Regulation by retinoic acid of ICAM-1 expression on human tumor cell lines

Gene regulation of intracellular adhesion molecule-1 (ICAM-1): A molecule with multiple functions

Intracellular adhesion molecule 1 (ICAM-1) is one of the most extensively studied inducible cell adhesion molecules which is responsible for several immune functions like T cell activation, extravasation, inflammation, etc. The molecule is constitutively expressed over the cell surface and is regulated up / down in response to inflammatory mediators like cellular stress, proinflammatory cytokines, viral infection. These stimuli modulate the expression of ICAM-1 primarily through regulating the ICAM-1 gene transcription. On account of the presence of various binding sites for NF-κB, AP-1, SP-1, and many other transcription factors, the architecture of the ICAM-1 promoter become complex. Transcription factors in union with other transcription factors, coactivators, and suppressors promote their assembly in a stereospecific manner on ICAM-1 promoter which mediates ICAM-1 regulation in response to different stimuli. Along with transcriptional regulation, epigenetic modifications also play a pivotal role in controlling ICAM-1 expression on different cell types. In this review, we summarize the regulation of ICAM-1 expression both at the transcriptional as well as post-transcriptional level with an emphasis on transcription factors and signaling pathways involved.

Bottom up proteomics reveals novel differentiation proteins in neuroblastoma cells treated with 13-cis retinoic acid

Neuroblastoma, a cancer of the sympathetic nervous system, is the second most common pediatric cancer. A unique feature of neuroblastoma is remission in some patients due to spontaneous differentiation of metastatic tumors. 13-cis retinoic acid (13-cis RA) is currently used in the clinic to treat neuroblastoma due to its differentiation inducing effects. In this study, we used shotgun proteomics to identify proteins affected by 13-cis RA treatment in neuroblastoma SK-N-SH cells. Our results showed that 13-cis RA reduced proteins involved in extracellular matrix synthesis and organization and increased proteins involved in cell adhesion and neurofilament formation. These changes indicate that 13-cis RA induces tumor cell differentiation by decreasing extracellular matrix rigidity and increasing neurite overgrowth. Differentially-affected proteins identified in this study may be novel biomarkers of drug efficacy in the treatment of neuroblastoma. SIGNIFICANCE: As neuroblastoma can spontaneously differentiate, determining which proteins are involved in differentiation can guide development of novel treatments. 13-cis retinoic acid is currently used in the clinic as a differentiation inducer. Here we have established a proteome map of SK-N-SH cells treated with 13-cis retinoic acid. Bioinformatic analysis revealed the involvement of development, differentiation, extracellular matrix assembly, collagen biosynthesis, and neurofilament bundle association. This proteome map provides information as to which proteins are important for differentiation and identifies networks that can be targeted by drugs to treat neuroblastoma [1].

Decitabine facilitates immune recognition of sarcoma cells by upregulating CT antigens, MHC molecules, and ICAM-1

Rhabdomyosarcoma, osteosarcoma, and Ewing's sarcoma are the most common types of sarcoma in children. Despite standard therapy, nearly one third of the patients with Ewing's sarcoma relapse, and there are limited options with curative potential. Immunotherapy is a promising approach as it can target tumor-specific antigens that are specifically expressed on tumors while sparing non-malignant cells. We have demonstrated that a demethylating chemotherapeutic drug, 5-aza-2'-deoxycytidine (decitabine, DAC) can upregulate the expression of cancer-testis (CT) antigens, MHC molecules, and intracellular cell adhesion molecule-1 on pediatric sarcoma cell lines, resulting in enhanced killing of tumor cells by CT antigen-specific cytotoxic T lymphocytes derived from pediatric sarcoma patients. A significant increase in the mRNA expression levels of MAGE-A1 and MAGE-A3 were found in 70 %, and NY-ESO-1 in 80 % of the sarcoma lines following exposure to pharmacological levels of DAC. The high expression levels of MAGE-A1, MAGE-A3, and NY-ESO-1 were sustained in sarcoma lines and primary tumor lines over 30 days after the cessation of DAC. Furthermore, DAC treatment induced upregulation of MAGE-A1, MAGE-A3, or NY-ESO-1 protein expression in seven of nine lines studied. These studies show that demethylating chemotherapy could be combined with CT antigen-directed immunotherapy for treating pediatric sarcoma.

About the cutaneous targets of bexarotene in CTCL patients

There are several approved therapies for cutaneous T-cell lymphoma (CTCL). The retinoids are one of the major biologic response modifiers used in CTCL, producing good response rates but few complete responses. Bexarotene has been demonstrated to act on malignant T-cells by inducing their apoptosis, but nothing is known about its role on keratinocytes and Langerhans cells. Immunohistochemical analysis using CD1a, HLA-DR, ICAM-1 (activation markers), CD95 and CD40 (apoptosis markers) was conducted on frozen sections of bexarotene-exposed cutaneous explants and skin biopsy specimens from patients treated with bexarotene. None of the studied markers was significantly modulated both on cutaneous explants and on skin biopsy specimens after treatment with bexarotene, compared to controls. Langerhans cells and keratinocytes do not appear to play a central role in the therapeutic control of CTCL by bexarotene therapy. The main bexarotene's target thus remains T-cells by inducing their apoptosis, a mechanism that is different from the other retinoids used in CTCL.

