Zheng Liu

Although tumor-intrinsic fatty acid β-oxidation (FAO) is implicated in multiple aspects of tumorigenesis and progression, the impact of this metabolic pathway on cancer cell susceptibility to immunotherapy remains unknown. Here, we report that cytotoxicity of killer T cells induces activation of FAO and upregulation of carnitine palmitoyltransferase 1A (CPT1A), the rate-limiting enzyme of FAO in cancer cells. The repression of CPT1A activity or expression renders cancer cells more susceptible to destruction by cytotoxic T lymphocytes. Our mechanistic studies reveal that FAO deficiency abrogates the prosurvival signaling in cancer cells under immune cytolytic stress. Furthermore, we identify T cell–derived IFN-γ as a major factor responsible for induction of CPT1A and FAO in an AMPK-dependent manner, indicating a dynamic interplay between immune effector cells and tumor targets. While cancer growth in the absence of CPT1A remains largely unaffected, established tumors upon FAO inhibition become significantly more responsive to cellular immunotherapies including chimeric antigen receptor-engineered human T cells. Together, these findings uncover a mode of cancer resistance and immune editing that can facilitate immune escape and limit the benefits of immunotherapies.

Antigen-specific immunotherapy can be limited by induced tumor immunoediting (e.g., antigen loss) or through failure to recognize antigen-negative tumor clones. Melanoma differentiation–associated gene-7/IL24 (MDA-7/IL24) has profound tumor-specific cytotoxic effects in a broad spectrum of cancers. Here we report the enhanced therapeutic impact of genetically engineering mouse tumor-reactive or antigen-specific T cells to produce human MDA-7/IL24. While mock-transduced T cells only killed antigen-expressing tumor cells, MDA-7/IL24-producing T cells destroyed both antigen-positive and negative cancer targets. MDA-7/IL24-expressing T cells were superior to their mock-engineered counterparts in suppressing mouse prostate cancer and melanoma growth as well as metastasis. This enhanced antitumor potency correlated with increased tumor infiltration and expansion of antigen-specific T cells as well as induction of a Th1-skewed immunostimulatory tumor environment. MDA-7/IL24-potentiated T-cell expansion was dependent on T-cell–intrinsic STAT3 signaling. Finally, MDA-7/IL24-modified T-cell therapy significantly inhibited progression of spontaneous prostate cancers in Hi-Myc transgenic mice. Taken together, arming T cells with tumoricidal and immune-potentiating MDA-7/IL24 confers new capabilities of eradicating antigen-negative cancer cell clones and improving T-cell expansion within tumors. This promising approach may be used to optimize cellular immunotherapy for treating heterogeneous solid cancers and provides a mechanism for inhibiting tumor escape.Significance:This research describes a novel strategy to overcome the antigenic heterogeneity of solid cancers and prevent tumor escape by engineering T lymphocytes to produce a broad-spectrum tumoricidal agent.

Supplementary Figure S1. Characterization of tumor-sensitized T cells expanded with y-chain cytokines.

Supplementary Figure S5. Alterations of tumor immune environment by MDA-7-producing T cells.

Supplementary Figure S6. Effects of MDA-7 engineering on phenotype, activation, and expansion of T cells.

Supplementary Figure S5. Alterations of tumor immune environment by MDA-7-producing T cells.

Supplementary Figure S2. Schematic depiction of construction of human MDA-7/IL-24-encoding lentivirus (LV-MDA-7) and engineering of T cells.

Supplementary Figure S8. Upregulation of endogenous MDA-7 in mouse cancer cells is not caused by human MDA-7 produced by engineered T cells.

Supplementary Figure S4. MDA-7/IL-24 engineering confers T cells with improved therapeutic activity in eradication of prostate cancer.