Chromosomal effects of methotrexate on cultured human lymphocytes.

The effect of MTX on chromosome morphology was analyzed in cultured lymphocytes, and a high percentage of aberrant mitoses was found. Chromosome anomalies, such as gaps and breaks, are observed on all the chromosomes, but are preferentially located on chromosome n.3 at band p14. When the cells were continuously exposed to the drug, the chromosome damage appeared to be particularly severe.