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Receptors for 1,25-dihydroxyvitamin D3 have been shown to exist in cultured breast cancer cells and in primary breast cancers. It is reported here that 1,25-dihydroxyvitamin D3 receptor (1,25-DR) was present in 80% of 54 unselected breast cancers. The concentration of 1,25-DR in the 43 receptor-positive tumors was 1.9 +/- 0.4 fmol/mg protein (S.E.). There was no correlation between 1,25-DR presence or concentration and the age of the patient or the concentration of estrogen, progesterone, androgen, or glucocorticoid receptors. 1,25-DR was also found in two of three renal cortical carcinomas but only in three of 14 gastrointestinal tract carcinomas. The relatively low concentration of 1,25-DR in these breast cancers, compared with that found in cultured breast cancer cells, is partially explained by incomplete "exchange" with occupied receptors. Since the serum vitamin D-binding protein is not precipitated from serum itself or from tissue homogenates using the polyethylene glycol method, artifactual 1,25-DR levels due to the inevitable contamination of tissue specimens with this protein can be excluded. These findings indicate that 1,25-DR is not a nonspecific marker of cancer. The high frequency of 1,25-DR in the breast cancers may be related to the calcium-transporting ability of breast cancer cells which allows them to grow as osteolytic metastases.

It has been demonstrated previously that several human cancer cell lines possess specific, high affinity receptors for 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3, calcitriol] and that 1,25-(OH)2D3 and certain of its metabolites inhibit the growth in vitro of several human breast cancer and malignant melanoma cell lines, i.e., analogous to the effect of estrogens on breast cancer. Furthermore, it has been shown that 1,25-(OH)2D3 and one of its synthetic analogues prolonged the survival in mouse leukemia, induced by inoculation of leukemic cells into syngeneic mice. However, until now no growth-inhibitory effect of 1,25-(OH)2D3 has been demonstrated in vivo for human cancer cells or for solid cancers. This paper describes the suppression by 1,25-(OH)2D3 of the growth of human cancer cell-derived xenografts in immune-suppressed mice. However, the 24-hydroxylated metabolite and the 24-difluorinated analogue of 1,25-(OH)2D3, both of which are active in vitro, were ineffective in this xenograft model system. The suppression by 1,25-(OH)2D3, which was achieved without significant toxicity, was observed with xenografts derived from two 1,25-(OH)2D3 receptor-positive cell lines (COLO 206F, derived from a colonic cancer, and COLO 239F from a malignant melanoma) but not in those from a receptor-negative line (RPMI 7932, also derived from a malignant melanoma). These studies demonstrate that pharmacological doses of 1,25-(OH)2D3 can be tolerated in the presence of a low calcium diet and that these doses can suppress the growth of human solid xenograft tumors in vivo. This is the first report of 1,25-(OH)2D3 growth suppression of solid tumors derived from human cancer cells in an in vivo model system, and it supports the hypothesized potential of the hormone in the treatment of 1,25-(OH)2D3 receptor-positive human cancers.

Receptors for 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] have been described in several human breast cancer cell lines and more recently in human melanoma. The presence of 1,25-(OH)2D3 receptor (1,25-DR) in two cultured breast cancer cell lines was associated with receptors for calcitonin, another hormone thought to have effects on calcium handling. Therefore, it seemed important to examine a range of established human cancer cell lines for the presence of receptors for 1,25-(OH)2D3 and calcitonin. Thirty-three cancer cell lines were examined. 1,25-DR was found to be present in 23 lines, while calcitonin receptors were not detected in any of them. The 1,25-DR from several cell lines sedimented at about 3.5S in sucrose density gradients, had the appropriate specificity for vitamin D metabolites, had Kds of 0.8 to 2.2 x 10(-11) M, and had receptor concentrations of 12 to 99 fmol/mg protein. Ten malignant melanoma and nine colonic carcinoma lines constituted the largest groups of carcinoma cell lines, and seven and eight, respectively, of these were 1,25-DR positive. The high frequency of 1,25-DR positivity in the cultured colonic carcinoma cells is quite different from the low frequency of 1,25-DR in primary colonic carcinomas. It was also interesting that both of two cell lines derived from patients who had had both bone metastases and malignant hypercalcemia were 1,25-DR positive. These various cell lines may provide useful models for the examination of 1,25-(OH)2D3 action in vitro.

Five human breast cancer cell lines (MCF 7, T 47D, BT 20, MDA 157, and MDA 231) and a human breast epithelial cell line (HBL 100) have been found to contain specific high-affinity receptors for 1,25-dihydroxyvitamin D3, Kd values ranged from 0.6 to 2.0 X 10(-11) M and receptor concentration from 31 to 150 fmol/mg cytosol protein. Two of the breast cancer lines (MCF 7 and T 47D) contain specific high-affinity receptors for calcitonin and a calcitonin-responsive adenylate cyclase, which have been characterized with the aid of salmon, eel, and human calcitonins and in several substituted analogues of human calcitonin. The 1,25-dihydroxyvitamin D3 receptor may reflect a normal property of the breast cell. Breast cancer cell lines provide a useful source of 1,25-dihydroxyvitamin D3 receptors. Their coexistence with a calcitonin receptor and biological response in some breast cancers offers the opportunity to investigate new aspects of breast cancer endocrinology.

