Immunohistochemical localization of NAD(P)H:quinone oxidoreductase in conjunctival melanomas and primary acquired melanosis

Purpose. Mitomycin C has been used in the treatment of primary acquired melanosis and melanomas of the conjunctiva. Because there is increasing evidence that NAD(P)H:quinone oxidoreductase (EC 1.6.99.2, NQOl) or DT-diaphorase plays an important role in the bioactivation of mitomycin C, we examined pathologic specimens of these tumors for NQO1 by immunohistochemistry. Methods. Formalin-fixed, paraffin-embedded sections with histologic diagnoses of primary acquired melanosis or conjunctival melanomas were obtained from the Eye Pathology Laboratory, University of Colorado Health Sciences Center. Detection of NQO1 in tissues was performed using standard immunohistochemical techniques with monoclonal antibodies against NQO1 and immunoperoxidase staining. Samples were examined by two independent reviewers and NQO1 staining was graded from 0 (no staining) to 3+ (intense staining). Results. Eleven of 11 melanomas (95% confidence interval, 72% to 100%) and three of three lesions with primary acquired melanosis with atypia stained positively for NQO1. In the melanomas, staining was relatively uniform, while in primary acquired melanosis there was cell-to-cell variability in the staining. Conclusions. NQO1 was detected by immunohistochemistry in every examined section of primary acquired melanosis and melanoma of the conjunctiva, suggesting that NQO1 may play a role in the bioactivation of mitomycin C in these tumors.