Targeting intracellular oncoproteins with dimeric IgA promotes expulsion from the cytoplasm and immune-mediated control of epithelial cancers

Dimeric IgA (dIgA) can move through cells via the IgA/IgM polymeric immunoglobulin receptor (PIGR), which is expressed mainly on mucosal epithelia. Here, we studied the ability of dIgA to target commonly mutated cytoplasmic oncodrivers. Mutation-specific dIgA, but not IgG, neutralized KRASG12D within ovarian carcinoma cells and expelled this oncodriver from tumor cells. dIgA binding changed endosomal trafficking of KRASG12D from accumulation in recycling endosomes to aggregation in the early/late endosomes through which dIgA transcytoses. dIgA targeting of KRASG12D abrogated tumor cell proliferation in cell culture assays. In vivo, KRASG12D-specific dIgA1 limited the growth of KRASG12D-mutated ovarian and lung carcinomas in a manner dependent on CD8+ T cells. dIgA specific for IDH1R132H reduced colon cancer growth, demonstrating effective targeting of a cytoplasmic oncodriver not associated with surface receptors. dIgA targeting of KRASG12D restricted tumor growth more effectively than small-molecule KRASG12D inhibitors, supporting the potential of this approach for the treatment of human cancers.

Considerations and Approaches for Cancer Immunotherapy in the Aging Host

Advances in cancer immunotherapy are improving treatment successes in many distinct cancer types. Nonetheless, most tumors fail to respond. Age is the biggest risk for most cancers, and the median population age is rising worldwide. Advancing age is associated with manifold alterations in immune cell types, abundance, and functions, rather than simple declines in these metrics, the consequences of which remain incompletely defined. Our understanding of the effects of host age on immunotherapy mechanisms, efficacy, and adverse events remains incomplete. A deeper understanding of age effects in all these areas is required. Most cancer immunotherapy preclinical studies examine young subjects and fail to assess age contributions, a remarkable deficit given the known importance of age effects on immune cells and factors mediating cancer immune surveillance and immunotherapy efficacy. Notably, some cancer immunotherapies are more effective in aged versus young hosts, while others fail despite efficacy in the young. Here, we review our current understanding of age effects on immunity and associated nonimmune cells, the tumor microenvironment, cancer immunotherapy, and related adverse effects. We highlight important knowledge gaps and suggest areas for deeper enquiries, including in cancer immune surveillance, treatment response, adverse event outcomes, and their mitigation.

Crucial roles of the BRCA1-BARD1 E3 ubiquitin ligase activity in homology-directed DNA repair

The tumor-suppressor breast cancer 1 (BRCA1) in complex with BRCA1-associated really interesting new gene (RING) domain 1 (BARD1) is a RING-type ubiquitin E3 ligase that modifies nucleosomal histone and other substrates. The importance of BRCA1-BARD1 E3 activity in tumor suppression remains highly controversial, mainly stemming from studying mutant ligase-deficient BRCA1-BARD1 species that we show here still retain significant ligase activity. Using full-length BRCA1-BARD1, we establish robust BRCA1-BARD1-mediated ubiquitylation with specificity, uncover multiple modes of activity modulation, and construct a truly ligase-null variant and a variant specifically impaired in targeting nucleosomal histones. Cells expressing either of these BRCA1-BARD1 separation-of-function alleles are hypersensitive to DNA-damaging agents. Furthermore, we demonstrate that BRCA1-BARD1 ligase is not only required for DNA resection during homology-directed repair (HDR) but also contributes to later stages for HDR completion. Altogether, our findings reveal crucial, previously unrecognized roles of BRCA1-BARD1 ligase activity in genome repair via HDR, settle prior controversies regarding BRCA1-BARD1 ligase functions, and catalyze new efforts to uncover substrates related to tumor suppression.

The complementarity of DDR, nucleic acids and anti-tumour immunity

Immune checkpoint blockade (ICB) immunotherapy is a first-line treatment for selected cancers, yet the mechanisms of its efficacy remain incompletely understood. Furthermore, only a minority of patients with cancer benefit from ICB, and there is a lack of fully informative treatment response biomarkers. Selectively exploiting defects in DNA damage repair is also a standard treatment for cancer, spurred by enhanced understanding of the DNA damage response (DDR). DDR and ICB are closely linked-faulty DDR produces immunogenic cancer neoantigens that can increase the efficacy of ICB therapy, and tumour mutational burden is a good but imperfect biomarker for the response to ICB. DDR studies in ICB efficacy initially focused on contributions to neoantigen burden. However, a growing body of evidence suggests that ICB efficacy is complicated by the immunogenic effects of nucleic acids generated from exogenous DNA damage or endogenous processes such as DNA replication. Chemotherapy, radiation, or selective DDR inhibitors (such as PARP inhibitors) can generate aberrant nucleic acids to induce tumour immunogenicity independently of neoantigens. Independent of their functions in immunity, targets of immunotherapy such as cyclic GMP-AMP synthase (cGAS) or PD-L1 can crosstalk with DDR or the DNA repair machinery to influence the response to DNA-damaging agents. Here we review the rapidly evolving, multifaceted interfaces between DDR, nucleic acid immunogenicity and immunotherapy efficacy, focusing on ICB. Understanding these interrelated processes could explain ICB treatment failures and reveal novel exploitable therapeutic vulnerabilities in cancers. We conclude by addressing major unanswered questions and new research directions.

Selective delipidation of Mycobacterium bovis BCG retains antitumor efficacy against non-muscle invasive bladder cancer

PURPOSE

Repeated instillations of bacillus Calmette et Guérin (BCG) are the gold standard immunotherapeutic treatment for reducing recurrence for patients with high-grade papillary non-muscle invasive bladder cancer (NMIBC) and for eradicating bladder carcinoma-in situ. Unfortunately, some patients are unable to tolerate BCG due to treatment-associated toxicity and bladder removal is sometimes performed for BCG-intolerance. Prior studies suggest that selectively delipidated BCG (dBCG) improves tolerability of intrapulmonary delivery reducing tissue damage and increasing efficacy in preventing Mycobacterium tuberculosis infection in mice. To address the lack of treatment options for NMIBC with BCG-intolerance, we examined if selective delipidation would compromise BCG's antitumor efficacy and at the same time increase tolerability to the treatment.

MATERIALS AND METHODS

Murine syngeneic MB49 bladder cancer models and in vitro human innate effector cell cytotoxicity assays were used to evaluate efficacy and immune impact of selective delipidation in Tokyo and TICE BCG strains.

RESULTS

Both dBCG-Tokyo and dBCG-TICE effectively treated subcutaneous MB49 tumors in mice and enhanced tumor-infiltrating CD8+ T and natural killer cells, similar to conventional BCG. However, when compared to conventional BCG, only dBCG-Tokyo retained a significant effect on intratumoral tumor-specific CD8+ and γδ T cells by increasing their frequencies in tumor tissue and their production of antitumoral function-related cytokines, i.e., IFN-γ and granzyme B. Further, dBCG-Tokyo but not dBCG-TICE enhanced the function and cytotoxicity of innate effector cells against human bladder cancer T24 in vitro.

CONCLUSIONS

These data support clinical investigation of dBCG-Tokyo as a treatment for patients with BCG-intolerant NMIBC.

Belly Fat Weakens Immune Fitness

Much work has been done to reduce cancer immunosuppression through inhibiting soluble proteins, surface molecules, and suppressive cells. This article shows an important role for the lipid lysophosphatidic acid, whose suppression shows promise as a novel cancer immunotherapeutic, demonstrated in ovarian cancer. See related article by Chae et al., 1904 (5).

Tumor Intrinsic PD-L1 Promotes DNA Repair in Distinct Cancers and Suppresses PARP Inhibitor-Induced Synthetic Lethality

BRCA1-mediated homologous recombination is an important DNA repair mechanism that is the target of FDA-approved PARP inhibitors, yet details of BRCA1-mediated functions remain to be fully elucidated. Similarly, immune checkpoint molecules are targets of FDA-approved cancer immunotherapies, but the biological and mechanistic consequences of their application are incompletely understood. We show here that the immune checkpoint molecule PD-L1 regulates homologous recombination in cancer cells by promoting BRCA1 nuclear foci formation and DNA end resection. Genetic depletion of tumor PD-L1 reduced homologous recombination, increased nonhomologous end joining, and elicited synthetic lethality to PARP inhibitors olaparib and talazoparib in vitro in some, but not all, BRCA1 wild-type tumor cells. In vivo, genetic depletion of tumor PD-L1 rendered olaparib-resistant tumors sensitive to olaparib. In contrast, anti-PD-L1 immune checkpoint blockade neither enhanced olaparib synthetic lethality nor improved its efficacy in vitro or in wild-type mice. Tumor PD-L1 did not alter expression of BRCA1 or its cofactor BARD1 but instead coimmunoprecipitated with BARD1 and increased BRCA1 nuclear accumulation. Tumor PD-L1 depletion enhanced tumor CCL5 expression and TANK-binding kinase 1 activation in vitro, similar to known immune-potentiating effects of PARP inhibitors. Collectively, these data define immune-dependent and immune-independent effects of PARP inhibitor treatment and genetic tumor PD-L1 depletion. Moreover, they implicate a tumor cell-intrinsic, immune checkpoint-independent function of PD-L1 in cancer cell BRCA1-mediated DNA damage repair with translational potential, including as a treatment response biomarker.

SIGNIFICANCE

PD-L1 upregulates BRCA1-mediated homologous recombination, and PD-L1-deficient tumors exhibit BRCAness by manifesting synthetic lethality in response to PARP inhibitors, revealing an exploitable therapeutic vulnerability and a candidate treatment response biomarker. See related commentary by Hanks, p. 2069.

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

Despite repeated associations between T cell infiltration and outcome, human ovarian cancer remains poorly responsive to immunotherapy. We report that the 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 (TCF1low) tissue-resident T cells (TRMstem cells), but not recirculating TCF1+ T cells, predict ovarian cancer outcome. TRMstem cells arise from transitional recirculating 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.

