Cytokine-armed dendritic cell progenitors for antigen-agnostic cancer immunotherapy

Dendritic cells (DCs) are antigen-presenting myeloid cells that regulate T cell activation, trafficking and function. Monocyte-derived DCs pulsed with tumor antigens have been tested extensively for therapeutic vaccination in cancer, with mixed clinical results. Here, we present a cell-therapy platform based on mouse or human DC progenitors (DCPs) engineered to produce two immunostimulatory cytokines, IL-12 and FLT3L. Cytokine-armed DCPs differentiated into conventional type-I DCs (cDC1) and suppressed tumor growth, including melanoma and autochthonous liver models, without the need for antigen loading or myeloablative host conditioning. Tumor response involved synergy between IL-12 and FLT3L and was associated with natural killer and T cell infiltration and activation, M1-like macrophage programming and ischemic tumor necrosis. Antitumor immunity was dependent on endogenous cDC1 expansion and interferon-γ signaling but did not require CD8+ T cell cytotoxicity. Cytokine-armed DCPs synergized effectively with anti-GD2 chimeric-antigen receptor (CAR) T cells in eradicating intracranial gliomas in mice, illustrating their potential in combination therapies.

Dendritic cell cross-dressing and tumor immunity

In addition to direct and cross‐presentation, dendritic cells (DCs) can present tumor antigens (TAs) to T cells via a hitherto poorly understood mechanism called “cross‐dressing.” DC cross‐dressing involves the acquisition of preformed peptide‐major histocompatibility class I/II (p‐MHC) complexes from cancer cells. This process has been documented both in cell culture and in tumor models; may occur via the uptake of tumor‐derived extracellular vesicles or the horizontal transfer of plasma membrane fragments from cancer cells to DCs; and can be enhanced through DC engineering for therapeutic applications. In some experimental contexts, DC cross‐dressing may be essential for productive anti‐tumor immunity, possibly owing to the fact that tumor‐derived p‐MHC complexes encompass the full repertoire of immunologically relevant TAs against which primed cytotoxic T cells can exert their tumoricidal activity.

Overcoming microenvironmental resistance to PD-1 blockade in genetically engineered lung cancer models

Immune checkpoint blockade (ICB) with PD-1 or PD-L1 antibodies has been approved for the treatment of non-small cell lung cancer (NSCLC). However, only a minority of patients respond, and sustained remissions are rare. Both chemotherapy and antiangiogenic drugs may improve the efficacy of ICB in mouse tumor models and patients with cancer. Here, we used genetically engineered mouse models of Kras ^G12D/+;p53 ^-/- NSCLC, including a mismatch repair-deficient variant (Kras ^G12D/+;p53 ^-/-;Msh2 ^-/-) with higher mutational burden, and longitudinal imaging to study tumor response and resistance to combinations of ICB, antiangiogenic therapy, and chemotherapy. Antiangiogenic blockade of vascular endothelial growth factor A and angiopoietin-2 markedly slowed progression of autochthonous lung tumors, but contrary to findings in other cancer types, addition of a PD-1 or PD-L1 antibody was not beneficial and even accelerated progression of a fraction of the tumors. We found that antiangiogenic treatment facilitated tumor infiltration by PD-1⁺ regulatory T cells (T_regs), which were more efficiently targeted by the PD-1 antibody than CD8⁺ T cells. Both tumor-associated macrophages (TAMs) of monocyte origin, which are colony-stimulating factor 1 receptor (CSF1R) dependent, and TAMs of alveolar origin, which are sensitive to cisplatin, contributed to establish a transforming growth factor-β-rich tumor microenvironment that supported PD-1⁺ T_regs Dual TAM targeting with a combination of a CSF1R inhibitor and cisplatin abated T_regs, redirected the PD-1 antibody to CD8⁺ T cells, and improved the efficacy of antiangiogenic immunotherapy, achieving regression of most tumors.

Abstract 75: Determinants of tumor resistance to anti-angiogenic immunotherapy in mouse models of Kras-mutant NSCLC

Immune checkpoint blockade (ICB) with PD-1 or PD-L1 antibodies has been approved for the treatment of non-small cell lung cancer (NSCLC), often in combination with chemotherapy. However, only a minority of the patients respond and sustained remissions are rare. Anti-angiogenic therapy improves tumor response to ICB in mouse models of cancer and in patients with EGFR-mutant NSCLC, but the contribution of anti-angiogenic therapy to the clinical efficacy of ICB in patients with KRAS-mutant NSCLC remains unclear. We used genetically engineered mouse models of KrasG12D/p53null NSCLC, including a mismatch repair-deficient variant (KrasG12D/p53null/Msh2null) with higher mutational burden, and longitudinal imaging of individual tumors to study tumor response and resistance to combinations of ICB, anti-angiogenic therapy, and cisplatin chemotherapy. We found that anti-angiogenic blockade of VEGFA and angiopoietin-2 (ANGPT2) with the bispecific antibody A2V was superior to single VEGFA inhibition and markedly slowed tumor progression. But, contrary to findings in other tumor models, the addition of a PD1 antibody to A2V did not provide additive benefits and even accelerated growth of a fraction of the tumors. We implicated tumor-associated macrophages (TAMs) and PD-1+regulatory T cells (T-regs) in this growth-promoting response, and identified a pre-clinical strategy involving the differential targeting of two distinct TAM subsets that unleashed the therapeutic potential of anti-angiogenic immunotherapy and achieved regression of more than 80% of the lung tumors.

