Upregulation of HMG1 leads to melanoma inhibitory activity expression in malignant melanoma cells and contributes to their malignancy phenotype

Increased expression of HMGB1 is associated with poor prognosis in human bladder cancer

BACKGROUND AND OBJECTIVE

High-mobility group box 1 (HMGB1) is a versatile protein with intranuclear and extracellular functions that is involved in numerous biological and pathological processes, such as transcription, DNA repair, and response to infection and inflammation. HMGB1 overexpression has been reported in a variety of human cancers. However, the clinical significance of HMGB1 expression in bladder cancer (BC) remains unclear. This study is aimed to investigate the correlations between HMGB1 expression and prognosis in patients with BC.

METHODS

HMGB1 protein expression in 164 primary BC tissue specimens was analyzed by immunohistochemistry, and its association with clinicopathologic factors and prognosis was also analyzed.

RESULTS

HMGB1 protein had high expression in 87 of 164 cases of BC (53%). HMGB1 overexpression was significantly associated with tumor grade (P < 0.001), and stage (P = 0.001). The Kaplan-Meier survival analysis demonstrated that HMGB1 expression was significantly associated with shorter disease-free survival and overall survival (both P < 0.001). Multivariate analysis further demonstrated that HMGB1 was an independent prognostic factor for patients with BC.

CONCLUSIONS

HMGB1 might be a new molecular marker to predict the prognosis of patients with BC.

Inflammation and immune surveillance in cancer

Chronic inflammation is a risk factor for tumor development. However, understanding the effect of the immune system on tumor development has only been significantly advanced over the past two decades. We now appreciate that the immune system, in addition to tumor-suppressive function by eliminating nascent transformed tumor cells, can also exert selection pressure on tumor cells and facilitate tumor growth by providing a favorable tumor microenvironment. Yet, the distinctions between tumor-promoting inflammation and tumor-suppressive immunity are still not clear due to the dual role of some cytokines and other molecules in the immune system. The danger signal hypothesis has shaped our view of the role of immunity in cancer development, but still little is known about the exact role of danger signal receptors in cancer progression. In this review, we introduce the processes of cancer immunoediting and inflammation-induced cancer and discuss what is currently known about the role of danger signal receptors in cancer development and progression.

Effect of HMGB1 silencing on cell proliferation, invasion and apoptosis of MGC-803 gastric cancer cells

High-mobility group box 1 (HMGB1) is a multifunctional protein with intranuclear and extracellular functions. Although HMGB1 is overexpressed in approximately 85% of gastric cancers, the role of HMGB1 in gastric cancer biology remains unclear. In this study, we investigate the effect of downregulation of HMGB1 on the biological behavior of gastric cancer cells. MGC-803 gastric cancer cells were transduced with HMGB1-specific RNAi lentiviral vectors. Real-time polymerase chain reaction and Western blot analysis of HMGB1 mRNA and protein, respectively, validated the silencing effects. HMGB1-specific silencing significantly decreased cell proliferation. The impact on proliferation was observed at the cell cycle level--the number of cells in the G0/G1 phase increased, whereas that in S and G2/M phases decreased. Cell cycle changes were accompanied by decreases in cyclin D1 expression. Furthermore, HMGB1 silencing sensitized cells to apoptosis that was induced by oxaliplatin and mediated by the caspase-3 pathway. Finally, silencing of HMGB1 expression significantly reduced cellular metastatic ability and MMP-9 expression in MGC-803 cells. In summary, HMGB1 not only plays an essential role in the proliferation and invasion of MGC-803 cells but also represents a potential target for the therapeutic intervention of gastric cancer.

Cyclin-dependent kinase 5 phosphorylates mammalian HMGB1 protein only if acetylated

High mobility group box 1 (HMGB1) protein is the most abundant chromatin-associated non-histone protein expressed in all nucleated eukaryotic cells. We examined the phosphorylation of mammalian HMGB1 by testing the ability of the cyclin-dependent kinase 5 (Cdk5) to use as substrates native protein, either unmodified or in vivo acetylated and recombinant HMGB1. It turned out that Cdk5 was active on the in vivo acetylated HMGB1 only. We studied the effect of the phosphorylation on the 'architectural' properties of the acetylated HMGB1. The treatment with Cdk5 of the acetylated HMGB1 inhibited its capacity to induce DNA end-joining but had no effect on its ability to recognize distorted DNA structures.

Association of high mobility group box-1 protein levels with sepsis and outcome of severely burned patients

BACKGROUND

The study was performed to observe the systemic release and kinetics of high mobility group box-1 protein (HMGB1) in burned patients.

METHODS

106 patients were included, and they were divided into three groups with different burn sizes: group I, group II and group III. Healthy volunteers served as normal controls (n=25). The peripheral blood samples were collected on postburn days (PBD) 1, 3, 7, 14, and 21. The blood samples were used to detect levels of HMGB1 in plasma by ELISA kits for human. Gene expression of HMGB1 in peripheral blood mononuclear cells was assessed by real-time quantitative PCR taking GAPDH as the internal standard.

