title: Activation of various downstream signaling molecules by IGFBP-3.
abstract: Insulin-like growth factor binding protein-3 (IGFBP-3), a secretory protein, is the most abundant IGF binding protein present in human serum among all IGF binding proteins. IGFBP-3 shows decreased level of expression in cancerous cells but has been known to be present in significant amounts in normal or non-cancerous cells. IGFBP-3 can induce apoptosis in prostate cancer cells either in an IGF-dependent manner or independently of IGF binding. Although putative cell death specific Insulin-like growth factor binding protein-3 (IGFBP-3R) receptor(s) has recently been identified by which IGFBP-3 may induce its anti-tumor effects, IGFBP-3 has also been known to activate various downstream intracellular signaling molecules via a different mechanistic pathway. Stat-1 has been known to be one of the candidate molecules activated by IGFBP-3. IGFBP-3 can also inhibit Akt/IGF-1 survival pathway in MCF- 7 breast cancer cells which ultimately leads to the induction of apoptosis in these cells. All these studies clearly demonstrate that IGFBP-3 regulates cell proliferation and promotes its pro-apoptotic effects in cancer cells in two different pathways,1) sequester IGF-I to bind to IGF-I receptor to inhibit cell proliferation and induce apoptosis, 2) independent of IGF-I pathway, IGFBP-3 binds to some putative receptor and activate various downstream pro-apoptotic molecules involved in cell death.
authors.affiliation: Diabetes Branch, NIDDK, National Institutes of Health, Bldg 10-Room 8D12, 9000 Rockville Pike, MSC 1758, Bethesda, MD 20892, United States.
authors.forename: Hanief Mohammad
authors.initials: HM
authors.lastname: Shahjee
authors.affiliation: Diabetes Branch, NIDDK, National Institutes of Health, Bldg 10-Room 8D12, 9000 Rockville Pike, MSC 1758, Bethesda, MD 20892, United States.
authors.forename: Nisan
authors.initials: N
authors.lastname: Bhattacharyya
keywords: Apoptosis; IGF-I; IGFBP-3; Stat-1; TGF-β