Natural killer cells: unlocking new treatments for bladder cancer

Immunotherapies primarily targeting the programmed death-ligand 1/programmed cell death protein 1 axis have failed to produce long-lasting improvements for patients with Bacillus Calmette-Guerin-resistant non-muscle invasive bladder cancer. Natural killer cells present an ideal target for enhancing T cell-mediated antitumor immunity. Combination immunotherapeutic strategies make up a substantial proportion of active clinical trials for non-muscle invasive bladder cancer and may hold the key to long-term outcomes. Non-muscle invasive bladder cancer, a disease with the oldest immunotherapeutic standard of care, has seen recent improvements in treatment via the application of checkpoint blocking antibodies. Unfortunately, response rates to programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) blocking antibodies remain low despite stratification by biomarkers. Sharing common biology with T cells but lacking true antigen-specificity and responding earlier to tumorigenic threats, natural killer (NK) cells present an ideal target for combination immunotherapies. NK-targeted immunotherapies under clinical investigation, including anti-NKG2A antibodies, interleukin agonists, and engineered viral vectors, hold promise in altering the immunotherapeutic landscape in bladder cancer and will be the focus of this review. Non-muscle invasive bladder cancer, a disease with the oldest immunotherapeutic standard of care, has seen recent improvements in treatment via the application of checkpoint blocking antibodies. Unfortunately, response rates to programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) blocking antibodies remain low despite stratification by biomarkers. Sharing common biology with T cells but lacking true antigen-specificity and responding earlier to tumorigenic threats, natural killer (NK) cells present an ideal target for combination immunotherapies. NK-targeted immunotherapies under clinical investigation, including anti-NKG2A antibodies, interleukin agonists, and engineered viral vectors, hold promise in altering the immunotherapeutic landscape in bladder cancer and will be the focus of this review.