Background: Indoleamine 2,3-dioxygenase (IDO1) is an enzyme that acts as an immunomodulatory molecule. It is found in several types of cancer where it seems to be associated with tumor escape due to its immunosuppressive mechanisms. However, the role of IDO1 expression in prostate cancer (PC) is unclear. The aim of our study was to evaluate the expression of IDO1 in localized PC and to correlate with the classic prognostic factor and recurrence after surgical treatment.
Methods: We retrospectively evaluated surgical specimens from 111 patients with localized PC, who underwent radical prostatectomy. Recurrence was defined as a prostate specific antigen (PSA) level exceeding 0.2 ng/mL postoperatively, and the follow-up was 123 months. IDO1 expression was evaluated by immunohistochemistry in 72 cases of which 42 (58%) had biochemical recurrence.
Results: Lower IDO1 expression was associated with higher Gleason score (p = 0.022) and PSA levels (p = 0.042). The multivariate analyses revealed that the loss of IDO1 and higher PSA were independently associated with biochemical recurrence. The chance of recurrence was increased by 85% in patients with lower IDO1 [OR = 0.15; p = 0.009 CI 95% (0.038-0.633)] and increased by 5.5 times in patients with higher PSA [OR = 5.51; p = 0.012 CI 95% (1.435-21.21)]. The recurrence-free survival curve also demonstrates that lower IDO1 was associated with lower time to biochemical recurrence (p = 0.0004).
Conclusion: The loss of IDO1 expression was associated with increased chance of biochemical recurrence, higher PSA, and a Gleason score in localized PC.
Keywords: Biomarkers; Indoleamine 2,3-dioxygenase; Prognosis; Prostate cancer.