Inverse relation of E-cadherin and autocrine motility factor receptor expression as a prognostic factor in patients with bladder carcinomas

Down-regulation of E-cadherin, an intercellular adhesion molecule, and up-regulation of autocrine motility factor receptor (gp78) expressions have been shown to play a role in tumor cell invasion and metastasis. Monoclonal antibodies against E-cadherin and gp78 were used to stain serial snap-frozen sections of 12 normal bladder and 83 bladder carcinoma specimens (27 noninvasive, 53 invasive, and 3 metastases). In normal urothelium, E-cadherin is expressed while gp78 is not. Positive expression of E-cadherin and negative expression of gp78 were found to be associated with a low risk of clinical progression in the superficial bladder carcinoma patient group. While reduction in E-cadherin concomitantly with an increase in gp78 expression was associated with poor prognosis, 71% of the patients (n = 30) underwent rapid cancer progression, and 32% of the patients died of cancer-related disease at a median of 2 years after initial diagnosis. Thus, it is suggested that reduction of E-cadherin expression associated with an increase in the level of gp78 in bladder cancers may define a high risk group of patients. The dual use of these two antigens may improve early diagnosis of high risk bladder cancer patients and influence treatment decisions.     

Structural basis of calcium-induced E-cadherin rigidification and dimerization

The cadherins mediate cell adhesion and play a fundamental role in normal development. They participate in the maintenance of proper cell-cell contacts: for example, reduced levels of epithelial cadherin (E-cadherin) correlate with increased invasiveness in many human tumour cell types. The cadherins typically consist of five tandemly repeated extracellular domains, a single membrane-spanning segment and a cytoplasmic region. The N-terminal extracellular domains mediate cell-cell contact while the cytoplasmic region interacts with the cytoskeleton through the catenins. Cadherins depend on calcium for their function: removal of calcium abolishes adhesive activity, renders cadherins vulnerable to proteases (reviewed in ref. 4) and, in E-cadherin, induces a dramatic reversible conformational change in the entire extracellular region. We report here the X-ray crystal structure at 2.0 A resolution of the two N-terminal extracellular domains of E-cadherin in the presence of calcium. The structure reveals a two-fold symmetric dimer, each molecule of which binds a contiguous array of three bridged calcium ions. Not only do the bound calcium ions linearize and rigidify the molecule, they promote dimerization. Although the N-terminal domain of each molecule in the dimer is aligned in a parallel orientation, the interactions between them differ significantly from those found in the neural cadherin (N-cadherin) N-terminal domain (NCD1) structure. The E-cadherin dual-domain structure reported here defines the role played by calcium in the cadherin-mediated formation and maintenance of solid tissues.     

Internalin of Listeria monocytogenes with an intact leucine-rich repeat region is sufficient to promote internalization

Listeria monocytogenes can use two different surface proteins, internalin (InlA) and InlB, to invade mammalian cells. The exact role of these invasiveness factors in vivo remains to be determined. In cultured cells, InlA is necessary to promote Listeria entry into human epithelial cells, such as Caco-2 cells, whereas InlB is necessary to promote Listeria internalization in several other cell types, including hepatocytes, fibroblasts, and epithelioid cells, such as Vero, HeLa, CHO, or Hep-2 cells. We have recently reported that the InlA receptor on Caco-2 cells is the cell adhesion molecule E-cadherin and demonstrated that nonpermissive fibroblasts become permissive for internalin-mediated entry when transfected with the gene coding for LCAM, the chicken homolog of the human E-cadherin gene. In this study, we demonstrate for the first time that the internalin protein alone is sufficient to promote internalization into cells expressing its receptor. Indeed, internalin confers invasiveness to both Enterococcus faecalis and internalin-coated latex beads. As shown by transmission electron microscopy, these beads were phagocytosed via a "zipper" mechanism similar to that observed during the internalin-E-cadherin-mediated entry of Listeria. Moreover, a functional analysis of internalin demonstrates that its amino-terminal region, encompassing the leucine-rich repeat (LRR) region and the inter-repeat (IR) region, is necessary and sufficient to promote bacterial entry into cells expressing its receptor. Several lines of evidence suggest that the LRR region would interact directly with E-cadherin, whereas the IR region would be required for a proper folding of the LRR region.     

