MiR-21 deficiency fosters DEN-induced HCC development. (A) Body weight, liver weight, and liver-to-body weight ratio of 11-month-old control (CTRL—miR21fx, n = 32), hepatocyte-specific and total miR-21 knockout (LmiR21KO, n = 21, and miR21KO n = 20, respectively) mice injected with diethylnitrosamine (DEN, 25 mg/kg of body weight) intraperitoneally at day 15 post-birth. (B) Plasma levels of alanine-aminotransferase (ALAT) in CTRL (n = 27), LmiR21KO (n = 21), and miR21KO (n = 19) mice. (C) Representative pictures of explanted livers post-sacrifice and magnetic resonance imaging (MRI) prior to sacrifice of CTRL, LmiR21KO, and miR21KO mice. Tumoral masses are indicated by white arrows in the MRI scans. (D) Volume of the total tumoral mass quantified by MRI (values log10-transformed) in CTRL (n = 8), LmiR21KO (n = 8), and miR21KO (n = 8) mice. (E) Number and (F) mean diameter of isolated tumors from explanted liver in CTRL (n = 32), LmiR21KO (n = 21), and miR21KO (n = 20) mice. (G) Representative histopathological sections (hematoxylin-eosin staining, original magnification ×100) of typical HCC tumors found indiscriminately in HCC in either CTRL, LmiR21KO, or miR21KO mice. Left panel shows HCC in miR21KO with a pseudo-glandular pattern and eosinophilic cells. Right panel shows HCC in miR21KO with trabecular architectures and clear cell changes. (H) Percentage of mice in the respective cohorts developing hepatocellular carcinoma (HCC) as determined by histopathological analyses of H&E stained sections (CTRL, n = 31; LmiR21KO, n = 21, miR21KO, n = 20). Data that failed normality tests was submitted to log10-transformation prior to statistical analysis. An outliers test was performed using the ROUT method (Q = 1%). One-way ANOVA with Holm–Sidak’s correction was used for comparison between more than two groups. Chi-square test was used to evaluate the independence of categorical variables (percentage of samples with detected expression). ns, not significant, * p-value < 0.05, ** p-value < 0.01, *** p-value < 0.001, **** p-value < 0.0001.