Figure 4.

Tumor growth and survival of rats transplanted with the four lines of cells. (A) Macroscopic overviews of rat brains bearing tumors of the four cell lines. The brains were dissected and sliced on 18 days after transplantation. Apparent tumor masses (asterisks) were observed in the brains transplanted only with C6-e and C6-L lines. (B) Cryosections of the fixed brain were fluorescently stained with Hoechst 33342 to identify the spread of tumor cells. C6-e (Bb) and C6-L (Bc) cells formed large tumor masses. Original C6 cells (ori-C6) formed an apparent but smaller tumor mass (Ba, arrowheads). There was no apparent tumor mass in the brain transplanted with C6-S cells (Bd). (C) Ratios of tumor area/total brain area were obtained by measuring the area clearly stained with Hoechst 33342, where tumor cells densely accumulated. The brains were dissected on 18 and 23 days after transplantation. Tumor areas were smaller in the C6-S-transplanted brains. Data (n=4 at each time point) are expressed as means ± SD. (D) Kaplan-Meier survival plots of rats transplanted with each C6 cell line by 40 days after transplantation. As revealed by log-rank test, rats transplanted with C6-S cells were survived significantly longer (P<0.001) than rats bearing tumors from other cell lines. (E) Mean survival days were calculated, by assuming that all surviving rats die at 41 days after transplantation. C6-S-transplanted rats survived longer by 5.5 days versus rats bearing original C6 tumors and 11 days versus C6-e and C6-L tumors. *P < .01, **P < .001.