Testicular toxicity is a frequent adverse effect of cancer chemotherapy that has no effective clinical biomarker. To find new biomarkers, we focused on epigenetic mechanisms in the male germline. We investigated the DNA methylation status of the male germline during testicular toxicity induced by doxorubicin (DXR), a widely used anticancer agent. We established mouse models of early stage testicular toxicity and testicular pre-toxicity by the administration of 0.2 mg/kg and 0.02 mg/kg DXR, respectively, tWice weekly for 5 weeks. Histological analysis showed sparse abnormalities in testicular tissue; however, western blotting analysis revealed reduced testicular expression levels of DNA methyltransferases DNMT3a and DNMT3b in both DXR-treated groups. Interestingly, comprehensive sperm DNA meihylation analysis using Methyl-CpG binding domain protein-enriched genome sequencing revealed that hypothethylation was the most frequent change induced by DXR. These findings suggest that sperm DNA methylation status may be used as an early diagnostic marker for testicular changes not detected by conventional toxicity analysis. (C) 2018 Elsevier Inc. All rights reserved.