Described herein are methods for the treatment of cancer (e.g. melanoma, lung cancer, or other cancers). The methods involve administrating to a subject in need thereof an agonist of the IL-9 receptor (e.g. IL-9), e.g. an agent that binds and activates the IL-9 receptor, or an agent that increases IL-9 expression in the subject (e.g. administration of TH9 cells that express IL-9, or administration of an inhibitor of RORγ).
