Intranuclear Irradiation Inhibits Solid Tumor Growth by Upregulating Caspase8 and Activating Apoptosis.

Radioimmunotherapy (RIT) is a novel and promising cancer treatment method, with ongoing research focusing on RIT antibody selection, radionuclides, treatment options, and benefited patient groups. As we dive into the mechanisms of tumor biology, a deeper exploration of how RIT affects tumor tissue is needed to provide new ways to improve clinical treatment outcome and patient prognosis. We labeled the anti-PD-L1 monoclonal antibody atezolizumab with iodine-131 (¹³¹I), separated and purified the labeled mAb with Sephadex G-25 medium gel filtration resin, and tested product stability. We detected the in vivo activity of ¹³¹I-PD-L1 mAb by analyzing its in vivo biodistribution and performing SPECT imaging and then set different treatment groups to study the effect of ¹³¹I-atezolizumab on the survival of tumor-bearing mice. Western blot, real-time quantitative PCR, and immunohistochemistry were used to detect the expression level of Caspase8 and Nlrp3 in tumor. TUNEL fluorescence staining was used to detect the apoptosis in the tumor. The radiopharmaceutical molecular probe ¹³¹I-atezolizumab showed high stability and in vivo biological activity. The treatment regimen adopted had a positive effect on the survival of tumor-bearing mice. ¹³¹I internal irradiation upregulated Caspase8 in tumor and ultimately inhibited solid tumor growth by activating apoptosis pathways. We also found a significant increase in the expression of NLRP3, which plays an important role in the pyroptosis pathway, in tumor. In summary, our data demonstrated that radiopharmaceuticals combined with immunotherapy affected tumor tissue by modulating relevant biological pathways, thereby achieving better antitumor effects compared with single therapy and providing new insights for promoting better patient prognosis and combination treatment strategies.