Introduction: CD44H is a transmembrane molecule important for cell-cell and cell-extracellular matrix interactions. In monocytes, CD44H is implicated in phagocytosis of particles coated by hyaluronan (HA). HA fragments were shown to induce chemokine secretion by monocytes. Tumour derived microvesicles (TMVs), which are small membrane fragments derived from tumour cells can carry fragments of HA. The aim of the study was to examine whether monocyte's CD44H is involved in the engulfment of pancreatic adenocarcinoma-derived microvesicles and in the production of chemokines induced by TMVs.
Materials and methods: TMVs engulfment and chemokines' secretion stimulated with TMVs were determined in control human monocytes and cells incubated with anti-CD44H monoclonal antibody (mAb) by flow cytometry and ELISA, respectively. Phosphorylation of STAT3, transcription factor essential for chemokines' production and CD44 signal transduction, was determined by Western blotting.
Results: Blocking of CD44H by anti-CD44H mAb on monocytes decreased the engulfment of TMVs and the secretion of CCL4 and CCL5, but had no effect on CCL2, CCL3 and CXCL8. STAT-3 phosphorylation in monocytes incubated with TMVs after CD44 blocking was also reduced.
Conclusion: The results suggest that tumour-derived microvesicles (TMVs) may carry bioactive cargo(s) which induces STAT3 dependent signalling pathway in human monocytes via CD44 molecules.
Keywords: CD44; HPC-4 cells; STAT3 phosphorylation; chemokines; flow cytometry; human monocytes; tumour-derived microvesicles.