CDK-inhibitor independent cell cycle progression in an experimental haematopoietic stem cell leukaemia despite unaltered Rb-phosphorylation

A CD34-negative haematopoietic progenitor cell line, D064, derived from canine bone marrow stromal cells is able to differentiate into haematopoietic progenitors under the influence of growth factor-mediated signalling. While differentiating, these cells eventually start to express MHC class II molecules (DR homologues) on their surface. The stable transfection of the fibroblast-like wild-type cells with retroviral constructs containing the cDNA for the canine MHC class II DR-genes (DRA and DRB) induces a change in morphology, accelerates cell cycle progression and leads to a loss of anchorage-dependent growth. Transfected cells show features of an immature stem cell leukaemia, such as giant cell formation. In wild-type D064 cells the accumulation of the cyclin-dependent kinase inhibitor (cdki) p27kip-1 induces differentiation, which is dependent upon signalling via the ligand for the tyrosine kinase receptor c-kit (stem cell factor). DR-transfected cells instead apparently grow independently of any growth factor-mediated signals and express high levels of the cdkis p27kip-1 and especially p21waf-1/cip-1, concurrently with accelated cell cycle progression. In contrast to the overexpression of cdkis and despite accelerated cell cycle progression, the expression of the G2/M phase transition kinase p34cdc2 is significantly reduced in DR-transfected and transformed cells as compared to the haematopoietic wild-type cell line D064. This might suggest a possible alternative cell cycle progression pathway in this experimental stem cell leukaemia by by-passing the G0/G1 phase arrest, although retinoblastoma (Rb)-phosphorylation remains unaltered. These results provide evidence that mechanisms normally controlling the cell cycle and early haematopoietic differentiation are disrupted by the constitutive transcription and expression of MHC class II genes (DR) leading to a progression and growth of this experimental stem cell leukaemia independent from cell cycle controlling regulators such as p27 and p21. © 1999 Cancer Research Campaig

Changes in Hematopoietic Cell Transplantation Practices in Response to COVID-19: A Survey from the Worldwide Network for Blood & Marrow Transplantation.

SARS-CoV-2 has spread rapidly worldwide, but the full impact of the COVID-19 pandemic on the field of hematopoietic cell transplantation (HCT) remains unknown. To understand this better, an 18-item online survey was disseminated by the Worldwide Network for Blood & Marrow Transplantation with questions exploring SARS-CoV-2 testing algorithms, mobilization, and cryopreservation strategies and COVID-19 infections in allogeneic related and autologous hematopoietic progenitor cell (HPC) donors. The aim of this survey was to assess the impact of the outbreak on policies relating to HPC mobilization, collection, and processing with respect to changes in daily routine. A total of 91 individual responses from distinct centers in 6 continents were available for analysis. In these centers, the majority (72%) of allogeneic related and autologous donors are routinely tested for SARS-CoV-2 before HPC collection, and 80% of centers implement cryopreservation of allogeneic HPC grafts before commencing conditioning regimens in patients. Five related and 14 autologous donors who tested positive for COVID-19 did not experience any unexpected adverse events or reactions during growth factor administration (eg, hyperinflammatory syndrome). These data are limited by the small number of survey respondents but nonetheless suggest that centers are following the recommendations of appropriate scientific organizations and provide some preliminary data to suggest areas of further study

Acute graft versus host disease

Acute graft-versus-host disease (GVHD) occurs after allogeneic hematopoietic stem cell transplant and is a reaction of donor immune cells against host tissues. Activated donor T cells damage host epithelial cells after an inflammatory cascade that begins with the preparative regimen. About 35%–50% of hematopoietic stem cell transplant (HSCT) recipients will develop acute GVHD. The exact risk is dependent on the stem cell source, age of the patient, conditioning, and GVHD prophylaxis used. Given the number of transplants performed, we can expect about 5500 patients/year to develop acute GVHD. Patients can have involvement of three organs: skin (rash/dermatitis), liver (hepatitis/jaundice), and gastrointestinal tract (abdominal pain/diarrhea). One or more organs may be involved. GVHD is a clinical diagnosis that may be supported with appropriate biopsies. The reason to pursue a tissue biopsy is to help differentiate from other diagnoses which may mimic GVHD, such as viral infection (hepatitis, colitis) or drug reaction (causing skin rash). Acute GVHD is staged and graded (grade 0-IV) by the number and extent of organ involvement. Patients with grade III/IV acute GVHD tend to have a poor outcome. Generally the patient is treated by optimizing their immunosuppression and adding methylprednisolone. About 50% of patients will have a solid response to methylprednisolone. If patients progress after 3 days or are not improved after 7 days, they will get salvage (second-line) immunosuppressive therapy for which there is currently no standard-of-care. Well-organized clinical trials are imperative to better define second-line therapies for this disease. Additional management issues are attention to wound infections in skin GVHD and fluid/nutrition management in gastrointestinal GVHD. About 50% of patients with acute GVHD will eventually have manifestations of chronic GVHD

Apoptotic cell-based therapies against transplant rejection: role of recipient’s dendritic cells

