Human adenovirus oncolytic properties and the inhibitory role of E4 orf4 and E4 orf6/7 on endogenously activated NF-κB

Human adenovirus is a promising tool for cancer therapy as an oncolytic virus. To predict which region of the oncolytic adenovirus E4 gene could be deleted, we investigated the relationship between the E4 proteins and NF-κB. Here, we report that TLR2-dependent NF-κB activation in Ad5-infected cells was significantly inhibited 24 h post-infection. Among the six E4 proteins, E4 orf4 and E4 orf6/7 exhibited notable suppressive effects on NF-κB activation. However, only E4 orf4 was co-immunoprecipitated with the RelA protein, also known as p65. It appears likely that E4 orf6/7 represses NF-κB activation via E2F-dependent pathways. Our results suggest that both E4 orf4 and E4 orf6/7 are novel inhibitors of NF-κB activation. The inhibition of endogenous NF-κB activation by E4 proteins during the late phase of infection also appears to elucidate the previously reported suppression of E1A expression in the late phase of infection. These redundant suppressive effects of E4 orf4 and E4 orf6/7 on NF-κB suggest that these proteins may play a major role in the anticancer properties of oncolytic adenovirus.

Human antigen R knockdown attenuates the invasive activity of oral cancer cells through inactivation of matrix metalloproteinase-1 gene expression

Background/purpose

The RNA-binding protein human antigen R (HuR) recognizes AU-rich elements in the 3'-untranslated regions of mRNA. The expression of cytoplasmic HuR is related to the malignancy of many carcinomas. The aim of this study is investigation of effect of HuR knockdown for invasive activity of oral carcinoma.

Materials and methods

Proliferation, invasion, real-time PCR, and reporter gene assays were performed to confirm that the knockdown of HuR downregulates the invasive activity of cancer cells. Immunohistochemical staining was performed for high invasive carcinoma, squamous cell carcinoma (SCC) and low invasive carcinoma, verrucous carcinoma (VC), to determine if the localization of cytoplasmic HuR is related to matrix metalloproteinase-1 (MMP-1) expression.

Results

Invasive activity was significantly lower in HuR knockdown cancer cells than in control cells. A luciferase assay revealed that HuR knockdown inactivated the promoter activity of the MMP-1 gene. The mRNA levels of the transcription factors required for MMP-1 expression, including c-fos and c-jun, were decreased in HuR knockdown cancer cells. Immunohistochemical analysis revealed the level of cytoplasmic HuR and MMP-1 in invasive carcinoma to be higher than in low invasive cancer. HuR induced MMP-1 expression in the invasive front of most SCC cases.

Conclusion

HuR knockdown attenuated the invasive activity of cancer cells by decreasing the expression of the MMP-1, at least partially. HuR localization may help determine the invasive phenotype of cancer cells and inhibit cancer cell invasion. Furthermore, in oral SCC, HuR may be related to invasive activity through the expression of MMP-1.

High expression of Sam68 contributes to metastasis by regulating vimentin expression and a motile phenotype in oral squamous cell carcinoma

The present study aimed to investigate the clinical and biological significance of Src-associated in mitosis 68 kDa (Sam68) in oral squamous cell carcinoma (OSCC). Immunohistochemical analysis was performed on tissue samples obtained from 77 patients with OSCC. Univariate analysis revealed that the high expression of Sam68 was significantly correlated with advanced pathological T stage (P=0.01), positive lymphovascular invasion (P=0.01), and pathological cervical lymph node metastasis (P<0.01). Moreover, multivariate analysis demonstrated that the high expression of Sam68 was an independent predictive factor for cervical lymph node metastasis (odds ratio, 4.39; 95% confidence interval, 1.49-14.23; P<0.01). These results indicated that high Sam68 expression contributed to tumor progression, especially cervical lymph node metastasis, in OSCC. mRNA sequencing was also performed to assess the changes in the transcriptome between OSCC cells with Sam68 knockdown and control cells with the aim of elucidating the biological roles of Sam68. Gene Ontology enrichment analysis revealed that downregulated differentially expressed genes (DEGs) were concentrated in some biological processes related to epithelial-mesenchymal transition. Among these DEGs, it was established that vimentin was particularly downregulated in these cells. It was also confirmed that Sam68 knockdown reduced the motility of OSCC cells. Furthermore, the immunohistochemical study of vimentin identified the association between vimentin expression and Sam68 expression as well as cervical lymph node metastasis. In conclusion, the present study suggested that the high expression of Sam68 may contribute to metastasis by regulating vimentin expression and a motile mesenchymal phenotype in OSCC.

Abstract PO-017: Application of oncolytic adenovirus to desmoplastic pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the highly malignant tumors with the poorest prognosis worldwide. The five-year survival rate of pancreatic cancer patients is 5%. PDAC comprises a dense fibrotic stroma with an extracellular matrix produced by activated-human pancreatic stellate cells (HPSC), which helps tumor growth, infiltration and metastasis. It is the main reason for chemotherapy resistance since fibrotic stroma is impenetrable for drug delivery. AU-rich elements (ARE) are RNA elements commonly present in the 3’-UTR of certain mRNAs that encode many early response genes or growth-related genes such as proto-oncogenes. ARE enhances the rapid decay of mRNAs, and the fate of ARE-mRNA is controlled by ARE-binding proteins HuR. ARE-mRNA is stabilized in most types of cancers mediate by binding with HuR, which exports target ARE-mRNA to the cytoplasm. We have developed E4orf6-deficient adenovirus dl355 as an oncolytic virus. E4orf6 is a viral gene essential for viral replication and contributes to viral replication by stabilizing ARE-mRNA in infected cells. Therefore, dl355 can replicate only in cancer cells in which ARE-mRNA is stabilized and lyses the cells. If ARE-mRNA is stabilized not only in PDAC but also in the activated-HPSC, dl355 may be effective for surrounding fibrosis. We found that HuR was relocalized in the cytoplasm of human PDAC and HPSC activated by TGFβ-1. The co-culture enhanced HuR export of MIA PaCa-2 with activated-HPSC. Inhibition of HuR function using CMLD-2 reagent inactivated the growth, invasion and metastasis activities of PDAC. The proliferative and cytopathic effects of dl355 were very high with PDAC and even with activated-HPSC compared to quiescent cells. These results indicate that oncolytic adenovirus dl355 shows potentiality to kill both pancreatic cancer cells and activated-pancreatic stellate cells where an abundance of HuR in the cytoplasm. dl355 has the potential to overcome several critical hurdles proposed by the tumor microenvironment of desmoplastic pancreatic tumors.

Citation Format: Elora Hossain, Fumihiro Higashino. Application of oncolytic adenovirus to desmoplastic pancreatic cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-017.