13-cis-retinoic acid in the treatment of recurrent glioblastoma multiforme

Basic science and clinical investigations have demonstrated that 13-cis-retinoic acid (cRA) has activity against malignant gliomas. To assess its effectiveness in the setting of recurrent glioblastoma multiforme (GBM), we performed a retrospective analysis of the medical records and neuroimaging results of patients with recurrent GBM who were treated with cRA. The toxicity profile of cRA, response, and effect on progression-free survival from initiation of treatment were end points of our analysis. Eighty-two of 85 patients with a median age of 51 years received at least 1 full cycle of cRA. At the initiation of cRA treatment, the median Karnofsky performance score was 80. All patients had failed conventional radiotherapy. Seven patients were chemonaïve, whereas 75 patients had received some form of chemotherapy. Radiographic partial responses, minor responses, and stable disease were seen in 4%, 8%, and 34% of patients, respectively. Two patients were not assessable. Progression-free survival and overall survival after initiation of cRA were 10.0 and 24.6 weeks, respectively. Six-month progression-free survival was 19% for the entire group. Grade 3 or 4 toxicity developed in 14 patients (16%), one of whom developed pancreatitis and died. The results of this study demonstrate only modest efficacy for cRA therapy in this cohort of heavily pretreated patients with recurrent GBM. This data supports the use of cRA in such patients, but its further evaluation in larger, prospective, controlled studies with or without other noncytotoxic and cytotoxic agents may be warranted.

Antidisialoganglioside/granulocyte macrophage-colony-stimulating factor fusion protein facilitates neutrophil antibody-dependent cellular cytotoxicity and depends on FcgammaRII (CD32) and Mac-1 (CD11b/CD18) for enhanced effector cell adhesion and azurophil granule exocytosis

Polymorphonuclear leukocytes (PMNs) mediate antibody-dependent cellular cytotoxicity (ADCC), which is increased by the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF). We sought to determine whether PMN ADCC also would be increased by the addition of an antibody/GM-CSF fusion protein and whether this would be associated with the up-regulation and activation of Mac-1 (CD11b/CD18) and with azurophil granule exocytosis. ADCC against LA-N-1 human neuroblastoma cells was evaluated with 4-hour calcein acetoxymethyl ester (calcein-AM) microcytotoxicity assay, electron microscopy, and multi-parameter flow cytometry. With the calcein-AM assay, LA-N-1 cell survival was 10%, 55%, and 75% when PMN ADCC was mediated by the antidisialoganglioside (anti-GD2) immunocytokine hu14.18/GM-CSF, by monoclonal antibody (mAb) hu14.18 mixed with GM-CSF, and by hu14.18 alone. Function-blocking mAbs demonstrated that FcgammaRII and FcgammaRIII were required for ADCC with hu14.18 alone or mixed with GM-CSF, but that only FcgammaRII was required for ADCC with hu14.18/GM-CSF. ADCC mediated by hu14.18 and hu14.18/GM-CSF was Mac-1 dependent. Electron microscopy demonstrated the greatest PMN adhesion, spreading, and lysis of targets with hu14.18/GM-CSF. Monoclonal antibodies blocking Mac-1 function allowed the tethering of PMN to targets with hu14.18/GM-CSF but prevented adhesion, spreading, and cytolysis. Flow cytometry showed that hu14.18 with or without GM-CSF and hu14.18/GM-CSF all mediated Mac-1-dependent PMN-target cell conjugate formation but that GM-CSF was required for the highest expression and activation of Mac-1, as evidenced by the mAb24-defined beta(2)-integrin activation epitope. Hu14.18/GM-CSF induced the highest sustained azurophil granule exocytosis, almost exclusively in PMNs with activated Mac-1. Thus, hu14.18/GM-CSF facilitates PMN ADCC against neuroblastoma cells associated with FcgammaRII and Mac-1-dependent enhanced adhesion and degranulation.

RARbeta involvement in enhancement of lung tumor cell immunogenicity revealed by array analysis

