Abstract
BACKGROUND: Overall patients with melanoma liver metastasis (MLiM) have a dismal prognosis and poor responses to the standard of care treatment. Understanding the role of the tumour microenvironment (TME) is critical for discovering better strategies to overcome intrinsic therapy resistance in MLiM. The aim was to understand the crosstalk signalling pathways between hepatocytes and metastatic melanoma cells in the TME of MLiM. METHODS: Hepatocytes and melanoma tumour cells of MLiM were assessed using transcriptomic NanoString GeoMx digital spatial profiling (NGDSP) assay. Functional assays were performed using normal hepatocytes and MLiM-derived cell lines. Validation was performed using multiplex immunofluorescence. RESULTS: In NGDSP analysis adjacent normal hepatocytes (ANH) had higher CXCR4 and COL1A1/2 levels than distant normal hepatocytes (DNH), while melanoma cells had higher TNF-α levels. In vitro, MLiM cell lines released TNF-α which upregulated CXCR4 and CXCL12 levels in ANH. CXCL12 activated CXCR4, which triggered AKT and NFκB signalling pathways. Consequently, AKT signalling induced the upregulation of collagen type I. MLiM were significantly encircled by a shield of collagen, whereas other liver metastases showed reduced levels of collagen. Of all the liver metastasis analyzed, the presence of collagen in melanoma liver metastasis was associated with a reduction in tumour-infiltrating lymphocytes. CONCLUSIONS: MLiM modified ANH to increase collagen production and created a physical barrier. The collagen barrier was associated with a reduction of immune cell infiltration which could potentially deter MLiM immune surveillance and treatment responses. HIGHLIGHTS: Spatial analyses of melanoma liver metastasis show that adjacent normal hepatocytes have increased collagen-type I levels. Melanoma liver metastases tumour cells secrete enhanced levels of TNF-α to stimulate CXCR4/CXCL12 upregulation in adjacent normal hepatocytes. Activation of CXCR4 promotes AKT and NF-κB signalling pathways to promote collagen-type I secretion in adjacent normal hepatocytes. Elevated collagen levels were associated with reduced tumour-infiltrating lymphocytes.