ARTIK-52 induces replication-dependent DNA damage and p53 activation exclusively in cells of prostate and breast cancer origin

The realization, that the androgen receptor (AR) is essential for prostate cancer (PC) even after relapse following androgen deprivation therapy motivated the search for novel types of AR inhibitors. We proposed that targeting AR expression versus its function would work in cells having either wild type or mutant AR as well as be independent of androgen synthesis pathways. Previously, using a phenotypic screen in androgen-independent PC cells we identified a small molecule inhibitor of AR, ARTIK-52. Treatment with ARTIK-52 caused the loss of AR protein and death of AR-positive, but not AR-negative, PC cells. Here we present data that ARTIK-52 induces degradation of AR mRNA through a mechanism that we were unable to establish. However, we found that ARTIK-52 is toxic to breast cancer (BC) cells expressing AR, although they were not sensitive to AR knockdown, suggesting an AR-independent mechanism of toxicity. Using different approaches we detected that ARTIK-52 induces replication-dependent double strand DNA breaks exclusively in cancer cells of prostate and breast origin, while not causing DNA damage, or any toxicity, in normal cells, as well as in non-PC and non-BC tumor cells, independent of their proliferation status. This amazing specificity, combined with such a basic mechanism of toxicity, makes ARTIK-52 a potentially useful tool to discover novel attractive targets for the treatment of BC and PC. Thus, phenotypic screening allowed us to identify a compound, whose properties cannot be predicted based on existing knowledge and moreover, uncover a barely known link between AR and DNA damage response in PC and BC epithelial cells.

研究人员发现，即便在雄激素剥夺疗法（androgen deprivation therapy）后出现复发，雄激素受体（androgen receptor, AR）仍是前列腺癌（prostate cancer, PC）发生发展的关键驱动因素，这推动了新型AR抑制剂的研发。我们提出，靶向AR表达而非其功能，可在携带野生型或突变型AR的细胞中发挥作用，且不依赖雄激素合成通路。此前，我们通过在非雄激素依赖性前列腺癌细胞中开展的表型筛选，发现了一种小分子AR抑制剂ARTIK-52。ARTIK-52处理可导致AR蛋白降解，并使AR阳性的前列腺癌细胞死亡，但对AR阴性的前列腺癌细胞无此效应。本文中，我们展示的数据表明，ARTIK-52可通过一种尚未明确的机制诱导AR信使RNA（messenger RNA, mRNA）的降解。不过我们发现，ARTIK-52对表达AR的乳腺癌（breast cancer, BC）细胞具有毒性，尽管这些细胞对AR敲低并不敏感，这提示其毒性作用存在不依赖AR的机制。通过多种实验手段，我们检测到ARTIK-52仅在前列腺癌和乳腺癌来源的癌细胞中诱导复制依赖性双链DNA断裂（double strand DNA breaks），而对正常细胞、非前列腺癌及非乳腺癌肿瘤细胞均未造成DNA损伤或任何毒性，且该效应与细胞增殖状态无关。这一出色的特异性，加之其如此基础的毒性作用机制，使得ARTIK-52成为极具潜力的研究工具，可用于发现治疗乳腺癌和前列腺癌的新型潜在靶点。因此，表型筛选帮助我们发现了一种无法通过现有知识预测其特性的化合物，此外还揭示了前列腺癌和乳腺癌上皮细胞（epithelial cells）中AR与DNA损伤应答（DNA damage response）之间鲜为人知的关联。