The immune checkpoint receptor PD-1 on T follicular helper (Tfh) cells promotes Tfh:B cell interactions and appropriate positioning within tissues. Here we examined the impact of regulation of PD-1 expression by the genomic organizer SATB1 on Tfh cell differentiation. Vaccination of CD4^CreSatb1^f/f mice enriched for antigen-specific Tfh cells, and TGF-β-mediated repression of SATB1 enhanced Tfh differentiation of human T cells. Mechanistically, high Icos expression in Satb1^−/− CD4⁺ T cells promoted Tfh cell differentiation by preventing T follicular regulatory cell skewing, and resulted in increased isotype-switched B cell responses in vivo. Ovarian tumors in CD4^CreSatb1^f/f mice accumulated tumor antigen-specific, LIGHT⁺CXCL13⁺IL-21⁺ Tfh cells and tertiary lymphoid structures (TLS). TLS formation decreased tumor growth in a CD4⁺ T cell and CXCL13-dependent manner. Transfer of Tfh cells, but not naïve CD4⁺ T cells, induced TLS at tumor beds and decreased tumor growth. Thus, TGF-β-mediated silencing of Satb1 licenses Tfh cell differentiation, providing insight into the genesis of TLS within tumors.

Despite repeated associations between T-cell infiltration and outcome, human ovarian cancer remains poorly responsive to immunotherapy. We report that hallmarks of tumor recognition in ovarian cancer-infiltrating T-cells are primarily restricted to tissue-resident memory (TRM) cells. Single-cell RNA/TCR/ATAC sequencing of 83,454 CD3⁺CD8⁺CD103⁺CD69⁺ TRM cells and immunohistochemistry of 122 high-grade serous ovarian cancers shows that only progenitor (TCF1^low) tissue-resident T-cells (TRM_stem cells), but not re-circulating TCF1⁺ T-cells, predict ovarian cancer outcome. TRM_stem cells arise from transitional re-circulating T-cells, which depends on antigen affinity/persistence, resulting in oligoclonal, trogocytic, effector lymphocytes that eventually become exhausted. Therefore, ovarian cancer is indeed an immunogenic disease, but that depends on ~13% of CD8⁺ tumor-infiltrating T-cells (~3% of CD8⁺ clonotypes), which are primed against high-affinity antigens and maintain waves of effector TRM-like cells. Our results define the signature of relevant tumor-reactive T cells in human ovarian cancer, which could be applicable to other tumors with unideal mutational burden.

The role of estrogens in antitumor immunity remains poorly understood. Here, we show that estrogen signaling accelerates the progression of different estrogen-insensitive tumor models by contributing to deregulated myelopoiesis by both driving the mobilization of myeloid-derived suppressor cells (MDSC) and enhancing their intrinsic immunosuppressive activity in vivo. Differences in tumor growth are dependent on blunted antitumor immunity and, correspondingly, disappear in immunodeficient hosts and upon MDSC depletion. Mechanistically, estrogen receptor alpha activates the STAT3 pathway in human and mouse bone marrow myeloid precursors by enhancing JAK2 and SRC activity. Therefore, estrogen signaling is a crucial mechanism underlying pathologic myelopoiesis in cancer. Our work suggests that new antiestrogen drugs that have no agonistic effects may have benefits in a wide range of cancers, independently of the expression of estrogen receptors in tumor cells, and may synergize with immunotherapies to significantly extend survival. Significance: Ablating estrogenic activity delays malignant progression independently of the tumor cell responsiveness, owing to a decrease in the mobilization and immunosuppressive activity of MDSCs, which boosts T-cell–dependent antitumor immunity. Our results provide a mechanistic rationale to block estrogen signaling with newer antagonists to boost the effectiveness of anticancer immunotherapies. Cancer Discov; 7(1); 72–85. ©2016 AACR. See related commentary by Welte et al., p. 17. This article is highlighted in the In This Issue feature, p. 1

BTN3A1 governs antitumor responses: T lymphocytes are immune cells that can be activated through their gamma delta (γδ) or alpha beta (αβ) receptors. Both T cell types are found in human cancers, but current immunotherapies do not harness their coordinated antitumor activity. Payne et al. found that BTN3A1 and BTN2A1, two members of the butyrophilin family of proteins, partner to activate the most abundant subset of γδ T cells in peripheral blood. Antibodies targeting BTN3A1 redirect γδ T cells to attack cancer cells while also increasing the activity of tumor-specific αβ T cells. Thus, the killing of established tumors by different T cell subsets can be achieved through BTN3A1 targeting and may provide new strategies for cancer immunotherapy. Science , this issue p. 942

Purpose: To define the safety and effectiveness of T cells redirected against follicle-stimulating hormone receptor (FSHR)-expressing ovarian cancer cells. Experimental Design: FSHR expression was determined by Western blotting, immunohistochemistry, and qPCR in 77 human ovarian cancer specimens from 6 different histologic subtypes and 20 human healthy tissues. The effectiveness of human T cells targeted with full-length FSH in vivo was determined against a panel of patient-derived xenografts. Safety and effectiveness were confirmed in immunocompetent tumor-bearing mice, using constructs targeting murine FSHR and syngeneic T cells. Results: FSHR is expressed in gynecologic malignancies of different histologic types but not in nonovarian healthy tissues. Accordingly, T cells expressing full-length FSHR-redirected chimeric receptors mediate significant therapeutic effects (including tumor rejection) against a panel of patient-derived tumors in vivo. In immunocompetent mice growing syngeneic, orthotopic, and aggressive ovarian tumors, fully murine FSHR-targeted T cells also increased survival without any measurable toxicity. Notably, chimeric receptors enhanced the ability of endogenous tumor-reactive T cells to abrogate malignant progression upon adoptive transfer into naïve recipients subsequently challenged with the same tumor. Interestingly, FSHR-targeted T cells persisted as memory lymphocytes without noticeable PD-1–dependent exhaustion during end-stage disease, in the absence of tumor cell immunoediting. However, exosomes in advanced tumor ascites diverted the effector activity of this and other chimeric receptor–transduced T cells away from targeted tumor cells. Conclusions: T cells redirected against FSHR⁺ tumor cells with full-length FSH represent a promising therapeutic alternative against a broad range of ovarian malignancies, with negligible toxicity even in the presence of cognate targets in tumor-free ovaries. Clin Cancer Res; 23(2); 441–53. ©2016 AACR.