Fig. 1

Effect of chronic exposure to HDM in a urethane-induced LC model. A WT C57BL/6 mice were treated i.n with HDM (n = 8), HI-HDM (n = 10), or with the vehicle (VEH, n = 9) and i.p with urethane as indicated in this schematic overview of the study design. B Representative photos of 4 lung lobes (dorsal view). Scale bars, 0.25 cm. C Lung weight normalized to mouse body weight (BW). D Representative pictures of H&E-stained lung sections. One lobe per mouse is shown. Arrowheads indicate tumors. Scale bars, 1 mm. E Two selected ROIs on the H&E-stained lung section of the mouse treated with urethane and HDM shown in D. ROI#1 shows dense perivascular and peribronchial mononuclear inflammatory infiltrates (left). ROI#2 shows a papillary AD (right). Scale bars, 0.1 mm. F Representative photo of an H&E-stained lung section showing an AC of the papillary type found in one lung lobe of a mouse treated with urethane and HDM. The right panel shows the boxed region (ROI#3) at higher magnification with enlarged nuclei, prominent nucleoli, and scattered mitotic figures (indicated by arrows). Scale bars, 1 mm (left panel) and 0.1 mm (ROI#3). G IHC staining for TTF-1 of the AC shown in F. The H&E and TTF-1 staining were performed on non-serial sections of the same lung lobe. The right panel shows the boxed region (ROI#4) with strong nuclear staining for TTF-1 in tumor cells at higher magnification. Scale bars, 1 mm (left panel) and 0.2 mm (ROI#4). H Tumor multiplicity (i.e., the number of lung lesions per mouse). I Tumor area (i.e., the sum of lesion surface areas per mouse). The parameters in H and I were calculated on H&E-stained sections as shown in D. J The relative mRNA levels of several genes involved in cell proliferation were analyzed by qPCR in lung homogenates and were normalized to Krt19 gene expression. The mean expression level of each gene in the VEH group was used as a reference and was assigned the value of 1. Data are representative of one (G), two (J), or three (A–F, H, and I) independent experiments and are presented as mean ± SEM. Statistical significance was assessed by one-way (C, H, and I) or two-way (J) ANOVA with post hoc Bonferroni’s test. n.s: non-significant, * P < 0.05, ** P < 0.01, *** P < 0.001, **** P < 0.0001