ZFHX3 acts as a tumor suppressor in prostate cancer by targeting FTO-mediated m6A demethylation. ZFHX3 acts as a tumor suppressor in prostate cancer by targeting FTO-mediated m6A demethylation

Zinc-finger homeobox 3 (ZFHX3, also known as ATBF1) suppresses prostatic tumorigenesis. ZFHX3 is frequently found to have numerous deletions in human prostate cancer (PCa). However, the underlying molecular function of ZFHX3 during prostatic tumorigenesis is not well understood. N6-methyladenosine (m6A) modification in RNA plays a critical role in the development of cancers; however, the relationship between ZFHX3 and m6A modification is largely unknown in PCa. In this study, we found that ZFHX3 knockdown decreased total m6A levels through enhancing the transcriptional activity of FTO in PCa cells. Importantly, FTO inhibition suppressed cell proliferation and rescued the promoting function of ZFHX3 knockdown on cell proliferation. In vivo, we verified that FTO was upregulated and ZFHX3 was decreased in PCa patients and that a high level of ZFHX3 is indispensable for low FTO expression and is correlated with better patient survival. Through transcriptome sequencing and Me-RIP sequencing, we revealed that E2F2 and CDKN2C were the direct targets of FTO-mediated m6A modification and ZFXH3 was required for the regulation of FTO on E2F2 and CDKN2C expression. Unexpectedly, we uncovered that ZFHX3 expression was in return regulated by FTO in a m6A-dependent way. These findings establish a novel crosstalk mechanism between ZFHX3 and FTO in prostatic tumorigenesis. Overall design: Examination of m6A modification levels in control cells and FTO-knockdown cells

锌指同源框3（Zinc-finger homeobox 3，简称ZFHX3，又称ATBF1）可抑制前列腺肿瘤发生。研究表明，ZFHX3在人类前列腺癌（prostatic cancer，以下简称PCa）中常存在大量片段缺失。然而，ZFHX3在前列腺肿瘤发生过程中的潜在分子功能尚未被充分阐明。RNA上的N6-甲基腺嘌呤（N6-methyladenosine，简称m6A）修饰在癌症发生发展中发挥关键作用，但ZFHX3与m6A修饰在PCa中的关联仍知之甚少。本研究发现，在PCa细胞中，ZFHX3敲低可通过增强FTO的转录活性降低细胞内总m6A水平。值得注意的是，抑制FTO可抑制细胞增殖，并逆转ZFHX3敲低对细胞增殖的促进作用。在体内实验中，我们证实PCa患者组织中FTO表达上调而ZFHX3表达下调；高表达的ZFHX3对于低水平FTO表达是必需的，且与患者更好的生存预后相关。通过转录组测序与甲基化RNA免疫沉淀测序（Me-RIP sequencing），我们揭示E2F2与CDKN2C是FTO介导的m6A修饰的直接靶标，且ZFHX3是FTO调控E2F2与CDKN2C表达所必需的。出乎意料的是，我们还发现FTO可通过m6A依赖的方式反向调控ZFHX3的表达。上述发现揭示了ZFHX3与FTO在前列腺肿瘤发生中的新型串扰调控机制。总体设计：检测对照组细胞与FTO敲低细胞中的m6A修饰水平。