6-Thioguanine damages mitochondrial DNA and causes mitochondrial dysfunction in human cells

► Thiopurines are widely used immunosuppressant and anticancer drugs. ► They cause 6-thioguanine (6-TG) accumulation in DNA. ► 6-TG in mitochondrial DNA (mtDNA) is rapidly oxidized. ► Oxidized 6-TG inhibits mtDNA replication and transcription. ► Loss of mtDNA-encoded proteins leads to mitochondrial dysfunction.