Enhancing ²²³Ra Treatment Efficacy by Anti-β1 Integrin Targeting

β1I expression, in vitro. (A) RNA expression of ITGB1 in bones and soft-tissue metastasis, Stand Up to Cancer/Prostate Cancer Foundation database. (B and C) Flow cytometry and immunofluorescence analysis of β1I expression in PC3 and C4-2B cells. Experiment was repeated twice. Bar = 50 μm; n.s. = nonsignificant.

In vivo response of PCa cells in bone to anti-β1I (4B4) and ²²³Ra treatments. (A) Experimental design and timeline of treatment schedule. (B) PC3 tumors, growth, and survival curve over time (²²³Ra, 300 kBq/kg; 4B4-mAb, 100 μg/mouse; n = 13–19 tumors). (C and D) C4-2B tumors, growth curve, and survival curve over time (²²³Ra, 300 kBq/kg; 4B4-mAb, 100 μg/mouse; n = 8–10 tumors [C]; ²²³Ra, 100 kBq/kg; 4B4-mAb, 100 μg/mouse; n = 9–12 tumors [D]). *P < 0.05. ***P < 0.001, 1-way ANOVA, followed by Tukey honestly-significant-difference post hoc test.

Cellular mechanisms of response to anti-β1I and ²²³Ra treatments. (A) Cartoon and timeline. (B) Representative overview micrograph. Insert shows zoomed subregions segmented every 100 μm from bone interface. Bar = 100 μm. (C) Quantification of mitosis/apoptosis nucleus ratio for each treatment condition. Data are mean ± SD (n = 3 bones/treatment, 3–5 slices/bone). (D) Zonal comparison of apoptotic and mitotic cells for ²²³Ra and ²²³Ra + 4B4 treatments. *P < 0.05. **P < 0.01 by 1-way ANOVA and honestly-significant-difference post hoc test. DAPI = 4′,6-diamidino-2-phenylindole.

Effects of 4B4-mAb treatment on α-radiation sensitization. (A) Cartoon of experimental pipeline. (B and C) Representative pictures of PC3 tumoroids treated with 4B4-mAb (15 μg/mL) and ²²³Ra (10 Bq/mL) alone or in combination (B); growth curve, with 3 independent experiments performed (means ± SD, 6 scaffolds/condition; C, left panel); and percentage of apoptotic cells after treatment (means ± SD, 6 scaffolds/treatment; C, right panel). Bar = 100 μm. *P < 0.05 by 1-way ANOVA and honestly-significant-difference post hoc test.