Multiple proteases are involved in mesothelin shedding by cancer cells

Chin-Hsien Tai,Thorkell Andresson,Xiufen Liu,Ira Pastan,Alexander Chan

doi:10.1038/s42003-020-01464-5

Abstract

Mesothelin (MSLN) is a lineage restricted cell surface protein expressed in about 30% of human cancers and high MSLN expression is associated with poor survival in several different cancers. The restricted expression of MSLN in normal tissue and its frequent expression in cancers make MSLN an excellent target for antibody-based therapies. Many clinical trials with agents targeting MSLN have been carried out but to date none of these agents have produced enough responses to obtain FDA approval. MSLN shedding is an important factor that may contribute to the failure of these therapies, because shed MSLN acts as a decoy receptor and allows release of antibodies bound to cell-surface MSLN. We have investigated the mechanism of shedding and show here that members of the ADAM, MMP and BACE families of proteases all participate in shedding, that more than one protease can produce shedding in the same cell, and that inhibition of shedding greatly enhances killing of cells by an immunotoxin targeting MSLN. Our data indicates that controlling MSLN shedding could greatly increase the activity of therapies that target MSLN.

Highlights

Mesothelin (MSLN) is a lineage restricted cell surface protein expressed in about 30% of human cancers and high MSLN expression is associated with poor survival in several different cancers
Our results show that MSLN is cleaved at many sites close to the cell membrane, that ADAM10, ADAM17, BACE2, BACE1, and MMP15 all have a role in MSLN shedding, and that more than one sheddase can catalyze MSLN release in the same cell line
To determine the sites at which MSLN is cut, we studied five different cancer cell lines: KLM1, KB31, OVCAR8, A431/H9 cells, and RH16, a primary mesothelioma cell line

Summary

Introduction

Mesothelin (MSLN) is a lineage restricted cell surface protein expressed in about 30% of human cancers and high MSLN expression is associated with poor survival in several different cancers. MSLN shedding is an important factor that may contribute to the failure of these therapies, because shed MSLN acts as a decoy receptor and allows release of antibodies bound to cell-surface MSLN. Shedding is an impediment to antibody-based therapies, because it provides a sink within tumors that reduces their efficiency and promote their release from the cell surface before they can kill the cell[6]. To understand MSLN shedding in more depth, we determined the cut sites generated when MSLN is shed in different cancer cell lines. Our results show that MSLN is cleaved at many sites close to the cell membrane, that ADAM10, ADAM17, BACE2, BACE1, and MMP15 all have a role in MSLN shedding, and that more than one sheddase can catalyze MSLN release in the same cell line

Methods

Results

Conclusion