560 Alpha-tocopheryloxyacetic acid induces apoptosis of murine rhabdomyosarcoma in vitro while modulating innate and adaptive immune responses in vivo

BackgroundRelapsed pediatric sarcomas have a poor prognosis with no available curative options. Alpha-Tocopheryloxyacetic acid (a-TEA) is a redox-silent analog of alpha-tocopherol that induces apoptotic and immunogenic cell death of tumor cells at doses that are not harmful to healthy normal cells. In a first-in-human clinical trial, a-TEA was well tolerated in adults with advanced solid tumors (NCT02192346), but has not yet been studied in pediatric sarcoma. We used a murine model of rhabdomyosarcoma (M3-9-M RMS) to assess the in vitro and in vivo anti-tumor effects of a-TEA.MethodsIn vitro studies were performed on the M3-9-M RMS cell line to measure a-TEA-mediated apoptosis using flow cytometry (Annexin V+/7AAD+ cells) and live cell imaging (Annexin V+ cells). In vivo studies involved orthotopic implantation of luciferase+ M3-9-M tumor cells into syngeneic C57BL/6 recipients. Once tumors were palpable, mice were randomized to a control diet or a-TEA-supplemented chow for 21 days and evaluated for bioluminescence, tumor growth and overall survival. Gene expression of tumor-infiltrating and splenic T cells were analyzed by bulk RNA-Seq and flow cytometry respectively.ResultsM3-9-M RMS treatment with 2.5–100 uM a-TEA induced apoptosis in a dose-dependent manner within 24 hours (p < 0.05) as measured by flow cytometry and live cell imaging. In-vivo studies with the M3-9-M RMS mouse model showed that recipients of a-TEA chow had 30–40% reduced tumor growth (p