Similarity in dynamics of single or double minute chromosomes incidence and number of chromosomal aberrations during long-term treatment of a human cell line with methotrexate.

The human cell line VUPT was treated with gradually increasing concentrations of methotrexate for 500 days. During this period of time the frequency of cells containing single or double minute chromosomes and the number of chromosomal aberrations were estimated. When the concentration of the drug increased, so did the frequency of cells with minute chromosomes, but after several days of adaptation to the given concentration of the drug the minute chromosomes disappeared again. The dynamics of the frequency of chromosomal aberrations resembled that of the minute chromosomes, but the change in the former cytogenetic parameter generally preceded corresponding changes in the latter. The results indicate a possible relationship between the development of chromosomal aberrations and the formation of minute chromosomes.