Abstract
Rationale: (212)Pb, a promising in vivo alpha-particle generator of (212)Bi, has aroused much interest as a therapeutic radionuclide. For the development of targeted alpha therapy (TAT), it is important to determine the contribution of targeted effects in irradiated cells, and also of non-targeted effects in non-irradiated bystander cells. Currently, the critical roles of mitochondrial transfer in cellular crosstalk have garnered significant attention. However, the specific involvement of damaged mitochondrial transfer in orchestrating this alpha-particle radiation-induced bystander effect (RIBE) needs to be further explored. Methods: A novel alpha-emitting radiopharmaceutical, (212)Pb-hydrogel nanoparticles (HNPs), was synthesized and subsequently evaluated its theranostics effects. The impact of irradiated cell-conditioned media (ICCM), collected at different times post-(212)Bi irradiation, on bystander cancer cells regarding cell viability was also investigated. Additionally, damaged mitochondria were isolated and cultured with non-irradiated bystander cells to assess their role. Results: (212)Pb-HNPs exhibited efficient therapeutic antitumor effects in vitro, including increased GSH depletion, ROS accumulation, and mitochondrial damage in irradiated tumor cells. In vivo studies demonstrated its imaging potential through SPECT/CT, and RNA sequencing results indicated activation of oxidative stress-related pathways in irradiated tumors. Additionally, ICCM influenced the viability of non-irradiated bystander cells, suggesting a radiation-induced bystander effect by the alpha-particle (212)Bi. Interestingly, damaged mitochondria isolated from ICCM were observed to enter co-cultured non-irradiated bystander cells. Further experiments confirmed that the transfer of damaged mitochondria results in the death of non-irradiated bystander cells. Conclusion: The present study highlights the theranostic potential of the alpha-particle generator (212)Pb and, more importantly, elucidates the role of damaged mitochondrial transfer in alpha-particle RIBE. These findings provide a novel theoretical mechanism for the antitumor effects of alpha-particles and expand the clinical application prospects of TAT.