In another study, where DNA methylation was compared within immunoglobulin heavy-chain gene variable region (IGVH) mutated/unmutated subgroups of CLL, it was reported that in IGVH-unmutated cells, tumor suppressor genes such as von Hippel–Lindau (VHL), Abelson interactor 3 (ABI3), and immunoglobulin superfamily member 4 (IGSF4) were found hypermethylated while genes associated with cell proliferation and migration such as adenosine A3 receptor (ADORA3) and perforin 1 (PRF1) were hypomethylated [26]. Here, PRF1 is linked to B-cell chronic lymphocytic leukemia.