PDX1 and neoplasm: Since the iRFP signal could already be measured in LSL-iRFP Pdx1-Cre animals and increased signal was observed prior to a palpable tumour from KPC mice with iRFP, we were able to use iRFP fluorescence to monitor and quantify tumour development more closely than with palpation alone, and were able to obtain data documenting tumour growth (Fig. 4d).