Responsiveness of human carcinoma cells of gynecologic origin to 1,25-dihydroxycholecalciferol

25-Hydroxycholecalciferol Inhibits Cell Growth and Induces Apoptosis in SiHa Cervical Cells via Autocrine Vitamin D Metabolism

Preclinical studies show that the anticancer actions of vitamin D metabolites are mediated by apoptosis, inhibition of cell proliferation and induction of cell cycle arrest. Cervical cancer cells express an autocrine vitamin D metabolising system (VDMS) comprised of a vitamin D receptor, vitamin D catabolic enzyme (CYP24A1), and the activating enzyme of 25-hydroxycholecalciferol (25(OH)D3), CYP27B1. We assessed the anticancer effects of 25(OH)D3 at clinically relevant concentrations on a cervical squamous cell cancer cell line, SiHa. We evaluated cell health parameters (cell count, viability, and cell cycle), cell death modes (apoptosis, autophagic-dependent death, and necrosis by flow cytometry and transmission electron microscopy), and autocrine VDMS gene and protein expression by qPCR and Western blot, respectively. Our study demonstrates that physiological and supraphysiological doses of 25(OH)D3 inhibit cell growth and viability and induce biochemical and morphological apoptosis in SiHa cells. These growth effects are mediated by alteration in the VDMS gene and protein expression, with prominent negative feedback at supraphysiological treatment dose. These data identify promising therapeutic potential of 25(OH)D3 in cervical cancer, which warrants further clinical translational investigations.

Vitamin D and Endometrium: A Systematic Review of a Neglected Area of Research

Growing evidence supports a role of vitamin D (VD) in reproductive health. Vitamin D receptor (VDR) is expressed in the ovary, endometrium, and myometrium. The biological actions of VD in fertility and reproductive tissues have been investigated but mainly using animal models. Conversely, the molecular data addressing the mechanisms underlying VD action in the physiologic endometrium and in endometrial pathologies are still scant. Levels of VDR expression according to the menstrual cycle are yet to be definitively clarified, possibly being lower in the proliferative compared to the secretory phase and in mid-secretory compared to early secretory phase. Endometrial tissue also expresses the enzymes involved in the metabolism of VD. The potential anti-proliferative and anti-inflammatory effects of VD for the treatment of endometriosis have been investigated in recent years. Treatment of ectopic endometrial cells with 1,25(OH)₂D₃ could significantly reduce cytokine-mediated inflammatory responses. An alteration of VD metabolism in terms of increased 24-hydroxylase mRNA and protein expression has been demonstrated in endometrial cancer, albeit not consistently. The effect of the active form of the vitamin as an anti-proliferative, pro-apoptotic, anti-inflammatory, and differentiation-inducing agent has been demonstrated in various endometrial cancer cell lines.

Role of 24-hydroxylase in vitamin D3growth response of OVCAR-3 ovarian cancer cells

Vitamin D and its analogues are potent regulators of cell growth and differentiation both in vivo and in vitro. We studied the effects of 25-hydroxyvitamin D(3) [25(OH)D(3)], 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] and vitamin D analogue, EB 1089, on the growth of a human ovarian cancer cell line, OVCAR-3. We also studied the expression of vitamin D metabolising enzymes 24-hydroxylase (24OHase) and 1alpha-hydroxylase (1alphaOHase). Our results showed that high concentrations (10 and 100 nM) of 1,25(OH)(2)D(3) inhibited a cell proliferation, whereas low concentration (0.1 nM) stimulated growth of the OVCAR-3 cells. In the concentration range of 10-500 nM a prohormone, 25(OH)D(3), stimulated growth. An amount of 1 nM EB 1089 and 100 nM 1,25(OH)(2)D(3) inhibited growth with an equal magnitude. The expression of 24OHase was strongly induced by 1,25(OH)(2)D(3) and EB 1089 in OVCAR-3 cells, and analysis of vitamin D metabolites showed the functionality of 24OHase. An inhibition of 24OHase activity with a novel 24OHase inhibitor enhanced growth-inhibiting effects of 1,25(OH)(2)D(3) and suppressed the growth stimulation of 100 nM 25(OH)D(3). We also report the expression of a vitamin D activating enzyme, 1alphaOHase, in 7 ovarian cancer cell lines. The production of 1,25(OH)(2)D(3) in OVCAR-3 cells was low, possibly due to an extensive activity of 24OHase or a low 1alphaOHase activity. These results suggest that in ovarian cancer cells vitamin D metabolizing enzymes might play a key role in modulating the growth response to vitamin D. The possible mitogenic effects of vitamin D should be considered when evaluating treatment of ovarian cancer with vitamin D.

Vitamin D receptor in endometrial carcinoma and the differentiation-inducing effect of 1,25-dihydroxyvitamin D3 on endometrial carcinoma cell lines

In view of the potential of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] as a cell-differentiation-inducing agent in endometrial cancer, the localization of the vitamin D receptor (VDR) was examined immunohistochemically in 21 endometrial adenocarcinoma specimens, and the effect of 1,25(OH)2D3 on cell growth, as well as the phenotypic changes for cell maturation after treatment with 1,25(OH)2D3, was investigated in 2 endometrial carcinoma cell lines (AMEC-1, RL95-2). The VDR was detected in 14 of the 21 endometrial carcinoma specimens. The growth of RL95-2 cells expressing VDR was inhibited to 44% when cultured with 50 nM 1,25(OH)2D3 for 6 days. In contrast, the growth of AMEC-1 cells not expressing VDR was completely uninhibited even when cultured with 100 nM 1,25(OH)2D3 for 6 days. The RL95-2 cells exposed to 50 nM 1,25(OH)2D3 for 6 days had an increasing expression for 52.5 kD or 45 kD cytokeratin polypeptide, and they became columnar with pronounced polarity and formed gland-like structures when cultured in collagen gel. These results suggest that endometrial adenocarcinoma is a target for 1,25(OH)2D3, which appears to function as a cell-differentiation-inducing agent for the treatment of endometrial cancer.

Receptors for 1,25-dihydroxyvitamin D3 in gynecologic neoplasms

To determine if gynecologic malignancies are candidates for 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) therapy we measured vitamin D receptor (VDR) levels in 11 tumor specimens using a radiolabeled ligand-binding assay. VDR was demonstrated in 3 of 6 ovarian tumors and 1 of 1 uterine sarcomas, but not in endometrial tumors (2), cervical tumors (1), or Krukenberg tumors (1). Scatchard plots revealed that [3H]1,25(OH)2D3 was bound to a single class of high-affinity (Kd = 0.3 to 0.6 nM), saturable sites characteristic of authentic 1,25(OH)2D3 receptors. Specificity of binding activity for 1,25(OH)2D3, the active vitamin D3 metabolite, was demonstrated by failure of 25-hydroxy- and 24,25-dihydroxyvitamin D3 to compete effectively against 1,25(OH)2D3 binding in total cellular tumor extracts. The ovarian carcinoma cell line NIH:OVCAR3 was shown to possess VDR (binding capacity = 137 fmol/mg protein, Kd = 0.48 nM). A 3-day incubation of NIH:OVCAR3 cells with 100 nM 1,25(OH)2D3 resulted in 49% inhibition of cell growth. The growth inhibition of an ovarian carcinoma line and the observation that 36% of gynecologic tumors assayed were shown to be VDR-positive suggest that further study is warranted to delineate the mechanism and possible therapeutic aspects of 1,25(OH)2D3 action in gynecologic tumors.