The retinoid receptors (RARs and RXRs) are mediators of the multiple effects of retinoic acid. Of these, the retinoic acid receptor beta2 (RARbeta2) has frequently been shown to be the principal mediator of the growth and tumor suppressive effects of retinoic acid; this gene is inactivated in many epithelial tumors and their derived cell lines. We have searched for genes that are regulated by this isoform and are potentially involved in tumor suppression. Using the Atlas human cDNA array I, we identified 27 genes (not counting RARbeta itself) that are regulated, directly or indirectly, by RARbeta2 when it is transfected into Calu-1, a lung tumor-derived line that does not normally express RARbeta. Several of the affected genes code for proteins whose functions would augment the process of apoptosis and/or the host's immune response. The latter group included ICAM-1 and MHC class I heavy chain, whose protein products play particularly important roles in the mounting of an effective anti-tumor response. We then confirmed by flow cytometry that the observed increases in message levels were reflected in increased cell surface protein levels for ICAM-1 and MHC class I in RARbeta2 transfectants of two RARbeta-deficient lines, Calu-1 and the epidermoid lung cancer-derived line SK-MES. Finally, we showed that RARbeta2 transfection of Calu-1 cells enhanced the heterologous CTL response in both the induction and the effector phases by up to threefold. These results support the hypothesis that down-regulation of these genes (and possibly others) in RARbeta-deficient tumor cells contributes to immune system evasion, and suggest a novel therapeutic approach for this disease.

Retinoic acid redifferentiation therapy for thyroid cancer

For the treatment of differentiated thyroid cancer, surgery, radioiodide therapy, and thyrotropin-suppressive thyroxine application represent established therapeutic measures of proven efficiency, affording a good prognosis for this disease. However, in up to 30% of the cases, dedifferentiation is observed, giving rise to tumors that are refractory to conventional treatment. Eventually, this may lead to the most malignant human tumor, anaplastic thyroid carcinoma, with a life expectancy of only a few months after diagnosis. Among novel approaches for the treatment of dedifferentiated thyroid carcinomas, retinoic acid redifferentiation therapy was evaluated in several in vitro and in vivo studies. Cell culture experiments in thyroid carcinoma lines show that RA treatment affects thyroid specific functions (type I 5'-deiodinase, sodium/iodide-symporter), cell-cell or cell-matrix interaction (intercellular adhesion molecule-1, E-cadherin), differentiation markers (alkaline phosphatase, CD97), growth, and tumorigenicity. The observed changes, which involve multiple parameters that characterize a mature, functional thyrocyte, may be interpreted as partial redifferentiation. In clinical pilot studies, about 40% of the patients responded to RA application with an increased radioiodide uptake. In an evaluation of 20 RA-treated patients with well-documented data sets, 8 exhibited a decrease (4) or stabilization (4) in tumor size and/or in serum thyroglobulin levels in addition to enhanced radioiodide transport. This indicates that these patients with a long history of unresponsiveness to other treatment may have experienced an actual therapeutic benefit. These data suggest that RA redifferentiation therapy, considering especially its comparatively mild side effects, may soon represent an alternative therapeutic approach to otherwise untreatable thyroid tumors.

The role of human melanoma cell ICAM-1 expression on lymphokine activated killer cell-mediated lysis, and the effect of retinoic acid

Intercellular adhesion molecule (ICAM-1) exists as a membrane-associated form (mICAM-1) on the surface of tumour cells as well as a soluble form (sICAM-1). This study analyses the ability of all-trans retinoic acid (RA) to alter both sICAM and mICAM-1 expression in C8161 and Hs294T human melanoma cell lines and investigates the involvement of ICAM-1 in the interaction between tumour and lymphokine-activated killer (LAK) cells using the Cr-51 release assay. Our data showed that 4-day pretreatment of the tumour cells with 10(-7) M RA and 10(-6) M RA induced an increase in lysis of both cell lines and also increased mICAM-1 expression without having any effect on sICAM-1 levels. Addition of blocking ICAM-1 antibody (10 microg ml(-1)) to the C8161 cells at an effector:tumour cell ratio of 40:1 caused a 2.3-fold reduction in lysis of tumour cells and a 3-fold reduction in lysis of RA-treated cells. Blocking ICAM-1 antibody at optimum concentrations of 5 microg ml(-1) reduced lysis 1.8-fold in control Hs294T cells and 1.3-fold in RA-treated cells. Blocking the HLA-ABC complex had no effect on lysis. The more highly metastatic C8161 cells were found to secrete 4-fold greater levels of sICAM-1 than the poorly metastatic Hs294T cells and addition of sICAM-1 to the assay failed to affect lysis of either cell line but did induce a 2-fold decrease in lysis of RA-treated C8161 cells. Collectively, these data provide further evidence for ICAM-1 involvement in the tumour/LAK cell response and indicates that the RA-induced increase in mICAM-1 levels are partly responsible for the increase in susceptibility of the tumour cells. sICAM-1 appears to be unimportant in evasion of the tumour cells from LAK cell lysis, but may play a role in evasion of RA-treated C8161 cells.