Pharmacologic Tumor PDL1 Depletion with Cefepime or Ceftazidime Promotes DNA Damage and Sensitivity to DNA-Damaging Agents

The interaction between tumor surface-expressed PDL1 and immune cell PD1 for the evasion of antitumor immunity is well established and is targeted by FDA-approved anti-PDL1 and anti-PD1 antibodies. Nonetheless, recent studies highlight the immunopathogenicity of tumor-intrinsic PDL1 signals that can contribute to the resistance to targeted small molecules, cytotoxic chemotherapy, and αPD1 immunotherapy. As genetic PDL1 depletion is not currently clinically tractable, we screened FDA-approved drugs to identify those that significantly deplete tumor PDL1. Among the candidates, we identified the β-lactam cephalosporin antibiotic cefepime as a tumor PDL1-depleting drug (PDD) that increases tumor DNA damage and sensitivity to DNA-damaging agents in vitro in distinct aggressive mouse and human cancer lines, including glioblastoma multiforme, ovarian cancer, bladder cancer, and melanoma. Cefepime reduced tumor PDL1 post-translationally through ubiquitination, improved DNA-damaging-agent treatment efficacy in vivo in immune-deficient and -proficient mice, activated immunogenic tumor STING signals, and phenocopied specific genetic PDL1 depletion effects. The β-lactam ring and its antibiotic properties did not appear contributory to PDL1 depletion or to these treatment effects, and the related cephalosporin ceftazidime produced similar effects. Our findings highlight the rapidly translated potential for PDDs to inhibit tumor-intrinsic PDL1 signals and improve DNA-damaging agents and immunotherapy efficacy.

Nitration of CCL2 disrupts the tumor-protective function of CCL2 in bladder cancer

The chemokine CCL2 (C-C motif ligand 2) is best known for its ability to induce trafficking of immune cells by binding its primary receptor, CCR2. The recruitment of immunosuppressive monocytes by CCL2 promotes cancer in several tumor types. Surprisingly, we previously found an unanticipated protective role for CCL2 signaling in bladder cancer (BC). To determine if CCL2’s effect to suppress bladder tumor growth is dependent on T cells, we examined the effects of α-CCL2 antibody in wild-type versus T cell-deficient mice. The protective effect of CCL2 was lost in T cell-deficient mice and on T cell depletion in wild-type mice. Mixed bone marrow chimera experiments also showed that CCR2+ T cells were preferentially recruited by CCL2 to the bladder compared with CCR2− T cells suggesting that the protective effect of CCL2 in BC is through CCR2+ T cells. Most studies researching chemokines, including CCL2, in cancer assume the chemokine to be completely active and do not consider their different modified states which may be one of the critical reasons behind the failure of chemokines in clinical trials. We show for the first time that bladder tumors induce post-translational nitration of CCL2 and block T cell recruitment to the bladder which is restored by exogenous recombinant (r) CCL2 treatment. However, the chemical nitration of rCCL2 abolished this therapeutic efficacy of rCCL2 and was associated with decreased bladder T cell infiltration and more monocytes infiltration in BC. Our study analyzed the role of nitrated CCL2 in BC which explained certain paradoxes between CCL2 levels and patient outcomes in cancer. We also developed a novel BC treatment strategy using rCCL2 which should lead to effective combinations with existing BC immunotherapies.

Supported by (1) the Mays Family Cancer Center at University of Texas Health San Antonio (P30 CA054174), (2) the Roger L. And Laura D. Zeller Charitable Foundation Chair in Urologic Cancer, (3) the Glenda and Gary Woods Distinguished Chair in GU Oncology, (4) the Max & Minnie Tomerlin Voelcker Fund, (5) CDMRP CA170270/P1P2, (6) Bladder Cancer Advocacy Network (BCAN), (7) Research Training Award (RP170345) from the Cancer Prevention & Research Institute of Texas (8) MSTP Program (NIH T32GM113896)

PD-L1 plays a B cell-intrinsic role in suppressing the antibody response and anti-tumor immunity

The discovery that PD-L1 inhibits PD-1 on CD8+ T cells has led to new mechanistic insights into the regulation of host immune responses. The contribution of PD-L1 expressed by different immune cell types remains poorly understood, partly due to the lack of cell type-specific Cd274 (encoding PD-L1) knockout mice. Here, to address the role of B cell-expressed PD-L1 in antibody response and tumor development, we have generated AicdacreCd274fl/fl mice, in which PD-L1 was ablated only in activated B cells. As compared to their wild-type littermates, AicdacreCd274fl/fl mice showed normal development and maintenance of B cells, T cells, DCs and macrophages, while mounting a stronger T-dependent high affinity NP-binding IgM, IgG1 and IgG2a titers upon immunization with NP-CGG plus alum. Such phenotype was copied by C57 mice treated with a blocking αPD-L1 antibody. Tumor growth from engrafted E0771 breast cancer cells in AicdacreCd274fl/fl mice was significantly delayed, in association with increased CD8+ T cell infiltration and activities. Moreover, B cells isolated from AicdacreCd274fl/fl mice or those treated with aPD-L1 displayed higher levels of proliferation and differentiation to plasma cells upon in vitro stimulation with the T-dependent B-cell stimulus CD154. This along with the altered gene expression in AicdacreCd274fl/fl mice and αPD-L1-treated cells suggests a B cell-intrinsic role of PD-L1 in regulating B cell differentiation. Furthermore, PD-L1 expressed on B cell surface was tightly regulated during differentiation and internalized upon αPD-L1 treatment, suggesting a possible new mechanism on how PD-L1+ B cells modulate host immune responses.

Supported by grants from NIH: The Ruth L. Kirschstein NRSA Institutional Research Training Grant (to MK), NIH T32 Graduate Research in Immunology Program (to CC),  R01 AI153506 and R21 AI135599 (to ZX). Mays Cancer Center Dew Foundation Pilot Grant (to ZX) and DoD BCRP BC170448 (to ZX)

Spontaneous class-switched antibody responses at endometrial cancer tumor bed drives superior patients’ outcome

The role of humoral responses in endometrial cancer remains insufficiently investigated. Using a cohort of 107 patients with different histological subtypes of endometrial carcinoma, we report that concomitant accumulation of T, B and plasma cells at tumor beds predicts better survival. However, only B cell markers predict survival specifically in high-grade endometrioid type and serous tumors. Accordingly, immune protection is associated with class-switched IgA and, to a lesser extent, IgG. Notably, expression of polymeric immunoglobulin receptor (pIgR) by tumor cells and its occupancy by IgA are superior predictors of outcome, and correlate with defects in methyl mismatch repair. Mechanistically, pIgR-dependent, antigen-independent IgA occupancy drives inflammatory pathways associated with IFN and TNF signaling in tumor cells, along with apoptotic and ER stress pathways, while thwarting DNA repair mechanisms. Therefore, coordinated humoral and cellular immune responses, characterized by IgA:pIgR interactions in tumor cells, determine the progression of human endometrial cancer, and therefore the potential for effective immunotherapies.

Supported by grants from NIH (R01CA157664, R01CA124515, R01CA178687 and R01CA211913), and from Cancer Center Support Grant (CCSG) CA076292

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.)

Programmed death ligand 1 signals in cancer cells

The paradigm of surface-expressed programmed death ligand 1 (PDL1) signalling to immune cell programmed death 1 (PD1) to inhibit antitumour immunity has helped to develop effective and revolutionary immunotherapies using antibodies blocking these cell-extrinsic interactions. The recent discovery of cancer cell-intrinsic PDL1 signals has broadened understanding of pathologic tumour PDL1 signal consequences that now includes control of tumour growth and survival pathways, stemness, immune effects, DNA damage responses and gene expression regulation. Many such effects are PD1-independent. These insights demonstrate that the prevailing cell-extrinsic PDL1 signalling paradigm is useful, but incomplete in important respects. This Perspective discusses historical and recent advances in understanding cancer cell-intrinsic PDL1 signals, mechanisms for signal controls and important immunopathologic consequences including resistance to cytotoxic agents, targeted small molecules and immunotherapies. Cancer cell-intrinsic PDL1 signals present novel drug discovery targets and also have potential as reliable treatment response biomarkers. Cancer cell-intrinsic PD1 signals and cell-intrinsic PDL1 signals in non-cancer cells are discussed briefly, as are PDL1 signals from soluble and vesicle-bound PDL1 and PDL1 isoforms. We conclude with suggestions for addressing the most pressing challenges and opportunities in this rapidly developing field.

Immune checkpoint expression and relationships to anti-PD-L1 immune checkpoint blockade cancer immunotherapy efficacy in aged versus young mice

Introduction

Aging is the biggest cancer risk, and immune checkpoint (IC) inhibition (ICI) is a revolutionary cancer immunotherapy approach. Nonetheless, there are limited preclinical/clinical data regarding aging effects on ICI outcomes or age effects on IC expression in different organs or tumors.

Methods

Flow cytometry assessed IC on immune and non-immune cells in various organs in young and aged BL6 mice. Comparisons: aged versus young naïve WT versus interferon-γ ^KO mice and WT challenged with B16F10 melanoma and treated with αPD-1 or αPD-L1 ICI. We co-cultured young and aged T cells and myeloid cells in vitro and used OMIQ analyses to test cell-cell interactions.

Results

αPD-1 ICI treated melanoma in young and aged hosts, whereas αPD-L1 ICI was only effective in young. We found considerable, previously undescribed age effects on expression of various IC molecules participating in the ICI treatment, including PD-1, PD-L1, PD-L2, and CD80, in distinct organs and in the tumor. These data help explain differential ICI efficacy in young and aged hosts. Host interferon-γ influenced age effects on IC expression in both directions depending on specific IC molecule and tissue. IC expression was further affected by tumor challenge on immune, non-immune, and tumor cells in tumor and other organs. In in vitro co-culture, αPD-1 versus αPD-L1 distinctly influenced polyclonal T cells in young versus aged, suggesting mechanisms for distinct age-related ICI outcomes.

