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Transplant: Past Present and Future

Transplant: Past Present and Future. John McCarty M.D. Medical Director Bone Marrow Transplantation Program Massey Cancer Center VCU Health Systems/MCV Hospitals and Physicians May 7, 2008. Introduction. History of stem cell transplantation Definition and biology of stem cells by source

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Transplant: Past Present and Future

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  1. Transplant: Past Present and Future John McCarty M.D. Medical Director Bone Marrow Transplantation Program Massey Cancer Center VCU Health Systems/MCV Hospitals and Physicians May 7, 2008

  2. Introduction • History of stem cell transplantation • Definition and biology of stem cells by source • Practical aspects of the transplant process • Future directions of BMT

  3. Highlights in Stem Cell Transplant • Studies of atomic bomb victims showed marrow most sensitive to radiation • Splenic shielding protected mice from radiation • Bone marrow infusion rescued mice from radiation • Murine and canine models developed for transplant • Discovery that immune response controlled by genetic factors (histocompatibility factors) • Marrow from histocompatible animals rescues from lethal radiation

  4. Highlights in Stem Cell Transplant • 1957: marrow safely infused intravenously • 1958: reports of successful identical twin transplants • 1969: Cytoxan added to radiation • 1970: bone marrow harvests perfected to obtain stem cells • 1989: peripheral blood stem cells harvested • 1990: first successful cord blood transplant • 1996: first non-ablative transplant Thomas et al J Clin Invest 1959

  5. What are Stem Cells? • Not characteristics of specific tissues • Divide for the lifetime of the organism • Can replenish themselves • Stem cells as “seed cells” for the body • Stem cells may exist in all organs • Serve in injury repair • “trust fund” to replace cells as they die off • Stem cells may circulate from one tissue reserve to another?

  6. Sources of Stem Cells • Three main types of stem cells • Adult stem cells • Main reservoir in the bone marrow • Cord blood stem cells • Circulating stem cells in umbilical cord blood • Embryonic stem cells • Derived from fertilized embryos during early phases of development

  7. Adult Stem Cells • Replenish cells lost through age or injury • Largest reservoir in marrow • Stem cells circulate in blood • “Relocate” to fill empty stem cell slots in other tissues • Harvested from bone marrow or peripheral blood in stem cell transplants since late 1970’s • Stem cells isolated from: • Skin, brain, prostate, muscle

  8. Umbilical Cord Blood Stem Cells • Obtained from blood retained in the umbilical cord and placenta after delivery • Has been used in stem cell transplants since the late 1980’s • Most often used in children and small adults • Potential role for double cord transplants in adults

  9. Cancer: Leukemia Myelodysplasia Lymphoma Breast cancer Testicular cancer Ovarian cancer Brain tumors Pediatric tumors Multiple myelomas Sarcomas Kidney cancers Non Cancers: Autoimmune diseases Rheumatoid arthritis Juvenile and adult Multiple Sclerosis Scleroderma Systemic Lupus Immune deficiency Sickle cell anemia Thalassemia Indications for Stem Cell Transplants

  10. 45,000 40,000 35,000 Autologous 30,000 25,000 NUMBER OF TRANSPLANTS 20,000 15,000 10,000 Allogeneic 5,000 0 1970 1975 1980 1985 1990 1995 2000 YEAR Annual Numbers Of Blood And Marrow Transplants Worldwide 1970-2002

  11. Bone Marrow (BM) Peripheral Blood (PB) Cord Blood (CB) Bone Marrow (BM) Peripheral Blood (PB) Cord Blood (CB) Age £20 yrs Age >20 yrs Stem Cell Sources By Recipient Age 1997-2004

  12. Practical BMT • Two main types based on source of stem cells • Autologous: no immunologic conflict • Stem cell infusion as “rescue” from high dose chemo • “marrow lethal dose” • Allogeneic: Minor HLA disparity • Related • Unrelated • Cord blood • High dose therapy with immunotherapy • “rejection” of the cancer and building better immunity

  13. Elements of Stem Cell Transplants • Selection of donor • Based on tissue typing of 6-10 HLA antigens in allogeneic transplantation • Tissue typing unnecessary in autologous transplantation • Harvest of stem cells from donor • Bone marrow harvest or pheresis of peripheral blood • Preparative regimen • Chemo-radiation for ablation and immune suppression • Stem cell infusion • Post-transplant supportive care • Autologous 100 days • Allogeneic 180 days or longer for tolerance to develop

