Figure 1. Collagen types I and IV and their associated collagenases are abundant in the stromal compartment of PDAC.

(a) Collagen by Masson’s trichrome staining and (b) immunohistochemistry (IHC) of collagen proteins type I and IV in human and mouse tumour sections. Representative images and their relative insets from n=4 patients and n=3 Pdx1-Cre;KrasG12D;Ink4a−/− (PKI) mice are illustrated. The percentage of total collagen and collagen types I and IV staining intensity calculated relative to total tumour area, expressed as mean±s.e.m., is indicated. Scale bar, 100 μm. (c) mRNA levels of the collagen specific MMP 13, 9 and 2 and prolidase (Pepd gene) measured by quantitative RT–PCR in PDAC from PKI mice (n=3) versus control pancreases from KrasG12D;Ink4a−/− (KI) mice (n=3). Data are mean±s.e.m. *P<0.05, **P<0.01, ***P<0.001; two-tailed unpaired Student’s t-test. (d) Prolidase localization in human and PKI mice tumours revealed by IHC (left) or immunofluorescence (IF, right), respectively. Representative images from n=4 patients and from n= 3 PKI mice. Scale bar, 100 μm. (e) Prolidase levels in supernatant from PK4A cells cultured during 24 or 48 h with coated collagen I in complete media. Total loaded protein was determined by Ponceau red staining (Std: standard). Marker sizes are indicated in kDa. Photos are representative of n=3 independent experiments. Uncropped images of blots are shown in Supplementary Fig. 10. MMP, matrix metalloproteases; RT–PCR, PCR with reverse transcription.