Abstract
BackgroundNumerous studies indicate that cancer cells present an aberrant glycosylation pattern that can be detected by lectin histochemistry. Lectins have shown the ability to recognise these modifications in several carcinomas, namely in the prostate carcinoma, one of the most lethal diseases in man. Thus, the aim of this work was to investigate if the α-D-galactose-binding plant lectin frutalin is able to detect such changes in the referred carcinoma. Frutalin was obtained from different sources namely, its natural source (plant origin) and a recombinant source (Pichia expression system). Finally, the results obtained with the two lectins were compared and their potential use as prostate tumour biomarkers was discussed.ResultsThe binding of recombinant and native frutalin to specific glycoconjugates expressed in human prostate tissues was assessed by using an immuhistochemical technique. A total of 20 cases of prostate carcinoma and 25 cases of benign prostate hyperplasia were studied. Lectins bound directly to the tissues and anti-frutalin polyclonal antibody was used as the bridge to react with the complex biotinilated anti-rabbit IgG plus streptavidin-conjugated peroxidase. DAB was used as visual indicator to specifically localise the binding of the lectins to the tissues. Both lectins bound to the cells cytoplasm of the prostate carcinoma glands. The binding intensity of native frutalin was stronger in the neoplasic cells than in hyperplasic cells; however no significant statistical correlation could be found (P = 0.051). On the other hand, recombinant frutalin bound exclusively to the neoplasic cells and a significant positive statistical correlation was obtained (P < 0.00001). However, recombinant frutalin did not recognise all malignant prostate cases and, when positive, the binding to those tissues was heterogeneous.ConclusionNative and recombinant frutalin yielded different binding responses in the prostate tissues due to their differences in carbohydrate-binding affinities. Also, this study shows that both lectins may be used as histochemical biomarkers for the prostate cancer. Moreover, the successful use of a recombinant lectin in immunohistochemical studies of prostate cancer was for the first time demonstrated, highlighting the advantages of using recombinant systems in the preparation of pure lectin samples for diagnostic purpose.
Highlights
Numerous studies indicate that cancer cells present an aberrant glycosylation pattern that can be detected by lectin histochemistry
In each run a positive control and a negative control were included
Native frutalin bound to all the studied cases of prostate carcinoma (100%; 20/20), as well as to all the studied cases of benign prostate hyperplasia (BPH) (100%; 25/ 25)
Summary
Numerous studies indicate that cancer cells present an aberrant glycosylation pattern that can be detected by lectin histochemistry. Prostate carcinoma is one of the most common causes of cancer-related deaths in men older than 50 years of age It is predominantly a disease of older men, with a peak incidence between the ages of 65 and 75 years. The glycosylation profile on tumour cells glycoproteins is distinctly different from that on normal cells, due to the blockage of the glycosylation pathways. This phenomenon results in the incomplete elongation of O-glycans and premature sialylation, leading to the expression of shorter and modified cancerassociated oligosaccharides such as T, sialyl-T, Tn, sialylTn, LewisX (LeX) and sialyl-LeX, with a drastic impact in the cells normal function [9,10]
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