Recombinant DNA Advisory Committee - 12/3-4/92 
Review-Dr. Leventhal 
Dr. Murray called on Dr. Leventhal to present her primary review of the protocol 
submitted by Dr. Joyce O'Shaughnessy of the National Institutes of Health, Bethesda, 
Maryland. Dr. Leventhal summarized the objectives of the protocol. This protocol is 
designed to determine: (1) the effect of high dose chemotherapy and multi-drug 
resistance-one (MDR-1) transduced hematopoietic stem cells on autologous bone 
marrow (ABM) engraftment, (2) the potential of MDR-1 to be used as a dominant 
selectable marker, and (3) if MDR-1 expression in ABM cells provides protection against 
chemotherapy-induced myelosuppression. Patient eligibility will be limited to individuals 
with biologically documented metastatic breast cancer who have demonstrated either 
complete or partial response to conventional chemotherapy and who have no 
demonstrable tumor cells in their bone marrow. 
Patients will initially receive a single dose of both Cytoxan and granulocyte colony 
stimulating factor (G-CSF). When the patient's peripheral blood cell count reaches 2 x 
10 3 cells per milliliter (ml), peripheral blood stem cells (PBSC) will be harvested daily 
until 10 nucleated cells per kilogram body weight have been harvested. Two weeks 
following PBSC harvest, the ABM cells will be harvested. Seventy percent of these 
ABM cells will be cryopreserved, and the remaining 30% will be transduced with the 
MDR-1 gene. Following ABM harvest, patients will receive maximally tolerated doses of 
the chemotherapy agents ifosfamide, carboplatin, and etoposide (ICE) with MESNA. 
Following chemotherapy, patients will be reinfused with their cryopreserved cells; and 
the MDR-1 transduced cell population. Patients who demonstrate residual disease will 
receive either taxol or vinblastine. ABM sampling will be performed periodically to 
monitor for the presence of the MDR-1 gene. Any recurrent tumor will be assayed for 
the presence of the MDR-1 gene. In summary, the investigators will attempt to induce a 
higher level of chemotherapy resistance in ABM cells than in tumor cells. 
Dr. Leventhal stated that the majority of her questions and those of Dr. Brinckerhoff had 
been addressed by the investigators; however, there are still concerns about the assays 
that will be performed to determine MDR-1 expression. Although polymerase chain 
reaction (PCR) will provide useful information regarding gene transduction, no 
information will be obtained regarding gene expression. Since these patients have 
already received intensive chemotherapy, their tumor cells may already possess the MDR 
phenotype. Not enough animal experiments have been performed to support the 
scientific basis for this protocol. Also, gene expression should be addressed more 
thoroughly. An additional concern is the possibility of transducing residual tumor cells 
remaining in the ABM. How will the investigators distinguish between naturally 
occurring MDR resistance resulting from prior drug exposure and MDR resistance 
induced by the inserted gene? 
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Recombinant DNA Research, Volume 16 