RESULTS

The levels of HMGB1 were significantly elevated on PBD 1-21 in patients with various burn sizes compared with normal controls, and there were obvious differences between group I and group III. The HMGB1 levels were significantly higher in septic patients than those without sepsis on PBD 7-21. Among septic patients, the HMGB1 levels in the survival group were markedly lower than those with fatal outcome on PBD 3-21.

CONCLUSIONS

Extensive burn injury could result in significantly increased HMGB1 levels, which appears to be associated with the development of sepsis and fatal outcome of major burns.

High-mobility group box 1 and cancer

High-mobility group box 1 protein (HMGB1), a chromatin associated nuclear protein and extracellular damage associated molecular pattern molecule (DAMP), is an evolutionarily ancient and critical regulator of cell death and survival. Overexpression of HMGB1 is associated with each of the hallmarks of cancer including unlimited replicative potential, ability to develop blood vessels (angiogenesis), evasion of programmed cell death (apoptosis), self-sufficiency in growth signals, insensitivity to inhibitors of growth, inflammation, tissue invasion and metastasis. Our studies and those of our colleagues suggest that HMGB1 is central to cancer (abnormal wound healing) and many of the findings in normal wound healing as well. Here, we focus on the role of HMGB1 in cancer, the mechanisms by which it contributes to carcinogenesis, and therapeutic strategies based on targeting HMGB1.

The expression of HMGB1 protein and its receptor RAGE in human malignant tumors

High Mobility Group Box 1 (HMGB1) is a nuclear non-histone protein discovered to be released in the extracellular medium as a response to various stimuli and implicated in cancerogenesis. High HMGB1 levels are reported in a variety of tumor types, but there are few data relating HMGB1 to the histological grade or to a particular cell type and cellular localization. We studied the expression of HMGB1 protein in malignant human tumors of different differentiation level and in tumor metastasis. In all tumor tissues, the protein level is elevated. In moderately differentiated carcinomas, the localization of the protein is perinuclear, while in the low differentiated; there is a tendency for non-specific nuclear localization. HMGB1 protein and its receptor RAGE are identified as a ligand-receptor pair that plays an important role in regulating the invasiveness of tumor cells. RAGE is not produced in all of the tested tumor specimens. We found high level of expression in hepatocellular, colorectal, and breast cribriform carcinomas, but not in malignant testicular specimens. Probably, the RAGE synthesis is related to distinctive tumor types. In metastatic cells, RAGE exhibits higher level of expression losing its specific granular cytosolic pattern characteristic for the primary tumors.

Ethyl pyruvate administration inhibits hepatic tumor growth

EP is a potent inhibitor of HMGB1 release that has significant anti-inflammatory activities and exerts a protective effect in animal models of inflammation. As inflammation is linked to cancer growth, we hypothesized that EP would have anti-tumor activity and explored its effects in a liver tumor model. Mice injected intraportally with MC38 colorectal cancer cells led to the growth of visible hepatic tumors within 2 weeks. Pretreatment with EP 30 min prior to infusion of tumor cells and continuing daily for 9 days inhibited tumor growth significantly in a dose-dependent manner, with 80 mg/kg EP achieving >70% reduction in the number of tumor nodules when compared with untreated animals. Delayed treatment with EP also suppressed tumor growth significantly, although to a lesser extent. Tumors had early, marked leukocytic infiltrates, and EP administration decreased innate (NK cells, monocytes) and adaptive (T and B cell lymphocytic) immune cell infiltrates acutely and significantly in the liver. Serum IL-6 and HMGB1 levels, which were elevated following tumor injection, were decreased significantly in EP-treated animals. Tumors showed an increase in apoptosis in EP treated mice, and tumor cells treated in vitro with EP had marked increases in LC3-II and cleaved PARP, consistent with enhanced autophagic flux and apoptosis. Thus, EP inhibition of tumor growth in the liver was mediated by tumor (induction of apoptosis) and host (decreased inflammation) effects. EP administration may have a therapeutic role in the treatment of cancer in conjunction with other therapeutic agents.

Endogenous damage-associated molecular pattern molecules at the crossroads of inflammation and cancer

Inflammatory mediators play important roles in the development and progression of cancer. Cellular stress, damage, inflammation, and necrotic cell death cause release of endogenous damage-associated molecular pattern (DAMP) molecules or alarmins, which alert the host of danger by triggering immune responses and activating repair mechanisms through their interaction with pattern recognition receptors. Recent studies show that abnormal persistence of these molecules in chronic inflammation and in tumor microenvironments underlies carcinogenesis and tumor progression, indicating that DAMP molecules and their receptors could provide novel targets for therapy. This review focuses on the role of DAMP molecules high-mobility group box 1 and S100 proteins in inflammation, tumor growth, and early metastatic events.

