Stromal Fibroblasts Induce CCL20 through IL6/C/EBPβ to Support the Recruitment of Th17 Cells during Cervical Cancer Progression.

Cervical cancer is a consequence of persistent infection with human papillomaviruses (HPV). Progression to malignancy is linked to an inflammatory microenvironment comprising T-helper-17 (Th17) cells, a T-cell subset with protumorigenic properties. Neoplastic cells express only low endogenous levels of the Th17 chemoattractant CCL20, and therefore, it is unclear how Th17 cells are recruited to the cervical cancer tissue. In this study, we demonstrate that CCL20 was predominantly expressed in the stroma of cervical squamous cell carcinomas in situ. This correlated with stromal infiltration of CD4(+)/IL17(+) cells and with advancing International Federation of Gynecology and Obstetrics (FIGO) stage. Furthermore, we show that cervical cancer cells instructed primary cervical fibroblasts to produce high levels of CCL20 and to attract CD4/IL17/CCR6-positive cells, generated in vitro, in a CCL20/CCR6-dependent manner. Further mechanistic investigations identified cervical cancer cell-derived IL6 as an important mediator of paracrine CCL20 induction at the promoter, mRNA, and protein level in fibroblasts. CCL20 was upregulated through the recently described CCAAT/enhancer-binding protein β (C/EBPβ) pathway as shown with a dominant-negative version of C/EBPβ and through siRNA-mediated knockdown. In summary, our study defines a novel molecular mechanism by which cervical neoplastic cells shape their local microenvironment by instructing fibroblasts to support Th17 cell infiltration in a paracrine IL6/C/EBPβ-dependent manner. Th17 cells may in turn maintain chronic inflammation within high-grade cervical lesions to further promote cancer progression.