ALBERT

Description: Gaucher disease is an inherited lysosomal storage disease in which the loss in functional activity of glucocerebrosidase (GC) results in the storage of its lipid substrate in cells of the macrophage lineage. A gene therapy approach involving retroviral transduction of autologous bone marrow (BM) followed by transplantation has been recently approved for clinical trial. Amelioration of the disease symptoms may depend on the replacement of diseased macrophages with incoming cells expressing human GC; however, the processes of donor cell engraftment and vector gene expression have not been addressed at the cellular level in relevant tissues. Therefore, we undertook a comprehensive immunohistologic study of macrophage and microglia replacement after murine BM transplantation with retrovirus-marked BM. Serial quantitative PCR analyses were employed to provide an overview of the time course of engraftment of vector-marked cells in a panel of tissues. Following reconstitution of hematopoietic tissues with vector- marked donor cells at early stages, GC+ cells began to infiltrate the liver, lung, brain, and spinal cord by 3 months after transplant. Immunohistochemical analyses of PCR+ tissues using the 8E4 monoclonal antibody specific for human GC revealed that macrophages expressing human GC had partially reconstituted the Mac-1+ population in all tissues in a manner characteristic to each tissue type. In the brain, 20% of the total microglia had been replaced with donor cells expressing GC by 3 to 4 months after transplant. The finding that significant numbers of donor cells expressing a retroviral gene product immigrate to the central nervous system suggests that gene therapy for neuronopathic forms of lysosomal storage diseases as well as antiviral gene therapy for AIDS may be feasible.

Description: We have developed a novel cotransplantation system in which gene- transduced human CD34+ progenitor cells are transplanted into immunodeficient (bnx) mice together with primary human bone marrow (BM) stromal cells engineered to produce human interleukin-3 (IL-3). The IL- 3-secreting stroma produced sustained circulating levels of human IL-3 for at least 4 months in the mice. The IL-3-secreting stroma, but not control stroma, supported human hematopoiesis from the cotransplanted human BM CD34+ progenitors for up to 9 months, such that an average of 6% of the hematopoietic cells removed from the mice were of human origin (human CD45+). Human multilineage progenitors were readily detected as colony-forming units from the mouse marrow over this time period. Retroviral-mediated transfer of the neomycin phosphotransferase gene or a human glucocerebrosidase cDNA into the human CD34+ progenitor cells was performed in vitro before cotransplantation. Human multilineage progenitors were recovered from the marrow of the mice 4 to 9 months later and were shown to contain the transduced genes. Mature human blood cells marked by vector DNA circulated in the murine peripheral blood throughout this time period. This xenograft system will be useful in the study of gene transduction of human hematopoietic stem cells, by tracing the development of individually marked BM stem cells into mature blood cells of different lineages.

Description: Gaucher disease is an inherited lysosomal storage disease in which the loss in functional activity of glucocerebrosidase (GC) results in the storage of its lipid substrate in cells of the macrophage lineage. A gene therapy approach involving retroviral transduction of autologous bone marrow (BM) followed by transplantation has been recently approved for clinical trial. Amelioration of the disease symptoms may depend on the replacement of diseased macrophages with incoming cells expressing human GC; however, the processes of donor cell engraftment and vector gene expression have not been addressed at the cellular level in relevant tissues. Therefore, we undertook a comprehensive immunohistologic study of macrophage and microglia replacement after murine BM transplantation with retrovirus-marked BM. Serial quantitative PCR analyses were employed to provide an overview of the time course of engraftment of vector-marked cells in a panel of tissues. Following reconstitution of hematopoietic tissues with vector- marked donor cells at early stages, GC+ cells began to infiltrate the liver, lung, brain, and spinal cord by 3 months after transplant. Immunohistochemical analyses of PCR+ tissues using the 8E4 monoclonal antibody specific for human GC revealed that macrophages expressing human GC had partially reconstituted the Mac-1+ population in all tissues in a manner characteristic to each tissue type. In the brain, 20% of the total microglia had been replaced with donor cells expressing GC by 3 to 4 months after transplant. The finding that significant numbers of donor cells expressing a retroviral gene product immigrate to the central nervous system suggests that gene therapy for neuronopathic forms of lysosomal storage diseases as well as antiviral gene therapy for AIDS may be feasible.

