Interactions between human colon carcinoma cells, fibroblasts and monocytic cells in coculture--regulation of cathepsin B expression and invasiveness.

To elucidate the importance of the tumor/host interaction in malignant tumors, we investigated the colon carcinoma cell line HT-29 in coculture with monocytic cells (THP-1) and fibroblasts (175BR) for cathepsin B expression and activity. The tumor cells were grown in monolayer cultures or as multicellular tumor spheroids. After coculture, the three cell types were separated by labeled magnetic beads for cathepsin B mRNA and protein analysis. The invasive potential was studied in in vitro invasion assays. The expression level of cathepsin B was found to be 10-fold increased in three dimensional spheroids of HT-29 compared to HT-29 monolayers. The coculture of HT-29 with THP-1 cells and/or human fibroblasts led to a considerable increase in cathepsin B mRNA expression in both tumor and tumor-associated cells. The invasive potential of the tumor cells was 5 times increased by adding monocytic cells to the assay system. This is dependent on the functional activity of cathepsin B as shown by specific siRNA's and seems to be regulated by activation of ERK1/2 and p38 signal transduction pathways.

Expression of inducible nitric oxide synthase and cyclooxygenase-2 in pancreatic adenocarcinoma: correlation with microvessel density.

AIM: Cyclooxygenases (COX) are key enzymes for conversion of arachidonic acid to prostaglandins. Nitric oxide synthase (NOS) is the enzyme responsible for formation of nitric oxide. Both have constitutive and inducible isoforms. The inducible isoforms (iNOS and COX-2) are of great interest as regulators of tumor angiogenesis, tumorigenesis and inflammatory processes. This study was to clarify their role in pancreatic adenocarcinomas. METHODS: We investigated the immunohistochemical iNOS and COX-2 expression in 40 pancreatic ductal adenocarcinomas of different grade and stage. The results were compared with microvessel density and clinicopathological data. RESULTS: Twenty-one (52.5%) of the cases showed iNOS expression, 15 (37.5%) of the cases were positive for COX-2. The immunoreaction was heterogeneously distributed within the tumors. Staining intensity was different between the tumors. No correlation between iNOS and COX-2 expression was seen. There was no relationship with microvessel density. However, iNOS positive tumors developed more often distant metastases and the more malignant tumors showed a higher COX-2 expression. There was no correlation with other clinicopathological data. CONCLUSION: Approximately half of the cases expressed iNOS and COX-2. These two enzymes do not seem to be the key step in angiogenesis or carcinogenesis of pancreatic adenocarcinomas. Due to a low prevalence of COX-2 expression, chemoprevention of pancreatic carcinomas by COX-2 inhibitors can only achieve a limited success.