Expression of phosphorylated mTOR and its regulatory protein is related to biological behaviors of ameloblastoma.

The present study investigated the relationship between the expression of p-mTOR, p-4EBP1 and p-p70S6K in the cytoplasm and nucleus of ameloblastoma (AB) cells and the invasiveness of ABs. Immunohistochemistry was performed to detect the expression of p-mTOR, p-4EBP1 and p-p70S6K in ABs and the level of these proteins in the nucleus and cytoplasm was scored. There was ectopic expression of p-mTOR in ABs. 27 AB patients were positive for p-mTOR expression in the nucleus and 47 for p-mTOR expression in the cytoplasm. The ectopic expression of p-4EBP-1 was also noted. 23 patients (27%) were positive for p-4EBP-1 expression in the nucleus and 55 (64.7%) for p-4EBP-1 expression in the cytoplasm. The ectopic expression of p-p70S6K was also noted. Of these patients, 33 were positive for p-p70S6K expression in the nucleus (38.8%) and 45 for p-p70S6K expression in the cytoplasm (52.9%). Statistical analysis showed the expression of three proteins in the nucleus of patients with recurrent cancer was markedly higher than that in those with primary cancer. The expression of p-mTOR, p-4E-BP1 and p-p70S6K in the nucleus was related to the invasiveness of ABs. Multivariable analysis with Cox proportional hazards model showed the p-mTOR expression had influence on AB recurrence (OR: 6.417, 95%CI: 1.428-28.824). The possibility of AB recurrence in patients with nuclear p-mTOR expression was 6.417 folds higher than that in those with cytoplasmic p-mTOR expression. The nuclear expression of p-mTOR, p-4E-BP1 and p-p70S6K was associated with biological behaviors (invasiveness) of ABs, and p-mTOR was an independent predictor of AB.