Gangliosides and neutral glycosphingolipids of normal tissue and oat cell carcinoma of human lung

Sphingolipids and plasma membrane hydrolases in human primary bronchial cells during differentiation and their altered patterns in cystic fibrosis

Human primary bronchial epithelial cells differentiated in vitro represent a valuable tool to study lung diseases such as cystic fibrosis (CF), an inherited disorder caused by mutations in the gene coding for the Cystic Fibrosis Transmembrane Conductance Regulator. In CF, sphingolipids, a ubiquitous class of bioactive lipids mainly associated with the outer layer of the plasma membrane, seem to play a crucial role in the establishment of the severe lung complications. Nevertheless, no information on the involvement of sphingolipids and their metabolism in the differentiation of primary bronchial epithelial cells are available so far. Here we show that ceramide and globotriaosylceramide increased during cell differentiation, whereas glucosylceramide and gangliosides content decreased. In addition, we found that apical plasma membrane of differentiated bronchial cells is characterized by a higher content of sphingolipids in comparison to the other cell membranes and that activity of sphingolipids catabolic enzymes associated with this membrane results altered with respect to the total cell activities. In particular, the apical membrane of CF cells was characterized by high levels of ceramide and glucosylceramide, known to have proinflammatory activity. On this basis, our data further support the role of sphingolipids in the onset of CF lung pathology.

Influenza virus entry via the GM3 ganglioside-mediated platelet-derived growth factor receptor β signalling pathway

The possible resistance of influenza virus against existing antiviral drugs calls for new therapeutic concepts. One appealing strategy is to inhibit virus entry, in particular at the stage of internalization. This requires a better understanding of virus-host interactions during the entry process, including the role of receptor tyrosine kinases (RTKs). To search for cellular targets, we evaluated a panel of 276 protein kinase inhibitors in a multicycle antiviral assay in Madin-Darby canine kidney cells. The RTK inhibitor Ki8751 displayed robust anti-influenza A and B virus activity and was selected for mechanistic investigations. Ki8751 efficiently disrupted the endocytic process of influenza virus in different cell lines carrying platelet-derived growth factor receptor β (PDGFRβ), an RTK that is known to act at GM3 ganglioside-positive lipid rafts. The more efficient virus entry in CHO-K1 cells compared to the wild-type ancestor (CHO-wt) cells indicated a positive effect of GM3, which is abundant in CHO-K1 but not in CHO-wt cells. Entering virus localized to GM3-positive lipid rafts and the PDGFRβ-containing endosomal compartment. PDGFRβ/GM3-dependent virus internalization involved PDGFRβ phosphorylation, which was potently inhibited by Ki8751, and desialylation of activated PDGFRβ by the viral neuraminidase. Virus uptake coincided with strong activation of the Raf/MEK/Erk cascade, but not of PI3K/Akt or phospholipase C-γ. We conclude that influenza virus efficiently hijacks the GM3-enhanced PDGFRβ signalling pathway for cell penetration, providing an opportunity for host cell-targeting antiviral intervention.

Current status of immunotherapy for the treatment of lung cancer

Immunotherapy is a novel approach for the treatment of systemic malignancies. Passive and adaptive immunotherapy have been applied to the treatment of a wide variety of solid tumors such as malignant melanoma (1), renal cell carcinoma (2) and ovarian cancer (3). Several early clinical trials of immune based therapy for both non-small (NSCLC) and small cell lung cancer (SCLC) have demonstrated limited or no success (3),(4) but recent trials of antigen-specific cancer immunotherapy have shown early therapeutic potential and are now being rigorously evaluated on a larger scale (5). In this communication we briefly review the historic aspects of immune based therapy for solid cancer, describe therapeutic strategies aimed at targeting lung cancer, and discuss limitations of current therapy and future directions of this field.

Respiratory Homeostasis and Exploitation of the Immune System for Lung Cancer Vaccines

Lung cancer is the leading cause of all cancer deaths in the US. The international scientific and clinical community has made significant advances toward understanding specific molecular mechanisms underlying lung carcinogenesis; however, despite these insights and advances in surgery and chemoradiotherapy, the prognosis for non-small-cell lung cancer (NSCLC) remains poor. Nonetheless, significant effort is being focused on advancing translational research evaluating the efficacy of novel targeted therapeutic strategies for lung cancer. Illustrative examples of this include antagonists of the epidermal growth factor receptor (EGFR), tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib, and a diverse assortment of anti-angiogenic compounds targeting growth factors and/or their receptors that regulate tumor-associated angiogenic programs. In addition, with the increased awareness of the significant role chronically activated leukocytes play as potentiators of solid-tumor development, the role of innate and adaptive immune cells as regulators of lung carcinogenesis is being examined. While some of these studies are examining how novel therapeutic strategies may enhance the efficacy of lung cancer vaccines, others are evaluating the intrinsic characteristics of the immune response to lung cancer in order to identify rate-limiting molecular and/or cellular programs to target with novel anticancer therapeutics. In this article, we explore important aspects of the immune system and its role in regulating normal respiratory homeostasis compared with the immune response accompanying development of lung cancer. These hallmarks are then discussed in the context of recent efforts to develop lung cancer vaccines, where we have highlighted important concepts that must be taken into consideration for future development of novel therapeutic strategies and clinical trials assessing their efficacy.

