Somuncu, BernaEkmekcioglu, AysegulAntmen, Fatma MerveErtuzun, TugceDeniz, EmreKeskin, NazliPark, JoonYazici, Ilgu EceSimsek, BusraErman, BatuYin, WhitneyErman, BurakMuftuoglu, Meltem2023-02-212023-02-212022-01-0110.1371/journal.pone.0268391https://hdl.handle.net/11443/2549http://dx.doi.org/10.1371/journal.pone.0268391Synthetic lethality in DNA repair pathways is an important strategy for the selective treatment of cancer cells without harming healthy cells and developing cancer-specific drugs. The synthetic lethal interaction between the mismatch repair (MMR) protein, MutL homolog 1 (MLH1), and the mitochondrial base excision repair protein, DNA polymerasey (Poly) was used in this study for the selective treatment of MLH1 deficient cancers. Germline mutations in the MLH1 gene and aberrant MLH1 promoter methylation result in an increased risk of developing many cancers, including nonpolyposis colorectal and endometrial cancers. Because the inhibition of Poly in MLH1 deficient cancer cells provides the synthetic lethal selectivity, we conducted a comprehensive small molecule screening from various databases and chemical drug library molecules for novel Poly inhibitors that selectively kill MLH1 deficient cancer cells. We characterized these Poly inhibitor molecules in vitro and in vivo, and identified 3,3'-{[}(1,1'-Bipheny1)4',4'-diyl)bis(azo)]bis{[}4-amino-1-naphthalenesu lfonic acid] (congo redCRZinc 03830554) as a high-affinity binder to the Pol y protein and potent inhibitor of the Pol y strand displacement and one-nucleotide incorporation DNA synthesis activities in vitro and in vivo. CR reduced the cell proliferation of MLH1 deficient HCT116 human colon cancer cells and suppressed HCT116 xenograft tumor growth whereas it did not affect the MLH1 proficient cell proliferation and xenograft tumor growth. CR caused mitochondrial dysfunction and cell death by inhibiting Poly activity and oxidative mtDNA damage repair, increasing the production of reactive oxygen species and oxidative mtDNA damage in MLH1 deficient cells. This study suggests that the Pol y inhibitor, CR may be further evaluated for the MLH1 deficient cancers' therapy.ArticleWOS:000843619700133