Targeting EGFR and HER2 in bladder cancer: receptor profiling and therapeutic potential of 213bismuth alpha-particle therapy

Bladder cancer is a major global health burden, with non-muscle-invasive bladder cancer (NMIBC) accounting for the majority of cases. Current standard-of-care therapy with BCG fails in up to 30–40% of patients, highlighting the need for alternative bladder-sparing treatments. This study characterized EGFR and HER2 expression and evaluated targeted alpha-particle therapy using [ 213 Bi] Bi-labeled trastuzumab plus cetuximab in human bladder cancer cell lines in vitro. Trastuzumab and cetuximab exhibited specific, high-affinity binding to all human bladder cancer cells; however, EGFR was more abundant per cell than HER2. Treatment with [ 213 Bi]Bi-trastuzumab+cetuximab caused dose-dependent cytotoxicity in SCaBER and RT4 cells and increased DNA-damage markers, associated with increased cell-death markers. 213 Bi treatments induced dose-dependent transcriptional changes by inducing irreparable DNA damage, disrupting DNA repair pathways, and activating multiple regulated cell death mechanisms. Immunoblot analysis showed that Chk1 and Wee1 expression and activation were comparable in [ 213 Bi]Bi-trastuzumab+cetuximab and untreated controls after 48 h of treatment with 0.3 MBq of 213 Bi. RNA sequencing demonstrated dose-dependent downregulation of G2M-checkpoint markers at 0.3 and 0.56 MBq of 213 Bi. Targeted alpha therapy using combined 213 Bi-labeled trastuzumab+cetuximab demonstrated strong preclinical efficacy in human bladder cancer cell lines, supporting its potential for further clinical development.