Epigenetic Regulation of Alternative Splicing in Cancer

Prostate cancer is the most frequently diagnosed cancer among men and the second leading cause of cancer death in the United States. Major cause of mortality and morbidity is due to the metastasis of this cancer to the secondary organs. Identification of potential molecular targets and pathways is essential to devise effective therapeutic strategies to cure metastatic prostate cancer. A closer look at molecular processes such as alternative splicing and epigenetic regulation would provide useful insight into the mechanistic controls of tumor dissemination.\ud Aberrant methylation and dysregulated alternative splicing play a major role in tumor progression but scientific evidence of a definite link between the two is yet to be found. In our study we report that a differential methylation of four different sites in the intragenic region of CXCR3 regulates its alternative splicing. To showcase this proof of principle, a bichromatic reporter minigene construct with a nucleotide switch at the differentially methylated cytosines to mimic the observed methylation change was used. The unique property of this construct helps obtain a quantifiable metric of the splice ratio for a change in every cytosine moiety and compute a dose dependent effect for every extra base pair altered. It was identified that a critical methylation ratio is essential for a spice switch of CXCR3 in prostate cancer cells. In addition, the synergistic effect of methylation and a specific micro-environment on the phenotypic expression of the cell was also tested. The functionality of this construct to provide a snapshot on the effect of an external stimulus on the splice ratio will provide with a useful tool in obtaining quick data on factors that influence splicing in the context of the epigenome. In-vivo studies in the future will identify the propensity of invasion or arrest of tumor cells in light of its splice axis.\ud PUBLIC HEALTH OVERVIEW : Prostate cancer is the second leading cause of death in the United States alone. The quality of life of patients in the terminal cancer stages is poor and the survival rate is very low. Current therapeutic options do not improve the quality of life and improve survival rate only marginally. This study aims at identifying potential therapeutic targets with prognostic capabilities.\u