Conclusion

Age affects IC expression on specific immune cells in an organ- and tissue-specific manner. ICs were generally higher on aged immune cells. High immune-cell PD-1 could help explain αPD-1 efficacy in aged. High co-expression of CD80 with PD-L1 on dendritic cells could help explain lack of αPD-L1 efficacy in aged hosts. Factors other than myeloid cells and interferon-γ also affect age-related IC expression and T cell function, meriting additional studies.

Alignment of single-cell trajectories by tuMap enables high-resolution quantitative comparison of cancer samples

Single-cell technologies allow characterization of cancer samples as continuous developmental trajectories. Yet, the obtained temporal resolution cannot be leveraged for a comparative analysis due to the large phenotypic heterogeneity existing between patients. Here, we present the tuMap algorithm that exploits high-dimensional single-cell data of cancer samples exhibiting an underlying developmental structure to align them with the healthy development, yielding the tuMap pseudotime axis that allows their systematic, meaningful comparison. We applied tuMap on single-cell mass cytometry data of acute lymphoblastic and myeloid leukemia to reveal associations between the tuMap pseudotime axis and clinics that outperform cellular assignment into developmental populations. Application of the tuMap algorithm on single-cell RNA sequencing data further identified gene signatures of stem cells residing at the very-early parts of the cancer trajectories. The quantitative framework provided by tuMap allows generation of metrics for cancer patients evaluation.

TGF-β-mediated silencing of genomic organizer SATB1 promotes Tfh cell differentiation and formation of intra-tumoral tertiary lymphoid structures

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. The transfer of Tfh cells, but not naive 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.

CD122-targeted interleukin-2 and αPD-L1 treat bladder cancer and melanoma via distinct mechanisms, including CD122-driven natural killer cell maturation

Bladder cancer (BC) and melanoma are amenable to immune checkpoint blockade (ICB) therapy, yet most patients with advanced/metastatic disease do not respond. CD122-targeted interleukin (IL)-2 can improve ICB efficacy, but mechanisms are unclear. We tested αPD-L1 and CD122-directed immunotherapy with IL-2/αIL-2 complexes (IL-2c) in primary and metastatic bladder and melanoma tumors. IL-2c treatment of orthotopic MB49 and MBT-2 BC generated NK cell antitumor immunity through enhanced activation, reduced exhaustion, and promotion of a mature, effector NK cell phenotype. By comparison, subcutaneous B16-F10 melanoma, which is IL-2c sensitive, requires CD8⁺ T and not NK cells, yet we found αPD-L1 efficacy requires both CD8⁺ T and NK cells. We then explored αPD-L1 and IL-2c mechanisms at distinct metastatic sites and found intraperitoneal B16-F10 metastases were sensitive to αPD-L1 and IL-2c, with IL-2c but not αPD-L1, increasing CD122⁺ mature NK cell function, confirming conserved IL-2c effects in distinct cancer types and anatomic compartments. αPD-L1 failed to control tumor growth and prolong survival in B16-F10 lung metastases, yet IL-2c treated B16-F10 lung metastases effectively even in T cell and adaptive immunity deficient mice, which was abrogated by NK cell depletion in wild-type mice. Flow cytometric analyses of NK cells in B16-F10 lung metastases suggest that IL-2c directly boosts NK cell activation and effector function. Thus, αPD-L1 and IL-2c mediate nonredundant, immune microenvironment-specific treatment mechanisms involving CD8⁺ T and NK cells in primary and metastatic BC and melanoma. Mechanistic differences suggest effective treatment combinations including in other tumors or sites, warranting further studies.

γδ T Cells Support Antigen-Specific αβ T cell-Mediated Antitumor Responses during BCG Treatment for Bladder Cancer

Bacillus Calmette-Guérin (BCG) is the most effective intravesical agent at reducing recurrence for patients with high-grade, non-muscle-invasive bladder cancer. Nevertheless, response to BCG is variable and strategies to boost BCG efficacy have not materialized. Prior work demonstrated a requirement for either conventional αβ or nonconventional γδ T cells in mediating BCG treatment efficacy, yet the importance of T-cell antigen specificity for BCG's treatment effect is unclear. Here, we provide direct evidence to show that BCG increases the number of tumor antigen-specific αβ T cells in patients with bladder cancer and protects mice from subsequent same-tumor challenge, supporting BCG induction of tumor-specific memory and protection. Adoptive T-cell transfers of antigen-specific αβ T cells into immunodeficient mice challenged with syngeneic MB49 bladder tumors showed that both tumor and BCG antigen-specific αβ T cells contributed to BCG efficacy. BCG-specific antitumor immunity, however, also required nonconventional γδ T cells. Prior work shows that the mTOR inhibitor rapamycin induces the proliferation and effector function of γδ T cells. Here, rapamycin increased BCG efficacy against both mouse and human bladder cancer in vivo in a γδ T cell-dependent manner. Thus, γδ T cells augment antitumor adaptive immune effects of BCG and support rapamycin as a promising approach to boost BCG efficacy in the treatment of non-muscle-invasive bladder cancer.

Tumour DDR1 promotes collagen fibre alignment to instigate immune exclusion

Immune exclusion predicts poor patient outcomes in multiple malignancies, including triple-negative breast cancer (TNBC)¹. The extracellular matrix (ECM) contributes to immune exclusion². However, strategies to reduce ECM abundance are largely ineffective or generate undesired outcomes^3,4. Here we show that discoidin domain receptor 1 (DDR1), a collagen receptor with tyrosine kinase activity⁵, instigates immune exclusion by promoting collagen fibre alignment. Ablation of Ddr1 in tumours promotes the intratumoral penetration of T cells and obliterates tumour growth in mouse models of TNBC. Supporting this finding, in human TNBC the expression of DDR1 negatively correlates with the intratumoral abundance of anti-tumour T cells. The DDR1 extracellular domain (DDR1-ECD), but not its intracellular kinase domain, is required for immune exclusion. Membrane-untethered DDR1-ECD is sufficient to rescue the growth of Ddr1-knockout tumours in immunocompetent hosts. Mechanistically, the binding of DDR1-ECD to collagen enforces aligned collagen fibres and obstructs immune infiltration. ECD-neutralizing antibodies disrupt collagen fibre alignment, mitigate immune exclusion and inhibit tumour growth in immunocompetent hosts. Together, our findings identify a mechanism for immune exclusion and suggest an immunotherapeutic target for increasing immune accessibility through reconfiguration of the tumour ECM.

Resident memory CD8+ T cells in regional lymph nodes mediate immunity to metastatic melanoma

The nature of the anti-tumor immune response changes as primary tumors progress and metastasize. We investigated the role of resident memory (Trm) and circulating memory (Tcirm) cells in anti-tumor responses at metastatic locations using a mouse model of melanoma-associated vitiligo. We found that the transcriptional characteristics of tumor-specific CD8+ T cells were defined by the tissue of occupancy. Parabiosis revealed that tumor-specific Trm and Tcirm compartments persisted throughout visceral organs, but Trm cells dominated lymph nodes (LNs). Single-cell RNA-sequencing profiles of Trm cells in LN and skin were distinct, and T cell clonotypes that occupied both tissues were overwhelmingly maintained as Trm in LNs. Whereas Tcirm cells prevented melanoma growth in the lungs, Trm afforded long-lived protection against melanoma seeding in LNs. Expanded Trm populations were also present in melanoma-involved LNs from patients, and their transcriptional signature predicted better survival. Thus, tumor-specific Trm cells persist in LNs, restricting metastatic cancer.

CD122-SELECTIVE IL-2 COMPLEXES TREAT OVARIAN CARCINOMAS, INDUCE TREG FRAGILITY AND PROMOTE T CELL STEM CELLS

Regulatory T cells (Treg) engage IL-2 by high affinity CD25, and anti-tumor effector T cells (Teff) use intermediate affinity CD122. We studied IL-2 complexes (IL-2c) that selectively activate CD122+ Teff over CD25+ Tregs. We found IL-2c but not aPD-L1 potently inhibits ID8agg, an aggressive mouse ovarian cancer (OC) model. IL-2c decreased ascites Treg functional markers (CD25, GranzymeB) while upregulating them on Teffs. IL-2c inhibited Treg suppressive function in ascites but not TDLN. Ascites Tregs after IL-2c showed a fragile phenotype (increased PD-1, T-bet, and IFNg with maintained FoxP3) known to contribute to better immunotherapy response. These data suggest IL-2c inhibits Treg in the ascites through inducing fragile Tregs. Neither CD8+ T cells nor gd T cells is required for IL-2c induced Treg fragility. Studies testing other populations are ongoing. CD8+TCF-1+T cell stem cells (TCSC) improve immune checkpoint blockade in many cancer types. In ID8agg tumors, IL-2c induces CD8+TCF-1+ TCSC with tumor inhibitory capacity when transferred into Rag KO mice. tSNE analysis revealed IL-2c-induced TCSC are CXCR5+PD-1− express CCR2 CXCR3 and produce TNFa, while aPD-L1 induced TCSC are CXCR5+ and PD-1+, consistent with previous reports. These data suggest IL-2c induces beneficial CD8+TCSC distinct from aPD-L1. Although aPD-L1 is not efficacious alone in ID8agg, it significantly promoted IL-2c efficacy. Mice treated with IL-2c+αPD-L1 are resistant to tumor re-challenge even 6 weeks after final dose, suggesting durable immune memory. In sum, IL-2c is a novel OC immunotherapy that targets distinct immune pathways simultaneously, including inhibiting Tregs, boosting TCSCs, and inducing immune memory when combined with aPD-L1.

