与淋巴结阴性乳腺癌患者预后不良显著相关。在本研究中，我们旨在研究 rab31（过）表达对体外和体内肿瘤进展重要方面的影响。
低表达（MDA-MB-231）或不表达（CAMA-1）内源性 rab31 的乳腺癌细胞被稳定转染 rab31 表达质粒。对批次转染的细胞以及表达不同水平 rab31 蛋白的选定细胞克隆进行分析，以研究增殖、细胞黏附、肿瘤细胞的侵袭能力以及在异种移植肿瘤模型中的体内情况。针对重组表达 rab31 的多克隆抗体进行了生成，并通过免疫组织化学、Western blot 分析和新开发的敏感 ELISA 分析进行蛋白表达分析。
rab31 蛋白水平升高与乳腺癌细胞增殖增强相关。有趣的是，在没有检测到内源性 rab31 表达的细胞系中，弱至中度 rab31 的过表达已足以引起对细胞增殖的明显影响。相比之下，在乳腺癌细胞中表达 rab31 会导致对几种细胞外基质蛋白的黏附减少，并且通过 Matrigel（TM）的侵袭能力降低。再次，rab31 对细胞黏附和侵袭的调节作用呈剂量依赖性。最后，在异种移植小鼠模型中，我们观察到 rab31 过表达的 MDA-MB-231 乳腺癌细胞向肺部转移的能力显著受损。
乳腺癌细胞中 rab31 的过表达导致从侵袭表型到增殖表型的转变，表现为细胞增殖增加、体外黏附性和侵袭性降低，以及体内形成肺转移的能力降低。
