The RASSF8 candidate tumor suppressor inhibits cell growth and regulates the Wnt and NF-κB signaling pathways
The RASSF8 candidate tumor suppressor inhibits cell growth and regulates the Wnt and NF-κB signaling pathways
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DOI：
10.1038/onc.2010.192
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发表时间：
2010-07-01
期刊：
影响因子：
8
通讯作者：
Latif, F.
中科院分区：
文献类型：
--
作者：
Lock, F. E.;Underhill-Day, N.;Latif, F.
直到最近，肿瘤抑制蛋白的 Ras 关联结构域家族 (RASSF) 还包含六种名为 RASSF1-6 的蛋白。最近，通过对含有 RA 结构域的蛋白质进行同源搜索，鉴定出了四个新的家族成员 RASSF7-10。这些额外的 RASSF 成员与 RASSF1-6 不同且结构不同，包含 N 端 RA 结构域，但缺少 Sav/RASSF/Hpo (SARAH) 结构域。在这里，我们表明 RASSF8 在整个小鼠胚胎和正常人类成人组织中普遍表达。从功能上讲，RNAi介导的非小细胞肺癌（NSCLC）细胞系中RASSF8的敲低，增加了软琼脂中的贴壁独立生长，并增强了严重联合免疫缺陷（SCID）小鼠中的肿瘤生长。此外，RASSF8 耗尽细胞的 EdU 染色显示生长抑制以依赖于接触抑制的方式进行。我们发现内源性 RASSF8 不仅存在于细胞核中，而且还与细胞间粘附位点的膜相关，与粘附连接 (AJ) 成分 β-连环蛋白共定位并与 E-钙粘蛋白结合。使用替代小干扰 RNA (siRNA) 序列在两种不同的肺癌细胞系中去除 RASSF8 后，我们发现 AJ 不稳定，并且 E-钙粘蛋白从细胞膜上丢失。 AJ 成分 β-连环蛋白和 p65 也从细胞与细胞接触的位点丢失，并重新定位到细胞核，同时 RASSF8 耗尽后，β-连环蛋白依赖性和核因子 kappa B (NF-kappa B) 依赖性信号传导增加。 RASSF8 可能也需要维持肌动蛋白细胞骨架组织，因为免疫荧光分析显示 RASSF8 耗尽后肌动蛋白细胞骨架出现显着的混乱。因此，划痕伤口愈合研究表明 RASSF8 缺陷细胞的细胞迁移增加。这些结果表明 RASSF8 是一种肿瘤抑制基因，对于维持上皮细胞中 AJ 的功能至关重要，并且在上皮细胞迁移中发挥作用。癌基因 (2010) 29, 4307-4316; doi：10.1038/onc.2010.192； 2010 年 5 月 31 日在线发布
The Ras-assocation domain family (RASSF) of tumor suppressor proteins until recently contained six proteins named RASSF1-6. Recently, four novel family members, RASSF7-10, have been identified by homology searches for RA-domain-containing proteins. These additional RASSF members are divergent and structurally distinct from RASSF1-6, containing an N-terminal RA domain and lacking the Sav/RASSF/Hpo (SARAH) domain. Here, we show that RASSF8 is ubiquitously expressed throughout the murine embryo and in normal human adult tissues. Functionally, RNAi-mediated knockdown of RASSF8 in non-small-cell lung cancer (NSCLC) cell lines, increased anchorage-independent growth in soft agar and enhanced tumor growth in severe combined immunodeficiency (SCID) mice. Furthermore, EdU staining of RASSF8-depleted cells showed growth suppression in a manner dependent on contact inhibition. We show that endogenous RASSF8 is not only found in the nucleus, but is also membrane associated at sites of cell-cell adhesion, co-localizing with the adherens junction (AJ) component beta-catenin and binding to E-cadherin. Following RASSF8 depletion in two different lung cancer cell lines using alternative small interfering RNA (siRNA) sequences, we show that AJs are destabilized and E-cadherin is lost from the cell membrane. The AJ components beta-catenin and p65 are also lost from sites of cell-cell contact and are relocalized to the nucleus with a concomitant increase in beta-catenin-dependent and nuclear factor-kappa B (NF-kappa B)-dependent signaling following RASSF8 depletion. RASSF8 may also be required to maintain actin -cytoskeletal organization since immunofluorescence analysis shows a striking disorganization of the actincytoskeleton following RASSF8 depletion. Accordingly, scratch wound healing studies show increased cellular migration in RASSF8-deficient cells. These results implicate RASSF8 as a tumor suppressor gene that is essential for maintaining AJs function in epithelial cells and have a role in epithelial cell migration. Oncogene (2010) 29, 4307-4316; doi: 10.1038/onc.2010.192; published online 31 May 2010