Quantitation of a transformation-sensitive, adhesive cell surface glycoprotein. Decrease of several untransformed permanent cell lines

We have quantitated the transformation-sensitive, cell surface LETS glycoprotein on many untransformed cell types. By SDS-polyacrylamide gel electrophoresis, this trypsin-sensitive iodinatable glycoprotein comprises 1-3% of total cellular protein of the seven early passage cell types tested. In contrast, it constitutes less than 0.15% of the protein in four of six continuous cell lines. This decrease is reflected in alterations both in [14C]glucosamine labeling and in the immunofluorescent staining of early passage vs. these four permanent cell lines. These results help to clarify previous experiments in which CSP, a purified LETS protein, partially restored a fibroblastic phenotype to cells transformed by tumor viruses. These findings also indicate that a major decrease in this cell surface glycoprotein can occur in the establishment of a continuous cell line without resulting in cellular transformation.