Abstract PO-082: Radiation therapy enhances the potential of the oncolytic virus in the treatment of osteosarcoma

Background: Combination of neoadjuvant chemotherapy and surgery is the standard treatment approach for osteosarcoma. Despite aggressive treatment protocol, ~40% of patients do not respond and relapse, the survival rate is poor for these patients. Conditionally replicative adenovirus (CRAds) destroying cancer cell while sparing normal cells is a new treatment approach for cancers. We developed a new oncolytic adenovirus which grows using mRNA stabilization system found in many cancer cells. Our recent report showed that this virus replicated in cancer cells where AU-rich element (ARE) containing mRNA is stabilized. ARE-mRNA is stabilized in the majority types of cancers mediate by binding with HuR (Human antigen R), which exports target ARE-mRNA to the cytoplasm. Radiotherapy (RT) is not a first-line treatment option for osteosarcoma as osteosarcoma cells are not killed by radiation easily. But in certain conditions radiotherapy can be used where surgical resection is not technically possible without undue morbidity or when surgery is refused. In response to ionizing radiation and UV radiation DNA damage response (DDR) can influence HuR action either by the increasing cytoplasmic HuR abundance or affecting the binding affinity to target ARE-mRNA. The purpose of the present study was to analyze the efficacy of the combination treatment of RT and oncolytic adenovirus for osteosarcoma. Materials and Methods: E4rof6-deleted adenovirus (dl355) and human osteosarcoma cell lines U2OS and Saos2 were used in this study. Cell viability assays were carried out to evaluate the cytotoxicity and synergism of dl355 and RT combination. Chou and Talalay’s median-effect method was used to calculate the combination index. CPE assay was used to assess the cytopathic effect of the combination. Viral replication with or without radiation combination was investigated by hexon staining. Western blot analysis was performed to examine viral protein expression. Results: We found that RT treatment enhanced the cytoplasmic relocalization of HuR; thus irradiation up-regulated the propagations of dl355. Also, radiation-induced upregulation of viral protein expression was observed by western blotting. The RT and dl355 combination treatment increased the cytolysis of U2OS, and Saos2 cells in a synergistic manner compared to RT or virus only. Conclusion: Radiotherapy up-regulated of oncolytic adenovirus, which grows using the ARE-mRNA stabilization system, and this cytolytic effect provides a rationale for this combination. This combination approach has the possibility of a promising strategy for osteosarcoma.

Citation Format: Elora Hossain, Fumihiro Higashino. Radiation therapy enhances the potential of the oncolytic virus in the treatment of osteosarcoma [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-082.

Advantages of Using Paclitaxel in Combination with Oncolytic Adenovirus Utilizing RNA Destabilization Mechanism

Oncolytic virotherapy is a novel approach to cancer therapy. Ad-fosARE is a conditionally replicative adenovirus engineered by inserting AU-rich elements (ARE) in the 3'-untranslated region of the E1A gene. In this study, we examined the oncolytic activity of Ad-fosARE and used it in a synergistic combination with the chemotherapeutic agent paclitaxel (PTX) for treating cancer cells. The expression of E1A was high in cancer cells due to stabilized E1A-ARE mRNA. As a result, the efficiency of its replication and cytolytic activity in cancer cells was higher than in normal cells. PTX treatment increased the cytoplasmic HuR relocalization in cancer cells, enhanced viral replication through elevated E1A expression, and upregulated CAR (Coxsackie-adenovirus receptor) required for viral uptake. Furthermore, PTX altered the instability of microtubules by acetylation and detyrosination, which is essential for viral internalization and trafficking to the nucleus. These results indicate that PTX can provide multiple advantages to the efficacy of Ad-fosARE both in vitro and in vivo, and provides a basis for designing novel clinical trials. Thus, this virus has a lot of benefits that are not found in other oncolytic viruses. The virus also has the potential for treating PXT-resistant cancers.

HuR translocation to the cytoplasm of cancer cells in actin-independent manner

Human antigen R (HuR) is a RNA-binding protein, which binds to the AU-rich element (ARE) in the 3'-untranslated region (3'-UTR) of certain mRNA and is involved in the export and stabilization of ARE-mRNA. HuR constitutively relocates to the cytoplasm in many cancer cells, however the mechanism of intracellular HuR trafficking is poorly understood. To address this question, we examined the functional role of the cytoskeleton in HuR relocalization. We tested the effect of actin depolymerizing macrolide latrunculin A or myosin II ATPase activity inhibitor blebbistatin for HuR relocalization induced by the vasoactive hormone Angiotensin II in cancer and control normal cells. Western blot and confocal imaging data revealed that both inhibitors attenuated the cytoplasmic HuR in normal cells but no such alteration was observed in cancer cells. Concomitant with changes in intracellular HuR localization, both inhibitors markedly decreased the accumulation and half-lives of HuR target ARE-mRNAs in normal cells, whereas no change was observed in cancer cells. Furthermore, co-immunoprecipitation experiments with HuR proteins revealed clear physical interaction with ß-actin only in normal cells. The current study is the first to verify that cancer cells can implicate a microfilament independent HuR transport. We hypothesized that when cytoskeleton structure is impaired, cancer cells can acquire an alternative HuR trafficking strategy.

Adenovirus infection induces HuR relocalization to facilitate virus replication

HuR is an RNA-binding protein of the embryonic lethal abnormal vision (ELAV) family, which binds to the AU-rich element (ARE) in the 3'-untranslated region (UTR) of certain mRNAs and is involved in the nucleo-cytoplasmic export and stabilization of ARE-mRNAs. The cytoplasmic relocalization of ARE-mRNAs with several proteins such as HuR and pp32 increases in cells transformed by the adenovirus oncogene product E4orf6. Additionally, these ARE-mRNAs were stabilized and acquired the potential to transform cells. Although, the relocalization of HuR and the stabilization of ARE-mRNAs are crucial for cell transformation, evidence regarding the relationship of HuR and ARE-mRNAs with adenovirus replication is lacking. In this report, we demonstrate that adenovirus infection induces the relocation of HuR to the cytoplasm of host cells. Analysis using the luciferase-ARE fusion gene and the tetracycline (tet)-off system revealed that the process of stabilizing ARE-mRNAs is activated in adenovirus-infected cells. Heat shock treatment or knockdown-mediated depletion of HuR reduced adenovirus production. Furthermore, expression of ARE-including viral IVa2 mRNA, decreased in HuR-depleted infected cells. These results indicate that HuR plays an important role in adenovirus replication, at least in part, by up-regulating IVa2 mRNA expression and that ARE-mRNA stabilization is required for both transformation and virus replication.

ALDH1 and podoplanin expression patterns predict the risk of malignant transformation in oral leukoplakia

Oral leukoplakia (OL) is a clinically diagnosed preneoplastic lesion of the oral cavity with an increased oral cancer risk. However, the risk of malignant transformation is still difficult to assess. The objective of the present study was to examine the expression patterns of aldehyde dehydrogenase 1 (ALDH1) and podoplanin in OL, and to determine their roles in predicting oral cancer development. In the present study, the expression patterns of ALDH1 and podoplanin were determined in samples from 79 patients with OL. The association between protein expression and clinicopathological parameters, including oral cancer-free survival, was analyzed during a mean follow-up period of 3.4 years. Expression of ALDH1 and podoplanin was observed in 61 and 67% patients, respectively. Kaplan-Meier analysis demonstrated that the expression of the proteins was correlated with the risk of progression to oral cancer. Multivariate analysis revealed that expression of ALDH1 and podoplanin was associated with 3.02- and 2.62-fold increased risk of malignant transformation, respectively. The malignant transformation risk of OL was considerably higher in cases with expression of both proteins. Point-prevalence analysis revealed that 66% of patients with co-expression of ALDH1 and podoplanin developed oral cancer. Taken together, our data indicate that ALDH1 and podoplanin expression patterns in OL are associated with oral cancer development, suggesting that ALDH1 and podoplanin may be useful biomarkers to identify OL patients with a substantially high oral cancer risk.

