Focus on Natural Products: Microcystin LR, a cyanobacterial toxin that inhibits protein phosphatase 2A, was recently shown to stimulate tumor-associated macrophages to adopt an anti-tumor M1 phenotype. Thus, in a mouse model, Microcystin LR can effectively reverse tumor immunosuppression and activate an anti-tumor immune response, enhancing the action of chemotherapeutic drugs.
