A fungal-derived adjuvant amplifies the antitumoral potency of Bacillus Calmette-Guérin via reprogramming granulopoiesis

Abstract

In patients with non-muscle invasive bladder cancer, the standard immunotherapy involves intravesical Bacillus Calmette-Guérin (BCG). However, its success requires repeated doses, and ∼50% of patients do not benefit. Using a preclinical orthotopic bladder cancer model, we found that a single intravesical dose of combined BCG and β-glucan immunotherapy eradicated aggressive tumors, resulting in 100% survival. Through single-cell transcriptomic/epigenomic analysis, flow cytometry, and intravital imaging, we show that BCG and β-glucan reprogrammed hematopoietic stem and progenitor cells with imprinting in innate immune cells, particularly neutrophils. Reprogrammed neutrophils exhibited increased reactive oxygen species (ROS) production and infiltration into the tumor core, reducing tumor vascularization and growth. The tumor microenvironment can convert neutrophils into protumor cells; BCG and β-glucan prevented this conversion, promoting sustained antitumoral activity. These findings support β-glucan as a safe, effective adjuvant to enhance BCG immunotherapy in bladder cancer and other solid tumors.

Keywords: BCG; bladder cancer; granulopoiesis; immunotherapy; innate immune memory; melanoma; neutrophils; trained immunity; β-glucan.