A regulatory B cell subpopulation expressing CD301b lectin promotes breast cancer growth

Tumor-associated carbohydrate antigens (TACAs) can promote tumor growth by regulating the anti-tumor immune response. The accumulation of immune suppressor cells within the tumor in response to TACAs suggests a critical pathway to suppress immune targeting of the tumor. Employing murine breast cancer models, we isolated a regulatory B cell subpopulation in the breast tumor microenvironment that displays an immune suppressive phenotype through its Tn TACA-binding lectin, CD301b. We then demonstrated that depleting CD301b ⁺ cells facilitated tumor control and mouse survival, whereas increasing Tn antigen expression decreased mouse survival. As tumor cells use Tn expression to overcome immune targeting, interfering with or blocking the Tn-CD301 axis may unleash the immune system, specifically within the aberrantly glycosylated tumor microenvironment, offering new immunotherapy for breast and other cancers.