PTEN-induction in U251 glioma cells decreases the expression of insulin-like growth factor binding protein-2
- Lady Davis Institute for Medical Research, Jewish General Hospital, Department of Medicine, Division of Experimental Medicine, McGill University, Montreal, Que., H3T 1E2 (Canada)
- M.D. Anderson Cancer Center, Department of Neuro-Oncology and Molecular Genetics, Houston, TX 77030-4095 (United States)
- Department of Medicine and Oncology, McGill University, Montreal, Que., H3T 1E2 (Canada)
PTEN is a tumor suppressor gene whose loss of function is observed in {approx}40-50% of human cancers. Although insulin-like growth factor binding protein-2 (IGFBP-2) was classically described as a growth inhibitor, multiple recent reports have shown an association of overexpression and/or high serum levels of IGFBP-2 with poor prognosis of several malignancies, including gliomas. Using an inducible PTEN expression system in the PTEN-null glioma cell line U251, we demonstrate that PTEN-induction is associated with reduced proliferation, increased apoptosis, and a substantial reduction of the high levels of IGFBP-2 expression. The PTEN-induced decrease in IGFBP-2 expression could be mimicked with the PI3-kinase inhibitor LY294002, indicating that the lipid phosphatase activity of PTEN is responsible for the observed effect. However, the rapamycin analog CCI-779 did not affect IGFBP-2 expression, suggesting that the PTEN-induced decrease in IGFBP-2 expression is not attributable to decreased mTOR signalling. Recombinant human IGFBP-2 was unable to rescue U251-PTEN cells from the antiproliferative effects of PTEN, and IGFBP-2 siRNA did not affect the IGF-dependent or -independent growth of this cell line. These results suggest that the clinical data linking IGFBP-2 expression to poor prognosis may arise, at least in part, because high levels of IGFBP-2 expression correlate with loss of function of PTEN, which is well known to lead to aggressive behavior of gliomas. Our results motivate translational research regarding the relationship between IGFBP-2 expression and loss of function of PTEN.
- OSTI ID:
- 20713413
- Journal Information:
- Biochemical and Biophysical Research Communications, Vol. 336, Issue 4; Other Information: DOI: 10.1016/j.bbrc.2005.08.229; PII: S0006-291X(05)01842-5; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0006-291X
- Country of Publication:
- United States
- Language:
- English
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