Recently, considerable attention in the field of
cancer therapy has been focused on the mammalian
rapamycin target (mTOR), inhibition of which could result in autophagic cell death (ACD). Though novel
combination chemotherapy of autophagy inducers with chemotherapeutic agents is extensively investigated, nanomedicine-based combination
therapy for ACD remains in infancy. In attempt to actively trigger ACD for synergistic
chemotherapy, here we incorporated autophagy inducer
rapamycin (RAP) into 7pep-modified
PEG-DSPE polymer micelles (7pep-M-RAP) to specifically target and efficiently priming ACD of MCF-7 human
breast cancer cells with high expression of
transferrin receptor (TfR). Cytotoxic
paclitaxel (PTX)-loaded
micelle (7pep-M-PTX) was regarded as chemotherapeutic
drug model. We discovered that with superior intracellular uptake in vitro and more
tumor accumulation of
micelles in vivo, 7pep-M-RAP exhibited excellent autophagy induction and synergistic antitumor efficacy with 7pep-M-PTX. Mechanism study further revealed that 7pep-M-RAP and 7pep-M-PTX used in combination provided enhanced efficacy through induction of both apoptosis- and mitochondria-associated autophagic cell death. Together, our findings suggested that the targeted excess autophagy may provide a rational strategy to improve therapeutic outcome of
breast cancer, and simultaneous induction of ACD and apoptosis may be a promising anticancer modality.