Periodic Reporting for period 4 - HOPE (Host Protective Engineering of Cancer Immunity by Targeting the Intracellular Immune Checkpoint NR2F6)
Reporting period: 2023-04-01 to 2024-09-30
Cancer immunotherapy, using regimens called immune checkpoint blockade (ICB) or personalized chimeric antigen receptor-engineered T cell immunotherapy (CAR-T), has become an innovative therapeutic pillar in oncology. Although cancer immunotherapy has definitely changed the way cancer is treated, a significant proportion of patients still fail to respond to, and even fewer are cured by, these current clinical strategies. Therefore, additional therapeutic target protein candidates suitable for the boosting of antitumor effector responses need to be identified. In my ERC project "HOPE", we are investigating the unique potential of the orphan intracellular receptor NR2F6 (nuclear receptor subfamily 2 group F member 6) and its effector pathway in T cells as an emerging alternative target for cancer immunotherapy to significantly increase response rates in e.g. NSCLC lung cancer patients.
We validated NR2F6 as a lege artis immune checkpoint using germline gene ablation and CRISPR/Cas9-mediated acute gene mutagenesis. Thus, especially in combination with ICB and CAR-T therapy regimens, targeting this nuclear receptor appears to be a strategy for improving antitumor immunotherapy responses. Taken together, our current preclinical experimental knowledge may be a promising and innovative perspective for human immunotherapy in the near future for the enhancement of immune system responses.
Why is the alternative and druggable immune checkpoint NR2F6 important?
NR2F6 is a recently discovered cancer immune checkpoint protein. It is found at particularly high levels in effector T cells that have infiltrated solid tumours. Consistent with this observation, genetic NR2F6 inhibition experiments have shown encouragingly strong improvements in T cell responses using both human PBMC in vitro and preclinical cancer therapy models in vivo. Investigation of Nr2f6 inhibition in mice using ex vivo CRISPR/Cas9-mediated gene ablation of Nr2f6 in T cells prior to therapeutic cell therapy, particularly in conjunction with ICB therapy, greatly improved the outcome of therapeutic anti-cancer responses.
NR2F6 may turn out to be an emerging and most suitable next-generation sensitiser target for improving T cell efficacy and subsequently immunotherapeutic outcome, thereby increasing the percentage of cancer patients responding to therapy, based on the current thinking that the most successful immuno-oncology concepts need to be used as combinatorial therapies.
Of particular note, our study targeting NR2F6 in mice in combination with ICB treatment showed no exacerbated signs of immune related adverse effects (irAE) over a three month follow-up period. When compared directly with untreated mice, there were no significant differences in immune cell infiltration, weight loss or colon length in mice with Nr2f6 deficiency. Our findings suggest that NR2F6 might be a highly localized immune checkpoint at the tumor site and that, subsequently, Nr2f6 inhibition boosts only a locally restricted antitumor effector T cell response with fewer systemic IrAE.
Indeed, NR2F6-targeting regimens are currently being investigated in research and development laboratories around the world. At the end of the day, we "HOPE" (as our ERC project acronym already suggested) that this NR2F6-centered alternative therapeutic approach, if proven successful, could complement existing therapeutic models and significantly increase response rates in cancer patients and/or expand the reach of immunotherapies to a wider range of cancer types.
We validated NR2F6 as a lege artis immune checkpoint using germline gene ablation and CRISPR/Cas9-mediated acute gene mutagenesis. Thus, especially in combination with ICB and CAR-T therapy regimens, targeting this nuclear receptor appears to be a strategy for improving antitumor immunotherapy responses. Taken together, our current preclinical experimental knowledge may be a promising and innovative perspective for human immunotherapy in the near future for the enhancement of immune system responses.
Why is the alternative and druggable immune checkpoint NR2F6 important?