HuR and podoplanin expression is associated with a high risk of malignant transformation in patients with oral preneoplastic lesions

The risk of malignant transformation in oral preneoplastic lesions (OPLs) is challenging to assess. The objective of the present study was to determine the expression of ELAV like RNA binding protein 1 (HuR) and podoplanin in OPLs, and to evaluate the use of each protein as biomarkers for the risk assessment of malignant transformations. Immunohistochemistry for HuR and podoplanin was performed on the tissues of 51 patients with OPL, including cases of low grade dysplasia (LGD) and high grade dysplasia (HGD). The association between the protein expression patterns and clinicopathological parameters, including oral cancer free survival (OCFS) time, was analyzed during the follow-up period. HuR and podoplanin expression was observed in 28 (55%) and 36 (71%) of 51 patients, respectively. Kaplan-Meier analysis showed that the expression of HuR and podoplanin was associated with the risk of progression to oral cancer (P<0.05). Multivariate analysis revealed that HuR and podoplanin expression was associated with a 2.93-fold (95% confidence interval (CI), 0.98–10.34; P=0.055) and 2.06-fold (95% CI, 0.55–8.01; P=0.283) increase in risk of malignant transformation, respectively. The risk of OPL malignant transformation was considerably increased with the coexpression of HuR and podoplanin compared with the histological grading (95% CI, 1.64–23.59; P=0.005). The results of the present study demonstrated that the expression of HuR and podoplanin associates with malignant transformation and suggests that the proteins may be used as biomarkers to identify OPL patients with an increased risk of cancer development.

Cytoplasmic expression of HuR may be a valuable diagnostic tool for determining the potential for malignant transformation of oral verrucous borderline lesions

Oral verrucous carcinoma (OVC) is a low grade variant of oral squamous cell carcinoma, and oral verrucous hyperplasia (OVH) is a benign lesion without malignant features. However, pathologists are sometimes presented with borderline lesions and are indecisive as to diagnose them as benign or malignant. Thus, these lesions are tentatively termed oral verrucous lesions (OVLs). HuR is an ARE mRNA-binding protein, normally localized in the nucleus but cytoplasmic exportation is frequently observed in cancer cells. The present study aimed to elucidate whether expression of the HuR protein facilitates the diagnosis of true malignant lesions. Clinicopathological features were evaluated, and immunohistochemical analysis for p53, Ki67 and HuR proteins was performed in 48 cases of OVH, OVC and OVL, and the outcomes were correlated using appropriate statistical analysis. The association of these three proteins in relation to malignant transformation was analyzed after a 3-year follow-up of 25 OVL cases. The basal characteristics (age, gender and location) of all cases had no significant association with the types of lesions. Gingiva (39.4%) was the common site for all lesions. Distribution of the examined proteins had a significant association with the lesions. As compared with the OVLs, the number of immunostained-positive cells was significantly higher in the OVCs and lower in the OVH cases. During follow-up, 24% of the OVLs underwent malignant transformation for which high HuR expression and a diffuse staining pattern in the epithelium were observed. Taken together, the high degree of HuR expression with diffuse staining pattern in the epithelium may be an effective diagnostic tool that determines the potential of OVLs for malignant transformation.

pp32r1 controls the decay of the RNA-binding protein HuR

pp32 is a tumor suppressor and is one of the associated proteins of the RNA-binding protein HuR. The pp32-HuR complex is exported to the cytoplasm of cells under stress conditions, and HuR is degraded by caspases in the cytoplasm. In the present study, we examined the role of pp32r1, a member of the pp32 family that has oncogenic properties, in the decay of HuR. pp32r1 was found to be abundantly expressed in cancer cells, and overexpression of pp32r1 induced colony formation in soft-agar. pp32r1 was expressed in both the nucleus and cytoplasm, whereas pp32 was predominantly localized in the nucleus. Even with lethal stress such as staurosporine (STS), HuR in the cytoplasm was never downregulated, and caspase-3 activity was inhibited when cells expressed pp32r1. pp32r1 bound to HuR without interacting with pp32. In cancer cells, HuR survived in the cytoplasm of cells overexpressing pp32r1, although HuR was not expressed in the cytoplasm of pp32-expressing cells, similar to lethal stress conditions. Taken together, these results indicate that pp32r1 binds to HuR to avoid the caspase-mediated decay of HuR in the cytoplasm of cells. We suggest that this function contributes to the oncogenic activity of pp32r1.

Expression of parathyroid hormone-related protein confers malignant potential to mucoepidermoid carcinoma

Parathyroid hormone-related protein (PTHrP) is known to induce bone resorption by activating RANKL as well as PTH. PTHrP plays a central role in humoral hypercalcemia, and its expression has been reported to be closely associated with bone metastasis of breast carcinoma. PTHrP expression in oral squamous carcinoma cell lines was investigated, and PTHrP was expressed in oral squamous cell carcinoma cell lines similar to that in a prostate carcinoma cell line. Mucoepidermoid carcinoma is the most common malignant salivary gland tumor composed of different types of cells including a squamous component. Its clinical behavior is highly variable and ranges from slow-growing and indolent to locally aggressive and highly metastatic. We examined the PTHrP expression in mucoepidermoid carcinoma and assessed the significance of its correlation with clinicopathological features. Immunohistochemical detection of PTHrP was carried out in 21 cases of mucoepidermoid carcinoma in the head and neck region. PTHrP was highly detectable in intermediate and epidermoid cells, and abundant expression of PTHrP in intermediate cells had a significant association with cancer malignancy, including lymph node metastasis and/or tumor recurrence. These results suggest that PTHrP expression can be used as a prognostic factor for mucoepidermoid carcinoma.

Pim-1 activation of cell motility induces the malignant phenotype of tongue carcinoma

Pim-1 is a serine/threonine kinase as well as a proto-oncogene that induces T-cell lymphoma. Pim-1 induces cell cycle progression in cooperation with c-Myc and acts as an inhibitor of apoptotic cell death, actions that are involved in blood cell oncogenesis. However, little is known regarding the role of Pim-1 in oral carcinogenesis. We investigated Pim-1 expression in tongue squamous cell carcinoma (SCC) and examined its clinicopathological features. Western blotting was performed in 6 oral SCC cell lines, with Pim-1 being detected in all 6 of the lines. Immunohistochemical detection of Pim-1 was carried out in 39 cases of tongue SCC and analyzed in terms of its associated clinicopathological features. Pim-1 was expressed in 17/39 cases of tongue carcinoma, and was significantly correlated with lymph node metastasis. The role of Pim-1 in cell motility was further examined in HSC3 cells using the GTP-binding assay for Rho family protein, the motility assay and siRNA treatment. Rac1 activation was observed, and cell motility was reduced when Pim-1 was knocked down by siRNA. These results indicate that Pim-1 is involved in the carcinogenesis of oral SCC and is correlated to metastasis, which is in part associated with the enhancement of cell motility.