Altered cell adhesion activity by pervanadate due to the dissociation of alpha-catenin from the E-cadherin.catenin complex

Leukemia cells (K562) that grow as non-adhesive single cells and have no endogenous cadherin were transfected with an E-cadherin expression vector, and cell clones stably expressing E-cadherin on their surface were established. The expression of E-cadherin induced the up-regulation of catenins, and E-cadherin became associated with catenins. The transfected cells grew as floating aggregates. Cell aggregation was Ca2+-dependent and was inhibited by E-cadherin antibodies. The aggregates dissociated into single cells on the addition of pervanadate. Pervanadate caused a dramatic augmentation of the phosphorylation of E-cadherin, beta-catenin, and gamma-catenin (plakoglobin), but alpha-catenin was not detectably phosphorylated. After pervanadate treatment, beta-catenin and gamma-catenin migrated more slowly on gel electrophoresis, suggesting changes in their conformations due to eventual changes in their phosphorylation levels. In the treated cells, a significant amount of alpha-catenin was dissociated from the E-cadherin.catenin complex. Aggregates of cells expressing an E-cadherin chimeric molecule covalently linked with alpha-catenin were not dissociated on pervanadate treatment, supporting the idea that the dissociation of alpha-catenin from the complex underlies the observed E-cadherin dysfunction.     

Expression of c-ets-1 mRNA is associated with an invasive, EMT-derived phenotype in breast carcinoma cell lines

We have previously observed in vitro that some stromal proteinases (MMP-2, MT1-MMP) were expressed or activated by invasive carcinoma cell lines exhibiting mesenchymal features, presumably acquired through an epithelial to mesenchymal transition (EMT). To examine the potential contribution of c-ets-1 to this phenotype, we have compared here the expression of c-ets-1 with invasiveness in vitro and expression of vimentin, E-cadherin, uPA, MMP-1 and MMP-3 in a panel of human breast cancer cell lines. Our results clearly demonstrate an association between c-ets-1 expression and the invasive, EMT-derived phenotype, which is typified by the expression of vimentin and the lack of E-cadherin. While absent from the two non-invasive, vimentin-negative cell lines, c-ets-1 was abundantly expressed in all the four vimentin-positive lines. However, we could not find a clear quantitative or qualitative relationship between the expression of c-ets-1 and the three proteinases known to be regulated by c-ets-1, except that when they were expressed, it was only in the invasive c-ets-1-positive lines. UPA mRNAs were found in three of the four vimentin-positive lines, MMP-1 in two of the four, and MMP-3 could not be detected in any of the cell lines. Intriguingly, MDA-MB-435 cells, which exhibit the highest metastatic potential of these cell lines in nude mice, expressed vimentin and c-ets-1, but lacked expression of these three proteinases, at least under the culture conditions employed. Taken together, our results show that c-ets-1 expression is associated with an invasive, EMT-derived phenotype in breast cancer cells, although it is apparently not sufficient to ensure the expression of uPA, MMP-1 or MMP-3, in the vimentin-positive cells. Such proteases regulation is undoubtedly qualified by the cellular context. This study therefore advances our understanding of the molecular regulation of invasiveness in EMT-associated carcinoma progression, and suggests that c-ets-1 may contribute to the invasive phenotype in carcinoma cells.     

Antileukotrienes and asthma: alternative or adjunct to inhaled steroids?

