Li Zhen Chen

A genome-wide association study of nasopharyngeal carcinoma identifies three new susceptibility loci

To identify genetic susceptibility loci for nasopharyngeal carcinoma (NPC), a genome-wide association study was performed using 464,328 autosomal SNPs in 1,583 NPC affected individuals (cases) and 1,894 controls of southern Chinese descent. The top 49 SNPs from the genome-wide association study were genotyped in 3,507 cases and 3,063 controls of southern Chinese descent from Guangdong and Guangxi. The seven supportive SNPs were further confirmed by transmission disequilibrium test analysis in 279 trios from Guangdong. We identified three new susceptibility loci, TNFRSF19 on 13q12 (rs9510787, Pcombined = 1.53 × 10−9, odds ratio (OR) = 1.20), MDS1-EVI1 on 3q26 (rs6774494, Pcombined = 1.34 × 10−8, OR = 0.84) and the CDKN2A-CDKN2B gene cluster on 9p21 (rs1412829, Pcombined = 4.84 × 10−7, OR = 0.78). Furthermore, we confirmed the role of HLA by revealing independent associations at rs2860580 (Pcombined = 4.88 × 10−67, OR = 0.58), rs2894207 (Pcombined = 3.42 × 10−33, OR = 0.61) and rs28421666 (Pcombined = 2.49 × 10−18, OR = 0.67). Our findings provide new insights into the pathogenesis of NPC by highlighting the involvement of pathways related to TNFRSF19 and MDS1-EVI1 in addition to HLA molecules.

Trends in incidence and mortality of nasopharyngeal carcinoma over a 20–25 year period (1978/1983–2002) in Sihui and Cangwu counties in southern China

BackgroundNasopharyngeal carcinoma (NPC) is a rare malignancy in most parts of the world but is common in southern China. A recent report from the Hong Kong Cancer Registry, a high-risk area for NPC in southern China, showed that incidence rate decreased by 29% for males and by 30% for females from 1980–1999, while mortality rate decreased by 43% for males and 50% for females. Changing environmental risk factors and improvements in diagnosis and treatment were speculated to be the major factors contributing to the downward trend of the incidence and mortality rates of NPC. To investigate the secular trends in different Cantonese populations with different socio-economic backgrounds and lifestyles, we report the incidences and mortality rates from two population-based cancer registries in Sihui and Cangwu counties from 1978–2002.MethodsIncidence and mortality rates were aggregated by 5-year age groups and 5 calendar years. To adjust for the effect of difference in age composition for different periods, the total and age-specific rates of NPC incidence and mortality rate were adjusted by direct standardization according to the World Standard Population (1960). The Estimated Annual Percentage Change (EAPC) was used as an estimate of the trend.ResultsThe incidence rate of NPC has remained stable during the recent two decades in Sihui and in females in Cangwu, with a slight increase observed in males in Cangwu from 17.81 to 19.76 per 100,000. The incidence rate in Sihui is 1.4–2.0 times higher during the corresponding years than in Cangwu, even though the residents of both areas are of Cantonese ethnicity. A progressive decline in mortality rate was observed in females only in Sihui, with an average reduction of 6.3% (p = 0.016) per five-year period.ConclusionTo summarize, there is great potential to work in the area of NPC prevention and treatment in southern China to decrease NPC risk and improve survival risk rates in order to reduce M:I ratios. Future efforts on effective prevention, early detection and treatment strategies were also discussed in this paper. Furthermore, the data quality and completeness also need to be improved.

MiR-138 suppressed nasopharyngeal carcinoma growth and tumorigenesis by targeting the CCND1 oncogene

The microRNA miR-138 is dysregulated in several human cancers, but the underlying mechanism remains largely unknown. Here, we report that miR-138 is commonly underexpressed in nasopharyngeal carcinoma (NPC) specimens and NPC cell lines. The ectopic expression of miR-138 dramatically suppressed cell proliferation and colony formation in vitro and inhibited tumorigenesis in vivo. Moreover, we identified the cyclin D1 (CCND1) gene as a novel direct target of miR-138. In consistent with the knocked-down expression of CCND1, overexpression of miR-138 inhibited cell growth and cell cycle progression in NPC cells. Furthermore, CCND1 was widely upregulated in NPC tumors, and its mRNA levels were inversely correlated with miR-138 expression. Taken together, our findings suggest that miR-138 might be a tumor suppressor in NPC, which is exerted partially by inhibiting CCND1 expression. The identification of functional miR-138 in NPC and its direct link to CCND1 might provide good candidates for developing diagnostic markers and therapeutic applications for NPC.

