Graft-versus-tumor effect

Graft-versus-tumor effect (GvT) appears after allogeneic hematopoietic stem cell transplantation (HSCT). The graft contains donor T cells (T lymphocytes) that can be beneficial for the recipient by eliminating residual malignant cells.[1] GvT might develop after recognizing tumor-specific or recipient-specific alloantigens. It could lead to remission or immune control of hematologic malignancies.[2] This effect applies in myeloma and lymphoid leukemias, lymphoma, multiple myeloma and possibly breast cancer.[3] It is closely linked with graft-versus-host disease (GvHD), as the underlying principle of alloimmunity is the same. CD4+CD25+ regulatory T cells (Treg) can be used to suppress GvHD without loss of beneficial GvT effect.[4] The biology of GvT response still isn't fully understood but it is probable that the reaction with polymorphic minor histocompatibility antigens expressed either specifically on hematopoietic cells or more widely on a number of tissue cells or tumor-associated antigens is involved.[5][6] This response is mediated largely by cytotoxic T lymphocytes (CTL) but it can be employed by natural killers (NK cells) as separate effectors, particularly in T-cell-depleted HLA-haploidentical HSCT.[6]

Graft-versus-leukemia

Graft-versus-leukemia (GvL) is a specific type of GvT effect. As the name of this effect indicates, GvL is a reaction against leukemic cells of the host. GvL requires genetic disparity because the effect is dependent on the alloimmunity principle. GvL is a part of the reaction of the graft against the host. Whereas graft-versus-host-disease (GvHD) has a negative impact on the host, GvL is beneficial for patients with hematopeietic malignancies. After HSC transplantation both GvL and GvHD develop. The interconnection of those two effects can be seen by comparison of leukemia relapse after HSC transplantation with development of GvHD. Patients who develop chronic or acute GvHD have lower chance of leukemia relapse.[7] When transplanting T-cell depleted stem cell transplant, GvHD can be partially prevented, but in the same time the GvL effect is also reduced, because T-cells play an important role in both of those effects.[8] The possibilities of GvL effect in the treatment of hematopoietic malignancies are limited by GvHD. The ability to induce GvL but not GvH after HSCT would be very beneficial for those patients. There are some strategies to suppress the GvHD after transplantation or to enhance GvL but none of them provide an ideal solution to this problem. For some forms of hematopoietic malignancies, for example acute myeloid leukemia (AML), the essential cells during HSCT are, beside the donor's T cells, the NK cells, which interact with KIR receptors. NK cells are within the first cells to repopulate host's bone marrow which means they play important role in the transplant engraftment. For their role in the GvL effect, their alloreactivity is required.[9] Because KIR and HLA genes are inherited independently, the ideal donor can have compatible HLA genes and KIR receptors that induce the alloreaction of NK cells at the same time. This will occur with most of the non-related donor. When transplanting HSC during AML, T-cells are usually selectively depleted to prevent GvHD while NK cells help with the GvL effect which prevent leukemia relapse. When using non-depleted T-cell transplant, cyclophosphamide is used after transplantation to prevent GvHD or transplant rejection. Other strategies currently clinically used for suppressing GvHD and enhancing GvL are for example optimization of transplant condition or donor lymphocyte infusion (DLI) after transplantation.[10][11] However, none of those provide satisfactory universal results, thus other options are still being inspected. One of the possibilities is the use of cytokines. Granulocyte colony-stimulating factor (G-CSF) is used to mobilize HSC and mediate T cell tolerance during transplantation. G-CSF can help to enhance GvL effect and suppress GvHD by reducing levels of LPS and TNF-α. Using G-CSF also increases levels of Treg, which can also help with prevention of GvHD. Other cytokines can also be used to prevent or reduce GvHD without eliminating GvL, for example KGF, IL-11, IL-18 and IL-35.[11]

See also

References
  1. Thompson LF, Tsukamoto H, Chernogorova P, Zeiser R (January 2013). "A delicate balance: CD73-generated adenosine limits the severity of graft vs. host disease but also constrains the allogeneic graft vs. tumor effect". Oncoimmunology. 2 (1): e22107. doi:10.4161/onci.22107. PMC 3583907. PMID 23482243.
  2. Kolb HJ (December 2008). "Graft-versus-leukemia effects of transplantation and donor lymphocytes". Blood. 112 (12): 4371–83. doi:10.1182/blood-2008-03-077974. PMID 19029455.
  3. Childs RW, Clave E, Tisdale J, Plante M, Hensel N, Barrett J (July 1999). "Successful treatment of metastatic renal cell carcinoma with a nonmyeloablative allogeneic peripheral-blood progenitor-cell transplant: evidence for a graft-versus-tumor effect". Journal of Clinical Oncology. 17 (7): 2044–9. doi:10.1200/jco.1999.17.7.2044. PMID 10561256.
  4. Vagianos C, Polydorou A, Karatzas T, Vagenas C, Stavropoulos M, Androulakis J (1992). "Successful treatment of postoperative external biliary fistula by selective nasobiliary drainage". HPB Surgery. 6 (2): 115–20, discussion 120–4. doi:10.1155/1992/58436. PMC 2443016. PMID 1292584.
  5. Baron F, Maris MB, Sandmaier BM, Storer BE, Sorror M, Diaconescu R, et al. (March 2005). "Graft-versus-tumor effects after allogeneic hematopoietic cell transplantation with nonmyeloablative conditioning". Journal of Clinical Oncology. 23 (9): 1993–2003. doi:10.1200/JCO.2005.08.136. PMID 15774790.
  6. Rezvani AR, Storb RF (May 2008). "Separation of graft-vs.-tumor effects from graft-vs.-host disease in allogeneic hematopoietic cell transplantation". Journal of Autoimmunity. 30 (3): 172–9. doi:10.1016/j.jaut.2007.12.002. PMC 2329571. PMID 18242060.
  7. Horowitz MM, Gale RP, Sondel PM, Goldman JM, Kersey J, Kolb HJ, et al. (February 1990). "Graft-versus-leukemia reactions after bone marrow transplantation". Blood. 75 (3): 555–62. doi:10.1182/blood.V75.3.555.555. PMID 2297567.
  8. Kolb HJ, Schmid C, Barrett AJ, Schendel DJ (February 2004). "Graft-versus-leukemia reactions in allogeneic chimeras". Blood. 103 (3): 767–76. doi:10.1182/blood-2003-02-0342. PMID 12958064.
  9. Falco M, Pende D, Munari E, Vacca P, Mingari MC, Moretta L (April 2019). "Natural killer cells: From surface receptors to the cure of high-risk leukemia (Ceppellini Lecture)". HLA. 93 (4): 185–194. doi:10.1111/tan.13509. PMC 6767140. PMID 30828978.
  10. Warren EH, Deeg HJ (April 2013). "Dissecting graft-versus-leukemia from graft-versus-host-disease using novel strategies". Tissue Antigens. 81 (4): 183–93. doi:10.1111/tan.12090. PMC 3645301. PMID 23510414.
  11. Chang YJ, Zhao XY, Huang XJ (2018-12-21). "Strategies for Enhancing and Preserving Anti-leukemia Effects Without Aggravating Graft-Versus-Host Disease". Frontiers in Immunology. 9: 3041. doi:10.3389/fimmu.2018.03041. PMC 6308132. PMID 30619371.


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