Abstract 5814: Emergent functions of cyclin-dependent kinase 4 regulating aurora b and cenpp transcription

Abstract A better understanding of the precise molecular mechanisms that control cell proliferation is crucial for the identification of novel cancer therapeutic targets. A critical molecule in this process is the Cyclin-Dependent Kinase 4 (CDK4), which regulates key aspects of the G1 to S phase transition through phosphorylation of the retinoblastoma (Rb) family of proteins. Since dysregulation of this cell cycle mechanism is a hallmark of most cancers, drugs have been developed to inhibit the kinase activity of CDK4. However, such drugs have been met with variable degrees of success and, in some cases, little efficacy. Research performed in the last few years has suggested that CDK4 have alternative targets other than the Rb proteins. Consistent with this idea, we found that CDK4 plays additional roles not related to the canonical function in the CDK-Rb axis. Here, we show that CDK4 remains attached to the chromatin fraction of Balb/MK2 keratinocytes upon the extraction of the soluble components (nucleoplasm and cytoplasm). Chromatin-immunoprecipitation (ChIP) analysis shows that CDK4 occupies the regulatory sites of genes associated with chromosomal segregation, such as Aurkb (Aurora B) and Cenpp (Centromere Protein P). Moreover, gain- and loss-of-function experiments showed that the AurkB and Cenpp promoters are regulated through CDK4 binding. In line with these findings, studies in skin carcinogenesis revealed that transgenic expression of CDK4 in mouse epidermis induces chromosome instability (CIN) and centrosome amplification (CA), two events linked to overexpression of Aurora B. Moreover, Aurora-B has a crucial role in chromosome bi-orientation and the spindle-assembly checkpoint, whereas Cenpp is required for proper kinetochore function. Remarkably, a persistent dysregulation of Aurora B has been reported in numerous human cancers. Thus, our results suggest that CDK4 plays a role in the maintenance of chromosomal stability, implying that additional functions could be inhibited by therapeutically targeting CDK4. Our conclusions are supported by previous reports showing that pharmacological inhibition of CDK4 led to delayed progression from G2 to mitosis in Rb-positive and as well as Rb-negative cells. Citation Format: Sung Hyun Lee, Liliana R. Rodriguez, Paula L. Miliani de Marval, Marcelo L. Rodriguez-Puebla. Emergent functions of cyclin-dependent kinase 4 regulating aurora b and cenpp transcription [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5814.