Analysis of glycoconjugate patterns of normal and hormone-induced dysplastic noble rat prostates, and an androgen-independent noble rat prostate tumor, by lectin histochemistry and protein blotting

BACKGROUND. Alteration of the expression of glycoconjugates is frequently o bserved in tumors. However, studies on the changes of cellular glycosylatio n in the early premalignant stage of prostate carcinogenesis are scarce. METHODS. The present study characterized and compared the glycoconjugates e xpressed in the dysplastic lateral prostate induced in Noble (Nb) rat by st eroid hormones and a transplantable androgen-independent Nb rat prostatic c arcinoma line (AIT) by lectin histochemistry and protein blotting. RESULTS. The results of lectin histochemistry show that the dysplastic pros tatic epithelium elaborates altered patterns of glycosylation, which are di stinct from the normal secretory epithelium. Some individual cells in the d ysplastic epithelium were intensely labeled by the N-acetylgalactosamine (G alNAc)-specific (agglutins from Glycine max [SBA], Helix aspera [HAA], Heli x pomatia [HPA], Vicia villosa [WA], Erythrina cristigalli [ECA]) and compl ex-type oligosaccharide-specific (Phaseolus vulgaris agglutin [PHA-E]) lect ins, indicating that these cells contained abundant GalNAc(alpha1,3)GalNAc/ Gal and Gal(beta1,4)GlcNAc(alpha1,2)Man(alpha1,6) residues. These lectins a lso bound to some tumor cells in the AIT, suggesting that these sugar resid ues are common in some dysplastic and neoplastic prostatic cells. The study has also identified several lectins (agglutins from Griffonia simplicifoli a [GS-I-B-4], Arachis hypogaea [PNA], Ricinus communis [RCA-I], Maackia amu rensis [MAA], Sambucus nigra [SNA]), which bound only to some AIT tumor cel ls but not to dysplastic epithelium, indicating that alpha/beta Gal and sia lic acid-containing glycoconjugates are expressed by neoplastic prostatic c ells. The results of lectin blottings with vulgnue agglutin [S-WGA] Ulex eu ropaeus agglutin [UEA-I] and PHA-E have identified five major glycoprotein bands (of apparent molecular weights of 116, 79, 64, 61, and 57 kDa) in the microsomal fraction of testosterone plus 17 beta -estradiol (T + E-2)-trea ted lateral prostate. These lectin-reactive bands were not detected in the AIT extracts. In the AIT microsomal extract, two glycoprotein bands of mole cular weights of 58 and 46 kDa were revealed by SEA and PNA. CONCLUSIONS. The present study shows that there is an increased expression of GalNAc(alpha1,3)GalNAc/Gal residues and triantennary complex-type oligos accharides in the dysplastic epithelial cells as compared to normal secreto ry epithelial cells in rat lateral prostate. This altered expression of gly coconjugates revealed in the dysplastic epithelium indicates an aberrant gl ycosylation in the early premalignant stage of prostate carcinogenesis. The results also show that the AIT tumor cells are heterogeneous in their glyc oconjugates and different from the dysplastic epithelial cells. Prostate 46 :21-32, 2001. (C) 2001 Wiley-Liss, Inc.