Platelet-derived growth factor expression correlates with tumor grade and proliferative activity in human oligodendrogliomas.

Background: For the last one and a half decade, it has been found that platelet-derived growth factor (PDGF) promotes glial tumor growth through autocrine and paracrine loops, by expression of PDGFalpha receptor (PDGFRalpha) on glioma cells and PDGFbeta receptor (PDGFRbeta) on proliferating endothelial cells. However, studies on oligodendrogliomas, correlating expression of PDGF and its receptor with tumor grade and proliferative activity, through MIB-1 labeling index (LI) are relatively few as compared to astroglial counterpart.
Methods: Formalin-fixed paraffin-embedded tissues from 55 cases of oligodendrogliomas (34 World Health Organization [WHO] grade II and 21 WHO grade III tumors) were subjected to immunohistochemistry. MIB-1 LI was calculated, and a semiquantitative scoring system for expression of PDGF and PDGFRalpha was used.
Results: MIB-1 LI and PDGF expression increased with histologic grades of malignancy ("t" test, P < .001 and Mann Whitney test, U = 109, P < .001 respectively). The PDGF expression scores had a positive correlation with MIB-1 LI, irrespective of tumor grade (Pearson's correlation coefficient, r = 0.566; P < .001). However, there was no significant difference of PDGFRalpha expression between 2 grades of tumors.
Conclusions: The results of this study showed that MIB-1 LI is a rapid and cost-effective modality for predicting tumor grade in oligodendrogliomas. Immunohistochemistry for PDGF was found to be useful in differentiating various grades of oligodendroglioma, and therefore, it may be involved in tumor cell proliferation and malignant transformation. Platelet-derived growth factor receptor alpha, although expressed in oligodendroglial neoplasms, was not found to be useful in predicting tumor grade.