  14. Patient Evaluation • Recipient Age • Autologous: “0” to 70 years • Allogeneic: • Matched Related 55-60 years • Mismatched or Unrelated Donor: 50-55 years • Risk of GVHD significantly increased age >45 • Dose-Adjusted Transplantation for older, or ill patients • Reduced intensity myeloablative • Non-myeloablative • Indicated based on extensive pre-transplant evaluation for candidacy • Patients up to age 70 may be eligible for allogeneic transplant

  15. Preparation for BMT • Immune suppression and myeloablation required • Bone marrow failure states require more immunosuppression • Immune deficiency without empty marrow leads to rejection. • Chemotherapy induces aplasia to allow engraftment • Additional merits of marrow ablation • Provides marrow “space” • Eradicates malignant cells • Reset of the recipient immune system • Preparative regimens before transplant provide aplasia and immune suppression

  16. HLA and Marrow Transplantation • Histocompatibility Locus Antigens (HLA) are determinants of immunologic “self” and “not-self” • Immunologic “password” • Allows for effective immune response against infections, cancer • T cell reaction to foreign HLA molecules (donor) is a major problem of transplantation (alloreactivity) • Need good donor and recipient match for HLA sites • Cause of acute rejection in organ transplant, and of GVHD in BMT.

  17. HLA Typing in BMT • Family members typed with patient for HLA A, B and DR • Likelihood of 6/6 or 5/6 match depends on frequency of recipient HLA haplotype • Likelihood of unrelated donor match related to haplotype frequency in general population • Some HLA combinations more frequently found among ethnic groups • Ethnic sequestration phenomenon

  18. Ethnicity and Unrelated Donors

  19. Increasing Donor Pool Essential • Time from search to unrelated donor: 4 months • Often relapse prevents coming to transplant • Greater efforts are needed to increase participation and minority representation in the volunteer donor pool (NMDP) • Education regarding safety and need • Increasing cord blood donation may help some • Everyone has umbilical cord blood they won’t use • No risk to donate • Better reflects the local population demographics

  20. Harvesting Stem Cells • Adult stem cells obtained by large volume marrow biopsy/aspiration (1-2L) • Cord blood stem cells obtained at delivery by sterile emptying umbilical cord and placenta into blood donation bag • Increasingly obtained by processing of peripheral blood of patients and healthy donors • Isolated in “real time” from blood after stimulation with blood cell growth factors • Stem cells can be frozen for up to 5-10 years

  21. Practical BMT • Stem cells infused IV • “Home” to micro-environment niches in marrow and spleen • Recognition of arrays of adhesive and growth factors in marrow stroma • Donor T lymphocytes are essential to engraftment

  22. Hematopoietic Reconstitution • Bone marrow cellularity decreased months post transplant • Immunologic reconstruction over 100 days post transplant • Graft-vs.-host disease (GVHD) delays immune reconstitution • Immune deficits expected: • T cell and B cell dysfunction. • Low Ig levels for three months, normal IgG and IgM by one year, IgA by two year • Predisposes to fungal, viral and bacterial infection

  23. Transplantation Immunology • In solid organ transplantation, the main relevant immunologic process is graft rejection • In marrow transplantation, a novel immunologic condition arises due to the immunologic competence of the graft itself. • Rejection is bi-directional • Graft rejection • Graft-vs.-host disease (GVHD) • Tolerance develops, immunosuppression not lifelong

  24. Dendritic Cells Facilitating Cells Stem Cells, progenitors NK Cells T and B Lymphocytes Stem Cell Grafts are Complex Stem cell graft components T Lymphocyte functions GVHD GVL, grafting

  25. Pathophysiology of GVHD • Essential factors necessary for GVHD to occur: • Immunologically competent donor graft • Histo-incompatibility between donor and host • Immunologically incompetent host

  26. Graft-versus Malignancy Effect • Lower incidence of leukemic relapse in patients who get acute or chronic GVHD • Higher relapse rates in syngeneic vs. allogeneic BMT • High relapse rates in T cell depleted BMT • Cytogenetic remission induced after post BMT relapse of CML by infusion of donor leukocytes

