Expression profiles of mTOR pathway proteins in porocarcinoma: A provisional immunohistochemical study

Porocarcinoma is a rare skin appendage carcinoma, with a poor prognosis. At present, the recommended treatment of localized porocarcinoma is wide surgical resection. Although anthracyclin-based chemotherapy or combination of 5-fluorouracil (5-FU), taxanes and cisplatin are considered to be the first-line treatment for metastatic or locally-advanced porocarcinoma, this type of tumor is recognized as relatively chemoresistant, and no standard systemic treatment has been established yet. Mammalian target of rapamycin (mTOR) is an important protein involved in carcinogenesis. mTOR phosphorylates the eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1), and then phosphorylated 4E-BP1 (p4E-BP1) triggers cell cycle progression, cell proliferation and angiogenesis. Therefore, mTOR is believed to be one of the most promising therapeutic targets in various types of carcinomas. However, the expression profiles of mTOR pathway proteins in porocarcinoma have yet to be elucidated. Therefore, we analyzed the expression of mTOR, 4E-BP1 and p4E-BP1 in five cases of porocarcinoma (four invasive and one in situ case) using immunohistochemical methods. mTOR expression was observed in the invasive porocarcinoma cases, but not in the in situ case. 4E-BP1 was expressed in all five cases. p4E-BP1 expression was observed in 3/4 invasive porocarcinoma cases, but not in the in situ case. This preliminary study clearly demonstrated the overexpression of mTOR and its downstream proteins in most of the included invasive porocarcinoma cases. Therefore, mTOR inhibitors could be considered as potential therapeutic modalities for the treatment of metastatic or locally-advanced porocarcinoma.