The prognostic significance of indoleamine-2,3-dioxygenase and the receptors for transforming growth factor β and interferon γ in metastatic lymph nodes in malignant melanoma

We analyzed the prognostic significance of indoleamine-2,3-dioxygenase (IDO) and type 1 receptors for transforming growth factor beta (TGF-βR1) and interferon gamma (IFN-γR1) in resected nodal metastases of 48 malignant melanoma patients. In 32 cases the corresponding skin tumors were available. We used immunohistochemical (IHC) staining which was assessed by pathologists and by a computer-aided algorithm that yielded quantitative results, both absolute and relative. We correlated the results with the patient outcome. We identified absolute computer-assessed IDO levels as positively correlated with increased risk of death in a multivariate model (HR = 1.02; 95% CI: 1.002-1.04; p = 0.03). In univariate analysis, patients with IDO levels below the median had a better overall survival time (30.3 vs. 17.5 months; p = 0.03). TGF-βR1 and IFN-γR1 expression was modestly correlated (R = 0.34; p < 0.05) and TGF-βR1 expression was lower in lymph nodes than in matched primary skin tumors (Z = 2.87; p = 0.004). The pathologists’ and computer-aided IHC assessment demonstrated high correlation levels (R = 0.61, R = 0.74 and R = 0.88 for IDO, TGF-βR1 and IFN-γR1, respectively). Indoleamine-2,3-dioxygenase is prognostic for the patient outcome in melanoma with nodal involvement and should be investigated prospectively for its predictive significance. IHC assessment by computer-aided methods is recommended as its gives IHC more objectivity and reproducibility.