Involvement of high mobility group B proteins in cisplatin-induced cytotoxicity in squamous cell carcinoma of skin

Cis-diamminedichloroplatinum (II) (cisplatin) is a well-known anticancer drug with high potency and efficacy against various types of human cancers. Although it is widely accepted that the mechanism of cisplatin action is via apoptosis, there is enough evidence to support that cisplatin-induced cell death also occurs by other nonapoptotic pathways. Nonhistone, high mobility group (HMG) proteins are known to bind cisplatin-damaged DNA, and we studied their expression during cisplatin-induced cell death using immunohistochemistry, Western blot, and RT-PCR. Results show that the cell death is primarily apoptotic during initial stages of cisplatin treatment of skin tumors, and there is only marginal increase in high mobility group B (HMGB) levels, indicating that HMGB are still bound to nucleus. However, extended treatment of skin tumors with cisplatin caused necrosis and showed significantly increased levels of HMGB, which suggests that HMGB thus released from nuclei act as cytokine and trigger inflammatory response leading to necrosis. Present results clearly indicate a strong association between HMGB proteins and cisplatin-induced cell death that is dominantly apoptotic or necrotic depending on the duration of cisplatin exposure. Because of their important implication in the outcome of cancer chemotherapy, HMGB proteins can be interesting therapeutic targets.

Co-treatment with deoxycholic acid and azoxymethane accelerates secretion of HMGB1 in IEC6 intestinal epithelial cells

OBJECTIVES

High-mobility group box 1 (HMGB1) is a nuclear protein that acts as a ligand of the receptor for advanced glycation end products (RAGE) and its expression enhances progression of cancer. However, the mechanism underlying HMGB1 secretion is still unclear. In this study, we examined the effect of deoxycholic acid (DCA), a promoter of colon carcinogenesis, on HMGB1 secretion.

MATERIALS AND METHODS

We used an in vitro transformation model comprised of IEC6 intestinal epithelial cells treated with azoxymethane (AOM) and/or DCA. HMGB1 expression and secretion were examined by Western and Northern blot analyses, and ELISA. Intracellular translocation of HMGB1 was examined by protein fractionation.

RESULTS

AOM + DCA-treated IEC6 cells showed upregulation of HMGB1 mRNA expression and increased level of HMGB1 protein in culture medium, but decreased level of HMGB1 protein in the nucleus. AOM + DCA treatment increased level of histone H4 acetylation, which induced translocation of HMGB1 from the nucleus to the cytoplasm and increased HMGB1 secretion. Leptomycin B inhibited extranuclear translocation and secretion of the HMGB1 protein.

CONCLUSION

These findings suggest that DCA affects intracellular localization and secretion of HMGB1.

Cadherin-7 interacts with melanoma inhibitory activity protein and negatively modulates melanoma cell migration

Melanoma inhibitory activity (MIA) has been identified as a small protein secreted from malignant melanoma cells, which strongly enhances melanoma cell migration and invasion. Detailed analyses performed by our group showed interaction of MIA with extracellular matrix proteins and integrin alpha4beta1 and alpha5beta1 leading to cellular detachment. In this study, we identified cadherin-7 as a new MIA-binding protein using surface-enhanced laser desorption/ionization-mass spectrometry technology and co-immunoprecipitation. Cadherin-7 is a classical cell-cell adhesion molecule which was shown to be upregulated in malignant melanoma. We demonstrated enhanced expression of cadherin-7 in primary tumor cells compared to metastatic cells. Upregulation of cadherin-7 expression in metastatic cell lines but also downregulation of expression in cells derived from primary melanomas resulted in reduced cell migration. In addition, we speculate that MIA/cadherin-7 interaction may regulate cell-cell adhesion of malignant melanoma cells influencing the migration of the cells. Interestingly, overexpression of cadherin-7 resulted in a decreased MIA mRNA expression. In addition, MIA effects on cell migration were abrogated in cell clones overexpressing cadherin-7. In conclusion, these findings suggest that cadherin-7 regulates the expression and activity of MIA and the migration of melanoma cells playing a role in tumor development of malignant melanoma.

Chromatin-specific remodeling by HMGB1 and linker histone H1 silences proinflammatory genes during endotoxin tolerance

Epigenetic silencing of tumor necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) transcription occurs in blood leukocytes of animals and humans after the initiation of severe systemic inflammation (SSI). We previously reported that the epigenetic signature requires induction of NF-kappaB factor RelB, which directs histone H3K9 dimethylation, disrupts assembly of transcription activator NF-kappaB p65, and induces a sustained switch from the euchromatin to heterochromatin. Here, we report the novel findings that intracellular high mobility group box 1 protein (HMGB1) and nucleosome linker histone H1 protein are necessary components of endotoxin-mediated silencing of TNF-alpha in THP-1 human promonocytes. HMGB1 binds the TNF-alpha promoter during transcription silencing and promotes assembly of the repressor RelB. Depletion of HMGB1 by small interfering RNA results in dissociation of RelB from the promoter and partially restores TNF-alpha transcription. Histone H1, which typically displaces HMGB1 from nucleosomal DNA, also binds concomitantly with HMGB1 to the heterochromatin of the silenced TNF-alpha promoter. Combined knockdown of HMGB1 and H1 restores binding of the transcriptionally active NF-kappaB p65 and reestablishes TNF-alpha mRNA levels. Chromatin reimmunoprecipitation experiments demonstrate that HMGB1 and H1 are likely recruited to TNF-alpha sequences independently and that their binding correlates with histone H3K9 dimethylation, as inhibition of histone methylation blocks HMGB1 and H1 binding. Moreover, HMGB1- and H1-mediated chromatin modifications are gene specific during endotoxin silencing in that they also bind and repress acute proinflammatory IL-1beta, while no binding nor repression of antiinflammatory IkappaBalpha is observed. Finally, we find that H1 and HMGB1 bind to the TNF-alpha a promoter in human leukocytes obtained from patients with SSI. We conclude proinflammatory HMGB1 and structural nucleosome linker H1 couple as a component of the epigenetic complex that silences acute proinflammatory TNF-alpha during the assembly of heterochromatin in the SSI phenotype.

