Functional and Therapeutic Significance of PLK4 in Melanoma

总结： 本研究的目的是确定polo样激酶4（PLK 4）是否与其他黑色素瘤驱动因子沿着 是黑色素瘤管理的治疗上可操作的药物靶点， PLK 4的机制和相互作用的合作伙伴，在黑素细胞转化和肿瘤进展。 黑色素瘤是一种临床上具有挑战性的皮肤癌，如果没有早期诊断。流行病学和基因组数据 提示BRAFV 600 E突变可能是黑素细胞痣的起始病变;然而，这些突变 仅是恶性转化是不够的。紫外线辐射（UVR）和其他激活 已知致癌途径有助于黑素细胞的肿瘤进展。在最近的过去， 晚期黑色素瘤管理的治疗前景随着批准 BRAF抑制剂和免疫检查点抑制剂等新药。然而，这些治疗 与近50%的患者发生的获得性耐药有关。因此，基于新机制的 需要治疗方法来有效管理这种可怕的肿瘤。基于有限 根据最近的一些研究，PLK 4被认为是某些癌症的潜在药物靶点。Plk4 抑制已显示导致中心粒和中心体复制失败，而其 过表达导致过量的中心粒形成，其足以驱动中心体扩增 (CA)和基因组的不稳定性与致癌作用有关。最近的一项研究表明PLK 4在以下方面的作用： 通过调节PI 3 K/AKT信号通路诱导上皮-间充质转化（EMT）。我们最近证明， PLK 4在黑色素瘤中显著过表达，小分子PLK 4抑制导致显著的细胞凋亡。 在多种黑色素瘤细胞系中的抗增殖反应[Mol Cancer Res，2018]。我们的初步数据显示 PLK 4 CRISPR K/O A375黑色素瘤细胞在黑色素瘤中显示出显著降低的肿瘤生长， 表明PLK 4在黑素瘤中的重要作用。我们还发现PLK 4的联合抑制 BRAF和MEK抑制剂在黑色素瘤细胞中具有协同抗增殖作用。本研究 我建议挑战一个假设，即PLK 4信号传导，以及黑素细胞的其他驱动途径， 转化和肿瘤进展，将提供治疗上可行的新的共靶向 黑色素瘤的治疗方法。提出了三个目标：1）确定之间的关联 PLK 4和离体黑素细胞转化和肿瘤进展的其他驱动途径; 2） 确定PLK 4在黑色素瘤进展和转移中的功能和机制意义， 在多种人类相关的基因工程小鼠模型中体内; 3）确定治疗性的 PLK 4抑制的意义，单独和与其他有前途的基于靶点的抗黑色素瘤组合 体内的模式。我们希望我们的研究将确定PLK 4在黑色素瘤中的确切作用， 诊断/预后以及治疗意义。

SUMMARY: The objective of this study is to determine if the polo-like kinase 4 (PLK4) along with other melanoma driver pathways, is a therapeutically actionable druggable target for melanoma management, and what are the mechanisms and interacting partners of PLK4, during melanocytic transformation and neoplastic progression. Melanoma is a clinically challenging skin cancer, if not diagnosed early. Epidemiological and genomic data suggest that BRAFV600E mutations may be the initiating lesion in melanocytic nevi; however, these mutations alone are not sufficient for malignant transformation. Ultraviolet radiation (UVR) and activation of other oncogenic pathways are known to contribute to the neoplastic progression of melanocytes. In the recent past, the treatment landscape for advanced melanoma management has seen dramatic changes with the approval of new drugs such as BRAF inhibitors as well as immune-checkpoint inhibitors. However, these treatments are linked with acquired resistance occurring in nearly 50% of patients. Therefore, novel mechanism-based therapeutic approaches are needed for effective management of this dreaded neoplasm. Based on limited number of recent studies, PLK4 is being considered as a potential druggable target for certain cancers. PLK4 inhibition has been shown to cause a failure of centriole and centrosome duplication, whereas its overexpression results in excess centriole formation, which are sufficient to drive centrosome amplification (CA) and genome instability that is linked to carcinogenesis. A recent study has suggested a role of PLK4 in epithelial-mesenchymal transition (EMT) via modulating PI3K/AKT pathway. We recently demonstrated that PLK4 is significantly overexpressed in melanoma, and small molecule PLK4 inhibition resulted in a significant anti-proliferative response in multiple melanoma cell lines [Mol Cancer Res, 2018]. Our preliminary data has shown that PLK4 CRISPR K/O A375 melanoma cells show significantly decreased tumor growth in melanoma xenografts suggesting an important role of PLK4 in melanoma. We also found that combined inhibition of PLK4 with BRAF and MEK inhibition exerted synergistic antiproliferative effect in melanoma cells. In this study, we propose to challenge a hypothesis that PLK4 signaling, together with other driver pathways of melanocytic transformation and neoplastic progression, will provide therapeutically-actionable novel co-targeting approaches, for melanoma management. Three aims are proposed to; 1) determine the association between PLK4 and other driver pathways of melanocytic transformation and neoplastic progression ex vivo; 2) determine the functional and mechanistic significance of PLK4 in melanoma progression and metastasis in vivo in a variety of human-relevant genetically engineered mouse models; 3) determine the therapeutic significance of PLK4 inhibition, alone and in combination with other promising target-based anti-melanoma modalities in vivo. We expect that our study will establish the exact role of PLK4 in melanoma, and its diagnostic/prognostic as well as therapeutic significance in this neoplasm.