Metformin reduces ECM and AT1 expression in AK4.4 pancreatic cancer model in overweight/obese mice.

After 10 weeks of high-fat diet, AK4.4 tumors were orthotopically implanted in obese FVB mice. Animals were randomly assigned to metformin in drinking water (300 mg/kg) or no treatment at day 7 until day 21 when tumors were collected. (A-i) Representative immunohistochemistry images showing the effect of metformin on tumor hyaluronan and collagen-I levels in AK4.4 tumors (n = 3–4). (A-ii) Quantification of hyaluronan expression in AK4.4 tumors. Metformin decreases the hyaluronan-positive area fraction (%). (A-iii) Quantification of collagen-I expression in AK4.4 tumors. Metformin decreases the collagen-I-positive area fraction (%). (B-i) Representative immunohistochemistry images showing the effect of metformin on expression (co-localization) of hyaluronan and collagen-I levels in activated (αSMA-positive) pancreatic stellate cells (PSCs) in AK4.4 tumors (n = 3–4). (B-ii) Quantification of hyaluronan expression in PSCs. Metformin decreases the percentage of activated PSCs expressing hyaluronan. (B-iii) Quantification of collagen-I expression in PSCs. Metformin decreases the percentage of activated PSCs expressing collagen-I. (C-i) Representative Western blots for angiotensin-II receptor-1 (AT1) expression in AK4.4 tumors. ß-actin is used as a control for protein loading. (C-ii) Densitometric analysis of AT1 expression normalized to ß-actin. Metformin decreases the expression of AT1. Data are presented as the mean ± standard error. * p < 0.05 vs. control.