Targeting ATDC with PARP inhibitors in pancreatic cancer

描述（由申请人提供）：我们最近报道了ATDC（也称为TRIM29）在胰腺癌中高表达，并通过WNT/b-catenin途径促进细胞增殖，显示出致癌特性（Cancer cell 15:07, 2009）。我们的初步结果还表明，ATDC可以保护胰腺癌细胞免受放射和化疗的影响。促生长和耐药的特性表明ATDC是一个重要的治疗靶点。为了更好地了解ATDC的功能及其在耐药性中的作用，我们探索了在暴露于电离辐射之前和/或之后ATDC与哪些蛋白质相互作用。通过免疫沉淀试验，我们发现ATDC与聚（adp -核糖）聚合酶1 （PARP1）相互作用，并且这种相互作用在暴露于电离辐射后显著增加。为了研究这种相互作用是否依赖于PARP的催化活性，我们用PARP抑制剂处理细胞，并令人惊讶地发现，这种处理导致ATDC细胞蛋白水平的显著降低。此外，通过siRNA敲低Parp1表达导致ATDC水平降低，表明Parp1刺激胰腺癌细胞中ATDC的表达。重要的是，我们的初步结果表明，PARP抑制导致胰腺癌细胞增殖减少和对电离辐射的敏感性增加。我们假设ATDC是胰腺癌的一个有希望的新治疗靶点，因为它的失活可能导致肿瘤生长减少和对放射治疗的敏感性。此外，我们假设PARP抑制剂将靶向ATDC，选择性地抑制表达ATDC的胰腺癌肿瘤的生长和增敏。

DESCRIPTION (provided by applicant): We recently reported that ATDC (also known as TRIM29) is highly expressed in pancreatic cancers and that it exhibits oncogenic properties by promoting cell proliferation via the WNT/b-catenin pathway (Cancer Cell 15:207, 2009). Our preliminary results also show that ATDC protects pancreatic cancer cells against radiation and chemotherapy. The properties of growth promotion and resistance to therapy suggest that ATDC is an important therapeutic target. To better understand the function of ATDC and its role in resistance, we explored what proteins ATDC interacts with before and/or after exposure to ionizing radiation. Using immunoprecipitation assays we found that ATDC interacts with poly(ADP-ribose)polymerase1 (PARP1) and that this interaction is substantially increased following exposure to ionizing radiation. To investigate whether this interaction is dependent on the catalytic activity of PARP, we treated cells with PARP inhibitors and found surprisingly that this treatment lead to a marked loss of the cellular protein levels of ATDC. Furthermore, knockdown of Parp1 expression by siRNA resulted in reduced levels of ATDC indicating that PARP1 stimulates the expression of ATDC in pancreatic cancer cells. Importantly, our preliminary results suggest that PARP inhibition results in reduced proliferation and increased sensitivity to ionizing radiation of pancreatic cancer cells. We hypothesize that ATDC is a promising novel therapeutic target in pancreatic cancer because its inactivation may lead to both reduced tumor growth and sensitization to radiation therapy. Furthermore, we hypothesize that PARP inhibitors will target ATDC and selectively inhibit growth and sensitize ATDC-expressing pancreatic cancer tumors. PUBLIC HEALTH RELEVANCE: Pancreatic cancer has the worst outcome of any cancer and kills more than 30,000 people in the US annually. We recently found that the protein ATDC is expressed at abnormally high levels in pancreatic cancer and this overexpression promotes the growth and resistance of pancreatic tumors. Unexpectedly, we found that a class of chemotherapeutic drugs currently in clinical use reduces ATDC levels in pancreatic cancer cells and make them more sensitive to radiation. In this R21 proposal we will explore the mechanisms of how these drugs reduce ATDC levels and whether they will target ATDC in pancreatic tumors in laboratory mice.