Abstract 5835: Functional and mechanistic characterization of ΔNp63α in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is highly prevalent in Asia with a poor prognosis and a high mortality rate [1, 2]. The p63 protein, encoded by TP63, is a master regulator involved in many cell events including cell cycle, DNA damage, cell proliferation, stem cell maintenance, and cell death in different cancer types. ΔNp63α is the dominantly expressed isoform of p63 in squamous cell carcinomas, playing a critical role in tumorigenesis [3, 4]. However, the functional roles of ΔNp63α in ESCC have not been fully elucidated. Our results have revealed that ΔNp63α is highly expressed and up-regulated in ESCC. We have shown that ΔNp63α protein expression plays an oncogenic role in ESCC cells, depletion of which inhibits in vitro cell proliferation and colony formation and greatly suppresses in vivo tumor growth, in a panel of ESCC cell lines and our latest patient-derived organoid cultures, potentially in a differentiation-dependent manner. Glycolysis pathway and two novel downstream signaling pathways of ΔNp63α, MYC/4EBP1 and AKT/NDRG1, are significantly suppressed upon ΔNp63α depletion in ESCC cell lines. Notably, xenografts of ΔNp63α-depleted human ESCC cells show elevated infiltrating cancer-associated fibroblasts (CAFs), which may contribute to tumor suppression by ΔNp63α depletion. These data not only shed light on the ΔNp63α functions and how they contribute to the ESCC tumorigenesis, but also unravel potential therapeutic benefits for ESCC patients in the future. Acknowledgements: We acknowledge DSMZ (German Collection of Microorganisms and Cell Culture) for the KYSE cell lines. We acknowledge the Research Grants Council Theme-Based Research Scheme grant T12-701/17-R to MLL. References [1] Chen, W., et al., Cancer statistics in China, 2015. CA Cancer J Clin, 2016. 66(2): p. 115-32. [2] Peng, L., et al., CCGD-ESCC: A Comprehensive Database for Genetic Variants Associated with Esophageal Squamous Cell Carcinoma in Chinese Population. Genomics Proteomics Bioinformatics, 2018. 16(4): p. 262-268. [3] Fukunishi, N., et al., Induction of DeltaNp63 by the newly identified keratinocyte-specific transforming growth factor beta Signaling Pathway with Smad2 and IkappaB Kinase alpha in squamous cell carcinoma. Neoplasia, 2010. 12(12): p. 969-79. [4] Moses, M.A., et al., Molecular Mechanisms of p63-Mediated Squamous Cancer Pathogenesis. Int J Mol Sci, 2019. 20(14).

Citation Format: Shan Shan So, Valen Z. Yu, Simon Y. Law, Maria L. Lung. Functional and mechanistic characterization of ΔNp63α in esophageal squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5835.

Abstract 6016: Patient-derived tumor organoid cultures identify a chemo-resistant sub-population in esophageal squamous cell carcinoma

Background: Patient-derived xenograft has been a gold standard for cancer modeling. However, low establishment efficiency and high maintenance cost have hindered the development in the field. In recent years, patient-derived tumor organoid culture has been developed as an efficient and economic model to mimic and recapitulate the original tumor tissue, in contrast to conventional cancer cell lines and patient-derived xenografts (Drost & Clevers, 2018). Due to the limited availability of current esophageal squamous cell carcinoma (ESCC) models, we aimed to establish a panel of ESCC patient-derived organoid (PDO) long-term cultures for ESCC study.

Results: In the current project, we have established and biobanked a panel of ESCC PDO cultures in vitro from Chinese ESCC treatment-naïve patients undergoing an endoscopic examination or upfront surgery, or patients undergoing neoadjuvant chemoradiotherapy (CRT) followed by surgery in Hong Kong. We also established and maintained PDO-derived xenograft (PDOX) in immunocompromised mice. Immunohistochemical examination confirmed the squamous origin of the established PDOs and PDOXs. Genomic profiling showed consistent mutational landscapes of the established PDO, as compared to ESCC patient profiles. Transcriptomic profiling suggests organoid culture resembles patient tissue samples better than the cell line model in terms of global gene expression patterns. Notably, PDOs from CRT-treated patients show enhanced re-growth after recovery from cisplatin treatment, indicating a candidate cancer stem cell (CSC) sub-population enriched by neoadjuvant CRT. This sub-population can be further enriched in vitro by serial cisplatin treatment and recovery cycles.

Conclusions: ESCC PDOs can be efficiently established from highly limited patient tissue samples and maintained long-term in vitro and can be feasibly integrated with mouse model. It preserves the original cell hierarchy and indicates existence of candidate CSC sub-population, which may be targeted therapeutically in future.

Reference: Drost J, Clevers H. Organoids in cancer research. Nat Rev Cancer. 2018 Jul; 18(7).

Acknowledgment: We acknowledge the Research Grants Council (Theme-based Research Scheme T12-701/17-R to MLL) and the Food and Health Bureau (Health and Medical Research Fund 06171566 to VZY) of Hong Kong Special Administrative Region for funding supports. We acknowledge DSMZ (German Collection of Microorganisms and Cell Culture) for the KYSE cell lines. We acknowledge the University of Hong Kong Faculty of Medicine Core Facility for providing imaging facilities.

Citation Format: Valen Z. Yu, Bryan C. Lung, Ian Y. Wong, Claudia L. Wong, Simon Y. Law, Maria L. Lung. Patient-derived tumor organoid cultures identify a chemo-resistant sub-population in esophageal squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6016.

Abstract 5371: Real-time serial monitoring of liquid biopsies allows earlier detection of treatment responses and relapse for metastatic esophageal squamous cell carcinoma

Purpose: Esophageal squamous cell carcinoma (ESCC) is a deadly cancer, frequently diagnosed at advanced stages, when it has already metastasized, making treatment difficult and survival low. We utilized liquid biopsies from ESCC patients for real-time monitoring of treatment responses and detection of relapse and metastasis. We aimed to determine the usefulness of circulating tumor biomarkers for monitoring disease burden and provide real-time assessment of the evolving tumor under treatment pressure.

Experimental methods: Blood was collected from metastatic ESCC patients before, during, and at the end of treatment. It was processed to lyse red blood cells and enrich for circulating tumor cells (CTCs). Spiral microfluidics chips for size separation enriched for larger CTCs and removed smaller white blood cells. CTC enumeration was performed by immunofluorescence staining using antibody cocktails [pan-cytokeratin (CK), epithelial cell adhesion molecule (EpCAM), and clusters of differentiation 45 (CD-45)]. We performed next-generation sequencing (NGS) target capture analysis for a customized 300-gene panel of selected cancer-relevant and druggable genes. cfDNAs extracted from plasma were utilized to determine mutation profiles for circulating tumor DNA (ctDNA) with the Roche AVENIO ctDNA 77-gene pan-cancer kit. Mutations or amplifications detected were validated by Sanger sequencing or digital PCR.

