Dansyl fluoride, a fluorescent inhibitor for the location of tumour cells in human tissues.

Dansyl fluoride (Dan-F), an active site directed fluorescent inhibitor of guanidinobenzoatase (GB), has been used for the location of tumour cells in frozen sections of human squamous cell carcinoma and colonic carcinoma tissues. The tumour cell surfaces having active GB bind Dan-F and fluoresce blue. The surrounding normal epithelial lung cell surfaces fail to bind Dan-F and hence lack fluorescence, whilst the normal colon cell surfaces have another isoenzymic form of GB, bind Dan-F and fluoresce blue. Kinetic studies have shown that Dan-F is an irreversible inhibitor of GB, and Dan-GB complexes are not dissociated with SDS and high salt concentration. However hydroxylamine (1 M) can dissociate Dan-GB complexes in the presence of 0.1% SDS, both on membrane-bound and in free solution. These studies suggest that Dan-F is a potent inhibitor of GB, and in very low concentration (3 x 10(-8) M) can be used as a novel fluorescent probe for the location of tumour cells in histological sections of human tissues.