Role of ALDH in PARP inhibitor resistance in HR-deficient ovarian cancer

摘要 聚(ADP-核糖)聚合酶(PARP)抑制剂(PARPI)是一类令人兴奋和有前途的新的 已获FDA批准用于BRCA1或BRCA2复发卵巢癌的抗癌药物 突变，以及作为铂敏感型卵巢癌一线治疗后的维持治疗 BRCA突变。PARPI通过合成杀伤力选择性地杀死BRCA1/2缺陷的癌细胞。然而， 接受PARPI治疗的患者最终会发生癌症进展，并获得PARP抑制剂耐药性 仍然是临床上的一个障碍。获得性PARPI耐药的机制之一是恢复 DNA修复能力，主要通过BRCA1/2的二级突变。我们的初步研究 证实PARPI可以增强卵巢癌细胞的乙醛脱氢酶(ALDH)活性， 主要是通过诱导ALDH家族的一个亚型ALDH1A1的表达。此外，我们还发现， ALDH1A1能够增强微同源介导的末端连接(MMEJ)，这是修复途径之一 DNA双链断裂(DSB)，增强DNA聚合酶θ(POLθ)的表达 MMEJ途径，降低BRCA2突变卵巢癌细胞对PARPI的敏感性。基于 在这一科学前提下，我们提出了一个假设，即PARPI诱导的ALDH1A1的过度表达 MMEJ通过上调Polθ的表达促进HR缺陷症PARPI治疗后细胞存活 癌细胞，最终导致获得性PARPI耐药。因此，对ALDH1A1的抑制应该是 能与PARPI协同治疗HR缺陷型EOC，逆转HR缺陷型EOC对PARPI的耐药性 平等机会委员会。这项建议的主要目标是确定一种有助于PARPI的新机制 BRCA1/2突变的EOC细胞中的耐药性，并检测靶向该机制在预防和治疗卵巢癌中的作用 逆转这些细胞中的PARPI耐药。提出了两个具体的目标来检验这一假设并实现 我们的目标。在具体目标1中，我们将确定PARPI诱导MMEJ增强的机制 在HR缺乏的EOC细胞中的表达及其在PARPI抵抗中的作用。在具体目标2中，我们将确定 ALDH1A1抑制剂NCT-505预防和逆转PARPI耐药的作用 BRCA1/2突变的体内外EoC。我们期望在这个项目结束时，我们将 证实了在HR缺乏的EoC中PARPI抵抗发生的新机制。 我们还将展示ALDH1A1抑制剂在治疗这些患者方面的治疗潜力。

Summary Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) are an exciting and promising new class of anticancer drugs, which have been approved by the FDA for recurrent ovarian cancer with BRCA1 or BRCA2 mutations, and as maintenance therapy after frontline therapy for platinum sensitive ovarian cancer regardless of BRCA mutation. PARPi selectively kill BRCA1/2-deficient cancer cells through synthetic lethality. However, patients receiving PARPi eventually develop cancer progression, and acquired PARP inhibitor resistance remains a clinical hurdle. One of the mechanisms underlying acquired PARPi resistance is the restoration of DNA repair capacity, mainly through the secondary mutations of BRCA1/2. Our preliminary study has demonstrated that PARPi can enhance the Aldehyde dehydrogenase (ALDH) activity in ovarian cancer cells, mainly through inducing expression of ALDH1A1, an isoform of the ALDH family. In addition, we also found that ALDH1A1 is able to augment the microhomology-mediated end joining (MMEJ), one of the pathways for repairing DNA double-strand breaks (DSBs), enhance the expression of DNA polymerase θ (Pol θ), a key player in the MMEJ pathway, as well as reduce the sensitivity of BRCA2 mutated ovarian cancer cells to PARPi. Based on this scientific premise, we generate a hypothesis that PARPi-induced overexpression of ALDH1A1 enhances MMEJ via increasing the expression of Pol θ, and promotes cell survival after PARPi treatment in HR-deficient cancer cells, eventually leading to acquired PARPi resistance. Consequently, inhibition of ALDH1A1 should be able to synergize with PARPi in treating HR-deficient EOC, and reverse resistance to PARPi in HR-deficient EOC. The main objective of this proposal is to determine a novel mechanism that contributes to PARPi resistance in BRCA1/2-mutated EOC cells, and test the efficacy of targeting this mechanism in preventing and reversing PARPi resistance in these cells. Two specific aims are proposed to test this hypothesis and achieve our goal. In specific aim 1, we will determine the mechanism underlying PARPi-induced augmentation of MMEJ in HR-deficient EOC cells and its contribution to PARPi resistance. In specific aim 2, we will determine the therapeutic potential of an ALDH1A1 inhibitor, NCT-505, in preventing and reversing PARPi resistance in BRCA1/2-mutated EOC in vitro and in vivo. It is our expectation that at the conclusion of this project, we will have demonstrated a new mechanism contributing to the development of PARPi resistance in HR-deficient EOC. We will have also shown the therapeutic potential of an ALDH1A1 inhibitor in treating these patients.