Phenotype of tumor lymphatic vessels is a prognostic factor in human tongue squamous cell carcinoma

Tumor metastasis to lymph nodes occurs through the lymphatic vessels located in the tumor circumference. However, few studies have focused on the phenotypes of lymphatic vessels around these tumors. We investigated the characteristics of the lymph vessels of tongue squamous cell carcinoma (SCC) and compared them to clinicopathological characteristics. A total of 43 patients diagnosed as having tongue SCC consulted Hokkaido University Hospital were examined. The lymphatic vessels were identified by antibody D2-40 and the number and diameter of tumor lymphatic vessels were measured. The proliferative activity of lymphatic endothelial cells was also examined by immunostaining using antibody MIB-1. We then measured the DNA density of lymphatic endothelial cells in normal and tumor tissues. The number of tumor lymphatic vessels significantly increased in highly metastatic cases of tongue SCC, particularly in cases with a large number of micro lymphatic vessels. A significant correlation was found between the metastatic and proliferative activity of tumor lymphatic endothelial cells. Moreover, the DNA density of tumor lymphatic endothelial cells increased compared to normal tissues. These results suggest that the phenotypes of tumor lymphatic endothelial cells are an indicator of lymph node metastasis of tongue SCC.

HuR knockdown changes the oncogenic potential of oral cancer cells

HuR binds to AU-rich element-containing mRNA to protect them from rapid degradation. Here, we show that knockdown of HuR changes the oncogenic properties of oral cancer cells. Oral squamous cell carcinoma cell lines, HSC-3 and Ca9.22, which express HuR protein and cytoplasmic AU-rich element mRNA more abundantly than normal cells, were subjected to HuR knockdown. In the HuR-knockdown cancer cells, the cytoplasmic expression of c-fos, c-myc, and COX-2 mRNAs was inhibited compared with those in cells that had been transfected with a control small interfering RNA, and the half-lives of these mRNAs were shorter than those of their counterparts in the control cells. HuR-knockdown cells failed to make colonies in soft agar, suggesting that the cells had lost their ability for anchorage-independent cell growth. Additionally, the motile and invasive activities of the cells decreased remarkably by HuR knockdown. Furthermore, the expression of cell cycle-related proteins, such as cyclin A, cyclin B1, cyclin D1, and cyclin-dependent kinase 1, was reduced in HuR-knockdown cancer cells, and HuR bound to cdk1 mRNA to stabilize it. These findings suggest that HuR knockdown changes the features of oral cancer cells, at least in part, by affecting their cell cycle and shows potential as an effective therapeutic approach.

HuR is exported to the cytoplasm in oral cancer cells in a different manner from that of normal cells

HuR, a ubiquitously expressed member of the Hu protein family that binds and stabilizes an AU-rich element (ARE)-containing mRNAs, is known to shuttle between the nucleus and the cytoplasm via several export pathways. When normal cells were treated with heat shock, HuR was exported to the cytoplasm in a chromosome maintenance region 1 (CRM1)-dependent manner. However, in this study, we demonstrate that HuR is exported to the cytoplasm in oral cancer cells even if the cells were treated with the inhibitor of the CRM1-independent export pathway. Immunohistochemical and biochemical analyses showed that HuR existed in both the cytoplasm and the nucleus in oral cancer cells, such as HSC-3 and Ca9.22, but existed entirely inside the nucleus in normal cells. AU-rich element-mRNAs were also exported to the cytoplasm and stabilised in the oral cancer cells, which were inhibited by HuR knockdown. This export of HuR was not affected by at least 7 h of treatment of leptomycin B (LMB), which is an inhibitor of the CRM1-dependent export pathway. These findings suggest that HuR is exported to the cytoplasm in oral carcinoma cells in a different manner from that of normal cells, and is likely to occur through the perturbation of a normal export pathway.

Expression of E1AF, an ets-oncogene transcription factor, highly correlates with malignant phenotype of malignant melanoma through up-regulation of the membrane-type-1 matrix metalloproteinase gene

Matrix metalloproteinase (MMP) is closely involved in the degradation of extracellular matrix and confers invasive and metastatic potential to malignant tumors. MMP-2 is a type-IV collagenase secreted as a proenzyme that is activated on the surface of the tumor cell by membrane-type 1-MMP (MT1-MMP). MT1-MMP plays a critical role during tumor progression and metastasis. We investigated the expression levels of E1AF and MT1-MMP in malignant melanoma cell lines and specimens from patients in order to clarify the mechanisms responsible for the invasion and metastasis of malignant melanoma. High levels of E1AF and MT1-MMP mRNA expression were observed in melanoma cells by Northern blotting and real-time PCR. The expression level was highly correlated with an invasive potential determined by an in vitro invasion assay. The down-regulation of MT1-MMP was identified when E1AF was knocked down by RNA interference. These results suggest that E1AF plays a crucial role in the invasion and metastasis of malignant melanoma through up-regulating the MT1-MMP expression.

Synergistic up-regulation of Hexokinase-2, glucose transporters and angiogenic factors in pancreatic cancer cells by glucose deprivation and hypoxia

There is accumulating evidence demonstrating that HIF-1 functions as a key regulator of the adaptation responses to hypoxia in cancer tissues. To this evidence, we add that adaptation responses to glucose deprivation plus hypoxia are also necessary for the survival of tumor cells in the tumor microenvironment as cancer tissues are exposed to glucose deprivation as well as hypoxia. We found that adrenomedullin (AM), VEGF, Glut-1, Glut-3, and Hexokinase-2 among 45 hypoxia-inducible genes investigated were expressed at higher levels under glucose-deprived hypoxic conditions than under hypoxic conditions. Glucose deprivation activated the AMPK under normoxia and hypoxia. Compound C, an inhibitor of AMPK, suppressed the expressions of AM and VEGF which had already been enhanced under glucose-deprived hypoxic conditions. siRNAs for both AMPKalpha1 and AMPKalpha2 suppressed the expressions of AM and VEGF. HIF-1alpha protein level and the transcriptional activity of HIF-1 under glucose-deprived hypoxic conditions were thus found to be similar to those under hypoxic conditions. Furthermore, tumor cells in 15 out of 20 human pancreatic cancer tissue specimens were stained by anti-phospho-AMPKalpha antibody. Our results thus suggest that the enhanced expressions of those genes mediated by the activation of AMPK and HIF-1 therefore play a pivotal role in the tumor formation of pancreatic cancers.

