The anticancer activity of vitamin D analogs injected after the completion of 5-FU administration in the treatment of mice bearing MC38 colon cancer. The kinetics of tumor growth (mean tumor volume). Mice bearing s.c. MC38 colon cancer cells were i.v. injected with 5-FU at a dose of 100 mg/kg/day from days 20 to 34. When 5-FU reduced tumor volume by about 90% in comparison to the control group, the administration of analogs was initiated (after administration of the cytostatic drug ended). Both analogs were administrated s.c., three times a week from days 35 to 56, PRI-2191 at a dose of 1 μg/kg/day and PRI-2205 at a dose of 10 μg/kg/day. Black arrows indicate the days of 5-FU administration, gray – days of vitamin D analog administration. Number of mice in the control group – 8 and in each treated group – 6. Statistical analysis: Kruskal-Wallis ANOVA Multiple Comparisons P values (2-tailed) test. P < 0.05 compared to control group: 5-FU from days 26 to 33, 5-FU + PRI-2191 as well as 5-FU + PRI-2205 from days 28 to 35. On day 35 the control group was sacrificed because of large size of tumors.