DOES THE LECTIN HELIX-POMATIA AGGLUTININ BIND TO HYALURONIC-ACID IN BREAST AND COLON-CANCER

The lectin Helix pomatia agglutinin (HPA) has been successfully used a s an indicator of metastatic spread in a number of epithelial neoplasm s including breast, colorectal, gastric, prostate and oesophageal canc ers. Despite its use, the binding partners of HPA in tissue sections h ave not been defined at the molecular level. HPA has two main binding specificities: 1) N-acetylgalactosamine (GalNac) and 2) N-acetylglucos amine (GlucNac). In order to determine whether HPA binds to hyaluronic acid (a GlucNac-containing glycosaminoglycan) a dot blot assay was pe rformed which confirmed hyaluronic acid as a binding partner for HPA. In the next step, experiments were performed using hyaluronate lyase p redigestion before HPA application on clinical and experimental human tumours grown in severe combined immunodeficient (SCID) mice to assess whether the HPA binding in the dot blot system also occurred in tissu e sections. The results from all samples indicate that hyaluronate lya se pretreatment does not alter HPA binding to tumour cells both in the patients' samples and in the human cancer cell lines grown in SCID mi ce. This also indicates that HPA binds to similar carbohydrate residue s in patients' samples and in SCID mouse-grown human tumour cells. It seems, therefore, unlikely that HPA recognises hyaluronic acid as a bi nding partner in tissue sections of human tumours, and hence GalNac-co ntaining glycoproteins seem to be the more likely ligands for HPA in c ancer cells.