Review on novel toxicological effects and personalized health hazard in workers exposed to low doses of benzene.

Several recent reports indicate health hazards for workers with below occupational limit exposure to benzene (BZ). Our updated review indicates that such low exposures induced traditional as well as novel toxicity/genotoxicity, e.g., increased mitochondria copy numbers, prolongation of telomeres, impairment of DNA damage repair response (DDRR), perturbations of expression in non-coding RNAs, and epigenetic changes. These abnormalities were associated with alterations of gene expression and cellular signaling pathways which affected hematopoietic cell development, expression of apoptosis, autophagy, etc. The overarching mechanisms for induction of health risk are impaired DDRR, inhibition of tumor suppressor genes, and changes of MDM2-p53 axis activities that contribute to perturbed control for cancer pathways. Evaluation of the unusual dose-responses to BZ exposure indicates cellular over-compensation and reprogramming to overcome toxicity and to promote survival. However, these abnormal mechanisms also promote the induction of leukemia. Further investigations indicate that the current exposure limits for workers to BZ are unacceptable. Based on these studies, the new exposure limits should be less than 0.07 ppm rather than the current 1 ppm. This review also emphasizes the need to conduct appropriate bioassays, and to provide more reliable decisions on health hazards as well as on exposure limits for workers. In addition, it is important to use scientific data to provide significantly improved risk assessment, i.e., shifting from a population- to an individual-based risk assessment.

Lymphocyte-based challenge DNA-repair assays for personalized health risk assessment.

Combinations of genetic and environmental factors are responsible for the development of many human diseases, such as cancer, as demonstrated using various biomarkers. Within this scenario, DNA repair holds a gate-keeper position which determines outcomes after appearance of DNA damage and, therefore, adverse cellular consequences, e.g., initiation of carcinogenesis. DNA repair deficiency and some of the subsequent events can be validated from studies using live cells from cancer patients. However, these deficiencies/events are difficult to demonstrate in live cells from normal individuals because individual variations in DNA repair capacities (DRC) are too low to be measured easily. Such lack of information has been hindering progress in developing personalized disease prevention and intervention protocols, especially among exposed populations. However, using a variety of challenge assays as biomarkers, variations in individual's DRC can be amplified in live cells and be determined. Furthermore, evidence indicates that DRC are not only inherited but can also be modified by environmental factors (e.g., nutritional status and exposure to genotoxic substances). Using these challenge assays, e.g., in live lymphocytes, individual's DRC can be holistically and functionally determined as well as quantitated. With the more precise information, assessment of health risk can be better determined on an individual rather than on a population basis. This review provides a succinct summary on the development and application of recent challenge assays in lymphocytes which can provide measurements of individuals' DRC, and on the latest data for more precise disease prevention and intervention.

Occupational Health Risk Assessment of Benzene, Toluene, and Xylene in Shanghai.

OBJECTIVE: This study was designed to conduct a retrospective and systematic occupational health risk assessment (OHRA) of enterprises that used benzene, toluene, and xylene (BTX) in Shanghai, China. METHODS: All data for the study were obtained from 1,705 occupational health examination and evaluation reports from 2013 to 2017, and a semiquantitative model following Chinese OHRA guidelines (GBZ/T 298-2017) was applied for the assessment. RESULTS: The selected enterprises using BTX were mainly involved in manufacturing of products. Using the exposure level method, health risk levels associated with exposure to BTX were classified as medium, negligible, or low. However, the risk levels associated with benzene and toluene were significantly different according to job types, with gluers and inkers exhibiting greater health risks. For the same job type, the health risk levels assessed using the comprehensive index method were higher than those using the exposure level method. CONCLUSION: Our OHRA reveals that workers who are exposed to BTX still face excessive health risk. Additionally, the risk level varied depending on job categories and exposure to specific chemicals. Therefore, additional control measures recommended by OHRA guidelines are essential to reduce worker exposure levels.

Changes in miR-222 expression, DNA repair capacity, and MDM2-p53 axis in association with low-dose benzene genotoxicity and hematotoxicity.

