Prognostic value of nucleotide excision repair and translesion DNA synthesis proteins in muscle-infiltrating bladder carcinoma.

BACKGROUND

Cisplatin (CDDP) remains a key agent in the treatment of muscle-infiltrating bladder carcinoma (MIBC). However, a proportion of MIBC patients do not respond to chemotherapy, which may be caused by the increased repair of CDDP-induced DNA damage. The purpose of this study was to explore the prognostic value of proteins involved in nucleotide excision repair (NER) and translesion DNA synthesis (TLS) in MIBC patients.

METHODS

This is a retrospective analysis of 86 MIBC patients. The XPA, XPF, XPG, ERCC1, POLI, POLH and REV3L proteins were stained in primary bladder tumors and their levels were analyzed both in the total cohort and in a subgroup with metastatic urothelial carcinoma (mUC) that received gemcitabine and CDDP as a first-line therapy. Both cohorts were divided by percentage of cancer cells stained positive for each protein into subgroups with high and low expression. In the same manner, the combined expression of NER (XPA + ERCC1 + XPF + XPG) and TLS (POLI + POLH + REV3L), as the whole pathways, was analyzed.

RESULTS

Mortality was 89.5% at the median follow-up of 120.2 months. In the total cohort, patients with tumors stained positive for XPA, XPG and POLI had significantly worse overall survival (OS) compared to those with negative staining [hazard ratio (HR) = 0.60, 0.62 and 0.53, respectively]. Both XPG and POLI were independent prognostic factors in multivariate analyses (MVA). In addition, an increase in NER and TLS pathway expression was significantly associated with worse OS in the total cohort (HR = 0.54 and 0.60, respectively). In the mUC subgroup, high POLI expression was associated with significant deterioration of OS (HR = 0.56) in univariate analyses, and its independent prognostic value was shown in MVA.

CONCLUSIONS

Our study showed significant correlations between the tumor expression of XPG and POLI, as well as NER and TLS as the whole pathways, and inferior OS. Hence, they could constitute prognostic biomarkers and potentially promising therapeutic targets in MIBC. However, a prospective trial is required for further validation, thereby overcoming the limitations of this study.