Rapid regrowth or recurrent growth of occult cancer cells are often observed after esophagectomy or postoperative complications. In order to clarify the mechanism of such oncological circumstances, we focused on neutrophil elastase (NE), which degrades a broad spectrum of extracellular matrix and cell surface proteins. In the present study, we demonstrated that NE stimulated the growth of all of the five esophageal cell lines (TE-1, -7, -8, -12 and -13) by MTT assay and promoted cell invasion by cell migration assay. Pro-transforming growth factor-α (pro-TGF-α) from the cell membrane was released to the culture medium as a mature form after treatment with 5 µg/ml NE, and it reached the maximum level of 153% compared to the control values at 15 min of treatment in TE-13 cells. The phosphorylation of epidermal growth factor receptor (EGFR) rapidly occurs after treatment with NE and triggered the extracellular signal-regulated kinases 1 and 2 (ERK) signaling pathway. Moreover, NE induced release of platelet-derived growth factor-AA (PDGF-AA), PDGF-BB and vascular endothelial growth factor (VEGF) to 141.9, 227.7, and 171.6% of the control values, respectively. A specific NE inhibitor, sivelestat, significantly inhibited the NE-induced cell proliferation, cell invasion and subsequently inhibited the signal transduction pathway. Furthermore, sivelestat significantly inhibited NE-induced release of TGF-α, PDGF-AA, PDGF-BB and VEGF in the medium in TE-13 esophageal carcinoma cells. These results strongly indicate that NE released from activated neutrophils stimulates the growth and progression of esophageal cancer cells by releasing the growth factors on the cell surface and that sivelestat, a specific NE inhibitor, blocks these processes. Furthermore, we postulate that postoperative administration of sivelestat might be useful as a new molecular-targeting cancer therapy as well as for the treatment of postoperative respiratory complications.

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