Methotrexate-resistance is associated with double minute chromosomes in lymphocytes from patients with prostate cancer

Abstract

Human lymphocytes have long been used to assess the gene damage occurring in vivo as well as in vitro . In this study , peripheral blood lymphocytes from patients with prostate cancer were cultivated in vitro short-term culture in the presence of methotrexate (MTX) to investigate the possible mechanism of resistance to MTX in those cells. The results indicate that the resistance to MTX in lymphocytes from prostate cancer patients is associated with dihydrofolate reductase (DHFR) gene amplification . Metaphase chromosome preparations from those cells were examined and were shown to contain double minute chromosomes (DMs). We conclude, that the presence of DMs may support that the resistance to MTX in prostate cancer patients may be associated with DHFR gene amplification.