THY1 (CD90) Maintains the Adherens Junctions in Nasopharyngeal Carcinoma via Inhibition of SRC Activation

We had previously shown that THY1 (CD90) is a tumor suppressor in nasopharyngeal carcinoma (NPC) and that its down-regulation and loss of expression are associated with tumor metastasis, yet the mechanism leading to such effects remains unknown. In this study we show that tumor invasion could be suppressed by THY1 via adherens junction formation in a few NPC cell lines, and knockdown of THY1 would disrupt this cell-cell adhesion phenotype. Mechanistically, the activity of the SRC family kinase (SFK) member, SRC, and canonical Wnt signaling were dramatically reduced when THY1 was constitutively expressed. Previous studies by others have found that high levels of SRC activity in NPCs are associated with EMT and a poor prognosis. We hypothesized that THY1 can suppress tumor invasion in NPC via inhibition of SRC. By gene silencing of SRC, we found that the in vitro NPC cell invasion was significantly reduced and adherens junctions were restored. Through proteomic analysis, we identified that platelet-derived growth factor receptor β (PDGF-Rβ) and protein tyrosine phosphatase nonreceptor type 22 (PTPN22) are novel and potential binding partners of THY1, which were subsequently verified by co-immunoprecipitation (co-IP) analysis. The ligand of PDGF-Rβ (PDGF-BB) could highly induce SRC activation and NPC cell invasion, which could be almost completely suppressed by THY1 expression. On the other hand, the PTPN22 siRNA could enhance both the SRC activities and the cell invasion and could also disrupt the adherens junctions in the THY1-expressing NPC cells; the original THY1-induced phenotypes were reverted when the PTPN22 expression was reduced. Together, our results identified that PTPN22 is essential for THY1 to suppress cell invasion and SRC activity, maintain tight adherens junctions, and prevent NPC metastasis. These results suggested that PDGF-Rβ and SRC can be used as drug targets for suppressing NPC metastasis. Indeed, our in vivo assay using the SRC inhibitor KX2-391, clearly showed that inhibition of SRC signaling can prevent the metastasis of NPC, indicating that targeting SRC can be a promising approach to control the NPC progression.

EBV latent membrane protein 1 augments γδ T cell cytotoxicity against nasopharyngeal carcinoma by induction of butyrophilin molecules

Nasopharyngeal carcinoma (NPC) is a diverse cancer with no well-defined tumor antigen, associated with oncogenic Epstein-Barr Virus (EBV), and with usually late-stage diagnosis and survival <40%. Current radiotherapy and chemotherapy have low effectiveness and cause adverse effects, which calls for the need of new therapy. In this regard, adoptive immunotherapy using γδ T cells has potential, but needs to be coupled with butyrophilin 2A1 and 3A1 protein expression to achieve tumoricidal effect. Methods: Human γδ T cells were expanded (with Zol or PTA) and used for cytotoxicity assay against NPC cells, which were treated with the EBV EBNA1-targeting peptide (L₂)P₄. Effect of (L₂)P₄ on BTN2A1/BTN3A1 expression in NPC cells was examined by flow cytometry and Western blot. An NPC-bearing NSG mice model was established to test the effectiveness of P₄ and adoptive γδ T cells. Immunofluorescence was performed on NPC tissue sections to examine the presence of γδ T cells and expression of BTN2A1 and BTN3A1. EBV gene expression post-(L₂)P₄ treatment was assessed by qRT-PCR, and the relationship of LMP1, NLRC5 and BTN2A1/BTN3A1 was examined by transfection, reporter assay, Western blot, and inhibition experiments. Results: Zol- or PTA-expanded the Vδ2 subset of γδ T cells that exerted killing against certain NPC cells. (L₂)P₄ reactivates latent EBV, which increased BTN2A1 and BTN3A1 expression and conferred higher susceptibility towards Vδ2 T cells cytotoxicity in vitro, as well as enhanced tumor regression in vivo by adoptive transfer of Vδ2 T cells. Mechanistically, (L₂)P₄ induced EBV LMP1, leading to IFN-γ/p-JNK and NLRC5 activation, and subsequently stimulated the expression of BTN2A1 and BTN3A1. Conclusions: This study demonstrated the effectiveness of using the EBV-targeting probe (L₂)P₄ and adoptive γδ T cells as a promising combinatorial immunotherapy against NPC. The identification of the LMP1-IFN-γ/p-JNK-NLRC5-BTN2A1/BTN3A1 axis may lead to new insight and therapeutic targets against NPC and other EBV⁺ tumors.

Lanthanide-Based Peptide-Directed Visible/Near-Infrared Imaging and Inhibition of LMP1

A lanthanide-based peptide-directed bioprobe LnP19 (Ln = Eu or Yb) is designed as an impressive example of a small molecule-based dual-functional probe for the EBV oncoprotein LMP1. The peptide P19 (Pra-KAhx-K-LDLALK-FWLY-K-IVMSDKW-K-RrRK) is designed to selectively bind to LMP1 by mimicking its TM1 region during oligomerization in lipid rafts while signal transduction is significantly suppressed. Immunofluorescence imaging and Western blotting results reveal that P19 can effectively inactivate the oncogenic cellular pathway nuclear factor κB (NF-κB) and contribute to a selective cytotoxic effect on LMP1-positive cells. By conjugation with cyclen-based europium(III) and ytterbium(III) complexes, EuP19 and YbP19 were constructed to offer visible and near-infrared LMP1-targeted imaging and cancer monitoring. In addition to the ability to target and inhibit LMP1 and to selective inhibit LMP1-positive cells, selective growth inhibition toward the LMP1-positive tumor by LnP19 is also demonstrated.

Dual-Targeting Peptide-Guided Approach for Precision Delivery and Cancer Monitoring by Using a Safe Upconversion Nanoplatform

Using Epstein-Barr virus (EBV)-induced cancer cells and HeLa cells as a comparative study model, a novel and safe dual-EBV-oncoproteins-targeting pH-responsive peptide engineering, coating, and guiding approach to achieve precision targeting and treatment strategy against EBV-associated cancers is introduced. Individual functional peptide sequences that specifically bind to two overexpressed EBV-specific oncoproteins, EBNA1 (a latent cellular protein) and LMP1 (a transmembrane protein), are engineered in three different ways and incorporated with a pH-sensitive tumor microenvironment (TME)-cleavable linker onto the upconversion nanoparticles (UCNP) NaGdF4:Yb3+, Er3+@NaGdF4 (UCNP-P n , n = 5, 6, and 7). A synergistic combination of the transmembrane LMP1 targeting ability and the pH responsiveness of UCNP-P n is found to give specific cancer differentiation with higher cellular uptake and accumulation in EBV-infected cells, thus a lower dose is needed and the side effects and health risks from treatment would be greatly reduced. It also gives responsive UC signal enhancement upon targeted dual-protein binding and shows efficacious EBV cancer inhibition in vitro and in vivo. This is the first example of simultaneous imaging and inhibition of two EBV latent proteins, and serves as a blueprint for next-generation peptide-guided precision delivery nanosystem for the safe monitoring and treatment against one specific cancer.

The Role of EBV-Encoded LMP1 in the NPC Tumor Microenvironment: From Function to Therapy

Nasopharyngeal carcinoma (NPC) is closely associated with Epstein-Barr virus (EBV) infection. It is also characterized by heavy infiltration with non-malignant leucocytes. The EBV-encoded latent membrane protein 1 (LMP1) is believed to play an important role in NPC pathogenesis by virtue of its ability to activate multiple cell signaling pathways which collectively promote cell proliferation and survival, angiogenesis, invasiveness, and aerobic glycolysis. LMP1 also affects cell-cell interactions, antigen presentation, and cytokine and chemokine production. Here, we discuss how LMP1 modulates local immune responses that contribute to the establishment of the NPC tumor microenvironment. We also discuss strategies for targeting the LMP1 protein as a novel therapy for EBV-driven malignancies.

Design, synthesis and comparison of water-soluble phthalocyanine/porphyrin analogues and their inhibition effects on Aβ42 fibrillization

A series of ZnPorp and ZnPc conjugates were synthesized and compared by their inhibitory effects on Aβ₄₂ fibrillization. We show that ZnPc conjugates designed with a good hydrophilic–hydrophobic balance are deemed as better inhibitors.

