C. HESDORFFER 4/93 
be small since they will be undetectable by morphologic and cell 
sorting techniques in order for the patient to qualify for the 
protocol. Secondly, even if transduced with the transferred MDR 
gene, these residual cells would also require the proliferative 
and other biological characteristics that could make them the 
precursors of a relapsing population of tumor cells. Thirdly, 
with treatment with MDR-responsive drugs, either prior to 
chemotherapy or after exposure to taxol posttransduction, a 
population of tumor cells with high levels of endogenous MDR may 
well be selected since this is a common mechanism of drug 
resistance to tumors. This is indeed the rationale for treating 
breast cancer with agents other than MDR-responsive agents such 
as alkylating agents including melphalan and cyclophosphamide, 
and carboplatinum, thiotepa, 5-f luorouracil and nitrosoureas. In 
the case that this protocol led to the proliferation of an MDR- 
transduced residual breast cancer cell population in the marrow, 
treatment with combinations of these non-MDR responsive drugs 
will be used as would be the case with MDR resistance in a non- 
transduced patient. We will monitor the MDR content of marrow 
and tumor cells both pre- and post ABMT by measuring transferred 
MDR genes by PCR and MDR expression by FACS sorting in marrow 
specimens and all available tumor samples, respectively. 
6 . HUMAN SUBJECTS : 
With this protocol, we will embark on human studies in which 
the MDR gene is transferred into autologous human bone marrow 
cells prior to reinfusion back into these patients. The use of 
retroviral gene transfer into lymphocytes of patients has been 
reported and has demonstrated no toxic side effects to date (76- 
78) . We will evaluate the safety of gene transfer by looking for 
the presence of intact retrovirus in the bone marrow of MDR- 
transduced patients. This is the major risk of these studies. 
In addition, we will use the assays for human MDR at the DNA, 
RNA, and protein levels described earlier to determine the extent 
of expression of the MDR gene in human bone marrow cells in vitro 
and eventually in vivo in human subjects. 
A. Detailed Description of The Proposed Involvement of 
Human Subjects : 
The initial patients whose cells will be transduced 
with the MDR gene will be those undergoing ABMT for advanced 
cancers not involving the bone marrow. In these patients, MDR 
gene transfer and expression and potential toxicity will be 
assessed. In breast and ovarian cancer patients subsequently 
receiving high-dose adriamycin or taxol, the potential effect of 
MDR expression in reducing bone marrow toxicity will be measured. 
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Recombinant DNA Research, Volume 18 
