Abstract 2709: Functional Role of FKBP51 in malignant progression of melanoma.

Abstract

Abstract FKBP51 is a high molecular weight FK506-binding protein involved in the regulation of diverse biological processes. Its aberrant expression and pathological implications has been reported in some cancer types; however, its role in malignant melanoma has remained underexplored. In this study, we investigated the functional role of FKBP51 in melanoma pathogenesis by performing in vitro and in vivo studies. FKBP51 expression was observed in majority of primary and derivative melanoma cell lines. Interestingly, a greater expression of FKBP51 was detected in metastatic derivative lines (A375SM and FEMX-I) as compared to their respective parental cells (A375P and FEMX-V). Next, we stably repressed the expression of FKBP51 in A375SM and FEMX-I cells through short-hairpin RNA (shRNA)-mediated silencing. FKBP51 repression led to a decrease in growth and clonogenicity, in part, through suppression of cell cycle progression and induction of apoptosis. A reduced motility and invasion was also observed in both the FKBP51-silenced melanoma cell lines. Immunoblot analyses demonstrated loss of mesenchymal markers and elevated expression of epithelial markers in FKBP51-silenced cells, indicating a role of FKBP51 in epithelial to mesenchymal transition of melanoma cells. When injected subcutaneously into nude mice, FKBP51-silenced A375SM cells displayed significant inhibition of tumor growth as compared to the control cells. Immunohistochemical analysis of tumor tissues demonstrated a decrease in the proliferating (Ki67 positive) cells and increased numbers of apoptotic (TUNEL positive) cells in FKBP51-silenced A375SM as compared with control tumors. Furthermore, low vessel density and infiltration of myeloid derived suppressor cells (MDSC) was observed in tumors formed by FKBP51-silenced cells as examined by isolectin lectin B4 (Griffonia simplicifolia isolectin B4) and Gr-1 staining, respectively. Notably, tail vein injection of FKBP51- silenced cells produced no metastatic lesions in lungs, while significant metastases was observed in lungs of mice injected with control cells. Estimation of interleukin-8 (IL-8/CXCL-8), a chemokine previously associated with melanoma growth, metastasis and angiogenesis, demonstrated its decreased production in FKBP51-silenced cells and derived tumors. In conclusion, our study provides experimental evidence to support the functional significance of FKBP51 in malignant progression of human melanoma. Citation Format: Gurpreet Kaur, Sanjeev K. Srivastava, Sumit Arora, Arun Bhardwaj, Steven McClellan, Jonathan G. Scammell, William E. Grizzle, Laurie B. Owen, Oystein Fodstad, Ajay P. Singh, Seema Singh. Functional Role of FKBP51 in malignant progression of melanoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2709. doi:10.1158/1538-7445.AM2013-2709