Research On The Paclitaxel/Lapatinib-loaded PEG-PLA Micelles For The Treatment Of HER2 Positive Breast Cancers

Up to 30% of invasive breast cancers overexpress human epidermal growth factor receptor-2(HER2),HER2 positive breast cancer are associated with a more aggressive phenotype and shorter recurrence-free survival as well as OS.Lapatinib is approved for patients with HER2 positive metastatic breast cancer that has progressed with trastuzumab.In spite of several advantages as an agent against HER2 positive breast cancer, lapatinib has a poor solubility in water, which makes it difficult to prepare intravenous injection.Taking orally requires large dose and high frequency of lapatinib, leading to nonadherence of patients. Paclitaxel is widely used for chemotherapy against breast cancer. Similar with lapatinib, The solubility of paclitaxel in water is less than 0.4μg/mL. Cremophor EL and ethanol (1:1, v/v) are used as solvent to increase the solubility of paclitaxel. However, Cremophor EL may trigger fatal allergic reactions, which limites the application of paclitaxel to a certain degree.Nano drug-delivery system creats a new approach for tumor. Polymeric micelles not only have a potential as delivery system for poorly soluble drugs, also prolong time of blood cycle. In addition the nanosize of polymeric micelles allows for passive drug targeting at tumor tissues.In order to increase the solubility of the paclitaxel, paclitaxel and lapatinib copolymer micelles were prepared utilizing polyethylene glycol-poly lactic acid (PEG-PLA). It could improve the treatment effect of HER2 positive breast cancer with the possibility of achieving synergistic effect through the simultaneous delivery of paclitaxel and lapatinib.In Chapter I, LPT-PEG-PLA was synthesized by acylation reaction,then L-PPM-PTX were prepared by thin film hydration method.The particle size and PDI of L-PPM-PTX were 25.80±0.47nm and 0.202±0.019 respectively, Drug loading capacity (DLC) and entrapment efficiency (EE)for paclitaxel were14.82±2.16% and 84.21±9.83% respectively. L-PPM-PTX could escape from endosomes and be distributed into cytoplasm.Flow cytometry shows the cytotoxicity of L-PPM-PTX against SKBr-3 cells(HER2 positive) was found to significantly increase compared to PPM-PTX and L-PPM, L-PPM-PTX could lead to cell arrest in G2/M and G1/S phases simultaneously. Results of nucleus staining confirmed the result of flow cytometry.In Chapter II, PPM-PL were prepared by dialysis method. Particle size, drug loading of both paclitaxel and lapatinib were as the indexes on the basis of the primary single factor test. Prescription and preparation process of PPM-PL was optimized by applying the central composite design-response surface method. The optimal prescription:PEG-PLA was 50 mg, PTX and LPT were both 7.3 mg, and dialysis time was 19.4 h. Under optimal prescription prepared PPM-PL whose size and PDI were 20.05±0.09 nm and 0.193±0.01 respectively, DCL and EE of lapatinib were 6.02±0.29%、43.88±2.21%,DCL and EE of paclitaxel were 9.93±1.17%, 75.60±9.85%.Tumor xenografts were established by inoculation of SKBr-3 cells into nude mice. Then the distribution of free DiR and the DiR-loaded micelles in tumor-bearing nude mice were investigated by using vivo imaging technology.The result showed the fluorescence in tumor of the DiR-loaded micelles was stronger than that of free DiR which suggested that the DiR-loaded micelles could accumulate in tumor through the passive targeting effect, indicating drug-loaded micelles may have better effect than free drug. The tumor-bearing mice were treated with PPM-PL and other drugs to determine the antitumor activity. The result shows the antitumor effect of PPM-PL was the best than other experimental drugs.In summary, PM-PL were prepared to increase the solubility of paclitaxel and lapatinib. Meanwhile, drugs were accumulated in tumor tissues by passive targeting effect and released slowly. In addition, synergistic effect was achieved through the simultaneous delivery of both drugs,which could improve the therapeutic on the HER2 positive breast cancer.