The cadherins are a family of a calcium-dependent cell adhesion molecules that are regulated both spatially and temporally during development. Epithelial cadherin (E-cadherin) is present in the epithelial cells in both the embryo and yolk sac during organogenesis. In many studies, the presence of E-cadherin was analyzed during normal and disturbed craniofacial development with respect to palate and tooth formation. E-cadherin was present in epithelia of both ectodermal and endodermal origin. The expression level of E-cadherin increased with age and differentiation. The expression pattern of E-cadherin implies that this molecule has a role during normal development of the epithelia of the cranio-facial complex. Morphogenesis and cell differentiation in the developing tooth are controlled by a series of reciprocal interactions between the epithelial and mesenchymal tissues. The exact molecular mechanisms operating in these interactions are unknown at present, but both structural components of the extracellular matrix (ECM) and diffusible growth factors have been suggested to be involved. In this review article we summarize our findings on the distribution patterns of three ECM molecules and two cell surface receptors during tooth morphogenesis through bud, cap, and bell stages of development. The examined molecules include fibronectina and tenascin, which all represent components of the mesenchymal ECM, the cell surface proteoglycan, syndecan, which functions as a receptor for interstitial matrix. Based on the observed changes in distribution patterns and on experimental evidence, roles are suggested for these molecules in epithelial-mesenchymal interactions during tooth development. C-Cam is a cell surface glycoprotein that is involved in cell adhesion and may play a role in histogenesis and organogenesis. It is a member of the carcinoembryonic antigen (CEA) gene family, which is a subfamily of the immunoglobulin gene superfamily. The presence of C-CAM in all proliferating craniofacial epithelia indicates that this molecule may play an important role in development.     

Prediction of occult neck metastases in laryngeal carcinoma: role of proliferating cell nuclear antigen, MIB-1, and E-cadherin immunohistochemical determination

The aim of this study is to investigate the predictive value of proliferative activity assessment and E-cadherin expression by means of immunohistochemistry in identifying patients with laryngeal squamous cell carcinoma at a high risk for occult node metastasis. Thirty consecutive patients treated for laryngeal carcinoma with false clinically negative nodes (occult metastases, pN+) between the years 1980 and 1990 were selected for this study. A group of 30 cases with negative cervical lymph nodes (pN-) having a similar anatomic site and tumor size distribution was used as control. In each case, several histological parameters, including grade, pattern of invasion, number of mitosis (x10 high-power field), tumor inflammatory infiltrate, and tumor sclerosis, were assessed. Proliferative activity was determined using immunohistochemical staining for proliferating cell nuclear antigen (PCNA) and MIB-1. Other putative prognostic factors investigated at the immunohistochemical level were the cell adhesion molecule E-cadherin and two oncoproteins, p53 and c-erbB-2. In pN+ cases, the expression of PCNA and MIB-1 was significantly higher than in the pN- group. Moreover, a significant loss of E-cadherin expression was observed in carcinomas with occult metastases. No differences in p53 and c-erbB-2 oncoproteins were found between pN+ and pN- cases. Among the other pathological parameters examined, only histological grade was significantly associated with the presence of occult metastases, but on multivariate analysis, this relationship was lost. We conclude that PCNA, MIB-1, and E-cadherin are independent predictors of occult nodal disease in laryngeal squamous cell carcinoma, and their immunohistochemical determination could be useful in identifying patients with clinically negative lymph nodes who are at considerable risk for occult metastases and who may benefit from elective neck dissection.     

Reduced E-cadherin expression correlates with increased invasiveness in colorectal carcinoma cell lines

A reduction in cell adhesiveness and cell invasion are essential steps in tumour progression to metastasis. In the present study two out of seven colorectal carcinoma cell lines exhibited reduced expression of the cell-cell adhesion molecule E-cadherin as assessed by immunofluorescence. The same two cell lines were invasive in the collagen gel and membrane invasion culture system invasion assays. Addition of anti-E-cadherin antibody to a non-invasive carcinoma cell line caused the cells to assume a dissociated morphology on plastic and to become invasive in collagen gels. This demonstrates a causal role for E-cadherin in the maintenance of intercellular adhesion and the suppression of tumour cell invasion and possibly metastasis in colorectal tumour cells.     

