In Vitro and in Vivo Mechanism of Bone Tumor Inhibition by Selenium-Doped Bone Mineral Nanoparticles

Biocompatible tissue-borne crystalline nanoparticles releasing anticancer therapeutic inorganic elements are intriguing therapeutics holding the promise for both tissue repair and cancer therapy. However, how the therapeutic inorganic elements released from the lattice of such nanoparticles induce tumor inhibition remains unclear. Here we use selenium-doped hydroxyapatite nanoparticles (Se-HANs), which could potentially fill the bone defect generated from bone tumor removal while killing residual tumor cells, as an example to study the mechanism by which selenium released from the lattice of Se-HANs induces apoptosis of bone cancer cells in vitro and inhibits the growth of bone tumors in vivo. We found that Se-HANs induced apoptosis of tumor cells by an inherent caspase-dependent apoptosis pathway synergistically orchestrated with the generation of reactive oxygen species. Such mechanism was further validated by in vivo animal evaluation in which Se-HANs tremendously induced tumor apoptosis to inhibit tumor growth while reducing systemic toxicity. Our work proposes a feasible paradigm toward the design of tissue-repairing inorganic nanoparticles that bear therapeutic ions in the lattice and can release them in vivo for inhibiting tumor formation.