One of the ultimate goals in transplantation is to develop novel therapeutic methods for induction of donor-specific tolerance to reduce the side effects caused by the generalized immunosuppression associated to the currently used pharmacologic regimens. Interaction or phagocytosis of cells in early apoptosis exerts potent anti-inflammatory and immunosuppressive effects on antigen (Ag)-presenting cells (APC) like dendritic cells (DC) and macrophages. This observation led to the idea that apoptotic cell-based therapies could be employed to deliver donor-Ag in combination with regulatory signals to recipient’s APC as therapeutic approach to restrain the anti-donor response. This review describes the multiple mechanisms by which apoptotic cells down-modulate the immuno-stimulatory and pro-inflammatory functions of DC and macrophages, and the role of the interaction between apoptotic cells and APC in self-tolerance and in apoptotic cell-based therapies to prevent/treat allograft rejection and graft-versus-host disease in murine experimental systems and in humans. It also explores the role that in vivo-generated apoptotic cells could have in the beneficial effects of extracorporeal photopheresis, donor-specific transfusion, and tolerogenic DC-based therapies in transplantation

Diagnosis and staging of chronic graft-versus-host disease in the clinical practice.

Based on expert opinion and retrospective data the National Institutes of Health (NIH) Consensus Development Project proposed criteria for diagnosis and staging of both overall severity as well as organ severity of chronic graft-versus-host disease (cGVHD) for use in clinical trials. In 2008, representatives of German and Austrian allogeneic hematopoietic stem cell transplant (HSCT) centers established a study group on cGVHD during the annual meeting of the German Working Group on Bone Marrow and Blood Stem Cell Transplantation (DAG-KBT) to intensify a dialog among HSCT physicians, pathologists, and medical consultants focusing on the usefulness of the NIH consensus criteria for patient care in clinical practice and to promote collaborations between HSCT centers as well as different medical specialities involved in HSCT. We first conducted a survey of current practices of diagnosis, staging, and overall grading of cGVHD in daily clinical routine by sending an electronic questionnaire to the heads of the HSCT centers. During 3 meetings in 2009, more representatives of allogeneic HSCT centers were included into the discussion process, resulting in 81% participation representing 88% of all allogeneic HSCT activities in Germany, Austria, and Switzerland. During the third consensus meeting held in Regensburg, Germany, from November 6 to November 7, 2009, important agreements were achieved among participant having a strong impact on care of patients with cGVHD. Areas of disagreement such as distinction between classical NIH cGVHD and overlap syndrome or assignment of liver GVHD after day 100 to acute or chronic category will be further assessed in prospective observational studies among participants in the near future

Progressive improvement in cutaneous and extracutaneous chronic graft-versus-host disease after a 24-week course of extracorporeal photopheresis--results of a crossover randomized study.

In a prior multicenter randomized controlled trial, we found that a 12-week course of extracorporeal photopheresis (ECP) plus standard immunosuppressive therapy resulted in several beneficial outcomes in patients with corticosteroid-refractory/intolerant/dependent chronic graft-versus-host disease (GVHD). Here, we report the results of an open-label crossover ECP study in 29 eligible participants randomized initially to the standard of care non-ECP (control) arm. Eligible for the crossover ECP study were control arm patients who either (1) had progression of cutaneous chronic GVHD (cGVHD), defined as>25% worsening from baseline as measured by the percent change in the total skin score (TSS) at any time, or (2) had less than 15% improvement in the TSS, or had a=50% reduction in corticosteroid dose at weeks 12 and 24 was observed. Extracutaneous cGVHD response was highest in oral mucosa with 70% complete and partial resolution after week 24. In conclusion, progressive improvement in cutaneous and extracutaneous cGVHD was observed after a 24-week course of ECP in patients who previously had no clinical improvement or exhibited worsening of cGVHD while receiving standard immunosuppressive therapy alone in a randomized study. These results confirm previous findings and support the notion that prolonged ECP appears to be necessary for optimal therapeutic effects in corticosteroid-refractory cGVHD patients

Specific growth inhibition of primitive hematopoietic progenitor cells mediated through monoclonal antibody binding to major histocompatibility class II molecules

In a previous study using a canine model, we reported that a certain anti-class II monoclonal antibody (MoAb H81.9), which recognizes an epitope formed by the alpha and beta subunits of HLA-DR, prevented long- term engraftment of autologous marrow cells if administered intravenously during the first 4 days after 9.2 Gy of total body irradiation. Another MoAb (B1F6), reactive with only the beta subunit of HLA-DR and -DP, had no adverse effect on engraftment, although both MoAbs detect antigens on hematopoietic long-term repopulating cells as determined from complement-mediated lysis experiments. In the present study, continuous exposure of unfractionated human marrow to MoAb H81.9 specifically inhibited the growth of primitive progenitor cells that require multiple hematopoietic growth factors for proliferation (high proliferative potential colony forming cells [HPP-CFC] and burst- forming units-erythroid [BFU-e]), but had no effect on more mature, single factor responsive (CFU-GM), progenitor cells. In contrast, MoAb B1F6 did not impair primitive progenitor cell growth cultured as unfractionated marrow. However, when cell dose-response experiments were performed using CD34-positive cells plated at low cell densities, the marked inhibitory effects of MoAb H81.9 on HPP-CFC and BFU-e colony formation were not seen. These findings suggest that MoAb H81.9 may not inhibit primitive hematopoietic cells directly, but rather indirectly through the action of potent mediators derived from other HLA-DR- positive marrow cells.</jats:p