Combination therapy of insulin-like growth factor binding protein-3 and retinoid X receptor ligands synergize on prostate cancer cell apoptosis in vitro and in vivo.
We have previously identified the retinoid X receptor-alpha (RXRalpha) as an insulin-like growth factor binding protein-3 (IGFBP-3) nuclear binding partner, which is required for IGFBP-3-induced apoptosis. In the current study, we investigated the biological interactions of the RXR ligand, VTP194204 and rhIGFBP-3, in vitro and in vivo. In vitro, IGFBP-3 and VTP194204 individually induced apoptosis, and suppressed cell growth in prostate cancer cell lines in an additive manner. In vivo, LAPC-4 xenograft-bearing severe combined immunodeficiency mice treated daily with saline, IGFBP-3, and/or VTP194204 for 3 weeks showed no effect of individual treatments with IGFBP-3 or VTP194204 on tumor growth. However, the combination of IGFBP-3 and VTP194204 treatments inhibited tumor growth by 50% and induced a significant reduction in serum prostate-specific antigen levels. In terminal nucleotidyl transferase-mediated nick end labeling immunohistochemistry of LAPC-4 xenografts, there was modest induction of apoptosis with either IGFBP-3 or VTP194204 individual treatment, but combination therapy resulted in massive cell death, indicating that IGFBP-3 and VTP194204 have a synergistic effect in preventing tumor growth by apoptosis induction. In summary, this is an initial description of the successful therapeutic use of IGFBP-3 as a cancer therapy in vivo, and shows that combination treatment of IGFBP-3 and RXR ligand has a synergistic effect on apoptosis induction leading to substantial inhibition of prostate cancer xenograft growth. Taken together, these observations suggest that combination therapy with IGFBP-3 and RXR ligands may have therapeutic potential for prostate cancer treatment.
Division of Pediatric Endocrinology, Mattel Children's Hospital at UCLA, California, USA.
Bingrong
B
Liu
Kuk-Wha
KW
Lee
Heju
H
Li
Liqun
L
Ma
George L
GL
Lin
Roshantha A S
RA
Chandraratna
Pinchas
P
Cohen
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D004357:Drug Synergism; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000008:administration & dosage / Q000494:pharmacology*; D008024:Ligands; D008297:Male; D051379:Mice; D016513:Mice, SCID; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000188:drug therapy* / Q000473:pathology; D047488:Retinoid X Receptors / Q000378:metabolism; D012176:Retinoids / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D013997:Time Factors; D023041:Xenograft Model Antitumor Assays
D018972:Insulin-Like Growth Factor Binding Protein 3; D008024:Ligands; D047488:Retinoid X Receptors; D012176:Retinoids; D017430:Prostate-Specific Antigen