Expression and in‐situ localization of genes coding for extracellular matrix proteins and extracellular matrix degrading proteases in pancreatic cancer

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Abstract
Pancreatic cancer shows a strong desmoplastic reaction characterized by a remarkable proliferation of interstitial connective tissue (collagens type I and III, fibronectin). In this study we have analyzed the balance of expression of mRNAs encoding extracellular matrix components (collagens I, III and IV, laminin, fibronectin), extracellular matrix‐degrading metalloproteinases (MMP‐1,‐2,‐3 and‐9) and tissue inhibitors of metalloproteinases (TIMP‐1 and‐2) in pancreatic cancer and control pancreatic tissue by Northern‐blot analysis and mRNA in situ hybridization. Transcripts for MMP‐1 (interstitial collagenase) and MMP‐3 (stromelysin‐1) were not detectable in pancreatic cancer and control tissues. Steady‐state levels of transcripts encoding extracellular matrix proteins, MMP‐2 (72‐kDa collagenase IV), MMP‐9 (92‐kDa collagenase type IV), TIMP‐1 and TIMP‐2 were elevated in the majority of pancreatic‐cancer tissue samples as compared to control pancreatic tissue. A good correlation was seen between overexpression of these MMPs and TIMPs and the steady‐state levels of transcripts coding for extracellular matrix proteins, the amount of collagen protein and the severity of the desmoplastic reaction. In situ hybridization studies localized transcripts coding for collagens type I and III to spindle‐shaped stromal cells, whereas transcripts for MMP‐2, MMP‐9, TIMP‐1 and TIMP‐2 were found in both stromal and tumor cells. However, MMP‐2 transcripts appeared to be more abundant in stromal cells, TIMP‐1 and TIMP‐2 transcripts were evenly distributed over tumor and stromal cells and relatively more MMP‐9 transcripts were found in tumor cells. We conclude that, in human pancreatic cancer, MMP‐2, MMP‐9, TIMP‐1 and TIMP‐2 may be involved in processes leading to the strong desmoplastic reaction observed in these tumors. Both stromal and tumor cells appear to be the source of MMPs and TIMPs in human pancreatic cancer.