EXPRESSION OF PLATELET-DERIVED GROWTH-FACTOR TRANSCRIPTS IN MEDULLOBLASTOMAS AND EPENDYMOMAS

We used Northern blot analysis to measure the expression of mRNA for p latelet-derived growth factor subunit A (PDGF-B), PDGF-B and the PDGF- alpha receptor (PDGFR-alpha) and PDGF-beta receptor (PDGFR-beta) in ep endymomas and medulloblastomas. We analyzed tissue from 5 patients for each tumor type, looking specifically for components of an autocrine or paracrine system in these tumors. PDGF-A was expressed in all tumor s, PDGFR-alpha, which binds all 3 PDGF isoforms, was only found in epe ndymomas, Thus only ependymomas appeared to have a potential for using PDGFR-alpha autocrine loops. PDGF-B was expressed only in ependymomas , although the PDGFR-beta was expressed in both medulloblastomas and e pendymomas. Again, therefore, only ependymomas appear to have a potent ial autocrine loop with PDGFR-beta. These data suggest that ependymoma s have the biochemical prerequisites for autocrine and/or paracrine lo ops using PDGFR-alpha or PDGFR-beta systems, In this they resemble oth er glial tumors such as anaplastic astrocytomas and glioblastomas. Med ulloblastomas do not appear to have the ligand and/or receptor for eit her the PDGFR-alpha or PDGFR-beta autocrine loop.