Epigenomics in hematopoietic transplantation: novel treatment strategies

Allogeneic hematopoietic stem cell transplantation is a high risk but curative treatment option for leukemia, myelodysplasia and other hematological malignancies. After high dose radio- or chemo-therapy, recipient's hematopoiesis is replaced by a new immunosystem and residual malignant cells are eliminated by the graft-versus-leukemia reaction. The benefit of this immunological effect is limited by the most frequent complication of hematopoietic stem cell transplantation: graft-versus-host disease. In addition to their well-known anti-tumor activity, epigenetic drugs mediate immunotolerance without reducing alloreactivity or even enhance graft-versus-leukemia effect without inducing graft-versus-host disease by regulating cytokine release, increasing the circulating number of regulatory T cells and interacting with natural killer cells. We focus on the use of epigenetic drugs in the allogeneic transplantation setting in relation to their anti-tumor and immunomodulatory potential.