1,25-DIHYDROXYVITAMIN-D-3 AND BREAST-CANCER - GROWTH-INHIBITION BY 2 ANALOGS (RO23-4319 AND RO23-7553) AND DETECTION OF RECEPTORS IN ROUTINELY FORMALIN-FIXED PARAFFIN-EMBEDDED MATERIAL

In addition to the regulation of calcium absorption and bone mineralization, the active form of vitamin D-3, 1,25-dihydroxyvitamin D-3 (1,25(OH)(2)D-3), has been shown to inhibit the proliferation and induce the differentiation of a wide range of normal and malignant cells via binding to a specific intracellular receptor. In this study, we demonstrated that the growth of estrogen receptor positive (MCF-7 and T47D) and negative (MDA-MB-231 and BT-20) human breast cancer cells was inhibited in a dose-dependent manner by 22-ene-1,25(OH)(2)D-3 (Ro23-4319) and 16-ene-23-yne-1,25(OH)(2)D-3 (Ro23-7553), two noncalcemic analogues of 1,25(OH)(2)D-3. Moreover, we showed that the antitumor effect exerted by the antiestrogen 4-hydroxytamoxifen was enhanced by Ro23-7553 in MCF-7 cells. Taken together, these results provide further evidence for the clinical interest of the noncalcemic analogues of 1,25(OH)(2)D-3 both for patients with estrogen receptor positive and negative breast tumors. These observations combined with the potential pronostic Value of the 1,25(OH)(2)D-3 receptor (VDR) status in breast cancer led us to test an immunohistochemical method performed on 32 routinely formalin-fixed paraffin-embedded breast tumor samples which were until now unusable for VDR detection. We compared this method, involving a pretreatment of the tissue sections in a microwave oven, with the conventional biochemical assay. Our results showed that breast tumors were massively stained (80% to 98% of the tumor cell nuclei) and that the parallelism observed between the staining intensity and the VDR concentration, could be proposed to either select a responsive population of patients or to carry out retrospective studies intended to specify the pronostic interest of VDR in breast cancer. We also demonstrated, as others, that no relationship existed between the presence of VDR and the age of the patients, the presence of estrogen and progesterone receptors and the lymph node involvement.