Over-expression of phosphorylated mammalian target of rapamycin is associated with poor survival in oesophageal adenocarcinoma: a tissue microarray study

BACKGROUND: Protein kinase mammalian target of rapamycin (mTOR) is an important downstream effector of the phosphatidylinositol 3-kinase (PI3K)/Akt signalling pathway. In several tumour types, phosphorylated mTOR (p-mTOR) over-expression is an independent prognostic marker for poor survival. However, p-mTOR expression has not been assessed in oesophageal adenocarcinoma (OAC).

MATERIALS AND METHODS: Tumour cores of 154 patients with OAC were included in a tissue microarray (TMA). Scoring criteria were based on p-mTOR staining intensity.

RESULTS: 147 (95.5%) patients were available for immunohistochemical evaluation. Over-expression of p-mTOR was detected in 29 (19.7%) tumours, whereas 118 (80.3%) patients showed negative expression. Over-expression was significantly associated with poor overall survival in univariate analysis (HR 1.648; 95% CI 1.019 to 2.664; p=0.042). Median survival was 21.2 months in patients with p-mTOR over-expression and 29.0 in the negative p-mTOR group (p=0.040). In addition, a trend towards p-mTOR over-expression and vasoinvasive growth was seen (p=0.057). In multivariate analysis, including clinical and pathological variables (p<0.10), only T-stage (HR 2.795; 95% CI 1.343 to 5.813; p=0.006) and differentiation grade (HR 2.198; 95% CI 1.353 to 3.570; p=0.001) were independent prognostic markers of poor survival.

CONCLUSION: p-mTOR over-expression was detected in 19.7% of patients with OAC and was associated with poor overall survival.