SPHK1诱导非小细胞肺癌肿瘤干细胞特性的分子机制

Mounting evidence has shown that tumor stem cells, characterised with self-renewal and irregularated signalling pathways, play important roles in chemotherapy failure and tumor recurrence. It also has been suggested that Wnt/β-catenin signalling pathway is crucial for tumor stem cell regulation and tumorigenesis. The precise mechanism by which tumor stem cells keep constitutive Wnt/β-catenin activity, however, remains largely unclear. Previously, we have reported that SPHK1 could reinforce resistance of Non-Small Cell Lung Cancer (NSCLC) cells to chemotherapy (Clin Cancer Res, 2011). Recently, our preliminary results demonstrated that SPHK1 induced stemness of NSCLC tumor stem cells and promoted self-renewal in vitro and in vivo. Notably, SPHK1 binds to β-catenin and facilitates the translocation of β-catenin to the nucleus. Moreover, we found that miR-31 expression level was significantly upregulated in SPHK1 overexpressing cells via microRNA array. Upregulation of miR-31 dramatically inhibits the expression levels of APC, Axin1 and WTX, which function as negative regulatory proteins of β-catenin signalling pathway, ultimately resulting in activation of Wnt/β-catenin pathway. Therefore, in the current project, we are aiming to systematically investigate the mechanism underlying SPHK1-induced self-renewal activity of NSCLC tumor stem cells through constitutive activation of Wnt/β-catenin signalling pathway, which would provide novel therapeutic targets for NSCLC treatment.

肿瘤干细胞借助信号通路的异常调控实现自我更新，被认为是化疗失败导致肿瘤复发的罪魁祸首。研究表明 β-catenin通路在肿瘤干细胞中起关键作用，并伴随持续性激活，但其分子机制不明。前期我们证明鞘氨醇激酶1(SPHK1)增强非小细胞肺癌(NSCLC)细胞对化疗药物的抵抗性(Clin Cancer Res,2011)。体内外的预实验显示，SPHK1诱导产生NSCLC肿瘤干细胞并维持其自我更新。尤为重要的是，SPHK1结合并促进β-catenin发生大量核转位；通过芯片筛出miR-31受到SPHK1最为显著的上调， 而miR-31抑制负性调控蛋白APC、Axin1和WTX的表达明显激活β-catenin通路。以此为基础，本项目将系统性证实SPHK1介导β-catenin通路在诱导NSCLC肿瘤干细胞特性中起重要作用，阐明SPHK1持续激活β-catenin通路的机理，为治疗NSCLC提供新靶点。

肿瘤干细胞借助信号通路的异常调控实现自我更新，被认为是化疗失败导致肿瘤复发的罪魁祸首。研究表明Wnt/β-catenin通路在肿瘤干细胞中起关键作用，并伴随持续性激活，但其分子机制不明。本项目研究发现：（1）在乳腺癌中，miR-374a通过抑制WIF1，WNT5A，PTEN的表达维持Wnt/β-catenin信号通路的持续激活，继而促进肿瘤细胞发生EMT并促进肿瘤发生转移（J Clin Invest. 2013;123(2):566–579.）；（2）在乳腺癌中，Sam68高表达促进Wnt/β-catenin信号通路的激活，进而促进乳腺癌细胞的干细胞表型及自我更新能力（Medicine (Baltimore). 2015 Dec;94(49):e2228.）；（3）在乳头状甲状腺癌中SPHK1通过抑制miR-144的表达，维持FN1蛋白水平，进而促进了肿瘤侵袭的恶性表型（J Cancer Res Clin Oncol. 2016 Dec 10.）；（4）在胃癌中，SPHK1通过激活Akt/FoxO3a信号通路抑制Bim的表达，从而增强了胃癌细胞的抗凋亡能力（Oncol Rep. 2014 Oct;32(4):1369-73.）；（5）PSAT1，SOSTDC1，URGCP等基因促进非小细胞肺癌增殖、侵袭等恶性表型；（Int J Cancer. 2015 Feb 15;136(4):E39-50; Cell Biosci. 2016 Apr 14;6:24; Oncotarget. 2015 Nov 3;6(34):36489-504.）。以上研究结果表明，（1）Wnt/β-catenin通路在肿瘤细胞中的持续激活维持了肿瘤细胞的干细胞特性，并促进肿瘤转移和复发；（2）SPHK1在多种肿瘤中高表达，促进了肿瘤细胞的多种恶性表型，并可作为肿瘤预后判断的潜在标志物和治疗靶点。