Bladder cancer (BCa) is classified by tumor spread: non-muscle invasive (~75%), muscle-invasive (~20%), and metastatic (~5%).
Non-muscle invasive BCa is treated with transurethral resection (TURBT), often followed by a single chemotherapy dose for low-risk cases or Bacillus Calmette–Guérin (BCG) immunotherapy for higher-risk patients. BCG can cause toxicity and recurrence remains high. Muscle-invasive disease is treated with radical cystectomy and chemotherapy, but outcomes are poor, with five-year survival around 15% for metastatic cases. Immune checkpoint inhibitors (ICIs) offer new options, though response rates are limited.
Myeloid-derived suppressor cells (MDSCs) are immature immune cells that suppress anti-tumor responses and drive BCa progression. They expand in the bone marrow, migrate to tumors, and inhibit T cells via nutrient depletion, reactive oxygen species, nitric oxide, and cytokines like TGF-β and IL-10. MDSCs are detectable in tumor tissue, blood, and urine, with urine levels serving as noninvasive biomarkers. Standard therapies affect MDSCs variably—BCG, chemotherapy, and cisplatin can reduce or enhance their activity depending on context. Targeting MDSCs—through depletion, recruitment blockade, or functional inhibition—represents a promising strategy to improve BCa treatment outcomes.