Mechanisms for hematotoxicity and health effects from exposure to low doses of benzene (BZ) remain to be identified. To address the information gap, our investigation was focused onto using appropriate populations and cell cultures to investigate novel BZ-induced effects such as disruption of DNA repair capacity (DRC). From our study, abnormal miRNAs were identified and validated using lymphocytes from 56 BZ-poisoned workers and 53 controls. In addition, 173 current BZ-exposed workers and 58 controls were investigated for key miRNA expression using RT-PCR and for cellular DRC using a challenge assay. Subsequently, the observed activities in lymphocytes were verified using human HL-60 (p53 null) and TK6 (p53 wild-type) cells via 1,4-benzoquinone (1,4-BQ) treatment and miR-222 interferences. The targeting of MDM2 by miR-222 was validated using a luciferase reporter. Our results indicate induction of genotoxicity in lymphocytes from workers with low exposure doses to BZ. In addition, miR-222 expression was up-regulated among both BZ-poisoned and BZ-exposed workers together with inverse association with DRC. Our in vitro validation studies using both cell lines indicate that 1,4-BQ exposure increased expression of miR-222 and Comet tail length but decreased DRC. Loss of miR-222 reduced DNA damage, but induced S-phase arrest and apoptosis. However, silencing of MDM2 failed to activate p53 in TK6 cells. In conclusion, our in vivo observations were confirmed by in vitro studies showing that BZ/1,4-BQ exposures caused genotoxicity and high expression of miR-222 which obstructed expression of the MDM2-p53 axis that led to failed activation of p53, abnormal DRC and serious biological consequences.

Associations between functional polychlorinated biphenyls in adipose tissues and prognostic biomarkers of breast cancer patients.

BACKGROUND: Exposure to polychlorinated biphenyls (PCBs) has been shown to influence expression of some biomarkers that are predictive/prognostic for breast cancer. Therefore, our study was conducted to further investigating associations of different functional PCBs in adipose tissue with breast cancer prognostic biomarkers. METHODS: Two hundred and five breast cancer patients were recruited in Shantou, China. Breast adipose tissues were collected during their resection surgery and levels of 7 PCB congeners were analyzed by gas chromatography-mass spectrometry (GC-MS). The PCB congeners were divided into 4 groups according to structure-activity. Socio-demographic, clinical and pathological information were obtained from questionnaire and digital medical records. Odds ratios (ORs) for associations between prognostic biomarkers and PCB levels (tertile 3 [T3], tertile 2 [T2] vs. tertile 1) were estimated from logistic regression models. RESULTS: Most PCB congeners were detectable, with a highest level (22.06 ng/g lipid) of PCB153. As for estrogenic PCBs, increased PCB52 exposure was positively associated with PR expression (ORT2 = 2.36, Ptrend = 0.054), but higher PCB101 level was negatively associated with HER-2 (ORT3 = 0.24, Ptrend = 0.029) and tumor size (OR = 0.43). Limited dioxin-like PCB138 exposure was positively associated with ER (ORT2 = 3.23, ORT3 = 3.77, Ptrend = 0.047) but negatively with Top-IIα expression (ORT2 = 0.35, ORT3 = 0.28, Ptrend = 0.080). Higher PCB153 (CYP inducer) level was negatively associated with ER (ORT2 = 0.32, ORT3 = 0.19, Ptrend = 0.038) but positively with Ki-67 expression (ORT2 = 1.43, ORT3 = 3.60, Ptrend = 0.055). Higher neurotoxic PCB28 was positively associated with HER-2 (ORT3 = 5.43, Ptrend = 0.006) and tumor size (OR = 2.37). Moreover, total PCBs exposure was positively associated with VEGF-C (ORT2 = 76.91, ORT3 = 97.96, Ptrend = 0.041) and tumor metastasis (OR = 2.25). CONCLUSIONS: Different functional PCB congeners have different associations (both positive and negative) with breast cancer prognostic biomarkers, as well as tumor classification stage. Therefore, the development and aggressiveness of breast cancer may depend upon exposure to specific structure-activity of PCBs.