Synergistic induction of ICAM-1 expression by cisplatin and 5-fluorouracil in a cancer cell line via a NF-kappaB independent pathway

Cisplatin (CDDP) and 5-fluorouracil (5-FU) are common anti-tumour agents, and the anti-tumour effect of CDDP and 5-FU are synergistically enhanced by combined treatment. To clarify the mechanisms of this synergism, we examined the effect of CDDP and 5-FU on the expression of cell adhesion molecules involved in recognition of cancer cells by T lymphocytes. When NA cells, a squamous cell carcinoma cell line, were exposed to CDDP and 5-FU for 18 h, the expression of intercellular adhesion molecule-1 (ICAM-1) was synergistically induced, whereas CDDP or 5-FU alone did not induce the expression of ICAM-1, as determined by flow cytometry. Expression of ICAM-2 and ICAM-3, which are recognized by the same counter receptor on T-cells, were not up-regulated by CDDP and 5-FU. RT-PCR analysis showed that the induction of ICAM-1 on NA cells might be due to transcriptional induction of ICAM-1 mRNA. Treatment with genistein, a protein tyrosine kinase (PTK) inhibitor, inhibited the induction of ICAM-1 on NA cells by CDDP and 5-FU, whereas staurosporin, a protein kinase C inhibitor, did not. Although CDDP and 5-FU induced binding at the nuclear factor kappa B (NF-kappaB) site in the ICAM-1 promoter, pretreatment with genistein did not prevent CDDP and 5-FU-induced binding at the NF-kappaB site. Moreover, a NF-kappaB nuclear translocation inhibitor did not inhibit the induction of ICAM-1 expression by treatment with CDDP and 5-FU. The synergistic effect of CDDP and 5-FU was not specific to NA cells, since ICAM-1 was synergistically induced by CDDP and 5-FU on HSC-4 cells, a squamous cell carcinoma cell line. These findings indicate that treatment with CDDP and 5-FU induces ICAM-1 expression by a NF-kappaB independent regulatory mechanism involving PTK.

Nitric oxide up-regulates the expression of intercellular adhesion molecule-1 on cancer cells

Nitric oxide (NO) is an unstable free radical that functions as a cytotoxic agent secreted by macrophages to kill cancer cells. Here we report the effect of NO on the expression of intercellular adhesion molecule-1 (ICAM-1) on cancer cells. NO donors such as SNP, SNAP and SIN-1 up-regulated the expression of ICAM-1 on NA cells, a squamous cell carcinoma cell line. Northern blot analysis showed that the induction of ICAM-1 might be due to transcriptional induction of ICAM-1 mRNA. Up-regulation of ICAM-1 mRNA by NO donors was inhibited by carboxy-PTIO, a NO scavenger. Although NF-kappaB activity was induced by NO donors, AP-1 was not induced by them. Staurosporin, a protein kinase C (PKC) inhibitor, inhibited the induction of ICAM-1 on NA cells by NO, whereas genistein, a protein tyrosine kinase inhibitor, did not. These findings indicate that NO up-regulates ICAM-1 expression on cancer cells by a regulatory mechanism involving PKC and suggest that NF-kappaB, but not AP-1, might be involved in induction of ICAM-1 by NO in cancer cells.

Retinoic acid up-regulates the expression of major histocompatibility complex molecules and adhesion/costimulation molecules (specifically, intercellular adhesion molecule ICAM-1) in human cervical cancer

OBJECTIVE

Retinoids are a class of compounds that are structurally related to vitamin A and have been found to be effective in the prevention and treatment of cervical cancer. To investigate whether enhanced immunogenicity might be responsible for such efficacy, we evaluated the effects of retinoic acid on the expression of major histocompatibility complex class I and class II and intercellular adhesion molecule ICAM-1 in human cervical carcinoma cell lines.

STUDY DESIGN

The expression of surface antigens (major histocompatibility complex class I and class II and ICAM-1) was evaluated by fluorescence-activated cell sorter analysis in 3 human cervical carcinoma cell lines after exposure to therapeutic doses of retinoic acid. In addition, the effects on human leukocyte antigen class I messenger ribonucleic acid expression were also evaluated by Northern blot analysis after such treatment.

RESULTS

CaSki, SiHa, and HT-3 cervical cancer cells expressed variable levels of major histocompatibility complex class I and ICAM-1 antigens, whereas class II surface antigens were not detectable. Exposure to therapeutic doses of retinoic acid were able to significantly increase the expression of major histocompatibility complex class I and ICAM-1 antigens in all the cell lines when compared with untreated tumor cells but were not able to induce the expression of class II surface human leukocyte antigens. Northern blot analysis showed that for major histocompatibility complex class I molecules such up-regulation was the result of an increased expression at the transcriptional level of major histocompatibility complex class I messenger ribonucleic acid.

CONCLUSIONS

These data indicate that retinoic acid increases the expression of immunologically important surface antigens, suggesting that the efficacy of retinoic acid in the treatment of cervical cancer may be, at least in part, the result of immunologic modulation. Such findings support additional clinical research investigating the use of retinoids for the treatment of cervical cancer.

