Abstract 4968: Chemotherapy up-regulates RANK-RANKL signaling in breast cancer cells.

Abstract

Abstract Chemotherapy has been the mainstay of cancer treatment for so many years and so do the increasing resistance to it. Recent studies emphasize the importance of cytokines in breast cancer therapy resistance and how targeting cytokines or their receptor may prove to be a better therapeutic regimen. This study focuses on the role of receptor activator of NFkB ligand (RANKL), recently been observed to provide survival benefits to cancer cells and helps in mammary stem cell maintenance. To the best of our knowledge the modulations of RANK and RANKL in response to chemotherapy has not been evaluated before. Our preliminary studies with drug-resistant cells showed higher expression of RANK and RANKL both in vitro in cells as well as in vivo in tumors formed by these cells, suggesting a role of this RANKL mediated signaling in breast cancer therapy resistance. Given that RANK and RANKL are expressed in aggressive breast tumors and this signaling provides survival benefits to cancer cells, we hypothesized that chemotherapy up-regulates RANK-RANKL signaling in breast cancer cells which eventually makes breast cancer cells resistant to further chemotherapy providing evasion to therapy. To investigate this, we monitored the expression of RANKL in murine 4T1, CL66 and MDA MB-231, MCF-7; human breast cancer cells lines after treatment with two commonly used drugs doxorubicin and paclitaxel for breast cancer treatment. We observed that both drugs up-regulate RANKL expression in these cells. To examine if the expression of RANK also changes after drug treatment in these cells, we treated 4T1 and Cl66 cells with paclitaxel for 4, 8 and 12 hours. We observed an increase in the expression of RANK in these cells in a dose- and duration-dependent manner. 4T1 and Cl66 along with MDA MB-231 and MCF-7 were also treated with both paclitaxel and doxorubicin to evaluate if the change in receptor and ligand expression was drug-dependent. Our data showed that both the drugs up-regulate RANKL at mRNA (qRT-PCR) and protein levels (Immunofluorescence) in Cl66 and 4T1 cells. This up-regulation was as early as 4hrs (at mRNA level) after drugs treatment and the expression decreases after 8 hrs, suggesting an early transcriptional up-regulation. Our data suggest that increased expression of both RANK and RANKL in the breast cancer cells following chemotherapy may contribute to the activation of RANK-RANKL signaling in breast cancer and targeting this signaling might provide a novel adjuvant therapeutic regimen. Citation Format: Bhawna Sharma, Michelle L. Varney, Rakesh K. Singh. Chemotherapy up-regulates RANK-RANKL signaling in breast cancer cells. [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 4968. doi:10.1158/1538-7445.AM2013-4968