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Pathway alterations during glioma progression revealed by reverse phase protein lysate arrays
Rongcai Jiang1, Cristian Mircean, Ilya Shmulevich
1Department of Pathology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
Abstract:
The progression of gliomas has been extensively studied at the genomic level using cDNA microarrays. However, systematic examinations at the protein translational and post-translational levels are far more limited. We constructed a glioma protein lysate array from 82 different primary glioma tissues, and surveyed the expression and phosphorylation of 46 different proteins involved in signaling pathways of cell proliferation, cell survival, apoptosis, angiogenesis, and cell invasion. An analysis algorithm was employed to robustly estimate the protein expressions in these samples. When ranked by their discriminating power to separate 37 glioblastomas (high-grade gliomas) from 45 lower-grade gliomas, the following 12 proteins were identified as the most powerful discriminators: IBalpha, EGFRpTyr845, AKTpThr308, phosphatidylinositol 3-kinase (PI3K), BadpSer136, insulin-like growth factor binding protein (IGFBP) 2, IGFBP5, matrix metalloproteinase 9 (MMP9), vascular endothelial growth factor (VEGF), phosphorylated retinoblastoma protein (pRB), Bcl-2, and c-Abl. Clustering analysis showed a close link between PI3K and AKTpThr308, IGFBP5 and IGFBP2, and IBalpha and EGFRpTyr845. Another cluster includes MMP9, Bcl-2, VEGF, and pRB. These clustering patterns may suggest functional relationships, which warrant further investigation. The marked association of phosphorylation of AKT at Thr308, but not Ser473, with glioblastoma suggests a specific event of PI3K pathway activation in glioma progression.
Insights
This study analyzed protein expression in 82 gliomas, identifying 12 key proteins that distinguish high-grade glioblastomas from lower-grade gliomas, revealing specific PI3K pathway activation in progression.
Area of Science:
- Neuro-oncology
- Proteomics
- Cancer signaling pathways
Background:
- Glioma progression is well-studied at the genomic level, but protein expression and post-translational modifications remain less understood.
- Systematic analysis of protein translational and post-translational levels in gliomas is limited, hindering a comprehensive understanding of disease progression.
Purpose of the Study:
- To investigate protein expression and phosphorylation patterns in primary glioma tissues.
- To identify key proteins and signaling pathways involved in differentiating high-grade glioblastomas from lower-grade gliomas.
- To explore potential functional relationships between identified proteins through clustering analysis.
Main Methods:
- Construction of a glioma protein lysate array using 82 primary glioma tissues.
- Surveyed expression and phosphorylation of 46 proteins across key cancer signaling pathways.
- Employed an analysis algorithm for robust protein expression estimation and identified discriminating proteins using statistical ranking.
Main Results:
- Identified 12 proteins with high discriminating power between glioblastomas and lower-grade gliomas, including IBalpha, EGFRpTyr845, AKTpThr308, PI3K, BadpSer136, IGFBP2, IGFBP5, MMP9, VEGF, pRB, Bcl-2, and c-Abl.
- Clustering analysis revealed associations between PI3K and AKTpThr308, IGFBP5 and IGFBP2, and IBalpha and EGFRpTyr845.
- Observed a strong link between AKT phosphorylation at Thr308 (not Ser473) and glioblastoma, suggesting specific PI3K pathway activation.
Conclusions:
- Protein expression and phosphorylation profiling provide valuable insights into glioma progression beyond genomic analysis.
- Specific protein signatures, particularly involving PI3K pathway components, can effectively differentiate glioma grades.
- Further investigation into the functional relationships of identified protein clusters may uncover novel therapeutic targets for glioma.