Intracellular PD-L1 regulates DNA damage checkpoints and suppresses Chk1 and PARP inhibitor synthetic lethality

Tumor PD-L1 mediates non-canonical, intracellular signals including the DNA damage response (DDR), of unclear significance and mechanisms. We show that genetic PD-L1 depletion (PD-L1KO) destabilized the Chk2 protein, a DNA damage response (DDR) factor, resulting in ATM/Chk2 pathway defects but not ATR/Chk1 in melanoma, bladder, breast, and ovarian cancer. Consistent with ATM/Chk2 defects, PD-L1 KO led to DNA damage (γH2AX) and impaired homologous recombination (HR) (p-RPA32, BRCA1, Rad51 foci). Thus, PD-L1 KO vs control cells were significantly more sensitive to DDR inhibitors (DDRi) against ATR, Chk1, and PARP in vitro and in vivo in NSG mice. Chk2 regulation by PD-L1 was independent of PD-L1 cytoplasmic tail yet required intracellular (vs surface) PD-L1 suggesting physical PD-L1/Chk2 interaction supported by IP and imaging. PD-L1 stabilized Chk2 protein by preventing its lysosomal degradation without altering Chek2 mRNA. αPD-L1 is thought to work by protecting PD-L1 induced anti-tumor T cell suppression via PD-1, but PD-L1 DDR effects were PD-1-independent. Intracellular PD-L1 suppressed DDRi induced cGAS/STING activation by immunoblots and qRT-PCR of type 1 IFN genes. In vivo in WT mice, genetic PD-L1 depletion but not αPD-L1, sensitized highly immunotherapy resistant 4T1 breast cancer to PARPi. Strikingly, PARPi had reduced effect on PD-L1KO tumors in RAG2KO mice despite treating WT mice, indicating a strong immune component to DDRi efficacy. Our work implicates a novel role of intracellular PD-L1 in DDR and tumor immunogenicity and identifies related therapeutic vulnerabilities exposed by intracellular PD-L1 targeting. Surface vs intracellular PD-L1, and specific DDR signals could be treatment response biomarkers.

CD122-directed interleukin-2 treatment mechanisms in bladder cancer differ from αPD-L1 and include tissue-selective γδ T cell activation

BACKGROUND

Anti-programmed death-ligand 1 (αPD-L1) immunotherapy is approved to treat bladder cancer (BC) but is effective in <30% of patients. Interleukin (IL)-2/αIL-2 complexes (IL-2c) that preferentially target IL-2 receptor β (CD122) augment CD8⁺ antitumor T cells known to improve αPD-L1 efficacy. We hypothesized that the tumor microenvironment, including local immune cells in primary versus metastatic BC, differentially affects immunotherapy responses and that IL-2c effects could differ from, and thus complement αPD-L1.

METHODS

We studied mechanisms of IL-2c and αPD-L1 efficacy using PD-L1⁺ mouse BC cell lines MB49 and MBT-2 in orthotopic (bladder) and metastatic (lung) sites.

RESULTS

IL-2c reduced orthotopic tumor burden and extended survival in MB49 and MBT-2 BC models, similar to αPD-L1. Using antibody-mediated cell depletions and genetically T cell-deficient mice, we unexpectedly found that CD8⁺ T cells were not necessary for IL-2c efficacy against tumors in bladder, whereas γδ T cells, not reported to contribute to αPD-L1 efficacy, were indispensable for IL-2c efficacy there. αPD-L1 responsiveness in bladder required conventional T cells as expected, but not γδ T cells, altogether defining distinct mechanisms for IL-2c and αPD-L1 efficacy. γδ T cells did not improve IL-2c treatment of subcutaneously challenged BC or orthotopic (peritoneal) ovarian cancer, consistent with tissue-specific and/or tumor-specific γδ T cell contributions to IL-2c efficacy. IL-2c significantly altered bladder intratumoral γδ T cell content, activation status, and specific γδ T cell subsets with antitumor or protumor effector functions. Neither IL-2c nor αPD-L1 alone treated lung metastatic MB49 or MBT-2 BC, but their combination improved survival in both models. Combination treatment efficacy in lungs required CD8⁺ T cells but not γδ T cells.

CONCLUSIONS

Mechanistic insights into differential IL-2c and αPD-L1 treatment and tissue-dependent effects could help develop rational combination treatment strategies to improve treatment efficacy in distinct cancers. These studies also provide insights into γδ T cell contributions to immunotherapy in bladder and engagement of adaptive immunity by IL-2c plus αPD-L1 to treat refractory lung metastases.

IFNα Augments Clinical Efficacy of Regulatory T-cell Depletion with Denileukin Diftitox in Ovarian Cancer

PURPOSE

Immunotherapy treats some cancers, but not ovarian cancer. Regulatory T cells (Tregs) impede anti-ovarian cancer immunity but effective human Treg-directed treatments are lacking. We tested Treg depletion with denileukin diftitox (DD) ± IFNα as ovarian cancer immunotherapy.

PATIENTS AND METHODS

Mice with syngeneic ID8 ovarian cancer challenge were treated with DD, IFNα, or both. The phase 0/I trial tested one dose-escalated DD infusion for functional Treg reduction, safety, and tolerability. The phase II trial added IFNα2a to DD if DD alone failed clinically.

RESULTS

DD depleted Tregs, and improved antitumor immunity and survival in mice. IFNα significantly improved antitumor immunity and survival with DD. IFNα did not alter Treg numbers or function but boosted tumor-specific immunity and reduced tumor Treg function with DD by inducing dendritic cell IL6. DD alone was well tolerated, depleted functional blood Tregs and improved immunity in patients with various malignancies in phase 0/I. A patient with ovarian cancer in phase 0/I experienced partial clinical response prompting a phase II ovarian cancer trial, but DD alone failed phase II. Another phase II trial added pegylated IFNα2a to failed DD, producing immunologic and clinical benefit in two of two patients before a DD shortage halt. DD alone was well tolerated. Adding IFNα increased toxicities but was tolerable, and reduced human Treg numbers in blood, and function through dendritic cell-induced IL6 in vitro.

CONCLUSIONS

Treg depletion is clinically useful but unlikely alone to cure ovarian cancer. Rational treatment agent combinations can salvage clinical failure of Treg depletion alone, even when neither single agent provides meaningful clinical benefit.

Rapamycin enhances BCG-specific γδ T cells during intravesical BCG therapy for non-muscle invasive bladder cancer: a randomized, double-blind study

BACKGROUND

Although intravesical BCG is the standard treatment of high-grade non-muscle invasive bladder cancer (NMIBC), response rates remain unsatisfactory. In preclinical models, rapamycin enhances BCG vaccine efficacy against tuberculosis and the killing capacity of γδ T cells, which are critical for BCG's antitumor effects. Here, we monitored immunity, safety, and tolerability of rapamycin combined with BCG in patients with NMIBC.

METHODS

A randomized double-blind trial of oral rapamycin (0.5 or 2.0 mg daily) versus placebo for 1 month was conducted in patients with NMIBC concurrently receiving 3 weekly BCG instillations (NCT02753309). The primary outcome was induction of BCG-specific γδ T cells, measured as a percentage change from baseline. Post-BCG urinary cytokines and immune cells were examined as surrogates for local immune response in the bladder. Secondary outcomes measured were adverse events (AEs) and tolerability using validated patient-reported questionnaires.

RESULTS

Thirty-one patients were randomized (11 placebo, 8 rapamycin 2.0 mg, and 12 rapamycin 0.5 mg). AEs were similar across groups and most were grade 1-2. One (12.5%) patient randomized to 2.0 mg rapamycin was taken off treatment due to stomatitis. No significant differences in urinary symptoms, bowel function, or bother were observed between groups. The median (IQR) percentage change in BCG-specific γδ T cells from baseline per group was as follows: -26% (-51% to 24%) for placebo, 9.6% (-59% to 117%) for rapamycin 0.5 mg (versus placebo, p=0.18), and 78.8% (-31% to 115%) for rapamycin 2.0 mg (versus placebo, p=0.03). BCG-induced cytokines showed a progressive increase in IL-8 (p=0.02) and TNF-α (p=0.04) over time for patients on rapamycin 2.0 mg, whereas patients receiving placebo had no significant change in urinary cytokines. Compared with placebo, patients receiving 2.0 mg rapamycin had increased urinary γδ T cells at the first week of BCG (p=0.02).

CONCLUSIONS

Four weeks of 0.5 and 2.0 mg oral rapamycin daily is safe and tolerable in combination with BCG for patients with NMIBC. Rapamycin enhances BCG-specific γδ T cell immunity and boosts urinary cytokines during BCG treatment. Further study is needed to determine long-term rapamycin safety, tolerability and effects on BCG efficacy.

Bladder cancer cell-intrinsic PD-L1 signals promote mTOR and autophagy activation that can be inhibited to improve cytotoxic chemotherapy

Tumor cell-intrinsic programmed death-ligand 1 (PD-L1) signals mediate immunopathologic effects in breast, colon, and ovarian cancers and in melanomas, but bladder cancer (BC) effects are unreported. We show here that BC cell-intrinsic PD-L1 signals in mouse MB49 and human RT4, UM-UC3, and UM-UC-14 BC cells regulate important pathologic pathways and processes, including effects not reported in other cancers. α-PD-L1 antibodies reduced BC cell proliferation in vitro, demonstrating direct signaling effects. BC cell-intrinsic PD-L1 promoted mammalian target of rapamycin complex 1 (mTORC1) signals in vitro and augmented in vivo immune-independent cell growth and metastatic cancer spread, similar to effects we reported in melanoma and ovarian cancer. BC cell-intrinsic PD-L1 signals also promoted basal and stress-induced autophagy, whereas these signals inhibited autophagy in melanoma and ovarian cancer cells. BC cell-intrinsic PD-L1 also mediated chemotherapy resistance to the commonly used BC chemotherapy agents cis-platinum and gemcitabine and to the mTORC1 inhibitor, rapamycin. Thus, BC cell-intrinsic PD-L1 signals regulate important virulence and treatment resistance pathways that suggest novel, actionable treatment targets meriting additional studies. As a proof-of-concept, we showed that the autophagy inhibitor chloroquine improved cis-platinum treatment efficacy in vivo, with greater efficacy in PD-L1 null versus PD-L1-replete BC.

