ABSTRACT
The antitumor effects of 1,25-dihydroxyvitamin D(3) (calcitriol) are being exploited for prevention and treatment of prostate cancer (CaP). These studies examined the antiproliferative effects of calcitriol in primary cell cultures derived from transgenic adenocarcinoma of mouse prostate (TRAMP) mice chronically treated with calcitriol (20 microg/kg) or vehicle 3x/week from 4 weeks-of-age until palpable tumors developed. This is a report on the response of two representative control (Vitamin D naïve, naïve) and calcitriol-treated (Vitamin D insensitive, VDI) cells to calcitriol. VDI cells were less sensitive to calcitriol based on less cell growth inhibition and less inhibition of DNA synthesis as measured by MTT and BrdU incorporation assays. Similarly, VDI cells were less sensitive to growth inhibition by the vitamin analog, 19-nor-1alpha,25-dihydroxyvitamin D(2) (paricalcitol). There was no change in apoptosis following treatment of naïve and VDI cells with calcitriol. Vitamin D receptor (VDR) expression was up-regulated by calcitriol in both naïve and VDI cells. In addition, calcitriol induced the Vitamin D metabolizing enzyme, 24-hydroxylase (cyp24) mRNA and enzyme activity similarly in naïve and VDI cells as measured by RT-PCR and HPLC, respectively. In summary, VDI cells are less responsive to the antiproliferative effects of calcitriol. Understanding Vitamin D insensitivity will further clinical development of Vitamin D compounds for prevention and treatment of CaP.
Subject(s)
Drug Resistance, Neoplasm , Prostatic Neoplasms/metabolism , Prostatic Neoplasms/pathology , Vitamin D/metabolism , Animals , Cell Proliferation/drug effects , Cells, Cultured , Gene Expression Regulation/drug effects , Male , Mice , RNA, Messenger/genetics , Receptors, Calcitriol/metabolism , Steroid Hydroxylases/genetics , Steroid Hydroxylases/metabolism , Vitamin D/analogs & derivatives , Vitamin D/pharmacology , Vitamin D3 24-HydroxylaseABSTRACT
The mechanisms of action of three C-10 non-acetal trioxane dimers (TDs) were examined in human (LNCaP) and mouse (TRAMP-C1A and -C2H) prostate cancer cell lines. 1 (AJM3/23), 2 (GHP-TM-III-07w), and 3 (GHP-KB-06) inhibited cell growth with 3 being the most potent in C1A (GI50 = 18.0 nM), C2H (GI50 = 17.0 nM), and LNCaP (GI50 = 17.9 nM) cells. In comparison to a standard cytotoxic agent such as doxorubicin (GI50 = 45.3 nM), 3 (GI50 = 17.9 nM) inhibited LNCaP cell growth more potently. TDs induced G0/G1 cell cycle arrest in LNCaP cells and decreased cells in the S phase. These changes correlated with modulation of G1 phase cell cycle proteins including decreased cyclin D1, cyclin E, and cdk2 and increased p21waf1 and p27Kip1. TDs also promoted apoptosis in LNCaP cells with increased expression of proapoptotic bax. These results demonstrate that TDs are potentially useful agents that warrant further preclinical development for treatment of prostate cancer.
Subject(s)
Acetals/pharmacology , Antineoplastic Agents/pharmacology , Artemisinins/pharmacology , Heterocyclic Compounds/pharmacology , Prostatic Neoplasms/pathology , Acetals/chemical synthesis , Acetals/chemistry , Animals , Antibiotics, Antineoplastic/pharmacology , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Apoptosis/drug effects , Artemisinins/chemical synthesis , Artemisinins/chemistry , Cell Cycle/drug effects , Cell Cycle Proteins/metabolism , Dimerization , Doxorubicin/pharmacology , Heterocyclic Compounds/chemical synthesis , Heterocyclic Compounds/chemistry , Humans , Male , Mice , Prostatic Neoplasms/metabolism , Tumor Cells, Cultured/drug effectsABSTRACT
The active metabolite of vitamin D(3) (1alpha,25-dihydroxyvitamin D(3), calcitriol) has potent antitumor activities in vitro and in vivo in multiple cancers. Concerns about induction of hypercalcemia by calcitriol and the desire for more potent agents have prompted development of less-calcemic vitamin D analogs. These studies demonstrate that two vitamin D analogs, 19-nor-1alpha,25-dihydroxyvitamin D(2) (paricalcitol) and 1alpha-hydroxymethyl-16-ene-24,24-difluoro-25-hydroxy-26,27-bis-homovitamin D(3) (QW-1624F(2)-2, QW), have anticancer effects in the calcitriol-responsive squamous cell carcinoma (SCC) cell line. Paricalcitol (GI50 = 0.7 nM) and QW (GI50 = 0.001 nM) inhibited SCC cell growth; however, QW was more potent. Paricalcitol (10 nM) and QW (10 nM) induced G0/G1 cell cycle arrest and inhibited DNA synthesis by approximately 95%. The vitamin D analogs modulated cell cycle regulators, including decreasing mRNA and protein levels of p21(Waf1/Cip1) (p21) and cyclin-dependent kinase 2 (cdk2), and increasing p27(Kip1) (p27) protein expression. Vitamin D analogs induced apoptosis, caspase-3 cleavage and increased expression of pro-apoptotic MEKK-1. Phosphorylation of Akt, MEK and ERK1/2 that promote cell growth and survival were inhibited by vitamin D analogs. The anticancer effects of paricalcitol and QW are comparable to the effect of calcitriol. These less-calcemic vitamin D analogs are as effective as calcitriol in vitro and are promising for prevention and treatment of cancer and other diseases.