Intercellular adhesion molecule-1 is upregulated via the protein kinase C pathway in human thyroid carcinoma cell lines

Nonantigen specific adhesion systems lymphocyte function-associated antigen 1/intercellular adhesion molecule (LFA-1/ICAM-1) and cluster designation 2/lymphocyte function-associated antigen 3 (CD2/LFA-3) are considered a crucial step in immune-mediated cell-cell adhesion reactions. In particular, the LFA-1/ICAM-1 system is deeply involved in major histocompatibility system (MHC)-restricted and non-MHC-restricted cellular cytotoxicity of effector cells against cancer tissues. We have investigated in human thyroid carcinoma cell lines the role of the protein kinase C (PKC) pathway on ICAM-1 expression. Incubation with tissue plasminogen activator (TPA), an agonist of PKC, of two papillary (NPA and TPC-1) and one anaplastic (ARO) carcinoma cell lines induced an ICAM-1 upregulation of both protein and mRNA production. This phenomenon was dependent on RNA and protein synthesis and was inhibited by PKC antagonists such as staurosporine and H-7. A parallel increase in the soluble form of ICAM-1 followed the upregulation of cellular ICAM-1 levels induced by TPA. In conclusion, the PKC pathway is involved in the regulation of ICAM-1 expression in human thyroid carcinoma cell lines. Further studies are necessary to clarify the effects of the PKC pathway on the diffusion of thyroid tumors.

Expression of beta1-integrins and pseudo-immunoglobulins on acute promyelocytic leukemia cells and its modifications during in vitro differentiation

Adhesion molecules are involved in cell-cell interactions and therefore probably play a role in the differentiation and egress of cells from the bone marrow, which might be potentially important in the biology of acute promyelocytic leukemia (APL). All-trans retinoic acid (ATRA) is known to induce in vitro and in vivo differentiation of APL cells and to favor their release from the bone marrow into the blood at initiation of therapy. In order to determine whether these effects might be mediated in part by modifications of beta1-integrin and pseudoimmunoglobulin expression on APL cells, the expression of these adhesion molecules on bone marrow (BM) blast cells from 24 APL patients was assayed at diagnosis by an indirect immunofluorescence method. CD49b, CD49d, CD49e, CD49f, CD54, CD58, and CD56 were expressed respectively on 18%+/-20% (0-66%), 40%+/-31% (0-96%), 48%+/-32% (0-97%), 29%+29% (1-94%), 51%+/-30% (5-98%), 37%+/-24% (1-85%) and 32%+/-31% (0-97%) of APL cells, with respectively 39%, 71%, 79%, 50%, 70%, 70%, and 53% positive cases (> or = 20% positive cells). Despite a wide variability between individual samples, the expression of beta1-integrins and that of pseudo-immunoglobulins tended to be higher in APL in comparison with that of a cohort of 63 patients with other AML subtypes with significant differences for CD54 expression (51%+/-30% vs 28%+/-27%, P=0.006) and CD56 expression (37%+/-24% vs 17%+/-19%, P=0.0003). An in vitro differentiation assay was performed in nine cases. Cells were harvested after 4-7 days of culture and studied for the expression of adhesion molecules. Granulocytic differentiation was marked by persistence of CD15 expression. Antigen expression was decreased after culture with ATRA for all beta1-integrins (except CD49b and CD49f) and pseudoimmunoglobulins (except CD54) tested. However, changes were statistically significant only for CD56 (P=0.04), CD49d (P=0.02) and CD49e (P=0.01). The modifications in the expression of the beta1-integrins and pseudo immunoglobulins were not specific to ATRA-induced differentiation, but commonly observed with differentiation. Furthermore, the modifications in the adhesive properties of APL cells to extracellular matrix proteins, observed on adhesion assays, were not statistically significant after ATRA-induced differentiation. Overall, the level of expression of beta1-integrins and pseudo-immunoglobulins was higher in APL than in other AML subtypes, and appeared modified with induced differentiation. This was not specific of ATRA, but might be involved in the general differentiation phenomenon. The modulation of adhesion molecules does not seem a sufficient requisite for the development of the retinoic acid syndrome, but could nevertheless be part of the increase in leukocyte counts observed during the first days of ATRA therapy.

Cloning, sequencing and analysis of cDNA encoding bovine intercellular adhesion molecule-1 (ICAM-1)

Intercellular adhesion molecule-1 (ICAM-1) is an inducible glycoprotein that interacts with the leukocyte beta 2-integrins, LFA-1 and Mac-1. We have isolated and analyzed a cDNA clone coding for the putative bovine ICAM-1 gene and compared it with known comparative sequences from other species as well as bovine ICAM-3. The 3398-bp bovine ICAM-1 cDNA sequence codes for 535 amino acids and shows 57% homology with human ICAM-1 and 47% homology with bovine ICAM-3 at the amino acid levels. The predicted number and positions of cysteine residues in bovine ICAM-1 are all conserved among species including bovine ICAM-3. It has two arginine-glycine-aspartate (RGD) sites in the extracellular region and a serine residue in the cytoplasmic tail. Northern blot results show that the bovine ICAM-1 gene is expressed in stimulated leukocytes whereas bovine ICAM-3 is expressed predominantly in resting neutrophils.

