Suppression of miRNA-708 by polycomb group promotes metastases by calcium-induced cell migration

The progression of cancer to metastatic disease is a major cause of death. We identified miR-708 being transcriptionally repressed by polycomb repressor complex (PRC2)-induced H3-K27 trimethylation in metastatic breast cancer. miR-708 targets the endoplasmic reticulum protein neuronatin (Nnat) to decrease intracellular calcium (Ca2+) level, resulting in reduction of activation of ERK and FAK, decreased cell migration, and impaired metastases. Functional complementation experiments with Nnat-3’UTR mutant, which is refractory to suppression by miR-708, rescued cell migration and metastasis defects. In breast cancer patients, miR-708 expression was decreased in lymph node and distal metastases, suggesting a metastasis-suppressive role. Our findings uncover a mechanistic role for miR-708 in metastasis and provide a rationale for developing miR-708 as a therapeutic agent against metastatic breast cancer. Sequencing miRNAs from Human breast cancer cells: MCF10A, MCF7, MDA-MB-231, MDA-MB-LM2