CGH analysis of secondary genetic changes in Ewing tumors:: correlation with metastatic disease in a series of 43 cases

The occurrence of secondary chromosome changes is frequent in Ewing tumors, in particular trisomies for chromosomes 8 and 12, and unbalanced (1;16) translocations leading to gains of 1q and losses of 16q. The prognostic value of these secondary aberrations has not been statistically demonstrated. We report here a CGH analysis of a series of 43 primary tumors corresponding to 21 localized and 22 metastatic tumors. For five of them, a sufficient amount of DNA for the CGH analysis was available from the frozen samples. For 19 samples, a preliminary step of DOP-PCR amplification of the DNA was necessary. For the last 19 tumors, DNA was obtained after DOP-PCR amplification of small amount of DNA contaminating the RNA. As a whole, the main chromosome imbalances previously described, such as trisomies for 1q, 8, and 12, were observed. It is noteworthy that the mean number of imbalances was more frequent in localized versus metastatic tumors. Gain of 1q was more frequent in metastatic than in localized tumors. Nevertheless, these two results do not reach statistical significance. Conversely, a statistically significant excess of copy number of chromosome 2 was observed in non-metastatic tumors, suggesting that this imbalance, which has never been previously reported, could be associated with more favorable tumor behavior.