Studies on the mechanisms of tumorigenesis induced by polyetherurethanes in rats: leachable and biodegradable oligomers involving the diphenyl carbamate structure acted as an initiator on the transformation of Balb 3T3 cells.

The tumor-initiating activities of the methanol extracts of polyetherurethanes (PEUs) were first detected in the presence of 12-0-tetradecanyl-phorbol-13-acetate (TPA) using Balb 3T3 transformation assay. A model hard segment of PEUs, 4,4'-di(ethoxycarboamide) diphenylmethane (MDU), showed initiating activity, while chemical moieties other than the hard segment were shown to be negative in the test. The transformation assay was carried out using glass dishes half coated with two different PEUs, PU4 and PU8. In the presence of TPA, the transforming activities correlated with the tumorigenic potential in the rat implantation study on the coated surface of PEUs, but not on the uncoated glass area. From these results it was concluded that initiation was caused by the hard-segment moiety such as MDU structure derived not only from the leachable extracts but also from the biodegradable substances by the direct interaction of cells with the coated materials.