Activation of Estrogen Receptor Alpha by Decitabine Inhibits Osteosarcoma Growth and Metastasis

Osteosarcoma is a malignant tumor in the bone that originates from normal osteoblasts or osteoblast precursors. Normal osteoblasts express estrogen receptor alpha (ERa); however, osteosarcomas do not due to promoter DNA methylation. Here we show that treatment of 143B osteosarcoma cells with Decitabine (DAC, 5-Aza-2'-deoxycytidine) induces expression of ERa and leads to decreased proliferation and concurrent induction of osteoblast differentiation. DAC exposure reduced protein expression of metastasis-associated markers VIMENTIN, SLUG, ZEB1, and MMP9, with a concurrent decrease in mRNA expression of known stem cell markers SOX2, OCT4, and NANOG. Treatment with 17b-estradiol (E2) synergized with DAC to reduce proliferation. Overexpression of ERa inhibited proliferation and induced osteoblast differentiation, whereas knockout of ERa by CRISPR/Cas9 prevented the effects of DAC. In an orthotopic model of osteosarcoma, DAC inhibited tumor growth and metastasis of 143B cells injected into the tibia of NOD scid gamma (NSG) mice. Furthermore, ERa overexpression reduced tumor growth and metastasis, and ERa knockout prevented the effects of DAC in vivo. Together, these experiments provide pre-clinical evidence that the FDA-approved DNA methylation inhibitor DAC may be repurposed to treat osteosarcoma patients based on its efficacy to decrease proliferation, to induce osteoblast differentiation, and to reduce metastasis to visceral organs.

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