Retinoic acid inhibits the regulated expression of vascular cell adhesion molecule-1 by cultured dermal microvascular endothelial cells

The regulated expression of cell adhesion molecules (CAM) on endothelial cells is central to the pathogenesis of various inflammatory processes. Retinoic acid and synthetic derivatives have been demonstrated to exert antiinflammatory effects in cutaneous diseases. To determine modes of retinoid action in the modulation of inflammatory responses, we explored effects of all-trans-retinoic acid (t-RA) on the TNFalpha-induced expression of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and E-selectin in cultured human dermal microvascular endothelial cells. Pretreatment with t-RA specifically prevented TNFalpha-induced VCAM-1 expression, but not ICAM-1 and E-selectin induction. t-RA significantly reduced VCAM-1-dependent T cell binding to TNFalpha-treated human dermal microvascular endothelial cells as well. This differential modulation of TNFalpha-induced CAM expression by t-RA was reflected at steady state mRNA levels and in nuclear run-on studies. In transcriptional activation studies, the TNFalpha-mediated activation of the human VCAM-1 promoter was inhibited after t-RA treatment, while the ICAM-1 promoter activation was unaffected, indicating that the selective inhibition of CAM expression is regulated in part at the level of gene transcription. Furthermore, the transcriptional inhibition by t-RA appears to be mediated by its effects upon the activation of NF-kappaB-dependent complex formation. Analysis of protein-DNA binding assays revealed marked inhibition of specific NF-kappaB-dependent binding to the tandem NF-KB sites of the VCAM-1 promoter, but not to the functional NF-kappaB motif of the ICAM-1 promoter. The specific inhibition of cytokine-mediated VCAM-1 gene expression in vitro may provide a potential basis by which retinoids exert their biological effects at sites of inflammation in vivo.

Influence of retinoic acid on the expression of cytokeratins, vimentin and ICAM-1 in human gingival epithelia in vitro

Phenotypic differences exist in vivo between junctional (JE) and oral gingival (OGE) epithelia and an in vitro system has been developed that maintains phenotypic differences. This system, which permits in vitro studies of factors that may influence the epithelial phenotype, was used to investigate the effects of retinoic acid (RA) on epithelial expression of various markers known to distinguish JE from OGE. Primary cultures of JE and OGE were initiated from defined gingival regions and were subcultured and grown for 48 h in 96-well plates or on multiple-well slides. Control cultures were grown in medium supplemented with delipidized serum and all-trans RA was added to experimental groups. Other cultures were grown in a defined RA-free medium. Cultures were examined using monoclonal antibodies against cytokeratins, vimentin, and ICAM-1 and binding displayed by indirect immunocytochemical staining. Staining reactions were assessed by direct microscopic observation and assayed by spectrophotometric quantitation. The results showed that RA had minor effects on the marker expression of JE but markedly enhanced expression of cytokeratins 8, 18, 19, vimentin and ICAM-1 in OGE. These markers, which normally distinguish JE from OGE, were expressed at levels approaching or exceeding those of control JE cultures. These observations indicate that RA responsive mechanisms affect the phenotypes expressed by epithelia in vitro and suggest that such mechanisms may be related to the different phenotypic patterns expressed by gingival epithelia in vivo.

Intercellular adhesion molecule-1

The intercellular adhesion molecule (ICAM) 1 is an Ig-like cell adhesion molecule expressed by several cell types, including leukocytes and endothelial cells. It can be induced in a cell-specific manner by several cytokines, for example, tumor necrosis factor-alpha, interleukin-1, and interferon-gamma, and inhibited by glucocorticoids. Its ligands are the membrane-bound integrin receptors LFA-1 and Mac-1 on leukocytes, CD43, the soluble molecule fibrinogen, the matrix factor hyaluronan, rhinoviruses, and Plasmodium falciparum malaria-infected erythrocytes. ICAM-1 expression is predominantly transcriptionally regulated. The ICAM-1 promoter contains several enhancer elements, among them a novel kappa B element which mediates effects of 12-O-tetradecanoylphorbol-13-acetate, interleukin-1, lipopolysaccharide, tumor necrosis factor-alpha, and glucocorticoids. Expression regulation is cell specific and depends on the availability of cytokine/hormone receptors, signal transduction pathways, transcription factors, and posttranscriptional modification. ICAM-1 plays a role in inflammatory processes and in the T-cell mediated host defense system. It functions as a costimulatory molecule on antigen-presenting cells to activate MHC class II restricted T-cells, and on other cell types in association with MHC class I to activate cytotoxic T-cells. ICAM-1 on endothelium plays an important role in migration of (activated) leukocytes to sites of inflammation. ICAM-1 is shed by the cell and detected in plasma as sICAM-1. Regulation and significance of sICAM-1 are as yet unclear, but sICAM-1 is increased in many pathological conditions. ICAM-1 may play a pathogenetic role in rhinovirus infections. Derangement of ICAM-1 expression probably contributes to the clinical manifestations of a variety of diseases, predominantly by interfering with normal immune function. Among these are malignancies (e.g., melanoma and lymphomas), many inflammatory disorders (e.g., asthma and autoimmune disorders), atherosclerosis, ischemia, certain neurological disorders, and allogeneic organ transplantation. Interference with ICAM-1 leukocyte interaction using mAbs, soluble ICAM-1, antisense ICAM-1 RNA, and in the case of melanoma mAb-coupled immunotoxin, may offer therapeutic possibilities in the future. Integration of knowledge concerning membrane-bound and soluble ICAM-1 into a single functional system is likely to contribute to elucidating the immunoregulatory function of ICAM-1 and its pathophysiological significance in various disease entities.

