In situ hybridization not only corroborated the increased expression of Cxcl1 in Stat3-deficient tumours but also identified the tumour cells as the main cellular origin of Cxcl1 as confirmed by staining for the alveolar type 2 cell-specific marker SP-C (surfactant protein C) in serial sections (Fig. 3b and Supplementary Fig. 4b). Here, STAT3 is linked to neoplasm.