MAPK3 and neoplasm: We also assessed p-ERK1/2 expression in PDAC derived from our KPC mouse model (LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx-1-Cre) and found p-ERK1/2 expression in primary tumor cells, stromal cells and liver metastases (Fig. 2b).