Abstract P4-08-24: Palmitoylation of Flotillin-1 contributes to Breast Cancer Metastasis

Abstract

Abstract BACKGROUND Breast Cancer metastasis results in the majority of cancer-related mortality. Flotillin-1 is overexpressed in numerous solid tumors and has been demonstrated to contribute to invasion and metastasis in breast cancer. Though its expression alone has been associated with metastasis, there has yet to be any investigation as to how certain post-translational modifications can affect its metastatic capabilities. Flotillin-1 is modified through palmitoylation, a post-translational modification essential for protein stability, processing, and localization. By generating a palmitoylation defective mutant of flotillin-1, we have demonstrated that flotillin-1 palmitoylation contributes to its stability and metastatic capabilities in both 3D and in vivo models of invasion and metastasis. MATERIALS AND METHODS Flotillin-1 wild type or palmitoylation defective C-34-A mutants were expressed in stable flotillin-1 knockdown MDA-MB-231 and SUM-159 triple negative breast cancer cells. These cells were subjected to 2D invasion chambers and 3D collagen invasion assays. Further, both wild type and C34A expressing cells were used for experimental lung metastases in mice by tail vein injection. 2-bromopalmtiate (50µM) was used as a chemical palmitoylation inhibitor and MG-132 (10µM) for proteasomal inhibition. RESULTS Invasion in stable knockdown cells was restored by re-expression of flotillin-1, but not by follitillin-1 C34A. We further observed a significant decrease in lung metastasis in flotillin-1 C34A cells compared to wild type flotillin-1. Flotillin-1 C34A expression led to a significant decrease in protein stability, which was restored by MG-132. CONCLUSION Flotillin-1 palmitoylation contributes to its stability and subsequent metastatic capabilities in breast cancer cells and experimental metastasis models. Thus, flotillin-1 palmitoylation could be a promising target for breast cancer metastasis. Citation Format: Bryan McClellan. Palmitoylation of Flotillin-1 contributes to Breast Cancer Metastasis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-08-24.