Spt2p defines a new transcription-dependent gross chromosomal rearrangement pathway

Large numbers of gross chromosomal rearrangements (GCRs) are frequently observed in many cancers. High mobility group 1 (HMG1) protein is a non-histone DNA-binding protein and is highly expressed in different types of tumors. The high expression of HMG1 could alter DNA structure resulting in GCRs. Spt2p is a non-histone DNA binding protein in Saccharomyces cerevisiae and shares homology with mammalian HMG1 protein. We found that Spt2p overexpression enhances GCRs dependent on proteins for transcription elongation and polyadenylation. Excess Spt2p increases the number of cells in S phase and the amount of single-stranded DNA (ssDNA) that might be susceptible to cause DNA damage and GCR. Consistently, RNase H expression, which reduces levels of ssDNA, decreased GCRs in cells expressing high level of Spt2p. Lastly, high transcription in the chromosome V, the location at which GCR is monitored, also enhanced GCR formation. We propose a new pathway for GCR where DNA intermediates formed during transcription can lead to genomic instability.

Transmitting genetic information without creating deleterious genetic alternations is one of the cell's most important tasks. When cells cannot repair DNA damage properly, it leads to genomic instability and results in genetic disorders, including cancer. Many studies, including ours, have started to uncover pathways suppressing one type of genomic instability, gross chromosomal rearrangement (GCR). However, the pathogenic mechanism to promote GCR that could mimic the hyper-activation of oncogenes during tumorigenesis is not clearly understood. The high expression of HMG1 has been documented many times as a putative oncogene. Therefore, we tested whether high expression of its yeast homologue, Spt2p, could induce pathogenic effect including GCR formation. Excess Spt2p expression indeed induced GCR formation dependent on its role in transcription elongation and polyadenylation. Further studies to find mechanisms resided in GCR formation by Spt2p revealed that excess Spt2p increased single-stranded DNA to produce GCR. Our studies provide a mechanistic bridge between transcription and genomic instability.

Overexpression of high mobility group (HMG) B1 and B2 proteins directly correlates with the progression of squamous cell carcinoma in skin

High mobility group B (HMGB) chromosomal proteins, which plays important role in cancer and inflammation, were followed at various stages of the squamous cell carcinoma of skin. Present results were analyzed by histopathology, BrdU assay, immunohistochemistry, western blot and RT-PCR, which indicate that at early stages of tumorigenesis, expression of HMGB (B1, B2), raised only by about 20%. However, the advanced (> or =12 weeks) tumors showed significant (> or =80%) increase in HMG levels. Using skin cancer model, we demonstrated that high levels of HMGB directly correlate with the extent of neoplastic changes, and it appears that HMGB is an effective stimulus for cell differentiation, tumor progression, and metastatic invasion.

Non-Hodgkin lymphoma expressing high levels of the danger-signalling protein HMGB1

HMGB1 is a high mobility group protein that can act either as a DNA binding protein or extracellularly as a cytokine-like danger signal. Extracellular HMGB1, either actively secreted or passively released by necrotic cells, is linked to inflammation and cancer. Herein, the results of a study to quantify the expression of HMGB1 in lymphomas by quantitative real-time RT-PCR are presented. HMGB1 expression was analysed in 18 non-Hodgkin lymphomas and two lymphoma cell lines. 11/18 primary lymphomas expressed HMGB1 mRNA at a level exceeding the average of normal lymph nodes. Immunohistochemistry showed that HMGB1 positivity is confined to the lymphoma cells. No correlation between HMGB1 expression and grading was found. However, a high percentage of lymphomas is overexpressing a danger-signalling protein. This protein can support the growth and angiogenesis of lymphoma cells in a paracrine way when released e.g. due to necrosis. Thus it constitutes an interesting therapeutic target as well.