Targeting Epstein-Barr Virus in Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is consistently associated with Epstein-Barr virus (EBV) infection in regions in which it is endemic, including Southern China and Southeast Asia. The high mortality rates of NPC patients with advanced and recurrent disease highlight the urgent need for effective treatments. While recent genomic studies have revealed few druggable targets, the unique interaction between the EBV infection and host cells in NPC strongly implies that targeting EBV may be an efficient approach to cure this virus-associated cancer. Key features of EBV-associated NPC are the persistence of an episomal EBV genome and the requirement for multiple viral latent gene products to enable malignant transformation. Many translational studies have been conducted to exploit these unique features to develop pharmaceutical agents and therapeutic strategies that target EBV latent proteins and induce lytic reactivation in NPC. In particular, inhibitors of the EBV latent protein EBNA1 have been intensively explored, because of this protein's essential roles in maintaining EBV latency and viral genome replication in NPC cells. In addition, recent advances in chemical bioengineering are driving the development of therapeutic agents targeting the critical functional regions of EBNA1. Promising therapeutic effects of the resulting EBNA1-specific inhibitors have been shown in EBV-positive NPC tumors. The efficacy of multiple classes of EBV lytic inducers for NPC cytolytic therapy has also been long investigated. However, the lytic-induction efficiency of these compounds varies among different EBV-positive NPC models in a cell-context-dependent manner. In each tumor, NPC cells can evolve and acquire somatic changes to maintain EBV latency during cancer progression. Unfortunately, the poor understanding of the cellular mechanisms regulating EBV latency-to-lytic switching in NPC cells limits the clinical application of EBV cytolytic treatment. In this review, we discuss the potential approaches for improvement of the above-mentioned EBV-targeting strategies.

Nuclear DLC1 exerts oncogenic function through association with FOXK1 for cooperative activation of MMP9 expression in melanoma

A Rho GTPase-activating protein (RhoGAP), deleted in liver cancer 1 (DLC1), is known to function as a tumor suppressor in various cancer types; however, whether DLC1 is a tumor-suppressor gene or an oncogene in melanoma remains to be clarified. Here we revealed that high DLC1 expression was detected in most of the melanoma tissues where it was localized in both the nuclei and the cytoplasm. Functional studies unveiled that DLC1 was both required and sufficient for melanoma growth and metastasis. These tumorigenic events were mediated by nuclear-localized DLC1 in a RhoGAP-independent manner. Mechanistically, mass spectrometry analysis identified a DLC1-associated protein, FOXK1 transcription factor, which mediated oncogenic events in melanoma by translocating and retaining DLC1 into the nucleus. RNA-sequencing profiling studies further revealed MMP9 as a direct target of FOXK1 through DLC1-regulated promoter occupancy for cooperative activation of MMP9 expression to promote melanoma invasion and metastasis. Concerted action of DLC1–FOXK1 in MMP9 gene regulation was further supported by their highly correlated expression in melanoma patients’ samples and cell lines. Together, our results not only unravel a mechanism by which nuclear DLC1 functions as an oncogene in melanoma but also suggest an unexpected role of RhoGAP protein in transcriptional regulation.

Crucifera sulforaphane (SFN) inhibits the growth of nasopharyngeal carcinoma through DNA methyltransferase 1 (DNMT1)/Wnt inhibitory factor 1 (WIF1) axis

BACKGROUND

Sulforaphane (SFN), a natural compound present in cruciferous vegetable, has been shown to possess anti-cancer activities. Cancer stem cell (CSC) in bulk tumor is generally considered as treatment resistant cell and involved in cancer recurrence. The effects of SFN on nasopharyngeal carcinoma (NPC) CSCs have not yet been explored.

PURPOSE

The present study aims to examine the anti-tumor activities of SFN on NPC cells with CSC-like properties and the underlying mechanisms.

METHODS

NPC cells growing in monolayer culture, CSCs-enriched NPC tumor spheres, and also the NPC nude mice xenograft were used to study the anti-tumor activities of SFN on NPC. The population of cells expressing CSC-associated markers was evaluated using flow cytometry and aldehyde dehydrogenase (ALDH) activity assay. The effect of DNA methyltransferase 1 (DNMT1) on the growth of NPC cells was analyzed by using small interfering RNA (siRNA)-mediated silencing method.

RESULTS

SFN was found to inhibit the formation of CSC-enriched NPC tumor spheres and reduce the population of cells with CSC-associated properties (SRY (Sex determining Region Y)-box 2 (SOX2) and ALDH). In the functional study, SFN was found to restore the expression of Wnt inhibitory factor 1 (WIF1) and the effect was accompanied with the downregulation of DNMT1. The functional activities of WIF1 and DNMT1 were confirmed using exogenously added recombinant WIF1 and siRNA knockdown of DNMT1. Moreover, SFN was found to inhibit the in vivo growth of C666-1 cells and enhance the anti-tumor effects of cisplatin.

CONCLUSION

Taken together, we demonstrated that SFN could suppress the growth of NPC cells via the DNMT1/WIF1 axis.

The anti-tumor function of the IKK inhibitor PS1145 and high levels of p65 and KLF4 are associated with the drug resistance in nasopharyngeal carcinoma cells

We and others have previously shown that the canonical nuclear factor kappa-B (NF-κB) pathway is essential to nasopharyngeal carcinoma (NPC) tumor development and angiogenesis, suggesting that the NF-κB pathway, including its upstream modulators and downstream effectors, are potential therapeutic targets for NPC. The inhibitor of upstream IκB kinase (IKK), PS1145, is a small molecule which can specifically inhibit the IκB phosphorylation and degradation and the subsequent nuclear translocation of NF-κB. The present study aims to determine the anti-tumor activity of PS1145 on NPC. Our results showed that PS1145 significantly inhibited the growth of tumorigenic NPC cell lines, but not in the normal nasopharyngeal epithelial cell line. Results in the in vivo study showed that low concentration of PS1145 (3 mg/kg) could significantly suppress the subcutaneous tumor formation in the nude mice bearing NPC xenografts. Apparent adverse effects were not observed in the animal study. Drug resistance against PS1145 seems to be associated with the increased levels of active NF-kB p65 and change of expression levels of kruppel-like factor 4. As can be seen, PS1145 appears to be a safe agent for animal experiments and its effects are tumor-specific, and the proteins associated with the drug resistance of PS1145 are implied.

mTORC2-mediated PDHE1α nuclear translocation links EBV-LMP1 reprogrammed glucose metabolism to cancer metastasis in nasopharyngeal carcinoma

EBV infection of preinvasive nasopharyngeal epithelium is believed to be an initiation step during pathogenesis of nasopharyngeal carcinoma (NPC), but the mechanisms remain poorly understood. Here we report a novel mechanism driving NPC metastasis through the EBV-encoded LMP1-mediated metabolic reprogramming, via activation of IGF1-mTORC2 signaling and nuclear acetylation of the Snail promoter by the PDHE1α, an enzyme involved in glucose metabolism. Mechanistically, EBV-LMP1 increases the cellular secretion of IGF1 which promotes phosphorylation of IGF1R to activate mTORC2/AKT signaling linking glucose metabolism to cell motility. LMP1 expression facilitates translocation of mitochondrial PDHE1α into the nucleus in a phosphorylation-dependent manner at Ser²⁹³ residue. Functionally, nuclear PDHE1α promotes H3K9 acetylation on the Snail promoter to enhance cell motility, thereby driving cancer metastasis. Importantly, the IGF1/mTORC2/PDHE1α/Snail axis correlates significantly with disease progression and poor prognosis in NPC patients. This study highlights the functional importance of IGF1-mTORC2-PDHE1α signaling mediated by EBV-LMP1 in NPC pathogenesis.

SOX9 is a dose-dependent metastatic fate determinant in melanoma

Background

In this research, we aimed to resolve contradictory results whether SOX9 plays a positive or negative role in melanoma progression and determine whether SOX9 and its closely related member SOX10 share the same or distinct targets in mediating their functions in melanoma.

Methods

Immunofluorescence, TCGA database and qPCR were used to analyze the correlation between the expression patterns and levels of SOX9, SOX10 and NEDD9 in melanoma patient samples. AlamarBlue, transwell invasion and colony formation assays in melanoma cell lines were conducted to investigate the epistatic relationship between SOX10 and NEDD9, as well as the effects of graded SOX9 expression levels. Lung metastasis was determined by tail vein injection assay. Live cell imaging was conducted to monitor dynamics of melanoma migratory behavior. RHOA and RAC1 activation assays measured the activity of Rho GTPases.

Results

High SOX9 expression was predominantly detected in patients with distant melanoma metastases whereas SOX10 was present in the different stages of melanoma. Both SOX9 and SOX10 exhibited distinct but overlapping expression patterns with metastatic marker NEDD9. Accordingly, SOX10 was required for NEDD9 expression, which partly mediated its oncogenic functions in melanoma cells. Compensatory upregulation of SOX9 expression in SOX10-inhibited melanoma cells reduced growth and migratory capacity, partly due to elevated expression of cyclin-dependent kinase inhibitor p21 and lack of NEDD9 induction. Conversely, opposite phenomenon was observed when SOX9 expression was further elevated to a range of high SOX9 expression levels in metastatic melanoma specimens, and that high levels of SOX9 can restore melanoma progression in the absence of SOX10 both in vitro and in vivo. In addition, overexpression of SOX9 can also promote invasiveness of the parental melanoma cells by modulating the expression of various matrix metalloproteinases. SOX10 or high SOX9 expression regulates melanoma mesenchymal migration through the NEDD9-mediated focal adhesion dynamics and Rho GTPase signaling.

