Multifunctional nanoparticles based on a polymeric copper chelator for combination treatment of metastatic breast cancer

Copper plays an important role in tumor growth and metastasis. Copper chelation has been confirmed to be an effective strategy for breast cancer therapy through antiangiogenesis. In this work, a copper chelating coil-comb block copolymer RGD-PEG-b-PGA-g-(TETA-DTC-PHis) (RPTDH) was synthesized and used to prepare nano particles for loading resiquimod (R848), a TLR7 and TLR8 agonist, thus to combine antiangiogenesis and immune activation to treat breast cancer. RPTDH has strong copper-chelating ability and could self-assemble to form spherical nanoparticles with significant pH-sensitivity. R848 was efficiently loaded into RPTDH nano particles and exhibited greatly accelerated releases in weakly acid media simulating tumor microenvironment. RPTDH/R848 nanoparticles significantly inhibited the mobility, invasion and vascular tube formation of HUVECs via copper chelation, demonstrating their strong antiangiogenic activity in vitro. Furthermore, RPTDH/R848 nanoparticles remarkably induced the maturation and activation of human plasmacytoid dendritic CAL-1 cells, indicating their immune-activation ability. In breast tumor-bearing mice, RPTDH/R848 nanoparticles displayed excellent targeting ability for both primary breast tumor and lung metastases, and furthermore dramatically suppressed tumor growth and metastasis through copper deficiency-triggered antiangiogenesis and R848-induced immune activation. In summary, RPTDH/R848 nanoparticles can be used as an therapeutic agent against metastatic breast cancer through combining antiangiogenesis and immune activation.