Expression of miR-17-92 enhances anti-tumor activity of T-cells transduced with the anti-EGFRvIII chimeric antigen receptor in mice bearing human GBM xenografts

Background: Expression of miR-17-92 enhances T-cell survival and interferon (IFN)-gamma production. We previously reported that miR-17-92 is down-regulated in T-cells derived from glioblastoma (GBM) patients. We hypothesized that transgene-derived co-expression of miR17-92 and chimeric antigen receptor (CAR) in T-cells would improve the efficacy of adoptive transfer therapy against GBM. Methods: We constructed novel lentiviral vectors for miR-17-92 (FG12-EF1a-miR-17/92) and a CAR consisting of an epidermal growth factor receptor variant III (EGFRvIII)-specific, single-chain variable fragment (scFv) coupled to the T-cell receptor CD3 zeta chain signaling module and co-stimulatory motifs of CD137(4-1BB) and CD28 in tandem (pELNS-3C10-CAR). Human T-cells were transduced with these lentiviral vectors, and their anti-tumor effects were evaluated both in vitro and in vivo. Results: CAR-transduced T-cells (CAR-T-cells) exhibited potent, antigen-specific, cytotoxic activity against U87 GBM cells that stably express EGFRvIII (U87-EGFRvIII) and, when co-transduced with miR-17-92, exhibited improved survival in the presence of temozolomide (TMZ) compared with CAR-T-cells without miR-17-92 co-transduction. In mice bearing intracranial U87-EGFRvIII xenografts, CAR-T-cells with or without transgene-derived miR-17-92 expression demonstrated similar levels of therapeutic effect without demonstrating any uncontrolled growth of CAR-T-cells. However, when these mice were re-challenged with U87-EGFRvIII cells in their brains, mice receiving co-transduced CAR-T-cells exhibited improved protection compared with mice treated with CAR-T-cells without miR-17-92 co-transduction. Conclusion: These results warrant the development of novel CAR-T-cell strategies that incorporate miR-17-92 to improve therapeutic potency, especially in patients with GBM.