CAR T cells targeting Olfactory Receptor OR2H1 are an effective immunotherapeutic option in human epithelial tumors

Chimeric antigen receptor (CAR) T cells have been successful for hematological malignancies, but so far showed limited efficiency against solid tumors. Olfactory receptors are expressed in a variety of epithelial cancers, with a limited expression in healthy tissues. We quantified olfactory receptor OR2H1 expression in ovarian cancer, non-small cell lung cancer (NSCLC), breast cancer, and many normal tissues, and we found OR2H1 is expressed in multiple solid epithelial tumors but limited to testis among healthy human tissues. CAR T cells targeting OR2H1-extracellular domain were generated, and OR2H1-specific cytotoxic killing was confirmed, both in vitro and in vivo. Correspondingly, OR2H1-CAR T cells mediate significant therapeutic effects against OR2H1+ NSCLC and high-grade serous ovarian cancer. Interestingly, OR2H1 ablation significantly delays malignant progression of at least NSCLC, but OR2H1 expression is found to be essential for the cytotoxic effects of the OR2H1-CAR T cells. In summary, T cells directed against OR2H1-expressing tumor cells could be a potential therapeutic approach in future for treating OR2H1-expressing cancers.

Supported by CA076292, R01CA157664, R01CA124515, R01CA178687, R01CA211913, U01CA232758 

Ovarian cancer immunogenicity is governed by a narrow subset of progenitor tissue-resident memory T-cells

Despite repeated associations between T-cell infiltration and patient 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. In mouse models we found that TRM T-cells were better than the re-circulating counterpart at controlling tumor growth. Single-cell RNA/TCR/ATAC sequencing of 83,454 CD3+CD8+CD103+CD69+ TRM cells and 24,175 CD3+CD8+CD103− re-circulating TILs showed that progenitor (TCF1low) tissue-resident memory T-cells (TRMstem cells) arise from transitional recirculating T-cells, which depends on antigen affinity/persistence, resulting in oligoclonal, trogocytic, effector lymphocytes. This effector population develops into proliferative lymphocytes that eventually become exhausted TRMs. Immunohistochemistry of 122 high-grade serous ovarian cancer tissues showed that only TRMstem cells, but not re-circulating TCF1+ T-cells, predict ovarian cancer outcome. Therefore, ovarian cancer is indeed an immunogenic disease 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 cells.

Support for Shared Resources was provided by Cancer Center Support Grant (CCSG) CA076292 to H. Lee Moffitt Cancer Center and by CCSG CA010815 to The Wistar Institute. This study was supported by grants from NIH (R01CA157664, R01CA124515, R01CA178687, R01CA211913 and U01CA232758 to JRCG; R01CA184185 and RO1CA262121 to PCR.)

Immune pressure against ovarian cancer depends on antigen-specific CD69+CD103+TRM T cells

The relationship between stem-like, tissue resident memory (TRM) and exhausted T cells at tumor beds is incompletely understood. We found that more than 50% of the CD8+ T cells in human ovarian carcinomas are TRM cells. RNA seq of TRM and their re-circulating counterparts infiltrating multiple human ovarian carcinomas showed a very distinctive phenotype, characterized by co-upregulation of effector and exhaustion markers, along with increased clonality and marked proliferative and lipid metabolism signatures. Interestingly, both populations showed very little overlap in TCR repertoire. Single cell analysis of TRM population showed that this is a heterogeneous population composed of different clusters defined by gene expression and TCR repertoire. A distinctive cluster shows higher expression of cytotoxic mediators and exhaustion markers, along with higher clonality and higher proliferation rate, with a TCR repertoire shared by CD103+TCF7+ stem-like cells. Single cell ATACseq showed that TRM and their counterpart have different chromatin structure and, within both populations also appear variables epigenetic landscapes. In addition, the presence of TRM is correlated with better prognosis, while tumor antigen-specific TRM T cells transferred into syngeneic tumor-bearing mice were more effective at delaying tumor growth than their tumor antigen-specific re-circulating counterparts. Together, our data indicate that productive immune pressure against malignant progression depends on a subset of CD8+ stem-like T cells differentiating into a narrow cluster of TRM T cells of ~300 TCR clones, which represent true tumor antigen-specific effector lymphocytes.

