Complement C3a promotes proliferation, migration and stemness in cutaneous squamous cell carcinoma.

Background: Complement C3 has been shown to be highly expressed in cutaneous squamous cell carcinoma (cSCC) tumour tissues and is correlated with tumour cell growth. This study aimed to investigate the mechanism of C3 in cSCC malignant transformation.

Methods: C3 expression was analysed in cSCC cell lines A431, Tca8113, SCC13, HSC-5 and HSC-1 and in immortalized HaCaT keratinocytes. Proliferation and migration of cSCC were determined after C3a exposure. Expression of cyclin D1, cyclin E, vascular endothelial growth factor (VEGF), pro-matrix metalloproteinase 1 (pro-MMP1), pro-matrix metalloproteinase 2 (pro-MMP2), stemness factors, GSK-3β, and β-catenin were analyzed. Tumour growth was examined in a murine xenograft model.

Results: C3 expression was much more highly expressed in all cSCC cell lines than in HaCaT cells. C3a treatment significantly promoted cSCC cell proliferation and migration and upregulated cyclin D1, cyclin E, VEGF, pro-MMP1 and pro-MMP2 expression, which were impeded by the C3aR antagonist. Moreover, the expression of stemness factors Sox-2, Nanog, Oct-4, c-Myc and CD-44 was stimulated by C3a and slowed by C3aR disruption. Knockdown of Sox-2 by siRNA transfection suppressed cell proliferation and migration, constrained VEGF secretion and inhibited pro-MMP1 and pro-MMP2 expression. C3a also activated the Wnt and β-catenin pathway in cSCC cells. Disruption of C3aR expression dampened tumour growth and the expression of Wnt-1, β-catenin and Sox-2 in the xenograft model.

Conclusions: C3a enhanced cell proliferation, migration and stemness in cSCC, and this activity was correlated with activation of the Wnt and β-catenin pathway.