A human fibrosarcoma cell line producing multiplication stimulating activity (MSA)-related peptides

Abstract

WE suggested previously that transformed cells may produce and release cellular growth factors capable of interacting with a specific class of cellular receptors, making them unavailable as receptors for external ligands1,2. A prediction of this model was that a human fibrosarcoma line, which had been shown not to bind 125I-labelled multiplication stimulating activity (MSA)2, might be secreting molecules functionally related to MSA. We describe here some properties of growth factors produced by this human tumour cell line, derived from a 25-yr-old female with fibrosarcoma of the leg. The cells produce a family of MSA-related compounds with different molecular weights that can be separated on Sephadex G-75. The major activities correspond to proteins of approximate molecular weight (MW) of 11,000 and 7,000. Both of these fractions stimulate cell division, and will compete with 125I-labelled MSA for its receptors on mouse, rat or human cell membranes. Fibrosarcoma cells in culture may constitute an important alternate source to human serum and plasma for the isolation and characterisation of growth stimulating factors.