Phase III study of adjuvant vaccination with Bec2/bacille Calmette-Guerin in responding patients with limited-disease small-cell lung cancer (European Organisation for Research and Treatment of Cancer 08971-08971B; Silva Study)

PURPOSE

Bec2 is an anti-idiotypic antibody that mimics GD3, a ganglioside that is expressed on the surface of tumor cells and is of neuroectodermal origin. We assessed whether Bec2/bacille Calmette-Guerin (BCG) vaccination prolongs survival in patients with limited-disease small-cell lung cancer (SCLC) after a major response to chemotherapy and chest radiation.

PATIENTS AND METHODS

Patients were randomly assigned to receive five vaccinations of Bec2 (2.5 mg)/BCG vaccine or follow-up. Vaccination was given over a 10-week period. The sample size was targeted to detect an increase in median survival of 40% after random assignment, and stratification was by performance status, response, and institution. Quality of life was assessed by using the European Organisation for Research and Treatment of Cancer instrument. Humoral response was assessed in patients who received vaccination.

RESULTS

A total of 515 patients were randomly assigned. The primary toxicities of vaccination were transient skin ulcerations and mild flu-like symptoms. There was no improvement in survival, progression-free survival, or quality of life in the vaccination arm. Median survival from randomization was 16.4 and 14.3 months in the observation and vaccination arms (P = .28), respectively. Among vaccinated patients, a trend toward prolonged survival was observed in those (one third) who developed a humoral response (P = .085). Multivariate analysis showed a positive impact on survival by prior treatment with concomitant chemoradiotherapy, prophylactic cranial irradiation, female sex, low lactate dehydrogenase, and normal platelets.

CONCLUSION

Vaccination with Bec2/BCG has no impact on outcome of patients with limited-disease SCLC responding to combined-modality treatment. Vaccination strategies in SCLC may still be warranted using vaccines that produce a better immunologic response.

Differential effects of synthetic sphingosine derivatives on melanoma cell motility, growth, adhesion and invasion in vitro

Cancer cell surface glycosphingolipids are considered to play a critical role in tumor growth and metastasis. However, the implications of glycoconjugates in the control of cell motility, which is considered to be involved in tumor invasion, are not fully understood. In this study, the effects of a series of synthetic sphingosine derivatives, obtained by the chemical transformation of azidosphingosines, on directional migration of K1735-M2 melanoma cells grown on type I collagen-coated surfaces were investigated. Following the application of 60 microM (2R, 3S, 4E)-2, 3-epimino-4-octadecen-3-ol (S4) the migration rate was 94 +/- 10 microns/day, compared with 377 +/- 22 microns/day in the control experiment. Six other analogues were not as potent. S4 also considerably down-modulated melanoma single cell motility. Inhibition of motile activity was associated with changes in the actin filament organization as well as with changes in the number and distribution of vinculin plaques. Moreover, the compound reduced the attachment abilities of melanoma cells to basement membrane Matrigel. Tumor cell invasion, however, was less affected and proliferation remained unimpaired after treatment with S4. These data suggest at least one intracellular mode of action of this particular synthetic sphingosine derivative by modulation of cytoskeletal organization. Melanoma cell motility and growth may be controlled independently via glycosphingolipids.

Olfactory mucosa response in guinea pigs following intranasal instillation with Cryptococcus neoformans. A histological and immunocytochemical study

A central nervous system isolate from an acquired immunodeficiency syndrome (AIDS) patient of 10(3) Cryptococcus neoformans cells was instilled intranasally into guinea pigs. These were killed to evaluate the fate of the organisms and the response of the olfactory mucosa. Olfactory epithelium prevented the penetration of Cryptococcus neoformans and showed focal hyperplastic responses. The organisms, which manifested an affinity for the olfactory portion of the nasal cavities, were cleared from the olfactory space with no intervention from the immune system cells. By the end of the fifth week almost no organisms could be found and there was no histological evidence of dissemination. In contrast, destruction of the olfactory epithelium with zinc sulfate allowed the invasion of the subepithelial tissues, demonstrating the role of the olfactory mucosa in preventing infection with Cryptococcus neoformans through the nasal route. The results and the model described in this report may be useful in clarifying the pathogenic mechanisms of cryptococcosis and the non immune mediated host responses to Cryptococcus neoformans.

