Differential Expression of FGF Receptor-1 and FGF Receptor-2 Is Associated with Malignant Progression of Gliomas

Human gliomas were examined for alternative splicing of extracellular domain of FGFR1 (fibroblast growth factor receptor-1). The expression of the 2 Ig domain form of FGFR1 (FGFR1ββ) relative to the expression of the 3-Ig domain form of FGFR1 (FGFR1-a) was significantly elevated in glioblastoma multiforme (GBM). Although low-grade astrocytomas (LGAs) showed less FGFR1-ββ than GBMs but more than normal brains, anaplastic astrocytomas (AAs) had expression of FGFR1-β intermediate between GBMs and LGAs. The expression ratio of FGFR1-β and FGFR1-α had positive correlation with malignancy of gliomas. These results indicate that alternative RNA splicing of the FGFR1 may be associated with malignant progression of gliomas. We also analyzed the expression of FGFR2 transcript in normal brains and gliomas. GBMs showed no expression or a decreased level of FGFR2 transcript compared to adjacent normal brains. Because the FGFR2 gene localizes on chromosome 10q26, which is often lost in glioblastoma cells, and the tumor suppressor gene is inferred to exist in chromosome 10q24–q26, it is suggested that the putative tumor suppressor gene is correlated with the lack of FGFR2.