E-Cadherin-dependent growth suppression is mediated by the cyclin-dependent kinase inhibitor p27(KIP1)

Recent studies have demonstrated the importance of E-cadherin, a homophilic cell-cell adhesion molecule, in contact inhibition of growth of normal epithelial cells. Many tumor cells also maintain strong intercellular adhesion, and are growth-inhibited by cell- cell contact, especially when grown in three-dimensional culture. To determine if E-cadherin could mediate contact-dependent growth inhibition of nonadherent EMT/6 mouse mammary carcinoma cells that lack E-cadherin, we transfected these cells with an exogenous E-cadherin expression vector. E-cadherin expression in EMT/6 cells resulted in tighter adhesion of multicellular spheroids and a reduced proliferative fraction in three-dimensional culture. In addition to increased cell-cell adhesion, E-cadherin expression also resulted in dephosphorylation of the retinoblastoma protein, an increase in the level of the cyclin-dependent kinase inhibitor p27(kip1) and a late reduction in cyclin D1 protein. Tightly adherent spheroids also showed increased levels of p27 bound to the cyclin E-cdk2 complex, and a reduction in cyclin E-cdk2 activity. Exposure to E-cadherin-neutralizing antibodies in three-dimensional culture simultaneously prevented adhesion and stimulated proliferation of E-cadherin transfectants as well as a panel of human colon, breast, and lung carcinoma cell lines that express functional E-cadherin. To test the importance of p27 in E-cadherin-dependent growth inhibition, we engineered E-cadherin-positive cells to express inducible p27. By forcing expression of p27 levels similar to those observed in aggregated cells, the stimulatory effect of E-cadherin-neutralizing antibodies on proliferation could be inhibited. This study demonstrates that E-cadherin, classically described as an invasion suppressor, is also a major growth suppressor, and its ability to inhibit proliferation involves upregulation of the cyclin-dependent kinase inhibitor p27.     

Effects of 1,25-dihydroxyvitamin D3 on tumor cell invasion to the extracellular matrix in human fibrosarcoma HT1080 cells and its correlation with laminin

We investigated the role of the active form of vitamin D, 1,25-dihydroxyvitamin D3[1,25(OH)2D3], in promoting tumor cell invasiveness through the extracellular matrix, and showed that 1,25(OH)2D3-induced reduction of laminin production by the cells was correlated with the inhibitory effect of the hormone on tumor cell invasiveness. 1,25(OH)2D3 significantly inhibited invasiveness through the matrix, type IV collagenolytic and migratory activity, but not cell attachment to the matrix in human fibrosarcoma HT1080 cells. The 1,25(OH)2D3-induced inhibition showed the same dose dependency and magnitude for invasiveness as for the effects on type IV collagenolysis and cell migration. 1,25(OH)2D3 inhibited laminin production from the cells in a dose-dependent manner. The inhibitory effects of 1,25(OH)2D3 on the invasiveness, type IV collagenolysis and cell migration appeared to parallel the hormone-induced reduction of laminin production. Antilaminin monoclonal antibody, blocking the activity of laminin in the culture medium, inhibited HT1080 cell invasiveness. In the presence of exogenous laminin, 1,25(OH)2D3-induced inhibition of invasion was not observed. These findings suggest that 1,25(OH)2D3 acts on HT1080 cells, inhibiting the expression of laminin from the cells, and that the reduced laminin expression leads to the inhibition in the type IV collagenolytic and migratory activity of the cells, and consequently, to the inhibition of invasiveness through the extracellular matrix.     

