METHOTREXATE CHEMOSENSITIVITY BY ATP LUMINESCENCE IN HUMAN LEUKEMIA-CELL LINES AND IN BREAST-CANCER PRIMARY CULTURES - COMPARISON OF THE TCA-100 ASSAY WITH A CLONOGENIC-ASSAY

Chemosensitivity assays are widely used to predict the ability of tumo r cell lines to respond to potential or existing cytotoxic drugs. In t his study we have compared the cell cloning assay first described by S almon and Hamburger with a recently developed assay which measures via ble cell number by ATP luminescence. Methotrexate (MTX) was chosen as the test agent, since cell lines with varying degrees of sensitivity t o this agent were readily available. The results shown good correlatio n between the two assays, both of which are able to discriminate betwe en the various cell lines used. MTX inhibition of primary breast carci nomas and cell lines shows a steep dose-response curve with a threshol d concentration above which increasing dose does not increase sensitiv ity. In solid tumors, the plateau is usually reached at a level well b elow 100% inhibition. The ATP luminescence assay allows discrimination of MTX sensitivity between breast carcinomas and has considerable tec hnical advantages over the cloning assay.