Summary: The sensitivity and specificity of the cfDNA platform was determined using in-house controls with known mutations, which were validated by digital PCR. At the baseline timepoint, genetic alterations were detected in 90.3% of 31 ESCC patients. TP53 gene was the most frequently mutated with point mutations detected in 77% of ESCC patients and EGFR gains in 19% of patients. Longitudinal cfDNA analysis showed good concordance between mutant allele frequency and tumor mutation burden, suggesting the usefulness of real-time non-invasive monitoring to detect minimal residual disease. Analysis of cfDNAs also provides the opportunity to determine the extent of inter-tumoral heterogeneity between primary and metastatic tumors. Our preliminary data show CTC enumeration at ~6 weeks pre-cycle III for patients treated with palliative CT and at end of chemo-radiation therapy (CRT) for locally advanced ESCC patients, may be useful prognostic and predictive biomarkers for treatment efficacy and to gauge risk relapse and survival. Ongoing studies will increase sample sizes. The clinical relevance of serial CTC enumeration data and the cfDNA and CTC mutational load detected will be correlated with disease progression to determine their usefulness for prognostication.

Conclusions: Serial analysis of CTCs and ctDNAs of metastatic ESCC patients indicates the usefulness of real-time monitoring using liquid biopsies to assess tumor mutation burden and to predict treatment efficacy, disease relapse, and patient survival.

Acknowledgements: TBRS grant T12-701/17R and HMRF grant 05160926 to MLL

Citation Format: Josephine M. KO, Bianca H. NG, Maria L. Lung. Real-time serial monitoring of liquid biopsies allows earlier detection of treatment responses and relapse for metastatic esophageal squamous cell carcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5371.

Germline Polymorphisms and Length of Survival of Nasopharyngeal Carcinoma: An Exome-Wide Association Study in Multiple Cohorts

Germline polymorphisms are linked with differential survival outcomes in cancers but are not well studied in nasopharyngeal carcinoma (NPC). Here, a two-phase association study is conducted to discover germline polymorphisms that are associated with the prognosis of NPC. The discovery phase includes two consecutive hospital cohorts of patients with NPC from Southern China. Exome-wide genotypes at 246 173 single nucleotide polymorphisms (SNPs) are determined, followed by survival analysis for each SNP under Cox proportional hazard regression model. Candidate SNP is replicated in another two independent cohorts from Southern China and Singapore. Meta-analysis of all samples (n = 5553) confirms that the presence of rs1131636-T, located in the 3'-UTR of RPA1, confers an inferior overall survival (HR = 1.33, 95% CI = 1.20-1.47, P = 6.31 × 10-8). Bioinformatics and biological assays show that rs1131636 has regulatory effects on upstream RPA1. Functional studies further demonstrate that RPA1 promotes the growth, invasion, migration, and radioresistance of NPC cells. Additionally, miR-1253 is identified as a suppressor for RPA1 expression, likely through regulation of its binding affinity to rs1131636 locus. Collectively, these findings provide a promising biomarker aiding in stratifying patients with poor survival, as well as a potential drug target for NPC.

Orthotopic Xenograft Mouse Model in Esophageal Squamous Cell Carcinoma

Orthotopic xenograft model recapitulates the faithful organ-specific microenvironment and facilitates analyses involving tumor-stromal interactions that are crucial for developing new-generation cancer therapy. Herein, we describe the detailed rationales and protocols of a versatile orthotopic xenograft model for esophageal squamous cell carcinoma.

Functional characterization of a candidate tumor suppressor gene, Mirror Image Polydactyly 1, in nasopharyngeal carcinoma

Mirror Image Polydactyly 1 (MIPOL1) is generally associated with congenital anomalies. However, its role in cancer development is poorly understood. Previously, by utilizing the functional complementation approach, microcell-mediated chromosome transfer (MMCT), a tumor suppressor gene, MIPOL1, was identified. MIPOL1 was confirmed to be downregulated in nasopharyngeal carcinoma (NPC) cells and tumor tissues, and re-expression of MIPOL1 induced tumor suppression. The aim of the current study is to further elucidate the functional tumor suppressive role of MIPOL1. In our study, with an expanded sample size of different clinical stages of NPC tumor tissues, we further confirmed the downregulation of MIPOL1 in different cancer stages. MIPOL1 re-expression down-regulated angiogenic factors and reduced phosphorylation of metastasis-associated proteins including AKT, p65, and FAK. In addition, MIPOL1 was confirmed to interact with a tumor suppressor, RhoB, and re-expression of MIPOL1 enhanced RhoB activity. The functional role of MIPOL1 was further validated by utilizing a panel of wild-type (WT) and truncated MIPOL1 expression constructs. The MIPOL1 tumor-suppressive effect can only be observed in the WT MIPOL1-expressing cells. In vitro and nude mice in vivo functional studies further confirmed the critical role of WT MIPOL1 in inhibiting migration, invasion and metastasis in NPC. Overall, our study provides strong evidence about the tumor-suppressive role of MIPOL1 in inhibiting angiogenesis and metastasis in NPC.

Prospective, Multicenter, Phase 2 Trial of Induction Chemotherapy Followed by Bio-Chemoradiotherapy for Locally Advanced Recurrent Nasopharyngeal Carcinoma

PURPOSE

To evaluate, in a phase 2 study, whether induction docetaxel, cisplatin, and fluorouracil (TPF) followed by weekly docetaxel and cetuximab in concurrence with intensity modulated radiation therapy can improve the treatment outcome for patients with advanced locally recurrent nasopharyngeal carcinoma (rNPC).

METHODS AND MATERIALS

Thirty-three patients with rNPC (T3-T4, N0-N1, M0) were recruited. Of these, 19 patients (57.6%) had stage rT3 recurrence, and the rest had stage rT4. Eight patients also had rN1 at the time of relapse. Treatment outcomes and safety were evaluated.

RESULTS

Among these 33 patients, 1 died after 1 cycle of TPF, 5 patients withdrew from the study during the induction period because of grade ≥3 toxicities; 27 patients completed the whole course of treatment, but 1 died before any assessment could be made. The median follow-up period was 28.5 months. The progression-free survival and overall survival at 3 years for the whole group were 35.7% and 63.8%, respectively. Among the 26 patients who could be assessed after treatment, the complete response rate was 30.8%, and the locoregional control rate at 3 years was 49.2%. Temporal lobe necrosis (TLN) developed in 8 cases. The rates of grade ≥3 hearing loss, soft tissue necrosis, dysphagia, and trismus were 30.8%, 15.4%, 11.5%, and 19.2%, respectively. Overall, 5 patients died owing to acute (1 after cycle 1 TPF and 1 after completion of bio-chemoradiotherapy) or late (2 epistaxis and 1 TLN) treatment-related complications.

CONCLUSIONS

The proposed salvage treatment regimen for advanced locally recurrent NPC could achieve a better treatment outcome than seen in previous studies. However, poor tolerability of induction TPF and the high rate of TLN limit its applicability outside clinical trials.

Abstract 4522: Epstein-Barr virus infection suppresses the DNA repair mechanisms in nasopharyngeal epithelial cells via reduction of the H3K4me3 mark

Introduction: Epstein-Barr Virus (EBV) is an oncovirus, which contributes to development of various cancers, including nasopharyngeal carcinoma (NPC). EBV latent proteins play critical roles in modulation host cell histone modifications in order to regulate its signaling pathways. However, the role of EBV in regulation histone modifications in epithelia cell system is still not very clear. Further studies are necessary to characterize the functional role of EBV in regulating epithelial cell modifications.

Aim: in this current study, we aim to investigate the role of EBV infection in regulating a promoter and transcription activation histone marker, H3K4me3, in the host cell genome.

Methodologies: Chromatin immunoprecipitation sequencing (ChIPseq) was performed by using the next-generation sequencing approach. The ChIP reactions were prepared by utilizing the antibody targeting the H3K4me3 mark in two pairs of immortalized non-tumorigenic nasopharyngeal epithelial (NPE) cell lines, which were artificially infected with (550, 550-EBV, 361, and 361-EBV). The ChIPseq results were validated by the ChIP-QPCR and RT-QPCR.

