Periodic Reporting for period 2 - MitoGuide (Integration and adaptation of impaired mitochondrial fitness in orchestrating T cell dysfunction in the tumor microenvironment)
Okres sprawozdawczy: 2020-08-01 do 2022-01-31
Research has shown that many tumor types can be destroyed by tumor-reactive T cells and other immune cells, when immune cells are properly activated. These findings have led to the exciting development of cancer immunotherapies that yield remarkable and durable responses in established tumors by reawakening anti-tumor immunity. Nevertheless, a significant portion of patients treated with such therapy still exhibit high mortality. This may be in part because tumor-reactive T cells become dysfunctional upon infiltration into the tumor microenvironment (TME), a phenomenon referred to as “T cell exhaustion”. Moreover, emerging findings reveal that epigenetic alterations, including reprogramming of chromatin states and de novo DNA methylation, imprint T cell dysfunction and exhaustion. These studies further demonstrate that exhausted tumor-infiltrating CD8+ T lymphocytes can proliferate and exhibit certain degrees of effector functions after transfer into a naïve host; however, transferred cells quickly re-acquire the exhausted phenotype due to imprinted epigenetic programming. These results suggest that the TME can impose undefined modulations that lead to epigenetic reprogramming, thereby dictating T cell dysfunction and exhaustion.
Mitochondria govern cellular energy production via the tricarboxylic acid (TCA) cycle and electron transport chain. Through the cooperation of these metabolic processes, nutrients fuel cellular metabolic demands in response to growth factors, nutrient availability and nutrient-sensing signaling cascades. In addition, metabolic intermediates of the TCA cycle are used to produce building blocks for cell proliferation. Therefore, tight control that balances mitochondrial activity is critical to bridging nutrient availability and metabolic demands in response to stimuli for cell proliferation and activation. This tight control of mitochondrial functions also must communicate with nuclear events, including DNA replication, transcription and damage responses, through retrograde signals generated from mitochondria to ensure proper cellular responses. Intriguingly, emerging evidence indicates that epigenetic alterations might be the major regulatory mechanism to link mitochondrial activity with nuclear reprogramming. Although mitochondrial activities are critical for T cell differentiation, it remains unclear whether mitochondrial dynamics can be modulated to drive T cell dysfunction via alterations in their epigenome and generation of metabolic checkpoints.
Here, we aim to elucidate how the tumor microenvironment (TME) abolishes T cell anti-tumor responses by impairing the mitochondrial dynamics in TILs. We also aim to address whether diminished mitochondrial fitness in TILs leads to metabolic insufficiency and epigenetic reprogramming which induce a dysfunctional state in tumor-reactive T cells. New information about this process will be valuable to our understanding of how tumor cells impair anti-tumor immunity via undefined metabolic modulations. We further aim to develop approaches that harness metabolite-derived regulations to re-reprogram the epigenetic modifications that lock T cells into a dysfunctional state. Ultimately, our goal is to unleash anti-tumor immunity by restoring and/or sustaining T cell mitochondrial integrity and functions based on the findings of this proposal. The success of this work will represent an entirely new perspective on control of T cell functions by the immunosuppressive tumor microenvironment, and it may reveal new dimensions of immunometabolic regulation.
Mitochondria govern cellular energy production via the tricarboxylic acid (TCA) cycle and electron transport chain. Through the cooperation of these metabolic processes, nutrients fuel cellular metabolic demands in response to growth factors, nutrient availability and nutrient-sensing signaling cascades. In addition, metabolic intermediates of the TCA cycle are used to produce building blocks for cell proliferation. Therefore, tight control that balances mitochondrial activity is critical to bridging nutrient availability and metabolic demands in response to stimuli for cell proliferation and activation. This tight control of mitochondrial functions also must communicate with nuclear events, including DNA replication, transcription and damage responses, through retrograde signals generated from mitochondria to ensure proper cellular responses. Intriguingly, emerging evidence indicates that epigenetic alterations might be the major regulatory mechanism to link mitochondrial activity with nuclear reprogramming. Although mitochondrial activities are critical for T cell differentiation, it remains unclear whether mitochondrial dynamics can be modulated to drive T cell dysfunction via alterations in their epigenome and generation of metabolic checkpoints.
Here, we aim to elucidate how the tumor microenvironment (TME) abolishes T cell anti-tumor responses by impairing the mitochondrial dynamics in TILs. We also aim to address whether diminished mitochondrial fitness in TILs leads to metabolic insufficiency and epigenetic reprogramming which induce a dysfunctional state in tumor-reactive T cells. New information about this process will be valuable to our understanding of how tumor cells impair anti-tumor immunity via undefined metabolic modulations. We further aim to develop approaches that harness metabolite-derived regulations to re-reprogram the epigenetic modifications that lock T cells into a dysfunctional state. Ultimately, our goal is to unleash anti-tumor immunity by restoring and/or sustaining T cell mitochondrial integrity and functions based on the findings of this proposal. The success of this work will represent an entirely new perspective on control of T cell functions by the immunosuppressive tumor microenvironment, and it may reveal new dimensions of immunometabolic regulation.
This project has been conducted on different fronts, which are structured into three research thrusts.
First, Mitophagy-guided T cell anti-tumor immunity, we investigate the contribution of damage mitochondria removal machinery (mitophagy) on supporting T cell anti-tumor immunity. In this part, we confirm that a) mitophagy is required to support T cell anti-tumor immunity, maintain responsiveness to PD-1 blockade, drive formation of stem-like tutor-specific TILs; b) chronic T cell receptor stimulation and hypoxia in tumors abolish mitophagy activity in T cells; c) TILs accumulating depolarised mitochondria as a result of impaired mitophagy commit to terminally exhausted program. This exhausted features are characterised by functional, transcriptomic and epigenetic features, including changes in DNA methylation and chromatin accessibility.
