Abstract B47: mTOR C1/2 activities - related protein expression and its potential prognostic/therapeutic importance in certain lymphoid malignancies
Authors: Sebestyén Anna , Nagy Noémi , Márk Ágnes , Molnár Anna , Dankó Titanilla , Hajdu Melinda , Tóth Mónika , Timár Botond , Csóka Mónika , Kopper László 
Published: October 2015

There is increasing attention for PI3K/Akt/mTOR pathway as a potential target in tumor therapy. The high activity of mTOR is a characteristic feature of many tumors including hematological malignancies. However, the pathological characterisation of mTOR activity of lymphoid malignancies - especially the activity of different complexes – is still incomplete.

We studied the mTOR activity related phospho-proteins and the elements of mTOR complexes by using different techniques (ELISA, Western blot, different immunohistochemical stainings, flow cytometry) depending on the tumor sample type (fresh/fixed human tissues, isolated human cells from blood or bone marrow, cell lines). The expression and activity results were compared in order to find correlation with clinical data or to mTOR inhibitor sensitivity in vitro. The proliferation and apoptotic effects after in vitro treatments were detected by Alamar Blue assay and flow cytometry. We established the in situ measurement for the amount of mTORC1, C2 complexes by Duolink stainings to compare the effects of different mTOR inhibitors to the mTORC1/C2 complex availability in lymphoma cell cultures.

Our studies described high mTOR activity in all acute lymphoid leukemia (ALL) cases and in the majority of mantle cell lymphomas, anaplastic large cell lymphomas, Burkitt lymphomas, diffuse large B cell lymphomas (DLBCL), Hodgkin lymphomas (HL) and in certain cutan T lymphomas. Further characterisation of HLs, DLBCLs and ALL cases showed that high mTOR activity especially with the presence of mTORC2 is a sign of unfavorable prognosis. mTOR activity related to p-S6 and p-4EBP1 expression (ELISA and flow cytometry) at diagnosis was significantly higher in patients with poor prognosis in ALL cases. In DLBCL patient's the results showed that high mTOR activity with Rictor overexpression significantly correlated to the worse prognosis and shorter survival. We also detected the sign of high mTOR activity in more than 90% of HLs (HLs usually with favorable prognosis), however, in these cases Rictor was not found (the mTOR activity related to mTORC1). In the different lymphoma cell lines increased mTOR activity was detected and we could describe different Rictor, Raptor and mTOR-Rictor complex expression. Moreover, the inhibitor sensitivity of the cell lines and the different expression of the elements related to mTORC1 and C2 correlated.

Our results confirmed the increased mTOR activity related to mTORC1 and/or C2 complexes in certain lymphomas and ALLs. According to these analyses, the activity and expression of mTOR complexes should have potential prognostic value and high importance before mTOR inhibitor treatment, especially in the cases with high mTORC2 related protein expression.

The study was supported by OTKA816624, OTKA 84262 projects and Tumor Progression Research Group of Joint Research Organization of the Hungarian Academy of Sciences and Semmelweis University

Citation Format: Anna Sebestyén, Noémi Nagy, Ágnes Márk, Anna Molnár, Titanilla Dankó, Melinda Hajdu, Mónika Tóth, Botond Timár, Mónika Csóka, László Kopper. mTOR C1/2 activities - related protein expression and its potential prognostic/therapeutic importance in certain lymphoid malignancies. [abstract]. In: Proceedings of the AACR Special Conference: Targeting the PI3K-mTOR Network in Cancer; Sep 14-17, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(7 Suppl):Abstract nr B47.