NR2F6 is a recently discovered cancer immune checkpoint protein. It is found at particularly high levels in effector T cells that have infiltrated solid tumours. Consistent with this observation, genetic NR2F6 inhibition experiments have shown encouragingly strong improvements in T cell responses using both human PBMC in vitro and preclinical cancer therapy models in vivo. Investigation of Nr2f6 inhibition in mice using ex vivo CRISPR/Cas9-mediated gene ablation of Nr2f6 in T cells prior to therapeutic cell therapy, particularly in conjunction with ICB therapy, greatly improved the outcome of therapeutic anti-cancer responses.
NR2F6 may turn out to be an emerging and most suitable next-generation sensitiser target for improving T cell efficacy and subsequently immunotherapeutic outcome, thereby increasing the percentage of cancer patients responding to therapy, based on the current thinking that the most successful immuno-oncology concepts need to be used as combinatorial therapies.
Of particular note, our study targeting NR2F6 in mice in combination with ICB treatment showed no exacerbated signs of immune related adverse effects (irAE) over a three month follow-up period. When compared directly with untreated mice, there were no significant differences in immune cell infiltration, weight loss or colon length in mice with Nr2f6 deficiency. Our findings suggest that NR2F6 might be a highly localized immune checkpoint at the tumor site and that, subsequently, Nr2f6 inhibition boosts only a locally restricted antitumor effector T cell response with fewer systemic IrAE.
Indeed, NR2F6-targeting regimens are currently being investigated in research and development laboratories around the world. At the end of the day, we "HOPE" (as our ERC project acronym already suggested) that this NR2F6-centered alternative therapeutic approach, if proven successful, could complement existing therapeutic models and significantly increase response rates in cancer patients and/or expand the reach of immunotherapies to a wider range of cancer types.
Our research project has provided valuable results in 3 objectives according to the ERC "HOPE" project plan
Objective 1: NR2F6 pathway as an off-switch of antitumor T cell responses
Objective 2: Biological and clinical properties of NR2F6 in solid tumors such as lung cancer and metastatic melanoma
Objective 3: Human NR2F6 as a therapeutic candidate target for solid tumors
Objective 1: NR2F6 pathway as an off-switch of antitumor T cell responses
Objective 2: Biological and clinical properties of NR2F6 in solid tumors such as lung cancer and metastatic melanoma
Objective 3: Human NR2F6 as a therapeutic candidate target for solid tumors
Long-term perspective of results from our ERC "HOPE" project:
Our detailed insight into the NR2F6 mechanism of action (MoA) using biochemical and cell-based assays has led to improved knowledge for validating NR2F6 targets to lay the foundation for a rational therapeutic approach based on NR2F6 inhibition. Our discovery that NR2F6 inactivation as a single regulator of immune suppression provides a unique cancer therapeutic strategy to selectively manipulate tumor antigen-specific CD4+ and CD8+ effector T cells to induce host-protective cancer immunity in preclinical models. Modification of this newly defined NR2F6-mediated immunosuppression is essential for effector T cell activation and differentiation, a process critically involved in host protection during malignant disease and potentially also in other immune disorders (for an overarching concept, please see figure cartoon below).
Our long-term research in Innsbruck will continue to explore the forward translation of our basic knowledge of NR2F6 immune checkpoint function.
First, within this initiative, we will be able to set the stage for the validation and characterization of e.g. low molecular weight (LMW) compounds with respect to their future therapeutic potential for the treatment of malignancies in the clinic. The most relevant and robust functional HTS and secondary assays to support the hit-to-lead phase of this drug discovery program can now be developed to orthogonally validate candidates in intact human T cells. This will provide critical support for the identification of NR2F6 inhibitor candidates, in addition to the high academic value of our research (likely to lead to high impact publications in the near future).
Secondly, we are also considering to take the direction of personalized chimeric antigen receptor-engineered (CAR) T cell immunotherapy for solid NSCLC tumors that proves to be particularly promising. By NR2F6 pathway blockade, the extension of the success of CAR T cell therapy against blood cancers may allow the development of more effective treatment regimens for the treatment of advanced metastatic solid cancers.
