Comparative growth of SJL/J lymphomas in irradiated and normal SJL/J mice: cell cycle distribution and tumor cell...

Flow cytometric and biological quantification of tumor cells revealed that 650 rad gamma-radiation 1 day prior to iv injection of H-2Ds negative lymphoma cells into SJL/J mice resulted in approximately a fourfold (day 3) to twelvefold (day 7) decrease in the tumor cell content of lymphoid organs as compared to that in unirradiated mice. Approximately 1.6-fold less tumor growth was noted (day 7) in 700-rad gamma-irradiated as compared to growth in unirradiated (SJL/J X CBA/J)F1 mice. Distributions of tumor cells in S-phase of the cell cycle were comparable at days 3, 5, and 7 in irradiated and unirradiated mice. Although approximately 26% of splenic tumor cells were in S-phase at days 5 and 7 in irradiated SJL/J mice, splenic tumor cell content did not increase during this time period. The data indicate that early (prior to day 3) and late (after day 5) events are responsible for decreased tumor growth in irradiated mice.