Effects of Micronucleus Frequencies and Mitochondrial DNA Copy Numbers among Benzene-Exposed Workers in China.

To provide a more comprehensive understanding of genotoxic effects from benzene exposure, its effects on induction of mitochondrial DNA copy number (MtDNAcn) and of micronucleus (MN) were investigated using peripheral blood from workers in China. Changes in mtDNAcn and MN were determined using quantitative real-time polymerase chain reaction (PCR) and cytokinesis-block micronucleus assays (CBMN), respectively, in 58 control and 174 benzene-exposed workers in Shanghai, China. Among the exposed workers, relative mtDNAcn increased and then decreased with increasing doses of benzene exposure. Significant and dose-dependent increase in MN frequencies were observed among the different exposure groups. In addition, the relative mtDNAcn were significantly associated with the MN frequencies in the low-level exposure group (P = 0.046), but not in the high dose groups. Therefore, the mechanisms for induction of MtDNAcn and MN by benzene may be similar from exposure to low doses but different from high doses. Similar increase of MN frequencies and MtDNAcn may be due to oxidative stress induced by benzene at low concentrations, while higher concentrations may start to initiate the cell death pathway. The pathway may be associated with excessive MtDNAcn which can initiate apoptosis while MN can continue to be induced. However, the differential mechanisms need to be investigated because they may represent different levels of risk for different health consequences. On the other hand, our data indicate that induction of MtDNAcn may be a sensitive genotoxic biomarker for workers with exposure to low dose of benzene. Environ. Mol. Mutagen. 61:355-360, 2020. © 2020 Wiley Periodicals, Inc.

Public health issues from crude-oil production in the Ecuadorian Amazon territories.

Crude oil production (COP) is a high-pollution industry but the vast Amazon rainforest has been an active COP zone for South America. Although COP has been associated with a variety of health effects among workers around the world, such effects have not been adequately investigated in the Amazon region, especially at the community level. Therefore, this review was conducted to provide a report about COP in the Amazon of Ecuador and about its association with health status of indigenous human populations. Some epidemiological surveys in the Amazonian Territories indicate that COP has been associated with health problems in the surrounding populations, e.g. cancers in the stomach, rectum, skin, soft tissue, kidney and cervix in adults, and leukemia in children. In addition, some biomarkers and mechanistic studies show exposure effects. However, due to limitations from these studies, contradictory associations have been reported. Our review indicates that COP in the Amazonian territories of northern Ecuador was characterised by contamination which could have affected the indigenous and non-indigenous populations. However, there have not been dedicated investigations to provide relationships between the contamination and the subsequent exposure-health effects. Since indigenous populations have different lifestyle and cultures from regular city dwellers, systematic studies on their potential health hazards need to be conducted. Due to the remote locations and sparse populations, these new studies may involve the use of novel and genomic-based biomarkers as well as using high technology in the remote regions.

Exposure to perfluorooctane sulfonate based on circadian rhythm changes the fecundity and expression of certain genes on the hypothalamic-pituitary-gonadal-liver axis of female zebrafish.

Exposure of a variety of experimental animals to perfluorooctane sulfonate (PFOS) has shown that it is a potent endocrine-disrupting chemical. However, its interaction with the circadian rhythm on responses along the hypothalamic - pituitary - gonadal - liver (HPGL) axis should be of significant value but has not been adequately investigated. In present study, the effects of PFOS on fecundity, levels of estradiol (E2) and expression of certain genes on the HPGL axis at two time points (8:00 AM and 7:00 PM) were compared after female zebrafish were exposed to 0, 2, 20 and 200 µg/L PFOS for 21 days. In brain, expressions of gonadotropin-releasing hormone (GnRH), gonadotropin-releasing hormone receptor (GnRHr), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were significantly different after the exposure when sampled at 8:00 AM and at 7:00 PM (P < .05). In liver, significant down-regulation of vitellogenin1 (VTG1) and estrogenic receptor α (ERα) were observed at 7:00 PM compared with 8:00 AM (P < .05). In ovary, the level of CYP19 was significantly different at the two time points (P < .05). The increase of E2 after exposure to 20 µg/L PFOS at 8:00 AM caused compensatory down-regulation of GnRHr and up-regulation of VTG1 and ERα, but not at 7:00 PM. Profiles of concentrations of E2 and several gene expressions alongside the HPGL axis were different between two times points. The change of E2 and gene expressions were more perturbed by PFOS at 8:00 AM than at 7:00 PM with circadian rhythm.

