Expression of Po66-CBP, a galectin-8, in different types of primary and secondary broncho-pulmonary tumors.

The monoclonal antibody Po66 is an IgG1 immunoglobulin isolated from a human bronchial squamous carcinoma and directed against a carbohydrate binding protein, Po66-CBP, belonging to the galectin family involved in neoplastic processes. This Po66 antibody has been shown to be useful for immunoscintigraphic detection of squamous cell carcinoma metastasis. We examined the expression of Po66-CBP in a wider range of primary or secondary malignant tumors of the lung of various histological types. We studied 52 specimens of broncho-pulmonary tumors including 41 primary squamous, glandular or neuro-endocrine tumors and 11 secondary tumors of glandular, connective tissue, melanocytic or germinal origin as well as 9 extra-pulmonary primary tumors with histological types similar to lung metastases. An immunohistochemical study was performed using an amplification system on paraffin-embedded sections. All histological types were positive for Po66 antibody, the cell origin giving no influence on the expression of Po66-CBP. There was however a relation between Po66-CBP expression and the degree of differentiation notably for squamous cell cancer and neuro-endocrine tumors. The metastatic character of the tumor tissue did not affect Po66-CBP expression.

Two messenger RNAs and five isoforms for Po66-CBP, a galectin-8 homolog in a human lung carcinoma cell line.

Galectins are animal proteins which specifically bind beta-D-galactoside residues and their specific cellular function is not yet clearly established. However, these proteins seem to play a role in neoplastic transformations. Po66 is a murine monoclonal antibody directed against a protein from human lung carcinoma, Po66 Carbohydrate-Binding-Protein (Po66-CBP), which belongs to the galectin-8 family. Our results show that the Po66-CBP gene generates five transcripts by alternative splicing, which could give rise to five proteins: two proteins belong to the tandemly repeated galectin family and three belong to the single carbohydrate recognition domain galectins. All these proteins are encoded by a unique gene located in 1q42. Experiments carried out by reverse transcriptase-polymerase chain reaction show that the levels of expression of these five galectin-8 isoforms are variable during the culture time in SK-MES-1, a human lung squamous carcinoma cell line. Cancer Genome Anatomy Project database analysis confirms the presence of Po66-CBP in lung cancer and its absence in healthy lung.

Galectin-8: a complex sub-family of galectins (Review).

Galectins are animal lectins, that can specifically bind beta-galactosides. Twelve galectins have been described in vertebrates, belonging to three different groups: prototype, tandem-repeat and chimeric. These proteins seem to be involved in cellular interactions and neoplastic transformations. We present an overview of a particular galectin member: galectin-8. This galectin, which has been intensively studied over the last six years, presents a particular type of gene regulation. It is widely expressed in tumoral tissues and seems to be involved in integrin-like cell interactions. Studies show that the LGALS8 gene encodes for almost seven mRNAs by alternative splicing pathways and various polyadenylation sites. These mRNAs could encode for six isoforms of galectin-8, of which three belong to the tandem-repeat galectin group (with two carbohydrate binding domains) and the three others to the prototype group (one carbohydrate binding domain). All these isoforms seem to be differentially expressed in various tumoral cells. This untypical galectin-8 subfamily seems to have a complex expression regulation, that could be involved in cancer phenomena.

Sodium butyrate induces growth inhibition and modulates galectin-8 expression in human lung carcinoma cells.

Galectins are animal lectins, which may play a role in neoplastic transformation. Po66-Carbohydrate Binding Protein (Po66-CBP) belongs to the galectin-8 family and is expressed in lung tumor cells but not in normal ones. Recent studies showed that galectin-8 could be used for human lung squamous cell carcinoma radioimmunotherapy. To optimize this method of treatment, we attempted to increase galectin-8 expression in human lung tumor cells. A human lung squamous (SK-MES-1) or adeno (A 549) carcinoma cell line was grown with or without sodium butyrate. Cell growth, morphology, transcriptional, expression translational expression and cellular localization of galectin-8 were studied. 3 mM of sodium butyrate inhibited the two cell lines' growth after 48 hours of treatment, but only in SK-MES-1 cells galectin-8 expression is modulated without any secretion and cellular localization modifications, apoptosis or necrosis. Sodium butyrate could be an interesting tool in optimizing the radioimmunotherapy of human lung squamous carcinoma, but not of adenocarcinoma.

