C, Left, Quantification of cells expressing ARG1 (top), an enzyme converting arginine to urea and ornithine, and intensity of ARG1 (bottom) in normal cells from healthy (n=5, 2921 cells analyzed; blue) and residual cells from regressed (n=5, 2241 cells analyzed; green) mammary gland tissue sections. Statistical differences were calculated with the Mann-Whitney U test (Wilcoxon rank-sum test). Right, Representative images of immunofluorescence staining in normal (top) and residual (bottom) duct stained for ARG1 (green), CDH1 (red), and DAPI (blue). Scale bar: 20 μm. Data information: Numbers of replicates correspond to individual mice or humans. Box plots: midline, median; box, 25-75th percentile; whisker, minimum to maximum. Numbers marking comparisons (gray lines) show p values (corresponding statistical tests are described in individual panel legends). 