MON-LB85 Aberrant Glycan Expression Changes With the Phenotype of Follicular Thyroid Tumours

Abstract

Glycosylation is the most common post‐translational modification of proteins and plays an important role in cell communication, interaction and adhesion. Aberration of glycosylation is a hallmark of cancer cells and plays an important role in oncogenesis and cancer progression including metastasis1. One of the markers of aberrant glycosylation (O-linked) is the binding of the lectin Helix pomatia agglutinin (HPA), and this has been shown in a wide range of human cancers2, especially in tumours with a more aggressive phenotype. To study the alteration in cellular glycosylation, detected by lectin Helix pomatia agglutinin (HPA) binding in various phenotypes of follicular thyroid tumours, ranging from adenoma to carcinoma and metastatic follicular thyroid cancers. Lectin histochemistry was performed on archival paraffin wax‐embedded specimens of 6 follicular adenomas, 10 minimally invasive follicular carcinomas, 13 widely invasive follicular cancers and 4 metastatic follicular thyroid cancers. For positive controls, sections of rat kidney were used, which shows strong and characteristic HPA labelling were included in each labelling experiment. For negative controls, the lectin was omitted and the specificity of binding was confirmed by incubating the sections with HPA in the presence of 0·1‐mol/l GalNAc. Sections were scored as positive when 5% or more of the cancer cells labelled positive and scored as negative when less than 5% labelled positive for HPA binding. Assessments of HPA binding were performed by two observers who were blinded to the identity of the sample, and their results were compared. Positive labelling was seen in 20% of adenomas, 60% of minimally invasive carcinomas, 77% of widely invasive carcinomas and 100% of metastatic carcinomas (p<0.05). In the minimally invasive carcinoma group, all tumours that showed vascular invasion showed positive HPA labelling, whereas only 20% of patients with capsular invasion showed positivity. We speculate that as the phenotype of the thyroid tumours changes from benign to the malignant phenotype, the glycan expressions change. However, the underlying molecular mechanisms leading to this change needs to be further investigated.