Figure 6.

Suppression of malignant conversion and aneuploidy by exogenous TGF-β1. (A) TGF-β1 suppresses the frequency of calcium-resistant foci in TGF-β1−/− keratinocytes. The indicated doses of TGF-β1 were added to keratinocytes 3 days after infection with v-ras^Ha and maintained through the course of the experiment. Each histogram represents the average of five to seven dishes. *, Significantly different from untreated keratinocytes (P < 0.0001). (B) The development of aneuploidy in TGF-β1−/− v-ras^Ha keratinocytes is suppressed by treatment with TGF-β1. Histogram shows the percentage of total mitoses with specific chromosome numbers. Treatment with TGF-β1 (50 pg/ml) was begun 3 days after infection with v-ras^Ha and continued for 15 days. A total of 90 metaphases from 2 independent experiments were counted. (C) Dose response for inhibition of DNA synthesis by exogenous TGF-β1 in v-ras^Ha-transduced TGF-β1−/− keratinocytes. DNA synthesis was measured by the incorporation of [³H]thymidine (³H-TdR).