Enhanced expression of asparagine synthetase under glucose-deprived conditions protects pancreatic cancer cells from apoptosis induced by glucose deprivation and cisplatin

Although hypovasculature is an outstanding characteristic of pancreatic cancers, the tumor cells survive and proliferate under severe hypoxic, glucose-deprived conditions caused by low blood supply. It is well known that the hypoxia-inducible factor-1 pathway is essential for the survival of pancreatic cancer cells under hypoxic conditions. To discover how pancreatic cancer cells adapt to glucose deprivation as well as hypoxia, we sought glucose deprivation-inducible genes by means of a DNA microarray system. We identified 63 genes whose expression was enhanced under glucose-deprived conditions at >2-fold higher levels than under normal glucose conditions. Among these genes, asparagine synthetase (ASNS) was studied in detail. Although it is known to be associated with drug resistance in leukemia and oncogenesis triggered by mutated p53, its function is yet to be determined. In this study, we found that glucose deprivation induced the overexpression of ASNS through an AMP-activated protein kinase-independent and activating transcription factor-4-dependent manner and that ASNS protects pancreatic cancer cells from apoptosis induced by glucose deprivation itself. ASNS overexpression also induced resistance to apoptosis triggered by cisplatin [cis-diammine-dichloroplatinum (CDDP)] and carboplatin, but not by 5-fluorouracil, paclitaxel, etoposide, or gemcitabine. We show that glucose deprivation induces the activation of c-jun NH(2)-terminal kinase (JNK)/stress-activated protein kinase (SAPK) in a mock transfectant but not in an ASNS transfectant. Consequently, an inhibitor of JNK/SAPK decreased the sensitivity of pancreatic cancer cells to apoptosis by glucose deprivation and CDDP. These results strongly suggest that ASNS is induced by glucose deprivation and may play a pivotal role in the survival of pancreatic cancer cells under glucose-deprived conditions.

Adenovirus E1A negatively regulates E1AF, an ets family of the protein

E1AF was first identified as a transcription factor that binds to enhancer motifs of the adenovirus E1A gene and is thought to be a human homologue of mouse PEA3, one of the ets oncoprotein families. Here we show the effect of E1A on the gene expression and function of E1AF. E1A repressed the activity of E1AF promoter, and the N-terminal region of E1A, which is involved in the oncogenic activity of E1A, was essential for this repression. The ability as a transcription factor of E1AF, as well as those of the other PEA3 subfamily members ER81 and ERM, was also repressed by E1A via the same oncogenic domain. Furthermore, E1AF repressed the transformation activity of E1A cooperating with E1B, whereas the other ets family Ets-1 enhanced this activity. These results suggest that E1AF is one of the targets of E1A.

Suppression of tumor growth by intra-muscular transfer of naked DNA encoding adrenomedullin antagonist

We have recently reported that the intra-tumoral injection of adrenomedullin (AM) antagonist (AMA; AM (22-52)) peptides significantly reduced the in vivo growth of a pancreatic cancer cell line in severely combined immunodeficient (SCID) mice. In the present study, we examined the effects of intra-tumoral and intra-muscular transfers of naked DNA encoding AMA on the in vivo growth of cancer cell lines. We demonstrate that these treatments induce the regression of a pancreatic cancer cell line and a breast cancer cell line inoculated in SCID mice. Furthermore, CD31-positive cells disappear completely from tumor tissues, following treatment, indicating that neo-vascularization is entirely inhibited. These results suggest that the intra-tumoral or intra-muscular transfer of naked DNA encoding AMA might be a promising alternative modality for treating human cancers.

Genomic structure and promoter activity of the E1AF gene, a member of the ETS oncogene family

E1AF is a member of the ETS oncogene family and is thought to be a human homologue of mouse PEA3. We have isolated a genomic clone of E1AF and analyzed the promoter activity of its 5'-flanking region. We identified a variation in exon 1, which depends on the cell type. There was no typical TATA box in the 5'-flanking region, but putative binding sites of a number of transcription factors including PEA3 as well as CAAT boxes were seen. A luciferase reporter assay indicated that the 5'-flanking region possesses promoter activity. Northern blot studies demonstrated significant expression of the E1AF gene in restricted tissues such as the pituitary gland, placenta, and fetal kidney. Moreover, the E1AF promoter was activated by E1AF itself and estrogen receptor. These findings suggest that E1AF is a housekeeping gene, whose expression is controlled in specific tissues.

Adenovirus E4orf6 targets pp32/LANP to control the fate of ARE-containing mRNAs by perturbing the CRM1-dependent mechanism

E4orf6 plays an important role in the transportation of cellular and viral mRNAs and is known as an oncogene product of adenovirus. Here, we show that E4orf6 interacts with pp32/leucine-rich acidic nuclear protein (LANP). E4orf6 exports pp32/LANP from the nucleus to the cytoplasm with its binding partner, HuR, which binds to an AU-rich element (ARE) present within many protooncogene and cytokine mRNAs. We found that ARE-mRNAs, such as c-fos, c-myc, and cyclooxygenase-2, were also exported to and stabilized in the cytoplasm of E4orf6-expressing cells. The oncodomain of E4orf6 was necessary for both binding to pp32/LANP and effect for ARE-mRNA. C-fos mRNA was exported together with E4orf6, E1B-55kD, pp32/LANP, and HuR proteins. Moreover, inhibition of the CRM1-dependent export pathway failed to block the export of ARE-mRNAs mediated by E4orf6. Thus, E4orf6 interacts with pp32/LANP to modulate the fate of ARE-mRNAs by altering the CRM1-dependent export pathway.

E1AF expression is closely correlated with malignant phenotype of tongue squamous cell carcinoma through activation of MT1-MMP gene promoters

E1AF is an ets-oncogene family transcription factor that has been shown to up-regulate multiple MMPs whereas MMP-2, a potent extracellular matrix degrading enzyme, is not up-regulated. We investigated the activation mechanism of MMP-2 in oral squamous cell carcinoma. Chloramphenicol acetyltransferase (CAT) assay was utilized to investigate whether E1AF is able to up-regulate membrane type-1 matrix metalloproteinase (MT1-MMP), which is known to activate MMP-2. Expression of the CAT reporter gene under the control of the MT1-MMP promoter was increased approximately 40-fold by co-transfection with the E1AF expression vector. Real-time RT-PCR study was carried out in 25 patients with tongue squamous cell carcinoma, and the mRNA expression level of E1AF and MT1-MMP was synergistically increased. These results indicate that E1AF positively regulates transcription from MT1-MMP genes, which plays an important role in invasion and metastasis of squamous cell carcinoma of the tongue by converting pro-MMP-2 into active-MMP-2.

E1AF degradation by a ubiquitin-proteasome pathway

E1AF is a member of the ETS family of transcription factors. In mammary tumors, overexpression of E1AF is associated with tumorigenesis, but E1AF protein has hardly been detected and its degradation mechanism is not yet clear. Here we show that E1AF protein is stabilized by treatment with the 26S protease inhibitor MG132. We found that E1AF was modified by ubiquitin through the C-terminal region and ubiquitinated E1AF aggregated in nuclear dots, and that the inhibition of proteasome-activated transcription from E1AF target promoters. These results suggest that E1AF is degraded via the ubiquitin-proteasome pathway, which has some effect on E1AF function.

E1AF, an ets-oncogene family transcription factor

E1AF is an ets-oncogene family transcription factor. E1AF was shown to upregulate multiple matrix metalloproteinase (MMP) genes and contribute to the malignant phenotype of cancer cells by inducing invasive and metastatic activities. E1AF is upregulated by hepatocyte growth factor (HGF) stimulation, which indicates that E1AF would participate in cell motility by HGF/scatter factor. On the other hand, E1AF upregulates p21waf1/cip1 to induce cell cycle arrest when cells are exposed to stress. EWS/ETS fusions are frequently observed in Ewing's sarcoma, and we have revealed that EWS/ETS chimeric protein activates telomerase activity by upregulating hTERT. However, substitution ets binding site (EBS) mutants did not affect the responsiveness to EWS/E1AF. DNA-IP assay showed that the complexes contained EWS/E1AF bound to the hTERT promoter, which suggested that EWS/ETS functions as a co-activator for TERT transcription. Our findings that EWS/ETS acts as a transcriptional co-factor may imply that the transcription pathway is regulated by the interaction of transcription factors.

