The Impact of Myeloid-Mediated Co-Stimulation and Immunosuppression on the Anti-Tumor Efficacy of Adoptive T cell Therapy

Adoptive T cell therapy (ACT) in combination with lymphodepleting chemotherapy is an effective strategy to induce the eradication of tumors, providing long-term regression in cancer patients. However, only a minority of patients that receive ACT with tumor infiltrating lymphocytes (TILs) exhibit durable benefit. Thus, there is an urgent need to define strategies that potentiate anti-tumor activity conducted by adoptively transferred T cells. In these studies, we aimed to identify novel strategies to enhance the therapeutic efficacy of ACT. Accordingly, we describe the disparate roles of myeloid cells in the context of ACT characterized by the augmentation of TIL proliferation in the presence of 41BB-mediated co-stimulation and the dampening of anti-tumor immunity orchestrated by myeloid derived suppressor cells (MDSCs). The efficient expansion of T cells is a critical aspect of ACT, which is aided by culturing tumors and TILs in IL-2 and 41BB agonistic antibodies. However, the impact of 41BB-mediated co-stimulation conducted by constituent myeloid cells within tumors on the expansion of TILs is unclear. Here, we describe that the intratumoral administration of 41BB agonistic antibodies led to increases in CD8 T cell infiltration followed by tumor regression in murine models. We found that granulocytes and monocytes rapidly replaced macrophages and dendritic cells in tumors following administration of anti-41BB antibodies. Overall, myeloid cells from anti-41BB treated tumors had an improved capacity to stimulate T cells in comparison to myeloid cells from control treated tumors. In human co-culture systems, we demonstrated that the agonism of the 41BB-41BBL axis enhanced co-stimulatory signals and effector functions among antigen presenting cells and autologous TILs. Thus, myeloid-mediated co-stimulation is a critical factor in potentiating the proliferation of TILs and their anti-tumor activity. Despite that lymphodepleting regimens condition the host for optimal engraftment and expansion of adoptively transferred T cells, lymphodepletion concomitantly promotes immunosuppression during the course of endogenous immune recovery. Here, we have identified that lymphodepleting chemotherapy initiates the mobilization of hematopoietic progenitor cells that differentiate to immunosuppressive myeloid cells, leading to a dramatic increase of peripheral MDSCs. In melanoma and lung cancer patients, MDSCs rapidly expanded in the periphery within one week after completion of a lymphodepleting regimen and infusion of autologous tumor infiltrating lymphocytes (TIL). This expansion was associated with disease progression, poor survival, and reduced TIL persistence in melanoma patients. We demonstrated that the IL-6 driven differentiation of mobilized hematopoietic progenitor cells promoted the survival and immunosuppressive capacity of post-lymphodepletion MDSCs. Furthermore, the genetic abrogation or therapeutic inhibition of IL-6 in mouse models enhanced host survival and reduced tumor growth in mice that received ACT. Thus, the expansion of MDSCs in response to lymphodepleting chemotherapy may contribute to ACT failure and targeting myeloid-mediated immunosuppression may support anti-tumor immune responses. Collectively, we demonstrate that exploiting the immunostimulatory capacity of myeloid cells and the curtailment of myeloid-mediated immunosuppression are strategies that can augment the expansion and anti-tumor activity of TILs. The novel mechanistic insights of these studies highlight the importance of modulating myeloid cells to promote the therapeutic efficacy of ACT

The Impact of Myeloid-Mediated Co-Stimulation and Immunosuppression on the Anti-Tumor Efficacy of Adoptive T cell Therapy