Conclusions

These results unravel NEDD9 as a common target for SOX10 or high SOX9 to partly mediate their oncogenic events, and most importantly, reconcile previous discrepancies that suboptimal level of SOX9 expression is anti-metastatic whereas high level of SOX9 is metastatic in a heterogeneous population of melanoma.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0998-6) contains supplementary material, which is available to authorized users.

EBNA1-targeted inhibitors: Novel approaches for the treatment of Epstein-Barr virus-associated cancers

Epstein-Barr virus (EBV) infects more than 90% of humans worldwide and establishes lifelong latent infection in the hosts. It is closely associated with endemic forms of a wide range of human cancers and directly contributes to the formation of some. Despite its critical role in cancer development, no EBV- or EBV latent protein-targeted therapy is available. The EBV-encoded latent protein, Epstein-Barr nuclear antigen 1 (EBNA1), is expressed in all EBV-associated tumors and acts as the only latent protein in some of these tumors. This versatile protein functions in the maintenance, replication, and segregation of the EBV genome and can therefore serve as an attractive therapeutic target to treat EBV-associated cancers. In the last decades, efforts have been made for designing specific EBNA1 inhibitors to decrease EBNA1 expression or interfere with EBNA1-dependent functions. In this review, we will briefly introduce the salient features of EBNA1, summarize its functional domains, and focus on the recent developments in the identification and design of EBNA1 inhibitors related to various EBNA1 domains as well as discuss their comparative merits.

Responsive upconversion nanoprobe for monitoring and inhibition of EBV-associated cancers via targeting EBNA1

Non-responsive emission enhancement is the disadvantage of upconversion nanomaterials (UCNM) when compared with conventional organic based agents for molecular imaging. We herein show a new strategy by conjugating NaGdF4:Yb3+,Er3+@NaGdF4 (UCNP) with peptides to achieve responsive UC emission enhancement upon binding to a targeted protein - EBNA1. EBNA1 is a well-known viral latent protein for the EBV-associated cancer. Peptide-coating of the functionalized core-shell nanoparticle diminishes upconverted emission intensity drastically. However, the peptide-coated UCNP shows selective and responsive UC emission enhancement via aggregation with the targeted protein. This phenomenon paves a new way for UCNM in molecular imaging.

Abstract 5877: The functional role(s) of serum amyloid A1 (SAA1) polymorphisms in integrin-mediated cell adhesion in nasopharyngeal carcinoma (NPC) cells

Serum amyloid A1 (SAA1) was previously identified as a tumor suppressor gene with anti-angiogenic activities in nasopharyngeal carcinoma (NPC). Three SAA1 isoforms (SAA1.1, 1.3, and 1.5) were observed with disproportionate frequencies among the NPC patients and healthy people. SAA1.1 and 1.3 are the functional isoforms to inhibit angiogenesis whereas SAA1.5 was the defective gene. Our immunohistochemical results showed that the loss of SAA1 staining in the metastatic NPC tissues was significantly associated with tumor progression. We aim to investigate the functional roles of the three SAA1 isoforms in NPC metastasis in the present study. We want to investigate whether the functional SAA1.1 and 1.3 isoforms can suppress tumor metastasis by antagonizing the integrin-FAK signaling pathway in the NPC tumor cells. The focal adhesion assay was performed by seeding the tumor cells with or without the integrin alphaVbeta3/beta5 ligand vitronectin. Both the vector-alone control and the SAA1.5-expressing NPC cells began to spread out and adhered to the bottom of the culture dish in the presence of vitronectin from 7 to 9 hours, whereas the SAA1.1 and SAA1.3-cells remained in the round-up morphology with minimal attachment. Interestingly, after 48 hours the SAA1.1 and SAA1.3-expressing cells formed adherents junction among the cells. In order to study the viability of the effects of the three SAA1 isoforms on NPC cells, MTT viability assay was performed. The results showed that the viability of the SAA1.1 and SAA1.3-expressing cells were around 50 % lower than both the vector-alone and the SAA1.5-expressing cells. It is likely that the loss of focal adhesion after seeding of the SAA1.1 and SAA1.3-expressing cells will affect the survival of NPC cells. Furthermore, we found that the presence of the recombinant SAA1.1 and SAA 1.3 proteins could reduce the number of viable NPC cells compared with the solvent control and the SAA1.5 protein. We previously reported that the SAA1 proteins can physically interact with the integrin alphaVbeta3. Taken together, we suggested that the secreted SAA1 proteins from the NPC cells could directly affect the NPC focal adhesion as well as the cell viability by blocking the integrin on the NPC cell surface. We acknowledge the financial support of the General Research Fund (grant number HKBU17115114 to HLL) of the Research Grants Council of the Hong Kong Special Administrative Region.

Citation Format: On Ying Man, Hong Lok Lung. The functional role(s) of serum amyloid A1 (SAA1) polymorphisms in integrin-mediated cell adhesion in nasopharyngeal carcinoma (NPC) cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5877. doi:10.1158/1538-7445.AM2017-5877

PTPRG suppresses tumor growth and invasion via inhibition of Akt signaling in nasopharyngeal carcinoma

Protein Tyrosine Phosphatase, Receptor Type G (PTPRG) was identified as a candidate tumor suppressor gene in nasopharyngeal carcinoma (NPC). PTPRG induces significant in vivo tumor suppression in NPC. We identified EGFR as a PTPRG potential interacting partner and examined this interaction. Dephosphorylation of EGFR at EGFR-Y1068 and -Y1086 sites inactivated the PI3K/Akt signaling cascade and subsequent down-regulation of downstream pro-angiogenic and -invasive proteins (VEGF, IL6, and IL8) and suppressed tumor cell proliferation, angiogenesis, and invasion. The effect of Akt inhibition in NPC cells was further validated by Akt knockdown experiments in the PTPRG-down-regulated NPC cell lines. Our results suggested that inhibition of Akt in NPC cells induces tumor suppression at both the in vitro and in vivo levels, and also importantly, in vivo metastasis. In conclusion, we confirmed the vital role of PTPRG in inhibiting Akt signaling with the resultant suppression of in vivo tumorigenesis and metastasis.

Nuclear Localization of DNAJB6 Is Associated With Survival of Patients With Esophageal Cancer and Reduces AKT Signaling and Proliferation of Cancer Cells

BACKGROUND & AIMS

The DnaJ (Hsp40) homolog, subfamily B, member 6 (DNAJB6) is part of a family of proteins that regulates chaperone activities. One of its isoforms, DNAJB6a, contains a nuclear localization signal and regulates β-catenin signaling during breast cancer development. We investigated the role of DNAJB6 in the pathogenesis of esophageal squamous cell carcinoma (ESCC).

METHODS

We performed immunohistochemical analyses of primary ESCC samples and lymph node metastases from a cohort of 160 patients who underwent esophagectomy with no preoperative chemoradiotherapy at Hong Kong Queen Mary Hospital. Data were collected on patient outcomes over a median time of 12.1 ± 2.9 months. Retrospective survival association analyses were performed. Wild-type and mutant forms of DNAJB6a were overexpressed in cancer cell lines (KYSE510, KYSE 30TSI, KYSE140, and KYSE70TS), which were analyzed in proliferation and immunoblot assays, or injected subcutaneously into nude mice. Levels of DNAJB6 were knocked down in ESCC cell lines (KYSE450 and T.Tn), immortalized normal esophageal epithelial cell lines (NE3 and NE083), and other cells with short hairpin RNAs, or by genome engineering. Bimolecular fluorescence complementation was used to study interactions between proteins in living cells.

