Breast cancers bear overexpression of neurokinin-1 (NK-1). The aim of this study was to investigate the relationship between NK-1 and EGFR in triple negative breast cancers (TNBCs). Immunohistochemistry was performed to investigate NK-1 and EGFR expressions in TNBCs. [Sar(9), \Met(O2)(11)] substance P (SMSP) was used to activate NK-1 in two TNBC cell lines, MDA-MB-231 and MDA-MB-468. L-733060 and siRNA against NK-1 were used to inhibit NK-1. The in vitro regulatory effect of NK-1 was determined using CCK-8 proliferation assay. The effects of NK-1 activation and inhibition on EGFR and its downstreaming pathway were analyzed using western blot and real-time quantitative PCR. We found that the proportion of EGFR positive cases was increased with the increasement of NK-1 levels. SMSP could promote the proliferation of TNBC cells, while L-733060 and siRNA could inhibit cell proliferation and induce apoptosis. Moreover, SMSP could enhance expressions of phosphorylation (p)-EGFR and EGFR, and activate p-Akt and p-Erk. NK1-siRNA could decrease p-EGFR, p-Akt and p-Erk. In the presence of cetuximab (0.2mg/mL), SMSP still could stimulate cell proliferation, and activate p-EGFR. However, in the presence of erlotinib (10μM), SMSP could not stimulate cell proliferation and could not activate p-EGFR. Our study showed the interaction between NK-1 and EGFR in TNBCs. These results suggested that NK-1 may regulate TNBC proliferation through EGFR phosphorylation, and the curative effect of EGFR monoclonal antibodies may be affected by NK-1 activation.
Keywords: Cetuximab; EGFR; Neurokinin-1; Substance P; Triple negative breast cancer.
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