Inhibition of nuclear factor kappa B attenuates proinflammatory cytokine and inducible nitric-oxide synthase expression in postischemic myocardium

Nitric oxide (NO), a potent biological mediator, plays a key role in physiological as well as pathological processes, including inflammation and cancer. The role of NO in tumor biology remains incompletely understood. While a few reports indicate that the presence of NO in tumor cells or their microenvironment is detrimental to tumor cell survival and consequently their metastatic ability, a large body of clinical and experimental data suggest a promoting role of NO in tumor progression and metastasis. We suggest that tumor cells capable of very high levels of NO production die in vivo, and those producing or exposed to lower levels of NO, or capable of resisting NO-mediated injury undergo a clonal selection because of their survival advantage; they also utilize certain NO-mediated mechanisms for promotion of growth, invasion and metastasis. The possible mechanism(s) are: (a) a stimulatory effect on tumor cell invasiveness, (b) a promotion of tumor angiogenesis and blood flow in the tumor neovasculature, and (c) a suppression of host anti-tumor defense. In this review, we discuss these mechanisms on the basis of data derived from experimental models, in particular, a mouse mammary tumor model in which the expression of eNOS by tumor cells is positively correlated with invasive and metastatic abilities. Tumor-derived NO was shown to promote tumor cell invasiveness and angiogenesis. The invasion-stimulating effects of NO were due to an upregulation of matrix metalloproteases and a downregulation of their natural inhibitors. Treatment of tumor-bearing mice with NO-blocking agents reduced the growth and vascularity of primary tumors and their spontaneous metastases. We propose that selected NO-blocking drugs may be useful in treating certain human cancers either as single agents or as a part of combination therapies.     

The cell adhesion molecule E-cadherin is widely expressed in human atherosclerotic lesions

OBJECTIVE: Various cell adhesion molecules are expressed in atherogenesis and the significance of their involvement in atherosclerotic lesion formation is well appreciated. In the present work, we examined whether the Ca(2+)-dependent cell adhesion molecule E-cadherin is also involved in atherogenesis. METHODS: Specimens of carotid artery and aorta were obtained at operation. Expression of E-cadherin was studied by an immunohistochemical method. The nature of E-cadherin-expressing cells was examined by comparative analysis of consecutive sections and by a double immunostaining procedure. An immunohistochemical approach was also applied to examine how the accumulation of oxidised low density lipoproteins (LDL) by intimal cells is associated with E-cadherin expression. RESULTS: No E-cadherin+ cells were found in normal non-atherosclerotic intima but E-cadherin+ cells were present in 96% of the atherosclerotic lesions. In atherosclerotic intima, E-cadherin was expressed by intimal cells showing varying degrees of transformation into foam cells. These E-cadherin+ cells also contained oxidised LDL in their cytoplasm. Differing numbers of CD68+ foam cells (15% to 60%) expressed E-cadherin but all the CD68+ macrophages without signs of transformation into foam cells were negative for E-cadherin. Neither smooth muscle cells nor foam cells of smooth muscle cell origin (smooth muscle alpha-actin+) were found to be positive for E-cadherin. T-cells (CD3+) and endothelial cells (von Willebrand factor+) were also negative for E-cadherin. Only a few vascular dendritic cells (S-100+) expressed E-cadherin and their expression was weak. We also found that a large proportion (40% to 85%) of E-cadherin+ cells did not stain with any cell-type specific markers. CONCLUSIONS: The finding that E-cadherin is expressed in atherosclerotic lesions expands our knowledge of cell adhesion molecules involved in atherogenesis. That E-cadherin is expressed in intimal cells transforming into foam cells suggests that lipid accumulation might be associated with the alteration and reorganisation of cell-to-cell interactions in atherogenesis. The present observations might assist in understanding the mechanisms associated with intracellular lipid accumulation.     

A method for production and determination of histamine releasing activity from human peripheral blood mononuclear cells

Cell-cell adhesion mediated by E-cadherin is often lost or disturbed in human carcinomas. For regular adhesive function, E-cadherin has to form complexes with peripheral cytoplasmic catenins which are multifunctional proteins that are also involved in signal transduction and growth regulation. We have analyzed the expression levels of the genes encoding alpha-catenin, beta-catenin and plakoglobin in correlation to the E-cadherin expression levels in cell lines derived from human cervical carcinomas. Reduced mRNA and protein levels were detected for plakoglobin, whereas alpha- and beta-catenin showed only reduced protein (but not mRNA) levels. The alterations in catenin gene expression were often associated with absent or reduced E-cadherin. The findings indicate that a reduction of catenin gene expression may contribute to the development of cervical carcinomas.     