Specific high-affinity 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] receptors, which can undergo hormone-dependent activation and nuclear localization, have been demonstrated in a wide variety of established human cancer cell lines and surgically obtained human cancer tissues. 1,25-(OH)2D3 has been reported by some workers to stimulate cancer cell replication at low "physiological" concentrations and by ourselves and others to inhibit at higher concentrations. We report here that 1,25-(OH)2D3 had a biphasic effect on the replication of two distinct human cancer cell lines, i.e., the breast cancer T-47D and the malignant melanoma MM96, an effect analogous to that of estrogens on the breast cancer cell line MCF-7. These inhibitory effects were accompanied by marked morphological changes. Furthermore, two known metabolites of 1,25-(OH)2D3, i.e., 1,24,25-trihydroxyvitamin D3 and 1,25,26-trihydroxyvitamin D3, which compete for binding to the 1,25-(OH)2D3 receptor, did not stimulate but were almost equipotent with 1,25-(OH)2D3 in inhibiting the replication of both cell lines. The stimulatory but not the inhibitory effect of 1,25-(OH)2D3 was abolished by cortisone. These 1,25-dihydroxyvitamin D3 metabolites show promise for the inhibition of cancer growth, analogous to the effect of estrogens and antiestrogens in breast cancer but with potential application in a much wider range of human cancers.

Specific high affinity receptors for 1,25-dihydroxyvitamin D3 are present in several human breast cancer cell lines, and this hormone can regulate the replication of these cells. These receptors are also present in primary breast carcinomas. The present study has resulted from the follow-up for up to 68 mo of 263 women, who had had 1,25-dihydroxyvitamin D receptor (1,25-DR) levels measured in their primary tumors. Survival data on 191 women were correlated with the levels of 1,25-DR and other steroid hormone receptors, menopausal status, and age by life table analysis. Survival was not affected by 1,25-DR level in either absolute terms or relative levels. However, the late development of lymph node metastases in eight of 47 individuals was correlated with the 1,25-DR level (P = 0.05). There was no correlation between 1,25-DR or other hormone receptor levels and the development of hypercalcemia or bone metastases in the small number of individuals so affected. As we had observed previously, there was no correlation between the level of 1,25-DR and that of the other steroid hormones. These data show that the presence of 1,25-DR in primary breast cancers is independent of other prognostic indicators and, inasmuch as it correlated with late lymph node metastasis, may be an adverse prognostic indicator.

Specific, high affinity receptors for 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] have been demonstrated in human breast cancer cells. In addition, 1,25-(OH)2D3 has been shown to inhibit replication in some human breast cancer cell lines, although the mechanism(s) of this anti-tumor activity remain undefined. There is currently considerable interest in the role of autocrine growth factors in the control of breast cancer cell proliferation and the effects of steroid hormones on their production, receptor binding, and action. Since the epidermal growth factor (EGF) receptor mediates the effects of both EGF and the autocrine growth factor, alpha-transforming growth factor, we investigated the effect of 1,25-(OH)2D3 on EGF receptor levels in several human breast cancer cell lines. Preincubation of T-47D cells with 1,25-(OH)2D3 for 24 h resulted in a significant concentration-dependent decline in the specific binding of [125I]EGF. The effect was observed when EGF binding was assayed at either 0 or 37 degrees C, both before and after treatment with acid to remove receptor bound endogenous ligand. This indicated that the effect on [125I]-EGF binding was not due to effects of 1,25-(OH)2D3 on receptor internalization and degradation or receptor occupancy. The half-maximal inhibitory concentration of 1,25-(OH)2D3 was approximately 2 nM. The decrease in EGF binding was due to a decrease in receptor number from 2,900 sites/cell in control cultures to 2,330 and 1,730 sites/cell in cells treated for 24 h with 10(-8) and 10(-6) M 1,25-(OH)2D3, respectively. There was no change in the affinity of the receptor for EGF following treatment with 1,25-(OH)2D3 [Kd = 0.075 +/- 0.006 nM (+/- SEM) for control and Kd = 0.083 +/- 0.004 nM for treated cells]. Decreased EGF receptor levels were also achieved with a number of analogues of 1,25-(OH)2D3 in accordance with their affinities for the 1,25-(OH)2D3 receptor, i.e., potencies for decreasing EGF binding in T-47D cells were in the order: 1,25-(OH)2D3 greater than 1,24,25-trihydroxyvitamin D3 greater than 1,25,26-trihydroxyvitamin D3 greater than 24,25-dihydroxyvitamin D3 greater than or equal to 25-hydroxyvitamin D3. Specific, saturable EGF binding to MCF-7 cells was also reduced by 1,25-(OH)2D3 while binding to BT-20 and HBL-100 cells was unaffected by this treatment.(ABSTRACT TRUNCATED AT 400 WORDS)