Deletion of Ip36 in childhood endodermal sinus tumors by two-color fluorescence in situ hybridization: A pediatric oncology group study

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Abstract
Childhood endodermal sinus tumors (CESTs) are a unique category of germ cell tumors involving the testis and extragonadal region in children less than 4 years of age. Recent studies of CEST have shown recurrent cytogenetic abnormalities involving the short arm of chromosome I, most commonly, a deletion of distal Ip. Experience with neuroblastomas has shown that cytogenetic analyses may underestimate the frequency of Ip deletion. To determine the frequency of deletion of Ip in CEST and to verify that Ip is, in fact, deleted and not translocated, we analyzed ten tumors by two‐color fluorescence in situ hybridization on single‐cell suspensions of interphase nuclei by using a cosmid probe from the PITSLRE kinase (p58) locus (previously mapped to Ip36) cohybridized with plasmid probe pUCI.77 (which recognizes the Iq heterochromatic region) to determine the copy number of chromosome I. Eight of the ten tumors examined showed evidence of deletion of Ip36. Five of the eight tumors exhibited multiple subclones, and all subclones showed deletion of at least one copy of Ip36, indicating that the deletion probably occurred before the development of chromosome I aneusomy. We conclude that deletions of the short arm of chromosome I, specifically Ip36, do occur in CEST and probably occur at a higher incidence than that found in neuroblastoma. Further studies are needed to determine the degree of overlap of the common area of deletion in CEST with that of neuroblastoma and to determine whether Ip deletion in CEST has prognostic significance. Genes Chromosom Cancer 16:15–20 (1996).