DHFR and neoplasm: Such high avidity observed in the model surface is consistent with its specific binding and uptake by FAR(+) tumor cells in vitro; Second, conjugation of MTX to the dendrimer allows retention of the ability of the attached MTX to inhibit a human DHFR enzyme as potently as free MTX; Third, this enzyme inhibition activity is translatable in vitro in cell studies, as these dendrimers were potently cytotoxic to FAR(+) KB cells.