Bisphenol A from dental polycarbonate crown upregulates the expression of hTERT

Bisphenol A (BPA) is one of the endocrine-disrupting chemicals (EDCs) that possess estrogen-like biologic activity. Many dental materials have been reported to release BPA. However, there are few reports available on the release of BPA from dental polycarbonates. The purpose of this study was to investigate the release of BPA from dental polycarbonate crowns and to evaluate the estrogenic activity of BPA. Polycarbonate crowns were immersed in five solvents (water, ethanol, n-hepthane, acetic acid, and acetonitrile) at 37 or 65 degrees C for 24 h. The elution from the material was analyzed by high-performance liquid-chromatography (HPLC) and mass-spectrometry (MS) analysis. BPA release was detected corresponding to the degradation of dental polycarbonates under the some storage conditions (ethanol, acetic acid, and acetonitrile). A previous report proved that estrogen increased human telomerase catalytic subunit (hTERT) mRNA, whereas the effect of EDCs on the hTERT promoter has never been reported. The estrogenic activity of BPA was analyzed by luciferase assay with the use of the hTERT promoter. This assay revealed that BPA was a positive regulator of hTERT transcription. In addition, quantitative real-time PCR analysis showed that BPA increased the expression level of hTERT mRNA in MCF7 cells. Herein, it is demonstrated that hTERT is a new target of BPA.

EWS/ETS fusions activate telomerase in Ewing's tumors

EWS/ETS is a chimeric protein identified in most Ewing's sarcomas. Although EWS/ETS has been shown to activate transcription as a transcription factor, the detailed targets of EWS/ETS in transformed cells have not been clarified. Herein, we demonstrate that telomerase is a new target of EWS/ETS fusions. Both telomerase activity and the expression level of telomerase reverse transcriptase (TERT) mRNA were up-regulated in NIH3T3 cells transformed by EWS/E1AF and EWS/FLI1 as well as in two Ewing's sarcoma cell lines. Luciferase assay using the TERT promoter revealed that EWS/E1AF and EWS/FLI1 function as positive regulators of TERT transcription in an ETS binding site-independent manner. EWS/ETS appeared to be included in the initiation complex of TERT transcription and to cooperate with CREB-binding protein (CBP)/p300. When EWS/FLI1 was knocked down in Ewing's sarcomas cells by RNA interference, the expression level of TERT mRNA and the telomerase activity were significantly decreased. These findings indicate that EWS/ETS fusion proteins activate human telomerase activity in Ewing's tumors through up-regulation of TERT gene expression, probably as a transcriptional coactivator.

Nuclear export of adenovirus E4orf6 protein is necessary for its ability to antagonize apoptotic activity of BH3-only proteins

The adenovirus E4orf6 is a viral oncoprotein known to cooperate with the E1A gene product in transforming primary murine cells. It has been shown to inhibit the apoptotic activities of p53 and p73 through direct binding to these proteins. Here, we demonstrate that the adenovirus E4orf6 protein inhibits apoptosis mediated by BNIP3 and Bik, which are BH3-only proteins of the Bcl-2 family. This activity was not mediated by p53 and p73 because E4orf6 had the same effect on the apoptosis in Saos-2 cells that do not express p53-related genes. It was also ascertained that E4orf6 could change the mitochondrial localization of BNIP3 and Bik. A mutant lacking the nuclear export signal of E4orf6 failed to inhibit apoptosis and to translocate BNIP3 protein from the mitochondria. Moreover, it was also established that E4orf6 was able to interact with BNIP3 and Bik. In BNIP3 protein, the region required for the interaction included the transmembrane domain, which is required for the localization of BNIP3 to the mitochondria. These results suggest that E4orf6 is exported from the nucleus to the cytoplasm, enabling it to interact with BH3-only proteins, eventually leading to the inhibition of apoptotic activity.

Dominant-negative hypoxia-inducible factor-1 alpha reduces tumorigenicity of pancreatic cancer cells through the suppression of glucose metabolism

In the tumor cells exposed to hypoxia, hypoxia-inducible factor-1 (HIF-1)-mediated adaptation responses such as angiogenesis and anaerobic metabolism are induced for their survival. We have recently reported that the constitutive expression of HIF-1 alpha renders pancreatic cancer cells resistant to apoptosis induced by hypoxia and glucose deprivation. We then established dominant-negative HIF-1 alpha (dnHIF-1 alpha) transfectants and examined their susceptibility to apoptosis and growth inhibition induced by hypoxia and glucose deprivation in vitro and their tumorigenicity in SCID mice. We further examined the expressions of aldolase A and Glut-1 in vitro and Glut-1 expression and glucose uptake in the tumor tissues and microvessel counts in the tumor tissues. As a result, dnHIF-1 alpha rendered the pancreatic cancer cells sensitive to apoptosis and growth inhibition induced by hypoxia and glucose deprivation. Also it abrogated the enhanced expression of Glut-1 and aldolase A mRNAs under hypoxia and reduced the expression of Glut-1 and the glucose uptake in the tumor tissues and consequently in vivo tumorigenicity. We found no significant difference in the microvessel counts among the tumor tissues. From these results, we suggest that the disruption of the HIF-1 pathway might be effective in the treatment of pancreatic cancers.

Adrenomedullin antagonist suppresses in vivo growth of human pancreatic cancer cells in SCID mice by suppressing angiogenesis

Since it is reported that adrenomedullin (AM) upregulated by hypoxia inhibits hypoxic cell death, we examined the effects of AM antagonist (AM C-terminal fragment; AM(22-52)) on the growth of pancreatic cancer cells. We, for the first time, demonstrated that AM antagonist significantly reduced the in vivo growth of the pancreatic cancer cell line. Immunohistochemical analysis demonstrated that the mean diameter of blood vessels was significantly smaller in the tumor tissues treated with AM antagonist than in those treated with AM N-terminal fragment (AM(1-25)), and that the PCNA-labeling index was lower in the former than in the latter. Then we demonstrated that AM antagonist showed no effect on the in vitro growth of the pancreatic cancer cell line. These results showed that AM played an important role in the growth of pancreatic cancer cells in vivo, suggesting that AM antagonist might be a useful tool for treating pancreatic cancers.

