Expression of Cytoplasmic 8-oxo-Gsn and MTH1 Correlates with Pathological Grading in Human Gastric Cancer.

BACKGROUND Cancers have dysfunctional redox regulation resulting in production of reactive oxygen species (ROS), damaging DNA, RNA and free NTPs, and causing the accumulation of oxidative nucleic acids in cytoplasm. The major types are 8-oxo-7,8-dihydroguanine(8-oxoGsn) in RNA and 8-oxo-7,8-dihydro-2' deoxyguanosine(8-oxodGsn) in Mt-DNA. The MTH1 protein sanitizes oxidized nucleotide pools from NTPs to monophosphates, preventing the occurrence of transversion mutations. This study concerned cytoplasmic 8-oxodGsn/Gsn and MTH1 expression in gastric cancer and para-cancer tissues and elucidated roles of nucleic-acid oxidation and anti-oxidation. MATERIALS AND METHODS A polymer HRP detection system was used to detect 8-oxo-Gsn/dGsn and MTH1 expression in 51 gastric cancer and para-cancer tissue samples. Analyses of patient clinical and pathological data were also performed. RESULTS The expression of MTH1 and the 8-oxo-dGsn/Gsn ratio were significantly higher in cancer tissues than para-cancer tissues (P<0.05). Cytoplasmic 8-oxo-Gsn and MTH1 were both found to positively correlate (P<0.05) with tumor differentiation, while no significant associations were found with gender, age, invasion depth, lymph node metastasis and clinical stage (P>0.05). CONCLUSIONS We found 8-oxo-dGsn/Gsn and MTH1 are both highly expressed in gastric cancer tissues, especially in well differentiated lesions. In addition, oxidated mtDNA is prevalently expressed in gastric cancers, while 8-oxo-Gsn expression in cytoplasmic RNA is a bit lower, but more selectively.