Differences in Expression of Oligosaccharide Determinants by Phenotypically Distinct Sublines of the Dunning 3327 Rat Prostate Cancer

Abstract

Oligosaccharides expressed by the 3327-H and 3327-MAT LyLu sublines of the Dunning rat prostate cancer model have been compared in formalin-fixed and routinely paraffin-embedded tumour tissues. Binding by lectins of defined specificity has been employed to identify expression of seven oligosaccharide structures by primary and metastatic prostatic carcinoma cells. Neuraminidase digestion was employed to reveal determinants masked by sialic acid.The presence of core Manα1→3(Manα1→6)Manβ1→4GlcNAcβ1→4 determinants recognised by Con-A (Canavalia ensiformis) confirmed expression of complex-type glycoconjugates by plasma membrane and cytoplasmic components of the 3327-H tumour but only by cytoplasmic determinants within 3327 MAT LyLu variant tumour-cells. The only other oligosaccharide freely expressed by either tumour-subline was (GlcNAcβ1→4GlcNAcβ1→4—)n, recognised by WGA (Triticum vulgaris). Prior to neuraminidase digestion, PNA (Arachis hypogaea) (which identifies Type I oligosaccharides: Galβ1→3GalNAc–) bound to pseudoluminal membranes of the 3327-H tumour. However, ECG (Erythrina cristagalli) (which identifies type II oligosaccharides: Galβ1→4GlcNAc–) did not bind to this tumour. Unmasked Type I (Galβ1→3GalNAc–) and Type II (Galβ1→4GlcNAc–) oligosaccharides were not identified in the MAT-LyLu variant. After neuraminidase digestion, PNA-binding was identified along pseudoluminal plasma membranes within 3327-H tumours but only within the cytoplasm of 3327-MAT LyLu primary and metastatic tumour cells. Following neuraminidase digestion, ECG-binding was observed along pseudoluminal plasma membranes of 3327-H tumours and heterogeneously within the cytoplasm of primary, but not metastatic 3327-MAT LyLu tumours. Terminal α/βGalNAc—residues recognised by SBA (Glycine max) were not freely expressed by either subline. These structures were readily detected along luminal membranes of 3327-H cells and weakly detected within the cytoplasm of primary but not metastatic MAT 3327-LyLu tumour cells following neuraminidase digestion. Fucosylated Type II structures (Fucα1→2Gal(GalNAc)–), recognised by UEA-1 (Ulex europaeus-1) and GalNAcα1→3GalNAc—structures recognised by DBF (Dolichos biflorus) were not identified as a component of either tumour subline. The different patterns of oligosaccharide expression, identified by lectin-binding, clearly differentiated between the two tumour sublines and distinguished them from normal prostatic epithelium.The Dunning 3327 rat prostatic cancer sublines offer a useful model with which to examine the relationship between cell-surface oligosaccharide structures and phenotypic variants within a defined tumour-cell population. Correlation with similar changes observed in human prostatic cancer may be of potential diagnostic and prognostic value.