Autologous bone marrow transplantation in acute leukemia

Gene and virotherapy for hematological malignancies

Recent years have seen a transformation in the treatment of hematological malignancies. Advances in gene therapy and molecular techniques and significant gains in computational abilities have supported the rapid development of safer and better tolerated therapies for many patients with hematologic cancers. In this review, we discuss novel applications of gene therapy, including immunomodulation and gene silencing, and report on the rise of oncolytic viruses for use in the treatment of malignancies arising in cells of the blood, lymph, and marrow. We discuss the relationship of the tropism of wildtype viruses and their oncolytic behavior as well as the tumoricidal and immunostimulatory properties of a number of attenuated and recombinant viruses currently in clinical development in countries around the world. While we have focused on promising virotherapy applications for future development, we also present a historical perspective and identify areas of potential clinical and regulatory practice change. We outline several of the virus systems being developed for applications in hematology, and summarize efficacy data in the context of ongoing or future human clinical testing. We also present the advantages and limitations of gene and virus therapy, including challenges and opportunities for improved treatment tolerability and outcomes for patients with hematologic malignancies.

Induction of apoptosis and effect on CD20+ using rituximab on autologous peripheral blood stem cell harvests from patients with B cell lymphomas

Purging of neoplastic cells for autologous stem cell transplantation is usually done in vivo by administering chemotherapy and/or other agents before harvesting. It is also possible to decrease malignant cells counts directly in the cell harvest. In this study, we ascertained the effect of anti-CD20 monoclonal antibody and rituximab administration on peripheral blood hematopoietic stem cells. Five samples of stem cell harvests from different patients with B cell lymphoma were obtained. Each sample was divided in two tubes with calcium gluconate (20 mEq/50 microl). Rituximab (1 mg/600,000 mononuclear cells) was added to one of the tubes. Using flow cytometry, CD19, CD20 (B cell markers), and CD95 (apoptosis marker), expression was measured at baseline and 24 h after the addition of rituximab. A one-sided t-test with equal variances was used to analyze the results. Immediately after rituximab addition, CD20 expression became null. No significant difference in variation of CD19 expression was detected after the addition of rituximab (-3.64% control vs. 0.63% rituximab, p = 0.69). Mean variations of percentage of CD95 expression were 2.9% (controls) and 10.52% (rituximab tubes) (p = 0.06). We conclude that rituximab is capable of initiating apoptosis in vitro. We found no decrease in the CD19+ cell count, used as a surrogate marker for CD20+ cells, meaning that, at least in 24 h, apoptosis activation is not capable of decreasing CD20+ cell numbers. In vitro purging of peripheral blood stem cells harvests with rituximab could be part of a broader therapeutic strategy to be offered to lymphoproliferative disorder patients.

Composite vascularized skin/bone graft model: A viable source for vascularized bone marrow transplantation

In this study, we introduce a new model for vascularized skin and bone marrow transplantation. Twenty-five Lewis (RT1(1)) rats were studied. Anatomic dissection studies were performed in 5 animals. In the experimental group, 10 isograft transplantations were performed between Lewis rats. Combined groin skin and femoral bone flaps were transplanted based on the femoral artery and vein. Transplants were evaluated on a daily basis. All flaps survived without problems over 100 days posttransplant. The skin component remained pink and pliable, and grew new hair. Histological examination of the femoral bone (except the femoral head) revealed active hematopoiesis with a viable compact and cancellous bone components on day 100 posttransplant. This model can be applied to tolerance induction studies across the major Histocompatibility (MHC) barrier, where bone will serve as donor of stem and progenitor cells, and the skin flap will serve as a monitor of graft rejection.

