Insulin-like growth factor binding protein-2 regulates β-catenin signaling pathway in glioma cells and contributes to poor patient prognosis

Shilpa S Patil; Priyanka Gokulnath; Mohsin Bashir; Shivayogi D Shwetha; Janhvi Jaiswal; Arun H Shastry; Arivazhagan Arimappamagan; Vani Santosh; Paturu Kondaiah

doi:10.1093/neuonc/now053

Insulin-like growth factor binding protein-2 regulates β-catenin signaling pathway in glioma cells and contributes to poor patient prognosis

Neuro Oncol. 2016 Nov;18(11):1487-1497. doi: 10.1093/neuonc/now053. Epub 2016 Apr 3.

Authors

Shilpa S Patil¹, Priyanka Gokulnath¹, Mohsin Bashir¹, Shivayogi D Shwetha¹, Janhvi Jaiswal¹, Arun H Shastry¹, Arivazhagan Arimappamagan¹, Vani Santosh¹, Paturu Kondaiah¹

Affiliation

¹ Molecular Reproduction, Development and Genetics department, Indian Institute of Science, Bangalore, India (S.S.P., P.G., M.B., P.K.); Department of Neuropathology, National Institute of Mental Health and Neuro Sciences, Bangalore, India (S.D.S., J.J., V.S.); Clinical Neurosciences, National Institute of Mental Health and Neuro Sciences, Bangalore, India (A.H.S.); Neurosurgery, National Institute of Mental Health and Neuro Sciences, Bangalore, India (A.A.).

Abstract

Background: Upregulation of insulin-like growth factor binding protein 2 (IGFBP-2) is often associated with aggressiveness of glioblastoma (GBM) and contributes to poor prognosis for GBM patients. In view of the regulation of β-catenin by IGFBP-2 in breast cancer and the crucial role of β-catenin pathway in glioma invasion, proliferation and maintenance of glioma stem cells, the mechanism of regulation of β-catenin by IGFBP-2, and its role in GBM prognosis was studied.

Methods: Regulation of the β-catenin pathway was studied by immunocytochemistry, Western blot analysis, luciferase assays, and real-time RT-PCR. The role of IGFBP-2 was studied by subcutaneous tumor xenografts in immunocompromised mice using glioma cells engineered to express IGFBP-2 and its domains. GBM patient tumor tissues (n = 112) were analyzed for expression of IGFBP-2 and β-catenin by immunohistochemistry. Survival analysis was performed employing Cox regression and Kaplan-Meier survival analyses.

Results: IGFBP-2 knockdown in U251, T98G, and U373 or overexpression in LN229 and U87 cells revealed a role for IGFBP-2 in stabilization of β-catenin and regulation of its nuclear functions involving integrin-mediated inactivation of GSK3β. Similar results were obtained upon overexpression of the C-terminal domain of IGFBP-2 but not the N-terminal domain. Subcutaneous xenograft tumors overexpressing either full-length or the C-terminal domain of IGFBP-2 showed larger volume as compared with controls. Coexpression of high levels of IGFBP-2 and β-catenin was associated with worse prognosis (P = .001) in GBM patients.

Conclusion: IGFBP-2 potentiates GBM tumor growth by the activation of the β-catenin pathway through its C-terminal domain, and their coexpression possibly contributes to worse patient prognosis.

Keywords: GBM prognosis; GSK3β; IGFBP-2 C-domain; β-catenin signaling.

MeSH terms

Animals
Brain Neoplasms / diagnosis
Brain Neoplasms / metabolism*
Cell Line, Tumor
Glioblastoma / diagnosis
Glioblastoma / metabolism*
Glycogen Synthase Kinase 3 beta / metabolism
Heterografts
Humans
Insulin-Like Growth Factor Binding Protein 2 / metabolism*
Integrins / metabolism
Mice
Mice, Nude
Prognosis
Receptor, IGF Type 1
Receptors, Somatomedin / metabolism
Signal Transduction
Survival Analysis
beta Catenin / metabolism*

Substances

IGF1R protein, human
Insulin-Like Growth Factor Binding Protein 2
Integrins
Receptors, Somatomedin
beta Catenin
Receptor, IGF Type 1
Glycogen Synthase Kinase 3 beta