Description: As has been reported with other chemotherapeutic agents, evidence is emerging to suggest that increased taxol dose intensity is associated with improved therapeutic efficacy. Granulocyte colony-stimulating factor (G-CSF) effectively protects the bone marrow from taxol-induced neutropenia and allows for higher taxol dose administration. This report addresses the optimal use of G-CSF as a supportive agent for dose-intense taxol therapy. Forty-seven patients were evaluated. Each ovarian cancer patient received taxol with G-CSF support, with starting doses of 250 mg/m2 per 21 days and 10 micrograms/kg/d, respectively. Five patients were treated with the same dose of G-CSF for multiple cycles. Forty-two patients were given “flexibleflexible” G-CSF dosing. Instead of reducing taxol dose after a cycle of therapy complicated by febrile neutropenia (F+N+), the G-CSF dose was increased. Only after a second episode of F+N+ was the taxol dose reduced. The initial 5 patients who developed F+N+ after taxol (250 mg/m2) and G-CSF (10 micrograms/kg/d) were retreated at the same doses of both drugs; subsequently, 4 of 5 patients had another episode of F+N+. With flexible G-CSF dosing, taxol dose intensity could be maintained at the target level in 34 of 42 patients (81% of the cohort). Sixteen of these patients (38% of the cohort) would have required taxol dose reductions for F+N+ if flexible G-CSF dosing had not been used. By increasing the G-CSF dose when indicated, patients at high risk for recurrence of F+N+, because they had already experienced one episode, appeared to have a lower risk of developing a recurrent episode. These data suggest that flexible G-CSF dosing may have merit and may allow the administration of more dose- intense taxol. A prospective, randomized, controlled clinical trial of flexible G-CSF dosing versus fixed-dose G-CSF appears warranted.

Description: As has been reported with other chemotherapeutic agents, evidence is emerging to suggest that increased taxol dose intensity is associated with improved therapeutic efficacy. Granulocyte colony-stimulating factor (G-CSF) effectively protects the bone marrow from taxol-induced neutropenia and allows for higher taxol dose administration. This report addresses the optimal use of G-CSF as a supportive agent for dose-intense taxol therapy. Forty-seven patients were evaluated. Each ovarian cancer patient received taxol with G-CSF support, with starting doses of 250 mg/m2 per 21 days and 10 micrograms/kg/d, respectively. Five patients were treated with the same dose of G-CSF for multiple cycles. Forty-two patients were given “flexibleflexible” G-CSF dosing. Instead of reducing taxol dose after a cycle of therapy complicated by febrile neutropenia (F+N+), the G-CSF dose was increased. Only after a second episode of F+N+ was the taxol dose reduced. The initial 5 patients who developed F+N+ after taxol (250 mg/m2) and G-CSF (10 micrograms/kg/d) were retreated at the same doses of both drugs; subsequently, 4 of 5 patients had another episode of F+N+. With flexible G-CSF dosing, taxol dose intensity could be maintained at the target level in 34 of 42 patients (81% of the cohort). Sixteen of these patients (38% of the cohort) would have required taxol dose reductions for F+N+ if flexible G-CSF dosing had not been used. By increasing the G-CSF dose when indicated, patients at high risk for recurrence of F+N+, because they had already experienced one episode, appeared to have a lower risk of developing a recurrent episode. These data suggest that flexible G-CSF dosing may have merit and may allow the administration of more dose- intense taxol. A prospective, randomized, controlled clinical trial of flexible G-CSF dosing versus fixed-dose G-CSF appears warranted.