Abstract PR004: Genetic ablation of adipocyte PD-L1 reduces tumor growth but accentuates obesity-associated inflammation

The programmed death-ligand 1 (PD-L1)-dependent immune checkpoint attenuates host immunity and maintains self-tolerance. Imbalance between protective immunity and immunopathology due to altered PD-L1 signaling can lead to autoimmunity or tumor immunosuppression. The role of the PD-L1-dependent checkpoint in non-immune system is less reported. We previously found that white adipocytes highly express PD-L1. Here we show that adipocyte-specific PD-L1 knockout mice exhibit enhanced host anti-tumor immunity against mammary tumors and melanoma with low or no tumor PD-L1. However, adipocyte PD-L1 ablation in tumor-free mice also exacerbates diet-induced body weight gain, pro-inflammatory macrophage infiltration into adipose tissue, and insulin resistance. Low PD-L1 mRNA levels in human adipose tissue correlate with high body mass index and presence of type 2 diabetes. Therefore, our mouse genetic approach unequivocally demonstrates a cell-autonomous function of adipocyte PD-L1 in promoting tumor growth and inhibiting anti-tumor immunity. In addition, our work uncovers a previously unrecognized role of adipocyte PD-L1 in mitigating obesity-related inflammation and metabolic dysfunction.

This abstract is also being presented as PO031.

Citation Format: Bogang Wu, Huai-Chin Chiang, Xiujie Sun, Bin Yuan, Payal Mitra, Yanfen Hu, Tyler J. Curiel, Rong Li. Genetic ablation of adipocyte PD-L1 reduces tumor growth but accentuates obesity-associated inflammation [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PR004.

Estrogen receptor beta signaling in CD8+ T cells boosts T cell receptor activation and antitumor immunity through a phosphotyrosine switch

The non-overlapping functions of the two estrogen receptor subtypes, ERα (Estrogen Receptor α)and ERβ (Estrogen Receptor β), in tumor cells have been studied extensively. However, their counterparts in host cells is vastly underinterrogated. Even less is known about how ERα and ERβ activities are regulated in a subtype-specific manner. We previously identified a phosphotyrosine residue (pY36) of human ERβ that is important for tumor ERβ to inhibit growth of breast cancer cells in vitro and in vivo. A role of this ERβ phosphotyrosine switch in regulating host ERβ remains unclear.Conventional gene editing was used to mutate the corresponding tyrosine residue of endogenous mouse ERβ (Y55F) in mouse embryonic stem cells. The derived homozygous mutant Esr2^Y55F/Y55F mouse strain and its wild-type (WT) counterpart were compared in various transplant tumor models for their ability to support tumor growth. In addition, flow cytometry-based immunophenotyping was carried out to assess antitumor immunity of WT and mutant hosts. Adoptive transfer of bone marrow and purified CD8⁺ T cells were performed to identify the host cell type that harbors ERβ-dependent antitumor function. Furthermore, cell signaling assays were conducted to compare T cell receptor (TCR)-initiated signaling cascade in CD8⁺ T cells of WT and mutant mice. Lastly, the ERβ-selective agonist S-equol was evaluated for its efficacy to boost immune checkpoint blockade (ICB)-based anticancer immunotherapy.Disabling the ERβ-specific phosphotyrosine switch in tumor-bearing hosts exacerbates tumor growth. Further, a cell-autonomous ERβ function was defined in CD8⁺ effector T cells. Mechanistically, TCR activation triggers ERβ phosphorylation, which in turn augments the downstream TCR signaling cascade via a non-genomic action of ERβ. S-equol facilitates TCR activation that stimulates the ERβ phosphotyrosine switch and boosts anti-PD-1 (Programmed cell death protein 1) ICB immunotherapy.

Our mouse genetic study clearly demonstrates a role of the ERβ phosphotyrosine switch in regulating ERβ-dependent antitumor immunity in CD8⁺ T cells. Our findings support the development of ERβ agonists including S-equol in combination with ICB immunotherapy for cancer treatment.

CD122-Selective IL2 Complexes Reduce Immunosuppression, Promote Treg Fragility, and Sensitize Tumor Response to PD-L1 Blockade

The IL2 receptor (IL2R) is an attractive cancer immunotherapy target that controls immunosuppressive T regulatory cells (Treg) and antitumor T cells. Here we used IL2Rβ-selective IL2/anti-IL2 complexes (IL2c) to stimulate effector T cells preferentially in the orthotopic mouse ID8agg ovarian cancer model. Despite strong tumor rejection, IL2c unexpectedly lowered the tumor microenvironmental CD8+/Treg ratio. IL2c reduced tumor microenvironmental Treg suppression and induced a fragile Treg phenotype, helping explain improved efficacy despite numerically increased Tregs without affecting Treg in draining lymph nodes. IL2c also reduced Treg-mediated, high-affinity IL2R signaling needed for optimal Treg functions, a likely mechanism for reduced Treg suppression. Effector T-cell IL2R signaling was simultaneously improved, suggesting that IL2c inhibits Treg functions without hindering effector T cells, a limitation of most Treg depletion agents. Anti-PD-L1 antibody did not treat ID8agg, but adding IL2c generated complete tumor regressions and protective immune memory not achieved by either monotherapy. Similar anti-PD-L1 augmentation of IL2c and degradation of Treg functions were seen in subcutaneous B16 melanoma. Thus, IL2c is a multifunctional immunotherapy agent that stimulates immunity, reduces immunosuppression in a site-specific manner, and combines with other immunotherapies to treat distinct tumors in distinct anatomic compartments. SIGNIFICANCE: These findings present CD122-targeted IL2 complexes as an advancement in cancer immunotherapy, as they reduce Treg immunosuppression, improve anticancer immunity, and boost PD-L1 immune checkpoint blockade efficacy in distinct tumors and anatomic locations.

Abstract B10: High-dimensional (30-plex) imaging mass cytometry on tissue microarray identifies novel PD-L1-inclusive immunophenotypes associated with overall survival in stage III melanoma

We sought to determine the subcellular distribution of 30+ immune-related markers including PD-L1 in stage III melanoma tumor tissues (nuclear, cytoplasmic, surface) using novel imaging mass cytometry technology that enables simultaneous detection of over 30 immune and tumor markers. Metal-tagged antibodies were used to stain stage III melanoma tissues similarly to an IHC-based protocol, followed by laser ablation and mass cytometry using the Helios® and Hyperion® technology (Fluidigm). Markers for immune subsets included CD45, CD3, CD4, CD8, PD-1, Granzyme B, FoxP3, CD11b, CD11c, CD107, CD20, Vista, and CD68. Markers for tumor cell phenotyping included PD-L1 (intracellular and extracellular domain specific), E-cadherin, B-catenin, PD-L2, and keratin 8/18. Structural, inflammatory, survival, and signaling markers included Ki67, p53, p-tyrosine, Bcl-2, Cl-caspase 3, histone H3, collagen-1, actin, and arginase-1. We further validated subcellular distribution of PD-L1 in the same patient tumor cores using fluorochrome-labeled antibodies and 100X confocal microscopy to show difference in surface-only, cytoplasmic-only, and nuclear PD-L1. We then assessed the association between subcellular PD-L1 and immune populations in the tumor microenvironment, along with overall and recurrence-free survival. We wrote custom algorithms for data processing to identify novel immune subsets, ran SPADE and viSNE analyses for cross-validation, and employed Imaris Bitplane software to validate our own algorithms for immune population identification. Overall, we found that intracellular-only PD-L1 in tumor tissues has the highest correlation (Pearson r) to CD11b, FoxP3, PD-1, arginase, Ki67, PD-L2 and nuclear stain iridium, while extracellular (surface) PD-L1 in tumors has the highest correlation (Pearson r) to FoxP3, PD-1, arginase, Ki67, PD-L2 and Vista. We identified two novel immunophenotypes (histone-3+/p-tyrosinehi /Vistalo / PD-L1-ICDlo / PD-L1-ECDlo and CD11bhi / PD-L1-ICDhi / PD-L1-ECDhi) that are positively associated with overall patient survival. Of note, only phospho-Tyrhi was significantly associated with RFS. This work highlights the use of cutting-edge technology that can employ the highest multiplexing available for assessing novel interactions of 30+ tumor tissue markers for identification of novel immunophenotypes and biomarker in stage III melanoma patients. Our novel study showcases a novel methodologic approach to high-throughput analysis of retrospective profiling of the melanoma tumor immune microenvironment on a single IHC slide, followed by appropriate and rigorous cross-validation using Fluidigm’s novel CyTOF imaging technology. Our study provides a groundwork for this powerful, novel technology in translational and clinical research for biomarker identification and identification of novel combinatorial markers that may predict overall and recurrence-free survival in stage III melanoma.

Citation Format: Heather G. Hambright, Anand V.R. Kornepati, Dai Ogata, Roland R.L. Bassett, Suhendan Ekmekcioglu, Elizabeth A. Grimm, Tyler J. Curiel. High-dimensional (30-plex) imaging mass cytometry on tissue microarray identifies novel PD-L1-inclusive immunophenotypes associated with overall survival in stage III melanoma [abstract]. In: Proceedings of the AACR Special Conference on Melanoma: From Biology to Target; 2019 Jan 15-18; Houston, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(19 Suppl):Abstract nr B10.

Genetic ablation of adipocyte PD-L1 reduces tumor growth but accentuates obesity-associated inflammation

The programmed death-ligand 1 (PD-L1)-dependent immune checkpoint attenuates host immunity and maintains self-tolerance. Imbalance between protective immunity and immunopathology due to altered PD-L1 signaling can lead to autoimmunity or tumor immunosuppression. The role of the PD-L1-dependent checkpoint in non-immune system is less reported. We previously found that white adipocytes highly express PD-L1. Here we show that adipocyte-specific PD-L1 knockout mice exhibit enhanced host anti-tumor immunity against mammary tumors and melanoma with low or no tumor PD-L1. However, adipocyte PD-L1 ablation in tumor-free mice also exacerbates diet-induced body weight gain, pro-inflammatory macrophage infiltration into adipose tissue, and insulin resistance. Low PD-L1 mRNA levels in human adipose tissue correlate with high body mass index and presence of type 2 diabetes. Therefore, our mouse genetic approach unequivocally demonstrates a cell-autonomous function of adipocyte PD-L1 in promoting tumor growth and inhibiting antitumor immunity. In addition, our work uncovers a previously unrecognized role of adipocyte PD-L1 in mitigating obesity-related inflammation and metabolic dysfunction.

