RETROVIRUS-MEDIATED GENE-TRANSFER OF RAT GLUTATHIONE-S-TRANSFERASE YCCONFERS IN-VITRO RESISTANCE TO ALKYLATING-AGENTS IN HUMAN LEUKEMIA-CELLS AND IN CLONOGENIC MOUSE HEMATOPOIETIC PROGENITOR CELLS

Recently, we have reported that N2Yc, a Moloney-based retrovirus vecto r expressing the Yc isoform of rat glutathione S-transferase (GST-Yc), conferred resistance to alkylating agents in mouse NIH-3T3 fibroblast s. In this report, we address the feasibility of using rat GST-Yc soma tic gene transfer to confer chemoprotection to the hematopoietic syste m. Human chronic myelogenous leukemia K-562 cells were efficiently tra nsduced with the N2Yc retrovirus vector and showed a significant incre ase in the 50% inhibitory concentration of chlorambucil (3.2- to 3.3-f old), mechlorethamine (4.7- to 5.3-fold), and melphalan (2.1- to 2.2-f old). In addition, primary murine clonogenic hematopoietic progenitor cells transduced with the N2Yc vector mere significantly more resistan t to alkylating agents in vitro than cells transduced with the antisen se N2revYc vector. The survival of Yc-transduced hematopoietic colonie s at 400 nM mechlorethamine and 4 mu M chlorambucil was 39.4% and 42.6 %, respectively, compared to 27.2% and 30.4% for N2revYc-transduced ce lls. Future experiments will determine the level of chemoprotection ac hievable in vivo following transplantation of N2Yc-transduced hematopo ietic cells in mice.