KRT19 and cancer: To investigate whether PDAC cancer cells also exhibit higher pyruvate carboxylation activity in tumors in vivo, we first verified that the tdTomato fluorescence in tumors arising in KP-/-C mice bearing a LSL-tdTomato allele did not co-localize with staining for the fibroblast-specific marker alpha-smooth muscle actin (α-SMA) (Figure 5A), but did co-localize with Cytokeratin 19 (CK19), a marker of pancreatic cancer cells (Figure 5B).