PATTERN OF EXPRESSION OF HUMAN HOMOLOGUE OF DROSOPHILA PATCHED1 PROTEIN IN FOUR DIFFERENT SALIVARY GLAND TUMORS

Salivary gland tumors are a comparatively rare and diverse group of tumors with variable clini- cal and histopathological pictures. Pleomorphic adenoma (PA) & papillary cystadenoma lymphato- sum (PCL) are common benign tumors and Mucoepidermoid carcinoma (MEC) & adenoid cystic carcinoma (ACC) are common malignant tumors with the respect of order. The human homologue of the Drosophila segment polarity gene Patched 1 (PTCH 1) is a member of hedgehog pathway encoding a receptor for the morphogen Sonic Hedgehog and it is the candidate gene for Gorlin’s syndrome.  Interestingly it is considered as a one of the tumor a suppressor gene which is associ- ated with different neoplasms and cystic lesions.  In this study the pattern of expression of PTCH1 in PA, PCL, MEC, and ACC tumors will be explored to reveal if there is any possible correlation between PTCH1 expression and these four different salivary gland entities. Twenty paraffin embed- ded blocks of salivary gland tumors was chosen as follow (five cases PA, five cases PCL, five cases MEC (two high grades, two low grades, 1 moderate grade) and five cases ACC (4 cribriform pat- tern, one tubular pattern). immunohistochemistry technique using PTCH 1 primary antibody was done to investigate the level of expression of PTCH 1 protein in our samples. Our results revealed that PTCH1 is expressed with various intensities from light to heavy in the four studied salivary gland tumors. Furthermore, PTCH1 expression was confined to the epithelial cells component of the tumors with cytoplasmic and membranous staining. PCL & MEC (low & moderate grade), ACC (cribriform pattern) cases showed the highest immunoreactivity. While PA, high grade MEC, ACC (tubular pattern) showed the lowest. It can be conclude that PTCH1 might has a role in the development of salivary gland tumors with main components epithelium as PCL, MEC, ACC and to a lesser extent PA as a mixed tumor. Finally, it is recommended that researchers should target SHH pathway genes including PTCH1 in most tumors for further investigations and possible gene therapies