Objective: To observe the synergistic antitumor effect and possible mechanism of extract from Periplaneta americana(EPA) and cyclophosphamide (CTX) on mice bearing-H22. Method: KM mice were inoculated subcutaneously with H22 cells to form solid tumor models and then were treated for 10 days with high dose

middle dose and low dose (50

100

200 mg·kg-1) EPA

30 mg·kg-1 CTX or received combination therapy respectively. 10 days later

the tumor weight

liver index

and spleen index were measured;and the levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in liver tissues were measured to detect the antioxidant activity of drugs;the contents of tumor necrosis factor-α (TNF-α)

interleukin 2(IL-2)

and the number of white blood cells were detected to evaluate the synergistic antitumor effect of EPA and CTX. Result: Compared with the model group

all the treatment groups could inhibit the tumor growth (P<0.05)

most significantly in combination group of 50 mg·kg-1 and CTX

with the tumor inhibitory rate up to 61.96%. EPA alone and combination of EPA and CTX could increase SOD level in liver tissues

reduce MDA level

and significantly increase serum TNF-α and IL-2 levels (P<0.05

P<0.01). The various doses of EPA could improve the spleen index and thymus index of tumor-bearing mice

but combination groups had no significant effect on the organs of tumor-bearing mice

but could enhance the amount of white blood cells in the peripheral blood. Conclusion: Combined application of EPA and CTX has significant antitumor effect in mice bearing-H22

and the mechanism may be associated with antioxidant activity and enhanced immunity.