Natural Compounds as a Promising Therapeutic Agent for SPOP Downregulated Breast Cancer

Breast cancer is the second most deadly type of cancer for women in America. Due to this, there is a pressing need to investigate and develop a better treatment plan for those afflicted by it. There are numerous studies that show a downregulation of the E3 ubiquitin ligase Type POZ Protein (SPOP) for up to 70% of breast cancer patients. This demonstrates that, in breast cancer, SPOP is a vital tumor suppressor gene. In previous research projects, our lab has shown that SPOP targets GLI3 for ubiquitination and degradation which subsequently places a restraint on SHH signaling. Furtermore, we have shown that SPOP mutations lead to a upregulation of GLI3 and subsequent hyperactivated SHH signaling in prostate cancer. Since SPOP is downregulated in a large number of breast cancer patients, we hypothesize that SPOP downregulated breast cancer tumors would also display hyperactivated SHH signaling. Additionally, we hypothesize that SPOP downregulated breast cancer patients will benefit from therapeutics that specifically target the SHH signaling pathway. To characterize the effect of SPOP downregulation in breast cancer, we used a lentivirus with shRNA complementary to SPOP to generate a stable MCF-7 SPOP knockdown cell line. Proliferation assays were utilized to first confirm that SPOP knockdown promotes enhanced cell proliferation. Next, quantitative PCR was used to demonstrate that SPOP knockdown leads to an upregulation of GLI3 target genes. To find a novel treatment strategy for SPOP downregulated breast cancer, a natural compound library was used. Through the screen and subsequent quantitative PCR analysis, we identified novel therapeutic natural compounds that specifically target SPOP downregulated MCF-7 cells in a manner that involves disruption of GLI3-dependent SHH signaling. Our findings thus give necessary insight into novel treatment strategies for patients suffering from SPOP downregulated breast cancer.