Increased expression of high mobility group box 1 (HMGB1) is associated with progression and poor prognosis in human nasopharyngeal carcinoma

High mobility group box 1 (HMGB1) is a versatile protein with intranuclear and extracellular functions that is involved in numerous biological and pathological processes, such as transcription, DNA repair, and response to infection and inflammation. The expression of HMGB1 has been described in many types of cancers, but the role of HMGB1 in nasopharyngeal carcinoma (NPC) is unknown. The aim of this study was to analyse the roles of HMGB1 in NPC progression and clinical outcome using NPC clinical samples. In an immunohistochemical study, HMGB1 had high expression in 89 of 166 cases of NPC (53.6%). HMGB1 overexpression was significantly associated with T classification (p = 0.01), N classification (p = 0.003), distant metastasis (p = 0.046), and clinical stage (p < 0.001). Patients with higher levels of HMGB1 expression had poorer overall survival and disease-free survival, whereas patients with lower levels of HMGB1 expression had better survival. Multivariate analysis showed that HMGB1 expression was an independent prognostic indicator for patient survival. Disruption of endogenous HMGB1 using small interfering RNAs suppressed NPC cell invasive ability. These data support the notion that HMGB1 overexpression has a role in the progression of NPC and hence its poor clinical outcome.

High mobility group box-1-inducible melanoma inhibitory activity is associated with nodal metastasis and lymphangiogenesis in oral squamous cell carcinoma

Melanoma inhibitory activity (MIA) is an 11-kDa secretory protein isolated from malignant melanoma cells that is correlated with invasion and metastasis in various human malignancies. We examined MIA expression in 62 oral squamous cell carcinomas (OSCC) by immunohistochemistry. MIA expression was significantly associated with nodal metastasis (P = 0.00018). MIA expression was also associated with expression of high mobility group box-1 (HMGB1) (P < 0.0001) and lymph vessel density (P < 0.0001). Expression levels of MIA, HMGB1, nuclear factor kB (NFkB) p65 and HMGB1-NFkB p65 binding were significantly higher in a metastatic human OSCC cell line (HSC3) than those in a non-metastatic OSCC cell line (HSC4). Treatment with receptor for advanced glycation end products (RAGE) antisense or small interfering RNA and human recombinant HMGB1 (hrHMGB1) did not affect MIA expression, whereas HMGB1 antisense or siRNA treatment decreased MIA expression in HSC3 cells. Then HMGB1 enhanced MIA expression as an NFkB cofactor but not as a RAGE ligand. MIA neutralization by MIA antibodies increased extracellular signal-related kinase 1/2 phosphorylation, but decreased p38 phosphorylation and the expression of vascular epithelial growth factor (VEGF)-C and -D. Treatment with p38 inihibitor decreased VEGF-C and -D expression in HSC3 cells. These results suggest that MIA expression is enhanced by the interaction of intracellular HMGB1 and NFkBp65 and MIA is closely involved in tumor progression and nodal metastasis by the increments of VEGF-C and VEGF-D in OSCC.

Masquerader: High Mobility Group Box-1 and Cancer

Since its identification a third of a century ago, the high-mobility group box-1 (HMGB1) protein has been linked to varied diverse cellular processes, including release from necrotic cells and secretion by activated macrophages engulfing apoptotic cells. Initially described as solely chromatin-associated, HMGB1 was additionally discovered in the cytoplasm of several types of cultured mammalian cells 6 years later. In addition to its intracellular role, HMGB1 has been identified extracellularly as a putative leaderless cytokine and differentiation factor. In the years since its discovery, HMGB1 has also been implicated in disease states, including Alzheimer's, sepsis, ischemia-reperfusion, arthritis, and cancer. In cancer, overexpression of HMGB1, particularly in conjunction with its receptor for advanced glycation end products, has been associated with the proliferation and metastasis of many tumor types, including breast, colon, melanoma, and others. This review focuses on current knowledge and speculation on the role of HMGB1 in the development of cancer, metastasis, and potential targets for therapy.

Potential protein markers for nutritional health effects on colorectal cancer in the mouse as revealed by proteomics analysis

It is suggested that colorectal cancer might be prevented by changes in diet, and vegetable consumption has been demonstrated to have a protective effect. Until now, little is known about the effects of vegetable consumption at the proteome level. Therefore, the effect of increased vegetable intake on the protein expression in the colonic mucosa of healthy mice was studied. Aim was to identify the proteins that are differentially expressed by increased vegetable consumption and to discriminate their possible role in the protection against colorectal cancer. Mice were fed four different vegetable diets, which was followed by analysis of total cellular protein from colonic mucosal cells by a combination of 2-DE and MS. We found 30 proteins that were differentially expressed in one or more diets as compared to the control diet. Six could be identified by MALDI-TOF MS: myosin regulatory light chain 2, carbonic anhydrase I, high-mobility group protein 1, pancreatitis-associated protein 3, glyceraldehyde-3-phosphate dehydrogenase and ATP synthase oligomycin sensitivity conferral protein. Alterations in the levels of these proteins agree with a role in the protection against colon cancer. We conclude that these proteins are suitable markers for the health effect of food on cancer. The observed altered protein levels therefore provide support for the protective effects of vegetables against colorectal cancer.

