Abstract 82: Analysis of the role of MDM2 in regulation of cell cycle arrest through p21 pathways in LNCaP-MST cells using PCR array

Abstract

Abstract Cell cycle checkpoints are imperative for assuring genomic fidelity and integrity during cell division. In normal cells, the cell cycle arrest occurs in response to nuclear DNA damage via activation and inactivation of a series of cell cycle regulatory molecules that can impact the transition from G1 to S phase and G2 to M phase. However, in cancerous cells, this process is disrupted resulting in uncontrolled cell proliferation and resistance to apoptosis. Therefore, cell cycle regulatory molecules are accepted as suitable targets for drug development and cancer treatment. It has been well known that overexpression of MDM2, a negative regulator of p53, will eventually lead to the inactivation of cell cycle control and loss of apoptotic ability in many tumors. In this study, we aimed to investigate the effectiveness of MDM2 inhibition in mediating cell cycle arrest through p53 dependent pathways by using the MDM2 transfected prostate cancer cells (LNCaP-MST). During our experiments the LNCaP-MST cells were treated for 24 hrs with 20 uM Nutlin-3, a small molecule inhibitor of MDM2/p53 interaction. The impact of Nutlin-3 treatment on the gene expression profile of LNCaP-MST cells was established by using the cell cycle pathway specific PCR array. Our study clearly demonstrates a significant increase of p21 gene expression after Nutlin-3 treatment, which indicates a possible restoration and release of the transcriptional activity of p53 in LNCaP-MST cells. In addition to the elevation of p21, a significant increase in the expression of Cyclin-Dependent Kinase 4 Inhibitor B (CDKN2B) along with multiple folds increase in the expression of Growth Arrest and DNA Damage 45 (GADD45A) genes were also found. These results clearly point towards efficient initiation of cell cycle arrest mechanisms in LNCaP-MST cells, possibly through p21 and CDKN2B mediated inhibition of the CDKs (cyclin dependent kinases). In addition, it appears that MDM2 inhibition may effectively block both G1 to S and G2 to M transition and cause DNA damage through apoptosis that could lead to the death of LNCaP-MST cells. Activation of the above outlined mechanisms following MDM2 inhibition is quite evident due to increased expression of GADD45A and decreased levels of anti-apoptotic B-cell lymphoma 2 (Bcl-2) genes. Our results offer convincing evidence towards the effectiveness of MDM2 inhibition in causing cell cycle arrest and apoptosis during cancer treatment. (This research was supported by the generous funds provided by the Royal Dames of Cancer Research Inc., Ft. Lauderdale, Florida) Citation Format: Khalid Alhazzani, Ali Alaseem, Thiagarajan Venkatesan, Appu Rathinavelu. Analysis of the role of MDM2 in regulation of cell cycle arrest through p21 pathways in LNCaP-MST cells using PCR array. [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 82. doi:10.1158/1538-7445.AM2015-82