Results: A total of 1747 genes show losses of H3K4me3 in both sets of EBV-infected NPE cell lines. Among them, 628 (36%) genes show losses of H3K4me3 in promoter regions. Interestingly, a total of 18 DNA damage repair signaling members in the base excision repair (BER), homologous recombination, non-homologous end-joining, and the mismatch repair pathways showed significant losses of H3K4me3 in EBV-infected NPE cells. Based on utilizing the DAVID annotation tool for pathway analysis, members in the BER pathway were significantly enriched (FDR = 0.0709, cut-off<0.1). The ChIPseq results were validated by ChIP- and RT-QPCR and showed significant losses of the H3K4me3 and expression of the BER members in both sets of EBV-infected NPE cell lines. The clinical significances were further confirmed by detection of significant down-regulation of the BER members in NPC paired biopsies.

Conclusion: EBV infection induces changes of host cell H3K4me3 levels and results in down-regulation of the BER members.

Acknowledgement: This work was supported by the Research Grants Council of the Hong Kong Special Administrative Region, People's Republic of China: Grant number AoE/M-06/08 to MLL and the Seed Funding Programme for Basic Research of the University of Hong Kong: Grant number 201308159003 to AKLC.

Citation Format: Maria L. Lung, Arthur KL Cheung, Wei Dai, Merrin ML Leong, George SW Tsao. Epstein-Barr virus infection suppresses the DNA repair mechanisms in nasopharyngeal epithelial cells via reduction of the H3K4me3 mark. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4522.

Abstract 125: Whole-exome sequencing identifies NF-kappaB pathway regulators frequently mutated in nasopharyngeal carcinoma

Introduction

Nasopharyngeal carcinoma (NPC) is a unique epithelial malignancy with a high prevalence in Southeast Asia. To date, the genomic abnormalities leading to the pathogenesis of NPC remain unclear. Thus, we sought to characterize the mutational landscape in NPC tumors using next-generation sequencing approaches and to identify significantly mutated genes and pathways.

Methods

124 NPC primary tumors were examined to define the mutational landscape with whole-exome sequencing (WES) and targeted re-sequencing. Mean target coverage of tumor and blood samples was 70X and 49X in WES, and 190X and 68X in targeted resequencing, respectively. Somatic SNPs and INDELs were called with MuTect and VarScan2, respectively. MutSigCV was applied to identify potential driver events in tumorigenesis. Verification rate for somatic mutations was 95%. The functional consequences of mutations in candidate genes were evaluated by the luciferase promoter, cell proliferation, and colony formation assays.

Results

The mutation rate of NPC is relatively low, with a median of 0.9 somatic mutations per megabase. Mutational signature analysis revealed two signatures in NPC, the ubiquitous signature in cancer characterized by C>T transitions predominantly occurring at NpCpG trinucleotides and the APOBEC-related signature characterized by C>G and C>T mutations at TpCpN trinucleotides, which is related to the innate immune APOBEC family of cytidine deaminases.

MutSigCV analysis identified significantly mutated genes, NFKBIA, TP53, CYLD, KMT2D, DMXL1, KMT2C, GPR144, RYR2, BOD1L1, AKAP9, and CEP192, with q values less than 0.1. Pathway and gene ontology analysis identified several pathways/terms with enriched somatic mutations including cell cycle phase transition, chromatin modification, cell death, immune response, p53 pathway, viral carcinogenesis, and the canonical NF-κB signaling pathways. TP53 is the most frequently mutated gene (7.3%, 9/124). Almost all somatic mutations fall into the DNA binding domain of TP53, including well-known hotspot and gain-of-function mutations.

Multiple loss-of-function (LOF) mutations were detected in NF-kB negative regulators, including NFKBIA (encodes IκBα protein), CYLD, and TNFAIP3. Mutations in NFKBIA were shown to alter the tumor suppressive function of IκBα.

Conclusions

In this study we detected an APOBEC-related signature in NPC. Several NF-kB negative regulators, including NFKBIA and CYLD, were mutated in a subset of NPC primary tumors, which may contribute to pathogenesis of NPC through NF-kB signaling pathway. These data provide an enhanced road map for understanding the molecular basis underlying NPC and also provide insight for exploring new therapies.

Acknowledgement

This work was supported by the Research Grants Council of the Hong Kong Special Administrative Region, People's Republic of China Grant number AoE/M006/08 to MLL.

Citation Format: Hong Zheng, Wei Dai, Arthur KL Cheung, Josephine MY Ko, Rebecca Kan, Bonnie WY Wong, Merrin ML Leong, Maria L. Lung. Whole-exome sequencing identifies NF-kappaB pathway regulators frequently mutated in nasopharyngeal carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 125.

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 4148: Adverse effects of TERT-CLPTM1L and double-strand breaks repair contribute to risk for nasopharyngeal carcinoma

Background and Aims The genetic etiology of NPC and mechanisms for inherited susceptibility remain unclear. Only modest low-penetrance effects of cancer-predisposing common variant SNPs were previously identified in the few large-scale NPC association studies reported. Most NPC association studies focused on single or limited candidate genes with modest sample sizes. Systematic and comprehensive study designs for evaluation of higher order gene-gene interactions are scanty. A large-scale NPC case-control SNP association study was performed to examine the genetic risk factors for NPC development. In order to elucidate the genetic susceptibility for NPC, we hypothesized that heritable risk is attributable to cumulative effects of common low-risk variants, especially for genes in DNA repair pathways.

Material and Methods Genotype screening of 377 SNPs and validation in an 81-SNP panel of DNA repair and other genes in 2349 individuals from Hong Kong (1177 cases and 1172 controls) using iPLEX Gold assays with the MassARRAY platform were performed for association analyses for risk allele identification and pathway-based studies for NPC. All statistical tests were two-sided.

Results Three SNPs (rs401681, rs6774494, rs3757318) corresponding to TERT/CLPTM1L (OR 0.77, 95% CI 0.68-0.88), MDS1-EVI1 (OR 0.79, 95% CI 0.69-0.89), and CCDC170 (OR 0.76, 95% CI 0.66-0.86) conferred modest protective effects individually for NPC risk by the logistic regression (pBonferroni <0.05) (Table II).

Stratification of NPC according to familial status identified rs2380165 in BLM (OR 1.49, 95% CI 1.20-1.86) association with family history-positive NPC (FH+NPC) patients (pBonferroni <0.05) (Table III).

Higher order multiple SNPs pathway-based analysis revealed that the combined adverse effects of TERT-CLPTM1L and double-strand break repair (DSBR) (HR, NHEJ, FA-BS, and FA-HR pathways) conferred significant elevated risk up to OR 5.6 (95% CI 2.67-11.78) in FH+NPC and 2.4 (95% CI 1.28-4.48) in sporadic NPC patients carrying five adverse alleles in TERT/NHEJ and TERT/FA/BS pathways, respectively. (Fig. 2,3)

Conclusions Three SNPs corresponding to MDS1-EVI1, TERT/CLPTM1L, and CCDC170 conferred modest protective effects individually for NPC risk in Hong Kong patients. Importance of pathway-based analysis for the cumulative increased risk associations with TERT locus and DNA repair pathways for DBS repair play a critical role in determining genetic susceptibility to NPC. A SNP in BLM is associated with FH+NPC patients. Pathway-based analysis also showed that the cumulative effect is more pronounced in FH+NPC patients.

