Immunohistochemical expression of mTOR negatively correlates with PTEN expression in gastric carcinoma

The phosphoinositide-3 kinase (PI3K)-AKT-mammalian target of rapamycin (mTOR) pathway is a cellular pathway involved in cell growth, tumorigenesis and cell invasion which is frequently activated in various types of cancer. The downstream effector of the pathway is mTOR which is important in cellular growth and homeostasis and aberrant activation of mTOR has been reported in several types of cancer. The tumor suppressor gene phosphatase and tensin homolog (PTEN) is essential in this pathway for inhibiting tumor invasion and metastasis. However, the involvement of mTOR and PTEN in the progression of human gastric cancer remains to be identified. Immunohistochemical staining was performed to detect the expression of mTOR and PTEN in paraffin-embedded gastric tissue sections obtained from 33 patients with gastric cancer and 30 normal controls. The expressed mTOR was mainly distributed in the cytoplasm, while PTEN was mainly localized to the nucleus. By considering negative mTOR expression with positive PTEN expression as one group and negative PTEN expression with positive mTOR expression as the other, significant statistical differences were observed in various categories, including histological types and metastatic and clinical pathology stages, between the 2 groups (P<0.01 or 0.05). The results indicated that the expression levels of mTOR and PTEN were negatively correlated in the PI3K-AKT-mTOR signaling pathway. Combined detection of mTOR and PTEN expression may be used to evaluate the degree of malignancy in gastric cancer and may be a useful marker for the early diagnosis of gastric cancer.