Biochemical and histochemical detection of the sialic acids in mammary tumours of bitches

Abstract

This study describes the expression and localisation of sialic acid in mammary tumours in bitches. Tissue total sialic acid (TSA) concentrations were detected spectrophotometrically. Localisation of sialic acids in mammary tissue was visualised using the biotin-conjugated Sambucus nigra lectin (SNA), specific for alpha 2,6-linked sialic acid, and Maaickia amurensis lectin (MAL), specific for alpha 2,3-linked sialic acid. The mean value of tissue TSA of malignant tumours (1.46 +/- 0.14 mu mol/g protein) was significantly higher (p < 0,001) than that in healthy tissues (0.26 +/- 0.07 mu mol/g protein) as well as in tissues with benign types of tumour (0.50 +/- 0.06 mu mol/g protein). We could not find a significant difference in sialic acid concentrations between adenomas and normal tissue (p > 0.05). Tissue TSA content in the same type of tumours was not always equal. In histochemical analyses both the staining intensity and localisation patterns of SNA and MAL showed marked differences. The staining for SNA and MAL was only low or not present in normal mammary tissues but high in carcinomas. In malign tumours binding sites for SNA were predominantly in epithelial cells and in individual cells infiltrating the fibrous tissue. However, the binding sites for MAL were predominantly in fibrous tissue, capillary and lymphatic endothelia. Contrary to malignant tumours, a moderate staining was observed in benign tumours. The staining was mainly in epithelial cells, in fibrocytes and in myoepithelial cells. It was not always the case that the same type of tumours revealed the same staining intensity localisation for the lectins. The results obtained from the present study suggest that elevated levels of sialic acid in malignant mammary tumours may play an important role in the detachment of carcinoma cells from the primary tumour and would be of critical importance for the metastasis of turnout cells.