Autoradiographic characterization of newly developed melanoic cell group different from the melanoic tumor piece embedded into a liver lobe of mice.

Secondary proliferous melanoic tumors grew at 100% of probability in a liver lobe of C57BL/6 mouse with a piece of B16 melanoma tumor embedded successfully in the lobe. Clear border between host liver tissues and the embedded tumor piece was observed 14 days after embedding. No division image was noted in cells of the embedded tumor piece. In all regions surrounding the embedded tumor piece, there were few accumulations of leucocytes, lymphocytes, or giant cells, indicating a strong likelihood of immune reaction or antigen-antibody reaction, although there was active formation of fibroblast bunds and production of lysosomal enzymes. Secondary proliferous melanoic tumors developed in the environment of liver tissue separately from the embedded tumor location. Results of 14C-thymidine-nuclear labeling of embedded tumor cells showed that the majority of the labeled cells did not migrate or divide. In the case of 14C-thymidine-labeling of host liver tissue cells, results indicated no transfer of 14C-radioactivity into nuclei of embedded tumor cells, although there was positive distribution of 14C-radioactivity into nuclei of proliferous cells in the secondary tumor, a newly developed melanoic cell group. When prelabeling was performed the average density of autoradiographic image over the secondary tumor was equivalent to that over the normal liver tissue at the early stage such as 7 days after embedding and decreased with time after that. The newly developed melanoic cells were particularly exciting and proliferous, because they received much more labeling of 14C-thymidine as compared to liver tissue cells that was provided by one shot labeling of the radioactive tracer 1 h. before sacrifice of tumor embedded mice. There was no development of secondary melanoic cells in the liver lobe in case of embedding of a tumor piece previously by wrapping with a membranefilter, less 5 microns in pore size.