CD8+ T cells have a central role in antitumour immunity, but their activity is suppressed in the tumour microenvironment1–4. Reactivating the cytotoxicity of CD8+ T cells is of great clinical interest in cancer immunotherapy. Here we report a new mechanism by which the antitumour response of mouse CD8+ T cells can be potentiated by modulating cholesterol metabolism. Inhibiting cholesterol esterification in T cells by genetic ablation or pharmacological inhibition of ACAT1, a key cholesterol esterification enzyme5, led to potentiated effector function and enhanced proliferation of CD8+ but not CD4+ T cells. This is due to the increase in the plasma membrane cholesterol level of CD8+ T cells, which causes enhanced T-cell receptor clustering and signalling as well as more efficient formation of the immunological synapse. ACAT1-deficient CD8+ T cells were better than wild-type CD8+ T cells at controlling melanoma growth and metastasis in mice. We used the ACAT inhibitor avasimibe, which was previously tested in clinical trials for treating atherosclerosis and showed a good human safety profile6,7, to treat melanoma in mice and observed a good antitumour effect. A combined therapy of avasimibe plus an anti-PD-1 antibody showed better efficacy than monotherapies in controlling tumour progression. ACAT1, an established target for atherosclerosis, is therefore also a potential target for cancer immunotherapy.

Central tolerance is established through negative selection of self-reactive thymocytes and the induction of T-regulatory cells (T R s). The role of thymic dendritic cells (TDCs) in these processes has not been clearly determined. In this study, we demonstrate that in vivo , TDCs not only play a role in negative selection but in the induction of T R s. TDCs include two conventional dendritic cell (DC) subtypes, CD8 lo Sirpα hi/+ (CD8 lo Sirpα + ) and CD8 hi Sirpα lo/− (CD8 lo Sirpα − ), which have different origins. We found that the CD8 hi Sirpα + DCs represent a conventional DC subset that originates from the blood and migrates into the thymus. Moreover, we show that the CD8 lo Sirpα + DCs demonstrate a superior capacity to induce T R s in vitro . Finally, using a thymic transplantation system, we demonstrate that the DCs in the periphery can migrate into the thymus, where they efficiently induce T R generation and negative selection.

Despite clear epidemiological and genetic evidence for X-linked prostate cancer risk, all prostate cancer genes identified are autosomal. Here we report somatic inactivating mutations and deletion of the X-linked FOXP3 gene residing at Xp11.23 in human prostate cancer. Lineage-specific ablation of FoxP3 in the mouse prostate epithelial cells leads to prostate hyperplasia and prostate intraepithelial neoplasia. In both normal and malignant prostate tissues, FOXP3 is both necessary and sufficient to transcriptionally repress cMYC, the most commonly over-expressed oncogene in prostate cancer as well as among the aggregates of other cancers. FOXP3 is an X-linked prostate tumor suppressor in the male. Since the male has only one X chromosome, our data represents a paradigm of “single-genetic-hit” inactivation-mediated carcinogenesis.

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