Enzymatic modulation of the cell surface in malignant transformation of normal human mammary epithelial cells and in conversion of mammary carcinoma cells.

The effect of treatment with trypsin and neuraminidase on morphology, proliferation pattern, adhesiveness and ultrastructure of human normal mammary and carcinoma cell lines has been investigated. These criteria were chosen because they reflect on the cell surface function. Active enzymes were required to produce changes. If trypsinized and then allowed to grow in culture media supplemented with 'fibroblast growth-promoting factor', human normal mammary epithelial cells proliferated in a disorganized pattern with cells overlapping and piling up and developing ultrastructural characteristics of neoplastic cells. On the other hand, if treated with neuraminidase and then permitted to grow in presence of the 'fibroblast growth-promoting factor', mammary carcinoma cells proliferated in an organized pattern, forming one-cell-thick, fibroblast-like monolayers and ultrastructural characteristics of normal epithelial cells.