Park, Yong-Koo

Aims and background Id helix-loop-helix proteins function as regulators of cell growth and differentiation. However, they can induce malignant transformation when overexpressed. The EWS/ETS chimeric proteins in Ewing sarcoma act as aberrant transcription factors leading to tumorigenic processes. An enhanced expression of the Id2 gene in Ewing sarcoma cells was previously shown by gene array techniques. We investigated the expression of Id2 at the protein and gene level in Ewing sarcoma. Methods We evaluated the expression of Id2 protein using immunohistochemistry in formalin-fixed, paraffin-embedded specimens from a total of 71 cases of Ewing sarcoma. Additionally, a Ewing sarcoma cell line was examined by real-time quantitative PCR. Results Id2 expression was observed in 65 cases (91.5%) of the 71 total cases examined and a high level of Id2 expression was observed in 45 of these cases (63.8%). In tumor cells, Id2 proteins displayed cytoplasmic as well as nuclear localization. The amplification of the Id2 gene was not noted in a Ewing sarcoma cell line using real-time quantitative PCR. The crossing points of Id2 in the Ewing sarcoma cell line, control fibroblast, and osteosarcoma cell line were 18.54 ± 0.16, 18.25, and 18.34, respectively. Conclusions Our data support a role for increased Id2 protein expression in Ewing sarcoma. However, this overexpression of the Id2 protein could not be confirmed by a corresponding change at the gene level in a Ewing sarcoma cell line.

Aims and Background HuR is a member of the family of ELAV (embryonic lethal abnormal vision)-like proteins that stabilize several cellular mRNAs by binding to AU-rich elements in the 3’ untranslated region of the mRNA. Cyclooxygenase-2 (COX-2) is a well known enzyme that promotes tumor growth and metastasis. Recent studies have shown that HuR can stabilize the mRNA of COX-2, and cytoplasmic expression of HuR is associated with increased COX-2 expression in some cancers. The aim of this study was to investigate the correlation between COX-2 and HuR in Ewing sarcoma. Methods The expression patterns for HuR and COX-2 were assessed via immunochemical analysis of 70 Ewing sarcoma samples. Results Nuclear HuR expression was observed in 12 of 70 (17.1%) cases, but cytoplasmic expression was not observed. COX-2 expression was seen in 25 of 70 (35.7%) samples. Nuclear HuR and COX-2 were simultaneously expressed in 8 of 70 (11.4%) samples. The expression of nuclear HuR was significantly associated with COX-2 expression (P = 0.014). Neither HuR nor COX-2 expression showed a correlation with age or sex. Conclusions COX-2 expression in Ewing sarcoma may not be directly related to mRNA stabilization by HuR. However, a correlation between COX-2 expression and nuclear HuR expression through indirect mRNA stabilization can be suggested.