A study has shown that the chemotherapeutic agents mitomycin C, mitoxantrone and doxorubicin, as well as a monofunctional alkylating agent, ethylmethanesulfonate (EMS), induced deletions of expanded CTG/CAG repeats in the 5′-untranslated region (UTR) of the myotonic dystrophy protein kinase (DMPK) gene in myotonic dystrophy type 1 (DM1) patient lymphoblasts [51]. The gene discussed is DMPK; the disease is myotonic dystrophy type 1.