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Anticancer activity of VDR-coregulator inhibitor PS121912. Cancer Chemother Pharmacol 2014 Oct;74(4):787-98

Date

08/12/2014

Pubmed ID

25107568

Pubmed Central ID

PMC4177010

DOI

10.1007/s00280-014-2549-y

Scopus ID

2-s2.0-84939871260   17 Citations

Abstract

PURPOSE: PS121912 has been developed as selective vitamin D receptor (VDR)-coregulator inhibitor starting from a high throughput screening campaign to identify new agents that modulate VDR without causing hypercalcemia. Initial antiproliferative effects of PS121912 were observed that are characterized herein to enable future in vivo investigation with this molecule.

METHODS: Antiproliferation and apoptosis were determined using four different cancer cell lines (DU145, Caco2, HL-60 and SKOV3) in the presence of PS121912, 1,25-(OH)₂D₃, or a combination of 1,25-(OH)₂D₃ and PS121912. VDR si-RNA was used to identify the role of VDR during this process. The application of ChIP enabled us to determine the involvement of coregulator recruitment during transcription, which was investigated by RT-PCR with VDR target genes and those affiliated with cell cycle progression. Translational changes of apoptotic proteins were determined with an antibody array. The preclinical characterization of PS121912 includes the determination of metabolic stability and CYP3A4 inhibition.

RESULTS: PS121912 induced apoptosis in all four cancer cells, with HL-60 cells being the most sensitive. At sub-micromolar concentrations, PS121912 amplified the growth inhibition of cancer cells caused by 1,25-(OH)₂D₃ without being antiproliferative by itself. A knockout study with VDR si-RNA confirmed the mediating role of VDR. VDR target genes induced by 1,25-(OH)₂D₃ were down-regulated with the co-treatment of PS121912. This process was highly dependent on the recruitment of coregulators that in case of CYP24A1 was SRC2. The combination of PS121912 and 1,25-(OH)₂D₃ reduced the presence of SRC2 and enriched the occupancy of corepressor NCoR at the promoter site. E2F transcription factors 1 and 4 were down-regulated in the presence of PS121912 and 1,25-(OH)₂D₃ that in turn reduced the transcription levels of cyclin A and D, thus arresting HL-60 cells in the S or G2/M phase. In addition, proteins with hematopoietic functions such as cyclin-dependent kinase 6, histone deacetylase 9 and transforming growth factor beta 2 and 3 were down-regulated as well. Elevated levels of P21 and GADD45, in concert with cyclin D1, also mediated the antiproliferative response of HL-60 in the presence of 1,25-(OH)₂D₃ and PS121912. Studies at higher concentration of P121912 identified a VDR-independent pathway of antiproliferation that included the enzymatic and transcriptional activation of caspase 3/7.

CONCLUSION: Overall, we conclude that PS121912 behaves like a VDR antagonist at low concentrations but interacts with more targets at higher concentrations leading to apoptosis mediated by caspase 3/7 activation. In addition, PS121912 showed an acceptable metabolic stability to enable in vivo cancer studies.

Author List

Sidhu PS, Teske K, Feleke B, Yuan NY, Guthrie ML, Fernstrum GB, Vyas ND, Han L, Preston J, Bogart JW, Silvaggi NR, Cook JM, Singh RK, Bikle DD, Arnold LA

Authors

Alexander (Leggy) Arnold PhD Professor in the Chemistry & Biochemistry department at University of Wisconsin - Milwaukee
James M. Cook PhD University Distinguished Professor in the Chemistry and Biochemistry department at University of Wisconsin - Milwaukee
Nicholas R. Silvaggi PhD Assistant Professor in the Chemistry and Biochemistry department at University of Wisconsin - Milwaukee




MESH terms used to index this publication - Major topics in bold

Antimetabolites, Antineoplastic
Apoptosis
Apoptosis Regulatory Proteins
Caco-2 Cells
Caspases, Effector
Cell Proliferation
Cytochrome P-450 CYP3A
Dose-Response Relationship, Drug
Drug Screening Assays, Antitumor
Enzyme Activation
HL-60 Cells
Humans
Receptors, Calcitriol
Transcriptional Activation
Tumor Cells, Cultured