C. Bachier

Ex-vivo expansion of bone marrow progenitor cells for hematopoietic reconstitution following high-dose chemotherapy for breast cancer

The use of hematopoietic growth factors, stromal monolayers, and frequent medium exchange allows the expansion of hematopoietic progenitors ex-vivo. We evaluated the use of ex-vivo expanded progenitor cells for hematopoietic reconstitution following high dose chemotherapy (HDC) in breast cancer patients. Patients with high-risk Stage II or metastatic breast carcinoma underwent bone marrow aspirations using general anesthesia. A total of 675-1125 x 10(6) mononuclear cells (MNC) were seeded for ex-vivo expansion for 12 days in controlled perfusion bioreactors (Aastrom Biosciences, Inc.). The bone marrow cultures, which included the stromal cells collected with the aspirate, were supplemented with erythropoietin, granulocyte-macrophage-colony stimulating factor (GM-CSF)/IL-3 fusion protein (PIXY 321), and flt3 ligand. Stem cell transplant was performed with expanded cells after HDC. A median bone marrow volume of 52.9 mL (range 42-187 mL) was needed to inoculate the bioreactors. Median fold expansion of nucleated cells (NC) and colony forming unit granulocyte-macrophage (CFU-GM) was 4.9 and 9.5, respectively. The median fold expansion of CD34+lin- and long-term culture-initiating culture (LTC-IC) was 0.42 and 0.32, respectively. Five patients were transplanted with ex-vivo expanded NC. Median days to an absolute neutrophil count > 500/microL was 18 (range 15-22). Median days to a platelet count > 20,000/microl was 23 (range 19-39). All patients had sustained engraftment of both neutrophils and platelets. Immune reconstitution was similar to that seen after HDC and conventional stem cell transplantation. We conclude that ex-vivo expansion of progenitor cells from perfusion cultures of small volume bone marrow aspirates, allows hematopoietic reconstitution after HDC.

Phase I and pharmacokinetic study of once-daily dosing of intravenously administered busulfan in the setting of a reduced-intensity preparative regimen and allogeneic hematopoietic stem cell transplantation as immunotherapy for renal cell carcinoma.

We performed a Phase I and pharmacokinetic study of once-daily, intravenously administered busulfan in the setting of a reduced-intensity preparative regimen and matched sibling donor allogeneic stem cell transplantation for treatment of metastatic renal cell carcinoma. Seven male patients with metastatic renal cell carcinoma received intravenously administered busulfan at 3.2 mg/kg once daily on day -10 and day -9, fludarabine at 30 mg/m2 on day -7 through day -2, and equine antithymocyte globulin at 15 mg/kg per day on day -5 through day -2. The mean area under the plasma concentration-time curve (AUC) and the half-life of the first dose of intravenously administered busulfan were 6,253 microM x minute (range, 5,036-7,482 microM x minute) and 3.37 hours (range, 2.54-4.00 hours), respectively. The AUC was higher than predicted from extrapolation of AUC data for the same total dose of intravenously administered busulfan divided into four doses daily. Patients experienced greater than expected regimen-related toxicity for a reduced-intensity preparative regimen, and the study was stopped. In conclusion, this preparative regimen was associated with unacceptable regimen-related toxicity among patients with metastatic renal cell carcinoma.

Immunotoxin Therapy of Cancer

Immunotoxin conjugates are potent cytotoxic agents. They are composed of toxins from plants or bacteria linked chemically or by protein engineering to antibodies or ligands that target cell surface structures present in malignant cells. Their cytoxicity is based on blocking protein synthesis. Studies in vitro and in animals have shown significant tumour cytotoxicity with minimal toxicity to normal tissues. Their novel mechanism of action, cell cycle independence, tumour specificity and low toxicity profile have made immunotoxins attractive candidates for use in clinical trials. Results from phase I/II studies of immunotoxins incorporating ricin, Pseudomonas exotoxin and diphtheria toxin have demonstrated the feasibility of this approach, especially in patients with leukaemias and lymphomas. Recent advances have made possible modifications in immunotoxin structure, resulting in even more potent and/or less immunogenic molecules. However, several obstacles must still be overcome such as: (a) immune-mediated neutralisation of the conjugate; (b) penetration of bulky tumours; and (c) intrinsic tumour resistance. Areas of future clinical investigation will include clinical trials with newer conjugates, treatment of malignancies at a state of minimal disease, and combination of immunotoxins and other chemotherapeutic agents. These studies will define the role of immunotoxins in the therapy of cancer.