Hematological malignancies that include leukemia and lymphoma are often treated with allogeneic hematopoietic stem cell transplantation (allo-HCT). However, chronic graft-versus-host disease (cGVHD) remains a prominent cause of transplant-related morbidity and mortality despite available immunosuppressive regimens. Few prophylactic strategies have been successful at reducing the incidence of cGVHD in patients after allo-HCT. An area previously unexplored as a treatment for cGVHD involves the unfolded protein response (UPR). Three master regulators control the UPR: PERK, IRE-1?, and ATF6. When IRE-1? becomes activated, its primary function is to splice Xbox binding protein-1 (XBP-1u) mRNA. Spliced XBP-1 (XBP-1s) mRNA is translated into XBP-1 protein which acts as an effective nuclear transcription factor. Immune responses such as B-cell proliferation and antibody production require large amounts of properly folded proteins. As a transcription factor, XBP-1 protein relieves ER stress by up regulating cellular machinery responsible for protein folding and degradation. XBP-1 is therefore required for the effector function and survival of various types of immune cells that are susceptible to ER stress. IRE-1?/XBP-1 signaling axis plays predominate roles in B cells and dendritic cells (DCs) among other immune cells. Built upon published findings and our preliminary observations, we will evaluate how IRE-1?/XBP-1 signaling axis impacts in the development of cGVHD after allo-HCT through regulating B cells and DCs among others. Our Central Hypothesis is that XBP-1 plays an essential role for B-cell and DC activation and function, and targeting XBP-1 will restrain allogeneic responses leading to the control of cGVHD while preserving the integrity of cytotoxic T lymphocytes (CTL) and thus maintaining the graft-versus-leukemia (GVL) effect. This hypothesis will be tested in the following two Specific Aims: 1) Define the contribution of XBP-1 on hematopoietic cells in the development of cGVHD after allo-HCT using a genetic approach; 2) Determine the therapeutic effect of targeting XBP-1 in the control of cGVHD and leukemia relapse using a pharmacological approach. The current study is expected to further understand the cell biology how UPR regulates immune responses, reveal the role for IRE-1?/XBP-1 signaling axis in the development of cGVHD and relatable hematologic malignancies, and provide a novel therapy for controlling cGVHD and leukemia relapse in after allo-HCT.
Hematopoietic cell transplantation (HCT) offers great promise for the treatment of a variety of diseases including blood related cancers, but causes a major complication termed graft-versus-host disease (GVHD). Many types of immune cells contribute to the development of GVHD, especially its chronic form. The current research is designed to further understand cellular stress response of immune cells under HCT, and to identify potential therapeutic target(s) for controlling GVHD as well as leukemia recurrence.