Lisbeth Barkholt

Transplantation of allogeneic hematopoietic stem cells: an emerging treatment modality for solid tumors

Allogeneic transplantation of hematopoietic cells from an HLA-compatible donor has been used to treat hematologic malignancies. Allogeneic transplantation not only replaces the marrow affected by the disease, but exerts an immune graft-versus-tumor (GVT) effect mediated by donor lymphocytes. The development of nonmyeloablative conditioning regimens before allogeneic transplantation has allowed this therapy to be used in elderly and disabled patients. An allogeneic GVT effect is observed in a proportion of patients with renal, breast, colorectal, ovarian, and pancreatic cancer treated with allogeneic transplantation. In general, the tumor response is associated with the development of acute and chronic graft-versus-host disease. Further improvements will depend on the identification of the antigen targets of GVT, and on reduction of the toxicity of the procedure. Targeted therapies may complement the immune effect of allogeneic transplantation. We present updated results from the literature and data recently placed on file at the European Bone Marrow Transplantation Solid Tumors Working Party.

Reduced-intensity allogeneic hematopoietic stem cell transplantation in metastatic colorectal cancer as a novel adoptive cell therapy approach. The European group for blood and marrow transplantation experience

Reduced-intensity conditioning (RIC) regimens for allogeneic hematopoietic stem cell transplantation (HCT) allowed the existence of an allogeneic cell-mediated antitumor effect in metastatic colorectal cancer (mCRC) to be explored. We report on 39 patients with progressing mCRC treated with different RIC regimens in a multicenter clinical trial of the European Bone Marrow Transplantation Group. Disease status at transplant was progressive disease (PD) in 31 patients (80%), stable disease (SD) in 6 (15%), and partial response (PR) in 2 (5%). All patients engrafted (median donor T cell chimerism of 90% at day +60). Transplant-related morbidities were limited. Grades II-IV acute graft-versus-host disease (aGVHD) occurred in 14 patients (35%) and chronic GVHD (cGVHD) in 9 patients (23%). Transplant-related mortality occurred in 4 patients (10%). The best tumor responses were: 1 complete response (CR) (2%), 7 PR (18 %), and 10 SD (26%), giving an overall disease control in 18 of 39 patients (46%). Allogeneic HCT after RIC is feasible; the collected results compared favorably in terms of tumor response with those observed using conventional approaches beyond second-line therapies. The study of an allogeneic cell based therapy in less advanced patients is warranted.

T‐Cell Receptor Vβ Repertoire after Myeloablative and Reduced Intensity Conditioning Allogeneic Haematopoietic Stem Cell Transplantation

T cells play an important role in the adaptive immune system. After haematopoietic stem cell transplantation (HSCT), T‐cell function is impaired. This is reflected by the emergence of opportunistic infections, infections that are often difficult to treat because of the patients insufficient immune function. T‐cell receptor reconstitution was studied using CDR3 spectratyping to analyze the diversity of the T‐cell repertoire at 3, 6 and 12 months after myeloablative and reduced intensity conditioning (RIC) HSCT in 23 patients. Immune function in vitro was tested by lymphocyte stimulation at 3, 6 and 12 months after HSCT. Lower diversity in the CDR3 repertoire was demonstrated in CD4+ cells after RIC HSCT at 3 and 6 months and in CD8+ cells at 3 months compared with healthy donors. After myeloablative HSCT, lower diversity was seen at 3, 6 and 12 months in CD4+ cells and at 6 and 12 months in CD8+ cells after HSCT. Acute and chronic graft‐versus‐host‐disease (GVHD) did not affect diversity. Responses to phytohaemagglutinin (PHA), Concanavalin A (Con A) and Staphylococcus aureus protein A were significantly lower compared with healthy donors during the first 6 months after RIC HSCT. After myeloablative HSCT, lymphocyte response to Con A was significantly lower at 3 months compared with healthy donors. Decreased responses to cytomegalovirus and varicella zoster virus antigens were seen in patients suffering from acute GVHD grade II or chronic GVHD. The T‐cell repertoire is skewed under the first year after HSCT, and immune reconstitution after HSCT with myeloablative and RIC conditioning seems to be comparable. GVHD, infections and age are more important for immune reconstitution than type of conditioning.

Reconstitution of the ig heavy chain CDR3 repertoire after allogeneic haematopoietic stem cell transplantation with myeloablative or reduced-intensity conditioning regimens

The objective of this study was to investigate B‐lymphocyte reconstitution in patients undergoing allogeneic haematopoietic stem cell transplantation (HSCT) after myeloablative conditioning (MAC) or reduced‐intensity conditioning (RIC) regimens. B‐lymphocyte reconstitution was studied by monitoring the CDR3 repertoire with spectratyping. We demonstrate a delay in the recovery of the B‐lymphocyte repertoire, measured by variation in size distribution of the immunoglobulin H CDR3 in patients conditioned with RIC compared to MAC. We found no general explanation for this finding, but when clinical data for each patient were studied in detail, we could identify a cause for the oligoclonality of the B‐lymphocyte repertoire after HSCT with RIC for each of the patients. Older patients and donors, low cell dose at transplantation, relapse, graft‐versus‐host disease (GVHD) and its treatment as well as cytomegalovirus infection and its treatment are all possible causes for the restriction of the B‐lymphocyte repertoire observed in this study. Taken together, reconstitution of the B‐lymphocyte repertoire after HSCT is a process dependent on multiple factors and differs between patients. The conditioning regimen may be of importance, but data from this study suggest that individual factors and the various complications occurring after HSCT are more likely to determine the development of the B‐lymphocyte repertoire.

Importance of CsA drug monitoring in SCT recipients to minimize GVHD and maximize graft vs. leukemia

The new human immune system that develops after allogeneic hematopoietic stem cell transplantation (SCT) can destroy tumor cells, offering the only potential cure for many patients suffering from malignant hematological disease (1). In leukemia and solid tumor patients with verified graft-versus-leukemia/tumor (GVL/ GvT) effect, donor CD4+ and CD8+ T cells that are reactive with patient s malignant cells can be detected in the blood after transplantation and may persist for years. Individual allogeneic T-cell clones have been isolated and have shown to exhibit cytolytic activity against recipient leukemia/tumor cells, mostly by recognizing minor histocompatibility (H) antigens (peptides derived from endogenous proteins) that are presented by major HLA molecules of recipient cells (2). Smaller T-cell subsets seem to recognize tumor-specific determinants (3–5). However, T cell recognition of recipient s highly immunogeneic minor H antigens is also responsible for graft vs. host disease (GVHD) (6). Thus, a prevailing challenge in allogeneic SCT is to develop approaches that will permit separation of the GVL effect from GVHD or abrogate GVHD after tumor eradication is complete.