Abstract
MTH1 (MutT Homolog 1) protein is one of the enzymes that protect cells from mutagenetic actions of reactive oxygen species. It sanitizes the pool of free nucleotides, making sure that oxidized dNTPs are not incorporated into the DNA. Any misfunction of it would lead to mutations. As such, it has attracted interest of cancer researchers, and multiple studies have been conducted over the years to determine its role in tumor cells. It has been found that MTH1 is not downregulated in most tumor tissues but, to the contrary, often overexpressed. This suggests that MTH1 is used by cancer as an adaptation to increased oxidative stress caused by metabolic reprogramming to support excessive proliferation. Based on this premise, many recent studies have evaluated MTH1 as either prognostic factor, general biomarker or therapeutic target in cancer. Here, we summarize all available research on MTH1 mRNA, protein and its enzymatic activity in clinical samples across various cancer types, identifying a subset of cancers where MTH1 plays an important role. This is particularly evident in cancers characterized by high metabolic activity and oxygen-rich environments, such as hepatocellular carcinoma, renal cell carcinoma, or non-small cell lung adenocarcinoma.