Traditional Cantonese diet and nasopharyngeal carcinoma risk: A large-scale case-control study in Guangdong, China

BackgroundNasopharyngeal carcinoma (NPC) is rare in most parts of the world but is a common malignancy in southern China, especially in Guangdong. Dietary habit is regarded as an important modifier of NPC risk in several endemic areas and may partially explain the geographic distribution of NPC incidence. In China, rapid economic development during the past few decades has changed the predominant lifestyle and dietary habits of the Chinese considerably, requiring a reassessment of diet and its potential influence on NPC risk in this NPC-endemic area.MethodsTo evaluate the association between dietary factors and NPC risk in Guangdong, China, a large-scale, hospital-based case-control study was conducted. 1387 eligible cases and 1459 frequency matched controls were recruited. Odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were estimated using a logistic regression model, adjusting for age, sex, education, dialect, and habitation household type.ResultsObservations made include the following: 1) consumption of canton-style salted fish, preserved vegetables and preserved/cured meat were significantly associated with increased risk of NPC, with enhanced odds ratios (OR) of 2.45 (95% CI: 2.03-2.94), 3.17(95% CI: 2.68-3.77) and 2.09 (95% CI: 1.22-3.60) respectively in the highest intake frequency stratum during childhood; 2) consumption of fresh fruit was associated with reduced risk with a dose-dependent relationship (p = 0.001); and 3) consumption of Canton-style herbal tea and herbal slow-cooked soup was associated with decreased risk, with ORs of 0.84 (95% CI: 0.68-1.03) and 0.58 (95% CI: 0.47-0.72) respectively in the highest intake frequency stratum. In multivariate analyses, these associations remained significant.ConclusionsIt can be inferred that previously established dietary risk factors in the Cantonese population are still stable and have contributed to the incidence of NPC.

Direct Sequencing and Characterization of a Clinical Isolate of Epstein-Barr Virus from Nasopharyngeal Carcinoma Tissue by Using Next-Generation Sequencing Technology

ABSTRACT Epstein-Barr virus (EBV)-encoded molecules have been detected in the tumor tissues of several cancers, including nasopharyngeal carcinoma (NPC), suggesting that EBV plays an important role in tumorigenesis. However, the nature of EBV with respect to genome width in vivo and whether EBV undergoes clonal expansion in the tumor tissues are still poorly understood. In this study, next-generation sequencing (NGS) was used to sequence DNA extracted directly from the tumor tissue of a patient with NPC. Apart from the human sequences, a clinically isolated EBV genome 164.7 kb in size was successfully assembled and named GD2 (GenBank accession number HQ020558). Sequence and phylogenetic analyses showed that GD2 was closely related to GD1, a previously assembled variant derived from a patient with NPC. GD2 contains the most prevalent EBV variants reported in Cantonese patients with NPC, suggesting that it might be the prevalent strain in this population. Furthermore, GD2 could be grouped into a single subtype according to common classification criteria and contains only 6 heterozygous point mutations, suggesting the monoclonal expansion of GD2 in NPC. This study represents the first genome-wide analysis of a clinical isolate of EBV directly extracted from NPC tissue. Our study reveals that NGS allows the characterization of genome-wide variations of EBV in clinical tumors and provides evidence of monoclonal expansion of EBV in vivo. The pipeline could also be applied to the study of other pathogen-related malignancies. With additional NGS studies of NPC, it might be possible to uncover the potential causative EBV variant involved in NPC.

A large cohort study reveals the association of elevated peripheral blood lymphocyte-to-monocyte ratio with favorable prognosis in nasopharyngeal carcinoma.