Re-assessment of acidic glycosphingolipids in small-cell-lung-cancer tissues and cell lines

The occurrence of tumor-associated glycosphingolipids (GSLs) has been documented in a variety of cancer tissues (Hakomori, 1984, 1985, 1989). In the case of small-cell lung cancer (SCLC), the monosialoganglioside IV2Fuc-II3NeuAc-Gg4Cer (Fuc-GM1; short notations of gangliosides are according to Svennerholm, 1963), first described from bovine liver (Wiegandt, 1973), was found to be a unique tumor-associated GSL (Nilsson et al., 1984). It is present in up to 90% of all SCLC cases as compared with 25% frequency in non-SCLC, and no occurrence in normal lung (Brezicka et al., 1989, 1992). Thus, Fuc-GM1 may represent a suitable target antigen for immunotherapy of SCLC, and successful experiments have been performed showing tumor-cell killing by monoclonal antibodies (MAbs) against Fuc-GM1, both in vitro and, in a mouse model, in vivo (Brezicka et al., 1991). However, an effective tumor vaccination in humans would require this antigen to be expressed by the primary tumor and also by all metastases. The co-expression of Fuc-GM1 has already been reported in primary tumors and in most but not all metastases of SCLC (Hanquing et al., 1986; Nilsson et al., 1986; Brezicka et al., 1989). In view of the significance this ganglioside may have for possible immunotherapeutical approaches to SCLC and of the difficulty in obtaining a sufficient number of samples for analysis, a re-assessment of Fuc-GM1 expression was made in SCLC primary tumors and their metastases, as well as in established SCLC cell lines. In addition, the possible presence of such gangliosides, that might help to explain the selective tetanus-toxin binding of SCLC cells (Critchley et al., 1986; Heymanns et al., 1989) was investigated. Finally, the typical occurrence of sulfatide in all SCLC tissues and cell lines could be established.

Aberrant expression of gangliosides in human renal cell carcinomas

Aberrant and elevated ganglioside expression has been observed in neoplasms, and has been shown to be an important marker of tumor progression. We therefore studied the gangliosides of renal cell carcinoma (RCC) by analyzing gangliosides from 18 RCC biopsies, 10 RCC lines and 5 normal kidney biopsies. A comparison of tumor with normal tissue revealed a significant difference in individual ganglioside expression in which the former consistently expressed eight major gangliosides, GM3, GM2, GM1, GD3, GD1A, GD2, GD1B and GT1B, according to the nomenclature of Svennerholm. There was a notable significant mean increase in the expression of GM2, GM1 and GD1A and a significant decrease in the expression of GD3 in tumor tissue compared with normal kidney tissue. Compared with tumor biopsy tissue, RCC cell lines showed a significant decrease in the expression of GM3, but a significant increase in GM2, GM1 and GD2. There was a marked increase in a pathway gangliosides (GM2, GM1, and GD1a) in RCC biopsies and cell lines compared with normal kidney. These studies indicating that RCC have markedly aberrant ganglioside expression similar to neural origin tumors may relate to the activation of a ganglioside pathway enzymes. Gangliosides expressed on RCC tumors may be important markers of tumor progression and target antigens for immunotherapy.

The expression of H-like blood group glycolipids in small cell carcinoma of the lung

Monoclonal antibody SM1 has been shown to be preferentially reactive with small cell carcinoma of the lung (SCCL) cell lines by fluorescent and radioimmunoassay membrane staining (1). Using solid phase indirect radioimmunoassay, the antigen is not detected in non-SCCL lung carcinomas histologically classified as squamous carcinoma, adenocarcinoma or large cell carcinoma, and other tumors, viz; pheochromocytoma, a mesoderm derived lymphoblastic leukemia cell line or in normal human brain, heart, liver, colon, endothelial tissues of the aorta and blood vessels, skin, omentum, muscle, lung parenchyma and is weakly reactive with bronchial mucosa, pancreas, and kidney. The membrane antigens detected by SM1 were isolated from small cell carcinoma of the lung (SCCL) cell line, SW2, using anion exchange chromatography and thin layer chromatography, and were further analysed by exoglycosidase and endoglycosidase treatments followed by chemical staining and immunostaining with SM1 and other antibodies. We show here that SM1 antibody reacts with a group of fucose-containing neutral glycolipids and gangliosides many of which are cross-reactive with antibodies to H antigens.

