Clinical significance of preoperative serum sialic acid levels in colorectal cancer: utility in the detection of patients at high risk of tumor recurrence.

This study was conducted to evaluate the significance of preoperative serum sialic acid levels in the diagnosis and prognosis of colorectal cancer (CRC). Total sialic acid (TSA) was determined by the thiobarbituric acid method and normalized to total protein (TP). A postoperative follow-up of CRC patients classified as Dukes' stages A, B or C was performed and survival analysis was carried out to evaluate the impact of sialic acid levels on tumor recurrence. Our diagnostic studies indicate that TSA/TP is a better marker than either TSA or carcinoembryonic antigen (CEA), especially for the detection of CRC patients at an early stage. At a cutoff of 30.90 nmol/mg of protein, TSA/TP showed a sensitivity of 85% with a specificity of 97% to discriminate CRC patients from healthy donors. In survival analysis, both TSA and TSA/TP were found to be significant prognostic factors for tumor recurrence in CRC. Furthermore, TSA/TP could distinguish patients at high risk of recurrence within Dukes' stage B and in multivariate analysis it was identified as the best independent prognostic factor. According to our results, preoperative serum TSA/TP content could supply additional information to that provided by Dukes' stage about the prognosis of CRC patients.

Immunohistochemical analysis of sialic acid and fucose composition in human colorectal adenocarcinoma.

The expression of different sialoglycoconjugates and fucoglycoconjugates in normal mucosa and adenocarcinoma samples from 43 colorectal cancer patients was investigated by using specific lectins and applying a semiquantitative analysis. A pronounced decrease in the intracellular binding of the Maackia amurensis lectin, which recognizes alpha(2,3)-linked sialic acid residues, was found in the tumoral tissue. In contrast, a significant increase in the staining with the Sambucus nigra lectin (SNA I), which binds to alpha(2,6)-linked sialic acid residues, was detected in the epithelial cells as well as in the mucins from tumors. No significant differences in the reactivity with the Aleuria aurantia lectin, which recognizes the sequence Fuc(alpha1,6)GlcNAc, between normal and malignant colorectal tissues were detected. Furthermore, the correlation between lectin-binding profiles and the prognosis of colorectal cancer patients was examined. After an average postoperative follow-up period of 31 months, patients with tumors showing a strong SNA I staining presented a greater probability of disease recurrence. This result suggests that the intensity of staining with SNA I could be a valid parameter for predicting recurrence in colorectal cancer.

Differential expression of three sialidase genes in rat development.

Mammalian sialidases have been reported to give a great influence on a number of cellular functions including cell differentiation and cell growth by removal of sialic acids from glycoproteins and gangliosides. To understand the roles of the sialidases during development, we investigated expression pattern of three types of sialidase in developing rat brain and liver. For this purpose we cloned a new membrane-associated sialidase cDNA from rat brain. The cDNA encodes 418 amino acids containing three ASP-boxes characteristic of sialidases and the major transcript of 3.5 kb is highly expressed in brain and cardiac muscle but low in liver. Competitive polymerase chain reaction methods were developed to evaluate the mRNA level together with activity assays in comparison with cytosolic and lysosomal sialidases previously obtained. The results indicate that the expression of individual sialidase genes is spatiotemporally controlled with distinct roles in determining the concentration and components of sialo-glycoconjugates during development.