Immunohistochemical expression of the intracellular component of galectin-8 in squamous cell metaplasia of the bronchial epithelium in neoplastic and benign processes.

Specified galectins are known to play a role in regulating cell proliferation, differentiation, adhesion and migration. Po66, a mouse IgG1 monoclonal antibody produced by immunization against squamous cell cancer, reacts against a carbohydrate-binding protein (Po66-CBP), recently shown to be a member of the galectin family with a strong homology with galectin-8 (PCTA-1), identified as a human tumor-associated antigen. We studied Po66 in squamous metaplasia of the bronchi in order to determine whether it could be specifically involved in neoplastic conditions and if so, if it would be helpful in distinguishing metaplasia at risk of cancer. Twenty-eight formalin-fixed, paraffin-embedded archival tissues of 17 metaplasias with SCC, 3 metaplasia with distant neoplastic disease and 8 metaplasias with an inflammatory process, were immunostained using a streptavidin biotin peroxydase method. The squamous metaplasias were positively stained in non-neoplastic disease as well as in neoplastic processes. Expression was also observed in stromal and normal cells. Po66-CBP was not associated with a pre-neoplastic character. We discussed the expression of this intra-cellular component of galectin-8 according to the functions of galectins in cellular differentiation, host reaction against tumor, and inflammation.

Expression of Po66-CBP, a type-8 galectin, in different healthy, tumoral and peritumoral tissues.

UNLABELLED: A monoclonal antibody, Po66, recognized an antigen named Po66 carbohydrate binding protein (PO66-CBP), which was homologous to the galectin-8 protein. Two additional isoforms previously not described were characterized. The aim of this study was to compare the expression of Po66-CBP and its isoforms in different healthy, tumoral and peritumoral tissues and at last to determine the localization of the protein in tumors and distant tissues. MATERIALS AND METHODS: Reverse transcriptase PCR of Po66-CBP was performed on total RNA extract from eleven healthy and eleven tumoral and peritumoral tissue specimens. Antibody Po66 was used to localize the protein in the tumors and distant tissues by an immunohistochemistry method. RESULTS: Po66-CBP was expressed by half of the healthy tissues. One of the isoforms, the last often present in healthy tissues, was found in all tumoral and peritumoral tissues studied. Immunohistochemistry evidenced a gradient of protein expression in normal cells depending on the vicinity of tumoral tissue. Po66-CBP expression was modified in cancerous tissue, suggesting the implication of galectins in carcinogenesis.

[Radiation-induced DNA fragmentation evaluated by anti-poly(ADP-ribose)immunolabeling in CHO cells. Standardization with pulsed-field electrophoresis]. / Fragmentation radio-induite de l'ADN évaluée par immunomarquage anti poly (ADP-ribose) dans les CHO. Etalonnage par électrophorèse en champ pulsé.

The poly (ADP-ribose) polymerase is an ubiquitous nuclear protein capable of binding specifically to DNA strand breaks. It synthesizes ADP-ribose polymers proportionally to DNA breaks. The actual method of reference to determine DNA double strand breaks is pulsed-field gel electrophoresis, but this requires many cells. It thus appeared of interest to use poly (ADP-ribos)ylation to follow and estimate gamma-ray-induced DNA fragmentation at the level of isolated cells after gamma-irradiation in chinese hamster ovary cells (CHO-K1). The results obtained by the immunolabelling technique of ADP-ribose polymers were compared to those obtained by pulsed-field gel electrophoresis. They show that poly (ADP-ribos)ylation reflects the occurrence of radiation-induced DNA strand breaks. A clear relationship exists between the amount of ADP-ribose polymers detected and DNA double strand breaks after gamma-irradiation.