Abstract 2047: CDK10 promotes tumour growth and chemoresistance in colorectal cancer, and is a potential target for treatment

Abstract

Abstract CDK10 is a novel and relatively poorly characterized member of the CDC2 family of kinases. CDK10 has been reported to be involved in the regulation of the G2/M phase of the cell cycle. Its role in cancer is unclear. A meta-analysis of gene expression profiling studies has consistently demonstrated higher expression of this protein in colorectal cancer (CRC) but its role is unknown. In this study, we were interested in examining the role of CDK10 in growth, apoptosis, chemoresistance, and as a therapeutic target in CRC. CRC cell lines stably overexpressing CDK10 wild type (WT) as well as a kinase defective/dominant negative (DN) form of CDK10 were established in CRC cell lines RKO, HCT-15 and MIP101. Knockdown of CDK10 was achieved via siRNA. MTS and colony-forming assays were used to examine the response to 5-Fluorouracil (5-FU); TUNEL, caspase 3/7 assays, for apoptosis; and signaling events by immunoblotting. Cell growth in vivo was monitored after injection of cell lines into the flanks of Nude mice. To examine CDK10's role as a potential target, SCID mice implanted SC with patient-derived CRC were injected with lentiviral siRNA targeting CDK10 and tumor growth was examined. Overexpression of CDK10 WT in RKO cells resulted in greater in vitro cell proliferation in comparison to either the DN or the control cells. It also inhibited apoptosis by 32%, while overexpression of the CDK10 DN protein was associated with an augmentation of apoptosis (>50%). Knockdown of CDK10 via siRNA confirmed a significant decrease in cell viability (20-60%) and a significant increase in apoptosis (>80%). This was associated with a downregulation of Bcl-2 and Bcl-xL expression. Interestingly, inhibition of apoptosis in CDK10 WT RKO cells could be achieved by inhibiting the expression of Bcl-2 and Bcl-xL by siRNA. The sensitivity of CRC cells to 5-FU was also dramatically reduced in cells overexpressing CDK10, as demonstrated by the significant higher IC50 in these cells. Colony-forming assay showed involvement of the kinase activity in 5-FU resistance since CDK10 DN HCT-15 cells displayed higher sensitivity and the CDK10 WT HCT-15 higher resistance to 5-FU. In line with the in vitro results, in vivo studies revealed that HCT-15 tumor xenografts expressing CDK10 WT have a significantly greater rate of growth than tumors expressing basal levels of CDK10. Interestingly, tumors of CDK10 DN cells had the slowest rate of growth. Furthermore, in vivo knockdown of CDK10 significantly impaired the growth of human SC implanted CRC tumors, as compared to control, with a ΔT/ΔC close to 0% by 26 days of treatment. CDK10 appears to be involved in the pathogenesis of CRC by influencing cell growth, apoptosis and chemotherapy resistance, in part, through its kinase active site. In addition, in vivo results using patient-derived tumors showed a significant reduction in tumor growth, following siRNA knockdown of CDK10, thereby demonstrating it to be a potential target for therapy in CRC. Citation Format: Louis-Bastien Weiswald, Mohammad R. Hasan, Mahbuba Rahman, Clarissa Pasiliao, Isabella T. Tai. CDK10 promotes tumour growth and chemoresistance in colorectal cancer, and is a potential target for treatment. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2047. doi:10.1158/1538-7445.AM2015-2047