NO PREFERENTIAL PARENT OF ORIGIN FOR THE ISOCHROMOSOME 17Q IN CHILDHOOD PRIMITIVE NEUROECTODERMAL TUMOR (MEDULLOBLASTOMA)

We have shown that an i(17q) is the most frequent abnormality in centr al nervous system primitive neuroectodermal tumors (PNETs; medulloblas toma), implicating the presence of a tumor suppressor gene which maps to 17p. In the present study, we investigated whether the deletion of chromosome arm 17p that results from the formation of the i(17q) is pr eferentially of maternal or paternal origin. Eight cases of primary PN ETs of the posterior fossa were examined at five polymorphic loci whic h map to 17p13. Two or three informative loci were detected in each fa mily. Of the eight cases, four tumors evidenced loss of the paternal a llele for loci on 17p13 and four tumors demonstrated maternal deletion s. Although the number of cases is relatively small, these studies do not implicate the loss of an imprinted gene as a mechanism for tumorig enesis in children with central nervous system PNETs/medulloblastoma. (C) 1997 Wiley-Liss, Inc.