TCF3 and Burkitt lymphoma: This implies that additional events may occur in vivo to regulate TCF3 levels, possibly independent of the presence of EBV, as supported by the observation that DNA demethylation by Aza leads to a significant rescue of TCF3 mRNA levels in both EBV(+) and EBV(−) BLs; this also indicates that methylation at different CpG positions could be one of the mechanisms responsible for TCF3 deregulated expression in EBV− BL, additional to the frequent mutation rate reported in sporadic BL.