Inherent and toxicant-provoked reduction in DNA repair capacity: A key mechanism for personalized risk assessment, cancer prevention and intervention, and response to therapy.

Genomic investigations reveal novel evidence which indicates that genetic predisposition and inherent drug response are key factors for development of cancer and for poor response to therapy. However, mechanisms for these outcomes and interactions with environmental factors have not been well-characterized. Therefore, cancer risk, prevention, intervention and prognosis determinations have still mainly been based on population, rather than on individualized, evaluations. The objective of this review was to demonstrate that a key mechanism which contributes to the determination is inherent and/or toxicant-provoked reduction in DNA repair capacity. In addition, functional and quantitative determination of DNA repair capacity on an individual basis would dramatically change the evaluation and management of health problems from a population to a personalized basis. In this review, justifications for the scenario were delineated. Topics to be presented include assays for detection of functional DNA repair deficiency, mechanisms for DNA repair defects, toxicant-perturbed DNA repair capacity, epigenetic mechanisms (methylation and miRNA expression) for alteration of DNA repair function, and bioinformatics approach to analyze large amount of genomic data. Information from these topics has recently been and will be used for better understanding of cancer causation and of response to therapeutic interventions. Consequently, innovative genomic- and mechanism-based evidence can be increasingly used to develop more precise cancer risk assessment, and target-specific and personalized medicine.

Attitudes towards acceptance of an innovative home-based and remote sensing rehabilitation protocol among cardiovascular patients in Shantou, China.

BACKGROUND: Cardiac rehabilitation (CR) protocols have diversified to include home-based cardiac tele-rehabilitation (HBCTR) as an alternative to hospital-based or center-based CR. To adopt the use of home-based cardiac tele-rehabilitation, it is necessary to assess cardiac patients' attitudes towards acceptance of such e-health technology, especially in China where knowledge of such technology is deficient. METHODS: Interviews were conducted in the First Affiliated Hospital of Shantou University Medical College, Shantou, China. After percutaneous coronary interventional (PCI) surgery, patients completed the survey. RESULTS: Among the 150 patients, only 13% had ever heard of HBCTR. After an introduction of our HBCTR program, 60% of patients were willing to participate in the program. From our multivariate analysis of questionnaire data, age (OR: 0.92, 95% CI: 0.86-0.98; P = 0.007), average family monthly income (OR: 0.13, 95% CI: 0.05-0.34; P < 0.001), education level (OR: 0.24, 95% CI: 0.10-0.59; P = 0.002) and physical exercise time (OR: 0.19, 95% CI: 0.06-0.56; P = 0.003) were independent predictors for acceptance of HBCTR. From the reasons for participation, patients selected: enhanced safety and independence (28.3%), ability to self-monitor physical conditions daily (25.4%), and having automatic and emergency alert (23.1%). Reasons for refusal were: too cumbersome operation (34.3%) and unnecessary protocol (19.4%). CONCLUSIONS: Most patients lacked knowledge about HBCTR but volunteered to participate after they have learned about the program. Several personal and life-style factors influenced their acceptance of the program. These indicate that both improvement of technology and better understanding of the program will enhance active participation.

Effect of polymorphic metabolizing genes on micronucleus frequencies among benzene-exposed shoe workers in China.