Increased expression of high mobility group box 1 (HMGB1) is associated with an elevated level of the antiapoptotic c-IAP2 protein in human colon carcinomas

BACKGROUND

High mobility group box 1 (HMGB1) is a non-histone chromosomal protein implicated in a variety of biologically important processes, including transcription, DNA repair, V(D)J recombination, differentiation, and development. Overexpression of HMGB1 inhibits apoptosis, arguing that the molecule may act as an antiapoptotic oncoprotein. Indeed, increased expression of HMGB1 has been reported for several different tumour types. In this study, we analysed human colon carcinoma for HMGB1 as well as for c-IAP2 expression levels. c-IAP2 is an antiapoptotic protein which may be upregulated as a consequence of nuclear factor kappaB (NFkappaB) activation via HMGB1.

METHODS

A comparative genomic hybridisation (CGH) database comprising 1645 cases from different human tumour types was screened to detect cytogenetic changes at the HMGB1 locus. Immunohistochemical staining of human colon tissue microarrays and tumour biopsies, as well as western blot analysis of tumour lysates, were performed to detect elevated HMGB1 and c-IAP2 expression in colon carcinomas. The antiapoptotic potential of HMGB1 was analysed by measuring caspase activities, and luciferase reporter assays and quantitative polymerase chain reaction analysis were employed to confirm NFkappaB activation and c-IAP2 mRNA upregulation on HMGB1 overexpression.

RESULTS

According to CGH analysis, the genomic locus containing the HMGB1 gene was overrepresented in one third (35/96) of colon cancers. Correspondingly, HMGB1 protein levels were significantly elevated in 90% of the 60 colon carcinomas tested compared with corresponding normal tissues evaluable from the same patients. HMGB1 increased NFkappaB activity and led to co-overexpression of the antiapoptotic NFkappaB target gene product c-IAP2 in vitro. Furthermore, increased HMGB1 levels correlated with enhanced amounts of c-IAP2 in colon tumours analysed by us. Finally, we demonstrated that HMGB1 overexpression suppressed caspase-9 and caspase-3 activity, suggesting that HMGB1 interferes with the apoptotic machinery at the level of apoptosomal caspase-9 activation.

CONCLUSIONS

We identified in vitro a molecular pathway triggered by HMGB1 to inhibit apoptosis via c-IAP2 induction. Our data indicate a strong correlation between upregulation of the apoptosis repressing HMGB1 and c-IAP2 proteins in the pathogenesis of colon carcinoma.

Melanoma inhibitory activity (MIA): an important molecule in melanoma development and progression

Cutaneous malignant melanoma is the leading cause of skin cancer death in industrialized countries. Melanoma development and progression are well defined by clinical and histopathological aspects; however, detailed analysis of molecular changes is still ongoing. The protein MIA, which is strongly expressed in melanoma cells but not in melanocytes, is likely to represent a key molecule regulating melanoma progression. Consistent with this, several in vitro and in vivo model systems indicate a direct involvement of MIA in melanoma migration and invasion, with recent studies suggesting a central role for MIA in early melanoma development by regulating important melanoma-related pathways and molecules. The latest developments in MIA research are summarized in this review, which describes recently published data related to the MIA protein structure and function, the role of MIA in melanoma development and progression, and the regulation of MIA expression. Furthermore, newly discovered MIA-homologous genes are discussed.

Genes involved in invasion and metastasis of gastric cancer identified by array-based hybridization and serial analysis of gene expression

Gastric cancer (GC) is still a serious health problem and remains the second most common type of fatal cancer worldwide. Comprehensive gene expression analyses may be useful to identify genes associated with invasion/metastasis in GC. Among them, array-based hybridization and serial analysis of gene expression (SAGE) are currently the most common approaches. Over the past 3 years, several large-scale gene expression studies with array-based hybridization and SAGE have been performed and several genes have been identified. This review describes genes associated with invasion/metastasis in GC which have been identified by array-based hybridization and SAGE. We compared the expression levels of the genes identified by array-based hybridization with our SAGE data. In addition, expression of the candidate genes obtained by SAGE was further investigated by quantitative RT-PCR of 40 GC samples. MIA and GW112 were overexpressed in 10 (25%) and 22 (55%) of 40 GC samples, and the overexpression of these two genes was associated with tumor stage, respectively. We also discuss the significance of HMGB1/amphoterin in invasion and metastasis of GC.

Inhibition of melanoma inhibitory activity (MIA) expression in melanoma cells leads to molecular and phenotypic changes

The secreted protein melanoma inhibitory activity (MIA) is highly expressed in malignant melanoma but not in melanocytes and is associated with tumor progression in vivo. Here, we further investigated the functional role of MIA by inhibiting MIA expression of the human melanoma cell line HMB2 via stable antisense MIA cDNA transfection, and subsequent analysis of the cell clones. MIA-deficient cell clones showed several changes in cell morphology and growth pattern. In monolayer and three-dimensional culture enhanced cell-cell contacts were formed. Furthermore, a re-induction of pigment synthesis in comparison with the amelanotic parental cell line HMB2 was observed. Molecular analyses revealed a re-expression of tyrosinase-related protein 1 (Trp-1) and tyrosinase in the MIA-deficient cell clones necessary for melanin synthesis. In accordance, re-expression of MIA in the MIA-deficient melanoma cell clones resulted in downregulation of Trp-1. To identify the molecular mechanisms of MIA regulating pigmentation, MITF and PAX3, two positive regulators of Trp-1 and tyrosinase transcription, and PIAS3, a negative regulator of MITF activity, were analyzed. Only in MIA-deficient cells, expression of PAX3 mRNA and MITF protein was found. In contrast, strong expression of PIAS3 was detected in HMB2 but not in the MIA-deficient cells. To our knowledge this is the first report demonstrating a correlation between MIA expression and pigmentation and morphology of melanocytic cells.

