Expression of upstream and downstream targets of mTOR pathway in seven cases of secretory carcinoma of salivary gland origin.

PURPOSE: To investigate the expression of upstream and downstream targets of mTOR signalling pathway in the secretory carcinoma of salivary gland origin (SCsg). METHODS: Seven cases of secretory carcinoma diagnosed by a combination of immunohistochemistry and/or molecular testing were retrieved from our pathology files. For comparison purposes, 27 other salivary carcinomas were selected. Immunohistochemical staining was performed against phospho-Akt, PTEN, phospho-mTOR, phospho-4E-BP, eIF4E and phospho-S6 ribosomal protein. RESULTS: With the exception of Akt, all the other proteins were present at some level in the SCsg and in other salivary carcinomas. PTEN was diffusely expressed in 57.1% of SCsg, but only in 14.8% of other salivary carcinomas. mTOR is expressed in more than half of the cases both for SCsg and other salivary tumour types. Most cases of SCsg showed negative expression for S6 ribosomal protein (71.4%) and 4E-BP1 (57.1%). For both groups evaluated, eIF4E was the most expressed protein. CONCLUSION: SCsg shows different expression patterns for the mTOR signalling molecules, but only eIF4E was highly expressed. This may suggest alternative signalling pathways other than Akt and mTOR in this group of tumours.