Of note, the VDR-KD cells were consistently non-responsive to vitamin D treatment in the in vitro experiments, which provides evidence that the growth suppression seen in VDR-KD cells in vivo is independent of vitamin D. The bone microenvironment provides a fertile soil for breast cancer cells, and bone is a preferred target organ for breast cancer metastasis [7, 36, 37]. The gene discussed is VDR; the disease is breast carcinoma.