Abstract 486: MicroRNA-30 family members inhibit breast cancer invasion, osteomimicry, and bone destruction by directly targeting multiple bone metastasis-associated genes

MicroRNAs (miRNAs), which are master regulators of gene expression, have emerged as key players in cancer metastasis. Here, we established miR-30 family members (miR-30a, miR-30b, miR-30c, miR-30d and miR-30e) as breast cancer bone metastasis suppressor genes. Low expression levels of miR-30s in primary tumors of breast cancer patients were associated with poor relapse-free survival. Additionally, miR-30s levels were significantly lower in estrogen receptor (ER)-negative/progesterone receptor (PR)-negative tumors than in their hormone-responsive counterparts. Overexpression of miR-30s in ER/PR-negative breast cancer cells resulted in the reduction of bone metastasis burden in vivo. MiR-30s overexpression also reduced tumor outgrowth, when tumor cells were implanted subcutaneously in animals. In vitro, miR-30s did not affect tumor cell proliferation, but inhibited tumor cell invasion. Furthermore, miR-30s restored bone homeostasis by reversing the in vitro effects of the tumor cell conditioned medium on stimulation of osteoclastogenesis and inhibition of osteoblastogenesis. We identified a number of genes associated with osteoclastogenesis stimulation (IL-8, IL-11), osteoblastogenesis inhibition (DKK-1), tumor cell osteomimicry (RUNX2, CDH11) and invasiveness (CTGF, ITGA5, ITGB3) that were direct and/or indirect targets for repression by miR-30s. Among these genes, integrin ITGA5 was a previously unknown miR-30 target. By silencing ITGA5 in ER-/PR-negative breast cancer cells, colonization of the bone marrow by tumor cells was drastically reduced in vivo. Overall, our data indicate that miR-30s employ multiple mechanisms to impede breast cancer bone metastasis. These findings may pave the way to a new field of therapeutic interventions in breast cancer patients with bone metastasis. Citation Format: Martine Croset, Francesco Pantano, Casina Kan, Edith Bonnelye, Francoise Descotes, Catherine Alix-Panabières, Charles Lecellier, Richard Bachelier, Nathalie Allioli, Saw See Hong, Kai Bartkowiak, Klaus Pantel, Philippe Clézardin. MicroRNA-30 family members inhibit breast cancer invasion, osteomimicry, and bone destruction by directly targeting multiple bone metastasis-associated genes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 486.