SFRP1 and B-cell chronic lymphocytic leukemia: Marked differences in the levels of aberrant DNA methylation between SFRP genes was found, namely, SFRP1 was methylated in 100% of cases, SFRP2 in 55%, SFRP4 in 30%, and SFRP5 in 15%, suggesting that epigenetic silencing of these SFRPs and especially SFRP1 could be important in the onset of CLL.