Mechano-response via ATP alters calcium signaling in breast epithelial cells with oncogenic KRas mutation

Abstract

The majority of breast cancer patient deaths occur when tumor cells migrate away from the primary tumors and disseminate metastatically. Cancer cells at the invasive front mimic the behaviors of non-tumorigenic epithelial cells at wound edges but show less coordinated migration comparatively. While most wound healing studies use a timeframe of 24- 48 hours, our previous studies have shown that ATP released from wounded cells initiates a calcium (Ca2+) signal within seconds that spreads to neighboring cells through activation of the P2Y2 surface receptor. RNAseq data of MCF10A mammary epithelial cells with stepwise mutations of PTEN knockout and KRas activation alone or in combination, demonstrate that P2Y2 is downregulated specifically by active KRas. Fluorescence microscopy was used to measure Ca2+ signaling and mitochondrial membrane potential in parental and mutant MCF10A cells. Change in total fluorescence was measured and compared to baseline using Fluo-4, a Ca2+ fluorescent indicator, and TMRM (, methyl ester), a fluorescent mitochondrial membrane potential dye on Nikon analysis software. We show that KRas activation disrupts ATP stimulation and Ca2+ signaling. This change was further quantified using a FlexStation III plate reader with Fluo-4 to read specific fluorescent changes in Ca2+ after ATP addition. ATP-stimulated Ca2+ was also disrupted in other breast tumor cell lines harboring Ras activating mutations, MDA-MB-231 and MDA-MB-436, both showing a similar decrease in P2Y2 expression. These data show that ATP stimulation can be used to further understand the differences in Ca2+ signaling and mechanical-response between normal breast epithelial cells and cancer cells. Clarifying these molecular mechanisms could reveal targets for new cancer treatments, especially since 90% of human tumors are epithelial carcinomas.