Expression of N-myc, c-myc and c-erbB-1 proto-oncogenes in cerebral primitive neuroectodermal tumors (PNET)

Neuroectodermal tumors demonstrate a relatively high incidence of proto-oncogenes amplification. This study attempted to determine the frequency of overexpression of three genes: N-myc, c-myc and c-erbB-1, in human PNET. Immunohistochemical studies revealed 5 to 74% neoplastic cells with positive immunoreactivity to anti-c-myc antibody in all investigated samples. In 3 cases the reactivity was particularly strong and present in more than 50% of tumor cells. Northern blot analysis revealed normal (2.3-kb in size) but significantly higher level of c-myc transcripts in these cases. By using anti-EGFR antibody 3 tumors disclosed 10 to 65% neoplastic cells with positive immunoreactivity. There was no rearrangement detected of their c-erbB-1 or N-myc genes by means of applied methods. Our results suggest that overexpression of c-myc gene is present in 10% of PNET but it is not the consequence of gene amplification. Amplification of N-myc and c-erbB-1 are rare events during PNET development.