The anti-tumor effect of soybean isoflavone (ISF) combined with vinorelbine (NVB) chemotherapy in VX2-
bearing rabbits and the corresponding mechanisms were investigated. Rabbits implanted with VX2 tumor in the lung were
divided into 4 groups including model, ISF, NVB, ISF+NVB (ISF combined with NVB) groups. The survival time of the
rabbits was recorded and the extension rate of life was calculated. The rabbits from another group were transplanted with
VX2 subcutaneously, and then the size and weight of tumor were estimated and the growth inhibition rate was calculated.
The activities of superoxide dismutase (SOD), glutathione-S-transferase (GST) and glutathione peroxidase (GSH-Px), total
antioxidant activity (T-AOC), and the content of malondialdehyde (MDA) in serum, as well as the activation of Caspase-3
and Caspase-8 in tumor tissue were detected by colorimetric method, and the DNA fragmentation of implanted tumor cells
was determined by DNA ladder method. The results showed that the administration with ISF and/or NVB prolonged the
survival time and improved the extension rate of life in VX2-bearing rabbits. ISF and/or NVB inhibited the growth of VX2
tumor transplanted subcutaneously into rabbits, and a synergistic effect was detected for the combination of ISF and NVB
in this model. In addition, NVB treatment increased serum MDA content, and reduced serum SOD activity despite of the
increased activity of serum GSH-Px, while ISF and ISF+NVB treatments increased serum GST, GSH-Px and TAOC levels,
and reduced serum MDA in VX2-bearing rabbits. Furthermore, ISF alone or ISF+NVB treatments increased the activation
of Caspase-3 and Caspase-8, and elevated DNA fragmentation of implanted VX2 tumor cells in VX2-bearing rabbits.
Therefore, ISF exhibits an inhibitory effect on the growth of transplanted VX2 tumor, and potentiates the chemotherapeutic
effect of NVB probably via improved anti-oxidative capability and the induction of apoptosis in carcinoma cells.