The Journal of Steroid Biochemistry and Molecular Biology
Characterization of Vitamin D insensitive prostate cancer cells
Introduction
Prostate cancer (CaP) is one of the leading causes of cancer and cancer-related mortality in American men [1]. 1,25-Dihydroxyvitamin D3 (calcitriol) is currently being developed for CaP prevention and treatment because it exerts antitumor activities in CaP [2], [3], [4], [5], [6]. The mechanisms of action of calcitriol in CaP include induction of cell cycle arrest [7], apoptosis [8], [9] and differentiation [2], [10]; and inhibition of invasion [11] and metastasis [4]. Clinical trials have been conducted in men with CaP using calcitriol alone or in combination with other antitumor agents [12], [13], [14]. Calcitriol is inactivated and degraded by 24-hydroxylase (cyp24) [15], and previous studies indicate that the availability of calcitriol in CaP cells is inversely proportional to cyp24 activity [16].
Evidence of insensitivity to the antiproliferative effects of calcitriol has been described in some malignant cells. Following chronic exposure to calcitriol, MCF-7 human breast cancer cells become resistant to the growth inhibitory effects of calcitriol and other Vitamin D analogs [17], [18]. The Vitamin D resistant chronic myelogenous leukemia cell line, JMRD3, is less sensitive to growth inhibition by calcitriol compared to parental RWLeu-4 cells [19]. However the molecular mechanisms of Vitamin D insensitivity in CaP is poorly understood. These studies are a report on primary cell cultures established from the transgenic adenocarcinoma of mouse prostate (TRAMP) model that were used to study Vitamin D insensitivity in CaP. The TRAMP model was developed using the minimal rat probasin promoter to target expression of SV40 early genes (T, t) specifically to the prostatic epithelium [20]. These mice progressively develop disease in the prostate ranging from prostatic intraepithelial neoplasia (PIN) to poorly differentiated cancer and metastasis. Prostate tumors of calcitriol-treated (Vitamin D insensitive, VDI) and vehicle-treated (Vitamin D naïve, naïve) mice were digested to generate primary cell cultures. This is a report on the response of naïve and VDI primary cells to calcitriol.
Section snippets
Chemicals and reagents
Calcitriol and paricalcitol (Abbott Laboratories, Chicago, IL) were dissolved in 100% ethanol and stored at −80 °C. Calcitriol was always handled with indirect light. Test compounds were diluted in DMEM media (Invitrogen, Frederick, MD) before use.
Animal studies
Experimental uses of laboratory animals were in accordance with IACUC and NIH guidelines. TRAMP animals were in the C57BL/6 X FVB 50:50 strain background. Breeding colonies were maintained at the Roswell Park Cancer Institute animal facilities. Four
Antiproliferative effects of Vitamin D compounds in naïve and VDI cells
Compared to naïve cells, VDI cells were less sensitive to inhibition of cell growth following treatment with calcitriol for 96 h (Fig. 1A). Calcitriol (3.6 nM) inhibited growth of naïve cells by 30%; however, there was no effect on growth of VDI cells. To determine whether VDI cells are cross-resistant to other Vitamin D compounds, cells were treated for 96 h with the Vitamin D analog, paricalcitol. VDI cells were less responsive to growth inhibition by paricalcitol than naïve cells which were
Discussion
Vitamin D resistance has been observed in some cancers and may limit the efficacy of Vitamin D therapies in the clinic. Progression to advanced CaP is associated with insensitivity to Vitamin D. There is a need to understand the molecular mechanisms that underlie insensitivity to Vitamin D therapies in order to improve the clinical efficacy of Vitamin D compounds. Previous studies have indicated that MCF-7 breast cancer cells and RWLeu-4 leukemia cells become insensitive to the antitumor
References (20)
- et al.
Vitamin D inhibition of prostate adenocarcinoma growth and metastasis in the Dunning rat prostate model system
Urology
(1997) - et al.
Calcitriol (1,25-dihydroxycholecalciferol) potentiates activity of mitoxantrone/dexamethasone in an androgen independent prostate cancer model
J. Urol.
(2002) - et al.
Vitamin D receptor: a potential target for intervention
Urology
(2002) - et al.
Vitamin D metabolism
- et al.
Characterization of a vitamin D3-resistant human chronic myelogenous leukemia cell line
Blood
(1994) - Cancer.org ACS website, American Cancer...
- et al.
Vitamin D and prostate cancer: 1,25-dihydroxyvitamin D3 receptors and actions in human prostate cancer cell lines
Endocrinology
(1993) - et al.
Antiproliferative effects of 1,25-dihydroxyvitamin D3 on primary cultures of human prostatic cells
Cancer Res.
(1994) - et al.
Vitamin D receptor-dependent antitumour effects of 1,25-dihydroxyvitamin D3 and two synthetic analogues in three in vivo models of prostate cancer
BJU Int.
(2002) - et al.
Antiproliferative effect of 1alpha,25-dihydroxyvitamin D3 in human prostate cancer cell line LNCaP involves reduction of cyclin-dependent kinase 2 activity and persistent G1 accumulation
Endocrinology
(1998)
Cited by (9)
Vitamin D and cancer: Deciphering the truth
2011, Biochimica et Biophysica Acta - Reviews on CancerCitation Excerpt :The epithelial cells in PIA lesions exhibit many molecular signs of inflammation including increased expression of COX-2; moreover, dietary supplementation of COX-2 selective inhibitors (e.g., celecoxib) suppresses prostate carcinogenesis in the TRAMP model of prostate cancer [40]. The inhibitory effects of calcitriol on COX-2 expression and the prostaglandin pathway, production of pro-inflammatory cytokines, NFkB signaling, and tumor angiogenesis suggest that vitamin D has the potential to be useful as a chemopreventive agent in malignancies such as prostate cancer: according to this hypothesis, administration of high-dose calcitriol suppresses prostate tumor development in TRAMP mice [41]. Importantly, similar results have been reported in Nkx3.1; PTEN mutant mice, which reproduce the stages of prostate carcinogenesis from PIN lesions to adenocarcinoma [42].
CYP24A1 regulation in health and disease
2011, Vitamin D: Two-Volume SetCYP24A1 regulation in health and disease
2011, Vitamin D