Metastatic cancers are prone to form metastasis at a distance and acquire drug resistance, which are very common clinically and major obstacles to successful chemotherapy. Besides the tumor itself, the lymphatic system is increasingly emerging as a new target for anticancer therapy because it is an important route of tumor metastasis. To specifically deliver drug to both highly metastatic tumor and its lymphatics, tumor- and tumor lymphatics-homing peptide (LyP-1) conjugated PEG-PCL micelles (LyP-1-PM) were first constructed. Artemisinin (ART), a natural product with potential anticancer and antilymphangiogenesis effects, was chosen as the model drug and associated into the micelles. Both PM and LyP-1-PM had similar physiochemical properties, about 30 nm in size with uniform distribution. Highly metastatic breast cancer MDA-MB-435S cells and lymphatic endothelial cells (LEC) were applied as cell models. Flow cytometry and confocal microscopy studies showed that LyP-1-PM exhibited its specificity to both cell lines evidenced by its higher cellular uptake than PM. LyP-1-PM-ART demonstrated higher inhibition effect than PM-ART against these two cell lines in cell apoptosis, cell cycle and cytotoxicity tests. Near-infrared imaging showed that LyP-1-PM was distributed more in orthotopic MDA-MB-435S tumor than PM. Further study by colocalization indicated that PM accumulated near blood vessels, while LyP-1-PM further homed to tumor lymphatic vessels. LyP-1-PM achieved higher antitumor efficacy than other ART formulations in vivo with low toxicity. Both in vitro and in vivo studies here proved that LyP-1 modification enhanced the specific delivery of ART or fluorescent probe loaded polymeric micelles to MDA-MB-435S and LEC. Therefore, LyP-1-PM might be promising in terms of specific delivery of therapeutic or imaging agents to both highly metastatic breast tumor and its lymphatics.

The embryonic stem cell (ESC)-enriched miR-294/302 family and the somatic cell-enriched let-7 family stabilizes the self-renewing and differentiated cell fates, respectively. The mechanisms underlying these processes remain unknown. Here we show that among many pathways regulated by miR-294/302, the combinatorial suppression of epithelial–mesenchymal transition (EMT) and apoptotic pathways is sufficient in maintaining the self-renewal of ESCs. The silencing of ESC self-renewal by let-7 was accompanied by the upregulation of several EMT regulators and the induction of apoptosis. The ectopic activation of either EMT or apoptotic program is sufficient in silencing ESC self-renewal. However, only combined but not separate suppression of the two programs inhibited the silencing of ESC self-renewal by let-7 and several other differentiation-inducing miRNAs. These findings demonstrate that combined repression of the EMT and apoptotic pathways by miR-294/302 imposes a synergistic barrier to the silencing of ESC self-renewal, supporting a model whereby miRNAs regulate complicated cellular processes through synergistic repression of multiple targets or pathways.

No abstract