^-O-Tetradecanoylphorbol-IS-acetate-induced Changes in Sulfated Proteoglycan Synthesis in Cultured Chondroblasts1

The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) rapidly blocks the terminal differentiation of normal cul tured Chondroblasts. In TPA, the chondroblasts lose their char acteristic polygonal morphology and initiate the synthesis of an atypical type IV sulfated proteoglycan. This atypical proteoglycan has lower molecular size, shorter polysaccharide chains, and different 4S-disaccharide:6S-disaccharide ratio in com parison with type IV sulfated proteoglycan from untreated chon droblasts. When removed from TPA, the cells reacquire their characteristic polygonal morphology and reinitiate the synthe sis of their typical cartilage-characteristic type IV sulfated pro teoglycan. TPA has no readily detectable effect on the type III sulfated proteoglycan synthesized by fibroblasts.