Loss of tumorigenicity in a methotrexate-resistant human leukemia cell line.


We have studied the tumorigenicity of a CCRF-CEM-derived cell line (CEM/MTX-3) resistant to MTX. Eight of nine mice inoculated with drug-sensitive CEM cells developed tumors within 5 weeks, but 16 weeks after inoculation with CEM/MTX-3 cells, none of nine mice developed tumors. We were unable to detect dihydrofolate reductase gene overexpression… (More)