Citation Format: Amaia Martinez-Usatorre, Ece Kadioglu, Chiara Cianciaruso, Alan Guichard, Bruno Torchia, Sina Nassiri, Martina Schmittnaegel, Carola H. Ries, Etienne Meylan, Ioanna Keklikoglou, Michele De Palma. Determinants of tumor resistance to anti-angiogenic immunotherapy in mouse models of Kras-mutant NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 75.

An Immunomodulatory Gallotanin-Rich Fraction From Caesalpinia spinosa Enhances the Therapeutic Effect of Anti-PD-L1 in Melanoma

PD-1/PD-L1 pathway plays a role in inhibiting immune response. Therapeutic antibodies aimed at blocking the PD-1/PD-L1 interaction have entered clinical development and have been approved for a variety of cancers. However, the clinical benefits are reduced to a group of patients. The research in combined therapies, which allow for a greater response, is strongly encouraging. We previously characterized a polyphenol-rich extract from Caesalpinia spinosa (P2Et) with antitumor activity in both melanoma and breast carcinoma, as well as immunomodulatory activity. We hypothesize that the combined treatment with P2Et and anti-PD-L1 can improve the antitumor response through an additive antitumor effect. We investigated the antitumor and immunomodulatory activity of P2Et and anti-PD-L1 combined therapy in B16-F10 melanoma and 4T1 breast carcinoma. We analyzed tumor growth, hematologic parameters, T cell counts, cytokine expression, and T cell cytotoxicity. In the melanoma model, combined P2Et and anti-PD-L1 therapy has the following effects: decrease in tumor size; increase in the number of activated CD4⁺ and CD8⁺ T cells; decrease in the number of suppressor myeloid cells; increase in PD-L1 expression; decrease in the frequency of CD8⁺ T cell expressing PD-1; improvement in the cytotoxic activity of T cells; and increase in the IFN γ secretion. In the breast cancer model, P2Et and PD-L1 alone or in combination show antitumor effect with no clear additive effect. This study shows that combined therapy of P2Et and anti-PD-L1 can improve antitumor response in a melanoma model by activating the immune response and neutralizing immunosuppressive mechanisms.

A LIGHTning Strike to the Metastatic Niche

Tumor-induced vascular alterations in distant organs have been linked to the spreading of cancer. In this issue of Cell Reports, He et al. (2019) show that targeting the cytokine LIGHT to the pulmonary vasculature prevents the establishment of lung metastasis in mice.

Enhanced Phenotype Definition for Precision Isolation of Precursor Exhausted Tumor-Infiltrating CD8 T Cells

In the context of adoptive T cell transfer (ACT) for cancer treatment, it is crucial to generate in vitro large amounts of tumor-specific CD8 T cells with high potential to persist in vivo. PD-1, Tim3, and CD39 have been proposed as markers of tumor-specific tumor-infiltrating CD8 T lymphocytes (CD8 TILs). However, these molecules are highly expressed by terminally differentiated exhausted CD8 T cells (Tex) that lack proliferation potential. Therefore, optimized strategies to isolate tumor-specific TILs with high proliferative potential, such as Tcf1+ precursor exhausted T cells (Tpe) are needed to improve in vivo persistence of ACT. Here we aimed at defining cell surface markers that would unequivocally identify Types for precision cell sorting increasing the purity of tumor-specific PD-1+ Tcf1+ Tpe from total TILs. Transcriptomic analysis of Tpe vs. Tex CD8 TIL subsets from B16 tumors and primary human melanoma tumors revealed that Tpes are enriched in Slamf6 and lack Entpd1 and Havcr2 expression, which encode Slamf6, CD39, and Tim3 cell surface proteins, respectively. Indeed, we observed by flow cytometry that CD39- Tim3- Slamf6+ PD-1+ cells yielded maximum enrichment for tumor specific PD-1+ Tcf1+ OT1 TILs in B16.OVA tumors. Moreover, this population showed higher re-expansion capacity upon an acute infection recall response compared to the CD39+ counterparts or bulk PD-1+ TILs. Hence, we report an enhanced sorting strategy (CD39- Tim3- Slamf6+ PD-1+) of Tpes. In conclusion, we show that optimization of CD8 TIL cell sorting strategy is a viable approach to improve recall capacity and in vivo persistence of transferred cells in the context of ACT.

miR-155 Overexpression in OT-1 CD8+ T Cells Improves Anti-Tumor Activity against Low-Affinity Tumor Antigen

Therapy by adoptive transfer of ex vivo-expanded tumor-infiltrating or genetically modified T cells may lead to impressive clinical responses. However, there is a need to improve in vivo persistence and functionality of the transferred T cells, in particular, to face the highly immunosuppressive environment of solid tumors. Here, we investigate the potential of miR-155, a microRNA known to play an important role in CD8⁺ T cell fitness. We show that forced expression of miR-155 in tumor antigen-specific T cells improves the tumor control of B16 tumors expressing a low-affinity antigen ligand. Importantly, miR-155-transduced T cells exhibit increased proliferation and effector functions associated with a higher glycolytic activity independent of exogenous glucose. Altogether, these data suggest that miR-155 may optimize the antitumor activity of adoptively transferred low-affinity tumor-infiltrating lymphocytes (TILs), in particular, by rendering them more resistant to the glucose-deprived environment of solid tumors. Thus, transgenic expression of miR-155 may enable therapeutic targeting of self-antigen-specific T cells in addition to neoantigen-specific ones.

