Expression of Kallikrein-Related Peptidase 6 in Primary Mucosal Malignant Melanoma of the Head and Neck

Mucosal melanomas of the head and neck (MMHN) are aggressive tumors with poor prognosis, different opposed to cutaneous melanoma. In this study, we characterized primary mucosal malignant melanoma for the expression of Kallikrein-related peptidase 6 (KLK6), a member of the KLK family with relevance to the malignant phenotype in various cancer types including cutaneous melanoma. Paraffin-embedded MMHN of 22 patients were stained immunohistochemically for KLK6 and results were correlated with clinical and pathological data. In 77.3% (17/22) of MMHN cases, positive KLK6 staining was found. Staining pattern for tumor cells showed a predominant cytoplasmic staining. However, in six cases we also observed a prominent nuclear staining. MMHN with a high KLK6 expression showed significantly better outcome concerning local recurrence-free survival (p = 0.013) and nuclear KLK6 staining was significantly associated with the survival status (p = 0.027). Overexpression of KLK6 was detected in more than 70% of MMHN and approximately 40% of tumors showed a strong expression pattern. Correlation between clinical outcome of MMHN patients and overexpression of KLK6 has not been addressed so far. Our data demonstrate for the first time increased levels of KLK6 in MMHN and strengthen the hypothesis that there might be a context-specific regulation and function of KLK6 in mucosal melanoma.