title: Insulin like growth factor binding protein 4 promotes GBM progression and regulates key factors involved in EMT and invasion.
abstract: Insulin like growth factor binding protein 4 (IGFBP4) regulates growth and development of tissues and organs by negatively regulating IGF signaling. Among most cancers, IGFBP4 has growth inhibitory role and reported as a down-regulated gene, except for renal cell carcinoma, wherein IGFBP4 promotes tumor progression. IGFBP4 expression has been shown to be higher in increasing grades of astrocytoma. However, the functional role of IGFBP4 in gliomas has not been explored. Surgical biopsies of 20 normal brain and 198 astrocytoma samples were analyzed for IGFBP4 expression by qRT-PCR. Highest expression of IGFBP4 mRNA was seen in GBM tumors compared to control brain tissues (median log2 of 2.035, p < 0.0001). Immunohistochemical analysis of 53 tissue samples revealed predominant nuclear staining of IGFBP4, seen maximally in GBMs when compared to DA and AA tumors (median LI = 29.12 ± 16.943, p < 0.001). Over expression of IGFBP4 in U343 glioma cells resulted in up-regulation of molecules involved in tumor growth, EMT and invasion such as pAkt, pErk, Vimentin, and N-cadherin and down-regulation of E-cadherin. Functionally, IGFBP4 over expression in these cells resulted in increased proliferation, migration and invasion as assessed by MTT, transwell migration, and Matrigel invasion assays. These findings were confirmed upon IGFBP4 knockdown in U251 glioma cells. Our data suggest a pro-tumorigenic role for IGFBP4 in glioma.
authors.affiliation: Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, 560 012, India.
authors.forename: V R
authors.initials: VR
authors.lastname: Praveen Kumar
authors.forename: Priyanka
authors.initials: P
authors.lastname: Sehgal
authors.forename: Balram
authors.initials: B
authors.lastname: Thota
authors.forename: Shilpa
authors.initials: S
authors.lastname: Patil
authors.forename: Vani
authors.initials: V
authors.lastname: Santosh
authors.forename: Paturu
authors.initials: P
authors.lastname: Kondaiah
mesh_terms: D000818:Animals; D001254:Astrocytoma / Q000473:pathology; D001932:Brain Neoplasms / Q000378:metabolism* / Q000473:pathology*; D015820:Cadherins / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D049109:Cell Proliferation; D018450:Disease Progression; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology; D005909:Glioblastoma / Q000473:pathology*; D006801:Humans; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D051058:Oncogene Protein v-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D018709:Statistics, Nonparametric; D014746:Vimentin / Q000378:metabolism
chemical_list: D015820:Cadherins; D018974:Insulin-Like Growth Factor Binding Protein 4; D034741:RNA, Small Interfering; D014746:Vimentin; D051058:Oncogene Protein v-akt