Increased pre-therapeutic serum vascular endothelial growth factor in patients with early clinical relapse of osteosarcoma

To investigate the clinical significance of circulating angiogenic factors, especially in association with early relapse of osteosarcoma, we quantified pre-therapeutic levels of vascular endothelial growth factor, basic fibroblast growth factor and placenta growth factor in the sera of 16 patients with osteosarcoma using an enzyme-linked immunosorbent assay. After a 1-year follow-up, the serum level of angiogenic factors was analysed with respect to microvessel density of the biopsy specimen and clinical disease relapse. The serum vascular endothelial growth factor levels were positively correlated with the microvessel density with statistical significance (P=0.004; Spearman rank correlation) and also significantly higher in seven patients who developed pulmonary metastasis than the remaining nine patients without detectable disease relapse (P=0.0009; The Mann-Whitney U-test). In contrast, the serum levels of basic fibroblast growth factor or placenta growth factor failed to show significant correlation with the microvessel density or relapse of the disease. Although there was no significant correlation between serum vascular endothelial growth factor levels and the tumour volume, the serum vascular endothelial growth factor levels were significantly higher in patients with a vascular endothelial growth factor-positive tumour than those with a vascular endothelial growth factor-negative tumour. These findings suggest that the pre-therapeutic serum vascular endothelial growth factor level reflects the angiogenic property of primary tumour and may have a predictive value on early disease relapse of osteosarcoma.

nm23-H1 suppresses invasion of oral squamous cell carcinoma-derived cell lines without modifying matrix metalloproteinase-2 and matrix metalloproteinase-9 expression

nm23-H1 is a candidate gene for the suppression of cancer metastasis. Several studies on human breast, hepatocellular, gastric, ovarian, and colon carcinomas and melanomas have shown that reduced nm23-H1 expression was closely related to metastatic progression with poor prognosis. However, the biochemical mechanism by which nm23-H1 suppresses the metastasis has yet to be elucidated. In this study, we analyzed the correlation between nm23 expression, cell motility, and the invasive abilities of six different oral squamous cell carcinoma cell lines (HSC2, HSC3, HSC4, KB, OSC19, and OSC20). Reduced mRNA/protein expression of the nm23-H1 was observed in three cell lines (HSC2, HSC3, and HSC4). These cell lines exhibited increased cell motility and an invasive character on organotypic raft culture. On the other hand, the cell lines (KB, OSC19, and OSC20) that showed a higher expression of nm23-H1 exhibited a threefold to fivefold reduced motility and also reflected fewer invasions compared to the former three cell lines. Because the HSC3 cells demonstrated the lowest nm23-H1 expression with the highest cell motility and invasive character, we established nm23-H1-transfected HSC3 cell lines to investigate whether exogenous nm23-H1 protein could inhibit cell migration and invasive activity. These transfectants showed a significant reduction in cell motility with exogenous nm23-H1 in a dose-dependent manner, and exhibited a noninvasive character. An immunofluorescence study demonstrated a distinct stress-fiber distribution at peripheral region of these transfectants. However, no significant difference of matrix metalloproteinase (MMP)-2 and MMP-9 expression was observed between mock transfectant and nm23-H1-transfected cells. These findings suggest that nm23-H1 inhibits the invasive activity of oral squamous cell carcinoma by suppression of cell motility without altering the MMP-2 and MMP-9 status.

Monitoring of in vitro and in vivo translation of green fluorescent protein and its fusion proteins by fluorescence correlation spectroscopy

BACKGROUND

Because the process of protein translation is an event of sparse molecules, the measurement requires high sensitivity. One of the candidates for studying the molecules is fluorescence correlation spectroscopy (FCS), which gleans quantitative information from fluctuating fluorescence signals in a diluted solution.

METHODS

Using FCS, the translation products of expression plasmid for green fluorescent protein (GFP) and its fusion proteins were measured in vitro and in vivo.

RESULTS

In in vitro translation, the number of products increased linearly for 90 min upon concentration of the plasmid. The autocorrelation function for GFP was fitted with a one-component model with a diffusion time of 0.18 ms, which was identical to the value expected from the molecular weight. In the cases of GFP- tagged hypoxia-inducible factor-1 alpha and glucocorticoid receptor, each fitting result was significantly improved with a two-component model. The slow component with a diffusion time of 6 ms appeared to be related to the ribosome or polysome. In response to the addition of dexamethasone, the nuclear translocation from cytosol clearly induced the decrease in number of molecules in the focal point.

CONCLUSIONS

FCS permits monitoring of the number of molecules translated in vitro and in vivo, the translation rate, and the molecular weight.

BAG-1 expression correlates highly with the malignant potential in early lesions (T1 and T2) of oral squamous cell carcinoma

BAG-1 is a Bcl-2-binding protein that functions as an anti-apoptotic molecule. In this report we show a possible correlation between BAG-1 expression levels and the probability of oral squamous cell carcinoma (SCC) progression. We investigated BAG-1 expression levels in 22 patients diagnosed with early lesions (T1 and T2) of oral SCCs using immunohistochemistry and western blotting. High steady-state levels of BAG-1 were detected in 13 out of 22 cases (59%). High BAG-1 expression was observed more frequently in cases with nodal metastasis (89%) than in those without nodal metastasis (38%) (P<0. 03), suggesting that BAG-1 expression levels may correlate with the pathological stage of oral SCCs. Furthermore, BAG-1 expression levels correlated with the WHO grade, i.e. 45% in grade-I cases as opposed to 72% in grade-II cases (P<0.02). These data suggest that an analysis of BAG-1 expression may be useful in establishing a prognosis for patients with oral SCCs, and especially in predicting the metastatic potential of SSCs.

Membrane type 1-matrix metalloproteinase expression is regulated by E-cadherin through the suppression of mitogen-activated protein kinase cascade

To elucidate the role of E-cadherin in matrix metalloproteinases (MMPs) expression, we transfected to squamous carcinoma cells with E-cadherin cDNA. HN5 cells and mock-transfected HN5-neo cells expressed proMMP-2 and active MMP-2. E-cadherin-transfected HN5-EC cells produced comparable proMMP-2 but low active MMP-2; and membrane type 1-MMP (MT1-MMP) mRNA declined. Phosphorylated ERK, a marker of mitogen-activated protein (MAP) kinase cascade, also declined in HN5-EC cells. The addition of anti-E-cadherin antibody resulted in the disappearance of these alterations in HN5-EC cells. These results suggest that E-cadherin suppresses MAP kinase cascade and down-regulates MT1-MMP.

Hepatocyte growth factor upregulates E1AF that induces oral squamous cell carcinoma cell invasion by activating matrix metalloproteinase genes

Hepatocyte growth factor (HGF) is thought to play a role in cell motility and invasion. Matrix metalloproteinases (MMPs) have been implicated in invasion and metastasis of tumor cells. We have previously reported that the Ets-oncogene family transcription factor E1AF positively regulates transcription of MMP genes in transient expression assays and that overexpression of the E1AF gene confers an invasive phenotype on breast cancer cells. Here we examined the effect of HGF on E1AF and MMP gene expression in terms of the invasive potential of the oral squamous cell carcinoma cell line HSC3. HGF stimulated expression of the E1AF gene. The levels of MMP-1, -3 and -9 mRNAs increased in cells treated with HGF and correlated with E1AF upregulation. In contrast, no obvious upregulation of MMP-1 and -9 mRNA was observed in ASE1AFHSC3 cells transfected with the antisense E1AF expression vector into parental HSC3 cells. The wild-type MMP-9 gene promoter was activated by endogenous E1AF in HSC3 cells, and chloramphenicol acetyltransferase (CAT) activities increased when HGF was added to transfected cells. On the other hand, CAT activity was reduced to almost two-thirds of the wild-type activity when HSC3 cells were transfected with a CAT reporter plasmid driven by a mutant MMP-9 promoter lacking the Ets-binding site, and induction of CAT activity was not observed upon addition of HGF. Analysis of organotypic raft cultures revealed that HSC3 cells invaded and degraded collagen gel actively upon addition of HGF. These results suggest that HGF induces expression of the Ets-related E1AF transcription factor gene whose product in turn activates MMP genes and leads to oral cancer cell invasion.