Second, mitochondria-nucleus communication on guiding T cell anti-tumor responses, we uncover that the declined mitochondrial fitness in T cells leads to permanent impairment of proliferative capacity and effector molecule expression and sustained expression of inhibitory receptors. As a result of these actions, T cells accumulating depolarised mitochondria engage senescence/apoptosis and fail to sustain responsiveness to immune checkpoint blockade treatment. Moreover, we conduct an in vivo CRISPR screening to identify metabolic enzymes and kinase that can be targeted for sustaining mitochondrial fitness in CD8 TILs. We are currently in the stage to validate those targets we identify and elucidate how this targeting approach can be exploited in T cell transfer therapy. In the end of this direction, we also finish proteome analysis and are in the process to finish metabolic analysis. We expect the integrated cross-omics analysis will allow us to further explore how mitochondria instruct T cell functionality and differentiation.
In the third direction, we further reveal that forcing accumulation of depolarised mitochondria in CD8 T cells is sufficient to launch epigenetic reprogramming, including altered DNA methylation pattern and chromatin accessibility, for orchestrating T cell exhaustion. By combining this finding with the findings mentioned above, we conclude that accumulation of depolarised mitochondria is the driving force to instruct T cell differentiation programming. In line with this finding and our findings in the importance of mitophagy, we further unveil that nicotinamide riboside treatment can sustain mitochondrial fitness in CD8 TILs. As a result of this action, nicotinamide riboside is able to elicit robust anti-tumor responses as a single treatment, boost therapeutic benefits of PD-1 blockade, and support anti-tumor activity in CD8 TILs.
First, Mitophagy-guided T cell anti-tumor immunity, we investigate the contribution of damage mitochondria removal machinery (mitophagy) on supporting T cell anti-tumor immunity. In this part, we confirm that a) mitophagy is required to support T cell anti-tumor immunity, maintain responsiveness to PD-1 blockade, drive formation of stem-like tutor-specific TILs; b) chronic T cell receptor stimulation and hypoxia in tumors abolish mitophagy activity in T cells; c) TILs accumulating depolarised mitochondria as a result of impaired mitophagy commit to terminally exhausted program. This exhausted features are characterised by functional, transcriptomic and epigenetic features, including changes in DNA methylation and chromatin accessibility.
Second, mitochondria-nucleus communication on guiding T cell anti-tumor responses, we uncover that the declined mitochondrial fitness in T cells leads to permanent impairment of proliferative capacity and effector molecule expression and sustained expression of inhibitory receptors. As a result of these actions, T cells accumulating depolarised mitochondria engage senescence/apoptosis and fail to sustain responsiveness to immune checkpoint blockade treatment. Moreover, we conduct an in vivo CRISPR screening to identify metabolic enzymes and kinase that can be targeted for sustaining mitochondrial fitness in CD8 TILs. We are currently in the stage to validate those targets we identify and elucidate how this targeting approach can be exploited in T cell transfer therapy. In the end of this direction, we also finish proteome analysis and are in the process to finish metabolic analysis. We expect the integrated cross-omics analysis will allow us to further explore how mitochondria instruct T cell functionality and differentiation.
In the third direction, we further reveal that forcing accumulation of depolarised mitochondria in CD8 T cells is sufficient to launch epigenetic reprogramming, including altered DNA methylation pattern and chromatin accessibility, for orchestrating T cell exhaustion. By combining this finding with the findings mentioned above, we conclude that accumulation of depolarised mitochondria is the driving force to instruct T cell differentiation programming. In line with this finding and our findings in the importance of mitophagy, we further unveil that nicotinamide riboside treatment can sustain mitochondrial fitness in CD8 TILs. As a result of this action, nicotinamide riboside is able to elicit robust anti-tumor responses as a single treatment, boost therapeutic benefits of PD-1 blockade, and support anti-tumor activity in CD8 TILs.
This project pivots around five aspects which are beyond the state of the art:
1) The understanding on the unexplored link between mitochondrial fitness and epigenetic reprogramming in T cell exhaustion.
2) We define how the tumor microenvironment could diminish mitochondrial fitness in tumor-infiltrating CD8 T cells.
3) Establishing new dimension of understanding about how metabolic interventions that target tumor metabolism and/or immunometabolism could be exploited for rejuvenating T cell anti-tumor responses.
4) We also unexpectedly reveal interleukin-10 can rejuvenate terminally exhausted T cells by modulating mitochondrial pyruvate uptake. This finding open a new horizon on T cell biology and serves as a springboard for us to generating new immunotherapy modalities.
5) The first CRISPR screening for supporting mitochondrial fitness in T cells could be exploited on refining CAR T cell therapy.
1) The understanding on the unexplored link between mitochondrial fitness and epigenetic reprogramming in T cell exhaustion.
2) We define how the tumor microenvironment could diminish mitochondrial fitness in tumor-infiltrating CD8 T cells.
3) Establishing new dimension of understanding about how metabolic interventions that target tumor metabolism and/or immunometabolism could be exploited for rejuvenating T cell anti-tumor responses.
4) We also unexpectedly reveal interleukin-10 can rejuvenate terminally exhausted T cells by modulating mitochondrial pyruvate uptake. This finding open a new horizon on T cell biology and serves as a springboard for us to generating new immunotherapy modalities.
5) The first CRISPR screening for supporting mitochondrial fitness in T cells could be exploited on refining CAR T cell therapy.