Ultrasound-introduced Human Triple-negative Breast Cancer Xenograft Interstitial Chemotherapy Using PLGA Microspheres Containing Docetaxel

Objective To prepare the sustained-release PLGA microspheres containing docetaxel(PMCD), observe the morphology, measure the particle size, and detect the drugloading rate, encapsulation efficiency and in vitro release, investigate the anti-tumoreffect on human breast cancer xenograft and the differential expression of multidrugresistance gene.Methods1. Preparation of PMCD: PMCD were prepared by solvent evaporation method, themorphology and particle size were observed by scanning electron microscope, thedrug loading rate, encapsulation efficiency and in vitro release were detected by highperformance liquid chromatography.2. In vivo anti-tumor effect and the mechanism: the human breast cancer-bearing nudemouse model was established by subcutaneous injection of cells suspension. Thirtymice with tumor diameter about1.2-1.5cm were randomly divided into6groups(n=5): the model group (M), blank microspheres group (B), docetaxel injection in lowdose group (DL), docetaxel injection in high dose group (DH), PMCD in low dosegroup (PMCDL), PMCD in high dose group (PMCDH), and achieved homologuetreatment. After administration, the tumor volume was measured once a week tocreate the tumor growth curve. On day35post-treatment, color Doppler flow imagingwas performed to observe the tumor morphology, parenchyma echo, boundary andblood flow information. The mice were sacrificed, and the tumors were removed tocalculate the tumor growth inhibition rate (IR) and execute histopathologicalexamination. The gene expression of multidrug resistance1(MDR1), multidrug resistance-associated protein (MRP) and breast cancer resistance protein (BCRP)were detected by real-time fluorescence quantitative polymerase chain reaction.Results1. The prepared PMCD were globe-like with smooth surface, good dispersion, and amean diameter of23.1μm.The encapsulation efficiency and drug loading rate weredetected as96.3%,4.82%, respectively. PMCD released steadily in vitro withoutobvious burst effect, and the accumulated release rate was measured as7.2%in firstday, and85.7%in40days.2. Anti-tumor effect in vivo2.1In M and B groups, the tumor volume increased obviously; in DL, DH andPMCDL groups, it increased comparatively slowly, while in PMCDH group, thetumor growth was inhibited significantly.2.2On day35post-treatment, the tumor size in PMCDH group decreasedsignificantly, with inhomogeneous echo and few blood flow signal detected by CDFI.2.3The tumor weight in group PMCDH was lower than that in group M （P <0.01）,and the tumor growth inhibition rate reached65.7%, which was the highest among allthe treatment groups.2.4Under microscope, the nuclei in group M was karyomegaly and anachromasis,with obviously pathological nuclear division. In DL, DH and PMCDL groups,partially necrotic tumor tissues were observed, whereas following the injection ofhigh-dose PMCD, a wide range of necrosis with degeneration and karyopyknosis inmost of the tumor cells occurred.2.5The gene expression of MDR1increased in DL group （P <0.05）, but decreasedin DH group（P＞0.05）, the difference was of great significance between DL groupand PMCDH group.Conclusion The PMCD prepared by solvent evaporation method has high drugloading rate, encapsulation efficiency, and steady release in vitro. Interstitialchemotherapy guided by ultrasound can significantly inhibit the growth of human breast cancer xenograft, and inhibiting gene expression of multidrug resistanceprotein may be one of the mechanisms.