Cell proliferation in Walker tumour growing in the stomach wall

Tumour cells from a Walker carcinosarcoma 256 were implanted in the gastric mucosa in rats. The tumour grew and infiltrated the lamina propria and the submucosal space after 7 days. It appeared to grow faster in the submucosal space than in the lamina propria. The cell proliferation was therefore studied separately in: (1) the tumour in the lamina propria, (2) the main tumour mass and (3) the tumour periphery, defined as the cells located within the outer 100-120 mum of the tumour. Mitoses arrested with vinblastine, cells labelled with tritiated thymidine and the grain count per labelled cell were studied at the three different sites. The rate of cell proliferation in the tumour was highest in the lamina propria, lower in the centre of the main tumour mass, and lowest at the periphery. Cell loss might explain the discrepancy between the rate of cell proliferation and the actual tumour growth. The factors that influence tumour cell proliferation in the different parts of the tumour are discussed.