Systematic analysis of the human tumor cell binding to human vs. murine E- and P-selectin under static vs. dynamic conditions

Abstract

Endothelial E- and P-selectins promote metastasis formation by interacting with sialyl-Lewis X and A (sLeX/sLeA) on circulating tumor cells. This interaction precedes extravasation and can take place under dynamic and static conditions. Metastasis formation is often studied in xenograft models. However, it is unclear whether species differences exist in the ligand specificity of human (h) vs. murine (m) selectins and whether different ligands are functional under dynamic vs. static conditions. We systematically compared the h vs. m E- and P-selectin (ESel/PSel) binding of a range of human tumor cells under dynamic vs. static conditions. The tumor cells were categorized by their sLeA/X status (sLeA+/sLeX+, sLeA−/sLeX+ and sLeA−/sLeX−). The general biological nature of the tumor–selectin interaction was analyzed by applying several tumor cell treatments (anti-sLeA/X blockade, neuraminidase, pronase and inhibition of O/N-glycosylation). We observed remarkable differences in the static vs. dynamic interaction of tumor cells with h vs. m ESel/PSel depending on their sLeA/X status. The tumor cell treatments mostly affected either static or dynamic as well as either h- or m-selectin interaction. mESel showed a higher diversity of potential ligands than hESel. Inhibition of O-GalNAc-glycosylation also affected glycosphingolipid synthesis. Summarized, different ligands on human tumor cells are functional under static vs. dynamic conditions and for the interaction with human vs. murine ESel/PSel. Non-canonical selectin ligands lacking the sLeA/X glycan epitopes exist on human tumor cells. These findings have important implications for the current development of glycomimetic, antimetastatic drugs and encourage the development of immunodeficient mice with humanized selectins.

Complementary Use of Carbohydrate Antigens Lewis a, Lewis b, and Sialyl-Lewis a (CA19.9 Epitope) in Gastrointestinal Cancers: Biological Rationale towards a Personalized Clinical Application

“…Due to the ability to act as selectin ligands, both sLea and the type 2 chain isomer sialyl-Lewis x (Siaα2,3Galβ1,4[Fucα1,3]GlcNAc, in which the galactose residue is linked to N-acetylglucosamine through a β1,4 linkage), have been extensively investigated in recent years (reviewed in [ 35 , 36 ]). Because of their capacity to enhance the malignant potential of cancer cells, as proven in model systems [ 36 , 37 ]), it is important to assess the actual expression of such structures by native cancers [ 38 , 39 ] compared to the normal counterpart. The ability to synthesize the various epitopes depends on the expression of specific glycosyltransferase enzymatic activities.…”

The Role of Platelet Cell Surface P-Selectin for the Direct Platelet-Tumor Cell Contact During Metastasis Formation in Human Tumors

“…Furthermore, not only different P-selectin levels on activated human vs. murine platelets, but also different ligands at the tumor cell surface used for binding human vs. murine Pselectin have to be considered: as reported quite recently, there is considerably more murine than human P-selectin binding to human tumor cells particularly when tumor cells express both canonical selectin ligands, i.e., the glycan epitopes sialyl-Lewis A and X (sLeA+/X+); there was much less difference seen with sLeA-/ sLeX+ or sLeA-/ sLeX-cells suggesting that the sLeA epitope (capping a variety of different carbohydrate structures) might specifically support murine P-selectin binding (109). All tested tumor cell lines stemming from a range of entities shared the ability to bind human and murine P-selectin, again underlining the crucial importance of P-selectin in the context of cancer.…”

“…All tested tumor cell lines stemming from a range of entities shared the ability to bind human and murine P-selectin, again underlining the crucial importance of P-selectin in the context of cancer. Interestingly, several tumor cell treatments aiming at disrupting tumor cell/ P-selectin interaction impaired human vs. murine P-selectin binding quite differently suggesting that different ligands are functional for both species (109). Another dimension of complexity results from the differential binding and adhesion behavior of human tumor cells to murine vs. human P-selectin under static and dynamic experimental conditions, respectively: while all tested human tumor cells bound human and murine P-selectin under static conditions, only sLeA+/X+ and sLeX+ cells (but not sLeA-/sLeX-cells) were able to adhere dynamically on murine P-selectin.…”

“…Interestingly, several tumor cell treatments aiming at disrupting tumor cell/ P-selectin interaction impaired human vs . murine P-selectin binding quite differently suggesting that different ligands are functional for both species ( 109 ). Another dimension of complexity results from the differential binding and adhesion behavior of human tumor cells to murine vs .…”

“…human P-selectin under static and dynamic experimental conditions, respectively: while all tested human tumor cells bound human and murine P-selectin under static conditions, only sLeA+/X+ and sLeX+ cells (but not sLeA-/sLeX- cells) were able to adhere dynamically on murine P-selectin. Among them, only those co-expressing PSGL-1 were able to adhere dynamically on human P-selectin ( 109 ). These observations imply that the ability of human tumor cells to directly interact with platelets inside the bloodstream (dynamic conditions) or outside the bloodstream (static conditions) might be remarkably different in mice and men.…”