| Epidemiological statistical analysis estimates that lung cancer accounts for 26% of people dead of cancer. Annually,15% of patients who are firstly diagnosed with cancer are SCLC. Chemotherapy is the cornerstone of treatment for patients, which is always given priority to systemic chemotherapy. Owing to high sensitivity to chemotherapy, initial response rates of SCLC are high. However with the therapeutic process, secondary resistance easily occurs and patients tend to relapse after treatment cease. So most of patients survive less than two years. Therefore effective chemotherapy agents for patients with SCLC are urgently needed.With the development of nanotechnology, more nanoparticles are applied into the targeted therapy of cancer, such as liposomes, dendrimers, polymer micelle, super paramagnetic iron oxide crystals and colloidal gold. Both passive and active targeting strategies have been utilized for nanodrug delivery. Passive targeting strategy is based on the enhanced permeability and retention (EPR) effect of the vasculature surrounding tumors. These nanodrug always induced the unspecific toxicity to normal tissues which have been witnessed with the conventional anti-tumoral drugs.Meanwhile, active targeting relies on ligand-directed binding of nanoparticles to receptors expressed by tumor cells. A wide range of ligands have been used for such purposes including folic acid, peptides, proteins, antibodies, aptamers, and oligonucleotides. Numerous targeting nanodelivery systems have been developed and entered clinical trials for diverse cancers except SCLC.1.Two polypeptides (AF and AP) were screened on Small cell lung cancer cells H446 using phage display technology. Then we explored their targeted specificities adopting immunohistochemical technique.Results showed that AP and AF specifically recognized SCLC pathological tissue with low binding abilities with the normal tissues.2. A nanoparticle loaded docetaxel (DN) was formulated based on the emulsion solvent evaporation method using polylactide (PLA) as carrier for its good biocompatibility. Then AP was conjugated to the nanoparticles to prepare the targeting nanoparticles (AP-DN)with EDC condensation reaction. The mean diameters of DN and AP-DN were 195.4±3.9 and 285.9±4.4 nm respectively. The average zeta potentials of DN and AP-DN were -30.5±0.9 and -30.1±0.6 mV respectively. The morphology of AP-DNs was spherical with a smooth surface as demonstrated by TEM. The entrapment efficiency of DTX was 93.7±0.9% and the drug loading of DN was 9.3 ±0.2%.The in vitro analysis displayed that AP-DN exhibited a good release profile.3.The antitumoral efficacy of targeting nanoparticle was investigated in the subsequent experiments. In vitro cytotoxicity showed that the cytotoxicity in H446 of AP-DN was higher than that of DTX.4. Then we explored the cellular uptake of different forms of DTX. The results showed that the H446 cells uptook more targeted nanoparticles than nanoparticles and free drug, illustrating the mechanism of the high cytotoxicity of AP-DN.5. In vivo experiment showed that AP-DN, DN significantly inhibited the growth of tumor but the mortality of DN group is 80% during the treatment.6. Then the distribution of AP-DN and DN was investigated in a mouse model of SCLC. Results showed the drug concentrations in the tumor in the AP-DN group were 4-7 times higher than that in the DTX group.7. Major organs of the nude mice in each group were harvested and stained with hematoxylin and eosin (HE). AP-DN significantly inhibited liver metastases induced by H446 cells.In conclusion, the targeting nanoparticles conjugated by specifically targeted peptide were stable, and displayed better antitumoral effect both in vivo and in vitro experiment. Targeting drug increased the concentration of DTX in tumor due to its higher specific delivery. |
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