Epidermal growth factor receptor and lipid membrane components in human lung cancers

The binding of 125I-epidermal growth factor (EGF) to the plasma membranes of 54 samples of human lung tumors was determined. These included 34 squamous cell carcinomas and 20 adenocarcinomas. Twenty samples of histologically normal lung excised surgically along with the tumors were used as controls. Most of the plasma membranes showed an EGF receptor level higher than that of normal tissue. A moderate increase in the amount of 125I-EGF bound (2-5 fold) was observed in the majority of the tumors. Only a few cases (5-10% of the total) showed a large increase (> than 10 fold). The binding of 125I-EGF was compared with clinical stages and grades of differentiation. No correlation between the stage of the tumor and 125I-EGF binding was observed. However, the highest levels of EGF receptor (EGF-R) were found in poorly differentiated squamous cell carcinomas. The total amount and the distribution pattern of gangliosides and phospholipids were analyzed in individual tumors. A decrease in GD1b, GD1a and sphingomyelin and an increase in GM1 and GM3 was observed. No correlation was detected when tumors with the highest or lowest levels of gangliosides or phospholipids were compared with tumors exhibiting the highest binding of 125I-EGF.

Lipids in airway mucus of acute quadriplegic patients

Quadriplegic patients have difficulty in clearing lung mucus due to paralysis of muscles of respiration. In about 25% of these patients, excessive mucus in the airway necessitates tracheostomy, and in some patients it is fatal. In others there is spontaneous recovery. To determine if the excessive mucus results from secretion of abnormal mucus or from accumulation of normal mucus, we analyzed the lipids in mucus from eight quadriplegic patients. Lipids were separated from other constituents of the mucus by density gradient ultracentrifugation, extracted with chloroform-methanol (2:1), and examined by high-performance thin-layer chromatography (HPTLC). Cholesterol was the major neutral lipid; phosphatidylethanolamine, phosphatidylcholine, and sphingomyelin were the main phospholipids. Glycolipids were predominant, lactosylceramide (CDH) being the highest in amount. Two-dimensional HPTLC as well as high-performance lipid chromatography also revealed the presence of gangliosides: comparison with standards indicated the presence of GM1, GM2, GM3, and some unidentified gangliosides. In normal mucus, cholesterol is the predominant lipid; phospholipid is present in smaller amounts but glycolipids are not identified. Thus, results of our lipid analysis show that mucus from the quadriplegic patients is abnormal and similar to that in hypersecretory diseases such as chronic bronchitis and cystic fibrosis. Unlike these latter cases, hypersecretion in the quadriplegic has a rapid onset and, often, spontaneous recovery, suggesting that this is due to abnormal stimulation rather than an increase in the population of secretory cells.

Tetanus toxin as a marker for small-cell lung cancer cell lines

Tetanus toxin labeling of human lung cancer cell lines was investigated using direct and indirect immunofluorescence and immunohistochemical staining. Cells of characterized permanent cell lines, eight small-cell lung cancer (SCLC) cell lines of classic subtype, six SCLC cell lines of variant subtype and seven non-small-cell lung cancer (NSCLC) cell lines, were incubated with a saturating concentration of tetanus toxin. For staining, fluorescein-isothiocyanate-(FITC)-conjugated anti-(tetanus toxin) antibodies were used or a mouse monoclonal anti-(fragment C) antibody with subsequent binding of FITC-conjugated anti-(mouse Ig) antibody or peroxidase-anti-peroxidase complex. Only SCLC showed an intense fluorescence/immunoreactivity restricted to the cell membrane. Quantitative analysis of tetanus toxin labeling by flow cytometry revealed the percentage of positive cells to be between 35% and 95% in SCLC without obvious differences between the classic and variant subtypes of SCLC. In NSCLC the percentage of positive cells was lower than 10%. These results demonstrate that SCLC in contrast to NSCLC can be labeled with tetanus toxin, emphasizing the neuroendocrine properties of this tumor, and that tetanus toxin labeling may become a useful diagnostic marker for SCLC cells in cytology.

Antitumor activity via inhibition of glycosphingolipid biosynthesis

The production by cancer cells of glycolipids, perhaps derived partly from host glycolipids, may play essential roles in malignancy, tumor growth, immunity from host immunodefense, and metastasis. The glycolipids are derived from the primary glycolipid, glucosylceramide (GlcCer), which is formed enzymatically from ceramide and uridine diphosphoglucose (UDP-glu). Injection of an inhibitor of this enzyme into mice bearing intraperitoneal Ehrlich ascites tumor cells (EATC) resulted in complete cure of about 30% of the mice and marked prolongation of life in the remainder. Almost all of the surviving mice were immune to a second inoculation of EATC. Injection of GlcCer stimulated cancer cell growth about 50% but this was largely reversed by the inhibitor. This type of inhibitor may have wide application to cancer chemotherapy.