ScienceDaily (June 25, 2008) — Drugs known as HDAC inhibitors, which have antitumor activity and can be used to treat some forms of skin cancer and some types of leukemia, are also known to have anti-inflammatory properties, but the mechanisms by which they modulate the immune system have not been determined.

New data, generated by Pavan Reddy and colleagues, at the University of Michigan Cancer Center, Ann Arbor, have now indicated one mechanism by which HDAC inhibitors modulate the mouse and human immune system and the information gained has been used to develop an approach to protect mice from graft-versus-host disease after bone marrow transplantation.

In the study, two different HDAC inhibitors were shown to prevent mouse and human immune cells known as dendritic cells (DCs) from initiating proinflammatory immune responses in vitro. Further, if DCs treated ex vivo with HDAC inhibitors were injected into mice after they had received a bone marrow transplant, the incidence and severity of graft-versus-host disease was dramatically reduced. Detailed analysis revealed that the HDAC inhibitors mediated their effects by inducing DCs to express more of a molecule known as IDO, which is a suppressor of DC function.

The authors therefore hope that their data provide support for studies to determine whether HDAC inhibitors might be of benefit to individuals receiving bone marrow transplants and to those with other immune-mediated diseases.

Journal reference:

1. Reddy et al. Histone deacetylase inhibition modulates indoleamine 2,3-dioxygenase–dependent DC functions and regulates experimental graft-versus-host disease in mice. Journal of Clinical Investigation, 2008; DOI: 10.1172/JCI34712

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