Prognostic value of xanthine oxidoreductase expression in patients with non-small cell lung cancer

Xanthine oxidoreductase (XOR) is a rate-limiting enzyme in the purine metabolism pathway. Lack of XOR expression is associated with unfavorable clinical outcomes. The objective of this study was to correlate XOR expression with prognosis in surgically resected non-small cell lung cancer (NSCLC).

Immunohistochemical staining was performed on deparaffinized specimens from 82 patients with stage I-IV NSCLC using a polyclonal anti-XOR rabbit antibody. Cytoplasmic XOR staining was scored on frequency and intensity scales from 0 to 4 with low expression defined as 0-1 and high expression defined as ≥2-4. XOR immunostaining was correlated with clinical characteristics and outcomes and analyzed using Kaplan-Meier and Cox proportional hazard methods.

Positive XOR expression was observed in 53/82 cases (65%). Patients with high XOR frequency had a longer median survival of 3053 days (95% CI: 2190-3916) vs. 592 days (95% CI: 492-692 days) for patients with low XOR frequency, p=0.0089, HR 0.47. Neither XOR intensity nor the overall score of XOR frequency multiplied by XOR intensity demonstrated any significant association with survival. Surgical resection was performed on 61 patients of which 34 (56%) received adjuvant chemotherapy. Patients who received adjuvant chemotherapy with low XOR expression, 15/34 (44%) had a shortened median survival compared with patients who received adjuvant chemotherapy with high XOR expression (543 days vs. 2023 days, respectively, p=0.007 and HR=0.33).

Low XOR expression was associated with shortened survival and also conferred a worse prognosis for patients with NSCLC who received adjuvant chemotherapy. Further studies of the XOR pathway are warranted to validate and mechanistically explain these outcomes.