Influence of adhesion molecule expression by human brain microvessel endothelium on cancer cell adhesion

Cultures of endothelial (En) cells derived from human brain microvessels were established in order to characterize adhesion molecule expression and to assay the adhesion properties of neoplastic cell lines to monolayers of En cells. Low constitutive expression of beta1 integrin (CD29), and ICAM-2 (CD102) was detected on human brain microvessel En cells. The beta1 chain of the VLA integrin family, ICAM-1, E-selectin (CD62E) and VCAM-1 (CD106) but not ICAM-2 and PECAM-1 (CD31) expression was upregulated by IL1-alpha, and TNF-alpha proinflammatory cytokines. High expression of PECAM-1 was found on non-activated human brain EN cells. In order to study the potential role of adhesion molecules in neoplastic cell adhesion two tumor cell lines were chosen. Adhesion of a cell line (DU145) derived from a cerebral metastasis of prostate carcinoma to human brain microvessel En cell monolayers was less pronounced compared to adhesion of a primary prostate carcinoma cell line (ND1). Adhesion of cerebral metastatic neoplastic cell line (DU145) was not significantly influenced by incubation of endothelial cells with different proinflammatory cytokines. The adhesion capability of primary prostate carcinoma line (NDI) was significantly upregulated by TNF-alpha proinflammatory cytokine. Furthermore, the adhesion of ND1 was partly inhibited using anti-E-selectin and VCAM-1 monoclonal antibodies. There was no significant effect of anti-adhesion antibodies on the adhesion characteristics of the cerebral metastatic (DU145) cell line. Our data demonstrate that different mechanisms are involved in the adhesion of neoplastic cells to cerebral En cells and turn our attention to the importance of adhesion molecule expression in the formation of metastases.     

Influence of glycosylphosphatidylinositol-linked H-2Dd molecules on target cell protection and natural killer cell specificity in transgenic mice

The expression of certain major histocompatibility complex (MHC) class I ligands on target cells is one important determinate of their susceptibility to lysis by natural killer (NK) cells. NK cells express receptor molecules that bind to MHC class I. Upon binding to their MHC class I ligand, the NK cell is presumed to receive a signal through its receptor that inhibits lysis. It is unclear what role the MHC class I molecules of the effector and target cells play in signaling to the NK cell. We have investigated the role of the cytoplasmic and transmembrane domains of MHC class I molecules by producing a glycosylphosphatidylinositol (GPI)-linked H-2Dd molecule. The GPI-linked H-2Dd molecule is recognized by H-2Dd-specific antibodies and cytotoxic T lymphocytes. Expression of the GPI-linked H-2Dd molecule on H-2b tumor cells resulted in protection of the tumor cells after transplantation into D8 mice (H-2b, H-2Dd) from rejection by NK cells. In addition, NK cells from mice expressing the GPI-linked H-2Dd molecule as a transgene were able to kill nontransgenic H-2b lymphoblast target cells. The GPI-linked MHC class I molecule was able to alter NK cell specificity at the target and effector cell levels. Thus, the expression of the cytoplasmic and transmembrane domains of MHC class I molecules are not necessary for protection and alteration of NK cell specificity.     

