Preclinical Evaluation of 223RaCL2 and Immune Checkpoint Inhibitors in Prostate Cancer Bone Mets

Tumor progression in mice (n = 10/group) was monitored using in vivo bioluminescence imaging following administration of 223RaCl2 at doses of 0.27 µCi, 0.18 µCi, or 0.04 µCi. The 0.27 µCi dose was also used in a cohort receiving combinational therapy with immune checkpoint inhibitors (ICIs). Imaging was performed prior to treatment (Day 0) and weekly thereafter. Mice were anesthetized with 2% isoflurane in oxygen, and D-luciferin potassium salt (120 mg/kg; MediLumine, Montreal, QC, Canada) was administered via intraperitoneal injection 7 min prior to image acquisition. Bioluminescence imaging was conducted using the Spectral Instruments Imaging Lago X system (Scott Ireland, ON, Canada). Up to five mice were positioned prone on the imaging bed, separated by physical dividers to prevent signal overlap. Bioluminescence signals were quantified using Aura software v4.5 (Spectral Instruments Imaging; Tucson, AZ, USA), and tumor burden was assessed by normalizing total flux (photons/sec) to each mouse’s Day 0 value.