POSTER NO: 183

The in vivo study on the protective function of multidrug resistance gene (mdr-1) transduced in hematopoietic progenitor cells in mice

Zi-xing Chen, Jian-nong Cen, Xiao-wei Yang, Jian-xin Fu
Jiangsu Institute of Hematology, 1st Affiliated Hospital Soochow University, 96 Shizi Street, Taipei, Taiwan, China

To study whether the mdr-1 gene which has been transduced into hematopoitic cells could play a role in protecting the hematopoietic function of the mice from chemotherapeutic agents, the bone marrow cells of BALB/C mice pretreated with 5-FU were transfected by supernatant of a retrovirus producing cell GP+E86/mdr-1 in presence of 20ng/ml of rmSCF, 20ng/ml of rm IL-3 and 20ng/ml of rhIL-6. The transduction efficiency was determined by colony forming assay. The BM cells then were transplanted into recipient mice who have previously irradiated with 8.5Gy of 60Co. The peripheral white cells were counted every 3 days until the recovery of hematopoiesis in the mice. As the white cell count increased to normal level, 10mg/kg of DNR was injected intraperitoneally to the mouse. 15 days later, the mouse was sacrificed to check for spleen nodules. The integration of the exogenous human mdr-1 in cells of peripheral blood, bone marrow, spleen, liver, kidney and heart was examined by PCR at 15, 30 and 60 days, respectively, after the drug challenge. The mdr-1 expression was determined by flow cytometry. The hematopoietic reconstitution could be detected in mouse 15 days after transplantation and the blood cell count increased to almost normal level after 25 days. The survival time in these mice was longer than 60 days. The integration of human mdr-1 gene could be detected by PCR in cells from peripheral blood, bone marrow and spleen nodules of the recipient mice at 15 and 30 days after transplantation. 10% of CFU-GM colonies formed by reconstituted bone marrow cells were mdr-1 positive. In mice who had been transplanted with mdr-1 gene transduced cells and subsequently exposed to DNR, the body weight, peripheral white count and survival time generally remained unchanged while 30-40% of mice in control group died following a substantial decrease of body weight and white count after the DNR was given. On 60th day after transplantation, the cells from various organs in mice challenged with DNR could still be detected as human mdr-1 positive while that became undetectable in mice without exposure to DNR. Our results indicated that the hematopoietic reconstitution in recipient mouse can be achieved by progenitor blood cells transduced with human mdr-1 gene. These mdr-1 positive bone marrow cells protect the hematopoietic function in animals from chemotherapeutic drugs to a certain degree. The mdr-1 positive blood cell clones can be selectively enriched and retained longer in the body by exposure to chemotherapeutic drugs.