Improved detection of labile cell-surface components with zinc chloride-aprotinin: Demonstration of glycoprotein differences in K-1735 metastatic melanoma variants

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Abstract
Metabolic labelling of K‐1735 melanoma variants with 3H‐glucosamine and cell harvesting with the commonly used protease inhibitor phenylmethylsulfonylfluoride revealed a Triton‐insoluble fibronection‐like 230 kd component in poorly metastatic cells. This component was not evident in highly metastatic cells. Significantly improved surface labelling and detection of the 230 kd glycoprotein in the highly metastatic variant was achieved by zinc chloride‐aprotinin treatment of cells prior to harvesting. This procedure also revealed an increase in a trypsin‐sensitive glycoprotein of higher molecular weight in the Triton‐insoluble fraction of the highly metastatic cell variant. Glycoprotein labelling in this fraction showed an electrophoretic pattern strongly resembling that reported by others for the high‐molecular‐weight human melanoma‐associated glycoprotein complex. The differential detection of the high‐molecular‐weight glycoprotein species in melanoma variants with differing metastatic abilities in an animal model provides a means of studying their possible relevance to metastatic melanoma. Our data also suggest that zinc chlorideaprotinin can be used to improve the detection of labile cell‐surface components.