Adipocyte PD-L1 suppresses anti-tumor immune response and promotes breast cancer progression

PD-L1 has become a major target in anti-cancer immunotherapy, however the overall response rate still remains relatively low among most types of cancers, notably breast cancer. There is an unmet need to boost efficacy of immune checkpoint blockade therapies. While both tumor and host immune cell-derived PD-L1 are implicated in immune suppressive functions of PD-L1, the exact immunosuppressive contribution of PD-L1 from different host tissues is little studied. Here we show that PD-L1 expression is significantly higher in human breast adipose tissue versus stromal vascular fractions. In vitro adipogenesis of mouse pre-adipocytes significantly up-regulates PD-L1 versus pre-adipocytes. In vitro co-culture shows that adipocyte PD-L1 suppresses T cell activation and response to anti-PD-L1. In an adipocyte-specific knockout (KO) mouse model, we show that syngeneic mammary tumors grow slower in KO than wildtype hosts. Immunophenotyping shows that tumors grown in KO mice have higher CD8+and CD4+ T cell infiltration as well as more CD8+ Prf+ cytotoxic T cells. Tumor tissue RNA-seq analysis reveals that genetic ablation of adipocyte PD-L1 confers a distinct transcriptomic signature of T cell activation and tumor killing. Our current findings uncover a previously unappreciated source of immune suppressive PD-L1 in the breast cancer microenvironment and could inform novel therapeutic strategies through targeting tumor-surrounding adipose tissue for treating breast cancer.

A phosphotyrosine switch controls antitumor activity of estrogen receptor b

Recently, we identified a phosphotyrosine residue in human ERb (pY36), which is highly conserved in all mammalian ERb orthologs, but not present in ERa. In addition, this phosphotyrosine switch in ERb controls its tumor-intrinsic (tumor cells) activity. However, the weakness of the current literature concerns limited information about the ERb tumor-extrinsic antitumor activity. To investigate ERb tumor-extrinsic antitumor activity, we generated a whole-body knock-in (KI) mouse model in which the tyrosine residue Y55 of endogenous mouse ERb, which corresponds to Y36 of human ERb, is mutated to phenylalanine (Y55F). We found that B16 melanoma grew more robustly in KI recipient mice than in their WT counterparts, as well as MC38 and M-Wnt tumor models. These data demonstrate that the phosphotyrosine switch is important for ERb tumor-extrinsic antitumor activity in multiple tumor types and in both sexes of recipient mice. In the following mouse bone marrow chimera experiment, we found B16 melanoma growth was significantly faster in KI&gt;WT chimeras versus male WT&gt;WT control. This suggests that KI-derived immune cells poorly deterred tumor growth. Analysis with enriched subpopulations of immune cells from spleen, CD8 T cells have ERb protein expression. Adoptive transfer of CD8 T cells from WT donor but not KI donor significantly reduced tumor growth in Rag1 KO mice, a function attributed to reduced infiltration of KI CD8 T cells into tumors. Accordingly, increased infiltration of CD8 T cells was positively associated with ESR2 expression in various cancer types from TCGA datasets, including breast cancer and melanoma.

Distinct responses to αPD-1, αPD-L1 and αPD-L2 immunotherapy in aged versus young hosts includes T-cell stem cell effects and PD-L2 expression differences

Aging is the biggest risk factor for cancer, yet little is known about how it affects cancer immunotherapy. Melanoma response to αPD-1/αPD-L1 correlates with CD8+ TCF-1+ T cell stem cell (TCSC) generation. We tested αPD-1 (100 μg/mouse), αPD-L1 (100 μg/mouse) or αPD-L2 (200 μg/mouse) in aged (18–24 months) and young (3–8 months) mice challenged orthotopically with B16 melanoma (SQ) or ID8agg ovarian cancer (IP). Tumors and draining lymph nodes (TDLN) were analyzed by flow. We previously reported that αPD-1 treats young and aged with B16 and αPD-L1 only treats young. αPD-L2 treated B16 in aged but not young, the first single agent cancer immunotherapy exhibiting this property. Preliminary data indicate survival benefit of αPD-L2 against ID8agg in aged but not young mice. Aged mice tolerated all treatments comparable to young. B16 efficacy in young (αPD-1, αPD-L1) and aged (αPD-1, αPD-L2) correlated with increased TCSC and total TIL, but TCSC differed by age and treatment. PD-1 interacts with PD-L1 and PD-L2 while PD-L1 interacts with PD-1 and CD80. Aged mice expressed significantly more T-cell PD-1 and PD-L2 and up to 40-fold more PD-L2, PD-L1 and CD80 vs. young on myeloid cells and NK cells. We generated bone marrow-derived DC with GM-CSF. Aged DC expressed much high PD-L2 versus young, suggesting a cell-intrinsic PD-L2 age bias. Treatment differences in aged versus young could depend on these immune checkpoint or TCSC differences. We are now identifying mechanisms for increased PD-L2 and contributions to αPD-L2 efficacy in aged, and testing TCSC effects on treatments. Our work can improve cancer immunotherapy in aged hosts and provide models for treatment resistance in young hosts.

CD122-selective IL-2 complexes target γδ T and NK cells to reduce tumor-promoting Th17 effects and synergize with αPD-L1 to treat primary and metastatic bladder cancer

αPD-L1 bladder cancer (BC) immunotherapy is effective in &lt;30% of cases. To address the large αPD-L1-unresponsive subset of patients, we tested αIL-2/IL-2 complexes (IL-2c) that block IL-2 from binding high-affinity IL-2Rα (CD25) for preferential IL-2Rβ (CD122) binding. Regulatory T cells (Tregs) capture IL-2 by CD25 whereas CD8+T, γδ T, and NK cells use CD122. We hypothesized that the tumor microenvironment, including local immune cells in primary versus metastatic BC, differentially affects immunotherapy responses. We used PD-L1+ mouse BC cell lines MB49 and MBT-2, for intravesical ([IVe] in bladder) and intravenous (IV) challenge studies of local versus metastatic BC. αPD-L1 or IL-2c alone reduced tumor burden and extended survival in IVe MB49 and MBT-2. Treg depletion using FOXP3DTR mice further enhanced IVe IL-2c effects, consistent with the known tumor-promoting role of Tregs in human BC. Using in vivo cell depletion approaches, we found that γδ T cells and NK cells, but not CD8+ T cells, were necessary for IL-2c efficacy in bladder. γδ T cells also reduced intratumoral Th17 cells that promote MB49 growth and are elevated in human BC. We confirmed γδ T cell effects in δ TCR KO mice, which abrogated IL-2c efficacy but not αPD-L1 efficacy. Neither αPD-L1 nor IL-2c alone treated metastatic MB49 and MBT-2 BC but the combination improved survival in both. These data are consistent with our recent findings in human BC patients in whom γδ T cell and NK cell cytotoxicity improved BCG immunotherapy. Thus, IL-2c is a promising novel BC immunotherapy that can improve bladder-specific immunity in primary BC. In metastatic BC, combination with αPD-L1 may also be a successful BC treatment strategy due to engagement of innate and adaptive immune responses.

Tumor cell-intrinsic PD-L1 signals promote DNA damage responses that mediate resistance to Chk1 and PARP inhibitors in vivo

Tumor PD-L1 mediates diverse cell-intrinsic signals that increase cancer pathogenesis including the DNA damage response (DDR). Although immune consequences of tumor-extrinsic PD-L1 blockade are known, novel therapeutic vulnerabilities from inhibiting tumor-intrinsic PD-L1 signals are little studied. To assess tumor-intrinsic PD-L1 DDR control, we depleted PD-L1 by CRISPR/Cas9 or shRNA (PD-L1KO) in mouse B16 (melanoma), 4T1 (breast), ID8agg (ovarian), and human bladder RT4 cancer lines. We identified specific DDR signaling defects in PD-L1KO versus control (con) cells after exposure to distinct DNA damaging agents. 24h gemcitabine (or 2 Gy X-ray) in vitro in PD-L1KO vs. con RT4 cells elevated γH2AX (DNA damage marker) and reduced Chk2 DDR gene expression but not ATM, ATR, Chk1, or BRCA1 (immunoblots), and decreased BRCA1/p-RPA32 nuclear foci formation (confocal) altogether suggesting tumor-intrinsic PD-L1 promotes specific DDR/DNA repair pathways. PD-L1 loss could thus predict synthetic lethality to DDR inhibitors (DDRi) Chk1i or PARPi. PD-L1KORT4, ID8, and 4T1 cells were more sensitive to small molecule Chk1i in vitro (&gt;15 fold vs. con, MTT) and in vivo in NSG mice. Chk1i and PARPi led to γH2AX increase in PD-L1KO B16, RT4, and 4T1 vs. sham treated tumor cells as predicted by DDR defects. Genetic cellular PD-L1 depletion, but not anti-PD-L1 (extrinsic), strongly sensitized B16 and 4T1 tumors to PARPi in vivo. Strikingly, PARPi had no effect on PD-L1KO B16 in RAG2KO mice despite treating WT mice, indicating a strong immune component to DDRi treatment efficacy. Thus, DDRi plus inhibiting tumor intrinsic PD-L1 signals could improve immunotherapy in immunotherapy-sensitive or resistant tumors.

