Evidence for cells possessing t-PA like activity in smears obtained from patients with oral squamous cell carcinoma

Squamous cell carcinoma cells possess a cell surface protease referred to as guanidinobenzoatase (GB) which is very similar to the single chain form of tissue type plasminogen activator. This enzyme binds fluorescent probes at its active center and cells possessing GB can be distinguished from those that lack this enzyme by fluorescent microscopic techniques. Normal squamous epithelial cells shed from the surface of the oral cavity lack GB and do not exhibit cell surface fluorescence when pretreated with such fluorescent probes. We have used this knowledge to design a simple technique for the rapid location of squamous cell carcinoma cells in oral smears; our results are presented in the form of colour prints in which the tumour cells can be easily distinguished from other cells by their fluorescence.