Radix Tetrastigma Extracts Enhance the Chemosensitivity in Triple-Negative Breast Cancer Via Inhibiting PI3K/Akt/mTOR-Mediated Autophagy.

OBJECTIVE: Drug resistance in tumors is one of the major factors that leads to chemotherapy failure. This study aims to investigate the effect of Radix Tetrastigma extracts (RTEs) on Taxol-induced autophagy and the chemosensitivity against drug resistance in triple-negative breast cancer (TNBC). METHODS: Taxol-resistant MDA-MB-468 (MDA-MB-468/Taxol) cells were induced and treated with RTEs and/or Taxol. Mice were subcutaneously inoculated with MDA-MB- 468/Taxol cells to establish xenograft models. The associated protein levels were measured by western blotting. Flow cytometry, CCK-8 and EdU assay were performed to detect cell apoptosis, viability, and proliferation, respectively. RESULTS: In MDA-MB-468/Taxol cells, RTEs & Taxol treatment increased cell apoptosis, reduced cell viability and proliferation, up-regulated anti-autophagy marker LC3I/LC3II ratio, and enhanced mTOR level. With RTEs & Taxol treatment, mTOR silencing downregulated LC3I/LC3II ratio, increased cell viability and proliferation, and reduced cell apoptosis, while mTOR overexpression showed the opposite results. PI3K inhibitor reduced AKT and mTOR levels, and the effects on cell activities were similar to the results of mTOR silencing. After RTEs & Taxol injection, xenograft tumor was smaller, and AKT, mTOR, LC3I/LC3II ratio and apoptotic marker cleaved caspase-3 were increased. CONCLUSION: RTEs enhanced the chemosensitivity of resistant TNBC cells to Taxol through inhibiting PI3K/Akt/mTOR-mediated autophagy. MICRO: RTEs exerted anti-tumor effects in various cancers, and this study determined its role in TNBC. Taxol-resistant MDA-MB-468 cells were induced and xenograft models were established. We found that RTEs inhibited autophagy of MDA-MB-468/Taxol cells and reduced tumor growth. Inhibition of PI3K/Akt/mTOR pathway promoted autophagy of MDA-MB-468/Taxol cells. We may provide a new potential strategy for TNBC treatment.

Co-delivery of doxorubicin and pH-sensitive curcumin prodrug by transferrin-targeted nanoparticles for breast cancer treatment.

The natural product curcumin and the chemotherapeutic agent doxorubicin have been used in the treatment of many cancers, including breast cancer. However, fast clearance and unspecific distribution in the body after intravenous injection are still challenges to be overcome by an ideal nano-sized drug delivery system in cancer treatment. In this study we design transferrin (Tf) decorated nanoparticles (NPs) to co-deliver CUR and DOX for breast cancer treatment. A pH-sensitive prodrug, transferrin-poly(ethylene glycol)-curcumin (Tf-PEG-CUR), was synthesized and used for the self­assembling of NPs (Tf-PEG-CUR NPs). DOX is incorporated into the Tf-PEG-CUR NPs to obtain Tf-PEG-CUR/DOX NPs. In vitro cytotoxicity studies and in vivo antitumor activity were carried out using MCF-7 cells and mice bearing MCF-7 cells, respectively. Tf-PEG-CUR/DOX NPs has a particle size of 89 nm and a zeta potential of -15.6 mV. This system displayed remarkably higher efficiency than other systems both in vitro and in vivo. DOX and CUR were successfully loaded into nanocarriers. The in vitro cell viability assays revealed the combination of Tf-PEG-CUR and DOX NPs exhibited higher cytotoxicity in vitro in MCF-7 cells compared with Tf-PEG-CUR NPs alone. Using the breast cancer xenograft mouse model, we demonstrate that this co-encapsulation approach resulted in an efficient tumor-targeted drug delivery, decreased cytotoxic effects and exhibited stronger antitumor effect.