Department of Pathology, Kochi Medical School, Nankoku 783-8505, Japan.
Carcinogenesis. 2012 Mar;33(3):548-54. doi: 10.1093/carcin/bgs001. Epub 2012 Jan 5.
Using the PCR-based subtractive messenger RNA hybridization assay described in this paper, we isolated a hitherto uncharacterized gene, transmembrane protein 207 (TMEM207), which was selectively expressed in collagen gel-invading cultured signet-ring cell carcinoma KATO-III cells. TMEM207 has a C-terminal proline-rich PPxY motif, which binds to the WW domain-containing oxidoreductase, WWOX. Enforced expression of TMEM207 significantly increased Matrigel invasion activity of KATO-III cells in vitro without affecting cell growth. In contrast, expression of TMEM207 with mutations in the PPxY motif did not significantly increase Matrigel invasion activity of KATO-III cells. Immunohistochemical staining showed that TMEM207 was strongly expressed in 7 of 30 gastric signet-ring cell carcinoma tissue specimens. Notably, TMEM207 expression was associated with the depth of cancer invasion and the presence of lymph node metastasis. The results of co-immunoprecipitation followed by western immunoblotting showed that TMEM207 is bound to WWOX in a PPxY motif-dependent manner. Small interfering RNA-mediated downregulation of WWOX also significantly increased Matrigel invasion activity of KATO-III cells. Notably, exogenous expression of TMEM207 impaired the WWOX-mediated repression of Matrigel invasion activity of another cultured signet-ring cell carcinoma cell line, NUGC-4 cells. Recent studies have highlighted the fact that WWOX acts as a tumor suppressor factor in various malignant tumors, including gastric cancer. On the basis of these findings and the results of the present study, we think that overexpression of TMEM207 may facilitate invasive activity and metastasis of gastric signet-ring cell carcinoma, which possibly occur through binding to WWOX and attenuation of its function.
利用本文所述的基于 PCR 的消减信使 RNA 杂交分析，我们分离出一个迄今尚未被描述的基因，跨膜蛋白 207（TMEM207），它在胶原蛋白凝胶侵袭性培养的印戒细胞癌 KATO-III 细胞中选择性表达。TMEM207 具有 C 末端富含脯氨酸的 PPxY 基序，该基序与含有 WW 结构域的氧化还原酶 WWOX 结合。TMEM207 的强制表达显著增加了 KATO-III 细胞在体外的 Matrigel 侵袭活性，而不影响细胞生长。相比之下，表达具有 PPxY 基序突变的 TMEM207 不会显著增加 KATO-III 细胞的 Matrigel 侵袭活性。免疫组织化学染色显示，TMEM207 在 30 例胃印戒细胞癌组织标本中的 7 例中强烈表达。值得注意的是，TMEM207 的表达与癌症侵袭的深度和淋巴结转移的存在有关。免疫共沉淀后进行 Western 免疫印迹的结果表明，TMEM207 与 WWOX 以 PPxY 基序依赖的方式结合。小干扰 RNA 介导的 WWOX 下调也显著增加了 KATO-III 细胞的 Matrigel 侵袭活性。值得注意的是，外源性表达 TMEM207 会损害 WWOX 对另一种培养的印戒细胞癌细胞系 NUGC-4 细胞的 Matrigel 侵袭活性的抑制作用。最近的研究强调了 WWOX 在包括胃癌在内的各种恶性肿瘤中作为肿瘤抑制因子的事实。基于这些发现和本研究的结果，我们认为 TMEM207 的过表达可能促进胃印戒细胞癌的侵袭和转移，这可能通过与 WWOX 结合并减弱其功能来实现。
