Paracrine signaling from the breast cancer cells stimulates the cell proliferation and Stat3 phosphorylation in non-cancerous mammary epithelial cells and is blocked by dietary agent, curcumin.

A126

Breast cancer cells coexist with normal mammary cells. It is unclear whether breast cancer cells promote pre-neoplastic phenotypes of surrounding normal mammary cells and whether there is any preventive approach to inhibit this process of carcinogenesis. We studied the possible stimulation effects of paracrine signaling from breast cancer cells to non-cancerous mammary epithelial cells. Media was conditioned in the presence of metastatic human breast cancer cells, MDA-MB-231 with high levels of activated Signal Transducers and Activators of Transcription 3 (Stat3). The persistent tyrosine phosphorylation of Stat3 is frequently found within breast carcinoma. The conditioned media from MDA-MB-231 cancer cells was then used to treat MCF-10A, a non-cancerous breast epithelial cell line. Western blot analysis demonstrated that soluble factor(s) secreted by MDA-MB-231 breast cancer cells were sufficient to amplify p-Stat3 (Y705) levels within MCF-10A cells and increased cell proliferation, and global DNA methylation changes in MCF-10A cells treated with conditioned media from MDA-MB-231 breast cancer cells. These results also prompted us to question which specific cytokines were responsible for this boost in Stat3 phosphorylation. ELISA analysis confirmed low levels of IL-6 secretion by MCF-10A and high levels of IL-6 secretion by MDA-MB-231. Human recombinant IL-6 was added to MCF-10A cells and the stimulation of Stat3 phosphorylation and cell proliferation were observed.
 >Treatment of MCF-10A cells with 10 μM JSI-124, a Jak/Stat3 inhibitor, blocked increasing Stat3 phosphorylation and cell proliferation after treatment with conditioned media. Further, we demonstrated for the first time that the addition of dietary and chemoprevention agent, curcumin blocks the increase in Stat3 phosphorylation and cell proliferation in MCF-10A cells treated with conditioned media from MDA-MB-231 breast cancer cells. Curcumin not only blocks the paracrine signaling stimulatory effects from MDA-MB-231 cells on MCF-10A cells but also inhibits the cell viability of MDA-MB-231 breast cancer cells. We will further examine whether curcumin can inhibit global DNA methylation changes in MCF-10A cells treated with conditioned media from MDA-MB-231 cancer cells.