No abstract

HN1 has previously been shown as overexpressed in various cancers. In Prostate cancer, it regulates AR signaling and centrosome-related functions. Previously, in two different studies, HN1 expression has been observed as inversely correlated with Cyclin B1. However, HN1 interacting partners and the role of HN1 interactions in cell cycle pathways have not been completely elucidated. Therefore, we used Prostate cancer cell lines again and utilized both transient and stable inducible overexpression systems to delineate the role of HN1 in the cell cycle. HN1 characterization was performed using treatments of kinase inhibitors, western blotting, flow cytometry, immunofluorescence, cellular fractionation, and immunoprecipitation approaches. Our findings suggest that HN1 overexpression before mitosis (post-G2), using both transient and stable expression systems, leads to S-phase accumulation and causes early mitotic exit after post-G2 overexpression. Mechanistically, HN1 interacted with Cyclin B1 and increased its degradation via ubiquitination through stabilized Cdh1, which is a co-factor of the APC/C complex. Stably HN1-expressing cells exhibited a reduced Cdt1 loading onto chromatin, demonstrating an exit from a G1 to S phenotype. We found HN1 and Cdh1 interaction as a new regulator of the Cyclin B1/CDK1 axis in mitotic regulation which can be explored further to dissect the roles of HN1 in the cell cycle.

Prostate cancer is one of the devastating diseases characterized by genetic changes leading to uncontrolled growth and metastasis of the cells of the prostate gland and affects men worldwide. Conventional hormonal and chemotherapeutic agents are effective in mitigating the disease if diagnosed at an early stage. All dividing eukaryotic cells require mitotic progression for the maintenance of genomic integrity in progeny populations. The protein kinases, upon activation and de-activation in an ordered fashion, lead to spatial and temporal regulation of the cell division process. The entry into mitosis along with the progression into sub-phases of mitosis is ensured due to the activity of mitotic kinases. These kinases include Polo-Like-Kinase 1 (PLK1), Aurora kinases, and Cyclin-Dependent-Kinase 1 (CDK1), among others. The mitotic kinases, among others, are usually overexpressed in many cancers and can be targeted using small molecule inhibitors to reduce the effects of these regulators on mechanisms, such as regulation of genomic integrity and mitotic fidelity. In this review, we attempted to discuss the appropriate functions of mitotic kinases revealed through cell culture studies and the impact of their respective inhibitors derived in pre-clinical studies. The review is designed to elucidate the growing field of small molecule inhibitors and their functional screening or mode of action at the cellular and molecular level in the context of Prostate Cancer. Therefore, studies performed specifically on cells of Prostatic-origin are narrated in this review, culminating in a comprehensive view of the specific field of mitotic kinases that can be targeted for therapy of Prostate cancer.

Prostate cancer cells need androgens to grow and maintain like normal prostate cells, both utilize that Androgen Receptor (AR) function. Androgen receptor (AR) is expressed throughout the prostate cancer progression plays a critical role as a transcription factor in castration-dependent stages of disease. AR also interacts to many cellular proteins, including p53, to regulate apoptosis. Further, as the stabilization of p53 protein triggers apoptosis, p53 interacting small molecules such as Nutlin3a, are interpreted as cancer therapeutics. In this study, to find out how Nutlin3a-mediated p53 stabilization effect on AR signaling. Here, we investigated the dynamics of p53 binding to transcriptional targets of AR, and further investigated the variations of AR intracellular localization as well as transactivation in the presence of Nutlin3a. To do this, the changes in AR transactivation were investigated via luciferase reporter assay, which was performed by treating LNCaPs with different doses of Nutlin3a and resulted that transactivation was suppressed by Nutlin3a in a dose dependent manner. AR transactivation and sub-cellular localization were also studied by immunofluorescence assay and found that cytoplasmic-nuclear fractionation-coupled western blot analysis showed that Nutlin3a inhibits AR phosphorylation and nuclear translocation regardless of androgens.