OBJECTIVE Triple-negative breast cancer(TNBC) is the most aggressive type of breast cancers with high mortality, high invasion and metastasis, early and frequent recurrence, poor prognosis, and lack of treatment options. Photothermal therapy(PTT) is a safe and powerful techniques used in the treatment of various cancers due to its non-invasiveness, high specificity, low side effects and strong antitumor efficacy as alternative to conventional cancer therapy. Inspired by the many advantages of liposomal hydrogel as an intelligent drug delivery system for chemo-photothermal therapy, an injectable liposomal hydrogels named as ELE-GA/NGO-Lip-gel loaded with β-elemene(ELE) and glycyrrhetinic acid modified nano graphene oxide(GA/NGO) has been prepared and characterized in author's previous study. Since 4T1 cells has high tumorigenicity and metastasis, and it is a suitable cell line for the in vivo and in vitro study of TNBC, the injectable liposome hydrogel was investigated for photothermal and synergistic targeted therapy of 4T1 breast cancer in this study. The antitumor activity, pharmacodynamics and tissue distribution of ELE-GA/NGO-Lip-gel combined with 808 nm laser irradiation were evaluated with 4T1 breast cancer cell and 4T1 bearing female BALB/c mice as the tumor models in vivo and in vitro.

METHODS  ELE-GA/NGO-Lip-gel was prepared by reverse phase evaporation method and chemical crosslinking method. The encapsulation rate, drug loading rate and the gelling property were investigated. The near-infrared laser irradiation condition was chosen to be 808 nm(2.5 W·cm⁻²) for 2 min. 4T1 breast cancer cells were taken as the model, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT), the scratch assay, and laser confocal technology were used for the antitumor activity, cell migration assay and uptake test in vitro. 4T1 bearing female BALB/c mice were taken as the model, infrared thermal imaging, in vivo fluorescence imaging, and the antitumor activity were adopted to evaluate the biodistribution and pharmacodynamics of ELE-GA/NGO-Lip-gel in vivo. The TNF-α, IFN-γ and IL-6 level in 4T1 tumor-bearing mice serum were measured by ELISA. At the end of the experiment, tumors of mice in each group were taken and treated, and HE and TUNEL staining methods were used.

RESULTS  The encapsulation rate and drug loading rate of ELE-GA/NGO-Lip were respectively (99.01±0.57)% and (13.70±0.49)%. The gelling temperature of ELE-GA/NGO-Lip-gel was suitable and the intelligent hydrogel had concentration and time-dependent photothermal conversion characteristics. Compared with ELE solution, ELE-GA/NGO-Lip-gel could significantly inhibite the proliferation of 4T1 cells(P<0.001) in a concentration- and time-dependent manner. After intratumoral injection, ELE-GA/NGO-Lip-gel had a good photothermal conversion effect in 4T1 tumor-bearing mice and a longer retention time in tumor tissues. In the pharmacodynamic test, ELE-GA/NGO-Lip-gel group showed no significant changes in body weight and relative tumor volume, and the results also showed ELE-GA/NGO-Lip-gel could induce large area apoptosis of tumor cells, and significantly reduced the levels of TNF-α, IFN-γ and IL-6 in serum of 4T1 tumor-bearing mice(P<0.001). As can be seen from the histopathology of tumor tissues, ELE-GA/NGO-Lip-gel+NIR could induce more tumor cell apoptosis, so as to realize the combined photothermal therapy in vivo.

CONCLUSION  This report focuses on the in vitro and in vivo anti-cancer effects evaluation of an injectable liposomal hydrogel co-loading of ELE and GA/NGO for breast cancer. Compared with free ELE, ELE-GA/NGO-Lip-gel has showed synergistically targeted chemo- photothermal therapy in the treatment of TNBT in vitro and in vivo irradiating at 808 nm. As a result, ELE-GA/NGO-Lip-gel combination with NIR irradiation is expected to become an alternative cancer treatment method for TNBC.