RESULTS

In primary ESCC samples, patients whose tumors had high nuclear levels of DNAJB6 had longer overall survival times (19.2 ± 1.8 months; 95% confidence interval [CI], 15.6-22.8 mo) than patients whose tumors had low nuclear levels of DNAJB6 (12.6 ± 1.4 mo; 95% CI, 9.8-15.4 mo; P = .004, log-rank test). Based on Cox regression analysis, patients whose tumors had high nuclear levels of DNAJB6 had a lower risk of death than patients with low levels (hazard ratio, 0.562; 95% CI, 0.379-0.834; P = .004). Based on log-rank analysis and Cox regression analysis, the combination of the nuclear level of DNAJB6 and the presence of lymph node metastases at diagnosis could be used to stratify patients into groups with good or bad outcomes (P < .0005 for both analyses). There was a negative association between the nuclear level of DNAJB6 and the presence of lymph node metastases (P = .022; Pearson χ(2) test). Cancer cell lines that overexpressed DNAJB6a formed tumors more slowly in nude mice than control cells or cells that expressed a mutant form of DNAJB6a that did not localize to the nucleus. DNAJB6 knockdown in cancer cell lines promoted their growth as xenograft tumors in mice. A motif of histidine, proline, and aspartic acid in the J domain of DNAJB6a was required for its tumor-suppressive effects and signaling via AKT1. Loss of DNAJB6a resulted in up-regulation of AKT signaling in cancer cell lines and immortalized esophageal epithelial cells. Expression of a constitutively active form of AKT1 restored proliferation to tumor cells that overexpressed DNAJB6a, and DNAJB6a formed a complex with AKT1 in living cells. The expression of DNAJB6a reduced the sensitivity of ESCC to AKT inhibitors; the expression level of DNAJB6a affected AKT signaling in multiple cancer cell lines.

CONCLUSIONS

Nuclear localization of DNAJB6 is associated with longer survival times of patients with ESCC. DNAJB6a reduces AKT signaling, and DNAJB6 expression in cancer cells reduces their proliferation and growth of xenograft tumors in mice. DNAJB6a might be developed as a biomarker for progression of ESCC.

Significance of NF-κB activation in immortalization of nasopharyngeal epithelial cells

NF-κB is a key regulator of inflammatory response and is frequently activated in human cancer including the undifferentiated nasopharyngeal carcinoma (NPC), which is common in Southern China including Hong Kong. Activation of NF-κB is common in NPC and may contribute to NPC development. The role of NF-κB activation in immortalization of nasopharyngeal epithelial (NPE) cells, which may represent an early event in NPC pathogenesis, is unknown. Examination of NF-κB activation in immortalization of NPE cells is of particular interest as the site of NPC is often heavily infiltrated with inflammatory cellular components. We found that constitutive activation of NF-κB signaling is a common phenotype in telomerase-immortalized NPE cell lines. Our results suggest that NF-κB activation promotes the growth of telomerase-immortalized NPE cells, and suppression of NF-κB activity inhibits their proliferation. Furthermore, we observed upregulation of c-Myc, IL-6 and Bmi-1 in our immortalized NPE cells. Inhibition of NF-κB downregulated expression of c-Myc, IL-6 and Bmi-1, suggesting that they are downstream events of NF-κB activation in immortalized NPE cells. We further delineated that EGFR/MEK/ERK/IKK/mTORC1 is the key upstream pathway of NF-κB activation in immortalized NPE cells. Elucidation of events underlying immortalization of NPE cells may provide insights into early events in pathogenesis of NPC. The identification of NF-κB activation and elucidation of its activation mechanism in immortalized NPE cells may reveal novel therapeutic targets for treatment and prevention of NPC.

The interplay of host genetic factors and Epstein-Barr virus in the development of nasopharyngeal carcinoma

The interplay between host cell genetics and Epstein-Barr virus (EBV) infection contributes to the development of nasopharyngeal carcinoma (NPC). Understanding the host genetic and epigenetic alterations and the influence of EBV on cell signaling and host gene regulation will aid in understanding the molecular pathogenesis of NPC and provide useful biomarkers and targets for diagnosis and therapy. In this review, we provide an update of the oncogenes and tumor suppressor genes associated with NPC, as well as genes associated with NPC risk including those involved in carcinogen detoxification and DNA repair. We also describe the importance of host genetics that govern the human leukocyte antigen (HLA) complex and immune responses, and we describe the impact of EBV infection on host cell signaling changes and epigenetic regulation of gene expression. High-power genomic sequencing approaches are needed to elucidate the genetic basis for inherited susceptibility to NPC and to identify the genes and pathways driving its molecular pathogenesis.

NF-κB p65 Subunit Is Modulated by Latent Transforming Growth Factor-β Binding Protein 2 (LTBP2) in Nasopharyngeal Carcinoma HONE1 and HK1 Cells

NF-κB is a well-characterized transcription factor, widely known as a key player in tumor-derived inflammation and cancer development. Herein, we present the functional and molecular relevance of the canonical NF-κB p65 subunit in nasopharyngeal carcinoma (NPC). Loss- and gain-of-function approaches were utilized to reveal the functional characteristics of p65 in propagating tumor growth, tumor-associated angiogenesis, and epithelial-to-mesenchymal transition in NPC cells. Extracellular inflammatory stimuli are critical factors that trigger the NF-κB p65 signaling; hence, we investigated the components of the tumor microenvironment that might potentially influence the p65 signaling pathway. This led to the identification of an extracellular matrix (ECM) protein that was previously reported as a candidate tumor suppressor in NPC. Our studies on the Latent Transforming Growth Factor-β Binding Protein 2 (LTBP2) protein provides substantial evidence that it can modulate the p65 transcriptional activity. Re-expression of LTBP2 elicits tumor suppressive effects that parallel the inactivation of p65 in NPC cells. LTBP2 was able to reduce phosphorylation of p65 at Serine 536, inhibit nuclear localization of active phosphorylated p65, and impair the p65 DNA-binding ability. This results in a consequential down-regulation of p65-related gene expression. Therefore, the data suggest that the overall up-regulation of p65 expression and the loss of this candidate ECM tumor suppressor are milestone events contributing to NPC development.

Novel lentiviral-inducible transgene expression systems and versatile single-plasmid reporters for in vitro and in vivo cancer biology studies

Many of the cancer cell lines derived from solid tumors are difficult to transfect using commonly established transfection approaches. This hurdle for some DNA transfection systems has hindered cancer biology studies. Moreover, there are limited tools for studying pathway activities. Therefore, highly efficient improved gene transfer and versatile genetic tools are required. In this study, we established and developed a comprehensive set of new lentiviral tools to study gene functions and pathway activities. Using the optimized conditions, cancer cell lines achieved >90% transduction efficiency. Novel lentiviral doxycycline-regulated pTet-IRES-EGFP (pTIE) systems for transgene expression and TRE reporters used for pathway activity determination were developed and tested. The pTIE Tet-Off system showed in vitro doxycycline-sensitive responses with low or undetectable leakage of protein expression and in vivo tumor suppression as illustrated using candidate tumor suppressors, Fibulin-2 and THY1. In contrast, the Tet-On system showed dose-dependent responses. The pTRE-EGFP (pTE) and pTRE-FLuc-EF1α-RLuc (pT-FER) reporters with the NFκB p65 subunit consensus sequence showed GFP and firefly luciferase responses, which were directly correlated with TNFα stimulation, respectively. Taken together, these newly developed lentiviral systems provide versatile in vitro and in vivo platforms to strengthen our capabilities for cancer biology studies.

Anti-angiogenic pathway associations of the 3p21.3 mapped BLU gene in nasopharyngeal carcinoma

Zinc-finger, MYND-type containing 10 (ZMYND10), or more commonly called BLU, expression is frequently downregulated in nasopharyngeal carcinoma (NPC) and many other tumors due to promoter hypermethylation. Functional evidence shows that the BLU gene inhibits tumor growth in animal assays, but the detailed molecular mechanism responsible for this is still not well understood. In current studies, we find that 93.5% of early-stage primary NPC tumors show downregulated BLU expression. Using a PCR array, overexpression of the BLU gene was correlated to the angiogenesis network in NPC cells. Moreover, expression changes of the MMP family, VEGF and TSP1, were often detected in different stages of NPC, suggesting the possibility that BLU may be directly involved in the microenvironment and anti-angiogenic activity in NPC development. Compared with vector-alone control cells, BLU stable transfectants, derived from poorly-differentiated NPC HONE1 cells, suppress VEGF165, VEGF189 and TSP1 expression at both the RNA and protein levels, and significantly reduce the secreted VEGF protein in these cells, reflecting an unknown regulatory mechanism mediated by the BLU gene in NPC. Cells expressing BLU inhibited cellular invasion, migration and tube formation. These in vitro results were further confirmed by in vivo tumor suppression and a matrigel plug angiogenesis assay in nude mice. Tube-forming ability was clearly inhibited, when the BLU gene is expressed in these cells. Up to 70-90% of injected tumor cells expressing increased exogenous BLU underwent cell death in animal assays. Overexpressed BLU only inhibited VEGF165 expression in differentiated squamous NPC HK1 cells, but also showed an anti-angiogenic effect in the animal assay, revealing a complicated mechanism regulating angiogenesis and the microenvironment in different NPC cell lines. Results of these studies indicate that alteration of BLU gene expression influences anti-angiogenesis pathways and is important for the development of NPC.

