Abstract C60: Snail transcription factor contributes to bone metastasis in prostate and breast cancer cells

Prostate cancer that is hormone refractory and has metastasized preferentially to bone is the main cause of prostate cancer death, especially in African American men. Receptor activator of nuclear factor kappa B ligand (RANKL) and its receptor (RANK) contributes to bone metastatic lesions and bisphosphonates such as Zometa and Fosamax have been used as antagonists of RANKL for the treatment of breast and prostate cancer metastasis. African American men have the highest bone mineral density compared to any other race, and the role this may play in prostate cancer metastasis to bone is not clear. A better understanding of bone metastasis may lead to alternative treatment options for metastatic prostate cancer. Snail transcription factor is important early in development and in cancer cells and promotes cancer cell migration and progression by inducing epithelial mesenchymal transition (EMT). We have observed increased expression of Snail in prostate cancer bone metastatic human patient samples. We hypothesized that Snail can mediate EMT-mediated prostate cancer migration towards bone of high bone mineral density and mediate the vicious cycle of tumor-tumor microenvironment reciprocal interactions through calcium and RANKL signaling. We generated an EMT model for prostate and breast cancer utilizing the ARCaP human prostate and MCF-7 breast cancer cells overexpressing Snail and identified increased RANKL expression that was associated with increased osteoclastogenesis both in vitro and in vivo, as well as decreased bone volume and density. We utilized pre-molded bone discs which are allograft bone/polyurethane (PUR) composite bone void fillers with tunable properties that have advantage over existing bone implant models in that it contains bigger pore sizes that support rapid cellular infiltration and remodeling. We treated the bone discs with hydrochloric acid which decreased the bone density to a ratio of 1:1.18 for low (HCL-treated): high (untreated) bone density, which is quite close to the 1: 1.2 ratio seen in Caucasian vs African American men. Incubation of these bone discs with prostate or breast cancer cells overexpressing Snail led to increased calcium release from bone of high density as compared to low density. We are currently testing whether this increased calcium release in response to Snail may promote paracrine cell proliferation. Since Snail is not required by adult cells except during injury, targeting Snail that is mainly expressed by cancer cells may antagonize metastatic lesions in bone without affecting normal bone in other areas of the body. Citation Format: Basil A. Smith, Veronica Henderson, Christopher Coke, Jerald Dumas, Cimona Hinton, Manu Platt, Leland K. Chung, Majd Zayzafoon, Valerie A. Odero-Marah. Snail transcription factor contributes to bone metastasis in prostate and breast cancer cells. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C60. doi:10.1158/1538-7755.DISP13-C60