Oncogenic role of the ICK-GSK3beta signaling pathway

 描述(申请人提供)：结直肠癌(CRC)是世界上第三大常见恶性肿瘤和第四大常见死亡原因，迫切需要新的治疗方法来治疗这种毁灭性的疾病。虽然许多在结直肠癌中起重要作用的信号通路已经被发现，但我们对这些通路在肠上皮恶性转化过程中如何功能上的网络和相互作用的理解上仍有很大的差距。我们的长期目标是确定这个复杂的信号拼图中缺少的关键成分，以促进我们对结肠癌分子机制的理解。本研究的目的是探讨一个新的信号通路ICK-GSK3β在结肠癌发生和肿瘤对拉帕洛格耐药中的作用。我们的中心假设是，非调控的ICK-GSK3β信号轴通过抑制β-T7的磷酸化将异常的WNT信号转导到mTOR过度激活，并通过介导一种新的反馈机制在结肠癌治疗中产生雷帕霉素耐药，从而在肠道肿瘤发生中发挥关键作用。这一假说基于我们最近发表的和初步的数据：1)Wnt转录靶标ICK在人结肠癌标本和小鼠肠腺瘤中高度过表达；2)ICK在人结肠癌细胞中的表达下调，有效地抑制了体外的恶性增殖和体内的皮下肿瘤生长；3)阻断了结肠癌细胞中的ICK信号，损害了mTOR和WNT的激活；4)作为WNT和mTOR通路的关键成分，GSK3β是ICK的新底物；5)与邻近的正常粘膜和雷帕霉素治疗后的人结肠癌细胞相比，ICK使β-T7的磷酸化水平升高。为了验证这一假设，我们提出了以下两个具体目标：Aim-1将确定ICK是否能够通过靶向Gsk3β上的一个新的抑制性磷酸化位点来激活结肠癌细胞中的mTOR信号；Aim-2将确定ICK-GSK3β信号轴是否在Wnt信号异常诱导的肠道恶性肿瘤和雷帕霉素耐药中起重要作用。我们提出的工作具有重要意义，因为我们的目标将解决我们在理解Wnt激活mTOR、抑制磷酸化和调节Gsk3β以及雷帕霉素耐药性的机制方面的主要知识空白。我们的工作具有创新性，因为我们的目标可能是确定苏氨酸蛋白7的抑制磷酸化是Gsk3β的一种新的调节机制，而雷帕霉素诱导的Gsk3β-T7磷酸化的反馈上调是导致雷帕霉素耐药的一种创新机制。预期的结果可能会对了解结肠癌发生和发展的潜在信号机制以及设计更有效的联合分子疗法以克服耐药性和防止肿瘤复发产生重大影响。

 DESCRIPTION (provided by applicant): Colorectal cancer (CRC) is the third most common malignancy and fourth most common cause of mortality worldwide, and there is an urgent need of new therapeutic approaches for this devastating disease. Although many signaling pathways with important roles in CRC have been identified, there are still major gaps in our understanding about how these pathways functionally network and interplay during malignant transformation of the intestinal epithelium. Our long-term goal is to identify key missing components in this complex signaling puzzle to advance our understanding of the molecular mechanism underlying colon cancer. The objective of this proposal is to explore the role of a novel signaling pathway ICK-GSK3β in the development of colon cancer and tumor resistance to rapalogs. Our central hypothesis is that deregulated ICK-GSK3β signaling axis plays a pivotal role in intestinal neoplasia by transducing aberrant Wnt signals to mTOR hyper-activation through inhibitory phosphorylation of GSK3β-T7 and by mediating a novel feedback mechanism underlying rapamycin resistance in colon cancer therapy. This hypothesis was formulated on the basis of our recent published and preliminary data: 1) ICK, a Wnt transcriptional target, is highly over-expressed in human colon cancer specimens and mouse intestinal adenomas; 2) Knockdown of ICK expression in human colon cancer cells effectively attenuated malignant proliferation in vitro and subcutaneous tumor growth in vivo; 3) Disrupting ICK signaling in colon cancer cells impaired mTOR and Wnt activation; 4) GSK3β, a key component of both Wnt and mTOR pathways, is a novel substrate for ICK; 5) Elevated phosphorylation of GSK3β-T7 by ICK was observed in human CRC specimens as compared with adjacent normal mucosa and in human colon cancer cells after rapamycin treatment. To test this hypothesis, we propose the following two specific aims: Aim-1 will determine whether ICK is able to activate mTOR signaling in colon cancer cells through targeting a novel inhibitory phosphorylation site on GSK3β; Aim-2 will determine whether the ICK-GSK3β signaling axis is important for aberrant Wnt signal-induced intestinal malignancy and rapamycin resistance. Our proposed work is significant because our aims will address major knowledge gaps in our understanding of the mechanisms underlying Wnt activation of mTOR, inhibitory phosphorylation and regulation of GSK3β, and rapamycin resistance. Our proposed work is innovative because our aims may identify inhibitory phosphorylation of Thr-7 as a novel regulatory mechanism for GSK3β, and rapamycin-induced feedback up-regulation of GSK3β-T7 phosphorylation as an innovative mechanism underlying rapamycin resistance. Anticipated outcomes may exert significant impacts on the understanding of the signaling mechanisms underlying the onset and development of colon cancer as well as the design for more effective combination molecular therapy to overcome drug resistance and prevent tumor relapse.