CXCR4 and metastatic neoplasm: Whether the apparent discrepancy in correlation of CXCR4 gene transcript ([15]) and CXCR4 protein expression (current study) with metastatic disease in EWS reflects true biological differences (e.g. differences at the mRNA level are not reflected at the protein level (or vice versa), due to post-transcriptional and/or -translational regulation) or are attributable to technical differences (e.g. different samples and/or sensitivity and dynamic ranges of the methods used for mRNA transcript and protein analysis) is not known.