Transcriptional regulation of the human intercellular adhesion molecule-1 gene: a short overview

Human intercellular adhesion molecule-1 (ICAM-1), a transmembrane glycoprotein that functions as a ligand for lymphocyte function-associated antigen-1, plays an important role in mediating cell-cell interactions in inflammatory reactions. It is induced by proinflammatory cytokines such as interleukin-1, tumor necrosis factor-alpha or interferon-gamma, as well as by phorbol esters, retinoic acid and lipopolysaccharide. Furthermore, ICAM-1 is upregulated by interleukin-6, which suggests that it belongs to the family of acute phase response genes. Investigation of the 5'-regulatory region of the human ICAM-1 gene revealed sequence motifs for a variety of transcription factors implicated in transcriptional regulation. This review summarizes the current knowledge of the transcriptional regulation of the human ICAM-1 gene.

Retinoic acid enhances connexin43 expression at the post-transcriptional level in rat liver epithelial cells

The mechanism by which all-trans retinoic acid (RA) stimulates gap junctional intercellular communication (GJIC) in the rat liver epithelial cell line. IAR203, was investigated. When RA, at 0.1 microM for 24-48 h, enhanced the dye transfer in IAR203 cells (x 1.4), it increased the amount of connexin43 (Cx43) in the cell-cell contact regions of the plasma membrane, as evidenced by analysis by Western blot and by immunofluorescence. It had no effect on the level of Cx43 mRNA. Freeze-fracture analysis of the size of gap junctions revealed an increase of the proportion of small gap junctions in RA-treated cells. We conclude that, in IAR203 cells, RA stimulates GJIC by acting at the post-transcriptional level of Cx43 regulation. The possibility that RA acts indirectly on the regulation of Cx43 expression, and increases the half-life of Cx43 by inducing adhesion molecules is discussed.

Regulation of intercellular adhesion molecule-1 expression by retinoic acid: analysis of the 5' regulatory region of the gene

Human intercellular adhesion molecule-1 (ICAM-1), a specific ligand for the lymphocyte-function-associated antigen-1, plays an important role in immune responses. ICAM-1 expression is regulated by various proinflammatory cytokines, by PMA, and by retinoic acid. In this study, we have investigated the mechanisms of transcriptional control involved in the stimulation of ICAM-1 gene expression by retinoic acid in SK-N-SH cells. Northern-blot analysis demonstrated that ICAM-1 mRNA is maximally induced at 24 hr, suggesting that it is not an early-response gene with respect to retinoic-acid responsiveness, whereas the retinoic acid receptor-beta mRNA level was maximal 12 hr following retinoic acid treatment. To analyze the 5'-regulatory region of the ICAM-1 gene, an EcoRI/SaII fragment spanning the first 1.3 kb upstream of the translational start site was used to direct the expression of a linked luciferase reporter gene in transient transfection assays in SK-N-SH cells. A 24-hr treatment of transfected cells with 10 microM retinoic acid resulted in a 10- to 13-fold increase in luciferase activity compared with untreated cells. Deletion mutant analysis revealed that a region located between -393 and -176 bp from the translational start site is critical for retinoic acid stimulation of luciferase activity. This region harbors a consensus sequence for a retinoic-acid-responsive element (RARE) homologous to the element found upstream of the alcohol dehydrogenase-3 gene. Co-transfection of expression vectors encoding the retinoic acid receptor-alpha, -beta, or -gamma, with reporter plasmids harboring the putative RARE, confirmed that the ICAM-1 gene is regulated by retinoic acid in a retinoic acid receptor-dependent fashion.

Autocrine regulation of ICAM-1 expression on bladder cancer cell lines: evidence for the role of IL-1 alpha

We have studied the autocrine regulation of essential expression of the intercellular adhesion molecule-1 (ICAM-1) on 8 transitional cell carcinoma (TCC) cell lines (histopathological grades 1-3). The constitutive expression of ICAM-1 was regulated by soluble factors in an autocrine fashion. These factors were produced by all cell lines, with the exception of the MGH-U1 cell line. The effects observed could be largely attributed to IL-1 alpha. However, the residual ICAM-1 inducing activity (up to 30% of ICAM-1 induction) could not be associated with any known ICAM-1 inducers (IFN gamma, TNF alpha, TNF beta, IL-1 alpha, IL-1 beta, IL-4, retinoic acid, LPS). In contrast to recombinant derived cytokines, the IL-1 alpha present in tissue culture supernatant was only able to induce ICAM-1 on high-grade tumours and not low-grade cells. This discriminative effect is similar to that noted following in vitro culture of tumour cells with bacillus Calmette-Guerin organisms. Whether the production of soluble factors (e.g., IL-1 alpha) by TCC cell lines plays an essential autocrine role for bladder tumours and/or affects the interaction with cells of the immune system needs to be investigated further.

