Activity measurements in human tissues of the methotrexate molecular target: a novel fluorometric assay

As DHFR is the main molecular target of MTX, a widely used anticancer drug, its level in human tissues is likely to be one of the factors determining tissue sensitivity towards this drug. Forty-one biopsies were analyzed for their DHFR activity by a convenient spectrofluorometric assay developed in our laboratory; this sensitive method proved to be suitable for measurements in very small human samples. Statistical analysis of the results showed that (i) DHFR activity is not an index of tumorogenicity, at least in the cases studied, (ii) tumorous extracts contain modulators of DHFR activity.