CCL2/CCR2 signaling protects against bladder cancer growth in a T cell dependent manner

The chemokine CCL2 (C-C motif ligand 2) is an important signaling axis underlying recruitment of pro-tumorigenic myeloid cells and is associated with worse outcomes in several tumor models. Currently, anti-CCL2 antibodies are being tested in cancer trials for solid tumors. To test CCL2 signaling in bladder carcinogenesis, wild type (WT) mice and mice deficient in CCL2 (CCL2KO) were given the urothelial carcinogen N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN). Surprisingly, tumor incidence was higher in CCL2KO mice demonstrating an unanticipated protective role for CCL2 signaling in bladder cancer (BC). We then orthotopically challenged WT, CCL2KO, and CCR2KO mice (lacking the major CCL2 receptor) with MB49 BC and confirmed the protective effect of CCL2/CCR2. WT mice had significantly more intratumoral T cells compared to CCL2KO mice suggesting that CCL2 is involved in recruiting T cells to the bladder. Further, depletion of T cells abolished this protective effect of CCL2. Adoptive transfer of CCR2+ T cells into CCR2KO mice restored protection against MB49. CCR2+ T cells were also more activated, functional and tumor specific compared to their CCR2− counterparts. We found that anti-CCL2 promotes BC growth highlighting a concern for use of anti-CCL2 in BC. Moreover, intravesical recombinant CCL2 (rCCL2) either alone or in combination with intravesical gemcitabine reduced bladder tumor and improved survival of mice with MB49 BC. We further developed a slow-release encapsulated nanoparticle formulation of rCCL2 which successfully treated MB49, C3H mice with MBT-2 BC and reduced urine hematuria in our first ever humanized model of orthotopic BC. Our results are rapidly translatable and identify a novel treatment strategy in BC.

PPARγ inhibition boosts efficacy of PD-L1 Checkpoint Blockade Immunotherapy against Murine Melanoma in a sexually dimorphic manner

Immune checkpoint blockade-based immunotherapy has become standard of care for multiple cancer types. However, the overall response rates among various cancer types still remain unsatisfactory. There is a pressing clinical need to identify combination therapies to improve efficacy of anticancer immunotherapy. We previously showed that pharmacologic inhibition of PPARγ by GW9662 boosts αPD-L1 and αPD-1 antibody efficacy in treating murine mammary tumors. In addition, we defined sexually dimorphic αPD-L1 efficacy in B16 melanoma. Here, we show a sexually dimorphic response to the combination of GW9662 and αPD-L1 immunotherapy in B16 melanoma. Combination effects were observed in female, but not male hosts. Neither female oöphorectomy impairs, nor does male castration rescue the combination effects, suggesting a sex hormone-independent response to this combination therapy. In diet-induced obese females, melanoma growth remained responsive to the combination treatment, albeit less robustly than lean females. These findings are informative for future design and application of immunotherapy-related combination therapy for treating human melanoma patients by taking gender and obesity status into consideration.

Percutaneous BCG enhances innate effector antitumor cytotoxicity during treatment of bladder cancer: a translational clinical trial

Background: Intravesical bacillus Calmette-Guérin (BCG) is the gold standard immunologic agent for treating patients with high-grade non-muscle invasive bladder cancer (NMIBC). Nevertheless, relapse rates remain high and BCG unresponsive NMIBC often requires bladder removal. Preclinical data suggest that priming with percutaneous BCG vaccine could improve response to intravesical BCG. Methods: A single-arm trial (NCT02326168) was performed to study the safety, immunogenicity, and preliminary efficacy of priming. Percutaneous BCG was given 21 days prior to intravesical BCG instillation in patients (n = 13) with high-risk NMIBC. Immune responses were monitored and compared to a sequentially enrolled cohort of nine control patients receiving only intravesical BCG. The effect of BCG on natural killer (NK) and γδ T cell in vitro cytotoxicity was tested. γδ T cell subsets were determined by T cell receptor gene expression with NanoString. Results: Priming was well tolerated and caused no grade ≥3 adverse events. The 3-month disease-free rate for prime patients was 85% (target goal ≥ 75%). Priming boosted BCG-specific immunity at 3 months and increased the activation status of in vitro expanded circulating NK and γδ T cells and their cytotoxicity against bladder cancer cells through receptor NKG2D. BCG enhanced the cytotoxicity of NK and γδ T cells against K562, RT4, and UM-UC6 but not against T24, UM-UC-3, or UM-UC-14 cells. Infiltrating γδ T cell subsets identified in the bladder includes γ9δ2 and γ8δ2. Conclusions: BCG priming is safe and tolerable. Poor sensitivity to NK and γδ T cell cytotoxicity by some bladder tumors represents a potential BCG-resistance mechanism.

Cell-intrinsic programmed death ligand-1 (PD-L1) inhibits cytotoxic chemo, promotes DNA damage repair, and enhances ATM/ATR signaling following exposure to DNA damaging agents in bladder, melanoma, and ovarian cancer cells

We have shown that cancer cell-intrinsic PD-L1 signals increase mTORC1 and unbundle actin. To test if tumor cell PD-L1 affects the DNA damage response (DDR) we made PD-L1KO mouse ID8agg (ovarian) and B16 (melanoma), and human bladder RT4 cancer lines. The DNA damaging agent gemcitabine (gem) reduced PD-L1KO ID8agg and RT4 viability in vitro vs. control (con) (ID8agg: 29X vs. 1.3X; RT4: 2X vs 1.1X). 4h gem increased phospho (p)-γH2AX, a marker of DNA double strand breaks: 2X in PD-L1KO vs. con RT4. P-γH2AX stayed abnormally high after gem removal, further showing defective DDR in PD-L1KO. 24h gem also induced more p-γH2AX in PD-L1KO vs. con ID8agg, and 48h gem induced more apoptosis in PD-L1KO vs. con RT4. Cisplatin, a DNA damaging agent distinct from gem, reduced PD-L1KO ID8agg viability 9X vs. 2X in con. No viability difference was seen in cisplatin treated PD-L1KO vs. con RT4. Thus, PD-L1 chemo resistance effects are cell type and/or agent specific. To define DDR mechanism(s), we found that 24h gem decreased p-Chk2 (ATM DDR pathway), due to reduced total Chk2, but not p-Chk1 or total Chk1 (ATR DDR pathway) in PD-L1KO vs. con RT4. 20 Gy X-rays (DNA damage distinct vs. gem), reduced p-Chk1 in PD-L1KO but not con B16 and induced less p-RPA32 in PD-L1KO vs. con B16, suggesting defects specifically in homologous recombination mediated DNA repair. Thus, cell-intrinsic PD-L1 DDR control is insult and/or cell type specific. RT4 DDR effects were independent of mTOR or actin. DDR affects immunotherapy so PD-L1 cell-intrinsic DDR control could be exploited in treatment or response biomarkers. DDR inhibitors, chemo or radiation combos could improve anti-PD-L1 efficacy in distinct cancers, subjects of ongoing work, as is testing tumor cell intrinsic PD-1 effects.

Tumor-intrinsic PD-L1 reduces actin cytoskeleton polymerization to promote mTORC1 signals driving tumor stemness

Tumor-intrinsic PD-L1 signals contribute to tumor virulence and pathology, but mechanisms are poorly understood. We previously showed that tumor-intrinsic PD-L1 increases mTORC1 and tumor initiating cell (TIC) generation and function in ovarian cancer and melanoma. We used CRISPR/Cas9 (KO) and shRNA (lo) to reduce PD-L1 in mouse melanoma (B16) and ovarian cancer (ID8agg), and human ovarian cancer (ES2). PD-L1lo reduced mTORC1 and TIC as expected, but unexpectedly increased actin polymerization and filopodia, and altered cell morphology. The actin depolymerizing agents Latrunculin-A or Cytochalasin-D reversed actin polymerization in PD-L1lo ID8agg cells and increased mTORC1 (p-rpS6) without affecting mTORC2 (pAktS473). Latrunculin-A and Cytochalasin-D increased TIC numbers and stemness gene expression (Oct4) in PD-L1lo ID8agg cells with no effect on control ID8agg cells. Similar actin effects were seen in PD-L1KO B16 and PD-L1KO ES2. To confirm TIC function, Latrunculin-A increased tumorospheres (TIC self-renewal function) in PD-L1lo, but not control ID8agg cells. The mTORC1 inhibitor rapamycin reduced TIC numbers and functions with no effect on actin polymerization, suggesting mTORC1 is downstream of actin polymerization. Rptorlo ID8agg cells (with low mTORC1 signaling) did not exhibit the PD-L1lo actin polymerization, nor did Latrunculin-A increase Rptorlo ID8agg TIC numbers, tumorospheres, or stemness genes, confirming the flow of signals is PD-L1 to actin to mTORC1 to TIC (stemness). Our data define a highly novel tumor virulence control mechanism of cell-intrinsic PD-L1 through inhibiting actin polymerization suggesting new drug discovery targets. Preliminary data show some similar effects of tumor PD-1.

Tumor-intrinsic PD-L1 regulates tumor initiating cell virulence and stemness genes, and TCF1+ stem-like T cells through Raptor in ovarian cancer, which correlates with survival in high grade serous ovarian cancer

We reported that tumor intrinsic PD-L1 promotes tumor initiating cell (TIC) virulence and mTORC1. Others have focused on PI3K/AKT/mTOR in promoting TIC, but specific downstream mTOR regulators of tumor stemness are unknown. We knocked down Raptor (mTORC1 component, Rptorlo) in ID8agg cells (murine ovarian cancer). Rptorlo cells had reduced mTORC1 with no change in PD-L1 in total cells or CD44+CD24+ TIC. %TIC was reduced in Rptorlo cell cultures, and Rptorlo TIC were functionally defective for self-renewal by tumorosphere formation. Rapamycin (mTORC1 inhibitor) reduced ID8agg Rptor, tumorospheres, and the stemness and virulence genes Oct4 and Nanog. Oct4 knockin to PD-L1lo ID8agg restored TIC numbers and spheres. Together, data confirm PD-L1 drives stemness through Oct4 by increasing mTORC1. Rptorlo TIC formed significantly smaller tumors vs. control TIC in immunodeficient NSG mice, confirming TIC intrinsic Rptor drives immune independent virulence. In wild type mice, Rptorlo vs. control TIC produced less ascites and smaller tumors with lower %TIC in vivo (but similar PD-L1), significantly more recently-activated CD44hiCD62LloCD8+ cells in ascites and draining lymph nodes (DLN). CCR2+CD8+ T cells and CXCR5+TCF1+PD-1+Tim3− stem-like T cells were also increased in Rptorlo DLN. Thus, Rptorlo TIC influence systemic and tumor-associated immunity. In high grade serous ovarian tumors (The Cancer Genome Atlas) high Rptor expression predicted a significantly higher cancer stem cell signature, and lower median survival in late stage patients. Our work establishes tumor intrinsic Rptor driven by PD-L1 plays a key role in regulating TIC and stem like T cells and can be a prognostic marker for late stage ovarian cancer patients.

