Abstract
Transformation of Sprague‐Dawley rat embryo (RE) cell and a cloned Fischer rat embryo cell line (CREF) with wild‐type (Ad5) or a temperature‐sensitive DNA‐minus mutant (H5ts125) of type 5 adenovirus results in a reduction in binding of epidermal growth factor (EGF) to cell surface receptors. A reduction in EGF binding is also seen in a Syrian hamster embryo cell line transformed by a hexon mutant of Ad5. In constrast, a human embryonic kidney cell line (293) transformed by sheared Ad5 DNA or transfected clones of KB cells expressing the E1 transforming region of Ad5 do not show a decrease in receptor binding. When cocultivated, the adenovirus transformed rat cells were able to induce the growth in agar of normal CREF cells. Medium from Ad5 transformed RE cells stimulated the growth in agar of CREF cells and also inhibited [^125^I]‐EGF binding in CREF cells. When fractionated by gel filtration, two peaks of [^125^I]‐EGF inhibiting activities were obtained with apparent molecular weights of 35,000 and 16,000. These results provide the first evidence that cells transformed by an adenovirus can produce a growth factor(s) that inhibits EGF‐receptor binding and induces anchorage‐independent growth of normal cells.