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 mineraliz ation, 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 th e differentiation of a wide range of normal and malignant cells via bi nding to a specific intracellular receptor. In this study, we demonstr ated that the growth of estrogen receptor positive (MCF-7 and T47D) an d negative (MDA-MB-231 and BT-20) human breast cancer cells was inhibi ted in a dose-dependent manner by 22-ene-1,25(OH)(2)D-3 (Ro23-4319) an d 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 exert ed by the antiestrogen 4-hydroxytamoxifen was enhanced by Ro23-7553 in MCF-7 cells. Taken together, these results provide further evidence f or the clinical interest of the noncalcemic analogues of 1,25(OH)(2)D- 3 both for patients with estrogen receptor positive and negative breas t tumors. These observations combined with the potential pronostic Val ue 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 forma lin-fixed paraffin-embedded breast tumor samples which were until now unusable for VDR detection. We compared this method, involving a pretr eatment of the tissue sections in a microwave oven, with the conventio nal biochemical assay. Our results showed that breast tumors were mass ively stained (80% to 98% of the tumor cell nuclei) and that the paral lelism observed between the staining intensity and the VDR concentrati on, could be proposed to either select a responsive population of pati ents or to carry out retrospective studies intended to specify the pro nostic interest of VDR in breast cancer. We also demonstrated, as othe rs, that no relationship existed between the presence of VDR and the a ge of the patients, the presence of estrogen and progesterone receptor s and the lymph node involvement.