Abstract 19191: Transfer of MicroRNAs From Cardiomyocytes Prevents the Growth of Cancer Cells

The sporadic incidence of malignancies in the heart led us to test the possibility that translocation of miRs from cardiomyocytes to cancer cells may oppose the expansion of tumors in the myocardium. miR-1, miR-133a, and miR-499 were highly expressed in myocytes but were barely detectable in MCF7 breast cancer cells. To establish whether miRs migrated from myocytes to MCF7 via gap junction channels, the two cell classes were cultured together. In comparison with MCF7 plated alone, the quantity of miR-1 and miR-133a in MCF7 co-cultured with myocytes increased 45-fold and 20-fold, respectively. However, the expression of miR-499 was only 4-fold higher in MCF7 seeded with myocytes. Coupling with cardiomyocytes decreased by 20% the fraction of Ki-67-positive MCF7. To determine the relevance of gap junctions for the translocation of miRs, Cx43 was downregulated in MCF7 by shRNA. The increase in miR-1 and miR-133a in co-cultured MCF7 was attenuated but not abolished following Cx43 silencing. Unexpectedly, silen...