However, as a note of caution, the current target validation of NR2F6 is based on evidence from preclinical models only. Given the lack of human data on the role of lymphatic NR2F6 as a suppressor of effective cancer immunity, the fate of the NR2F6-based immuno-oncology therapy envisioned here ultimately depends on functional antagonists for NR2F6, once established, and their outcome in human clinical trials.
Nevertheless, further exploration of NR2F6 may very well represent an appropriate avenue for drug discovery and offer an innovative, mechanism-based therapeutic strategy to enhance the sensitivity of tumor-infiltrating T cells to tumor antigens in patients with solid cancers. Therefore, the critical objective for follow-up research of our ERC "HOPE" project work is to firmly validate this human immune checkpoint candidate NR2F6 as a unique therapeutic target for next-generation immuno-oncology regimens.
However, at the end of the day and based on our research findings on NR2F6, with particular emphasis on the unique potential of NR2F6 and its critical and non-redundant role in T cell-mediated cancer immunity, we are " HOPE" - FULL that advances of distinct strategies targeting NR2F6 in the clinic may be made a reality in the near future.
Our detailed insight into the NR2F6 mechanism of action (MoA) using biochemical and cell-based assays has led to improved knowledge for validating NR2F6 targets to lay the foundation for a rational therapeutic approach based on NR2F6 inhibition. Our discovery that NR2F6 inactivation as a single regulator of immune suppression provides a unique cancer therapeutic strategy to selectively manipulate tumor antigen-specific CD4+ and CD8+ effector T cells to induce host-protective cancer immunity in preclinical models. Modification of this newly defined NR2F6-mediated immunosuppression is essential for effector T cell activation and differentiation, a process critically involved in host protection during malignant disease and potentially also in other immune disorders (for an overarching concept, please see figure cartoon below).
Our long-term research in Innsbruck will continue to explore the forward translation of our basic knowledge of NR2F6 immune checkpoint function.
First, within this initiative, we will be able to set the stage for the validation and characterization of e.g. low molecular weight (LMW) compounds with respect to their future therapeutic potential for the treatment of malignancies in the clinic. The most relevant and robust functional HTS and secondary assays to support the hit-to-lead phase of this drug discovery program can now be developed to orthogonally validate candidates in intact human T cells. This will provide critical support for the identification of NR2F6 inhibitor candidates, in addition to the high academic value of our research (likely to lead to high impact publications in the near future).
Secondly, we are also considering to take the direction of personalized chimeric antigen receptor-engineered (CAR) T cell immunotherapy for solid NSCLC tumors that proves to be particularly promising. By NR2F6 pathway blockade, the extension of the success of CAR T cell therapy against blood cancers may allow the development of more effective treatment regimens for the treatment of advanced metastatic solid cancers.
However, as a note of caution, the current target validation of NR2F6 is based on evidence from preclinical models only. Given the lack of human data on the role of lymphatic NR2F6 as a suppressor of effective cancer immunity, the fate of the NR2F6-based immuno-oncology therapy envisioned here ultimately depends on functional antagonists for NR2F6, once established, and their outcome in human clinical trials.
Nevertheless, further exploration of NR2F6 may very well represent an appropriate avenue for drug discovery and offer an innovative, mechanism-based therapeutic strategy to enhance the sensitivity of tumor-infiltrating T cells to tumor antigens in patients with solid cancers. Therefore, the critical objective for follow-up research of our ERC "HOPE" project work is to firmly validate this human immune checkpoint candidate NR2F6 as a unique therapeutic target for next-generation immuno-oncology regimens.
However, at the end of the day and based on our research findings on NR2F6, with particular emphasis on the unique potential of NR2F6 and its critical and non-redundant role in T cell-mediated cancer immunity, we are " HOPE" - FULL that advances of distinct strategies targeting NR2F6 in the clinic may be made a reality in the near future.