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Tumor is one of the intractable diseases causing human death at present.Although the prognosis of tumor patients has been improved to a certain extent through various modern treatment methods,multidrug resistance is still the main problem leading to poor tumor treatment effect.Nanomaterials are one of the research hotspots in recent years.They have many advantages,such as EPR(enhanced permeability and retention) effects,controllable modification and targeting,and have attracted more and more attention in the breakthrough of tumor drug resistance.Nano drug delivery system plays an important role in tumor therapy and can be a new way to reverse tumor drug resistance.The mechanism of multidrug resistance and the application of nanotechnology in drug resistance were reviewed.It is pointed out that further research should be carried out in the following aspects: 1) Combining with the mechanism of tumor drug resistance,reasonably control drug concentration to overcome drug resistance;2) Further explore the biosafety of nanodrug delivery system,optimize the nanodrug delivery system,avoid or reduce possible toxic and side reactions,and provide a more comprehensive theoretical basis for reversing tumor drug resistance;3) Improve the efficiency of reversing tumor drug resistance of nanodrug delivery system by combining immunology,photo dynamics,acoustic dynamics and other methods.

In order to investigate the effect on the expression of PD-1/PD-L1 and the proportion of CD3+CD4+, CD3+CD8+ T lymphocyte in spleen lymphocytes of mice treated with Chinese herbal compound, the extract of Chinese herbal compound is obtained by traditional boiling method. The mice are given intragastric administration once a day with extract of Chinese herbal compound at low, medium and high concentrations. The mice are sacrificed by neck dislocation at the end of experiment time and the spleen is freshly isolated from mice. The expression of PD-1/PD-L1 and the changes of lymphocyte subtypes are detected by Real-time PCR and flow cytometry. The results show that the expression of PD-1 on splenic lymphocytes decreases significantly and the ratio of CD3+CD4+ and CD3+CD8+ T lymphocytes increases significantly with the increase of the concentration of Chinese herbal compound, but the expression of PD-L1 does not change significantly. These results suggest that the Chinese herbal compound can be used in anti-tumor immunotherapy mediated by inhibiting the expression of PD-1 in lymphocytes, activating immune helper cells and effector cells.