1,25-dihydroxyvitamin D3 and breast cancer.

Studies by this laboratory have demonstrated the presence of specific, high affinity 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) receptors both in surgical specimens of human breast cancer and in breast cancer cells in culture. We report here that 1,25-(OH)2D3 receptors were found in 54% of 230 human primary breast cancers. Although receptor levels are lower than those of oestrogen receptors, using a modified and more sensitive assay method, the apparent receptor concentration is increased without altering the receptor positivity rate. Also in preliminary studies on lymph node metastases and their primary tumours, the receptor positivity rate is higher in the lymph nodes. These findings suggest that metastatic cells may be selected for the presence of 1,25-(OH)2D3 receptors. These data, taken with the evidence that 1,25-(OH)2D3 and several of its metabolites inhibit the growth of human breast cancer cells in culture, exactly analogously with the effects of oestrogens on cancer cell growth in vitro and in vivo, indicate that 1,25-(OH)2D3 or its metabolites could have a role in the 'hormonal' therapy of metastatic human breast cancer.