Generation of adhesive tumor variants: chromosomal changes, reduction in malignancy and increased expression of a distinct membrane glycoprotein.

Tumor cell variants which grow adherent to a plastic surface could be isolated in a reproducible way from the high metastatic tumor cell line ESb which grows in a suspension culture. This occurred when starting selection from the uncloned parental line as well as from a freshly derived non-adhesive subclone. The variants showed changes in their karyotype. These were quantitative (tetraploidization) and qualitative (single chromosome aberrations involving the chromosomes 12 and 17 and a marker MX-7). Phenotypic cell surface changes were documented in vitro by immunofluorescence using a monoclonal antibody (mAb 12-15) directed against a distinct plasma membrane glycoprotein of 60-69kD (gp 60-69). The expression of gp 60-69 increased with time of selection for adherence to plastic surface. The adherent cells showed in all cases a greatly reduced overall malignancy as seen by a prolonged survival time of respective tumor bearing animals compared with the suspension growing parental cells.