Abstract 1150: The role of the tumor suppressor gene THY1 in suppression of epithelial-mesenchymal transition (EMT) in nasopharyngeal carcinoma

Background and aims:

THY1 has been successfully identified as a tumor suppressor gene (TSG) in nasopharyngeal carcinoma (NPC) in our laboratory. The frequency of down-regulated THY1 protein expression was found to be significantly associated with NPC lymph node metastases. However, direct functional evidence is still lacking for THY1 being anti-metastatic in NPC. Epithelial-Mesenchymal Transition (EMT) is well-known as a closely associated process for stem cells as well as tumor cells to invade to other part of the body. We aim to study the association of EMT with the THY1 in NPC.

Methods: Functional analysis of restoration of THY1 expression in the NPC cell lines was studied. The RhoA negative regulator, p190 Rho GTPase-activating protein (p190RhoGAP) and the E-cadherin/beta-catenin cell junction was examined in the THY1-expressing NPC cells.

Results: Both real-time and conventional invasion chamber assays clearly showed that the invasive ability of the THY1 transfectants was consistently lower than vector-alone control. The reverse transcription-polymerase chain reaction (RT-PCR) results show that the gene expression of cell invasion-associated gelatinase MMP-9 was significantly down-regulated in the THY1-transfectants compared with the vector-alone control. The p190RhoGAP was greatly activated by phosphorylation in the THY1 transfectants, when the THY1 gene was switched on in the absence of doxycycline (dox, an analogue of tetracycline). In the presence of dox when THY1 was switched off, the phosphorylation of p190RhoGAP was reduced. It appears that the phosphorylation status of p190RhoGAP is positively regulated by THY1 in NPC cells. The immunofluorescence (IF) confocal microscopy results show that beta-catenin and E-cadherin were much more frequently translocated to the cell-cell junction in the THY1 transfectants than the vector-alone.

Conclusions: These findings suggest that THY1 inhibited NPC cell invasion via the formation of adherens junction and up-regulation of p190RhoGAP. The enhanced formation of cell adherens junction by THY1 is likely to be one of the possible mechanisms to suppress EMT in NPC.

Citation Format: Hong Lok Lung, Maria Li Lung. The role of the tumor suppressor gene THY1 in suppression of epithelial-mesenchymal transition (EMT) in nasopharyngeal carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1150. doi:10.1158/1538-7445.AM2014-1150

Abstract 1550: Differential angiogenic roles of serum amyloid A 1 (SAA1) isoforms in esophageal squamous cell carcinoma (ESCC)

Esophageal Caner (EC), a highly metastatic and fatal cancer, is ranked the eighth in mortality rate in Hong Kong cancer patients (Hong Kong Cancer Registry, Hospital Authority, 2010). Esophageal Squamous Cell Carcinoma (ESCC) is the predominant type comprising more than 90% of EC. Using a functional complementation approach, SAA1 was identified as one of the tumor suppressor gene candidates. SAA1 is located at chromosome 11p15.1 and is expressed as a secretary protein in liver, human cultured smooth muscle cells, monocyte-macrophage cell lines, and in histologically-normal human epithelial tissues. Genetic polymorphisms of SAA1 have been identified as a risk factor of diseases such as amyloidosis. Three SAA1 isoforms with two single nucleotide polymorphisms at exon three (SAA1.1, 1.3, and 1.5) were observed in the ESCC patients and healthy individuals.

The SAA proteins contain the functional YIGSR-like and RGD-like motifs, proteins with these motifs can inhibit angiogenesis, cell adhesion to ECM, growth and metastasis. To understand the anti-tumorigenic and anti-angiogenic roles of the three SAA1 isoforms in ESCC progression, both recombinant proteins and secreted proteins from the conditioned media of lentiviral-infected ESCC cell lines were used for functional assays. For the vascular endothelial cell tube formation assay, the treatments with SAA1.1 and 1.3 proteins showed suppression of tube formation, whereas no significant effects could be observed in the treatment with the SAA1.5. Suppression of cell proliferation and induction of cell death were observed when the endothelial cells were cultured with SAA1.1 and 1.3 proteins. To further elucidate the differential effects among the three SAA1 isoforms in anti-angiogenesis, the cytoskeleton arrangement of the vascular endothelial cells was studied. The SAA1.1 and SAA1.3 proteins could abolish the endothelial cell adhesion by disturbing the formation of stress fibers and focal adhesions. As a conclusion, the present data has shown the variation in anti-angiogenic potential of the three SAA1 isoforms.

We acknowledge the financial support of the Food and Health Bureau of the Hong Kong Special Administration Region, China, grant number HMRF 01120886 to HLL.

Citation Format: ON YING MAN, Maria Lung, Hong Lok Lung. Differential angiogenic roles of serum amyloid A 1 (SAA1) isoforms in esophageal squamous cell carcinoma (ESCC). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1550. doi:10.1158/1538-7445.AM2014-1550

SAA1 polymorphisms are associated with variation in antiangiogenic and tumor-suppressive activities in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a cancer that occurs in high frequency in Southern China. A previous functional complementation approach and the subsequent cDNA microarray analysis have identified that serum amyloid A1 (SAA1) is an NPC candidate tumor suppressor gene. SAA1 belongs to a family of acute-phase proteins that are encoded by five polymorphic coding alleles. The SAA1 genotyping results showed that only three SAA1 isoforms (SAA1.1, 1.3 and 1.5) were observed in both Hong Kong NPC patients and healthy individuals. This study aims to determine the functional role of SAA1 polymorphisms in tumor progression and to investigate the relationship between SAA1 polymorphisms and NPC risk. Indeed, we have shown that restoration of SAA1.1 and 1.3 in the SAA1-deficient NPC cell lines could suppress tumor formation and angiogenesis in vitro and in vivo. The secreted SAA1.1 and SAA1.3 proteins can block cell adhesion and induce apoptosis in the vascular endothelial cells. In contrast, the SAA1.5 cannot induce apoptosis or inhibit angiogenesis because of its weaker binding affinity to αVβ3 integrin. This can explain why SAA1.5 has no tumor-suppressive effects. Furthermore, the NPC tumors with this particular SAA1.5/1.5 genotype showed higher levels of SAA1 gene expression, and SAA1.1 and 1.3 alleles were preferentially inactivated in tumor tissues that were examined. These findings further strengthen the conclusion for the defective function of SAA1.5 in suppression of tumor formation and angiogenesis. Interestingly, the frequency of the SAA1.5/1.5 genotype in NPC patients was ~2-fold higher than in the healthy individuals (P=0.00128, odds ratio=2.28), which indicates that this SAA1 genotype is significantly associated with a higher NPC risk. Collectively, this homozygous SAA1.5/1.5 genotype appears to be a recessive susceptibility gene, which has lost the antiangiogenic function, whereas SAA1.1 and SAA1.3 are the dominant alleles of the tumor suppressor phenotype.

Polo-like kinase inhibitor Ro5203280 has potent antitumor activity in nasopharyngeal carcinoma

Nasopharyngeal carcinoma is a cancer with its highest prevalence among the southern Chinese and is rare elsewhere in the world. The main treatment modalities include chemotherapy and radiotherapy. However, tumor chemoresistance often limits the efficacy of nasopharyngeal carcinoma treatment and reduces survival rates. Thus, identifying new selective chemotherapeutic drugs for nasopharyngeal carcinoma treatment is needed. In this current study, the antitumor efficacy of a polo-like kinase inhibitor, Ro5203280, was investigated. Ro5203280 induces tumor suppression both in vitro and in vivo. An inhibitory effect was observed with the highly proliferating cancer cell lines tested, but not with the nontumorigenic cell line. Real-time cell proliferation and fluorescence-activated cell sorting (FACS) analysis, together with immunohistochemical (IHC), immunofluorescence, and Annexin V staining assays, were used to evaluate the impact of drug treatment on cell cycle and apoptosis. Ro5203280 induces G2-M cell-cycle arrest and apoptosis. Western blotting shows it inhibits PLK1 phosphorylation and downregulates the downstream signaling molecule, Cdc25c, and upregulates two important mitosis regulators, Wee1 and Securin, as well as the DNA damage-related factor Chk2 in vitro and in vivo. In vivo tumorigenicity assays with Ro5203280 intravenous injection showed its potent ability to inhibit tumor growth in mice, with no observable signs of toxicity. These findings suggest the potential usefulness of Ro5203280 as a chemotherapeutic targeting drug for nasopharyngeal carcinoma treatment.

