Effect of aprotinin on immunological resistance in tumour-bearing animals.

Previous studies suggested that aprotinin might enhance the host's immunological resistance to tumours. This possibility has now been further investigated by studying the behaviour of tumours in both hamsters and mice. A second tumour graft in tumour-bearing hamsters appeared more rapidly than the first. Prior administration of aprotinin abolished this effect. Pretreatment of non-cancerous mice with cortisone nullified the effectiveness of aprotinin in inhibiting the growth of a subsequent tumour graft. These results are interpreted as additional evidence that aprotinin enhances the immunological system against tumour cells

Radioiodination studies of tumour cell-surface proteins after different disaggregation procedures.

The surface of single cells isolated from solid tumours by either a mechanical or an enzymatic method have been compared, using lactoperoxidase-catalyzed radioiodination of the tyrosine-containing proteins. Qualitatively, the patterns of surface labelling were similar, and duplicate experiments indicated that each method of isolation gave reproducible results. Analysis of incorporated label into 4 defined sections of the electrophoretic pattern illustrated quantitative differences. When the cells were isolated mechanically, the incorporation into low-mol.- wt. components was considerably reduced, whereas that into the high-mol.-wt. components was unaffected. Treatment of enzymatically isolated cells with trypsin also reduced incorporation into low-mol.-wt components

Inhibition of Malignant Cell Invasion in vitro by a Proteinase Inhibitor

The inhibitory effect of the protease inhibitor aprotinin (Trasylol) on the invasion of mouse kidney explants by polyoma virus transformed BHK21 cells was investigated using a mixed cell/organ culture technique. The extent of invasion was monitored by following the changes in LDH isoenzyme pattern in the explants and by histological assessment. The kidney explants containing aprotinin were found to maintain a normal kidney LDH pattern and to suffer considerably less invasion than the explants not containing the drug. These results support the idea that proteolytic enzymes are associated with invasion and that inhibitors of protease activity could possibly be useful in the management of clinical cancer