Background Nasopharyngeal carcinoma (NPC) is an endemic neoplasm in southern China. Although NPC sufferers are sensitive to radiotherapy, 20–30% of patients finally progress with recurrence and metastases. Elevated lymphocyte-to-monocyte ratio (LMR) has been reported to be associated with favorable prognosis in some hematology malignancies, but has not been studied in NPC. The aim of this study was to evaluate whether LMR could predict the prognosis of NPC patients. Methods A retrospective cohort of 1,547 non-metastatic NPC patients was recruited between January 2005 and June 2008. The counts for peripheral lymphocyte and monocyte were retrieved, and the LMR was calculated. Receiver operating characteristic curve analysis, univariate and multivariate COX proportional hazards analyses were applied to evaluate the associations of LMR with overall survival (OS), disease-free survival (DFS), distant metastasis-free survival (DMFS) and loco-regional recurrence-free survival (LRRFS), respectively. Results Univariate analysis revealed that higher LMR level (≥5.220) was significantly associated with superior OS, DFS and DMFS (P values <0.001). The higher lymphocyte count (≥2.145×109/L) was significantly associated with better OS (P = 0.002) and DMFS (P = 0.031), respectively, while the lower monocyte count (<0.475×109/L) was associated with better OS (P = 0.012), DFS (P = 0.011) and DMFS (P = 0.003), respectively. Multivariate Cox proportional hazard analysis showed that higher LMR level was a significantly independent predictor for superior OS (hazard ratio or HR  = 0.558, 95% confidence interval or 95% CI  = 0.417–0.748; P<0.001), DFS (HR  = 0.669, 95% CI  = 0.535–0.838; P<0.001) and DMFS (HR = 0.543, 95% CI  = 0.403–0.732; P<0.001), respectively. The advanced T and N stages were also independent indicators for worse OS, DFS, and DMFS, except that T stage showed borderline statistical significance for DFS (P = 0.053) and DMFS (P = 0.080). Conclusions The elevated pretreatment peripheral LMR level was a significant favorable factor for NPC prognosis and this easily accessed variable may serve as a potent marker to predict the outcomes of NPC patients.

Sequence Variants in Toll-Like Receptor 10 Are Associated with Nasopharyngeal Carcinoma Risk

Nasopharyngeal carcinoma (NPC) is a common malignancy in southern China and Southeast Asia. Genetic susceptibility is a major factor in determining the individual risk of NPC in these areas. To test the association between NPC and variants in Toll-like receptor 10 (TLR10), we conducted a hospital-based case-control study in a Cantonese-speaking population in Guangdong province. Seven single nucleotide polymorphisms in TLR10, selected with a tagging algorithm, were genotyped. When assessing each unique haplotype compared with the most common haplotype, “GAGTGAA,” with the expectation-maximization algorithm in Haplo.stats, the risk of developing NPC was significantly elevated among men who carried the haplotype “GCGTGGC” (P = 0.005). After adjusting for age, gender, and VCA-IgA antibody titers, this association was more significant (P = 0.0007). To further assess the overall differences of haplotype frequency profiles between cases and healthy controls, the global score test, considering all haplotypes and adjusting for age, gender, and VCA-IgA antibody titers, gave a haplo score of 27.52 with P = 0.002. The haplotype specific odds ratio was 2.66 (confidence interval, 1.34-3.82) for GCGTGGC. We concluded that in this Cantonese population–based study, haplotype GCGTGGC with frequency of 11.4% in TLR10 was found to be associated with NPC and this association was statistically significant after adjusting for age, gender, and VCA-IgA antibody titers. It is possible that this is not a causal haplotype for NPC; rather, it is in strong linkage disequilibrium with a causal single nucleotide polymorphism in close proximity. (Cancer Epidemiol Biomarkers Prev 2006;15(5):862–6)

Effect of family history of cancers and environmental factors on risk of nasopharyngeal carcinoma in Guangdong, China.

