The E-cadherin surface expression was further reduced after treatment of the siRNA-transfected cells with elastase (Fig. 5F). As described above, elastase had no effect on MiaPaCa-2 nor Su8686 monolayers, compatible with the fact that these cells do not express E-cadherin, or only very little (Table 1). An important question is whether or not neutrophil elastase has an impact on the functional activity of pancreatic cancer cells. To this end, the effect of elastase on the migration of pancreatic cancer cells was tested in a “wound healing” assay. Following treatment with elastase, migration of T3M4 cells was markedly enhanced (on average 22.7%) compared
with that of the untreated cells (Fig. 6A–C). In line with these data, MAPK inhibitor silencing of E-cadherin expression also enhanced the migration of the transfected T3M4 cells compared with that of mock-transfected cells (by 29.6% for siRNA1, and 31.7% for siRNA2). To assess the invasive capacity of pancreatic cancer cells, a standardized Matrigel™ invasion assay was used. T3M4 cells were incubated with 1 μg/mL neutrophil
elastase and migration was followed up for 24 h. Compared with untreated cells, about threefold more cells invaded the membrane (elastase-treated cells: 212 ± 70 invading cells/0.3 cm2 versus untreated cells: 70 ± 11 Opaganib mw respectively; mean ± SD of n = 4; the mean values differed from each other with p = 0.007, according to t-test) (Fig. 6D). In parallel, nuclear accumulation of β-catenin, a transcription cofactor regulated by E-cadherin activity and associated with for tumor cell migration and invasion, was detected by western blotting (Fig. 6E). Our data so far suggested that neutrophil-derived elastase causes a dyshesion of tumor cells by degrading E-cadherin. To assess a correlation between neutrophils and E-cadherin expression in vivo, biopsies of patients with PDAC (n = 112; Supporting Information Fig. 2) were examined with regard to neutrophil infiltrates and E-cadherin expression. Neutrophils were identified by elastase expression and by staining with naphthol-ASD-chloracetate (NASDCL). Cells were counted within the tumor and in the desmoplastic
STK38 tumor stroma as well. Of note, the distribution of the neutrophils was not homogenous throughout the biopsy. There were areas with high density (more than 100 cells per high-power field) and those with none at all (Fig. 7). Therefore, neutrophils in ten high-power fields were counted, according to the mean values, three groups were formed: 0 and 0.5 neutrophils were considered as “negative,” 0.6–10 cells as “intermediate” and more than ten cells as “severe” (Supporting Information Table 2). Staining with NASDCL or immunostaining for elastase gave essentially similar results. The majority of cases presented a PMN infiltrate (n = 108), 51 with severe (on average 60 cells) and in 57 with an intermediate (on average 6.5 cells) infiltration of PMN.