Satb1 deficiency licenses TFH-differentiation and Tertiary Lymphoid Structure formation in cancer

Tertiary Lymphoid Structures (TLS) are commonly identified in human tumors with improved outcome, but how they are orchestrated remains elusive. Here we show that silencing of the master genomic organizer Satb1 results in enhanced antigen-specific T Follicular Helper (TFH) differentiation. Increased TFH thereby promoted antigen-specific intra-tumoral CD19+B220+ B cell responses and spontaneous TLS assembly upon ovarian tumor challenge. Mechanistically, Satb1 deficiency drives increased TFH formation through de-repression of ICOS and PD-1. Accordingly, TGF-β1-driven downregulation of Satb1 licenses activated human CD4+ T-cells for enhanced antigen-specific T Follicular Helper (TFH) differentiation. Furthermore, Satb1 deficiency abrogates the generation of PD-1highCXCR5+Foxp3+ T Follicular Regulatory (TFR) cells during the TFH differentiation process. Importantly, functional TFH cell accumulation, in the absence of Satb1 specifically in CD4+ T cells, resulted in corresponding isotype-switched B cell responses and spontaneous formation of TLS, while B cell depletion accelerated malignant progression. Our results indicate that the formation of TLS in cancer depends on enhanced B cell responses driven by TFH cells generated through Satb1 down-regulation.

SATB1 as a novel therapeutic target for methyltransferase inhibitors against Cutaneous T Cell Lymphoma

Cutaneous T cell lymphoma (CTCL) is a clinically unmet need. Using conditional knockout mice, we found that ablation of the genomic organizer Special AT rich sequence binding protein 1 (Satb1) induces a progressively fatal lymphoma characterized by mature, skin homing, Notch activated CD4 and CD8 T cells. Mechanistically, Satb1 restrains Stat5 phosphorylation and the expression of skin homing chemokine receptors in mature T cells. Notably, SUV39H1 and 2 methyltransferase dependent epigenetic repression of SATB1 is universally found in human Sezary Syndrome, but not other peripheral T cell malignancies. Accordingly, H3K27 and H3K9 trimethylation occlude the SATB1 promoter in Sezary cells. Inhibition of SUV39H1 and 2 methyltransferases with novel drugs, unlike EZH2 inhibition, restores SATB1 expression, selectively abrogating the growth of primary Sezary cells more effectively than Romidepsin. Therefore, SATB1 acts as a tumor suppressor in mature T cells upon NOTCH1 deregulation, and inhibition of methyltransferases that silence SATB1 could address an unmet need for patients with mycosis fungoides and Sezary syndrome.

Immune pressure against ovarian cancer depends on antigen-specific TRM T cells

Conventional memory T cells classically include central memory T (TCM) cells, residing in lymphoid organs, and effector memory T (TEM) cells, circulating through various tissues. Recently, a novel population of memory T cells has gained interest, namely tissue resident memory T (TRM) cells, which persist in tissues and do not recirculate. It is described that these cells reside in human tumors playing a role in tumor-specific T-cell responses. We found by flow cytometry that between 50%–80% of the CD8+ T cells in human ovarian carcinomas are CD103+CD69+TRM cells. RNA-seq of TRM and their re-circulating counterparts from 7 different human carcinomas showed a very distinctive phenotype, characterized by co-upregulation of effector (GZMB, IFNG) and exhaustion (PD-1, TIM3) markers, along with transcription factors and signaling molecules likely involved in the acquisition of the TRM phenotype. Unexpectedly, we found very little overlap between the TCR repertoire of both populations in multiple tumors, and TRM T cells consistently showed significantly higher clonality. Tumor antigen-specific TRM T cells intratumorally transferred into syngeneic mice were more effective at delaying tumor growth compared with their tumor antigen-specific recirculating counterparts. Finally, both the acquisition and the maintenance of a TRM phenotype within the CD8 T cell compartment at tumor beds are dependent on exposure to tumor cognate antigen. Together, our data indicate that TRM CD8+ T cells, but not their CD103− counterparts, represent tumor antigen-specific effector lymphocytes actively exerting anti-tumor immune pressure in the ovarian cancer microenvironment.