Biochemical observation of the rapid mobility of nuclear HMGB1

Formaldehyde-crosslinked and sonicated chromatin fragments were obtained from 15-day chicken embryo erythrocytes and purified on caesium chloride gradients. Polyclonal antibodies raised against chicken HMGB1 were used to immuno-precipitate fragments carrying HMGB1 in two protocols: (1) affinity purified antibodies covalently coupled to agarose beads and (2) diluted antiserum. The DNA of the antibody-bound chromatin was quantified and its sequence content assessed by quantitative real-time PCR to give values of the absolute enrichments generated. Amplicons were monitored within the active beta-globin locus, in the adjacent heterochromatin, in the lysozyme locus (containing an active housekeeping gene and the inactive lysozyme gene) and at the promoter of the inactive ovalbumin gene. For all amplicons the Bound/Input ratio was close to unity, implying no preferential location of HMGB1 on the chromatin. This initially unexpected result can now be understood in the light of the exceptional mobility of HMGB1 revealed by FLIP experiments showing that only 1-2 s are needed for HMGB1 to cross the nucleus: crosslinking times of 1 min were used in the present experiments.

First International Symposium on Melanoma and Other Cutaneous Malignancies

The First International Symposium on Melanoma and Other Cutaneous Malignancies, held in New York City on 23-25 April 2004, brought together researchers and clinicians from all over the world to discuss recent advances in the prevention, treatment and diagnosis of melanoma and other cutaneous malignancies. Discussion topics included primary and secondary prevention; advances in surgical therapy, including sentinel and elective lymph node dissection; the biology and pathogenesis of melanoma, including pathways of drug resistance; genomic analysis of melanoma, serum and tumour cell markers; with point and counterpoint sessions debating therapeutic controversies. The role of vaccines in the management of melanoma was discussed, including cell vaccines, dendritic cell-based vaccination and present research to improve the generation of melanoma vaccine-specific immunity. Adjuvant immunotherapy with high-dose IFN-alpha and an ongoing trial with biochemotherapy were debated. In addition, the role of chemotherapy and novel targeted agents in metastatic melanoma were discussed. Among the emerging agents and therapeutic targets presented were Bcl-2 antisense therapy, RAF kinases, heat-shock proteins, thalidomide and newer immunomodulatory drugs, cytotoxic T lymphocyte antigen-4 antibody and topical imiquimod. The symposium also provided an overview of existing and emerging agents and modalities in the management of patients with cutaneous T cell lymphomas, ocular melanoma and melanoma involving brain metastases. Sessions also included case-based learning and devoted ample time to providing 'how to' information for practising physicians.

Genes upregulated in a metastasizing human colon carcinoma cell line

Differential gene expression between the metastatic human colon cancer cell line HT29p and its nonmetastatic counterpart HT29-MTX was revealed by suppression subtractive hybridization. Fifty-eight individual genes showed increased mRNA levels in HT29p cells. Only 15 of these genes had been related to transformation in previous studies; the majority of genes are new candidates encoding proteins relevant for the metastatic process. Cancer profiling arrays as well as in situ hybridization study revealed that at least some of the genes obtained in the SSH screen are also differentially expressed in human tumors.

Strong expression of methylthioadenosine phosphorylase (MTAP) in human colon carcinoma cells is regulated by TCF1/[beta]-catenin

Methylthioadenosine phosphorylase (MTAP) is known as a ubiquitously expressed house keeping gene important in biochemical salvage processes. The MTAP gene is localized on the human chromosomal region 9p21, a region often deleted in cancer. Recently, several groups including our own have shown that MTAP serves as a tumour suppressor gene. The aim of this study was to analyse the role of MTAP in colon carcinoma and normal colon epithelium and the regulation of gene expression. To examine MTAP RNA and protein expression, we screened six colon carcinoma cell lines and human primary colon epithelial cells by RT-PCR and immunoblotting. MTAP expression was confirmed in vivo by immunohistochemical staining of normal colon tissue compared to adenoma and colon carcinoma. Interestingly, we found strong MTAP mRNA and protein expression by colon carcinoma cell lines but no expression by colonic epithelial cells. To analyse the regulation of MTAP expression, promoter studies were performed and revealed control of MTAP expression by LEF/TCF/beta-catenin. Furthermore, we demonstrated a significant correlation between MTAP protein expression and tumour progression as the intensity of MTAP protein staining increased from normal tissue to carcinoma. In addition, the recently postulated association between MTAP activity and interferon (IFN) sensitivity was confirmed in colon epithelial cells showing only little response to IFN-gamma, in contrast to the carcinoma cell lines. In summary, these data indicate for the first time that MTAP is not expressed in normal human colonic epithelium but is strongly upregulated in colon carcinoma. This finding may be of clinical significance concerning the homeostasis of normal colon epithelium and potential treatment of colon carcinoma.