Aknowledgements Hong Kong Research Grants Council Area of Excellence grant (AoE/M-06/08)

Citation Format: Maria L. Lung, Josephine Ko, Wei Dai, Elibe Wong, Dora Kwong, Wai Tong Ng, Anne Lee, Roger Ngan, Chun Chung Yau, Stewart Tung. Adverse effects of TERT-CLPTM1L and double-strand breaks repair contribute to risk for 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 4148. doi:10.1158/1538-7445.AM2014-4148

Abstract 2298: Methylated gene markers discovered in nasopharyngeal carcinoma by differential methylation hybridization (DMH) in high density CpG island DNA chips

Nasopharyngeal carcinoma (NPC) is a prevalent cancer in southern China and south east Asian countries. A variety of tumor suppressor (TS) genes including p16, RASSF1A, EDNRB, DAP-Kinase, RIZ1, E-Cadherin were found to be hypermethylated in NPC. This, however, could only be the tip of an iceberg. We made use of the high throughput differential methylation hybridization (DMH) technique in screening for methylated DNA markers in 244K CpG island DNA chip in three NPC xenografts (C15, C17, 99-186), a NPC tumor cell line (C666) versus an immortalized NP non-cancer cell line (NP69). This DMH screening discovered 100, 213, 372 and 977 genes respectively in 99-186, C17, C15 and C666 with ≥ 5 CpG sites in their gene promotors being methylated. Among these genes, 28 of them were found to have DNA methylation in all the 4 NPC xenografts/ tumor cell line. Bisulphite sequencing was performed in 17 pairs of tumor and normal biopsy samples from 17 NPC patients. This confirmed tumor specific methylation in the promotor regions of 8 gene markers, namely, NRP3, PCDH10, PENK, ADHFE1, IRX4, GSC, PFN2 & GFI1 with positive methylation ratios (+ve MR) in tumor biopsies of 86.7%, 85.7%, 80%, 72.7%, 54.5%, 50%, 41.7% &23.1% respectively and +ve MR of 18.2%, 0%, 0%, 0%, 0%, 37.5%, 12.5% & 0% respectively in normal biopsies. Methylation of CpG sites appears to occur either all or none with 15 to 45 consecutive CpG sites in these genes either all methylated or non-methylated in tumor biopsies probably indicating the need of methylation of a full cluster of CpG sites in order to affect the gene transcription of the discovered genes. Functions of the DMH identified genes includes cell adhesion (PCDH10), signal transduction (PENK), chloride ion binding (NPR3), regulation of DNA dependent transcription (IRX4) and xenobiotic metabolism (ADHFE1). In fact, PCDH10, PENK and GFI1 genes have been reported to be closely associated with NPC/esophageal carcinoma, pancreatic adenocarinoma and T-cell lymphoma respectively. Further analyses in these methylated markers could be useful in the diagnosis and study of etiology of NPC.

Citation Format: Wai Wai Cheng, Roger K.C. Ngan, Dora L.W. Kwong, Tim H.M. Huang, Victor W.S. Ma, Stephen C.K. Law, Loretta Tse, Pierre Busson, George S.W. Tsao, Maria Li Lung, Timothy T.C. Yip. Methylated gene markers discovered in nasopharyngeal carcinoma by differential methylation hybridization (DMH) in high density CpG island DNA chips. [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 2298. doi:10.1158/1538-7445.AM2014-2298

Abstract 1938: Inhibition of both physiological and aberrant Wnt/β-catenin signaling activities associated with stemness in nasopharyngeal carcinoma

We previously demonstrated that basic or physiological levels of β-catenin signaling and tissue context play decisional roles in the regulation of self-renewal networks in nasopharyngeal carcinoma (NPC) HONE1 cells. Introduction of physiological levels of β-catenin signaling in HONE1 hybrid cells plays a central role in the control of other pathway activities, such as TGF-β, Activin, and pluripotency maintenance (LIFR and IL6ST), during the stemness transition process. These results revealed novel regulatory relationships among Wnt signaling, stemness, epithelial-mesenchymal transition (EMT), tumor suppressive pathways and expression of common cancer stem cell surface markers, such as CD44 and CD133, in human tumor cells. In current studies, we found that several NPC cell lines, including CNE1, HK1, HNE1, SUNE1, and C666-1, have aberrant and significant up-regulation of β-catenin expression, when compared to HONE1 cells that have low levels endogenous β-catenin expression. In these NPC cells with aberrant β-catenin signaling activities, the Wnt pathway (Axin2, APC, TCF1 and TCF3), stemness factors (Nanog, and Oct4) and pluripotency markers (IFITM1 and GRB7) are strongly overexpressed, compared to HONE1 cells. Our findings suggest that aberrant Wnt/β-catenin signaling activities may play a prominent role in promoting tumor progression in NPC cells. To further verify the role of aberrant β-catenin signaling in NPC, we utilize shRNA to knock down β-catenin expression in these cells, including CNE1 and HK1. As found in HONE1 hybrids, the diminished expression of core stem cell factors (Nanog, Oct4, Klf4, and Sox2) is also detected in both CNE1 and HK1 cell lines. Concomitantly, the gene expression of EMT markers (E-cadherin and Zeb1) is also inhibited when β-catenin is knocked down by shRNA β-catenin infection. These preliminary results suggest that β-catenin signaling plays a dominant role in regulating both physiological and aberrant Wnt/β-catenin signaling activities as well as EMT events in NPC development.

Citation Format: Yue Cheng, Yee Peng Phoon, Maria L. Lung. Inhibition of both physiological and aberrant Wnt/β-catenin signaling activities associated with stemness 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 1938. doi:10.1158/1538-7445.AM2014-1938

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.

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 2637: Application of identity-by-descent (IBD) approach to genetic mapping of susceptibility locus in hereditary esophageal squamous cell carcinoma (ESCC) by high density SNP array analysis

Background and aims: Esophageal cancer (EC) is a deadly disease with a very low 5-year survival rate. The incidence of EC shows great geographical variations with high prevalence in Northern China. Although epidemiological studies suggest that environmental factors may be etiologic factors of EC, strong evidence supporting a causative role of genetic factors in familial EC comes from i) familial aggregation of EC in Yangcheng County, ii) the distinct high EC incidence in Chaoshan migrants to Nanao, and iii) molecular genetic studies such as BRCA2 germline mutations. Recent technological advances allow the identification of long regions of homozygosity (known as IBD segments) in genomic DNAs, which represent the sharing of a common ancestor in those regions, using the high density SNP arrays. Previous studies suggest that a high rate of consanguinity, which produces germline genomic homozygosity, is associated with cancers. We aim to use the IBD approach for mapping the susceptibility locus with low-penetrance SNPs in hereditary ESCC patients in Henan, one of the highest ESCC risk regions in the world. Screening programs based on knowledge of founder mutations may reduce cancer mortality by prevention. Thus, our second aim is to assess if a founder effect exists and predisposes individuals to ESCC in Henan. Methods: Genomic DNAs were extracted from blood samples of Henan family history positive (FH+) ESCC patients and healthy normal individuals. The germline homozygosity in 30 Henan FH+ ESCC patients was explored by using Affymetrix GeneChip Human mapping SNP array (∼238K SNPs, Sty I). IBD analysis was performed using the PLink software. Results: There is longer IBD segment length associated with FH+ ESCC compared with control groups. The 27 IBD segments in FH+ ESCC samples having no overlap with control/Hapmap may encompass the potential cancer-susceptibility loci and should be further examined. However, no strong evidence for founder effect was observed by IBD approach for hereditary ESCC in Henan population. Conclusions: The increased length of germline genomic homozygosity association with hereditary ESCC in Henan is observed. Due to the small sample size in the current study, the association is considered hypothesis-generating only. The importance of these IBD segments to the etiology and development of ESCC in high risk areas require further study with an expanded sample size for validation. Acknowledgements: This work was supported by the Research Grants Council of the Hong Kong Special Administrative Region, People's Republic of China (HKU 3/06C to M.L.L.).

