The results of the current study indicate that MMP-2 activation plays a significant role in tumor invasion and metastasis in pancreatic carcinoma.

Destruction of the basement membrane (BM) is mandatory for tumor spread, and matrix metalloproteinases (MMPs) are known to be implicated in colon cancer invasion and metastasis by digesting type IV collagen, a main component of the BM. The current study analyzed the expression of MMP-2 and MMP-9 in pancreatic cancer tissues. Frozen specimens of pancreatic cancer (n = 10), a liver metastatic nodule from pancreatic cancer (n = 1), and normal pancreas (n = 3) were homogenized and analyzed by zymography. The activated form of MMP-9 (82 kDa) was detected in all of the normal and malignant tissues, while the activated form of MMP-2 (62 kDa) was detected in all of the pancreatic cancers and its metastatic tissue, but not in the normal pancreatic tissues. These results indicate that expression of the activated form of MMP-2 may be specific to pancreatic cancer, while that of MMP-9 may be unrelated to it.

We investigated the role of neutrophils and the involvement of apoptosis in cerulein-induced acute pancreatitis. Male Sprague-Dawley rats were divided into 2 groups. In the control group, acute pancreatitis was induced by subcutaneous injections of cerulein. In methotrexate-treated group, the rats received intraperitoneal injections of methotrexate to produce neutrophil depletion before the injections of cerulein. The rats were sacrificed at the indicated time points until 72 h after the first injection of cerulein. Neutrophil depletion ameliorated pancreatic edema and vacuole formation in acinar cells during the early stages of cerulein-induced acute pancreatitis. Electron microscopy, DNA gel electrophoresis and in situ nick end-labeling revealed the involvement of apoptosis in acinar cells in cerulein-induced acute pancreatitis. Furthermore, the number of apoptotic acinar cells in neutrophil-depleted rats showed an about 2-fold increase during the late stages when compared with those in the control rats. Our results suggest that neutrophil depletion in cerulein-induced pancreatitis leads to amelioration of pancreatic injury during the early stage, and enhancement of apoptosis by neutrophil depletion occurs during the late stage.

It has been recognized in mammals that after pancreatic duct obstruction, acinar cells progressively disappear and pancreatic islets are preserved. Previous studies by electron microscopy have suggested the involvement of apoptosis in acinar cell deletion. In the present study, we employed molecular biological methods and investigated whether acinar cell deletion is due to apoptosis. In male Sprague-Dawley rats. pancreatic duct ligation was performed through a left paramedian incision. Pancreatic tissue was studied at each of the following intervals after ligation: 3, 6, 12, 18, and 24 h and 2, 3, 5, and 7 days. DNA fragmentation was determined by in situ labeling of DNA strand breaks on tissue sections [fluorescein-labeled terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling method (TUNEL)] and by electrophoretic detection of the fragments of extracted DNA. Tissue sections were also examined by hematoxylinfeosin staining and immunohistochemical staining of insulin. Pancreatic duct ligation induced acinar cell deletion by day 5. Pancreatic tissue from control rats demonstrated no TUNEL-positive nuclei. In contrast, acinar cells from rats 12 h to 5 days after duct ligation showed TUNEL-positive nuclei. The number of TUNELpositive nuclei was maximum 2 days after duct ligation. Electrophoresis showed DNA fragmentation after duct ligation. Control rats showed a genomic DNA pattern. Islets were preserved throughout the experimental period in duct-ligated rats and control rats. The results suggest that apoptosis may be the dominant form of acinar cell death in the rat pancreatic duct ligation model.

Obstruction of the pancreatic duct induces acinar cell deletion followed by duct proliferation and interstitial fibrosis. Apoptosis has been reported to be involved in the induction of acinar cell deletion after pancreatic duct ligation (PDL) in rats, however, the mechanism of pancreatic duct cell proliferation is still unknown. We hypothesized that Bcl-2 (antiapoptosis protein) and PCNA (cell cycle-related protein) could be involved in the mechanism of pancreatic duct cell proliferation after PDL. In PDL rats, acinar cells decreased in number and disappeared completely after duct ligation and duct-lining cells increased in number and formed duct-tubular complexes. Immunohistochemical study showed that PCNA expression appeared in the ductules and centroacinar cells from early stages after duct ligation and that Bcl-2 expression in duct cells, which was faint in normal pancreas, increased significantly when acinar cells were diminishing. Western blotting demonstrated that Bcl-2 was detected as a single band at 26 kDa, and the intensity of Bcl-2 in PDL rats was approximately ninefold stronger than in normal pancreas. Expression of Bcl-2 and PCNA after pancreatic duct ligation may be related to the prevention of apoptosis and cell proliferation of pancreatic duct cells in rats. Key Words: Apoptosis--1mmunochemistry-Western blot-DNA fragmentation-Chronic obstructive pancreatitis.Chronic obstructive pancreatitis is often associated with pancreatic carcinoma, pancreatic cysts, and carcinoma and benign stenosis of the ampulla of Vater. Histology reveals acinar cell deletion and prominent proliferation of duct cells with interstitial fibrosis, and the duct obstruction might play an important role in the pathogenesis. The experimental model of pancreatic duct ligation (PDL) shows the short packed figures of the chronic disease states and is quite similar to the histology in human obstructive pancreatitis. Thc PDL model has been used to investigate the morphological and physiological changes: i.e., acinar cell deletion, followed by duct proliferation and interstitial fibrosis, and pancreatic secretion, associated with duct obstruction (1-4).