Foreign-body tumorigenesis in mice: DNA synthesis in surface-attached cells during preneoplasia.

(CBA/H X CBA/H-T6)F1 mice were given sc implants of unplasticized vinyl chloride acetate 15 X 22-mm copolymer films. The animals were pulsed with [3H]thymidine at various times during the 15 months following implantation. DNA synthesis occurred in the film-attached cell population, predominantly macrophages, throughout the preneoplastic phase in both females and males. Giant cells with fewer than 10 nuclei were labeled synchronously and asynchronously. No DNA synthesis was detected in giant cells with more than 10 nuclei. Previous studies have shown that phagocytic inactivity and ultrastructural signs of functional dormancy are characteristic for the foreign-body-reactive macrophage. However, this investigation demonstrated that the macrophage was not dormant with respect to DNA synthesis.