Department of Pathology, Ohio State University Medical Center, Columbus, Ohio, United States of America.
PLoS One. 2010 Oct 20;5(10):e13406. doi: 10.1371/journal.pone.0013406.
PIWIL2, a member of PIWI/AGO gene family, is expressed in the germline stem cells (GSCs) of testis for gametogenesis but not in adult somatic and stem cells. It has been implicated to play an important role in tumor development. We have previously reported that precancerous stem cells (pCSCs) constitutively express Piwil2 transcripts to promote their proliferation. Here we show that these transcripts de facto represent Piwil2-like (PL2L) proteins. We have identified several PL2L proteins including PL2L80, PL2L60, PL2L50 and PL2L40, using combined methods of Gene-Exon-Mapping Reverse Transcription Polymerase Chain Reaction (GEM RT-PCR), bioinformatics and a group of novel monoclonal antibodies. Among them, PL2L60 rather than Piwil2 and other PL2L proteins is predominantly expressed in various types of human and mouse tumor cells. It promotes tumor cell survival and proliferation in vitro through up-regulation of Stat3 and Bcl2 gene expressions, the cell cycle entry from G(0/1) into S-phase, and the nuclear expression of NF-κB, which contribute to the tumorigenicity of tumor cells in vivo. Consistently, PL2L proteins rather than Piwil2 are predominantly expressed in the cytoplasm or cytoplasm and nucleus of euchromatin-enriched tumor cells in human primary and metastatic cancers, such as breast and cervical cancers. Moreover, nuclear PL2L proteins are always co-expressed with nuclear NF-κB. These results reveal that PL2L60 can coordinate with NF-κB to promote tumorigenesis and might mediate a common pathway for tumor development without tissue restriction. The identification of PL2L proteins provides a novel insight into the mechanisms of cancer development as well as a novel bridge linking cancer diagnostics and anticancer drug development.
PIWIL2 是 PIWI/AGO 基因家族的成员，在睾丸生殖细胞干细胞 (GSCs) 中表达，用于配子发生，但不在成人体细胞和干细胞中表达。它被认为在肿瘤发展中发挥重要作用。我们之前报道过，癌前干细胞 (pCSCs) 持续表达 Piwil2 转录本以促进其增殖。在这里，我们表明这些转录本实际上代表了 Piwil2 样 (PL2L) 蛋白。我们使用基因外显子映射逆转录聚合酶链反应 (GEM RT-PCR)、生物信息学和一组新的单克隆抗体的组合方法，鉴定了几种 PL2L 蛋白，包括 PL2L80、PL2L60、PL2L50 和 PL2L40。其中，PL2L60 而不是 Piwil2 和其他 PL2L 蛋白在各种类型的人类和小鼠肿瘤细胞中均有较高表达。它通过上调 Stat3 和 Bcl2 基因表达、将细胞周期从 G0/G1 期进入 S 期以及核表达 NF-κB 来促进肿瘤细胞的存活和增殖，从而促进肿瘤细胞在体内的致瘤性。一致地，PL2L 蛋白而不是 Piwil2 在富含常染色质的人类原发性和转移性癌症（如乳腺癌和宫颈癌）中的肿瘤细胞的细胞质或细胞质和核中均有较高表达。此外，核 PL2L 蛋白总是与核 NF-κB 共表达。这些结果表明，PL2L60 可以与 NF-κB 协同促进肿瘤发生，并且可能介导一种不受组织限制的常见肿瘤发展途径。PL2L 蛋白的鉴定为癌症发展的机制提供了新的见解，并为癌症诊断和抗癌药物开发提供了新的桥梁。
