| Multidrug resistance (MDR) is a common form of tumor cells resistant to multiplechemotherapy drug and is a major cause of cancer chemotherapy failure and tumor recurrence,become a hot research topic about cancer treatment. Nanotechnology used in clinicalpharmacy is a major breakthrough in the study of chemotherapy, and the application ofnanotechnology to overcome the resistance of tumor cells has attracted wide attention. In thispaper, based on tumor cells’ own metabolic characteristics, we prepared PEG-mCeramidemodified liposomes with the method of ethanol injection and choose ammonium sulfategradient method to entrap doxorubicin to obtain PEG-mCeramide modified doxorubicinliposomes (Lipo-ADR-Cer-). This study shows Lipo-ADR-Cer-can reduce the IC50ofdoxorubicin in the resistance tumor cells, significantly inhibited the vitro cell viablity ofresistant tumor cells MCF-7-ADR and HL-60-ADR, moreover Lipo-ADR-Cer-has a strongantitumor effect in the body.By detecting the expression of glycosylated ceramide synthase (GCS) in breast cancerand leukemia cell lines, the results indicate the expression of GCS increased in theMCF-7-ADR and HL-60-ADR cell lines than MCF-7and HL-60sensitive tumor cell lines.We consider the overexpression of GCS is associated with drug resistance in tumor cells,these results may increase the possibilities for the utilization of exogenous ceramide toovercome tumor resistance. Meanwhile, in vitro experiments, the results show that thecytotoxicity of free drug PEG-mCeramide is significantly stronger than cytotoxicity of thecontrol PEG-DSPE, the combined administration of various concentrations of freePEG-mCeramide with free doxorubicin lead sensitizing effect, sensitization factor increasedfollowing with the increasing concentration of PEG-mCeramide, and we found in the resistantcell lines, sensitizing effect of low doses of PEG-mCeramide combination with adriamycin isstronger than in the sensitive cells.In this study, we prepared PEG-mCeramide modified and non-modified control liposomeby ethanol injection, and choose ammonium sulfate gradient method to entrap doxorubicin toprepare PEG-mCeramide modified doxorubicin loading liposomes (Lipo-ADR-Cer-) andcontrol doxorubicin loading liposomes (Lipo-ADR-). The basic characterizations of nano-liposome include particle size, Zeta potential, drug loading efficiency, encapsulationefficiency, etc., and the results showed that the basic characterizations of two doxorubicinliposomes were no significant difference, and the vitro release experiments of the two doxorubicin liposomes under different conditions of PH were no significant difference. Wehave detected vitro cytotoxicity of free ADR， free ADR+PEG-mCeramide，Lipo-ADR-Cer-, and Lipo-ADR-by cck8method at different time points in MCF-7,MCF-7-ADR, HL-60and HL-60-ADR cell lines, the results demonstrated in two sensitivetumor cell lines (MCF-7and HL-60), the cytotoxicity of Lipo-ADR-Cer-and Lipo-ADR-were no statistical difference；in the two resistant tumor cell lines (MCF-7-ADR andHL-60-ADR), the cytotoxicity of Lipo-ADR-Cer-was stronger than Lipo-ADR-. To explorethe mechanism of the higher cytotoxicity of Lipo-ADR-Cer, with flow cytometry andconfocal microscopy we compared the transfection and cell endocytosis efficiency of twoliposomal, the results showed no significant difference between them. Therefore, we considerthe mechanisms of the higher cytotoxicity of Lipo-ADR-Cer-may be associated with themetabolic characteristics of drug resistant tumor cells.In vivo, we constructed animal tumor models in nude mice of breast cancer andleukemia, observed body weight changes and the tumor size in tumors-loading mice,regularly intravenously injected free PBS，Lipo-ADR-Cer-, Lipo-ADR-，free ADR and ADR+PEG-mCeramide in tumors-loading mice， then evaluated the vivo inhibitory effect ofbreast cancer tumors and the survival ratio of the leukemia animal tumor models in mice.Vivo results demonstrated that the suppression effect of PEG-mCeramide modifieddoxorubicin liposomes was stronger than the control doxorubicin liposomes, the effect ofcombination of free doxorubicin+free PEG-mCeramide is stronger than free doxorubicin，butthe two free drug treatment group are not comparable to the nano-drug group，the freedoxorubicin group and PBS group have the similar effects in the two tumors in animalmodels.Conclusion: the expression of GCS increased in resistant tumor cell lines than sensitivetumor cell lines; compared to the control doxorubicin liposomes，the basic characterization ofPEG-mCeramide modified doxorubicin liposomes in vitro releasing process, in vitrotransfection efficiency and cell endocytosis processes were not statistically different; in theresistant cell lines, compared to the control doxorubicin liposomes, PEG-mCeramidemodified doxorubicin liposomes enhanced the cytotoxicity and anti-tumor effect in in vitroand vivo. The issue based on its own characteristics of tumor cells resistant to drugs, the useof PEG-mCeramide with killing effect to prepare nano-modified liposome carrier andPEG-mCeramide modified doxorubicin liposomes, provides new evidence to overcome theresistance of tumor cells, provides a new way for the treatment of MDR. |
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