MicroRNA-155 Expression Is Enhanced by T-cell Receptor Stimulation Strength and Correlates with Improved Tumor Control in Melanoma

microRNAs are short noncoding RNAs that regulate protein expression posttranscriptionally. We previously showed that miR-155 promotes effector CD8⁺ T-cell responses. However, little is known about the regulation of miR-155 expression. Here, we report that antigen affinity and dose determine miR-155 expression in CD8⁺ T cells. In B16 tumors expressing a low-affinity antigen ligand, tumor-specific infiltrating CD8⁺ T cells showed variable miR-155 expression, whereby high miR-155 expression was associated with more cytokine-producing cells and tumor control. Moreover, anti-PD-1 treatment led to both increased miR-155 expression and tumor control by specific CD8⁺ T cells. In addition, miR-155 overexpression enhanced exhausted CD8⁺ T-cell persistence in the LCMV cl13 chronic viral infection model. In agreement with these observations in mouse models, miR-155 expression in human effector memory CD8⁺ T cells positively correlated with their frequencies in tumor-infiltrated lymph nodes of melanoma patients. Low miR-155 target gene signature in tumors was associated with prolonged overall survival in melanoma patients. Altogether, these results raise the possibility that high miR-155 expression in CD8⁺ tumor-infiltrating T cells may be a surrogate marker of the relative potency of in situ antigen-specific CD8⁺ T-cell responses.

Prophylactic vs. Therapeutic Treatment With P2Et Polyphenol-Rich Extract Has Opposite Effects on Tumor Growth

Polyphenols have tumoricidal effects via anti-proliferative, anti-angiogenic and cytotoxic mechanisms and have recently been demonstrated to modulate the immune response through their anti- or pro- oxidant activity. Nevertheless, it remains controversial whether antioxidant-rich supplements have real beneficial effects on health, especially in complex diseases such as cancer. We previously identified a polyphenol-rich extract obtained from Caesalpinia spinosa (P2Et) with anti-tumor activity in both breast carcinoma and melanoma. The present work evaluated the ability of P2Et extract to modulate the immune system in either the steady state or following tumor challenge. We found that the prophylactic treatment of healthy mice increased the number of CD4⁺ and CD8⁺ activated T, NK, regulatory T, dendritic and myeloid-derived suppressor cells in lymphoid organs together with a significant increase in plasma IL-6. Interestingly, this pre-conditioning of the host immune system with P2Et did not involve a protective effect against the control of tumor growth and metastasis in transplantable models of melanoma (B16) and breast cancer (4T1), but in contrast, a detrimental effect was observed in both models. We further demonstrated that this effect was at least partly due to an increase in regulatory T cells, myeloid-derived suppressor cells, and proinflammatory cytokines, with a concomitant decrease in CD4⁺ and CD8⁺ T cells. Taken together, these results suggest that the anti-tumor and immunomodulation properties of the P2Et extract critically depend on the presence of the tumor and might be mediated by the complex interactions between the tumor cells and the other components of the tumor microenvironment.

Tumour-derived PGD2 and NKp30-B7H6 engagement drives an immunosuppressive ILC2-MDSC axis

Group 2 innate lymphoid cells (ILC2s) are involved in human diseases, such as allergy, atopic dermatitis and nasal polyposis, but their function in human cancer remains unclear. Here we show that, in acute promyelocytic leukaemia (APL), ILC2s are increased and hyper-activated through the interaction of CRTH2 and NKp30 with elevated tumour-derived PGD2 and B7H6, respectively. ILC2s, in turn, activate monocytic myeloid-derived suppressor cells (M-MDSCs) via IL-13 secretion. Upon treating APL with all-trans retinoic acid and achieving complete remission, the levels of PGD2, NKp30, ILC2s, IL-13 and M-MDSCs are restored. Similarly, disruption of this tumour immunosuppressive axis by specifically blocking PGD2, IL-13 and NKp30 partially restores ILC2 and M-MDSC levels and results in increased survival. Thus, using APL as a model, we uncover a tolerogenic pathway that may represent a relevant immunosuppressive, therapeutic targetable, mechanism operating in various human tumour types, as supported by our observations in prostate cancer.Group 2 innate lymphoid cells (ILC2s) modulate inflammatory and allergic responses, but their function in cancer immunity is still unclear. Here the authors show that, in acute promyelocytic leukaemia, tumour-activated ILC2s secrete IL-13 to induce myeloid-derived suppressor cells and support tumour growth.