Genome-wide single-nucleotide resolution of oxaliplatin-DNA adduct repair in drug-sensitive and -resistant colorectal cancer cell lines.
Courtney M VaughnChristopher P SelbyYanyan YangDavid S HsuAziz SancarPublished in: The Journal of biological chemistry (2020)
Platinum-based chemotherapies, including oxaliplatin, are a mainstay in the management of solid tumors and induce cell death by forming intrastrand dinucleotide DNA adducts. Despite their common use, they are highly toxic, and approximately half of cancer patients have tumors that are either intrinsically resistant or develop resistance. Previous studies suggest that this resistance is mediated by variations in DNA repair levels or net drug influx. Here, we aimed to better define the roles of nucleotide excision repair and DNA damage in platinum chemotherapy resistance by profiling DNA damage and repair efficiency in seven oxaliplatin-sensitive and three oxaliplatin-resistant colorectal cancer cell lines. We assayed DNA repair indirectly as toxicity and directly measured bulky adduct formation and removal from the genome by slot blot and repair capacity in an excision assay, and used excision repair sequencing (XR-seq) to map repair events genome-wide at single-nucleotide resolution. Using this combinatorial approach and proxies for oxaliplatin-DNA damage, we observed no significant differences in repair efficiency that could explain the relative sensitivities and chemotherapy resistances of these cell lines. In contrast, the levels of oxaliplatin-induced DNA damage were significantly lower in the resistant cells, indicating that decreased damage formation, rather than increased damage repair, is a major determinant of oxaliplatin resistance in these cell lines. XR-seq-based analysis of gene expression revealed up-regulation of membrane transport pathways in the resistant cells, and these pathways may contribute to resistance. In conclusion, additional research is needed to characterize the factors mitigating cellular DNA damage formation by platinum compounds.
Keyphrases
- dna damage
- dna repair
- oxidative stress
- genome wide
- gene expression
- cell death
- dna methylation
- single cell
- induced apoptosis
- dna damage response
- single molecule
- cell cycle arrest
- emergency department
- high throughput
- squamous cell carcinoma
- locally advanced
- endothelial cells
- radiation therapy
- cell free
- adverse drug
- copy number
- circulating tumor
- drug induced
- high glucose