Objective: The antifolate chemotherapy agent pemetrexed has been widely used to treat non-small-cell-lung-cancer (NSCLC), but there is no clinically validated biomarker to select patients likely to respond. The aim of this study was to assess two proteins involved in DNA repair mechanisms, uracil DNA glycosylase (UDG) and BRCA1 as potential prognostic biomarkers in NSCLC patients treated with pemetrexed-based chemotherapy.
Material and methods: Formalin-fixed-paraffin-embedded tumor specimens from 119 patients with advanced NSCLC treated with pemetrexed between 2004 and 2011 were retrospectively analyzed. Expression of UDG, BRCA1, and known prognostic factors ALK, TTF-1, thymidylate synthase and folylpolyglutamate synthase was assessed by immunohistochemistry using H-SCORE (product of percent stained cells and intensity of expression). Progression-free (PFS) and overall survival (OS) served as reference endpoint.
Results: Most NSCLC tumor samples had UDG positivity in at least 5% of tumor cells and 34% samples had more than 50% positive tumor cells. Using the median expression value as threshold, high UDG expression (H-SCORE≥75) was significantly associated with shorter median PFS (3-year PFS 7% vs. 37%, p = 0.045) and a trend for shorter OS (3-year OS 15% vs 42%, p = 0.066) compared to patients with low UDG. In multivariable Cox analysis, the association between high UDG and shorter PFS was close to statistically significant (p = 0.08) at a significance level of 0.05 after controlling for age, gender, ALK- and TTF1-status with hazard ratio of 2.1. Grouping patients according to combined UDG and BRCA1 expression, patients with a profile of UDGhigh/BRCA1high had the shortest PFS and OS compared to all other patient groups (p = 0.007 and 0.02, respectively).
Conclusion: Our results demonstrate an important prognostic role for high UDG expression in pemetrexed-treated NSCLC patients, in addition to its previously reported role in pemetrexed cytotoxicity. High UDG expression was predictive of shorter PFS and OS, and patients with a combined profile of UDGhigh/BRCA1high had the poorest outcome following pemetrexed treatment.
Keywords: BRCA1; Non-small cell lung cancer; Pemetrexed; UDG; Uracil DNA glycosylase.
Copyright © 2018. Published by Elsevier B.V.