Quantitative proteomic analysis reveals a molecular triad signature as biomarker candidates for astrocytomas and oligodendrogliomas

摘要

We were able to identify 1095 iTRAQ labeled proteins and 268 presented altered expression level in at least one group. Some that proteins presented correlation with increase tumor malignancy. We found that expression of nucleophosmin (NPM, 2-3 folds) and GRP78 (2 folds) were increased and Raf kinase inhibitor protein or Phosphatidylethanolamine-binding protein 1 (RKIP or PEBP1, 2 folds) decreased in glioblastoma multiforme (GBM) and oligodendroglioma grade II and III. The expression data of these three proteins were validated in a larger number of tumors by qRT-PCR, western blotting and immunohistochemistry (data not shown). NPM is a phosphoprotein related to apoptosis, ribosome biogenesis, mitosis, and DNA repair. RKIP is a metastasis suppressor. NPM and RKIP are involved in two signal transduction cascades known to contribute to the formation of glioma, i.e. RAS/RAF/MAPK and PI3K/AKT/mTOR. GRP78 is an endoplasmic reticulum chaperone molecule that plays a key role in cell survival. It is a potent anti-apoptotic protein and plays a critical role in tumor cell survival, tumor progression, angiogenesis, metastasis and resistance to therapy. We also showed that silencing of NPM promoted a decreased expression of proteins involved in regulation of apoptosis, including GRP78. NPM proved to participate in the apoptotic process, sensitizing temolozamidetreated U87MG and A172 cells to cell death. In a large data set of GBM patients, both GRP78 and NPM1 genes were up-regulated and presented a tendency to shorter overall survival time. We also observed that the GRP78 expression at the mRNA and protein level showed a scattered pattern in grade IV astrocytoma, as opposed to a grouped pattern in grade I astrocytoma and in non-neoplastic tissue. These results suggest an important participation of the molecular triad in the already well-known heterogeneity of glioma which perhaps could be useful as prognostic factor and may represent important biomarkers of tumor progression. (supported by FAPESP, CNPq, FINEP)