The T/Tn-Specific Helix pomatia Lectin Induces Cell Death in Lymphoma Cells Negative for T/Tn Antigens

Morniga G is a T/Tn-specific lectin, inducing cell death in Tn-positive leukemias but not in healthy lymphocytes. Helix pomatia lectin (HPA) is another T/Tn-specific lectin, currently used as tool for cancer diagnostics. The HPA-mediated tumor cell death was evaluated on human leukemia and mouse lymphoma cells, and compared to the effect of Morniga G. Both lectins induced an equivalent percentage of cell death in Tn-positive Jurkat human leukemia. In contrast, EL4 mouse lymphoma resisted Morniga G-mediated cytotoxicity but were killed by HPA at concentrations of 2.5 μg/mL (0.032 nM) and higher. In both malignant cells, HPA-mediated cell death showed features compatible with apoptosis (annexin-externalization, caspase-activation, mitochondrial membrane depolarization, and ROS production). Cytometry analysis indicated that EL4 cells are T/Tn-negative. Because previous results showed a high amount of N-acetylgalactosamine (GalNAc, sugar present in Tn antigen) on EL4 cell surface, this GalNAc could be involved in the formation of truncated O-glycans other than the T/Tn residues. When compared to Morniga G, bioinformatic analysis suggested that HPA benefits from an extended carbohydrate-binding site, better adapted than Morniga G to the accommodation of more complex branched and truncated O-glycans (such as core 2). Finally, HPA killed EL4 cells but not healthy lymphocytes in a mixture of lymphoma cells + lymphocytes, suggesting that HPA selectively triggers tumor cell death.

Detection of O-glycosylated proteins from different Trichinella species muscle larvae total extracts

The aim of the work was to analyze oligosaccharide composition with the focus on O-linked glycoproteins presence in the total extract obtained from different Trichinella species muscle larvae by means of lectin affino-blot with lectins selected for their sugar specificity. The absence of reactivity with two lectins, Tritrichomonas mobilensis lectin and Maackia amurensis agglutinin, indicated that the species of the Trichinella genus do not synthesize sialic acid. Reactivity with Helix pomatia lectin, Vicia villosa lectin-B4, peanut agglutinin and Ulex europeus lectin-I identified the presence of O-linked glycans identical to carcinoma-associated Tn-antigen (GalNAc-α-Ser/Thr) and T-antigen (Gal-β1,3-GalNAc-α-Ser/Thr) and also structures analogous to ABH-blood group antigens. The results obtained may contribute to a better understanding of the glycobiology of this parasitic nematode in relation to occupation of its intracellular niches.

Histochemistry to detect Helix pomatia lectin binding in breast cancer: methodology makes a difference.

A number of studies have shown that altered cellular glycosylation, as detected by binding of Helix pomatia lectin to paraffin sections, is associated with metastatic disease and consequent poor patient prognosis in breast and other cancers. In a 24-year retrospective study, sections of 373 primary breast cancers were stained for binding of the lectin using two different histochemical techniques: a direct method (using peroxidase-conjugated lectin) and an indirect method (using native, unconjugated lectin). Similar percentages of cases were positive (79%) and negative (21%) for lectin binding with either technique, but there was enormous inconsistency when individual cases were examined. A total of 38/373 (10.2%) cases that were negative by the indirect method were positive by the direct method, and 37/373 (9.9%) cases that were negative by the direct method were positive by the indirect method. Life tables calculated for lectin staining vs nonstaining cases showed a very strong correlation between lectin binding and long-term survival (p < 0.0001) when staining was performed by the indirect method, but only very weak correlation with prognosis (p < 0.03, borderline significance) when the direct technique was employed. SDS-PAGE revealed that there were differences in breast cancer glycoproteins recognized by native lectin and peroxidase-conjugated lectin immobilized on Sepharose 4B affinity beads. Helix pomatia lectin binding appears to be an intriguing and potentially valuable marker of biological behavior in breast cancer. This study emphasizes the importance of selecting an appropriate immunohistochemical technique for its visualization.