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 2637. doi:1538-7445.AM2012-2637

Abstract 420: Physiological β-catenin signaling regulates pluripotency genes in cancer microcell hybrids

Both β-catenin signaling and Nanog were previously reported to be involved in cell fusion-mediated somatic cell reprogramming. It remains unclear as to how the β-catenin signaling pathway is initiated and whether this pathway may directly control the expression of core stem cell factors such as Nanog and Oct4. Since β-catenin signaling is a predominating force for the regulation of cellular fate and basic levels of this signaling are needed for somatic cell reprogramming, we speculate that transfer of a single copy of chromosome 3, where β-catenin maps and is controlled by its natural regulators, into somatic cancer cells may appropriately induce this pathway and switch on the expression of endogenous pluripotency genes in recipient cells. We previously generated human nasopharyngeal (HONE1) and esophageal (SLMT1) carcinoma hybrid cells with an intact copy of transferred chromosome 3. At both transcriptional and translational levels, we detected obvious expression of genes related to the Wnt/β-catenin pathway in HONE1/chromosome 3 hybrid cells. In these hybrid cells, β-catenin, c-Myc, Axin2, Tcf1, Sox2, Klf4, Oct4, and Nanog were either strongly expressed or up-regulated. The loss of region that contains B-catenin locus in transferred chromosome 3 abolishes the expression of core stem cell genes. The control of these gene activities by physiological β-catenin signaling was further confirmed in HONE1/chromosome 17 hybrids that contain the downstream components of β-catenin signaling Axin2 and Stat3, but was not detected in hybrids with an irrelevant transferred chromosome and SLMT1 cells that had a relatively high level of endogenous β-catenin expression. We also found that HONE1 hybrid cells have stem cell-like properties, including spheroid formation, up-regulation of CD24+ and CD44+ populations and expression of various embryonic markers. Additionally, chromosome 3 transfer induced epithelial-mesenchymal transformation (EMT) events in HONE1 cells that caused different expression of adhesion molecules and up-regulation of their regulators and other markers such as Twist, Snail, Slug, ZEB1, Sip1, and E-cadherin. As expected, we detected that p53, Rb1, and Smad2 involved pathways were activated in HONE1 hybrid cells, suggesting that physiological β-catenin signaling, via multiple signaling pathways, regulates both pluripotency networks and EMT events.

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 420. doi:1538-7445.AM2012-420

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.

Role of STAT3/5 and Bcl-2/xL in 2-methoxyestradiol-induced endoreduplication of nasopharyngeal carcinoma cells

2-methoxyestradiol (2ME2), an endogenous metabolite of 17-β-estradiol, has been shown to induce apoptosis and cell cycle arrest in various tumor models. We have previously shown that 2ME2 induced endoreduplication in a well-differentiated nasopharyngeal carcinoma (NPC) HK-1 and a poorly differentiated C666-1 cell line. In the present study, we studied the survival factors involved in 2ME2-induced endoreduplicating NPC cells. In the HK-1 cells, knockdown of BcL-xL expression by siRNA resulted in the reduction of endoreduplication and an increase in the percentage of apoptosis. Further mechanistic study revealed that 2ME2 enhanced the expression of the phosphorylated form of STAT5 (p-STAT5-Y694), but not p-STAT3 (Y705) and p-STAT3 (S727), in the nucleus of HK-1 cells. Pre-treatment of cells with JAK/STAT inhibitor AG490 and STAT5 inhibitor resulted not only in the reduced expression of Bcl-xL, but also reduced the percentage of endoreduplicating cells. In contrast, 2ME2 enhanced the expression of p-STAT3 in the poorly differentiated C666-1 cells. Pharmacological inhibition of STAT3 or Bcl-2/xL resulted in a decrease in endoreduplication of C666-1 cells. Taken together, the expression of p-STAT5 and p-STAT3 was upregulated in 2ME2-induced endoreduplicating HK-1 and C666-1 cells, respectively. Combination of 2ME2 with Bcl-2/xL inhibitor is a novel strategy to reduce the formation of endoreduplicating cells during chemotherapeutic treatment of NPC. © 2011 Wiley Periodicals, Inc.

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.

Role of p38 MAPKs in hypericin photodynamic therapy-induced apoptosis of nasopharyngeal carcinoma cells

The present study aims to determine the role of mitogen-activated protein kinases (MAPKs) in hypericin-mediated photodynamic therapy (HY-PDT)-induced apoptosis of the HK-1 nasopharyngeal carcinoma (NPC) cells. HY-PDT was found to induce proteolytic cleavage of procaspase-9 and -3 in HK-1 cells. Apoptotic nuclei were observed at 6 h after PDT whereas B-cell leukemia/lymphoma-2-associated-X-protein (Bax) translocation and formation of Bax channel is responsible for the cell death. Increase in phosphorylation of p38 MAPKs and c-Jun N-terminal kinase 1/2 (JNK1/2) was detected at 15-30 min after HY-PDT. The appearance of phosphorylated form of p38 MAPKs and JNK1/2 was inhibited by the singlet oxygen scavenger l-histidine. HY-PDT-induced cell death was enhanced by the chemical inhibitors for p38 MAPKs (SB202190 and SB203580), but not by the JNKs inhibitor SP600125. Knockdown of the p38alpha and p38beta MAPK isoforms by small interfering RNA (siRNA) are more effective than the p38delta in enhancing PDT-induced cell death. Augmentation of apoptosis by p38alpha or p38beta knockdown is also correlated with the increased proteolytic cleavage of procaspase-9 after HY-PDT treatment. Our results suggested that HY-PDT activated p38 MAPKs through the production of singlet oxygen. Inhibition of p38 MAPKs with chemical inhibitors or siRNA enhances HY-PDT-induced apoptosis of the HK-1 NPC cells.

Epigenetic identification of ADAMTS18 as a novel 16q23.1 tumor suppressor frequently silenced in esophageal, nasopharyngeal and multiple other carcinomas

Tumor suppressor genes (TSGs) often locate at chromosomal regions with frequent deletions in tumors. Loss of 16q23 occurs frequently in multiple tumors, indicating the presence of critical TSGs at this locus, such as the well-studied WWOX. Herein, we found that ADAMTS18, located next to WWOX, was significantly downregulated in multiple carcinoma cell lines. No deletion of ADAMTS18 was detected with multiplex differential DNA-PCR or high-resolution 1-Mb array-based comparative genomic hybridization (CGH) analysis. Instead, methylation of the ADAMTS18 promoter CpG Island was frequently detected with methylation-specific PCR and bisulfite genome sequencing in multiple carcinoma cell lines and primary carcinomas, but not in any nontumor cell line and normal epithelial tissue. Both pharmacological and genetic demethylation dramatically induced the ADAMTS18 expression, indicating that CpG methylation directly contributes to the tumor-specific silencing of ADAMTS18. Ectopic ADAMTS18 expression led to significant inhibition of both anchorage-dependent and -independent growth of carcinoma cells lacking the expression. Thus, through functional epigenetics, we identified ADAMTS18 as a novel functional tumor suppressor, being frequently inactivated epigenetically in multiple carcinomas.

