ABSTRACT
Chromosome 9p21 gene copy number in Ewing's sarcoma family of tumour (ESFT) cell lines and primary ESFT has been evaluated using Multiplex Ligation-dependent probe amplification, and the clinical significance of CDKN2A loss and p16/p14(ARF) expression investigated. Homozygous deletion of CDKN2A was identified in 4/9 (44%) of ESFT cell lines and 4/42 (10%) primary ESFT; loss of one copy of CDKN2A was identified in a further 2/9 (22%) cell lines and 2/42 (5%) tumours. CDKN2B was co-deleted in three (33%) cell lines and two (5%) tumours. Co-deletion of the MTAP gene was observed in 1/9 (11%) cell lines and 3/42 (7%) tumours. No correlation was observed between CDKN2A deletion and clinical parameters. However, co-expression of high levels of p16/p14(ARF) mRNA predicted a poor event-free survival (P=0.046, log-rank test). High levels of p16/p14(ARF) mRNA did not correlate with high expression of p16 protein. Furthermore, p16 protein expression did not predict event-free or overall survival. Methylation is not a common mechanism of p16 gene silencing in ESFT. These studies demonstrate that loss (homozygous deletion or single copy) of CDKN2A was not prognostically significant in primary ESFT. However, high levels of p16/p14(ARF) mRNA expression were predictive of a poor event-free survival and should be investigated further.
Subject(s)
Bone Neoplasms/genetics , Chromosomes, Human, Pair 9 , Genes, p16 , Sarcoma, Ewing/genetics , Bone Neoplasms/mortality , Bone Neoplasms/pathology , Cell Line, Tumor , Chromosome Mapping , Cyclin-Dependent Kinase Inhibitor p16/deficiency , Cyclin-Dependent Kinase Inhibitor p16/genetics , DNA, Neoplasm/genetics , DNA, Neoplasm/isolation & purification , Gene Deletion , Humans , Prognosis , RNA, Neoplasm/genetics , RNA, Neoplasm/isolation & purification , Reverse Transcriptase Polymerase Chain Reaction , Sarcoma, Ewing/mortality , Sarcoma, Ewing/pathology , Survival AnalysisABSTRACT
A 14-year-old boy presented with a soft tissue swelling on the outer aspect of his left upper arm. Examination of the tumor by light microscopy showed a small round cell tumor with a rare focus of myogenic differentiation. Myogenic differentiation was confirmed on ultrastructural examination by immunohistochemistry and reverse transcriptase polymerase chain reaction (RT-PCR). Conventional G-banding and fluorescent in situ hybridization (FISH) demonstrated a complex variant of t(21;22)(q22;q12). By RT-PCR, the EWS-ERG fusion transcript was defined as type 9e. This tumor was unusual in that it showed characteristics of myogenic and neural differentiation, and contained a rearrangement of the EWS gene consistent with a diagnosis of Ewing's sarcoma. This supports the hypothesis that a class of biphenotypic childhood sarcomas, with features of myogenic and neural differentiation, exists that may be related to the Ewing's sarcoma family of tumors.
