Our laboratory previously demonstrated that acquired resistance to etoposide in a human K562 leukemia cell line, K/VP.5, was associated with decreased TOP2α/170 mRNA/protein expression levels and an increased expression of TOP2α/90 (UniProtKB accession number A0A4D6UXC9), a novel TOP2α isoform that results from intron 19 (I19) IPA [11,15,16]. Here, TOP2A is linked to leukemia.