Hypomethylation may change Alu transcription level Dajun Deng, Peking University School of Oncology 15 March 2010 It is interesting that expessed Alu repeat may be a good reference for transcription normalization of target genes. However, it is well known that Alu elements in the human genome are hypomethylated in many cases such as cancer tissues and tissues exposed to cytotoxic chemicals and anoxic conditions. It is likely that transcription activity of Alu elements may change due to the hypomethylation, which might reduce the proposed normalization value of Alu transcripts. It will be useful if authors could exclude effect of the hypomethylation on Alu transcription. Competing interests I declare that I have no competing interests.