Butyrophilin 3A1 is a Dynamic T Cell Regulator in Ovarian Cancer

Ovarian carcinoma microenvironmental T cells exert clinically relevant pressure against malignant progression; however current immunotherapies rarely induce ovarian cancer regression. Here we investigate CD277-containing butyrophilin 3A1 (BTN3A1), a poorly investigated immunoregulatory pathway driven by myeloid and tumor cells in ovarian tumor beds. We show that BTN3A1 is overexpressed in ovarian cancer and is associated with a significant survival disadvantage in these patients (n=200). Concomitantly, ectopic expression of BTN3A1 on APCs inhibits αβ T cell proliferation and Th1 cytokine production. Proteomic analyses and binding assays demonstrate that BTN3A1 interacts with the CD45 phosphatase and elements of the TCR. Consequently, TCR ligation in the presence of BTN3A1 inhibits the segregation of CD45 from the immune synapse and blunts downstream signaling by antagonizing the phosphorylation of CD3Zeta, Lck, and Zap70. We developed fully human αCD277 antibodies which rescue αβ T cell proliferation and Th1 cytokine responses, while driving the infiltration of T cells into tumor beds, delaying ovarian tumor progression in novel BTN3A1+ humanized mice and xenograft studies. Paradoxically, αCD277 antibodies promote the activation of γδ T cells by driving a conformational transformation of BTN3A1. Thus, co-transfer of γδ and Ag-specific αβ T cells in the presence of αCD277 antibodies synergize to further impair malignant progression in vivo. Overall, we show that BTN3A1 drives αβ T cell dysfunction in ovarian cancer, while αCD277 antibodies transform this molecule from immunosuppressive to immunostimulatory by rescuing αβ T cells and activating γδ T cells, thus dynamically unleashing T cell-driven antitumor immunity.

Mesenchymal stem cells educate breast tumor associated macrophages to acquire increased immunosuppressive features

Breast cancer metastasis is known to be extensively promoted by immunosuppression. Here we describe a novel mechanism by which mesenchymal stem cell (MSC)-derived exosomes drive an immunosuppressive program within the breast tumor microenvironment. Initial q-PCR and immunophenotyping of human breast tumor samples, and TCGA data analysis confirmed a positive correlation between infiltrations of MSC and M2 macrophage phenotype, therefore we hypothesized that MSC promote M2 macrophage differentiation in breast tumors. We then performed a series of experiments in vitro and in vivo, and found that MSC-derived exosomes significantly promote differentiation of macrophages into PD-L1 expressing ‘M2-like’ phenotype, while also enhancing malignant progression of breast tumors, in vivo. Additionally, we observed increased invasive potential of tumor cells with higher expression of mesenchymal markers when induced with MSC-derived exosomes. Importantly, our observation of a significantly higher TGF-β production by tumor associated macrophages in exosome-induced tumors, with stronger PD-1 expression by intra-tumoral T cells, suggests TGF-β driven PD-1 upregulation. Blocking of PD-L1 abrogates exosome-induced tumor growth signifying the PD-L1/PD-1 checkpoint pathway is vital to MSC-induced tumor progression. Together, infiltration of MSCs within breast tumors drives the increased invasive potential as well as immune-checkpoint-mediated immunosuppression through inducing PD-L1 expression by tumor associated macrophages and PD-1 expression by T cells. Targeting infiltration of MSCs into the breast tumor therefore is a potential approach to reduce breast tumor metastases and improve efficacy of immunotherapies.

Satb1 deficiency licenses TFH-differentiation

T Follicular Helper cells (TFH) provide both co-stimulation and stimulatory cytokines to B cells to facilitate affinity maturation, class switch recombination, and plasma cell differentiation within the germinal center. However, is not clear how TFH differentiation is regulated. We found that deficiency of the chromatin organizer Satb1 results in increased TFH formation in CD4Cre+Satb1flx/flx mice through up-regulation of the canonical TFH markers ICOS and PD-1 and suppression of Foxp3+PD-1highCXCR5+ T follicular regulatory (TFR) cells as well. Accordingly, CD4Cre+Satb1flx/flx mice, or RAG1−/− mice transferred with Satb1-deficient CD4+ T cells showed a dramatic accumulation of CD4+CXCR5+PD-1high upon ovarian tumor challenge, compared to their Satb1+ counterparts, which was associated with reduced tumor growth. Importantly, intratumoral administration of Satb1-deficient CD4+ T cells re-directed to target ovarian cancer cells through chimeric receptors, but not their Satb1+ counterparts, induce the formation of Tertiary Lymphoid Structures in most tumors.

Conclusion

Satb1 controls three mechanisms relevant for TFH differentiation and, subsequently, antigen-specific humoral responses; namely, PD- 1 expression, ICOS de-repression and TFR formation. Our results suggest a novel role for Satb1 as a major regulator of TFH differentiation and TLS during tumor formation.