Deficient production of lysyl oxidase in cultures of malignantly transformed human cells.

Lysyl oxidase activity in the culture medium of eight malignantly transformed human cell lines was very low compared with that in four control fibroblast lines, being 9-16% in five sarcoma cell lines and 7-11% in three other tumour cell lines. The low enzyme activity was probably due to deficient enzyme synthesis rather than impaired secretion into the cell medium, as low activity was also found in urea extracts of the cell pellets. Lysyl oxidase production thus appears to be closely regulated with deficient collagen gene expression in malignant transformation.