Interactions between interferon gamma and retinoic acid with transforming growth factor beta in the induction of immune recognition molecules

The cell-surface expression of major histocompatibility (MHC) antigens and the adhesion molecule intercellular adhesion molecule 1 (ICAM-1) is essential for target cell recognition by T lymphocytes. The expression of both classes of molecule is induced by various cytokines, notably interferon gamma (IFN gamma). Since transforming growth factor beta (TGF beta) has been recently reported to antagonise HLA-DR induction by IFN gamma we have examined, using a number of murine and human cell lines, the effect of TGF beta on IFN gamma-induced MHC class I and class II and ICAM-1 expression. All of the cell lines tested expressed elevated class I MHC following IFN gamma treatment. Class II MHC induction was seen on most but not all of the cells, the exceptions being among a panel of human colorectal carcinoma cell lines. A striking difference between cells of different origin was noted in the response to TGF beta. TGF beta was found to antagonise IFN gamma-induced class I and class II MHC expression on C3H 10T1/2 murine fibroblasts, early-passage BALB/c mouse embryo fibroblasts, a murine oligodendroglioma cell line, and on MRC5 human fibroblasts and two human glioblastoma cell lines. Class II MHC was much more strongly inhibited (sometimes completely) than class I MHC. TGF beta also inhibited induction of class I MHC expression by IFN alpha. However, TGF beta did not inhibit class I or class II MHC induction by IFN gamma in any of the nine colorectal carcinoma cell lines, although two of five of the lines tested were growth-inhibited by TGF beta. On the other hand, human ICAM-1 induction by IFN gamma was not affected by simultaneous treatment with TGF beta in any of the cell lines. The down-regulation of IFN gamma-induced MHC antigens by TGF beta is not, therefore, the result of a general antagonism of IFN gamma. Retinoic acid has recently been reported to induce ICAM-1 expression on human tumour cells. We have confirmed this observation on MRC5, and the two human glioblastoma cell lines, however six colorectal carcinoma cell lines tested did not respond. In contrast to IFN gamma-induced ICAM-1 expression, retinoic-acid-induced ICAM-1 expression was inhibited by TGF beta on two of the three responsive lines.

Biphasic effect of camp-elevating agents on ICAM-1 expression stimulated by retinoic acid and interferonγ

Incubation of the human glioma cell line HS 683 in the presence of IFN-gamma or retinoic acid strongly stimulates the cell-surface expression of the intercellular adhesion molecule ICAM-1. We have investigated the role of the cAMP-mediated signal transduction pathway in this process and report that pharmacological agents which increased the intracellular levels of cAMP exhibited a biphasic action on ICAM-1 expression in human glioma cell line HS 683. Treatment for 1 hr with 25 microM forskolin or 1 mM isobutylmethylxanthine, or for 12 hr with 100 ng/ml pertussis toxin or 50 micrograms/ml cholera toxin transiently stimulated ICAM-1 expression with a maximal level of expression 8 hr post treatment, after which time ICAM-1 expression returned to the basal level. On the other hand, such pretreatments inhibited the inducing effects of either retinoic acid or IFN-gamma. Indeed, 24 hr after treatment with cAMP-elevating agents, both the retinoic-acid- and the IFN-gamma-induced ICAM-1 expression were inhibited by 60 to 80%, with a maximal 90 to 100% inhibition 72 hr post treatment. This inhibition of the cell-surface expression of ICAM-1 was confirmed at the mRNA level. The intracytoplasmic levels of cAMP were also quantified following treatments with forskolin, retinoic acid or IFN-gamma. In response to forskolin, cAMP levels increased 30-fold within 5 min, whereas a 10-fold increase occurred 60 min following treatment with 10 microM retinoic acid. Interferon gamma, in contrast, did not induce cAMP accumulation. These results were also correlated with an in vitro activation of adenylyl cyclase activity by retinoic acid and inhibition of this activity by IFN-gamma, in a dose-dependent and a GTP-dependent manner. Our results suggest that the suppression of IFN-gamma-induced ICAM-1 expression, obtained upon pre-treatment with cAMP-elevating agents, is due to direct antagonism with IFN-gamma action on adenylyl cyclase. However, the inhibition of retinoic-acid-induced ICAM-1 expression cannot be explained by the same mechanisms. The timing of adenylyl cyclase stimulation and cAMP accumulation, as well as the levels of cAMP accumulation, are probably involved in this inhibition. Our results also emphasize the fact that the induction of ICAM-1 expression is a multi-step process implicating different transductional signals among which cAMP might be involved as a second messenger.