Androgen-Mediated Repression of the Maspin Tumor Suppressor Gene in Prostate Cancer

Abstract

This year in the United States, cancer is projected to cause one out of every four deaths. Prostate cancer alone is estimated to take the life of over 30,000 men. One area of intense research as a potential therapy against cancerous growth is in tumor suppressing genes, which function in cell cycle checkpoint responses, detection and repair of damaged DNA, protein ubiquitination and degradation, mitogenic signaling, cell specification, differentiation and migration, and tumor angiogenesis. One particular gene, the mammary serine protease inhibitor (maspin), is critically important in both breast and prostate cancer, which in the latter the gene is repressed entirely. However, the exact mechanism that leads to the repression of the maspin gene is not entirely understood. In my thesis work, I first showed that the maspin tumor suppressor gene was under direct regulation by the androgen receptor protein. By analyzing the quality and quantity of the mRNA produced under various growth conditions, we confirmed that the activation of the androgen receptor was critical for the repression of maspin. To do this, cell cultures were selectively grown with or without androgens and the mRNA was extracted, converted to cDNA, and RT-PCR was performed to analyze relative levels of maspin expression. I next attempted to verify that the androgen receptor was physically binding the promoter region of maspin by performing chromatin immunoprecipitation (ChIP) assays. After immunoprecipitating any chromatin fragments with the androgen receptor bound, a PCR to amplify the maspin promoter was completed. Obtaining a PCR product confirmed that the AR binds the androgen response element (ARE), repressing its expression.