Targeting cholesterol metabolism and replication stress response in cancer therapy

项目总结： 肺癌是导致男性和女性癌症死亡的主要原因。非小细胞肺癌(NSCLC) 占肺癌诊断的绝大部分，迫切需要新的治疗策略 需要的。ATR及其下游效应子CHK1是复制应激(RS)反应的关键成分 特别是在DNA复制过程中处理停滞的复制叉子，对于细胞在 RS。针对ATR和CHK1的抑制剂目前正在进行临床试验。然而，仅有有限的疗效 当这些药物与标准治疗相结合时，已经观察到了这些药物。确定新的协同效应 使细胞对ATR/CHK1抑制剂敏感的条件将是提高这些药物疗效的关键。 角鲨烯环氧酶(SQLE)，一种控制胆固醇生物合成的酶，通过将角鲨烯转化为 内质网(ER)中的氧化月桂烯常在包括肺癌在内的人类肿瘤中过表达 癌症。Sqle高表达与预后不良有关。我们最近的全基因组功能丧失 Screen发现，Sqle的减少导致了对CHK1抑制剂的敏感性增强。因此，这一目标是 其应用是确定SQLE抑制是否使NSCLC细胞对ATR和CHK1抑制剂以及 联合抑制Sqle能否特异性靶向高表达Sqle的非小细胞肺癌 和ATR/CHK1。我们的初步数据表明，shRNA敲除的SQLE抑制导致RS和 激活ATR/CHK1激活。此外，抑制Sqle还导致Wip1，a蛋白表达增加 抑制ATM活性的磷酸酶，ATM是控制DNA修复的主要DNA损伤反应蛋白。 我们假设，抑制SQLE通过抑制DNA修复，使细胞变得敏感，从而导致RS增加 对ATR和CHK1的抑制。因此，SQLE抑制剂和ATR或CHK1抑制剂联合给药可以 协同抑制肿瘤生长。为了验证我们的假设，我们提出了三个具体目标。具体目标1 将询问Sqle抑制导致Wip1表达增加的机制。特定目标2将 确定SQLE抑制是否通过损害DNA修复，特别是同源DNA修复而导致RS增加 重组，一条预防和拮抗RS的主要修复途径。具体目标3将评估疗效 联合应用SQLE和ATR/CHK1抑制肿瘤细胞生长的体外实验 以及基于细胞系和患者来源的非小细胞肺癌异种移植(PDX)模型。如果成功，我们的研究将 揭示了抑制SQLE和ATR/CHK1之间的一种新的合成致死相互作用，并将具有显著的 通过确定新的治疗方法对提高肺癌患者存活率的影响。

Project Summary: Lung cancer is the leading cause of cancer deaths in both men and women. Non-small cell lung cancer (NSCLC) accounts for large majority of lung cancer diagnoses, and novel treatment strategies for this disease are urgently needed. ATR and its downstream effector CHK1 are key component of replication stress (RS) response that specifically deal with the stalled replication forks during DNA replication and are critical for cell survival under RS. Inhibitors targeting ATR and CHK1 are currently being tested in clinical trials. However, only limited efficacy has been observed when those agents are combined with standard therapy. Identifying the new synergistic conditions that render cells sensitive to ATR/CHK1 inhibitors will be key to improving the efficacy of these agents. Squalene epoxidase (SQLE), an enzyme controlling cholesterol biosynthesis by converting squalene to oxidosqualene in endoplasmic reticulum (ER), is frequently overexpressed in human cancers, including lung cancer. High expression of SQLE is associated with poor prognosis. Our recent genome-wide loss of function screen discovered that SQLE reduction led to enhanced sensitivity to a CHK1 inhibitor. Thus, the goal of this application is to determine whether SQLE inhibition sensitizes NSCLC cells to ATR and CHK1 inhibitors and whether high SQLE-expressing NSCLC cancer can be specifically targeted by the combined inhibition of SQLE and ATR/CHK1. Our preliminary data suggest that SQLE inhibition by shRNA knockdown causes RS and activates ATR/CHK1 activation. In addition, SQLE inhibition lead to increased protein expression of WIP1, a phosphatase that suppress the activity of ATM, a master DNA damage response protein controlling DNA repair. We hypothesize that SQLE inhibition leads to increased RS by suppressing DNA repair, rendering cells sensitive to ATR and CHK1 inhibition. Thus, co-administration of an SQLE inhibitor and an ATR or CHK1 inhibitor could synergistically suppress tumor growth. To test our hypothesis, three Specific Aims are proposed. Specific Aim 1 will interrogate the mechanism by which SQLE inhibition leads to increased WIP1 expression. Specific Aim 2 will determine whether SQLE inhibition leads to increased RS by impairing DNA repair, particularly homologous recombination, a major repair pathway that prevents and antagonizes RS. Specific Aim 3 will assess the efficacy of combined SQLE inhibition and ATR/CHK1 inhibition in suppressing tumor cell growth using in vitro assays as well as cell line-based and patient-derived xenograft (PDX) models of NSCLC. If successful, our studies will reveal a new synthetic lethal interaction between inhibition of SQLE and ATR/CHK1 and will have a significant impact on improving the survival of lung cancer patients by identifying novel therapeutic approaches.