Improvement of combination chemotherapy tolerance by introduction of polycistronic retroviral vector drug resistance genes MGMT and MDR1 into human umbilical cord blood CD34+ cells.

We obtained a full-length cDNA fragment encoding human O(6)-methylguanine-DNA-methyltransferase (MGMT) from the liver tissue of a patient with cholelithiasis by RT-PCR and confirmed by DNA sequencing. The polycistronic retrovirus vector G1Na-MGMT-Neo(r)-IRES-MDR1 was constructed and verified by restriction endonuclease analysis and DNA sequencing. The vector was transfected into packaging cells GP+E86 and PA317 by the LipofectAMINE method. Cord blood CD34+ cells were transfected with the supernatant of retrovirus containing human MGMT and MDR1cDNA under stimulation of hematopoietic growth factors. PCR, RT-PCR, Southern Blot, Western Blot, FACS and MTT analyses showed that dual drug resistance genes have been integrated into the genomic DNA of cord blood CD34+ cells and expressed efficiently. The transgene cord blood CD34+ cells conferred 5.8-6.3-fold stronger resistance to P-glycoprotein effluxed drugs and 5-fold to BCNU than untransduced cells. The polycistronic retrovirus vector mediated transfer of two different types of drug resistance genes into human cord blood CD34+ cells and co-expression provided an experimental foundation for improving combination chemotherapy tolerance in clinical practice.