TK1 and non-Hodgkin lymphoma: Aberrant DNA methylation of this gene occurs in the promoter region in lymphoid malignancies of B-cell phenotype Peripheral blood TK1 (Hs.515122, UNIQID 23826 and 34790) isozyme is a useful independent biochemical marker for the subgroup of adult non-Hodgkin's lymphoma who respond poorly to current therapy [18].