Vascular endothelial growth factor expression in untreated osteosarcoma is predictive of pulmonary metastasis and poor prognosis

To investigate the clinical significance of vascular endothelial growth factor (VEGF) in osteosarcoma, we immunohistochemically stained biopsy specimens of 27 primary osteosarcomas using an antibody against VEGF and evaluated the correlation between the expression of VEGF and local density of CD34-positive microvessels, clinicopathological variables, and survival of patients. VEGF staining was positive in 17 tumors (63.0%) in which the density of CD34-positive microvessels was significantly higher than that in VEGF-negative 10 tumors (P < 0.05). In terms of clinicopathological variables, there was no correlation between the expression of VEGF and histological subtype, stage, or response to neoadjuvant chemotherapy, or, strikingly, to the development of pulmonary metastasis (89% of VEGF-positive tumors versus 10% of VEGF-negative tumors; P < 0.0003). Moreover, patients with a VEGF-positive tumor were poorer in both disease-free survival (P < 0.001) and overall survival (P < 0.03) compared to those with a VEGF-negative tumor. These findings strongly suggest that VEGF expression in untreated osteosarcoma is predictive of pulmonary metastasis and poor prognosis in patients who underwent aggressive therapy and also provide the basis for a therapeutic strategy targeting angiogeneic property of osteosarcoma.

Selective secretion of chemoattractants for haemopoietic progenitor cells by bone marrow endothelial cells: a possible role in homing of haemopoietic progenitor cells to bone marrow

To elucidate the mechanisms by which haemopoietic progenitor cells lodge in the bone marrow, we examined the secretion of chemoattractants for haemopoietic progenitor cells by bone marrow and lung endothelial cells. The bone marrow endothelial cells, but not lung endothelial cells, secreted chemoattractants for the haemopoietic progenitor cell line, FDCP-2, and normal haemopoietic progenitor cells. Checkerboard analysis demonstrated that the conditioned medium of the bone marrow endothelial cells had chemotactic activity and random motility-stimulating activity. The bone marrow endothelial cells expressed stromal-cell-derived factor-1 (SDF-1) mRNA and produced SDF-1 protein, whereas the lung endothelial cells did not. Adhesion of FDCP-2 cells to the bone marrow endothelial cells was partially inhibited by anti-SDF-1 antibody. These findings suggest that the chemoattractants for haemopoietic progenitor cells including SDF-1 and random motility-stimulating factor(s) selectively secreted by the bone marrow endothelial cells may contribute to the homing of haemopoietic progenitor cells to bone marrow.

Adenovirus E4orf6 oncoprotein modulates the function of the p53-related protein, p73

Recently, several proteins have been identified that are related in their sequence to the p53 tumor-suppressor protein. One of these proteins, which is termed p73, exhibits sequence homology to the p53 transcriptional activation, DNA binding, and oligomerization domains. The adenovirus E1B 55-kDa protein, the adenovirus E4orf6 protein, and SV40 T antigen each can bind to p53 and inhibit p53 function. Here we demonstrate that the adenovirus E4orf6 protein, but not the E1B 55-kDa protein or T antigen, interacts with p73. The E4orf6 protein inhibits p73-mediated transcriptional activation and cell killing in a manner similar to its effect on p53. Thus, only a subset of viral oncoproteins that antagonize p53 function also interacts with the related p73 protein.

Correlated expression of matrix metalloproteinases and ets family transcription factor E1A-F in invasive oral squamous-cell-carcinoma-derived cell lines

Matrix metalloproteinases (MMPs) have been implicated in invasion and metastasis of tumor cells. Transcription regulatory regions of MMP genes often contain binding sites for ets transcription factors. We recently isolated a cDNA encoding human E1A-F, a member of the ets oncogene family, and showed that E1A-F can upregulate MMP genes by CAT assay. We attempted to investigate the relationship between E1A-F mRNA expression and MMP protein expression in four different types of oral squamous-cell-carcinoma-derived cell lines (HSC 3, SAS, KB, and Ca 9.22). HSC 3 and SAS are highly invasive cell lines when they are injected in the tongue of nude mice. Raft culture of HSC 3 and SAS revealed the same characteristics as seen in tumors implanted in vivo. Both type I collagenase (MMP-1) and 92-kd type IV collagenase (MMP-9) were detected in cultured HSC 3 and SAS cells. E1A-F mRNA was demonstrated to be highly expressed in HSC 3 and SAS by Northern blotting, and in situ hybridization confirmed E1A-F mRNA expression at the invasion front of tumor cells seeded on collagen gel. On the other hand, KB and Ca 9.22 have little potential for invasion, and MMP-1 and MMP-9 protein and E1A-F mRNA could not be detected. These results suggest that the ets-related E1A-F participates in the regulation of invasion-associated MMP genes and is involved in presenting invasive activity in tumor cells of oral squamous cell carcinoma.

Fusion of an ETS-family gene, EIAF, to EWS by t(17;22)(q12;q12) chromosome translocation in an undifferentiated sarcoma of infancy

EIAF is a newly isolated ETS-family gene that is located on 17q21 and codes for the adenovirus EIA enhancer-binding protein. In our chromosome analysis of 18 of the Ewing family of tumors and undifferentiated sarcomas, we found t(17;22)(q12;q12) in an MIC2 antigen-positive undifferentiated sarcoma of infancy. On Southern blot analysis, EWS and EIAF cDNA probes hybridized to the same rearranged band, indicating that an EWS-EIAF fusion gene was formed in the tumor. Further Southern blot analysis using four EIAF cDNA probes of different sizes showed that the breakpoint lies in the region upstream to the ETS domain of the EIAF gene. EIAF may be the fourth ETS-family gene to be identified forming a fusion gene with EWS. We assume that the RNA binding domain of EWS may have been replaced by the DNA binding domain of EIAF in the EWS-EIAF fusion protein as in other fusion proteins previously characterized in Ewing sarcoma and other types of sarcomas.

A single ets-related transcription factor, E1AF, confers invasive phenotype on human cancer cells

Invasion of cancer cells is the first step of metastasis. The invasive activity is thought to be dependent on the production of matrix metalloproteinases (MMPs). The transcription regulatory regions of MMP genes often contain binding sites for Ets and AP-1 transcription factors and they mediate oncogene- and growth factor-induced transcription of the genes. We recently isolated the cDNA encoding human E1AF, a new member of ets oncogene family. E1AF highly stimulated transcription from three different subclasses of MMP genes in transient expression assays. Here we show that transfection of the non-invasive human breast cancer cell line MCF-7 with the E1AF expression plasmid results in induction of invasive and motile activities, accompanied by an increase of 92 kD type IV collagenase (MMP-9) gene expression. Tumors derived from the E1AF transfectant were highly invasive and produced MMP-9. Expression of E1AF and MMP-9 genes was elevated in several invasive tumor cell lines. These results provide evidence for an important role of ets-related E1AF in tumor cell invasion.