New Research Shows Beneficial Role of Deleting AMPK in Graft-Versus-Host Disease

Graft-versus-host disease (GVHD) continues to be a troubling complication of allogeneic stem cell transplantation (alloSCT), carrying with it the potential for numerous morbidities and a significant risk of overall mortality. Post-transplant treatment options for GVHD remain limited to steroid therapy or nonspecific immunosuppression. However, steroid therapy carries risks of its own, and individuals with treatment-resistant GVHD have exceptionally high mortality rates.

The Byersdorfer Laboratory in the Division of Blood and Marrow Transplantation and Cellular Therapies (BMT-CT) at UPMC Children’s Hospital of Pittsburgh, led by associate professor of pediatrics Craig A. Byersdorfer, MD, PhD, is focused on studying the basic science of GVHD — its mechanistic properties — and through that work, identifying potential targets for novel therapies.

“Stem cell transplantation is and continues to be a promising therapy for otherwise incurable diseases. But we must figure out a way to either eliminate the possibility of GVHD - which would be a tremendous accomplishment — or develop treatment options that can safely ameliorate the condition if it occurs,” says Dr. Byersdorfer.

In July, Dr. Byersdorfer and colleagues published findings from their latest study¹ on the role of AMPK in GVHD in the journal JCI Insight.

AMPK is an enzyme that functions as a cellular energy sensor and regulates specific metabolic pathways within activated cells. In T cells, AMPK activity is upregulated because of the level and duration of allogeneic stimulation post-transplant. 

Key Study Findings

Dr. Byersdorfer's study produced several notable findings that he and his team plan to investigate further as they piece together the mechanistic properties of AMPK and its role in T cell-driven GVHD, including whether AMPK can serve as a viable target for therapeutic intervention or modulation.

Using a knockout mouse model in which the gene coding for AMPK is deleted in donor T cells, Dr. Byersdorfer’s team found that not only was the severity of GVHD suppressed to 40% of healthy controls, but that beneficial graft-versus-leukemia responses and reconstitution of the immune system post-transplant remained intact. Furthermore, these beneficial effects were maintained over a range of T cell doses. 

Data from the study also indicate that when AMPK is deleted, the number of effector T cells decreased early in the post-transplant process. However, important metabolic (fatty acid oxidation) and intrinsic cellular activities, including autophagy and mammalian target of rapamycin (mTOR) signaling, were unaffected. 

Furthermore, the study team uncovered that AMPK activity within the first 72 hours is critical in regards to subsequent GVHD initiation. As most clinical incidences of GVHD are noticed between day 20 and 60 post-transplant, it is likely that subclinical activity is already happening at the cellular level long before it can be detected through histologic or other laboratory testing.

"It appears that AMPK activity is absolutely critical in donor T cells during the first 72-96 hours post-transplant, for reasons that are not entirely clear. Some of our future studies will delve further into understanding how and why this is the case. We suspect that this initial post-transplant period will be crucial in managing GVHD in the future," says Dr. Byersdorfer.

Testing the Hypothesis in the Face of Immunosuppression

Since stem cell transplant patients all receive some form of immunosuppression as part of their therapeutic regimen, Dr. Byersdorfer and his team ran separate experiments on their models in the face of an immunosuppression agent, in this case, tacrolimus. T cells from immunosuppressed models continued to show the same strong increase in AMPK activity that was seen in non-immunosuppressed T cell populations. Importantly, these data suggest that inhibition or genetic deletion of AMPK would still be beneficial to patients on current regimens of post-transplant immunosuppression. 

Future Studies and Clinical Implications

While AMPK’s mechanism of action with respect to GVHD pathogenesis, maintenance, and severity is not fully understood, it may still prove to be a viable target in modulating disease severity. Due to AMPK’s involvement in multiple cell types throughout the body, systemic inhibition of AMPK is unlikely to be a viable therapeutic strategy. However, there are potential alternatives that Dr. Byersdorfer and his team are considering.

Stem cell transplant therapies, by their very nature, involve a period of time between when cells are harvested from the donor and when they are transplanted into the new host. This creates a window in which to target potentially pathogenic T cells ex vivo prior to patient administration. In this case, modulatory approaches to suppress AMPK activity, such as pharmacologic inhibition of AMPK or genetic deletion of the AMPK gene using CRISPR-mediated technologies, could be undertaken between donor cell collection and subsequent recipient administration. 

"Our lab is actively pursuing this line of research as part of our ongoing investigations on the role of AMPK in T cells," says Dr. Byersdorfer. "We are intrigued by the possibility of modifying or targeting donor cells prior to transplantation as a means to reduce or prevent GVHD."

Reference

1. Monlish DA, Beezhold KJ, Chiaranunt P, Paz K, Moore NJ, Dobbs AK, Brown RA, Ozolek JA, Blazar BR, Byersdorfer CA. Deletion of AMPK Minimizes Graft-Versus-Host Disease Through an Early Impact on Effector Donor T Cells. JCI Insight. 2021 July 22; 6(14): 143811. Epub ahead of print.

Further Reading 

Braverman EL, Waltz G, Byersdorfer CA. Immunometabolism in Haematopoietic Stem Cell Transplantation and Adoptive Cellular Therapies. Curr Opin Hematol. 2020 Nov; 27(6): 353-359.
Review.

Brown RA, Byersdorfer CA. Metabolic Pathways in Alloreactive T Cells. Front Immunol. 2020 Jul 24; 11: 1517. Review.

Glick GD, Rossignol R, Lyssiotis CA, Wahl D, Lesch C, Sanchez B, Liu X, Hao LY, Taylor C, Hurd A, Ferrara JL, Tkachev V, Byersdorfer CA, Boros L, Opipari AW. Anaplerotic Metabolism of Alloreactive T Cells Provides a Metabolic Approach to Treat Graft-Versus-Host Disease. J Pharmacol Exp Ther. 2014 Nov; 351(2):2 98-307. 

Byersdorfer CA, Tkachev V, Opipari AW, Goodell S, Swanson J, Sandquist S, Glick GD, Ferrara JL. Effector T Cells Require Fatty Acid Metabolism During Murine Graft-Versus-Host Disease.
Blood. 2013 Oct 31; 122(18): 3230-3237.