Growth factors from murine sarcoma virus-transformed cells

Area of Science:

• Cell Biology
• Molecular Biology
• Virology

Background:

• Murine sarcoma virus-transformed mouse fibroblasts secrete polypeptide growth factors.
• These factors promote cell division and anchorage-independent growth in soft agar.

Purpose of the Study:

• To characterize the growth factors produced by transformed fibroblasts.
• To determine if these factors represent a new class of growth-promoting molecules.

Main Methods:

• Cell culture of transformed and untransformed fibroblasts.
• Analysis of secreted factors using molecular weight determination, heat stability, and trypsin sensitivity assays.
• Competition assays with 125I-labeled epidermal growth factor (EGF) for membrane receptors.

Main Results:

• Three distinct molecular weight peaks (25,000, 12,000, and 7000 Da) of growth factor activity were identified.
• The sarcoma growth factors are heat-stable, trypsin-sensitive, and active at nanogram levels.
• These factors compete for EGF receptors but differ from EGF in molecular weight, antibody reactivity, and ability to induce anchorage-independent growth.

Conclusions:

• The identified sarcoma growth factors constitute a novel class of polypeptide tropic factors.
• These factors confer transformed cell properties, including anchorage independence, on fibroblasts in vitro.