A CD90(+) tumor-initiating cell population with an aggressive signature and metastatic capacity in esophageal cancer

Tumor-initiating cells (TIC), also known as cancer stem cells, are regarded widely as a specific subpopulation of cells needed for cancer initiation and progression. TICs have yet to be identified in esophageal tumors that have an increasing incidence in developed countries. Here, we report a CD90(+) cell population found in esophageal squamous cell carcinoma (ESCC), which is endowed with stem cell-like properties and high tumorigenic and metastatic potential. mRNA profiling of these cells suggested pathways through which they drive tumor growth and metastasis, with deregulation of an Ets-1/MMP signaling pathway and epithelial-mesenchymal transition figuring prominently. These cells possessed higher self-renewal activity and were sufficient for tumor growth, differentiation, metastasis, and chemotherapeutic resistance. CD90(+) TICs were isolated and characterized from ESCC clinical specimens as well as ESCC cell lines. In freshly resected clinical specimens, they represented a rare cell population, the levels of which correlated with strong family histories and lymph node metastasis. Our results prompt further study of this CD90(+) population of esophageal TICs as potential therapeutic targets.

Abstract 4002: Functional investigation and identification of dephosphorylation targets of tumor-suppressive protein tyrosine phosphatase, PTPRG

Background and aims: PTPRG was identified as a candidate tumor suppressor gene. It belongs to a family of membrane-bound receptor tyrosine phosphatases. However, the function and the dephosphorylation targets of PTPRG still remain to be elucidated. The aim of this current study was to identify the downstream dephosphorylation targets of PTPRG. Methods: A tetracycline-inducible system was used to obtain PTPRG-expressing clones. The dephosphorylation targets were identified by an antibody array. The anti-angiogenesis function of PTPRG was investigated by HUVEC tube formation assay. Results: The c-jun phosphorylation level was found to be down-regulated after re-expression of PTPRG. Re-expression of PTPRG can inhibit tube formation in the HUVEC tube formation assay by down-regulating the AP1 downstream target, VEGF, secretion. Conclusions: Re-expression of PTPRG can reduce the phosphorylation of c-jun and, thus, inhibit angiogenesis by down-regulating the important angiogenesis regulator, VEGF. The results suggest the importance of PTPRG in regulating tumor formation. It is a good candidate tumor suppressor gene, which warrants further study. Acknowledgements: This work was supported by the Research Grants Council and the University Grants Council of the Hong Kong Special Administrative Region, People's Republic of China (AoE/M-06/08, to M.L.L.) and the University of Hong Kong Small Project Fund (Grant 200907176081, to A.K.L.C.).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4002. doi:1538-7445.AM2012-4002

Abstract 3998: The role of serum amyloid A1 (SAA1) in nasopharyngeal carcinoma (NPC)

Background and aims: Nasopharyngeal carcinoma (NPC) is a cancer which occurs in high frequency in Southern China. The identification of diagnostic and prognostic markers will be highly beneficial for early stage NPC detection. Previous microcell-mediated chromosome transfer (MMCT) studies showed that the transfer of an intact human chromosome 11 suppresses the in vivo tumor growth of a NPC cell line (HONE1) in nude mouse tumorigenicity assays. We aim to identify candidate genes which are associated with tumor suppression in NPC. Methods: Differential expression analysis of 19K genes was performed in oligonucleotide microarray hybridization for the chromosome 11 microcell hybrids (MCHs)/ tumor segregants (TSs) pairs to hunt for some other unknown NPC genes. The gene expression of the candidate gene was examined in the NPC cell lines and tumor tissues. Functional analysis of restoration of the candidate gene expression was studied. Results: Using oligonucleotide microarray analysis, Serum Amyloid A 1 (SAA1), mapping close to 11p15.1, was identified as showing consistent down-regulated expression in the TSs, as compared to their parental tumor-suppressing MCHs. Gene expression and protein analyses show that SAA1 was not expressed in the NPC HONE1 recipient cells, tumor segregants, and other NPC cell lines; SAA1 was exclusively expressed in the non-tumorigenic MCHs. The mechanism of SAA1 gene inactivation in these NPC cell lines was attributed to hypermethylation. The clinical relevance of SAA1 in NPC was examined by RT-PCR; 54.8% (23/42) of NPC specimens showed either down-regulation or loss of SAA1 gene expression. After transfection of SAA1 gene into HONE1 cells, a dramatic reduction of colony formation ability was observed. Conclusions: These findings suggest that SAA1 is a candidate tumor suppressor gene in NPC. Acknowledgments Grant support: Research Grants Council of the Hong Kong Special Administrative Region, People's Republic of China grant HKU772309 (H.L. Lung)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3998. doi:1538-7445.AM2012-3998

Tumor suppressor Alpha B-crystallin (CRYAB) associates with the cadherin/catenin adherens junction and impairs NPC progression-associated properties

Alpha B-crystallin (CRYAB) maps within the nasopharyngeal carcinoma (NPC) tumor-suppressive critical region 11q22-23 and its downregulation is significantly associated with the progression of NPC. However, little is known about the functional impact of CRYAB on NPC progression. In this study we evaluated the NPC tumor-suppressive and progression-associated functions of CRYAB. Activation of CRYAB suppressed NPC tumor formation in nude mice. Overexpression of CRYAB affected NPC progression-associated phenotypes such as loss of cell adhesion, invasion, interaction with the tumor microenvironment, invasive protrusion formation in three dimensional Matrigel culture, as well as expression of epithelial-mesenchymal transition-associated markers. CRYAB mediates this ability to suppress cancer progression by inhibition of E-cadherin cytoplasmic internalization and maintenance of β-catenin in the membrane that subsequently reduces the levels of expression of critical downstream targets such as cyclin-D1 and c-myc. Both ectopically expressed and recombinant CRYAB proteins were associated with endogenous E-cadherin and β-catenin, and, thus, the cadherin/catenin adherens junction. The CRYAB α-crystallin core domain is responsible for the interaction of CRYAB with both E-cadherin and β-catenin. Taken together, these results indicate that CRYAB functions to suppress NPC progression by associating with the cadherin/catenin adherens junction and modulating the β-catenin function.

Anti-angiogenic and tumor-suppressive roles of candidate tumor-suppressor gene, Fibulin-2, in nasopharyngeal carcinoma

Fibulin-2 (FBLN2) has been identified as a candidate tumor-suppressor gene in nasopharyngeal carcinoma (NPC). Originally identified through a chromosome 3 NotI genomic microarray screen, it shows frequent deletion or methylation in NPC. FBLN2 is located on chromosome 3p25.1 and is associated with tumor development through its important interactions with the extracellular matrix (ECM) proteins. FBLN2 encodes two isoforms. The short isoform (FBLN2S) is expressed abundantly in normal tissues, but is dramatically downregulated in NPC, while the long isoform (FBLN2L) is either not detectable or is expressed only at low levels in both normal and tumor tissues. Reintroduction of this FBLN2S inhibited cell proliferation, migration, invasion and angiogenesis in vitro. Furthermore, in vivo studies in nude mice show its expression is associated with tumor and angiogenesis suppression. FBLN2-associated angiogenesis occurs via concomitant downregulation of vascular endothelial growth factor and matrix metalloproteinase 2. This study provides compelling evidence that FBLN2S has an important tumor-suppressive and anti-angiogenic role in NPC.

Catalytic activity of Matrix metalloproteinase-19 is essential for tumor suppressor and anti-angiogenic activities in nasopharyngeal carcinoma

The association of Matrix metalloproteinase-19 (MMP19) in the development of nasopharyngeal carcinoma (NPC) was identified from differential gene profiling, which showed MMP19 was one of the candidate genes down-regulated in the NPC cell lines. In this study, quantitative RT-PCR and Western blot analysis showed MMP19 was down-regulated in all seven NPC cell lines. By tissue microarray immunohistochemical staining, MMP19 appears down-regulated in 69.7% of primary NPC specimens. Allelic deletion and promoter hypermethylation contribute to MMP19 down-regulation. We also clearly demonstrate that the catalytic activity of MMP19 plays an important role in antitumor and antiangiogenesis activities in comparative studies of the wild-type and the catalytically inactive mutant MMP19. In the in vivo tumorigenicity assay, only the wild-type (WT), but not mutant, MMP19 transfectants suppress tumor formation in nude mice. In the in vitro colony formation assay, WT MMP19 dramatically reduces colony-forming ability of NPC cell lines, when compared to the inactive mutant. In the tube formation assay of human umbilical vein endothelial cells and human microvascular endothelial cells (HMEC-1), secreted WT MMP19, but not mutant MMP19, induces reduction of tube-forming ability in endothelial cells with decreased vascular endothelial growth factor (VEGF) in conditioned media detected by enzyme-linked immunosorbent assay (ELISA). The anti-angiogenic activity of WT MMP19 is correlated with suppression of tumor formation. These results now clearly show that catalytic activity of MMP19 is essential for its tumor suppressive and anti-angiogenic functions in NPC.

