Two breast cancer cell lines (MCF7 and MDA-MB-231) showed an increase in ARG level when treated with the combination of ARG and insulin, however the remaining seven cell lines showed either a marginal effect, or a decrease in ARG level when compared to ARG treatment alone (Fig. 1D–I; see Supplementary Fig. S1D–L for quantitation, and Supplementary Fig. S5–S13 for unprocessed images). Here, INS is linked to breast carcinoma.