Abstract 4020: Hyaluronan fragments as inflammation mediators in the early stages of melanomagenesis

Abstract UV light exposure is the main risk factor for melanoma development. Skin is constantly exposed to UV light, which induces the formation of reactive oxygen species (ROS). ROS are able to degrade hyaluronan (HA), the main extracellular matrix component of the skin epidermis. HA participates in several biological and pathological processes like in inflammation and cancer. It is postulated that in skin an intact HA coat around the cells has a protective effect against UV-radiation, while HA fragments derived from HA degradation are biologically active and may have tumor promoting effects. The aim of the present work was to study the role of HA fragments in melanomagenesis. Does pericellular hyaluronan or its degradation products affect UVB tolerance, melanocyte viability, intracellular signaling and the expression of proinflammatory cytokines? In our experimental model, primary human melanocytes were pretreated with Streptomyces hyaluronidase (Strept. Hyal) for 10 min to degrade the pericellular HA coat and thereafter exposed to UVB (30 mJ/cm2). After the UVB exposure Strept. Hyal was added again to accelerate HA degradation and HA fragment accumulation. The expression levels of proinflammatory cytokines were determined using qRT-PCR. Signaling pathways activated after UVB exposure were studied by western blotting. Cell viability was examined and the influences of UVB and HA coat degradation on cell cycle and apoptosis were analyzed with FACS. In this study, we show that UVB induces the expression of the proinflammatory cytokines IL-1β and IL6 and the chemoattractant cytokines IL8 and CXCL-10. This induction was strongly elevated by the Strept. Hyal treatment suggesting that HA fragments produced by HA degradation are responsible for upregulation of these genes. The inhibition of p38 and NFkβ reversed the effect of UVB + Strept. Hyal treatment on IL6 and IL8 expression indicating that this signaling pathway is responsible for the upregulation of these genes. Moreover, silencing of hyaluronan synthase 2 (Has2) was also able to block the effect of UVB + Strept. Hyal on the studied genes suggesting that the fragmentation of endogenously produced HA generates biologically active, proinflammatory signals. Interestingly, blocking CD44, the main hyaluronan receptor, expression with siRNA was ineffective, suggesting that other upstream effectors than CD44 are involved. Regarding cell viability and apoptosis the Strept. Hyal –treatment showed only a slight difference compared to the UVB –treated melanocytes. Taken together, our results demonstrate that HA fragments strengthen the inflammatory response induced by UVB exposure. UVB + Strept. Hyal activated the p38-NFkβ signaling pathway causing the upregulation of proinflammatory cytokines. The present data suggest that HA fragments mediate sustained inflammation, which may be a trigger for tumor formation. Citation Format: Piia Takabe, Leena Rauhala, Markku Tammi, Raija Tammi, Sanna Pasonen-Seppänen. Hyaluronan fragments as inflammation mediators in the early stages of melanomagenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4020.