We observed an induction of IL-9 production by tumor infiltrating lymphocytes (TIL) and a subset of FoxP3+ regulatory T cells in the tumoral region of NSCLC patients and identified tumor infiltrating T cells, FoxP3+ Treg cells and tumor cells as IL-9R expressing target cells for IL-9 signaling. The gene discussed is IL9; the disease is non-small cell lung carcinoma.