Analysis of human tissue kallikrein expression in salivary gland tumours

Objectives: Human tissue kallikreins (KLK) constitute a family of 15 serine proteases all of which co-localize to chromosome 19q13.4. Since their discovery, KLKs have been studied as emerging biomarkers for several cancers with increasing evidence for their prognostic value. Recently, kallikrein expression in salivary gland (SG) tumours has been reported by our lab and others1-3. This study aims to show that SG tumours have altered levels of kallikreins that may predict the outcome of disease. Furthermore, levels of KLK panels will be correlated with the outcome of disease, which my lead to the identification of KLKs as novel biomarkers for the detection of SG cancers. We hypothesize that kallikreins have independent diagnostic and prognostic potential for SG carcinomas.

Methods: An immunoperoxidase staining technique was used to semi-quantitatively assess the expression profile and the tumour profile of KLK6, 7, 8, 10, 13 and 14 in normal SG, Pleomorphic Adenoma (PA)(n = 21), Adenoid Cystic Carcinoma (ACC)(n = 17) and Mucoepidermoid Carcinoma (MEC)(n = 15).

Results: The KLK expression profile study showed higher levels of KLK7, 8 and 13 in ACC than in normal glands. Levels of KLK7 and 14 were higher in PA than in normal glands and lower in MEC than PA and ACC. Whereas KLK6 was higher in ACC than PA, only KLK8 showed a higher level in MEC compared to normal glands. There were no significant differences between KLK scores in ACC and MEC; however, PA showed lower levels of KLK6 and 10.

Conclusion: Differences in KLK levels among these tumours suggest that KLKs may aid in the differential diagnosis of SG tumours and may be prognostic indicators in SG cancer. KLKs may be promising new biomarkers for SG tumours, and further studies are needed to quantitatively measure their expression and to correlate with prospective clinical data.