Lectin-binding properties of human breast cancer cell lines and human milk with particular reference to Helix pomatia agglutinin

Several studies have shown binding of a variety of lectins to breast cancer cells in tissue sections. In particular, binding of the lectin from the Roman snail, Helix pomatia agglutinin (HPA), to breast cancer cells is linked with a poor prognosis. The molecular basis for lectin binding to metastatic breast cancers is not known. To elucidate this in a model system, lectin-binding patterns of seven human breast cancer cell lines were investigated, their cell membranes were isolated, and HPA binding was assessed. In addition, the influence of fixation and processing on lectin-binding sites was also investigated. Binding of lectins to the tumor cells was very heterogeneous between and within the different cell lines and was influenced by fixation and processing. However, some cell lines showed HPA-binding sites both in vivo and in tissue sections. Analysis of the isolated cell membrane glycoproteins from these cell lines on Western blots revealed that HPA can bind to several membrane glycoproteins. In contrast, human milk shows only one major milk glycoprotein that is HPA-positive. Therefore, a switch in glycosylation appears to be taking place during the transformation to a metastatic phenotype.