Apoptosis and expression of cytokines triggered by pyropheophorbide-a methyl ester-mediated photodynamic therapy in nasopharyngeal carcinoma cells

The photodynamic properties of pyropheophorbide-a methyl ester (MPPa), a semi-synthetic photosensitizer derived from chlorophyll a, were evaluated in a human nasopharyngeal carcinoma HONE-1 cell line. MPPa was non-toxic to the HONE-1. At the concentrations of 0.5-2μM, MPPa-mediated a drug dose-dependent photocytotoxicity in the HONE-1 cells. Confocal microscopy revealed a subcellular localization of MPPa in mitochondria and the Golgi apparatus. MPPa PDT-induced apoptosis was associated with the collapse of mitochondrial membrane potential, release of cytochrome c, the up-regulation of endoplasmic reticulum (ER) stress proteins (calnexin, Grp 94 and Grp78), and the activation of caspases-3 and -9. The photocytotoxicity was reduced by the corresponding specific caspase inhibitors. MPPa PDT-treated HONE-1 cells also up-regulated the gene expression of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) and beta-chemokines (MIP-1β, MPIF-1, and MPIF-2). These results suggest that the MPPa may be developed as a chlorophyll-based photosensitizer for the treatment of nasopharyngeal carcinoma.

Identification of a tumor suppressive critical region mapping to 3p14.2 in esophageal squamous cell carcinoma and studies of a candidate tumor suppressor gene, ADAMTS9

A gene critical to esophageal cancer has been identified. Functional studies using microcell-mediated chromosome transfer of intact and truncated donor chromosomes 3 into an esophageal cancer cell line and nude mouse tumorigenicity assays were used to identify a 1.61 Mb tumor suppressive critical region (CR) mapping to chromosome 3p14.2. This CR is bounded by D3S1600 and D3S1285 microsatellite markers. One candidate tumor suppressor gene, ADAMTS9, maps to this CR. Further studies showed normal expression levels of this gene in tumor-suppressed microcell hybrids, levels that were much higher than observed in the recipient cells. Complete loss or downregulation of ADAMTS9 gene expression was found in 15 out of 16 esophageal carcinoma cell lines. Promoter hypermethylation was detected in the cell lines that do not express this gene. Re-expression of ADAMTS9 was observed after demethylation drug treatment, confirming that hypermethylation is involved in gene downregulation. Downregulation of ADAMTS9 was also found in 43.5 and 47.6% of primary esophageal tumor tissues from Hong Kong and from the high-risk region of Henan, respectively. Thus, this study identifies and provides functional evidence for a CR associated with tumor suppression on 3p14.2 and provides the first evidence that ADAMTS9, mapping to this region, may contribute to esophageal cancer development.

Tumor suppressive role of a 2.4 Mb 9q33-q34 critical region and DEC1 in esophageal squamous cell carcinoma

The key genes involved in the development of esophageal squamous cell carcinoma (ESCC) remain to be elucidated. Previous studies indicate extensive genomic alterations occur on chromosome 9 in ESCC. Using a monochromosome transfer approach, this study provides functional evidence and narrows down the critical region (CR) responsible for chromosome 9 tumor suppressing activity to a 2.4 Mb region mapping to 9q33-q34 between markers D9S1798 and D9S61. Interestingly, a high prevalence of allelic loss in this CR is also observed in primary ESCC tumors by microsatellite typing. Allelic loss is found in 30/34 (88%) tumors and the loss of heterozygosity (LOH) frequency ranges from 67 to 86%. Absent to low expression of a 9q32 candidate tumor suppressor gene (TSG), DEC1 (deleted in esophageal cancer 1), is detected in four Asian ESCC cell lines. Stably expressing DEC1 transfectants provide functional evidence for inhibition of tumor growth in nude mice and DEC1 expression is decreased in tumor segregants arising after long-term selection in vivo. There is 74% LOH in the DEC1 region of ESCC primary tumors. This study provides the first functional evidence for the presence of critical tumor suppressive regions on 9q33-q34. DEC1 is a candidate TSG that may be involved in ESCC development.

Monochromosome transfer provides functional evidence for growth-suppressive genes on chromosome 14 in nasopharyngeal carcinoma

In many cancers, including nasopharyngeal carcinoma (NPC), extensive and multiple regions of allelic loss occur on chromosome 14. However, to date no functionally conclusive tumor suppressor genes have yet been identified on this chromosome. Through use of the monochromosome transfer technique, this study provides functional evidence for the importance of two discrete regions of chromosome 14. A newly established A9 mouse donor cell line containing an intact copy of chromosome 14 was used for transfer of this intact chromosome into the NPC HONE1 cell line. Twelve independently established microcell hybrids demonstrated uniform loss of specific chromosome 14 loci from both endogenous and exogenous alleles. By microsatellite typing and fluorescence in situ hybridization with BAC probes, the two critical regions were localized to 14q11.2-13.1 and 14q32.1. Selective elimination of these regions during hybrid selection was strongly associated with both hybrid survival and tumor growth in vivo. This functional evidence now narrows down the candidate areas for further studies and suggests that at least two hitherto unidentified growth-related genes localized on two critical regions of chromosome arm 14q play an important role in tumorigenesis.

Frequent loss of heterozygosity on multiple chromosomes in Chinese esophageal squamous cell carcinomas

Analysis of the loss of heterozygosity (LOH) detected by polymerase chain reaction techniques using 18 polymorphic markers localized to chromosomes 3p, 5, 17, and 18q in 40 Hong Kong Chinese esophageal squamous cell carcinoma (ESC) patients showed that multiple alterations on several chromosomes are involved in ESC development. The LOH rates detected for markers on chromosome 3 ranged from 44.0 to 85.7%, for chromosome 5 from 40.9 to 61.9%, for chromosome 17 from 40.0 to 100%, and for chromosome 18 from 38.9 to 58.3%. No significant association was observed between LOH and the clinical and histopathological parameters.

Microsatellite allelotyping of chinese nasopharyngeal carcinomas

BACKGROUND

Chinese nasopharyngeal carcinoma (NPC) specimens were analyzed by microsatellite allelotyping to evaluate their usefulness as biomarkers for cancer detection.

MATERIALS AND METHODS

A panel of eight microsatellite markers localized to chromosomes 3p, 6p, 9p, I1q and 14q were used to study 47 specimens.

RESULTS

A moderately low loss of heterozygosity (LOH) frequency (8% to 35%) was observed; 23 (49%) specimens showed LOH with at least one marker while microsatellite instability (MSI) was detected in 10 specimens (21%).

