CAT and B-cell chronic lymphocytic leukemia: Consistent with the catalase protein levels, we also detected reduced levels of catalase transcripts in CLL cells from majority of CLL patients (8 of 10) as compared to the mean value of catalase mRNA levels in normal B-cells (n = 5) (Fig. 2B); suggesting that catalase expression in CLL cells is likely regulated at the level of transcription.