Sequential changes of nuclear DNA content caused by chemotherapy in experimental canine gastric cancer

It is well known that the nuclear DNA content closely correlates with the histologic grade of malignancy. In this study, eight beagle dogs with gastric cancer induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) received weekly administration of 7-N-(p-hydroxyphenyl)-mitomycin C (M-83), a variant of mitomycin C. Endoscopic observations were carried out biweekly, and a biopsy specimen was taken from the same tumor site on each occasion. The nuclear DNA content of these biopsy specimens was measured by Feulgen-DNA-cytofluorometry and was sequentially observed in comparison with histologic findings. In conclusion, 1) the appearance rate of cells over 4C decreased from 25.6% to 14.7% on an average (p less than 0.02); 2) the maximum value of distribution decreased from 9.55C to 7.64C on an average (p less than 0.001); 3) the stem line reduced from 2.63C to 2.20C on an average (p less than 0.05) at the early stage of administration of the oncostatic agent prior to the appearance of histologic changes; 4) in the chemotherapy-effective group, the histogram approached a normal pattern; 5) this procedure will be useful for objective evaluation of oncostatic effects at the cytomorphologic level.