Aim: To investigate the relationship between changes of peripheral blood counts and tumor rejection induced by a low dose of melphalan in C57BL/6 mice.
Methods: Mouse lymphoma EL4 cells were inoculated subcutaneously into wild type C57BL/6 mice. Twelve days later, 7.5 mg/kg melphalan were administered intraperitoneally and the same volume of Normal Saline as control. Tumor sizes were observed and recorded subsequently. Blood samples were obtained from orbital venous sinus on different days before and after melphalan treatment, and then complete blood counts were performed and the relationship between the alterations of blood counts and tumor shrinkage after melphalan treatment was analyzed.
Results: Tumor sizes decreased and tumors disappeared after 7.5 mg/kg melphalan treatment; while tumors grow continuously in control mice. The number of WBC was increased a little (10.6 + or - 2.3) x 10(9)/L 6 h after melphalan treatment, but there was no significant difference with mice before melphalan injection (9.8 + or - 0.32) x 10(9)/L (P>0.05); The number of WBC decreased significantly at 4(th) day after melphalan treatment (P<0.01); Later it increased a little, but at 28(th); day after melphalan it still obviously lower than that of the normal (P<0.01). Hemoglobin (Hb) concentration decreased from (132 + or - 7) g/L before melphalan treatment to (110 + or - 14) g/L at 6 h after melphalan treatment (P<0.05). Later, the amount of Hb was decreasing and at 7th day it got to its lowest point (96 + or - 5) g/L. It increased gradually back to normal in 2 weeks after melphalan treatment. The platelet count increased to (1502 + or - 142) x 10(9)/L 6 h after melphalan treatment, significantly higher that that (914 + or - 322) x 10(9)/L before melphalan injection (P<0.01). It maintained at a high level for one week and it recovered back to normal level at 28(th) day after melphalan treatment.
Conclusion: Tumor shrinkage after melphalan treatment was not related to the decreased number of WBC or RBC, but correlated with the increased number of platelet in 10 days after melphalan treatment.