CONCLUSION

Poor survival was significantly associated with LOH detected by a chromosome 3 marker. Interestingly, tumors with multiple genetic alterations were significanty associated with earlier staging

A functional investigation of tumor suppressor gene activities in a nasopharyngeal carcinoma cell line HONE1 using a monochromosome transfer approach

Monochromosome transfers of selected chromosomes into a nasopharyngeal carcinoma (NPC) cell line were performed to determine if tumor suppressing activity for NPC mapped to chromosomes 9, 11, and 17. Current information from cytogenetic and molecular allelotyping studies indicate that these chromosomes may harbor potential tumor suppressor genes vital to NPC. The present results show the importance of CDKN2A on chromosome 9 in NPC development. There was no functional suppression of tumor development in nude mice with microcell hybrids harboring the newly transferred chromosome 9 containing an interstitial deletion at 9p21, whereas transfection of CDKN2A into the NPC HONE1 cells resulted in obvious growth suppression. Whereas intact chromosome 17 transfers into HONE1 cells showed no functional suppression of tumor formation, chromosome 11 was able to do so. Molecular analysis of chromosome 11 tumor segregants indicated that at least two tumor suppressive regions mapping to 11q13 and 11q22-23 may be critical for the development of NPC.

p53 inactivating mutations in chinese breast carcinomas

While previous reports on breast cancers indicate that Caucasian women have a low frequency of p53 mutations, higher frequencies of mutations are reported in some Japanese populations. There are few reports regarding p53 mutations in Chinese breast carcinomas. Using a previously established sensitive p53 yeast functional assay, we screened 23 Chinese breast carcinomas for mutations. The p53 was mutated in 5/23 (21.7%) specimens. Two of these mutations were detected in exon 5 and one was detected in each of exons 6, 7 and 8. All of these mutations have previously been shown to be mutated in Caucasian and Japanese breast cancers, but two have not previously been observed in Chinese breast cancers and one has also not been observed in Japanese.

Genomic instability and alterations in Apc, Mcc and Dcc in Hong Kong patients with colorectal carcinoma

Our aim was to reveal the significance of tumor-suppressor genes and genomic instability in 99 Hong Kong Chinese colorectal carcinoma (CRC) patients by PCR-LOH analysis and PCR-PTT assay. The frequencies of allelic loss of Apc, Mcc and Dcc and of APC truncation were 31.3% (15/48), 11.6% (5/43), 44.4% (20/45) and 46/93 (49.5%), respectively. The frequency of Apc LOH was similar to, the Mcc LOH was lower than, and the Dcc LOH was higher than that reported for Caucasians and Japanese. In Hong Kong CRC patients, the replication error-positive (RER(+)) phenotype occurred with a frequency of 10% (10/99), which was similar to other results using microsatellite markers where RER(+) frequencies ranged from 11% to 28%. The rates of genetic alteration in RER(+) tumors were lower in tumors harboring p53, Mcc and Dcc alterations; similar in Apc; and higher in Ki-ras tumors compared with RER(-) tumors, though these differences did not achieve statistical significance. None of the biomarkers examined were predictive of survival independently, but strong trends confirming earlier observations of associations between RER(+) phenotypes with proximal tumor location and poorly differentiated tumor status were noted. The RER(+) phenotype was correlated significantly to the less aggressive Duke's stage B and improved prognosis. Additionally, tumors with RER(+) phenotypes were positively correlated with young age and sex. Our results support the observation that a subset of younger male CRC patients in Hong Kong may develop CRC via the RER pathway and show differences in RER status and sex. A significantly higher percentage of older Hong Kong Chinese CRC patients had APC truncations. Int. J. Cancer (Pred. Oncol.) 84:404-409, 1999.

Genomic instability and alterations in Apc, Mcc and Dcc in Hong Kong patients with colorectal carcinoma

Our aim was to reveal the significance of tumor-suppressor genes and genomic instability in 99 Hong Kong Chinese colorectal carcinoma (CRC) patients by PCR-LOH analysis and PCR-PTT assay. The frequencies of allelic loss of Apc, Mcc and Dcc and of APC truncation were 31.3% (15/48), 11.6% (5/43), 44.4% (20/45) and 46/93 (49.5%), respectively. The frequency of Apc LOH was similar to, the Mcc LOH was lower than, and the Dcc LOH was higher than that reported for Caucasians and Japanese. In Hong Kong CRC patients, the replication error-positive (RER(+)) phenotype occurred with a frequency of 10% (10/99), which was similar to other results using microsatellite markers where RER(+) frequencies ranged from 11% to 28%. The rates of genetic alteration in RER(+) tumors were lower in tumors harboring p53, Mcc and Dcc alterations; similar in Apc; and higher in Ki-ras tumors compared with RER(-) tumors, though these differences did not achieve statistical significance. None of the biomarkers examined were predictive of survival independently, but strong trends confirming earlier observations of associations between RER(+) phenotypes with proximal tumor location and poorly differentiated tumor status were noted. The RER(+) phenotype was correlated significantly to the less aggressive Duke's stage B and improved prognosis. Additionally, tumors with RER(+) phenotypes were positively correlated with young age and sex. Our results support the observation that a subset of younger male CRC patients in Hong Kong may develop CRC via the RER pathway and show differences in RER status and sex. A significantly higher percentage of older Hong Kong Chinese CRC patients had APC truncations. Int. J. Cancer (Pred. Oncol.) 84:404-409, 1999.

L-myc genotypes in Hong Kong Chinese colorectal carcinoma patients

L-myc genotypes have been correlated with prognosis in different human tumors. Its role in colorectal carcinoma (CRC) is still unclear. This study aimed to assess the L-myc genotypes in 99 Hong Kong Chinese CRC patients by PCR-RFLP techniques. The results obtained were correlated with clinical, histological and pathological parameters and genetic alterations. The observed frequency of L-myc genotypes (LL:LS:SS) was 27:46:26. The ratio of S to L alleles was 0.51:0.49. Distribution of L-myc genotypes and alleles in Hong Kong Chinese CRC was similar to that of healthy Chinese and CRC patients of other ethnic origins. The homozygous SS genotype was significantly associated with Dukes' stages C versus B. Other parameters including sex, differentiation status and survival, and genetic alterations such as p53 and Ki-ras mutations and Dcc LOH had no significant association with L-myc SS genotype.

Comparative p53 mutational spectra in aerodigestive tract tumors in Hong Kong Chinese patients

The p53 mutations in colorectal, esophageal and lung carcinomas from Hong Kong were studied previously. The availability of mutation data for these cancers in one geographical region prompted investigations into special features of these p53 alterations. Mutations in codons 175, 176, 248 and 273 accounted for 35% of all mutations detected. A hot spot at codon 176 observed in esophageal carcinomas was not detected in any of the other aerodigestive tract tumors studied and appeared to be uniquely restricted to Chinese esophageal cancers. Other unique mutation sites, and a notably higher frequency of insertions and deletions in each of these cancers, were also detected in Chinese patients as compared to Caucasians.

Detection of p53 mutations in Hong Kong colorectal carcinomas by conventional PCR-SSCP analysis versus p53 yeast functional assays

BACKGROUND

Previous reports indicate that the p53 yeast functional assay is a highly sensitive method of detection of p53 mutations in clinical specimens. Our earlier report (1) showed a 35.4% p53 mutation frequency in Hong Kong colorectal carcinoma (CRC) patients, when conventional molecular screening techniques were utilized to assess the mutation rate in the hot spots in exons 5-8.

MATERIALS AND METHODS

The yeast functional assay was used to determine if the previous mutation frequency determined by PCR-SSCP techniques was under-estimated, and if so, to see if other hot spots for mutations explain this difference.

RESULTS

The p53 functional yeast assay results showed an increased mutation frequency. However, sequencing showed the mutations were confined to common hot spots for mutations in exons 6 and 7.

