Abstract P5-03-03: Cytotoxic t-lymphocyte density increased within the tumor immune microenvironment of patients with breast cancer following treatment with Akt inhibitor MK-2206

Background: The PAM (PI3K/Akt/mTOR) signaling pathway has been implicated in the oncogenesis of multiple solid malignancies, including breast cancer (BC). Tumor infiltrating lymphocytes (TILs) found within the tumor immune microenvironment (TME) are both prognostic of overall survival as well as predictive of response to neoadjuvant chemotherapy in BC. Our aim is to characterize the TME in a series of patients with operable stage I-III BC treated with MK-2206, an allosteric Akt inhibitor as part of a presurgical, window of opportunity, trial. In our presurgical trial (clinicaltrials.gov #: NCT01319539), patients received 2 doses of MK-2206 with first dose at day -9 and second at day -2 from surgery. Methods: Quantitative multiplex immunofluorescence (qmIF) was performed using immune biomarkers (DAPI, CD3, CD8, CD4, FOXP3, CD68, Pancytokeratin) on full section (4uM) tissue slides from core biopsy specimens and postsurgical specimens of 10 patients - 5 patient treated with MK-2206, and 5 prospectively collected untreated controls. Images were taken using Vectra, a novel pathology workstation and analyzed using inForm software to perform cell classification and phenotyping. Student T- test was used to compare biomarker changes before and after MK-2206. Results: Preliminary analysis demonstrates that patients treated with MK-2206 exhibited a significantly increased median cytotoxic T-cells (CD3CD8+) density, as compared to the matched control cohort (87% vs.0.2%, p Conclusions: In our study, we found that presurgical Akt inhibition lead to a significant increase in the cytotoxic T-cell population which was in similar proximity, if not closer, to tumor cells as compared to matched controls. Limitations of this exploratory study include a small patient cohort size and use of a single pathology evaluation technique. We are currently expanding our characterization of the TME with a more comprehensive myeloid panel as well as performing additional tissue analysis to validate our findings. At present, there are currently FDA approved therapies, as well as agents in clinical development that exert antineoplastic activity through the PAM pathway. Investigations that endeavor to understand the impact of these therapies on the TME may lead to both an increased understanding of the bioactivity of these agents and potentially identify aspects of the immune response which can be exploited by future immunotherapy therapeutics. Citation Format: Marks DK, Gartrell RD, Asmar ME, Hart TD, Lu Y, Esancy CL, Hibshoosh H, Connolly EP, Kalinsky KM, Saenger YM. Cytotoxic t-lymphocyte density increased within the tumor immune microenvironment of patients with breast cancer following treatment with Akt inhibitor MK-2206 [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-03-03.