The Existence of MTH1-independent 8-oxodGTPase Activity in Cancer Cells as a Compensatory Mechanism against On-target Effects of MTH1 Inhibitors.
Mol Cancer Ther
; 19(2): 432-446, 2020 02.
Article
en En
| MEDLINE
| ID: mdl-31744893
ABSTRACT
Investigations into the human 8-oxodGTPase, MutT Homolog 1 (MTH1), have risen sharply since the first-in-class MTH1 inhibitors were reported to be highly tumoricidal. However, MTH1 as a cancer therapeutic target is currently controversial because subsequently developed inhibitors did not exhibit similar cytotoxic effects. Here, we provide the first direct evidence for MTH1-independent 8-oxodGTPase function in human cancer cells and human tumors, using a novel ATP-releasing guanine-oxidized (ARGO) chemical probe. Our studies show that this functionally redundant 8-oxodGTPase activity is not decreased by five different published MTH1-targeting small molecules or by MTH1 depletion. Significantly, while only the two first-in-class inhibitors, TH588 and TH287, reduced cancer cell viability, all five inhibitors evaluated in our studies decreased 8-oxodGTPase activity to a similar extent. Thus, the reported efficacy of the first-in-class MTH1 inhibitors does not arise from their inhibition of MTH1-specific 8-oxodGTPase activity. Comparison of DNA strand breaks, genomic 8-oxoguanine incorporation, or alterations in cellular oxidative state by TH287 versus the noncytotoxic inhibitor, IACS-4759, contradict that the cytotoxicity of the former results solely from increased levels of oxidatively damaged genomic DNA. Thus, our findings indicate that mechanisms unrelated to oxidative stress or DNA damage likely underlie the reported efficacy of the first-in-class inhibitors. Our study suggests that MTH1 functional redundancy, existing to different extents in all cancer lines and human tumors evaluated in our study, is a thus far undefined factor which is likely to be critical in understanding the importance of MTH1 and its clinical targeting in cancer.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Antimutagênicos
/
Monoéster Fosfórico Hidrolasas
/
Enzimas Reparadoras del ADN
/
Neoplasias
Tipo de estudio:
Observational_studies
Límite:
Humans
Idioma:
En
Revista:
Mol Cancer Ther
Asunto de la revista:
ANTINEOPLASICOS
Año:
2020
Tipo del documento:
Article