Role of the DNA Damage Response in Prostate Cancer Initiation

本项目研究NKX3.1在前列腺上皮DNA损伤保护中的作用，这可能为其肿瘤抑制功能NKX3提供关键机制。I是一个位于8p21上的前列腺特异性同源盒基因，是人类前列腺癌中最常见的染色体丢失的目标。NKX3。I也是一种肿瘤抑制因子，其蛋白表达的降低足以解除对前列腺上皮细胞生长的调节并引起上皮内瘤变；此外，Nkx3.1单倍不全导致小鼠前列腺上皮异常增生。与其在人类前列腺癌中作为肿瘤抑制因子的作用相一致，我们已经证明NKX3中存在失活突变。在前列腺癌家族中，同位结构域与早发性前列腺癌共分离。在最近的研究中，我们发现NKX3.1增强DNA损伤后的细胞存活，并影响DNA断裂识别的最早事件，包括YH2AX病灶的形成和ATM的磷酸化。

This project investigates the role of NKX3.1 in protection against DNA damage in the prostate epithelium, which may provide a key mechanism for its function in tumor suppression, NKX3.I is a prostate specific homeobox gene located on 8p21, the target for the most frequent chromosomal loss in human prostate cancer. NKX3.I is also a tumor suppressor for which reduced protein expression is sufficient to deregulate prostate epithelial cell growth and cause Intraepithelial neoplasia; moreover, Nkx3.1 haploinsufficiency results in prostate epithelial dysplasia in mice. Consistent with its role as a tumor suppressor in human prostate cancer, we have shown that an Inactivating mutation In the NKX3.I homeodomain cosegregates with early onset prostate cancer in a prostate cancer family. In recent studies, we have shown that NKX3.1 enhances cell survival after DNA damage and affects the earliest events in recognition of DNA breaks, including formation of YH2AX foci and phosphorylation of ATM. Based on our hypothesis that a key mechanism by which NKX3.1 loss contributes to tumor initiation is through its impact on the DNA damage response, our studies will define the mechanistic role of NKX3.I in the DNA damage response in vitro, as well as its impact on DNA damage in vivo. We also will determine whether NKX3.I mediates the susceptibility of prostate cells to formation of the characteristic TMPRSS2- ERG chromosomal rearrangement that occurs in approximately 50% of prostate cancers. Taken together, our three aims will delineate the role of NKXS.I in the DNA damage response in distinct contexts, thereby providing a comprehensive investigation of this key mechanism of tumor suppression. In Aim 1, our experiments will define the dynamics of the functional interaction between NKX3.1 and ATM, which occurs within minutes of DNA damage. In Aim 2, we will determine whether Nkx3.I gene copy number affects the DNA damage response in vivo in the prostate epithelium, and particularly in prostate epithelial stem cells. Finally, in Aim 3, using unique lines of LNCaP cells that we have derived, we will determine whether NKX3.1 affects the frequency of TMPRSS2-ERG gene rearrangements. These proposed studies will be highly integrated with the overall program project. Notably, the experiments in Aim 2 include quantitative immunostaining analyses in collaboration with Core A, the work in Aim 2 on the prostate stem cells will be performed in collaboration with Michael Shen (Project 1), and the entirety of this project is linked to the molecular analyses of Nkx3.1 in cellular senescence by Cory Abate-Shen (Project 2).