Objective To explore the underlying mechanism of Qingzao Jiufei Decoction（清燥救肺汤

QZJFD） in the treatment of lung carcinoma. Methods Fifty C57 BL/6 J male mice were randomly divided into five groups

with 10 mice in each group. The groups included a model group

a cyclophosphamide（CTX） group

and QZJFD high

medium and low dose group. Lewis lung carcinoma cells were used to establish the mice tumor-bearing models of lung carcinoma. Twenty-four hours later

the model group was administered with 0.2 ml normal saline by gavage

twice daily; CTX group was injected intraperitoneally with 50 mg/kg cyclophosphamide

once every other day; the high

medium and low dose QZJFD group received 11

5.5 and 2.75 g/（kg·d） Qingzao Jiufei Decoction by gavage respectively

twice daily. QZFJD groups were given intragastric administration 14 days before and after the modelling

while other groups only received treatment 24 hours after the modelling for 14 days. The mRNA expression of adenosine triphosphate synthase β subunit（ATP 5 B） in lung carcinoma tissues was detected by real-time PCR; the protein expression of cytochrome c oxidase subunit Ⅳ（COX Ⅳ） was detected by western blotting; the adenosine monophosphate（AMP）

adenosine diphosphate（ADP）

and adenosine triphosphate（ATP） were detected by high performance liquid chromatography. JC-1 method was used to detect the changes of mitochondrial membrane potential（MMP）. Results The expression of ATP 5 B mRNA

COX Ⅳ protein

ATP

and MMP significantly reduced in CTX group and QZJFD high and medium dose group compared to those in model group（P<0.05 or P<0.01）. Compared to those in CTX group

the expression of ATP 5 B mRNA and COX IV protein in all QZJFD groups

ATP and MMP levels in QZJFD medium and low dose group

as well as AMP/ATP in QZJFD high dose group significantly increased

while AMP/ATP in QZJFD medium and low dose group

and ADP/ATP in QZJFD low dose group significantly decreased（P<0.05 or P<0.01）. Compared to QZJFD high dose group

both the medium and low dose group had higher expression of ATP 5 B mRNA and COX Ⅳ protein

higher ATP level

and lower levels of AMP/ATP and ADP/ATP

and the low dose group also had significantly higher MMP level（P<0.05 or P<0.01）. A statistically significant increase was seen in QZJFD low dose group when compared to the medium dose group in terms of ATP 5 B mRNA and COX Ⅳ protein expression

and the ATP level（P<0.01）. Conclusion QZJFD may inhibit the proliferation of lung carcinoma cells

by inhibiting the protein expression of COX Ⅳ

the key rate-limiting enzyme of oxidative phosphorylation energy metabolism

reducing mitochondrial membrane potential

inhibiting ATP 5 B activity

reducing ATP production

and increasing the ratio of AMP/ATP.