Lymphatic endothelium stimulates melanoma metastasis and invasion via MMP14-dependent Notch3 and β1-integrin activation.

Pirita Pekkonen,Sanni Alve,Krista Tuohinto,Sampsa Hautaniemi,Ilkka Paatero,Kaisa Lehti,Silvia Gramolelli,Giuseppe Balistreri,Otso Niiranen,Katherine Icay,Nina Perälä,Nadezhda Zinovkina,Johanna Ivaska,Pipsa Saharinen,Adewale Taiwo,Päivi M Ojala,Olga Tatti-Bugaeva,Pauliina Repo

doi:10.7554/elife.32490

Abstract

Lymphatic invasion and lymph node metastasis correlate with poor clinical outcome in melanoma. However, the mechanisms of lymphatic dissemination in distant metastasis remain incompletely understood. We show here that exposure of expansively growing human WM852 melanoma cells, but not singly invasive Bowes cells, to lymphatic endothelial cells (LEC) in 3D co-culture facilitates melanoma distant organ metastasis in mice. To dissect the underlying molecular mechanisms, we established LEC co-cultures with different melanoma cells originating from primary tumors or metastases. Notably, the expansively growing metastatic melanoma cells adopted an invasively sprouting phenotype in 3D matrix that was dependent on MMP14, Notch3 and β1-integrin. Unexpectedly, MMP14 was necessary for LEC-induced Notch3 induction and coincident β1-integrin activation. Moreover, MMP14 and Notch3 were required for LEC-mediated metastasis of zebrafish xenografts. This study uncovers a unique mechanism whereby LEC contact promotes melanoma metastasis by inducing a reversible switch from 3D growth to invasively sprouting cell phenotype.

Highlights

Distant organ metastasis requires that the tumor cells gain access into the hematogenous circulation (Lambert et al, 2017)
Melanoma cells have been shown to be in close contact with the lymphatic vessels in human specimens and often metastasize via the lymphatic system, (Niakosari et al, 2008), implying that the melanoma cell-lymphatic endothelial cells (LEC) interactions are common events in human melanomas
In the xenograft mouse model, dissemination of the metastatic WM852 cell line to distant organs was increased by LEC priming

Summary

Introduction

Distant organ metastasis requires that the tumor cells gain access into the hematogenous circulation (Lambert et al, 2017). Alve et al conducted a series of experiments to identify specific proteins in the melanoma cellsthat were responsible for making the cancer more invasive after it interacted with the lymph vessel cells These experiments identified proteins called MMP14, Notch, and b1-integrin as critical to the invasive spread of melanoma cells. Clinical observations of satellite melanoma tumors growing between the primary tumor and draining lymph nodes have suggested that the surrounding lymphatic endothelium serves as a protective microenvironment for the survival of incipient metastatic cells (Meier et al, 2002) In support of this hypothesis, over the last few years it has become increasingly clear that lymphatic endothelial cells (LECs) actively interact with the surrounding cells in the tissue, regulating both physiological and pathological processes including tumor progression and metastasis. The crosstalk with LECs promotes melanoma metastasis by inducing a reversible switch to invasively sprouting melanoma cells

Results

Discussion

Materials and methods