Cytotoxicity in human cell cultures as a primary screen for the detection of anti-tumor agents.

It has been shown in a preceding paper (5) that thirteen agents known to have an anti-tumor effect in animals or man were highly cytotoxic against a number of cultured human and animal cells, inhibiting growth at concentrations of 10~5 to 10~9 M. Conversely, two folie acid analogs which were essentially devoid of anti-tumor action in vivo were relatively inactive in cell cultures. These findings suggested that the "anti-tumor"