CD122-selective IL-2 complexes treat ovarian carcinomas and melanoma, alter Treg differentiation and induce more CD8+CXCR5+TCF-1+ stem T cells when combined with αPD-L1

Anti-tumor T cells (Teffs) engage IL2 largely through CD122, vs. CD25 for regulatory T cells (Tregs). In ID8agg ovarian cancer (OC), CD122-selective IL2 complexes (IL2c, made from CD122-blocking ab+IL-2), increased Teff numbers and functions as expected but unexpectedly reduced tumor Treg function, with near-complete tumor rejection in OC. IL2c reduced lineage specific molecules (e.g., Tbet) and cytokines (e.g., IFNg) in tumor Tregs, suggesting IL2c improves Treg differentiation, but not explaining IL2c-driven Treg defects. In vitro, IL-2 and IL-2c produced similar Treg numbers and Foxp3 from naïve CD4+T cells, with functional data pending. αPD-L1 improved IL2c efficacy for full tumor rejection in OC and B16 melanoma. Increased CD8+CXCR5+PD1+Tim3−TCF-1+stem-like T cells (CXCR5+) are associated with favorable αPD-1 or αPD-L1 outcome in mice and humans. IL2c + αPD-L1 markedly increased CXCR5+in B16 melanoma and to a lesser extent in OC. IL2c + αPD-L1 increased tumor CXCR5+perforin expression in B16 vs. either single agent. Injecting tumor-infiltrating CXCR5+into RagKO mice produced CXCR5+Tim3− and CXCR5−Tim3+cells confirming tumor CXCR5+stem cell properties. These data demonstrate several novel IL2c mechanisms to exploit in distinct cancers and treatment combinations. Ongoing work tests IL2c, αPD-L1 and combo treatment effects on CXCR5+ stemness and mechanisms for CXCR5+ induction, and mechanisms for IL2c-driven Treg dysfunction.

Surface and cytoplasmic tumor cell PD-L1 differentially mediate virulence in ovarian cancer and melanoma through mTOR activation

Tumors express intracellular PD-L1 that we showed increases ovarian cancer (OC) and melanoma virulence by increasing mTORC1 and tumor stem cells (TSC). We made PD-L1KO(CRISPR) in ES2 human OC and B16 melanoma cells and re-expressed PD-L1 only on cell surface (PD-L1surf) or in cytoplasm (PD-L1cyto) with specific expression vectors. Subcellular PD-L1 location in all clones was validated by immunoblots, confocal microscopy, and co-IP/mass spec. We selected clones with PD-L1 surf or cyto expression similar to parental cells. PD-L1KO reduced cell diameter 30% which was restored partially in PD-L1surf and fully in PD-L1cyto in ES2 and B16. PD-L1KO significantly decreased viability in all cell lines tested which was fully rescued in PD-L1surf and PD-L1cyto. PD-L1surf ES2 and B16 grew slower in vitro and in vivo than PD-L1cyto and only PD-L1cyto rescued F-actin polymerization phenotype seen in PD-L1KO ES2 and B16. RNA-seq showed that surf and cyto PD-L1 differentially altered canonical signaling pathways, notably mTOR, stemness and gene regulation. PD-L1cyto grew much slower than PD-L1surf B16 in NSG mice but generated more TSC in vitro, and PD-L1surf but not PD-L1cyto B16 responded to αPD-L1 in WT. PD-L1cyto but not PD-L1surf induced mTORC1 activation (p-rpS6, p-P70S6K) through mTORC1 lysosomal docking through LAMTOR1/2 seen by confocal and confirmed by co-IP in ES2 and B16. Imaging CyTOF of human melanomas showed PD-L1cyto association with activated mTOR. Thus, surf versus cyto PD-L1 differentially affects tumor biology, signaling, pathology, TIL and treatment response in OC and melanoma. We define a mechanism for PD-L1-driven mTORC1 activation. Surface vs. cytoplasmic PD-L1 and/or mTORC1 could be response biomarkers for αPD-L1 or αPD-1.

Adipocyte PD-L1 Modulates PD-1/PD-L1 Checkpoint Blockade Cancer Immunotherapy Efficacy

PD-L1 expression in both tumor and host cells correlates with antitumor therapeutic efficacy, but the specific contribution of PD-L1 in various cell compartments to antitumor immunity remains to be fully elucidated. Here we show that PD-L1 expression is significantly elevated in human and mouse mature adipocytes versus preadipocytes. When co-cultured with mouse splenocytes, adipocytes reduce αPD-L1 antibody-mediated CD8+T cell activation. Genetic ablation of adipose PD-L1 obliterates, while enforced PD-L1 expression in preadipocytes confers, the immune-inhibitory effect of adipocytes. Pharmacologic inhibition of adipogenesis by the PPARγ antagonist GW9662 reduces adipose PD-L1 expression and enhances the antitumor efficacy of αPD-L1 and αPD-1 immunotherapies in female mice bearing syngeneic melanoma or mammary tumors. Combo treatment with GW9662 and αPD-L1 increased antitumor lymphocytes infiltration versus control or single agent treatment. In diet-induced obese female mice, combo treatment elicited suppressed melanoma growth, although less effectively versus lean females. In contrast to females, melanomas in either lean or obese male mice exhibited no applicable response to combo treatment. More strikingly, obese males lost αPD-L1 single treatment response versus lean males, with lower CD45+and CD3+T cell infiltration in tumors. However, castration in lean males rescued efficacy of combo treatment. These data suggest an antagonistic effect of male hormones in this combination. The potential impact of sex and obesity warrants consideration in future development of immunotherapy-related combination therapy.

HIV infection induces CD44+PD-L1+ tumor initiating cells in AIDS associated non-AIDS defining cancers

The antiretroviral therapy (ART) significantly increased the number of aging HIV patients and the non-AIDS defining cancers (NADC) have become the most frequent co-morbidity and causes of death among HIV patients. The role of HIV infection in cancer initiation and progression is unclear. Tumor initiating cells (TIC) are responsible for chemo-resistance, metastasis and mortality. Our previous work demonstrated that tumor-intrinsic PD-L1 correlate with proportion (%) of TIC and virulence. Supernatants from HIV infected peripheral blood lymphocyte (PBMC) cultures (HIV-sup) significantly increased % TIC (CD44+PD-L1+) in two human tumor cell lines-SCC4 (squamous carcinoma) and HeLa (cervical cancer). HIV single stranded RNA (ssRNA) binds TLR7/8, and leads to immune activation and inflammation. The Cancer Genome Atlas database analyses showed that squamous cancer and cervical adenocarcinoma patients with TLR7/8 amplification had significantly poor overall survival. TLR7 agonist R848 led to significant increase in % TIC, whereas treatment of the cancer cells with HIV-sup in presence of TLR7/8 inhibitor ODN2088 reversed this effect. Similarly, pharmacological inhibition (by ACHP) of TLR7/8 mediated NFkB signaling pathway decreased TIC % two-fold, confirming HIV mediated TLR7/8 signaling has pro-TIC effects. High levels of inflammatory cytokine IFNα correlates with HIV load and persistent infection. Treatment with IFNα led to a significant increase in TIC whereas blocking IFNα-induced JAK signaling by ruxolitinib, in presence of HIV-sup reduced TIC significantly. Thus, our novel data gives insight into HIV induced host-pathogen interactions that lead to TIC prevalence.

Selective IL-2 receptor β (CD122) targeting improves αPD-L1 immunotherapy in a metastatic bladder cancer model

αPD-L1 is an FDA-approved bladder cancer (BC) immunotherapy but is effective in ≤30% of cases. We tested conjugates of αIL-2 antibody + IL-2 (IL-2c) that block IL-2 from binding high-affinity IL-2Rα (CD25) for preferential IL-2Rβ(CD122) binding. CD25 and CD122 are preferred for IL-2 capture by regulatory T cells and anti-tumor effector T cells (Teff), respectively, allowing IL-2c to target Teff preferentially. Orthotopic, intravesical (in bladder) MB49 BC produces PD-L1+BC tumors in syngeneic BL6 mice. αPD-L1 or IL-2c treated intravesical, but not lung metastatic MB49 produced by intravenous injection. Still, in metastatic BC, αPD-L1 + IL-2c (combo) reduced lung metastases and extended survival. Preliminary data found combo treatment efficacy was better in lung versus bladder. In subcutaneous (SQ) B16 melanoma, combo was better than single agents, and increased CD8+CXCR5+TCF-1+Tim-3−PD-1+T stem cells (CXCR5+SC, see X. Zhang poster) vs. single agents. Neither αPD-L1 nor combo increased CXCR5+SC in MB49 in bladder or lung metastases, suggesting a novel treatment mechanism. To test the impact of tumor PD-L1 on treatment efficacy, we made PD-L1KOMB49, but it did not grow in bladder or SQ in wild type mice, but grew similar to control MB49 in immunodeficient NSG mice SQ, suggesting tumor PD-L1 microenvironment-specific effects. PD-L1KOB16 grew well SQ in wild type mice, excluding a PD-L1-specific defect. Thus, tumor PD-L1 differs in immune evasion in a tumor-dependent manner. Selective IL-2 targeting to CD122 improves αPD-L1 treatment of metastatic BC. Mechanisms differ from melanoma, which could be due to tumor, PD-L1, or microenvironment effects. We are assessing mechanisms and αPD-1 treatment effects (also FDA-approved for BC).