Inhibition of immunosuppressive effects of melanoma-inhibiting activity (MIA) by antisense techniques

Melanoma inhibitory activity (MIA) is an 11 kD protein secreted by malignant melanomas. Recent studies revealed an interaction of MIA with epitopes of extracellular matrix proteins including fibronectin. Structural homology of MIA with the binding sites of alpha4beta1 integrin results in complex interactions of MIA with molecules binding to alpha4beta1 integrin. As cells of the immune system express alpha4beta1 integrins (VLA-4), we investigated whether MIA may modulate the function of human leukocytes. Here we describe the effects of MIA on the activation of human PBMCs and auto-/allogeneic lymphokine-activated killer cell (LAK) cytotoxicity in human MIA-negative glioma cell lines and MIA-positive melanoma cell lines in vitro. MIA inhibits PHA- or IL-2-induced human PBMC proliferation in a dose-dependent manner up to 63% ((3)H-Tdr incorporation) and 59% (cell count), respectively, when added to the cell culture prior to mitogen stimulation. In addition, both autologous (GL and HW) and allogeneic (HTZ-17, HTZ-243 and HTZ-374) antitumor LAK cytotoxicity was reduced by the addition of exogenous rhMIA (500 ng/ml, f.c.). Consequently, endogenous inhibition of MIA expression in human melanoma cells by MIA-specific phosphorothioate antisense oligonucleotides enhanced the autologous LAK-cell activity to the same level as observed in MIA-negative human HMB melanoma cells expressing an MIA-antisense construct. Our results indicate that MIA may contribute to immunosuppression frequently seen in malignant melanomas by inhibiting cellular antitumor immune reactions. Antagonization of MIA activity using antisense techniques may represent a novel therapeutic strategy for treatment of malignant melanomas.

Regulated expression and subcellular localization of HMGB1, a chromatin protein with a cytokine function

High mobility group box protein 1 (HMGB1) has been considered as a ubiquitous nuclear protein with an architectural function, but even early reports have described its presence outside of the nucleus. Today, we have only started to understand the extranuclear and extracellular functions of HMGB1: we know that it participates in developmental and differentiation processes, triggers and modulates many of the inflammatory cascades in the body, and may even be involved in the metastatic invasion programme of cancer cells. Given such diverse roles, it is important to know which cells express HMGB1, where, and how much. The present review deals with the expression pattern of HMGB1 and provides evidence that, far from being housekeeping, the HMGB1 gene is tightly regulated. This can have implications for therapeutic intervention on inflammatory diseases as well as cancer.

Amphoterin as an extracellular regulator of cell motility: from discovery to disease

Amphoterin is a ubiquitous and highly conserved protein previously considered solely as a chromatin-associated, nuclear molecule. Amphoterin is released into the extracellular space by various cell types, and plays an important role in the regulation of cell migration, differentiation, tumorigenesis and inflammation. This paper reviews recent research on the mechanistic background underlying the biology of secreted amphoterin, with an emphasis on the role of amphoterin as an autocrine/paracrine regulator of cell migration.

Gene expression dose-response changes in microarrays after exposure of human peripheral lung epithelial cells to nickel(II)

Occupational exposure to nickel compounds is associated with lung cancer risk; both genotoxic and epigenetic mechanisms have been proposed. For comprehensive examination of the acute effects of nickel(II) acetate on gene expression in cultured human peripheral lung epithelial HPL1D cells, microarray analyses were carried out with cDNA chips (approximately 8000 cDNAs). Cells were exposed for 24 h to nontoxic (50, 100, and 200 microM) or toxic (400, 800, and 1600 microM) nickel(II) concentrations. Cluster analysis was applied to the 868 genes with > or = 2-fold change at any concentration. Two main clusters showed marked up- or down-regulation at the highest, toxic concentrations. The data further subdivided into 10 highly cohesive clusters with high probability, and of these only 2 had the same response trend at low nontoxic as at high concentrations, an observation of clear relevance to the process of high- to low-dose extrapolation in risk assessment. There were 113 genes showing > or = 2-fold change at the three lower nontoxic concentrations, those most relevant to in vivo carcinogenesis. In addition to expected responses of metallothionein, ferritin, and heat-shock proteins, the results revealed for the first time changed expression of some potential cancer-related genes in response to low-dose Ni(II): RhoA, dyskerin, interferon regulatory factor 1, RAD21 homologue, and tumor protein, translationally controlled. Overall, most of the genes impacted by nontoxic concentrations of nickel(II) acetate related to gene transcription, protein synthesis and stability, cytoskeleton, signaling, metabolism, cell membrane, and extracellular matrix.