Long-term outcome of autologous transplantation of peripheral blood progenitor cells as postremission management of adult acute myelogenous leukemia in first complete remission

In order to improve leukemia-free survival (LFS) without the treatment-related morbidity of allogeneic bone marrow transplantation or multiple prolonged cycles of consolidation chemotherapy, we evaluated the long-term outcome of autologous transplantation of peripheral blood progenitor cells (PBPCs) as postremission therapy in 129 patients aged 18-71 years (median 49 years) with newly diagnosed acute myelogenous leukemia (AML) in first complete remission (CR1). The median follow-up from remission for surviving patients was 62.2 months (range 3.7-127.9 months). A total of 57 patients were alive and leukemia free at the end of the study. The LFS and overall survival 5 years from remission were 40.2% (+/-9.2%) and 41.4% (+/-9.4%), respectively. The median LFS and overall survival are 17.3 and 23.3 months, respectively. Multivariate analysis identified age as the most significant predictor for both LFS and overall survival. Karyotype was also found to be predictive of outcome. Our results show that autologous transplantation of PBPC procured after a single cycle of high-dose cytarabine-based consolidation chemotherapy for a population of adult patients with AML in CR1 produces a high likelihood of long-term LFS, offering a state of clinical minimal residual disease for the investigation of future therapeutic approaches.

Sensitivity of myeloid leukemia cells to calcium influx blockade: application to bone marrow purging

OBJECTIVE

The aim of this study was to assess the potential of store-operated Ca(2+) channel (SOC) antagonists as purging agents for leukemia cells.

MATERIALS AND METHODS

Clonogenic, limiting dilution, and nuclear condensation assays were used to evaluate SOC antagonist efficacy. SOC activity and endoplasmic reticulum Ca(2+) content were measured by flow cytometry. Murine bone marrow transplantation was used to determine purging efficacy and effects on hemopoietic reconstitution.

RESULTS

Econazole (Ec) and ketotifen (Ke) were variably effective against human and murine leukemia cell lines after 24 hours of incubation. However, a 2-hour serum and bovine serum albumin-free treatment protocol with Ec was found to maximize differential sensitivity between leukemic cells and normal hemopoietic progenitors. Primary acute myelogenous leukemia blast cell viability was reduced 4.2 to 5.1 logs by 2-hour Ec treatment as measured by limiting dilution. An inverse relationship between endoplasmic reticulum Ca(2+) content and Ke sensitivity in leukemia and untransformed cells was observed. Nuclear condensation, an index of apoptosis, which occurred after 24-hour treatments with either Ec or Ke, was not observed after 2-hour serum- and bovine serum albumin-free Ec exposures; however, condensed nuclei were observed after an additional 10-hour incubation in growth medium without drug. Using bone marrow deliberately contaminated with 1% P815 cells, we showed that highly effective in vitro purging can be accomplished using Ec with no adverse effects on bone marrow reconstitution in mice.

CONCLUSIONS

These studies suggest that SOC antagonists have potential as purging agents for residual leukemia cells present in bone marrow in the context of high-dose chemotherapy and autologous transplantation for leukemia.

Acute myelogenous leukemia: advances and limitations of treatment

Acute myelogenous leukemia (AML) describes a group of related hematologic malignancies that are being approached therapeutically from several perspectives. Conventional chemotherapeutic agents, such as anthracyclines and cytosine arabinoside (Ara-C), are useful in treating AML but now appear to have reached their maximum potential. Newer therapeutic approaches to AML have recently focused on immune-based therapy through monoclonal antibodies that target and destroy malignant cells via specific cell receptors. One such agent is gemtuzumab (CMA-676), an agent that targets the CD33 antigen on malignant myeloid cells. Initial studies have shown significant anticancer activity. We will discuss traditional and newer therapeutic approaches to AML and review the role of monoclonal antibody based therapies for patients with AML. A case of a 30-year-old man with refractory AML who was treated with gemtuzumab will be mentioned, highlighting potential applications and possible limitations to this novel therapy. Despite the effective reduction in the number of malignant cells in bone marrow, gemtuzumab ineffectively treated extramedullary leukemic gingival infiltrate. Regardless of limitations, monoclonal-based therapy offers an exciting and potentially safer adjunctive therapy for patients with AML.