Interleukin 17 in the tumor microenvironment: A potent target for anticancer immunotherapy?

Abstract

115 Background: Inflammation has been known to play a critical role in cancer for decades. Tumors build up on the “inflammatory soup” in the surrounding microenvironment to progress, grow, metastasize and evade immune response. Since its discovery in the nineties, interleukin-17 (IL-17A), a proinflammatory cytokine mainly secreted by T helper 17 cells, has been extensively studied in chronic inflammatory diseases like psoriasis or rheumatoid arthritis. In solid malignancies, there is growing evidence that IL-17 enhances cancer cells’ capacity of division, invasion and chemotherapy resistance. Methods: Based on our team's experience and publications, we systematically reviewed the existing literature about the role of IL-17 in cancers, in aim to discuss if developing IL-17 pathway-targeting strategies could be effective. Results: Data from several preclinical studies indicated tumor-promoting effects of IL-17 on diverse cancer models, cellular or murine. In clinical studies, detection of high levels of IL-17 in patients’ blood or tumors was correlated to bad prognosis. Concordantly, we reported recently in triple negative breast cancer cell lines that IL-17A and IL-17E promoted resistance to Docetaxel and failed to induce apoptosis as previously observed for IL-17E by other authors. Interestingly, we also revealed that both cytokines induced the generation of tumorigenic low molecular weight forms of cyclin E (LMW-E), which high levels correlated strongly with a poor survival in breast cancer patients. Lastly, we reported a crosstalk between IL-17E and epidermal growth factor signaling, which confers in vitro resistance to EGFR-targeted therapies. In opposition, a few studies observed that IL-17 inhibited tumor grafts development and metastasis in rodent possibly through the expression of other proinflammatory mediators such as IL-1β, TNFα, IL-6 or GM-CSF and the recruitment of neutrophils to the tumor site. Conclusions: Most of the literature supports a critical role of IL-17 in cancer promotion and development. These results encourage us to present the IL-17 family members and their receptors as potent targets for anticancer biotherapy.