The role of macrophage-mediated inflammation in melanoma

Abstract

Owing to their functional plasticity, macrophages display a wide spectrum of phenotypes. As primary mediators of inflammatory responses, macrophages have emerged as key orchestrators of a chronic inflammatory state that is reported to promote tumour progression. Using in vitro cell culture systems, we find evidence of crosstalk between human macrophages and melanoma cells with melanoma cells inducing macrophages to secrete high levels of IL1β. In contrast to several previously published studies, we find that melanoma cells neither express nor respond to IL1β and propose fibroblasts as the cell type most likely to respond to the observed increase in IL1β in the melanoma microenvironment. We show that IL1β treated fibroblasts secrete IL8 and GROalpha, which we show protect melanoma cells from MAPK and PI3K inhibition by drugs in clinical use to treat melanoma. Using a CXCR2 inhibitor, to block IL8 and GROalpha binding to the receptor, negated this protective effect thereby we propose targeting both the CXCR2 and MAPK signalling pathways for the treatment of metastatic melanoma patients. Using zebrafish models encompassing different stages of melanoma progression, we have observed macrophage infiltration in tumours and an upregulation of inflammatory markers, including il1β. We have engineered a tamoxifen-inducible Cre-mediated vector system in zebrafish that allows for the over-expression of cytokines specifically in the melanoma microenvironment. Using this system, we plan to overexpress zebrafish putative il1ra together with oncogenic NRAS in order to manipulate il1 signalling in the melanoma microenvironment and to analyze the resultant effect on zebrafish melanoma progression and response to inhibitors of MAPK signalling. Together our data indicates that macrophage-mediated inflammation plays a role in melanoma growth and survival in the presence of MAPK and PI3K signalling inhibitors and thus propose that dampening this inflammation would reduce the onset of resistance observed in melanoma patients treated with these targeted therapies.

Date of Award	1 Aug 2016
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Adam Hurlstone (Supervisor)