Human Tissue Kallikrein Expression in Polymorphous Low Grade Adenocarcinoma

Objectives: Polymorphous low grade adenocarcinoma (PLGA) is the second most common malignant tumor of minor salivary glands. It shows indolent growth and low propensity for metastasis, though delayed recurrence may occur.
Human tissue kallikreins (KLKs) are a family of highly conserved serine proteases encoded by 15 genes and are expressed by various tissue and organ. KLKs have become powerful markers for cancer diagnosis, prognosis and management. KLKs have been shown to be present in salivary gland neoplasms.
We aim to determine levels of KLK mRNA in samples of PLGA. We hypothesize that the expression of KLKs in PLGA is markedly different to normal salivary gland tissue. Altered expression may be used to predict tumor behaviour and has implications for diagnosis and treatment.

Methods: Cases of PLGA were reviewed at the Department of Pathology, Western University from 1987-2013. Demographic data were collected. RNA was isolated from formalin fixed paraffin-embedded PLGA and normal salivary gland tissue samples. Polymerase chain reaction (PCR) was use to quantitate the expression of KLKs 1-15. Samples exhibiting high and low KLK expression were selected for immunohistochemistry staining.

Results: 19 samples of PLGA were obtained. Patient age ranged from 17 to 78 years (mean 68). 64% of patients were female. Tumor sites included palate (64%), buccal mucosa (21%) and lips (14%). RNA isolation yielded 0.32ng of RNA from 16/19 PLGA tissue samples. Mean KLK mRNA expression was increased in all PLGA samples; and KLKs1, 4, 10, 12, and 15 showed statistically significant upregulation (Mann Whitney U test, p<0.05). Immunohistochemistry staining for KLKs will be reported.
Conclusions: KLK mRNA is increased in PLGA. Further interpretation of this preliminary data, along with clinical correlation, is needed to elucidate the role of KLKs as biomarkers for PLGA.