A pilot study of dose-intensified procarbazine, CCNU, vincristine for poor prognosis brain tumors utilizing fibronectin-assisted, retroviral-mediated modification of CD34+ peripheral blood cells with O6-methylguanine DNA methyltransferase

Abstract

Administration of chemotherapy is often limited by myelosuppression. Expression of drug-resistance genes in hematopoietic cells has been proposed as a means to decrease the toxicity of cytotoxic agents. In this pilot study, we utilized a retroviral vector expressing methylguanine DNA methyltransferase (MGMT) to transduce hematopoietic progenitors, which were subsequently used in the setting of alkylator therapy (procarbazine, CCNU, vincristine (PCV)) for poor prognosis brain tumors. Granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood progenitor cells were collected by apheresis and enriched for CD34 þ expression. Nine subjects were infused with CD34 þ -enriched cells treated in a transduction procedure involving a 4-day exposure to cytokines with vector exposure on days 3 and 4. No major adverse event was related to the gene therapy procedure. Importantly, the engraftment kinetics of the treated product was similar to unmanipulated peripheral blood stem cells, suggesting that the ex vivo manipulation did not significantly reduce engrafting progenitor cell function. Gene-transduced cells were detected in all subjects. Although the level and duration was limited, patients receiving cells transduced using fibronectin 'preloaded' with virus supernatant appeared to show improved in vivo marking frequency. These findings demonstrate the feasibility and safety of utilizing MGMT-transduced CD34 þ peripheral blood progenitor cells in the setting of chemotherapy.

In vitroerythropoiesis from bone marrow-derived progenitors provides a physiological assay for toxic and mutagenic compounds

“…The BM is often the dose-limiting tissue in chemotherapy and radiotherapy regimens, and therapy-related anemia, cytopenia, and leukemia are common side effects. These serious morbidities have prompted efforts to increase hematopoietic DNA repair capacity through gene therapy in patients receiving chemotherapeutic agents and to improve preclinical screening of new drugs for genotoxic effects (4)(5)(6)(7)(8)(9). Although leukemias and cytopenias arise in white cell populations, erythrocyte populations serve as a useful system to measure DNA damage because normal and micronucleated PCEs are easily recognized and scored by microscopy, flow cytometry, and laser scanning cytometry (10-13).…”

Protection of Mice from Methotrexate Toxicity by ex Vivo Transduction Using Lentivirus Vectors Expressing Drug-Resistant Dihydrofolate Reductase

“…Clinical testing of drug-resistance genes has included introduction of the MDR1 gene as a means of protecting against the toxicity of paclitaxel chemotherapy (Abonour et al, 2000, and references therein) and introduction of the methylguanine methyltransferase gene to confer resistance to alkylating agents (Cornetta et al, 2006). These studies have targeted human CD34 ϩ hematopoietic stem cells using retroviral vectors for introduction of the MDR1 or O 6 -methylguanine-DNA methyltransferase genes.…”

In vivo selection of human embryonic stem cell-derived cells expressing methotrexate-resistant dihydrofolate reductase

“…However, in cases where the gene-of-interest does not confer a selective advantage to modified cells, drug resistance gene expression in HSCs may be clinically beneficial. For example, drug resistance gene expression coupled to chemotherapy has been shown to selectively expand gene-modified cells in vivo 6–8. In addition, drug resistance gene expression in nonmalignant chemosensitive tissues, such as the bone marrow and gastrointestinal tract, has the potential to decrease toxicity associated with high-dose chemotherapy7.…”