Abstract 2090: Novel role of STAT-3 in anoikis resistance and metastasis in melanoma cells in vitro and in vivo

Abstract

Abstract Anoikis is an anchorage-independent cell death. Resistance to anoikis is one of the key features of metastatic cells. The role of STAT-3 in anoikis resistance in various melanoma cells was analyzed in the current study. Significant proportion of SK-MEL-28, SK-MEL-2, MeWo, SK-MEL-5 and B16-F0 cells resisted anoikis when grown under anchorage-independent conditions. Cells that resisted anoikis were observed to a have higher rate of migration and invasion as compared to the cells grown under anchorage dependent conditions. The anoikis resistant cells also exhibited significantly higher expression and phosphorylation of STAT-3 at Tyr 705 than the cells that were attached to the basement membrane. Treatment of these cells with IL-6, a cytokine which phosphorylates STAT-3, prevented the induction of anoikis. STAT-3 inhibitors AG490 and PL induced anoikis in a concentration-dependent manner in anoikis resistant cells, whereas IL-6 blocked anoikis. Over-expression of STAT-3 by transfection in SK-MEL-28 and SK-MEL-2 cells significantly increased the anoikis resistance, confirming the role of STAT-3 in anoikis resistance. On the other hand, silencing STAT-3 in SK-MEL-28, SK-MEL-2, SK-MEL-5 and MeWo cells decreased the potential of cancer cells to resist anoikis. Furthermore, STAT-3 (-/-) melanoma cells were more sensitive to anoikis, as compared to cells overexpressing STAT-3 (+/+) cells. STAT-3 (-/-) SK-MEL-28 cells and the SK-MEL-28 cells that were treated with PL completely failed to develop tumors when injected subcutaneously in immune-compromised mice. Moreover, these cells also failed to metastasize when injected intravenously. On the other hand, anoikis resistant wild type cells not only formed aggressive tumors subcutaneously but also highly metastasized when injected intravenously. The metastasis was confirmed by H & E staining. In summary, our results establish STAT-3 as a critical player that renders anoikis resistance to pancreatic cancer cells and enhance their metastasis potential. [Supported in part by R01 grant CA129038 (to S.K.S) awarded by the National Cancer Institute]. Citation Format: Neel Manoj Fofaria, Sanjay K. Srivastava. Novel role of STAT-3 in anoikis resistance and metastasis in melanoma cells in vitro and in vivo. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2090. doi:10.1158/1538-7445.AM2014-2090