Castration-induced apoptosis of androgen-dependent shionogi carcinoma is associated with increased expression of genes encoding insulin-like growth factor-binding proteins.
Insulin-like growth factor (IGF)-I has well-characterized mitogenic and antiapoptotic effects that are essential for maintenance of the normal prostate and may be important during regression of the normal prostate and/or prostate tumors induced by androgen-targeting therapies for prostate cancer. IGF-I activity is modulated by IGF-binding proteins (IGFBPs). Here we examine IGFBP expression during regression of androgen-dependent Shionogi carcinoma tumors after castration. In this model, we observe a 90% reduction in Shionogi tumors by 10 days postcastration. Northern blotting of RNA from tumors collected at various times after castration indicates a rapid induction of IGFBP-5 concomitant with apoptotic regression of tumors, as detected by Apoptag staining of tumor sections after castration. IGFBP-5 mRNA was not detectable in tumors from control animals, but levels increased 120-fold in tumors 3 days after castration. The mRNAs for IGFBP-3 and 4 were abundant in Shionogi tumors from intact mice and decreased to -33% and -20% of control, respectively. Castration had no significant effect on IGFBP-2 expression. Treatment with calcium channel blockers inhibited castration-induced apoptosis and tumor regression and also significantly inhibited up-regulation of IGFBP-5 after castration. These data provide strong evidence for a functional role of IGFBP-5 expression in mediating the apoptosis induced by androgen deprivation in androgen-dependent neoplasia.
Lady Davis Research Institute of the Sir Mortimer B. Davis Jewish General Hospital and Department of Oncology, McGill University, Montreal, Quebec, Canada.
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Nickerson
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Miyake
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Gleave
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Pollak
D017311:Amlodipine / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D002277:Carcinoma / Q000235:genetics / Q000473:pathology / Q000601:surgery*; D015972:Gene Expression Regulation, Neoplastic; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000096:biosynthesis* / Q000235:genetics; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D009376:Neoplasms, Hormone-Dependent / Q000235:genetics / Q000473:pathology / Q000601:surgery*; D009543:Nifedipine / Q000494:pharmacology; D009919:Orchiectomy; D011471:Prostatic Neoplasms / Q000235:genetics / Q000473:pathology / Q000601:surgery*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012334:RNA, Neoplasm / Q000096:biosynthesis / Q000235:genetics; D013739:Testosterone / Q000502:physiology*
D002121:Calcium Channel Blockers; D018971:Insulin-Like Growth Factor Binding Protein 2; D018975:Insulin-Like Growth Factor Binding Protein 5; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D017311:Amlodipine; D013739:Testosterone; D009543:Nifedipine