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

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 in vivo. 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.

Spontaneous metastasis xenograft models link CD44 isoform 4 to angiogenesis, hypoxia, EMT and mitochondria‐related pathways in colorectal cancer

“…The efficiency of CD44 kd was confirmed by flow cytometry. The same construct has been tested and successfully employed in two other cell lines and corresponding xenograft models, specifically HOS osteosarcoma and MeWo melanoma cells/xenografts [ 41 ].…”

“…All these functions would involve CD44 as a receptor within the metastatic cascade. In addition, the decoration of CD44 by selectin ligands would represent the ligand function of CD44, which would interact with the endothelial selectins [ 40 , 41 ]. Hence, CD44 appears to be crucially involved in several steps of the metastatic cascade [ 38 ].…”

Insights into the Role of Sialylation in Cancer Metastasis, Immunity, and Therapeutic Opportunity

“…Through these cancer cell stimulations, CCL5 derived from mesenchymal stem cells further boosts cancer cells’ motility, invasion, and metastasis [ 65 ]. Additionally, E-selectin interacts with its high-affinity ligands, sialyl Lewis X (sLeX) and sialyl Lewis A (sLeA), increasing cancer cell adherence and lung metastasis [ 66 ]. As ligands of selectins, sialic acids contribute to the negative charges of tumor cell surfaces.…”

Comparison of ex vivo bioluminescence imaging, Alu-qPCR and histology for the quantification of spontaneous lung and bone metastases in subcutaneous xenograft mouse models

“…However, our cumulative experience with the detection of bone metastases by ex vivo BLI suggested that in a notable percentage of mice the ex vivo BLI signals could not be validated by histology while in some cases large, vital bone metastases as per histology were not apparent via ex vivo BLI. One further technique we have been using regularly in parallel for the quantification of the bone metastatic burden, is quantitative real time-PCR for human-specific DNA sequences ( Alu -qPCR) [ 7 , 14 , 16 , 17 ]. Therefore, the aim of the present study was to compare ex vivo BLI, Alu -qPCR and histology as three independent methods for the quantification of spontaneous metastases in xenograft models, specifically comparing their value for lung and bone metastasis quantification.…”