Relationship of Sialyl-Lewisx/a Underexpression and E-Cadherin Overexpression in the Lymphovascular Embolus of Inflammatory Breast Carcinoma

Abstract

Inflammatory breast carcinoma (IBC) isOur screening methods for certain types of breast cancer such as inflammatory breast cancer (IBC) have not impacted the disease's age-adjusted 5 year mortality because these types of breast cancer do not remain organconfined before they are detected. 1 One telltale sign of lack of organ confinement is the presence of lymphovascular invasion, a finding that is most pronounced in IBC. 2 Lymphovascular invasion is defined by tumor emboli within lymphovascular spaces. 3 These emboli have a unique microscopic appearance of compact clumps of tumor cells retracted away from the surrounding endothelial cell layer lining the lymphovascular space. The molecular determinants of this phenotype remain undefined. Recently our laboratory established a human SCID model of IBC (MARY-X) that exhibited florid lymphovascular tumor emboli in vivo and compact spheroids in vitro. 4,5 We have characterized, in part, the molecular basis of the IBC phenotype using this model. Our initial studies indicated that MARY-X overexpressed both Ecadherin and MUC1. 4 We chose to focus on E-cadherin initially and demonstrated that both the tumor cell emboli and the in vitro spheroids formed on the basis of an intact and overexpressed E-cadherin/␣,␤-catenin axis that mediated tumor cell adhesion analogous to the embryonic blastocyst. 5 Disruption of the E-cadherin/␣,␤-catenin axis with either anti-E-cadherin antibodies or E-cadherin dominant-negative mutant approaches caused complete disadherence of the tumor emboli in vivo. Furthermore in addition to these two manipulations, trypsin proteolysis and Ca ϩϩ depletion caused complete disadherence of the spheroids in vitro. In the present study we decided to investigate the role of overexpressed MUC1 and a possible mechanism that might explain the apparent lack of binding of the tumor embolus to the surrounding endothelium.

Deficiency in surface expression of E‐selectin ligand promotes lung colonization in a mouse model of breast cancer

“…For instance, it has been proposed that the lack of sLe x enhanced formation of tumor embolus via stronger E-cadherin interaction within each embolus, which led to more efficient metastatic dissemination. 20 However, we did not observe any difference in anti-E-cadherin antibody binding to the cell variants (data not shown) or emboli formation among the sLe x -negative subpopulation in vitro or in situ, similar to the phenotype reported by Barsky's group. 20 A phenotype similar to what we observed has been associated with an increase in b-1fi6-GlcNAc branching structures on complex N-linked carbohydrates.…”

“…20 However, we did not observe any difference in anti-E-cadherin antibody binding to the cell variants (data not shown) or emboli formation among the sLe x -negative subpopulation in vitro or in situ, similar to the phenotype reported by Barsky's group. 20 A phenotype similar to what we observed has been associated with an increase in b-1fi6-GlcNAc branching structures on complex N-linked carbohydrates. 51 Replacing b1fi6 branching structures with bisecting GlcNAc has led to enhanced homotypic adhesion of tumor cells via increased functional expression of E-cadherin.…”

“…Others investigating the basis underlying the metastatic properties of inflammatory breast carcinoma also showed, consistent with our data, that a decrease or lack of sLe x/a promotes passive metastasis of tumor cells in a xenograft model. 20,46 Together such findings indicate that the conventional belief that metastatic tendency is increased by upregulation of sialylated Lewis oligosaccharides and a subsequent increase in tumor cell-endothelial cell adhesion might be restricted to metastatic events associated with bloodborne tumor cells.…”

“…Experimental metastasis models such as these exclude the early steps of the metastatic cascade that might be impacted by expression of selectin ligands. In this regard, Alpaugh et al 20 showed in a human-SCID model of inflammatory breast carcinoma, which is a nonsyngeneic passive model, that the lack of sLe x/a promotes passive metastasis. It would be advantageous to use a syngeneic model in which tumor cells are injected into the orthotopic site and tumor cell dissemination and distant organ colonization are then assessed because in such a model tumor cells will be forced to complete all or most of the steps needed for metastasis that are completed by cells originating in the primary tumor.…”

The lymphovascular embolus of inflammatory breast cancer exhibits a Notch 3 addiction

“…These spheroids resemble the human blastocyst. Both structures overexpress E-cadherin, and have a deficiency of fucosyltransferases and surface fucosylation (Alpaugh et al, 2002b), but are efficient at organ implantation. On account of these similarities, we wondered whether the spheroids might express a blastocyst-like expression profile.…”