Cardiac expression of TOP2 isoforms and its response to DRZ. (A) Top2a/b Western blot of heart tissues from B6 mice injected i.p. with 200 mg/kg DRZ. Whole hearts were removed 6, 24 or 48 h after injection. Western blot was performed with an antibody detecting both Top2a and Top2b under conditions permitting the resolving of these isoforms in H9C2 cells (the leftmost lane). (B) TOP2A and TOP2B mRNA expression levels in different human or mouse organs derived from online available RNA-Seq data (NCBI, GEO accession number GSE30352). (C) Western blot of heart tissues from B6 mice injected i.p. with 200 mg/kg DRZ and/or 20 mg/kg DOX, DRZ was given 30 min before DOX. Hearts were removed 24 h later for Western blot analysis using an antibody against Top2a and Top2b.