The effects of IL-6 on cell adhesion and e-cadherin expression in breast cancer

Interleukin 6 (IL-6) is a pleiotropic inflammatory cytokine and its role in cancer is not yet clear. The effects of IL-6 on four breast cancer cell lines and normal mammary epithelium, cultured from milk were tested. Four different patterns of response to IL-6 were found depending on the differentiation status of the cells. In normal mammary epithelial cultures, the effects of IL-6 were mainly growth inhibitory, whereas in MCF-7, IL-6 had growth inhibitory and anti-adhesive effects. In T-47D and ZR-75-1 the anti-adhesive effects were prominent although the growth inhibitory effects were not. These anti-adhesive effects were associated with epithelioid to fibroblastoid morphological changes and a local decrease in E-cadherin expression. In the highly invasive cell line MDA-MB-231, which does not express E-cadherin, no effects of IL-6 were seen. IL-6 levels in the serum of 60 breast cancer patients were found to be increased in 27% (16/60) compared to 2% (1/50) in a control group. Furthermore, it was found that altered E-cadherin expression was seen in 69% of the primary tumours, although no significant association was found between raised serum IL-6 levels and altered E-cadherin expression. Finally IL-6 serum levels did not effect the survival of breast cancer patients. The authors therefore implicate IL-6 as a possible factor important in breast cancer progression and metastasis formation, although the clinical significance of this cytokine in breast cancer patients could not be established.     

Prevention of breast cancer in the rat with 9-cis-retinoic acid as a single agent and in combination with tamoxifen

We show that 9-cis-retinoic acid (9cRA) is a potent inhibitor of mammary carcinogenesis induced by N-nitroso-N-methylurea in Sprague-Dawley rats. Rats were first treated with a single dose of N-nitroso-N-methylurea (50 mg/kg body weight) and then fed non-toxic levels of 9cRA (120 or 60 mg/kg of diet). 9cRA was highly effective in reducing tumor incidence, average number of tumors per rat, and average tumor burden, as well as extending tumor latency. The combination of 9cRA with low levels of tamoxifen (TAM; fed at either 1.0 or 0.5 mg/kg of diet) was particularly effective; addition of 9cRA to a TAM regimen doubled the number of animals that were tumor-free at autopsy and significantly diminished tumor number and tumor burden. For suppression of carcinogenesis in vivo, 9cRA was much more potent than all-trans-retinoic acid, both as a single agent or in combination with TAM, although both retinoids had equivalent inhibitory effects on DNA synthesis in cultured human breast cancer cell lines. Both 9cRA and all-trans-retinoic acid induce the expression of the adhesion molecule, E-cadherin, in the SK-BR-3 cell line. We suggest that clinical evaluation of the combination of 9cRA and TAM, either for chemoprevention or for adjuvant therapy, should be considered.     

Expression of costimulatory molecules, B7-1 and B7-2 on human gastric carcinoma

Costimulation of T cells via B7-1 and B7-2 molecules on a tumor has been shown to be important for eliciting cell-mediated antitumor immunity. We studied the surface expression of B7-1 and B7-2 in 24 cases of gastric carcinoma from the primary locus, 20 cases of metastatic carcinoma from malignant ascites, 20 cases of benign gastric mucosa and 7 gastric carcinoma cell lines by two-color flow cytometry with mAb CD80 and CD86. The B7-1 and B7-2 molecules were expressed by 6 cell lines, and 1 cell line showed the predominant expression of B7-2 but not B7-1. Almost all patients with primary gastric carcinoma and benign gastric mucosa showed high levels of expression of the B7-1 and B7-2, revealing approximately 40%-60% positive cells. However, the percentage of B7-1-positive cells of poorly differentiated primary carcinomas was significantly lower than that of well-differentiated carcinoma and normal mucosa (P < 0.01). Furthermore, all of the metastatic carcinoma cells revealed consistently very low or undetectable levels of expression of the B7-1 molecule, only 8% (mean) of cells being positive, despite showing higher levels of B7-2 expression. Thus, it seems likely that decreased or deleted expression of B7-1 correlates with the grade of tumor differentiation, tumor progression and metastasis. These results suggest that the B7-1 molecule on the gastric carcinoma bearing CD80+CD86+ is abrogated during tumor invasion and/or metastasis, and the tumor finally acquires the CD80-CD86+ phenotype. Consequently, inadequate B7-1 costimulation may contribute to the escape of tumors from destruction by the host's immune system.