Functional characterization of THY1 as a tumor suppressor gene with antiinvasive activity in nasopharyngeal carcinoma

THY1 was previously identified as a candidate tumor suppressor gene (TSG) associated with lymph node metastases in nasopharyngeal carcinoma (NPC) through functional studies. It was identified by oligonucleotide microarray analysis as an interesting differentially expressed gene. However, direct functional evidence is still lacking for THY1 being a TSG in NPC, as in vivo tumorigenicity assays have not been previously reported in our last study of THY1. In this study, a tetracycline-inducible expression vector, pETE-Bsd, was used to obtain stable transfectants of THY1. The stringent in vivo tumorigenicity assay results show that the activation of THY1 suppresses tumor formation of HONE1 cells in nude mice, and the tumor formation ability was restored in the presence of doxycycline (a tetracycline analog), when the gene is shut off. Functional inactivation of this gene is observed in all the tumors derived from the tumorigenic transfectant. The tumor suppressive effect could be repressed by knockdown of THY1 expression in nontumorigenic microcell hybrids. Further studies indicate that expression of THY1 inhibits HONE1 cell growth in vitro by arresting cells in G(0)/G(1) phase. It greatly reduces the ability for anchorage-independent growth. The invasiveness of HONE1 cells was also inhibited by the expression of THY1. These findings suggest that THY1 is a TSG in NPC, which is involved in invasion and shows an association with tumor metastasis. Taken together, THY1 clearly plays an important functional role in tumor suppression in NPC.

Extracellular protease ADAMTS9 suppresses esophageal and nasopharyngeal carcinoma tumor formation by inhibiting angiogenesis

ADAMTS metalloprotease family member ADAMTS9 maps to 3p14.2 and shows significant associations with the aerodigestive tract cancers esophageal squamous cell carcinoma (ESCC) and nasopharyngeal carcinoma (NPC). However, the functional impact of ADAMTS9 on cancer development has not been explored. In this study, we evaluated the hypothesized antiangiogenic and tumor-suppressive functions of ADAMTS9 in ESCC and NPC, in stringent tumorigenicity and Matrigel plug angiogenesis assays. ADAMTS9 activation suppressed tumor formation in nude mice. Conversely, knockdown of ADAMTS9 resulted in clones reverting to the tumorigenic phenotype of parental cells. In vivo angiogenesis assays revealed a reduction in microvessel numbers in gel plugs injected with tumor-suppressive cell transfectants. Similarly, conditioned medium from cell transfectants dramatically reduced the tube-forming capacity of human umbilical vein endothelial cells. These activities were associated with a reduction in expression levels of the proangiogenic factors MMP9 and VEGFA, which were consistently reduced in ADAMTS9 transfectants derived from both cancers. Taken together, our results indicate that ADAMTS9 contributes an important function in the tumor microenvironment that acts to inhibit angiogenesis and tumor growth in both ESCC and NPC.

Abstract 3069: Importance of zinc-binding domain of matrix metalloproteinase 19 (MMP19) in tumor suppression and anti-angiogenesis of nasopharyngeal carcinoma

Background and aims: Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases consisting of more than 20 enzymes. MMP19 shares the typical MMP structural domains. It degrades various ECM components including collagen type IV, nidogen-1, fibronectin, tenascin-C isoform, aggrecan, and laminin-5-gamma-2-chain. In our previous studies, MMP19 was identified as a candidate tumor suppressor gene (TSG) in nasopharyngeal carcinoma (NPC). It was down-regulated in NPC cell lines and NPC biopsies, when compared to an immortalized normal nasopharyngeal epithelial cell line and corresponding non-tumor nasopharyngeal tissues. Transfection of wild-type (WT) MMP19 into the HONE1-2 NPC cell line significantly suppressed tumor formation in the nude mouse tumorigenicity assay and decreased the tube-forming ability of both human umbilical vein endothelial cells (HUVEC) and human microvascular endothelial cells (HMEC-1). In this study, we aimed to validate the importance of the zinc-binding domain of MMP19 in NPC. Methods: We transfected the mutant MMP19, which contained a mutation at the zinc-binding domain, into HONE1-2 to study the effect of mutant MMP19 in tumor suppression and anti-angiogenesis compared to WT MMP19. Results: Mutant MMP19 was not tumor-suppressive, as is the WT MMP19, and aggressive tumors appeared with the same growth kinetics as the vector-alone control. The anti-angiogenesis effect was also not observed in endothelial cells incubated with conditioned medium from mutant MMP19 clones compared to WT MMP19 clones. Conclusions: Previous studies showed mutation of the zinc-binding domain in MMP19 leads to loss of MMP19 function in cell proliferation, migration, and protein degradation in a human keratinocyte cell model. This study demonstrates loss of tumor suppressive and anti-angiogenesis function of mutant MMP19 in NPC and indicates the importance of the zinc-binding motif for WT MMP19 in suppression of tumor formation and in inhibition of tube-forming ability of endothelial cells in NPC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3069.

Abstract 3080: Functional studies of a cell cycle and angiogenesis-related candidate tumor suppressor gene, Mirror image polydactyly 1, in nasopharyngeal carcinoma

Background and aims: Nasopharyngeal carcinoma (NPC) is a cancer with an especially high incidence in Southern China. We performed functional complementation studies to confirm and map critical regions on chromosome 14 associated with its tumor-suppressive ability. An interesting candidate tumor suppressor gene (TSG), Mirror image polydactyly 1 (MIPOL1) was identified. Previously this gene has only been reported to be associated with a genetic developmental disorder. Its contribution to cancer and its functional role in NPC was, therefore, investigated. Methods: A tetracycline-inducible system was used to obtain MIPOL1-expressing clones. A wild-type MIPOL1 gene was transferred into a NPC cell line, HONE1-2. Functional studies such as in vivo nude mouse tumorigenicity, HUVEC tube formation, and cell cycle analysis assays were used to investigate the function of MIPOL1. Results: MIPOL1 re-expression can suppress tumor growth in vivo and induce cell cycle arrest through increasing p21(WAF1/CIP1) and p27(KIP1) expression. Furthermore, expression of MIPOL1 can inhibit angiogenesis in the tube formation assay. Functional pathways were studied by detection of change in expression levels of different angiogenesis-related proteins in cell lysates and conditional medium of those stable clones. Conclusions: An interesting candidate TSG, MIPOL1, was identified. Functional studies confirm that MIPOL1 can suppress tumor growth in vivo. It can induce cell cycle arrest through the p21(WAF1/CIP1) and p27(KIP1) pathways. MIPOL1 can also inhibit angiogenesis, and this further confirms its importance in tumor suppression. Changes in expression of different angiogenesis-related proteins were observed. MIPOL1 is a good candidate tumor suppressor gene in NPC and warrants further study.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3080.

Abstract 3058: ADAMTS9 inhibits angiogenesis and induces apoptosis in nasopharyngeal carcinoma

Background and aims: A disintegrin-like and metalloprotease with thrombospondin type 1 motif 9 (ADAMTS9), a gene mapping to 3p14.2, has been shown to be silenced by promoter hypermethylation in nasopharyngeal carcinoma (NPC). The ADAMTS family consists of 19 secretion protein members consisting of a disintegrin domain, metalloproteinase domain, and different numbers of thrombospondin type 1 motifs. ADAMTS9 encodes a member of a large family of 19 metalloproteases involved in maturation of precursor proteins, extracellular matrix remodeling, cell migration, and inhibition of angiogenesis. Although the related matrix metalloproteases and ADAM proteases have been clearly implicated in tumor progression and angiogenesis, the role of ADAMTS proteases in cancer is less clearly defined. In the present study, we investigated the in vivo and in vitro functional roles of ADAMTS9 in angiogenesis of NPC.

Methods: To examine the antigiogenic activity of ADAMTS9 in NPC, the in vivo gel plug and in vitro tube formation assays were performed using a tetracycline-regulated expression vector in the present study.

Results: Here we show that when incubated with conditional media from the ADAMTS9 stable transfectant, the human umbilical vein endothelial cells (HUVEC) showed a dramatic decrease of tube formation ability. When the gel plugs used for the in vivo angiogenesis in the above section were stained with H&E, we observed that the numbers of apoptotic cells in the ADAMTS9 stable transfectant were dramatically increased. The numbers of apoptotic cells were also increased when growing in the absence of serum. Conclusions: Taken together, these studies indicate that ADAMTS9 is an important candidate tumor suppressor gene in NPC, which might mediate its tumor suppressive effects through the anti-angiogenic and pro-apoptotic mechanisms.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3058.

