新分子Ankrd22促进结直肠癌细胞重新获得干细胞特性靶蛋白鉴定及其作用机制研究

Colorectal cancer stem cells (CCSC) contribute greatly to the invasion, metastasis and recurrence in colorectal cancer (CRC). Recent studies have found that differentiated tumor cells could dedifferentiate and regain stemness characteristic, and then transform into CCSC through constant reprogramming. Thus, blocking of CCSC regeneration becomes a premise for target-eradicating CCSC. However, the mechanisms how differentiated tumor cells regain stemness characteristic are yet to be further understood. We previously found that the expression of Ankrd22 increased significantly in CCSC. CRC cells with enforced expression of Ankrd22 were inclined to stay in the stem-cell stage. Inflammatory cytokines and hypoxia also promoted transcription of Ankrd22. These results indicated that Ankrd22 may be a new therapeutic target for blocking of CCSC regeneration. But the molecular mechanisms of Ankrd22 remain unclear. Based on previous results, our current study is aimed to screen and identify the critical candidate molecules of Ankrd22 by affinity chromatography tandem mass spectrometry/yeast two-hybrid systems, clarify the molecular mechanisms of Ankrd22 promoting CRC reprogramming, and investigate how inflammatory cytokines and hypoxia affect transcription of Ankrd22 and CRC reprogramming. This study will lay a solid foundation for developing new molecular targeted drugs with low toxicity for blocking regeneration of cancer stem cells.

肿瘤干细胞是结直肠癌浸润转移和复发主要原因之一。最近发现普通肿瘤细胞可通过重编程不断去分化和重新获得干细胞特性而再生成肿瘤干细胞。因此，阻断肿瘤干细胞再生成是靶向清除结直肠癌干细胞的前提，然目前对结直肠癌细胞重新获得干细胞特性分子机制尚需明了。我们先前发现Ankrd22在结直肠癌干细胞表达显著增加；表达Ankrd22后细胞多停留在干细胞阶段；炎性因子和缺氧可促进Ankrd22转录。提示Ankrd22可能是靶向阻断结直肠癌干细胞再生成一个新的潜在治疗靶点。然目前Ankrd22分子作用机制尚不明了。本研究拟在先前研究基础上通过亲和串联质谱/酵母双杂交筛选和鉴定Ankrd22相互作用靶蛋白并阐明其促进结直肠癌细胞重新获得干细胞特性分子机制；明确炎性因子和缺氧等对Ankrd22的转录调控及对结直肠癌细胞重新获得干细胞能力影响。本研究为今后研制阻断肿瘤干细胞再生成新的低毒性分子靶向药物打下扎实基础。

普通肿瘤细胞重新获得干细胞特性是结直肠癌患者预后不佳的主要原因之一，肿瘤局部微环境在促进普通肿瘤细胞发生重编程事件起重要作用，然而肿瘤微环境重塑肿瘤细胞代谢过程中的关键分子和代谢重编程又是如何联系着线粒体数量形态改变的分子机制尚需明了。这里我们发现了一个新的核编码的线粒体膜定位蛋白ANKRD22，在结直肠癌干细胞中ANKRD22也可入核；ANKRD22受各种肿瘤微环境因素诱导并在结直肠(癌)干细胞中高表达；我们进一步发现ANKRD22通过与有氧糖酵解和ATP合成通路中多个靶点相互作用促进结直肠癌细胞的有氧糖酵解和减少ATP产生；并且在结直肠癌干细胞中ANKRD22通过与E-Syt1合作将过量脂质转运到线粒体，并以独立于自噬的方式减少了线粒体数量；最后我们发现p53是核内ANKRD22作用的靶点。我们的研究提示ANKRD22在正常胃肠上皮中起抑瘤基因的功能，通过稳定p53水平拮抗核重编程发生，而在具有突变性p53结直肠癌细胞则丧失了此作用；E-Syt1作为ANKRD22将脂质转运到线粒体的关键分子，可能是一个结直肠癌干预的潜在作用靶点。