Adoptive T cell therapy (ACT) in combination with lymphodepleting chemotherapy is an effective strategy to induce the eradication of tumors, providing long-term regression in cancer patients. However, only a minority of patients that receive ACT with tumor infiltrating lymphocytes (TILs) exhibit durable benefit. Thus, there is an urgent need to define strategies that potentiate anti-tumor activity conducted by adoptively transferred T cells. In these studies, we aimed to identify novel strategies to enhance the therapeutic efficacy of ACT. Accordingly, we describe the disparate roles of myeloid cells in the context of ACT characterized by the augmentation of TIL proliferation in the presence of 41BB-mediated co-stimulation and the dampening of anti-tumor immunity orchestrated by myeloid derived suppressor cells (MDSCs). The efficient expansion of T cells is a critical aspect of ACT, which is aided by culturing tumors and TILs in IL-2 and 41BB agonistic antibodies. However, the impact of 41BB-mediated co-stimulation conducted by constituent myeloid cells within tumors on the expansion of TILs is unclear. Here, we describe that the intratumoral administration of 41BB agonistic antibodies led to increases in CD8 T cell infiltration followed by tumor regression in murine models. We found that granulocytes and monocytes rapidly replaced macrophages and dendritic cells in tumors following administration of anti-41BB antibodies. Overall, myeloid cells from anti-41BB treated tumors had an improved capacity to stimulate T cells in comparison to myeloid cells from control treated tumors. In human co-culture systems, we demonstrated that the agonism of the 41BB-41BBL axis enhanced co-stimulatory signals and effector functions among antigen presenting cells and autologous TILs. Thus, myeloid-mediated co-stimulation is a critical factor in potentiating the proliferation of TILs and their anti-tumor activity. Despite that lymphodepleting regimens condition the host for optimal engraftment and expansion of adoptively transferred T cells, lymphodepletion concomitantly promotes immunosuppression during the course of endogenous immune recovery. Here, we have identified that lymphodepleting chemotherapy initiates the mobilization of hematopoietic progenitor cells that differentiate to immunosuppressive myeloid cells, leading to a dramatic increase of peripheral MDSCs. In melanoma and lung cancer patients, MDSCs rapidly expanded in the periphery within one week after completion of a lymphodepleting regimen and infusion of autologous tumor infiltrating lymphocytes (TIL). This expansion was associated with disease progression, poor survival, and reduced TIL persistence in melanoma patients. We demonstrated that the IL-6 driven differentiation of mobilized hematopoietic progenitor cells promoted the survival and immunosuppressive capacity of post-lymphodepletion MDSCs. Furthermore, the genetic abrogation or therapeutic inhibition of IL-6 in mouse models enhanced host survival and reduced tumor growth in mice that received ACT. Thus, the expansion of MDSCs in response to lymphodepleting chemotherapy may contribute to ACT failure and targeting myeloid-mediated immunosuppression may support anti-tumor immune responses. Collectively, we demonstrate that exploiting the immunostimulatory capacity of myeloid cells and the curtailment of myeloid-mediated immunosuppression are strategies that can augment the expansion and anti-tumor activity of TILs. The novel mechanistic insights of these studies highlight the importance of modulating myeloid cells to promote the therapeutic efficacy of ACT

Systemic and intravesical adoptive cell therapy of tumor-reactive T cells can decrease bladder tumor growth in vivo

Background The therapeutic armamentarium of bladder cancer has been recently enriched with the introduction of new therapies including immune checkpoint inhibitors, receptor tyrosine kinase inhibitors and antibody drug conjugates, however treatment responses and duration of responses are still less than expected. Adoptive cellular therapy (ACT) using tumor-infiltrating lymphocytes (TILs) has potential to treat bladder cancer, as previously demonstrated by successful expansion of tumor reactive T cells from human bladder tumors.Methods A model system using OT-I T cells and an ovalbumin expressing MB49 tumor cell line (MB49OVA) was developed to study ACT in bladder cancer. Systemic ACT-treated mice were given T cells intravenously after lymphodepleting chemotherapy and followed by interleukin (IL)-2 administration. Intravesical ACT treated mice were given T cells directly into the bladder, without chemotherapy or IL-2. TILs were isolated from MB49 orthotopic tumors and expanded ex vivo in IL-2. Immune cell infiltrates were analyzed by flow cytometry. T cell infiltration was studied using a CXCR3 blocking antibody.Results Systemic ACT-treated mice had a decrease in tumor growth, increase in T cell infiltration and long-term immune protection compared with control-treated mice. OT-I T cells delivered intravesically were able to control tumor growth without lymphodepleting chemotherapy or IL-2 in MB49OVA orthotopic tumors. Intravesical delivery of TIL expanded from MB49 tumors was also able to decrease tumor growth in mice with MB49 orthotopic tumors. Blocking CXCR3 on OT-I T cells prior to intravesical delivery decreased T cell infiltration into the tumor and prevented the control of tumor growth.Conclusions This study demonstrates how TIL therapy can be used in treating different stages of bladder cancer

Neoantigen-specific CD4+ tumor-infiltrating lymphocytes are potent effectors identified within adoptive cell therapy products for metastatic melanoma patients

Background Adoptive cell therapy (ACT) with tumor-infiltrating lymphocytes (TILs) is a promising immunotherapeutic approach for patients with advanced solid tumors. While numerous advances have been made, the contribution of neoantigen-specific CD4+T cells within TIL infusion products remains underexplored and therefore offers a significant opportunity for progress.Methods We analyzed infused TIL products from metastatic melanoma patients previously treated with ACT for the presence of neoantigen-specific T cells. TILs were enriched on reactivity to neoantigen peptides derived and prioritized from patient sample-directed mutanome analysis. Enriched TILs were further investigated to establish the clonal neoantigen response with respect to function, transcriptomics, and persistence following ACT.Results We discovered that neoantigen-specific TIL clones were predominantly CD4+ T cells and were present in both therapeutic responders and non-responders. CD4+ TIL demonstrated an effector T cell response with cytotoxicity toward autologous tumor in a major histocompatibility complex class II-dependent manner. These results were validated by paired TCR and single cell RNA sequencing, which elucidated transcriptomic profiles distinct to neoantigen-specific CD4+ TIL.Conclusions Despite methods which often focus on CD8+T cells, our study supports the importance of prospective identification of neoantigen-specific CD4+ T cells within TIL products as they are a potent source of tumor-specific effectors. We further advocate for the inclusion of neoantigen-specific CD4+ TIL in future ACT protocols as a strategy to improve antitumor immunity