Fig 2: Protein expression of target genes CYP1A1 and NF-?B in rat lung tissues detected by western blotting. In the control group, the lung tissue of the rats revealed low expression of CYP1A1. After 4 weeks of CS, the expression of CYP1A1 protein in rat lung tissues increased. From week 8 to week 16, there was significant overexpression of CYP1A1 protein in the rat lungs exposed to CS. EGCG treatment significantly downregulated the overexpression of CYP1A1 protein in rat lung tissues induced by CS. NF-?B was weakly expressed in the lung tissue of control rats. Between weeks 4 and 12, CS increased the protein expression of NF-?B in rat lung tissue, while EGCG administration downregulated this expression. However, NF-?B overexpression then decreased until the experimental endpoint in both treatment groups. *P<0.05, **P<0.01, ***P<0.001 and ****P<0.0001. NF-?B, nuclear factor-?B; EGCG, epigallocatechin-3-gallate; CS, cigarette smoke.

Fig 3: Expression of TGF-ß, CYP1A1 and NF-?B in non-small cell lung carcinoma tissues. The samples were detected by immunohistochemistry and stained by DAB at a magnification of ×100. The expression of TGF-ß and CYP1A1 in non-small cell lung carcinoma and lung atypical hyperplasia tissues was significantly higher than in para-carcinoma and chronic inflammatory tissues. Conversely, the expression of NF-?B in non-small cell carcinoma and in lung atypical hyperplasia tissues was significantly lower than in para-carcinoma and chronic inflammatory tissues. (A) In non-small cell lung carcinoma tissue, TGF-ß and CYP1A1 proteins were highly expressed, with NF-?B expressed at a low level. (B) In lung atypical hyperplasia tissue, TGF-ßand CYP1A1 proteins were strongly expressed but NF-?B was weakly expressed. (C) In para-lung carcinoma tissues, TGF-ß and CYP1A1 proteins were expressed at low levels, with NF-?B protein expressed at a high level. (D) In chronic inflammatory lung tissue, TGF-ß and CYP1A1 proteins were weakly expressed, while NF-?B was strongly expressed. #P>0.05, *P<0.05, **P<0.01 and ***P<0.001. TGF, transforming growth factor; NF-?B, nuclear factor-?B.

Fig 4: Expression of skin stem cell progenitor markers and AHR biomarkers in skin. Time-mated mice were treated by gavage with either corn-oil or TCDD (5 µg/kg bw) and pups were analyzed for specific localization of response to TCDD. Corn-oil- or TCDD-exposed skin samples at P21 were labeled with antibodies as indicated. DAPI (blue) was used to stain nuclei. (A) CYP1A1, CYP1B1, and LRIG1 expression in corn-oil- (a–d) and TCDD- (e–k) treated skin samples, as indicated. (B) CYP1B1 and LGR6 expression in corn-oil- (a–d) and TCDD- (e–h) treated skin, as indicated. Boxed areas in (a,e) are shown at higher magnification in (d,h), respectively. Scalebar = 25 µm. Abbreviations: AHR, aryl hydrocarbon receptor; TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxin; bw, body weight; P, postnatal day; DAPI, 4',6-diamidino-2-phenylindole; CYP1A1, cytochrome P4501A1; CYP1B1, cytochrome P4501B1; LRIG1, Leucine-rich repeats and immunoglobulin-like domains protein 1; LGR6, Leucine-Rich Repeat Containing G Protein-Coupled Receptor 6.

Fig 5: Biomarkers of response to TCDD. Time-mated mice were treated by gavage with either corn-oil or TCDD (5 µg/kg bw) and pups were analyzed for biomarkers of AHR activation. (A) Murine skin Cyp1a1, Cyp1b1, Artn mRNA expression measured by qPCR at the indicated age (n = 4–6). Data were analyzed by two-tailed Student’s t-test. * p < 0.05, compared to age-matched corn-oil control. (B) Representative images of immunohistochemical staining of CYP1A1 and CYP1B1 at P21 following the indicated treatment. Scale bar = 20 µm. Arrows point towards E, IF, IS, and SG. (C) CYP1A1 and CYP1B1 immunostaining intensity scores for corn-oil- and TCDD-treated samples. Staining intensity at different areas of localization was scored manually on a scale of 0 to 3 (CYP1A1) or 0 to 4 (CYP1B1), 0 being absence of staining and 3 or 4 being highest intensity of staining for CYP1A1 or CYP1B1, respectively. Each symbol represents an individual skin sample (n = 4–7). Graphs display mean values. Images in boxes are representative immunostaining of TCDD-treated sample at P6 (E, SG) and P21 (IF, IS) as per localization of maximum intensity. Scale bar = 20 µm. Data were analyzed by the Mann–Whitney U test. * p < 0.05, compared to age-matched corn-oil control. Abbreviations: TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxin; bw, body weight; AHR, aryl hydrocarbon receptor; CYP1A1, cytochrome P4501A1; CYP1B1, cytochrome P4501B1; ARTN, artemin; qPCR, quantitative PCR; P, postnatal day; E, epidermis; IF, infundibulum; IS, isthmus; SG, sebaceous gland.