Tumor cell E-selectin ligands determine partialefficacy of bortezomib on spontaneous lung metastasis formation of solid human tumors in vivo

Tobias Lange,Christian Börnchen,Klaus Pantel,Albrecht Schwab,Andreas Block,Ursula Valentiner,Valsamma Abraham,Lisa Staffeldt,Anna-Maria Dück,Ann-Kristin Ahlers,Jens K Habermann,Daniel Wicklein,Christine Stürken,Rainer Kiefmann,Horace M Delisser,Carolin Pahlow,Hanna Maar,Udo Schumacher,Anke Baranowsky,Sarah Starzonek,Timo Gemoll,Kristoffer Riecken,Vera Labitzky,Etmar Bulk,Sandra Genduso,Alexander Bauer

doi:10.1016/j.ymthe.2022.01.017

Abstract

Extravasation of circulating tumor cells (CTCs) is critical for metastasis and is initiated by adhesive interactions between glycoligands on CTCs and E-selectin on endothelia. Here, we show that the clinically approved proteasome inhibitor bortezomib (BZM; Velcade) counteracts the cytokine-dependent induction of E-selectin in the lung mediated by the primary tumor, thereby impairing endothelial adhesion and thus spontaneous lung metastasis invivo. However, the efficacy of BZM crucially depends on the tumor cells' E-selectin ligands, which determine distinct adhesion patterns. The canonical ligands sialyl-Lewis A (sLeA) and sLeX mediate particularly high-affinity E-selectin binding so that the incomplete E-selectin-reducing effect of BZM is not sufficient to disrupt adhesion or metastasis. In contrast, tumor cells lacking sLeA/X nevertheless bind E-selectin, but with low affinity, so that adhesion and lung metastasis are significantly diminished. Such low-affinity E-selectin ligands apparently consist of sialylated MGAT5 products on CD44. BZM no longer has anti-metastatic activity after CD44 knockdown in sLeA/X-negative tumor cells or E-selectin knockout in mice. sLeA/X can be determined by immunohistochemistry in cancer samples, which might aid patient stratification. These data suggest that BZM might act as a drug for inhibiting extravasation and thus distant metastasis formation in malignancies expressing low-affinity E-selectin ligands.

Highlights

The formation of distant metastases begins with the detachment of individual cancer cells or small cell clusters from the primary tumor (PT)and their invasion across the underlying basement membrane, migration through the adjacent extracellular matrix (ECM), and subsequent intravasation into the bloodstream as circulating tumor cells (CTCs).[1]
We analyzed whether the BZM-mediated reduction of E-selectin, ICAM-1, and VCAM-1 has a functional consequence for the adhesion of human tumor cells to human umbilical vein ECs (HUVECs) in laminar flow adhesion assays
In our proof-of-concept experiments, we found that two gastrointestinal adenocarcinoma cell lines (HT29 and PaCa5061) were not impaired during endothelial adhesion upon BZM treatment of the endothelial cells (ECs) (BZMresistant), while the adhesion of two tumor cell lines of non-epithelial origin (HOS and MeWo) was significantly reduced (BZM-sensitive; Figure 1D)

Summary

Introduction

The formation of distant metastases begins with the detachment of individual cancer cells or small cell clusters from the primary tumor (PT). Their invasion across the underlying basement membrane, migration through the adjacent extracellular matrix (ECM), and subsequent intravasation into the bloodstream as circulating tumor cells (CTCs).[1] During circulation, CTCs are exposed to different intrinsic and extrinsic selection pressures (anoikis induced by detachment from the ECM of the PT, mechanical shear stress, immune cells, especially natural killer [NK] cells).[2,3] it is widely assumed that the extravasation of CTCs into the stroma of the organ of the later metastasis represents a bottleneck step of the metastatic cascade.[4,5] The initial event of extravasation is the attachment of CTCs to the inner lining of the blood vessels, the endothelium. Neither the full repertoire of possible E-selectin ligands on human tumor cells nor the role of other endothelial CAMs is fully known to date.[6,8] Several

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