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No preferential loss of one parental allele of chromosome 17p13.3 in childhood medulloblastoma

Medulloblastomas are the most frequent malignant tumors of the central nervous system in childhood. Loss of heterozygosity of the telomeric part of chromosome 17p has been described frequently in these tumors, suggesting a possible second tumor‐suppressor gene in this region apart from the p53 gene. Using restriction‐fragment‐length polymorphism and microsatellite polymorphism analysis, we screened 16 medulloblastomas for 17p 13.3 deletions and compared the DNA patterns of patients' tumors and normal tissues with those of one or both parents. Loss of heterozygosity of chromosome 17p 13.3 could be detected in 6 out of 16 tumors (37.5%). In 4 of these 6 tumors the maternal allele was deleted, in 2 tumors the paternal allele. Although the number of tumors investigated is limited, we find no evidence that genomic imprinting of the chromosomal region most frequently deleted in medulloblastoma plays a role in tumorigenesis.