Functional analysis of a cell cycle-associated, tumor-suppressive gene, protein tyrosine phosphatase receptor type G, in nasopharyngeal carcinoma

Functional studies to identify the potential role of a chromosome 3p14-21 gene, protein tyrosine phosphatase receptor type G (PTPRG), were performed. PTPRG was identified as a candidate tumor suppressor gene (TSG) in nasopharyngeal carcinoma (NPC) by differential gene profiling of tumorigenic and nontumorigenic NPC chromosome 3 microcell hybrids (MCH). Down-regulation of this gene was found in tumor segregants when compared with their corresponding tumor-suppressive MCHs, as well as in NPC cell lines and tumor biopsies. Promoter hypermethylation and loss of heterozygosity were found to be important mechanisms contributing to PTPRG silencing. PTPRG overexpression in NPC cell lines induces growth suppression and reduced anchorage-independent growth in vitro. This is the first study to use a tetracycline-responsive vector expression system to study PTPRG stable transfectants. Results indicate its ability to induce significant tumor growth suppression in nude mice under conditions activating transgene expression. These studies now provide functional evidence indicating critical interactions of PTPRG in the extracellular matrix milieu induce cell arrest and changes in cell cycle status. This is associated with inhibition of pRB phosphorylation through down-regulation of cyclin D1. These novel findings enhance our current understanding of how PTPRG may contribute to tumorigenesis.

Identification of tumor suppressive activity by irradiation microcell-mediated chromosome transfer and involvement of alpha B-crystallin in nasopharyngeal carcinoma

In previous studies, we successfully refined nasopharyngeal carcinoma (NPC) critical regions (CRs) mapping to chromosome 11q13 and 11q22-23. The chromosome 11 fragment containing the 1.8 Mb NPC CR at 11q13 (CR1), the CR at 11q22.3 mapped near D11S2000 (CR2), part of the CR at 11q23.1-11q23.2 overlapping with D11S1300 and D11S1391 (CR3), and the CR at cell adhesion molecule 1 (CADM1) locus (CR4), was chosen as the chromosome 11 donor cell line for the present study. Gamma irradiation was applied to cleave this truncated chromosome into smaller fragments and a new panel of donor cells containing further deleted fragments was produced. Subclones XMCH3.2 and XMCH3.4 were chosen for subsequent transfer to HONE1 cells; each contains a single copy of deleted chromosome 11 fragment with or without CR2 and the THY1 locus, previously shown to be involved in NPC. Both resultant chromosome 11 fragments in XMCH3.2 and XMCH3.4 caused tumor suppression. The association of alpha B-crystallin (CRYAB), a gene identified as being differentially expressed by gene profiling of NPC and an immortalized nasopharyngeal epithelial cell line, and which is located near CR3, was found to be associated with tumor suppression in all the tumor-suppressive hybrids. In addition, the expression level of this gene was down-regulated in the 7 NPC cell lines and in 5 out of 14 normal/tumor tissue pairs in the present study. Both promoter hypermethylation and allelic loss may be involved in the inactivation of this gene, suggesting its possible role in NPC development.

TSLC1 is a tumor suppressor gene associated with metastasis in nasopharyngeal carcinoma

In up to 87% of nasopharyngeal carcinoma (NPC) clinical tumor specimens, there was either down-regulation or loss of TSLC1 gene expression. Using a tissue microarray and immunohistochemical staining, the frequency of down-regulated or loss of expression of TSLC1 in metastatic lymph node NPC was 83% and the frequency of loss of expression of TSLC1 was 35%, which was significantly higher than that in primary NPC (12%). To examine the possible growth-suppressive activity of TSLC1 in NPC, three NPC cell lines, HONE1, HNE1, and CNE2, were transfected with the wild-type TSLC1 gene cloned into the pCR3.1 expression vector; a reduction of colony formation ability was observed for all three cell lines. A tetracycline-inducible expression vector, pETE-Bsd, was also used to obtain stable transfectants of TSLC1. There was a dramatic difference between colony formation ability in the presence or absence of doxycycline when the gene is shut off or expressed, respectively, with the tetracycline-inducible system. Tumorigenicity assay results show that the activation of TSLC1 suppresses tumor formation in nude mice and functional inactivation of this gene is observed in all the tumors derived from tumorigenic transfectants. Further studies indicate that expression of TSLC1 inhibits HONE1 cell growth in vitro by arresting cells in G(0)-G(1) phase in normal culture conditions, whereas in the absence of serum, TSLC1 induced apoptosis. These findings suggest that TSLC1 is a tumor suppressor gene in NPC, which is significantly associated with lymph node metastases.

Functional studies of the chromosome 3p21.3 candidate tumor suppressor geneBLU/ZMYND10 in nasopharyngeal carcinoma

Chromosome 3p plays an important role in tumorigenesis in many cancers, including nasopharyngeal carcinoma (NPC). We have previously shown chromosome 3p can suppress tumor growth in vivo by using the monochromosome transfer approach, which indicated the chromosome 3p21.3 region was critical for tumor suppression. BLU/ZMYND10 is one of the candidate tumor suppressor genes mapping in the 3p21.3 critical region and is a candidate TSG for NPC. By quantitative RT-PCR, it is frequently downregulated in NPC cell lines (83%) and NPC biopsies (80%). However, no functional studies have yet verified the functional role of BLU/ZMYND10 as a tumor suppressor gene. In the current study, a gene inactivation test (GIT) utilizing a tetracycline regulation system was used to study the functional role of BLU/ZMYND10. When BLU/ZMYND10 is expressed in the absence of doxycycline, the stable transfectants were able to induce tumor suppression in nude mice. In contrast, downregulation of BLU/ZMYND10 in these tumor suppressive clones by doxycycline treatment restored the tumor formation ability. This study provides the first significant evidence to demonstrate BLU/ZMYND10 can functionally suppress tumor formation in vivo and is, therefore, likely to be one of the candidate tumor suppressor genes involved in NPC.

THY1 is a candidate tumour suppressor gene with decreased expression in metastatic nasopharyngeal carcinoma

Using oligonucleotide microarray analysis, THY1, mapping close to a previously defined 11q22-23 nasopharyngeal carcinoma (NPC) critical region was identified as showing consistent downregulated expression in the tumour segregants, as compared to their parental tumour-suppressing microcell hybrids (MCHs). Gene expression and protein analyses show that THY1 was not expressed in the NPC HONE1 recipient cells, tumour segregants, and other NPC cell lines; THY1 was exclusively expressed in the non-tumourigenic MCHs. The mechanism of THY1 gene inactivation in these cell lines was attributed to hypermethylation. Clinical study showed that in 65% of NPC specimens there was either downregulation or loss of THY1 gene expression. Using a tissue microarray and immunohistochemical staining, 44% of the NPC cases showed downregulated expression of THY1 and 9% lost THY1 expression. The frequency of THY1 downregulated expression in lymph node metastatic NPC was 63%, which was significantly higher than in the primary tumour (33%). After transfection of THY1 gene into HONE1 cells, a dramatic reduction of colony formation ability was observed. These findings suggest that THY1 is a good candidate tumour suppressor gene in NPC, which is significantly associated with lymph node metastases.

Fine mapping of the 11q22-23 tumor suppressive region and involvement of TSLC1 in nasopharyngeal carcinoma

Previous studies transferring an intact chromosome 11 into HONE1 cells demonstrated the functional significance of chromosome regions, 11q13 and 11q22-23, in nasopharyngeal carcinoma (NPC) development. In our study the 11q22-23 region was comprehensively re-investigated by detailed microsatellite and single nucleotide polymorphism genotyping and by fluorescence in situ hybridization to map precisely the regions containing tumor suppressive activity. We observed 3 chromosomal intervals within 11q22-23 that were commonly lost in the tumor segregants derived from HONE1/chromosome 11 hybrids. One critical region of 0.36 Mb was mapped near the marker D11S2000 and a second 0.44 Mb region was located around the markers D11S1300 and D11S1391. In a third region high allelic loss was also observed at marker D11S4484, where a newly cloned tumor suppressor gene, TSLC1 (tumor suppressor in lung cancer 1), is located. The gene expression analysis showed absence or low expression levels of TSLC1 mRNA in 4 highly tumorigenic NPC cell lines. In addition, the methylation study results show that the TSLC1 promoter region was hypermethylated in all 4 NPC cell lines and re-expression of the gene occurs in HONE1 cells after 5-aza-2'-deoxycytidine treatment. Hence, the mode of silencing of this candidate TSG in NPC may be attributed to promoter hypermethylation. We have obtained functional evidence for multiple critical tumor suppressive regions in 11q22-23 by fine deletion mapping and for inactivation of TSLC1 being one of these candidate TSGs in NPC development.