Inhibition of Oxidized Nucleotide Sanitation By TH1579 and Conventional Chemotherapy Cooperatively Enhance Oxidative DNA Damage and Survival in AML

The Effects of Black Raspberry as a Whole Food-Based Approach on Biomarkers of Oxidative Stress in Buccal Cells and Urine of Smokers

Cigarette smoke is a rich source of free radicals that can promote oxidative stress and carcinogenesis, including head and neck squamous cell carcinoma (HNSCC) development; importantly, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-iso-prostaglandin F2α (8-isoprostane) are biomarkers of oxidative stress. Several mechanisms, including the antioxidant properties of black raspberry (BRB), account for their chemopreventive effects. In the present clinical trial, we tested the hypothesis that BRB administration reduces biomarkers levels of oxidative stress in buccal cells and urine of smokers. One week after enrolling 21 smokers, baseline buccal cells and urine samples were collected before the administration of BRB lozenges for 8 weeks (5/day, 1 gm BRB/lozenge). Buccal cells and urine samples were collected at the middle and the end of BRB administration. The last samples were collected after the BRB cessation (washout period). We analyzed levels of 8-oxodG and 8-isoprostane (LC/MS-MS), urinary cotinine (ELISA), and creatinine (spectrophotometry). BRB significantly reduced the levels of 8-oxodG by 17.08% (P = 0.00079) in buccal cells and 12.44% (P = 0.034) in urine at the middle of BRB administration as compared with baseline; the corresponding values at the end of BRB administration were 16.46% (P = 0.026) in buccal cells and 25.72% (P = 0.202) in urine. BRB had no significant effect on the levels of urinary 8-isoprostane. BRB's capacity to inhibit 8-oxodG formation of smokers' buccal cells and urine is clearly evident and the reduction in 8-oxodG suggests that antioxidant abilities are central to BRB's HNSCC chemopreventive properties.

PREVENTION RELEVANCE

Cigarette smoke contains highly active components namely free radicals that can promote oxidative stress and oral cancer. We found that black raspberry (BRB) inhibited the formation of oxidative stress markers in the oral cavity and urine of smokers suggesting the antioxidant abilities of BRB in preventing oral cancer.

Targeting the nucleic acid oxidative damage repair enzyme MTH1: a promising therapeutic option

The accumulation of reactive oxygen species (ROS) plays a pivotal role in the development of various diseases, including cancer. Elevated ROS levels cause oxidative stress, resulting in detrimental effects on organisms and enabling tumors to develop adaptive responses. Targeting these enhanced oxidative stress protection mechanisms could offer therapeutic benefits with high specificity, as normal cells exhibit lower dependency on these pathways. MTH1 (mutT homolog 1), a homolog of Escherichia coli's MutT, is crucial in this context. It sanitizes the nucleotide pool, preventing incorporation of oxidized nucleotides, thus safeguarding DNA integrity. This study explores MTH1's potential as a therapeutic target, particularly in cancer treatment, providing insights into its structure, function, and role in disease progression.

The Role of 8-oxoG Repair Systems in Tumorigenesis and Cancer Therapy

Tumorigenesis is highly correlated with the accumulation of mutations. The abundant and extensive DNA oxidation product, 8-Oxoguanine (8-oxoG), can cause mutations if it is not repaired by 8-oxoG repair systems. Therefore, the accumulation of 8-oxoG plays an essential role in tumorigenesis. To avoid the accumulation of 8-oxoG in the genome, base excision repair (BER), initiated by 8-oxoguanine DNA glycosylase1 (OGG1), is responsible for the removal of genomic 8-oxoG. It has been proven that 8-oxoG levels are significantly elevated in cancer cells compared with cells of normal tissues, and the induction of DNA damage by some antitumor drugs involves direct or indirect interference with BER, especially through inducing the production and accumulation of reactive oxygen species (ROS), which can lead to tumor cell death. In addition, the absence of the core components of BER can result in embryonic or early post-natal lethality in mice. Therefore, targeting 8-oxoG repair systems with inhibitors is a promising avenue for tumor therapy. In this study, we summarize the impact of 8-oxoG accumulation on tumorigenesis and the current status of cancer therapy approaches exploiting 8-oxoG repair enzyme targeting, as well as possible synergistic lethality strategies involving exogenous ROS-inducing agents.

Targeting the DNA damage response and repair in cancer through nucleotide metabolism

The exploitation of the DNA damage response and DNA repair proficiency of cancer cells is an important anticancer strategy. The replication and repair of DNA are dependent upon the supply of deoxynucleoside triphosphate (dNTP) building blocks, which are produced and maintained by nucleotide metabolic pathways. Enzymes within these pathways can be promising targets to selectively induce toxic DNA lesions in cancer cells. These same pathways also activate antimetabolites, an important group of chemotherapies that disrupt both nucleotide and DNA metabolism to induce DNA damage in cancer cells. Thus, dNTP metabolic enzymes can also be targeted to refine the use of these chemotherapeutics, many of which remain standard of care in common cancers. In this review article, we will discuss both these approaches exemplified by the enzymes MTH1, MTHFD2 and SAMHD1. © 2022 The Authors. Molecular Oncology published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.