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 observed in tumors. However, studies on the changes of cellular glycosylation in the early premalignant stage of prostate carcinogenesis are scarce.

METHODS

The present study characterized and compared the glycoconjugates expressed in the dysplastic lateral prostate induced in Noble (Nb) rat by steroid hormones and a transplantable androgen-independent Nb rat prostatic carcinoma line (AIT) by lectin histochemistry and protein blotting.

RESULTS

The results of lectin histochemistry show that the dysplastic prostatic epithelium elaborates altered patterns of glycosylation, which are distinct from the normal secretory epithelium. Some individual cells in the dysplastic epithelium were intensely labeled by the N-acetylgalactosamine (GalNAc)-specific (agglutins from Glycine max [SBA], Helix aspera [HAA], Helix pomatia [HPA], Vicia villosa [VVA], Erythrina cristigalli [ECA]) and complex-type oligosaccharide-specific (Phaseolus vulgaris agglutin [PHA-E]) lectins, indicating that these cells contained abundant GalNAc(alpha1,3)GalNAc/Gal and Gal(beta1,4)GlcNAc(alpha1,2)Man(alpha1,6) residues. These lectins also bound to some tumor cells in the AIT, suggesting that these sugar residues are common in some dysplastic and neoplastic prostatic cells. The study has also identified several lectins (agglutins from Griffonia simplicifolia [GS-I-B4], Arachis hypogaea [PNA], Ricinus communis [RCA-I], Maackia amurensis [MAA], Sambucus nigra [SNA]), which bound only to some AIT tumor cells but not to dysplastic epithelium, indicating that alpha/betaGal and sialic acid-containing glycoconjugates are expressed by neoplastic prostatic cells. The results of lectin blottings with Triticum vulgare agglutin [S-WGA] Ulex europaeus 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 17beta-estradiol (T + E2)-treated lateral prostate. These lectin-reactive bands were not detected in the AIT extracts. In the AIT microsomal extract, two glycoprotein bands of molecular weights of 58 and 46 kDa were revealed by SBA and PNA.

CONCLUSIONS

The present study shows that there is an increased expression of GalNAc(alpha1,3)GalNAc/Gal residues and triantennary complex-type oligosaccharides in the dysplastic epithelial cells as compared to normal secretory epithelial cells in rat lateral prostate. This altered expression of glycoconjugates revealed in the dysplastic epithelium indicates an aberrant glycosylation in the early premalignant stage of prostate carcinogenesis. The results also show that the AIT tumor cells are heterogeneous in their glycoconjugates and different from the dysplastic epithelial cells.