Research Institute, National Cancer Center, Goyang, 10408, Republic of Korea.
Department of Environmental Medical Biology, Institute of Tropical Medicine, Yonsei University College of Medicine, Seoul, 03722, Republic of Korea.
Cell Death Dis. 2018 May 24;9(6):633. doi: 10.1038/s41419-018-0650-6.
We have previously reported that FAM188B showed significant differential exon usage in cancers (NCBI GEO GSE30727), but the expression and function of FAM188B is not well characterized. In the present study, we explored the functions of FAM188B by a knockdown strategy, using siRNAs specific for FAM188B in colon cancer cell lines. FAM188B is a novel gene that encodes a protein that is evolutionarily conserved among mammals. Its mRNA has been found to be highly expressed in most solid tumors, including colorectal cancer. FAM188B knockdown induced cell growth inhibition due to an increase in apoptosis in colon cancer cell lines. Interestingly, siFAM188B treatment induced the upregulation and activation of p53, and consequently increased p53-regulated pro-apoptotic proteins, PUMA and BAX. Proteomic analysis of FAM188B immunocomplexes revealed p53 and USP7 as putative FAM188B-interacting proteins. Deletion of the putative USP7-binding motif in FAM188B reduced complex formation of FAM188B with USP7. It is noteworthy that FAM188B knockdown resulted in a decrease in overall ubiquitination in the p53 immunocomplexes, as well as p53 ubiquitination, because USP7 is involved in p53 deubiquitination. FAM188B knockdown inhibited both colony formation and anchorage-independent growth in vitro. In addition, FAM188B knockdown by siRNA reduced tumor growth in xenografted mice, with an increase in p53 proteins. Taken together, our data suggest that FAM188B is a putative oncogene that functions via interaction with USP7. Therefore, control of FAM188B could be a possible target to inhibit tumor growth.
我们之前曾报道 FAM188B 在癌症中表现出显著的差异外显子使用（NCBI GEO GSE30727），但 FAM188B 的表达和功能尚未得到很好的描述。在本研究中，我们使用针对结肠癌细胞系的 FAM188B 的 siRNA 敲低策略来探索 FAM188B 的功能。FAM188B 是一种编码蛋白质的新基因，在哺乳动物中具有进化保守性。已经发现其 mRNA 在大多数实体瘤中高度表达，包括结直肠癌。FAM188B 敲低导致细胞生长抑制，这是由于细胞凋亡增加所致。有趣的是，siFAM188B 处理诱导 p53 的上调和激活，并且随后增加 p53 调节的促凋亡蛋白 PUMA 和 BAX。FAM188B 免疫复合物的蛋白质组分析显示 p53 和 USP7 是假定的 FAM188B 相互作用蛋白。FAM188B 中的假定 USP7 结合基序的缺失减少了 FAM188B 与 USP7 的复合物形成。值得注意的是，FAM188B 敲低导致 p53 免疫复合物中的总体泛素化以及 p53 泛素化减少，因为 USP7 参与 p53 去泛素化。FAM188B 敲低抑制了体外集落形成和非锚定依赖性生长。此外，siRNA 敲低 FAM188B 减少了异种移植小鼠中的肿瘤生长，并且 p53 蛋白增加。总之，我们的数据表明 FAM188B 是一种假定的癌基因，通过与 USP7 相互作用发挥作用。因此，控制 FAM188B 可能是抑制肿瘤生长的一个可能目标。