BACKGROUND Family history of nasopharyngeal carcinoma (NPC) is an established risk factor for this cancer, but the contributions of family history of other types of cancer and its interaction with environmental factors have not been well characterized. METHODS A total of 1845 incident cases of NPC and 2275 matched controls from Guangdong, China were included in this study. Odds ratios (OR) and 95% confidence intervals (CI) were calculated from logistic regression models adjusted for smoking, consumption of alcohol, salted fish consumption, and demographic factors. RESULTS A significant association between the risk of NPC and family history of any cancers in first degree relatives was observed, and higher number of affected family member was related to a higher risk (P(trend)<0.01). Family history of NPC was the strongest predictor for NPC (OR: 3.35, 95% CI: 2.46-4.55 for all first degree relatives). The risk of NPC was also positively associated with history of head and neck cancer among parents and lung and breast cancers among siblings. The combination of family history of cancer, especially NPC, and the consumption of salt-preserved fish significantly increased the risk for NPC. CONCLUSIONS These results confirm that the risk for NPC increases with family history of NPC and suggest that lung and breast cancer contribute to risk for NPC. A possible interaction between family history of cancer, especially NPC, and consumption of salt-preserved fish in the development of NPC was also identified.

A Case–control and a family-based association study revealing an association between CYP2E1 polymorphisms and nasopharyngeal carcinoma risk in Cantonese

Nasopharyngeal carcinoma (NPC) is rare in most parts of the world but is more prevalent in Southern China, especially in Guangdong. The cytochrome P450 2E1 (CYP2E1) has been recognized as one of the critically important enzymes involved in oxidizing carcinogens and is probably to be associated with NPC carcinogenesis. To systematically investigate the association between genetic variants in CYP2E1 and NPC risk in Cantonese, two independent studies, a family-based association study and a case-control study, were conducted using the haplotype-tagging single-nucleotide polymorphism approach. A total of 2499 individuals from 546 nuclear families were initially genotyped for the family-based association study. Single-nucleotide polymorphisms (SNPs) rs9418990, rs915908, rs8192780, rs1536826, rs3827688 and one haplotype h2 (CGTGTTAA) were revealed to be significantly associated with the NPC phenotype (P = 0.045-0.003 and P = 0.003, respectively). To follow up the initial study, a case-control study including 755 cases and 755 controls was conducted. Similar results were observed in the case-control study in individuals <46 years of age and had a history of cigarette smoking, with odds ratios (ORs) of specific genotypes ranging from 1.88 to 2.99 corresponding to SNP rs9418990, rs3813865, rs915906, rs2249695, rs8192780, rs1536826, rs3827688 and of haplotypes h2 with OR = 1.65 (P = 0.026), h5 (CCCGTTAA) with OR = 2.58 (P = 0.007). The values of false-positive report probability were <0.015 for six SNPs, suggesting that the reported associations are less probably to be false. This study provides robust evidence for associations between genetic variants of CYP2E1 and NPC risk.

Comprehensive pathway-based association study of DNA repair gene variants and the risk of nasopharyngeal carcinoma.

DNA repair plays a central role in protecting against environmental carcinogenesis, and genetic variants of DNA repair genes have been reported to be associated with several human malignancies. To assess whether DNA gene variants were associated with nasopharyngeal carcinoma (NPC) risk, a candidate gene association study was conducted among the Cantonese population within the Guangdong Province, China, the ethnic group with the highest risk for NPC. A 2-stage study design was utilized. In the discovery stage, 676 tagging SNPs covering 88 DNA repair genes were genotyped in a matched case-control study (cases/controls = 755/755). Eleven SNPs with P(trend) < 0.01 were identified. Seven of these SNPs were located within 3 genes, RAD51L1, BRCA2, and TP53BP1. In the validation stage, these 11 SNPs were genotyped in a separate Cantonese population (cases/controls = 1,568/1,297). Two of the SNPs (rs927220 and rs11158728), both in RAD51L1, remained strongly associated with NPC. The SNP rs927220 had a significant P(combined) of 5.55 × 10(-5), with OR = 1.20 (95% CI = 1.10-1.30), Bonferroni corrected P = 0.0381. The other SNP (rs11158728), which is in strong linkage disequilibrium with rs927220 (r(2) = 0.7), had a significant P(combined) of 2.0 × 10(-4), Bonferroni corrected P = 0.1372. Gene-environment interaction analysis suggested that the exposures of salted fish consumption and cigarette smoking had potential interactions with DNA repair gene variations, but need to be further investigated. Our findings support the notion that DNA repair genes, in particular RAD51L1, play a role in NPC etiology and development.