Novel 19-nor-hexafluoride vitamin D3 analog (Ro 25-6760) inhibits human colon cancer in vitro via apoptosis.
Our previously performed experiments clearly showed a significant VDR-mediated growth inhibitory effect of 1,25-dihydroxyvitamin D3 and its synthetic analogs in a variety of human cancer cells including human colon and breast cancer, soft tissue sarcoma, and malignant melanoma cell lines. The mechanisms by which 1, 25-dihydroxyvitamin D3 and its synthetic analogs growth inhibit human cancer cells is poorly elucidated. The exposure of human colon cancer cells HT-29 to 1,25-dihydroxyvitamin D3 or its analog, 1alpha, 25-dihydroxy-16-ene-23yne-26,27-hexafluoro-19-nor-choleca lci ferol (Ro 25-6760), at the 10(-6) M concentration resulted in significant growth inhibition with induction of the apoptotic process after three days of treatment detected by TUNEL assay and agarose gel electrophoresis of DNA. As a logical link with DNA fragmentation analyses and TUNEL assay, cleavage of the 116 kDa PARP protein was accompanied by the appearance of a characteristic 85 kDa fragment of PARP in a population of floating cells after both treatments. The results of cell cycle analysis showed a G0/G1 phase block after three days of administration of either compound when compared with untreated cells. On day 4, G0/G1 cell cycle arrest remained on the same level in comparison with control. Paralleling the G0/G1 phase block, was a notable decrease in the number of cells in the S phase which also became significant after three days of treatment. The results of these experiments show that the newly developed 19-nor synthetic vitamin D3 analog, Ro 25-6760, as well as 1, 25-dihydroxyvitamin D3, induced the expression of p21waf1, resulted in a significant G1/G0 cell cycle arrest leading to impressive growth inhibition and induction of apoptosis associated with proteolytic cleavage of poly(ADP-ribose) polymerase (PARP) showing a possible involvement of apoptosis-specific activation of the ICE/CED-3 proteolitic pathway.
Evans
S R
SR
Department of Surgery, George Washington University, Washington, DC 20037, USA.
Soldatenkov
V
V
Shchepotin
E B
EB
Bogrash
E
E
Shchepotin
I B
IB
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D002117:Calcitriol / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002762:Cholecalciferol / Q000031:analogs & derivatives* / Q000494:pharmacology; D003110:Colonic Neoplasms / Q000473:pathology*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects; D019073:HT29 Cells; D006801:Humans; D010447:Peptide Hydrolases / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D016192:Resting Phase, Cell Cycle / Q000187:drug effects; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; C113532:Ro 25-6760; D002762:Cholecalciferol; D011065:Poly(ADP-ribose) Polymerases; D010447:Peptide Hydrolases; D002117:Calcitriol