Metabolic reprogramming of stromal fibroblasts by melanoma exosome microRNA favours a pre-metastatic microenvironment

Richard B Bankert,Orla Maguire,Prashant Singh,Theresa L Whiteside,Shin La Shu,Michael J Ciesielski,Katherine A Collins,Cheryl L Allen,Peter J Bush,Yunchen Yang,Arindam Sen,Hans Minderman,Jun Qu,Xue Wang,Marc S Ernstoff,Martin Morgan,Yun Wu

doi:10.1038/s41598-018-31323-7

Abstract

Local acidification of stroma is proposed to favour pre-metastatic niche formation but the mechanism of initiation is unclear. We investigated whether Human Melanoma-derived exosomes (HMEX) could reprogram human adult dermal fibroblasts (HADF) and cause extracellular acidification. HMEX were isolated from supernatants of six melanoma cell lines (3 BRAF V600E mutant cell lines and 3 BRAF wild-type cell lines) using ultracentrifugation or Size Exclusion Chromatography (SEC). Rapid uptake of exosomes by HADF was demonstrated following 18 hours co-incubation. Exposure of HDAF to HMEX leads to an increase in aerobic glycolysis and decrease in oxidative phosphorylation (OXPHOS) in HADF, consequently increasing extracellular acidification. Using a novel immuno-biochip, exosomal miR-155 and miR-210 were detected in HMEX. These miRNAs were present in HMEX from all six melanoma cell lines and were instrumental in promoting glycolysis and inhibiting OXPHOS in tumour cells. Inhibition of miR-155 and miR-210 activity by transfection of miRNA inhibitors into HMEX reversed the exosome-induced metabolic reprogramming of HADF. The data indicate that melanoma-derived exosomes modulate stromal cell metabolism and may contribute to the creation of a pre-metastatic niche that promotes the development of metastasis.

Highlights

Local acidification of stroma is proposed to favour pre-metastatic niche formation but the mechanism of initiation is unclear
This study clearly demonstrates that Human Melanoma-derived exosomes (HMEX) and its Micro RNAs (miRNAs) are capable of reprograming the metabolism of stromal fibroblasts to increase aerobic glycolysis
The finding updates our current understanding that instigators of extracellular acidification that favours conducive microenvironment or “soil” for cancer progression may not be solely confined to the specific site of cancer, and that such a metastasis-favoring niche can be generated by normal stromal fibroblasts in distal regions that are exposed to metabolic reprogramming factors of tumour microenvironment (TME) such as cancer exosomes

Summary

Introduction

Local acidification of stroma is proposed to favour pre-metastatic niche formation but the mechanism of initiation is unclear. Exosomes released into extracellular space serve an essential role in cell-to-cell communication via the biologically-active payload that they carry, including proteins, lipids and metabolites as well as RNA and DNA species[20,21,22,23] An example of this communication is seen in melanoma exosomes that can travel to distal regions to recruit bone-marrow derived cells to promote a pre-metastatic niche and predispose the site for metastasis[5]. Exosomes derived from a BRAF (V600) mutation have been reported to harbor a different payload compared to exosomes from wild-type BRAF melanoma cells[24] Normal stromal cells such as fibroblasts play a critical role in inhibiting early-stage melanoma development[25]. Using normal HADF, we modeled the effects of the fibroblast-rich stroma to examine the contribution of HMEX in acidification of microenvironments in distal regions accessible to exosomes

Methods

Results

Conclusion