The set of growth factors stimulatory for a transformed rat cell of line NRK-49F depends on the identity of the transforming virus.

Re-cloned rat fibroblast line NRK-49F was transformed by human adenovirus type 5 which had been grown in human cells of the KB carcinoma line. Cell subclones were isolated from seven independent transformation events, and seven untransformed cell subclones were isolated in parallel from control cultures which had been inoculated with lysate of uninfected KB cells. The adenovirus-transformed cells differed from the control untransformed fibroblasts by being typically small and cuboidal, showing multilayered growth, producing colonies in soft-agar medium, and growing to higher saturation density. Adenovirus-transformed subclones showed no infective virus and no consistent difference from control subclones in karyotype (mode = 41). Like the original re-cloned NRK-49F cells, all fourteen subclones required epidermal growth factor, fibronectin, insulin, and retinoic acid for optimal growth in serum-free culture. Thus, transformation by HA5 did not alter the required set, in contrast to the earlier finding that transformation of this same re-cloned line by polyoma virus eliminated the requirements for insulin and retinoic acid.