CONCLUSIONS

The mutation frequency in CRC patients observed with the yeast assay is higher than previously reported. Forty-five percent of 20 SSCP-negative specimens were positive by the yeast assay, which this study shows is superior for detection of p53 mutations directly in clinical specimens containing varying amounts of normal tissue contamination.

Ki-ras codon 12 point mutational activation in Hong Kong colorectal carcinoma patients

This study investigated the frequency and importance of Ki-ras codon 12 mutations in 99 Hong Kong Chinese colorectal carcinoma specimens by allele-specific oligonucleotide hybridization. The frequency of mutations detected was 30% and the most common mutation observed resulted in aspartic acid substitutions. Previous studies showed that specific Ki-ras mutations have been significantly associated with prognosis. Ki-ras codon 12 point mutational activation in CRC was significantly associated with the differentiation status of tumors in this study. Ethnic differences in the patterns of Ki-ras codon 12 point mutations were observed.

p53 inactivating mutations in Chinese nasopharyngeal carcinomas

Previously a low frequency of p53 mutations was detected in nasopharyngeal carcinoma (NPC) using molecular techniques to screen for mutations, yet immunohistochemical staining revealed a high frequency of p53 aberrant proteins. These findings might be attributed to the occurrence of p53 mutations outside the common hot spots and/or the inactivation of the protein through interactions with cellular or viral proteins. Using a previously established simple and sensitive p53 yeast functional assay, we blindly screened 25 nasopharyngeal biopsies for p53 mutations from exons 4 to 11. p53 was mutated in 27.3% of NPC specimens and in 0% of the nasopharyngeal biopsies from patients with non-malignant diseases. Two p53 mutations were detected in exon 7 and two were detected in exon 8. Interestingly, the exon 8 mutations observed in NPC lie in codons which appear to be hot spots for mutations in other head and neck cancers.

p53 intron 2 genotypes detected in normal specimens and lung carcinomas in Hong Kong

Previous studies suggest that the polymorphic p53 intron 2 displays a high frequency of mutations, occurring with different frequencies in tumor tissues versus peripheral blood of lung cancer patients as compared to healthy individuals. We evaluated the significance of these polymorphisms and mutations utilizing matched triple specimens from the lung tumor, normal lung tissue, and peripheral blood of cancer patients. Identical genotypes were observed in normal tissues and blood, while 4 mutations were observed in tumors. The A1 allelic frequency was increased in the adenocarcinoma tissues as compared to normal tissues. Two p53 exon 2 polymorphisms were detected, appearing with equal frequencies among cancer patients and healthy individuals. The p53 intron 2 polymorphic locus is a hot spot for mutations in Hong Kong lung cancer patients.

Functional evidence for a nasopharyngeal carcinoma tumor suppressor gene that maps at chromosome 3p21.3

Nasopharyngeal carcinoma is a malignancy that is prevalent among populations from Southeast Asia. Epidemiological studies indicate that genetic predisposition, Epstein-Barr virus, and environmental conditions may play a role in determining incidence. Molecular studies have implicated a tumor suppressor gene(s) on the short arm of chromosome 3. In this study we provide functional evidence, via monochromosome transfer, for a tumor suppressor gene(s) activity in chromosome 3p21.3.

p53 mutations detected in colorectal carcinoma patients in Hong Kong

A mutational spectrum for exons 5-8 of the p53 tumor suppressor gene in colorectal carcinomas in Hong Kong Chinese was established. Ninety-nine colorectal carcinomas from Hong Kong patients were analyzed for mutations in p53 gene by PCR-single-strand conformation polymorphism analysis and direct DNA sequencing. Thirty-five of the 99 tumors (35.4%) contained mutations. Point mutations accounted for 80% of all genetic changes and were predominantly base transitions at CpG dinucleotide sites, mutations that were also predominant in Caucasian carcinomas. The major hot spots at codons 175 and 248 of p53 in Caucasians are also hot spots in the Chinese gene. Identical mutations in codons 152 and 306 were detected in two independent tumors in the Chinese, which were reported only rarely in Caucasians. Moreover, a significantly higher frequency (20%) of deletion and insertion mutations was observed in Hong Kong colorectal cancer patients. Distinct genetic and/or environmental factors may contribute to these findings.

p16 tumor suppressor gene mutations in Chinese esophageal carcinomas in Hong Kong

The frequency and nature of genetic alterations in the p16 tumor suppressor gene in 25 esophageal squamous cell carcinoma specimens from Chinese patients were investigated by PCR-SSCP and DNA sequencing techniques. No gross deletions occurred in either exon 1 and 2 of the gene by PCR amplification. However, genetic changes were observed in three cases. These included a point mutation in codon 12 of exon 1 with a resulting Ala --> Thr amino acid substitution, a point mutation at base 91 in the non-coding region of exon 1, and a 1 base pair insertion in codon 116 of exon 2. The low mutation frequency of 12% is consistent with that of three previous studies involving Japanese and Caucasian patients (8, 16 and 21% frequency: Esteve et al., 1996, Igaki et al., 1995 and Zhou et al., 1994). p16 gene mutations do not appear to play a major role in esophageal carcinogenesis.

Analysis of L-myc and GSTM1 genotypes in Chinese non-small cell lung carcinoma patients

The genotypes of L-myc and GSTM1 genes were studied in normal lung tissues of 98 non-small cell lung carcinoma (NSCLC) patients from Hong Kong using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) techniques. Results showed a statistical difference in L-myc genotypes between Chinese and African Americans (P = 0.02). A significant deficit in heterozygotes resulting in the departure from Hardy-Weinberg equilibrium in lung cancer female patients was detected (0.01 < P < 0.02). There were significant differences in survival times in patients having L-L and S-S genotypes, with shorter survival times in the patients with L-L genotypes (0.01 < P < 0.05). Data on age, size of tumor, histological types, and lymph node metastasis showed no significant association with L-myc genotype. The survival time in the GSTM1-negative (null gene) group was significantly different from the GSTM1 positive group between 16 and 24 months after operation (0.01 < P < 0.05). There was no significant difference in the distribution of GSTM1 genotypes between Chinese and Caucasian Americans.

Tissue distribution of Epstein-Barr virus genotypes

The genome of naturally occurring Epstein-Barr virus contains either two or three copies of a 29-bp tandem repeat sequence in the first intron of the BZLF gene. These genotypes differ markedly in their distribution between blood and epithelial tissues, presumably because they have adapted to separate life cycles in these sites. The genotype prevalent in the blood also appears to be better able to transform B lymphocytes.

Chromosomal 11 alterations in non-small-cell lung carcinomas in Hong Kong

We examined 60 non-small-cell lung cancer (NSCLC) patients for evidence of genetic alterations on chromosome 11 with nine polymorphic markers by Southern blot and microsatellite marker analysis. These analyses detected genetic alterations at both the 11p and 11q arms. At the 11p15 Ha-ras locus, the loss of heterozygosity (LOH) occurred in three out of 11 (27.3%) of the informative cases; at the 11p11-q12 D11S149 locus, the LOH occurred in two out of nine (22.2%) of the informative cases; and at the 11q13 INT-2 locus, the LOH occurred in four out of 18 (22.2%) of the informative cases. Microsatellite markers in the 11q12-q13 region revealed genetic alterations for PYGM in eight out of 54 (14.8%) of the specimens studied and 10 out of 55 (18.2%) of the specimens for the INT-2 marker. The data suggest genetic alterations occur in some of the lung cancer patients in both the 11p and 11q regions.