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When a monolayer culture of normal Balb/c3T3 cells is wounded by scraping away part of the cell sheet, the cells do not migrate into the cleared area unless there is serum in the culture medium. By contrast, SV40-transformed Balb/c3T3 cells do migrate into the wound area without serum. A quantitative assay for the migration of Balb/c3T3 cells into wounds is described. This assay is used in the partial purification of a migration factor released into serum-free medium by SV28 cells. SV28 is a line of BHK21/13 hamster cells transformed by SV40 chosen for its malignancy. The most purified fractions have about 1500 times the specific activity of whole calf serum. These fractions have an activity that promotes overgrowth of Balb/c3T3 cells to high density and an activity that prolongs cell survival without serum. The SV28 migration factor is not extractable from the medium of untransformed BHK21/13 cells or from serum. This migration factor might contribute to the malignancy of SV28 cells.
Robert R. Bürk (Thu,) studied this question.