  27. Nonmyeloablative Stem Cell Transplants as Immunotherapy • “Mini transplants”: less cytoablative therapy • host/donor marrow chimerism prominent • early studies effective in CML in patients up to 75 yrs • low level GVHD • if chimerism present, malignancy detectable (PCR): • reduction in immunosuppression • donor lymphocyte infusion • high remission re-induction rate • lower mortality/morbidity

  28. NST: Overview

  29. . NST: Graft versus Renal Cell Cancer 60 days post transplant 285 days post transplant Childs et al NEJM 2000

  30. Tandem Transplantation • Refers to the deliberate performance of two stem cell transplants within 3-4 months of each other • By intention, rather than by failure to respond • May consist of autologous-autologous or autologous-allogeneic • The latter allows separation of the high dose component from the immunotherapy component • Most often utilized in myeloma, testicular cancer, medulloblastoma, neuroblastoma • Response and risk adaptive approach used in myeloma

  31. Cost of BMT • Variable due to several factors: • Indication: AML<CML<NHL<AA • Complications: hospital days, blood products most $$ • Stem cell source: PBSC<Marrow (faster engraftment) • Preparative regimen: TBI expensive • Unrelated>>Allogeneic>Autologous • Average ABMT 84k-175k • Average AuBMT 70k-100k

  32. Cost Effectiveness of BMT • Welch (NEJM 1989): 41 patients with ALL • 17 w/ matched related donor • 19 w/ no donor; standard consolidation/maintenance • Costs for survivors (both arms) less than non-survivors • Incremental cost effectiveness (difference in cost/yrs survival): • BMT: survivor $166k, nonsurvivor $232k • Chemo: survivor $79k nonsurvivor $157k • More patients surviving after BMT • ICE of BMT $10k per year of life gained • Rx of moderate HTN $13.5k per year of life gained

  33. Long Term Complications • Infection risk prolonged with GVHD • Infertility (Women>>men, TBI>>HD Cytoxan) • Hypothyroid 15-25%; (TBI) • Cataracts (TBI, steroids) • AVN bone: (steroids) • Autoimmune dysfunction: (GVHD) • Dental: dry mouth, caries (GVHD, TBI) • Malignancy 5-6x increased risk PTLPD • Non hematologic cancer risks from TBI, Cytoxan

  34. New Directions I • Autoimmune diseases heterogenous with variable course • All have a basis in the stem cell • Main intervention is immunosuppression • Safety and side effect profile improving for stem cell transplant • Transplant considered in patients with severe AID • Life-threatening disease • Disease of major morbidity (diffuse Scleroderma) • unresponsive to standard therapy (Systemic Lupus) • Early in progressive relapse (Multiple Sclerosis) • Preparative regimens to include BU/CY/ATG • avoiding TBI reduces risk of secondary malignancy

  35. New Directions II • Stem cell transplantation as platform for directed therapies • Dendritic cell/NK cell immune therapy • Vehicle for cancer vaccine delivery • Use of specifically generated cytotoxic T cell lymphocyte responses • Against malignancy • Against infection • Enhance autologous Graft versus malignancy effect

  36. Developing Applications I • Induction of solid organ graft tolerance • In living donor solid organ transplants • Orthotopic liver • Kidney • Pancreatic islet cell • Tolerance to solid organ by subsequent NST transplantation • Patient as mixed chimera • Transplanted marrow and lymphocytes tolerate patient and recognize transplanted organ as “self”

  37. Developing Applications II • Heart disease • Heart muscle damaged by coronary heart disease or viral injury • Injection of stem cells into area of dead heart muscle regenerates viable muscle • Injection of stem cells promotes formation of new blood vessels in injured heart muscle • Can intracoronary or intravenous purified stem cell populations be given during cardiac catheterization?

  38. Stem Cells Repair Broken Hearts Orlic et al PNAS 2001

  39. Conclusions • Stem cells can be derived from adult, cord blood and eventually embryonic stem cells • Stem cell transplantation can both support highly intensive chemotherapy and promote highly effective immunotherapy • Recent advances in stem cell transplantation allow therapy more tailored to disease and patient • Improved supportive care measures expand transplant to more patients • Expanded applications capitalizing on stem cell plasticity are feasible

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