Prognostic significance of AKT/mTOR signaling in advanced neuroendocrine tumors treated with somatostatin analogs
I Fernandes, TR Pacheco, A Costa… - OncoTargets and …, 2012 - Taylor & Francis
OncoTargets and therapy, 2012•Taylor & Francis
Introduction: Somatostatin analogs (SSAs) are used as part of standard treatment for
advanced neuroendocrine tumors (NETs). The mechanisms behind the antiproliferative
action of SSAs remain largely unknown, but a connection with the mammalian target of
rapamycin (mTOR) signaling pathway has been suggested. Our purpose was to evaluate
the activation status of the AKT/mTOR pathway in advanced metastatic NETs and identify
biomarkers of response to SSA therapy. Patients and methods: Expression of phosphatase …
advanced neuroendocrine tumors (NETs). The mechanisms behind the antiproliferative
action of SSAs remain largely unknown, but a connection with the mammalian target of
rapamycin (mTOR) signaling pathway has been suggested. Our purpose was to evaluate
the activation status of the AKT/mTOR pathway in advanced metastatic NETs and identify
biomarkers of response to SSA therapy. Patients and methods: Expression of phosphatase …
Introduction
Somatostatin analogs (SSAs) are used as part of standard treatment for advanced neuroendocrine tumors (NETs). The mechanisms behind the antiproliferative action of SSAs remain largely unknown, but a connection with the mammalian target of rapamycin (mTOR) signaling pathway has been suggested. Our purpose was to evaluate the activation status of the AKT/mTOR pathway in advanced metastatic NETs and identify biomarkers of response to SSA therapy.
Patients and methods
Expression of phosphatase and tensin homolog (PTEN), phosphorylated (p)-AKT(Ser473), and p-S6(Ser240/244) was evaluated using immunohistochemistry in archival paraffin samples from 23 patients. Expression levels were correlated with clinicopathological parameters and progression-free survival under treatment with SSAs.
Results
A positive association between p-AKT and p-S6 expression was identified (P = 0.01) and higher expression of both markers was observed in pancreatic NETs. AKT/mTOR activation was observed without the loss of PTEN expression. Tumors showing AKT/mTOR signaling activation progressed faster when treated with SSAs: higher expression of p-AKT or p-S6 predicted a median progression-free survival of 1 month vs 26.5 months for lower expression (P = 0.02).
Conclusion
Constitutive activation of the AKT/mTOR pathway was associated with shorter time-to-progression in patients undergoing treatment with SSAs. Larger case series are needed to validate whether p-AKT(Ser473) and p-S6(Ser240/244) can be used as prognostic markers of response to therapy with SSAs.
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