Researchers have found that a subtype of muscle-invasive bladder cancer shares molecular signatures with some forms of breast cancer, opening the door for new ways of treating the disease. The findings were published in the new journal JCI Insight.

A subset of triple-negative breast cancer was already known to express low levels of a protein called claudin. The researchers in the current study showed that a subtype of bladder cancer also expresses low levels of claudin. They also found that patients’ immune systems had penetrated claudin-low tumors of either cancer type, but the cancer cells had suppressed the immune cells by blocking their checkpoint molecules. The researchers used gene signatures defined in the Cancer Genome Atlas to compare claudin-low breast cancer tumors to high-grade, muscle-invasive urothelial bladder carcinomas.

The researchers concluded that claudin-low bladder cancers may respond to immunotherapy-based treatments that activate the immune system, but future studies are needed to clinically test immune checkpoint inhibitor drugs in this bladder cancer subtype.