It is well-known that metabolism of benzene is required for the induction of toxicity and consequent health problems. Therefore, genetic variation in benzene (BZ) metabolism genes can influence health outcomes. However, large population studies are needed to provide more evidence for such relationship. We have conducted a large population investigation (385 BZ-exposed shoe workers and 197 matched healthy controls) on the association between inheritance of certain BZ metabolizing genes and the expression of micronuclei (MN). The latter was based on the cytokinesis-blocked MN assay. We analyzed the polymorphisms of GSTM1, GSTT1, GSTP1 (rs1695), CYP2E1 (rs3813867), CYP2E1 (rs2031920), CYP2E1 (rs6413432), mEH exon 3 (rs1051740), mEH exon 4 (rs2234922). Univariate Poisson regression analysis demonstrated that the BZ-exposed workers had significantly increased MN frequency compared with the controls (FR=1.84, 95% CI: 1.56-2.18; P<0.001), and showed a cumulative exposure dose-response relationship. The CYP2E1 rs3813867 mutant allele (CC+GC) (FR 1.15, 95% CI 1.02-1.29; P=0.020) and rs2031920 variant allele (CT+TT) (FR=1.23, 95% CI: 1.09-1.37, P<0.01) was associated with higher MN frequency significantly compared with the wild genotype separately. Furthermore, the MN frequency in rs2031920 variant allele (CT+TT) (FR=1.17, 95% CI: 1.04-1.31, P<0.01) was also higher than the wild genotype when the age, gender and cumulative exposure dose was adjusted in Poisson regression. In addition, the CYP2E1, however, GSTM1null, GSTT1null, GSTP1 rs1695, rs6413432, rs1051740 and rs2234922 polymorphisms showed no association with MN frequency. Our results indicate that two promoter polymorphisms in the CYP2E1 gene, especially the rs2031920 variant allele, were involved with the BZ-induction of MN and may contribute to risk of cancer among exposed workers.

Mortality characteristics and prediction of female breast cancer in China from 1991 to 2011.

AIMS: To analyze time-dependent changes in female breast cancer (BC) mortality in China, forecast the trend in the ensuing 5 years, and provide recommendations for prevention and management. MATERIALS AND METHODS: Mortality data of breast cancer in China from 1991 to 2011 was used to describe characteristics and distribution, such as the changes of the standardized mortality rate, urban-rural differences and age differences. Trend-surface analysis was used to study the geographical distribution of mortality. In addition, curve estimation, time series modeling, Gray modeling (GM) and joinpoint regression were performed to estimate and predict future trends. RESULTS: In China, the mortality rate of breast cancer has increased yearly since 1991. In addition, our data predicted that the trend will continue to increase in the ensuing 5 years. Rates in urban areas are higher than those in rural areas. Over the past decade, all peak ages for death by breast cancer have been delayed, with the first death peak occurring at 55 to 65 years of age in urban and rural areas. Geographical analysis indicated that mortality rates increased from Southwest to Northeast and from West to East. CONCLUSIONS: The standardized mortality rate of breast cancer in China is rising and the upward trend is predicted to continue for the next 5 years. Since this can cause an enormous health impact in China, much better prevention and management of breast cancer is needed. Consequently, disease control centers in China should place more focus on the northeastern, eastern and southeastern parts of China for breast cancer prevention and management, and the key population should be among women between ages 55 to 65, especially those in urban communities.

Evidence for exposure-induced DNA repair abnormality is indicative of health and genetic risk.

A recent focus has been targeted toward the development of functional biomarkers that can be used to predict disease more reliably. One such biomarker is the challenge assay for DNA repair deficiency. Briefly, the assay involves challenging lymphocytes in culture to a DNA damaging agent in vitro and determining the repair outcome in chromosome aberrations and/or DNA strand breaks. The aim is to show that individuals who have chronic exposure to toxic substances will develop exposure-induced DNA repair deficiencies. Many studies around the world have shown that the assay detects DNA repair deficiency in environmentally/occupationally exposed populations and with significant exposure dose-response relationship. The prediction of health risk was also validated. In addition, exposure-induced repair deficiency which was apparently passed through the germ cells had caused genetic consequences in a 3-generation population. The assay is simple to conduct and is more sensitive than some traditional biomarker assays. Together with the functional significance of the assay, the challenge assay can be used with confidence in population studies for health risk assessment.

XRCC1 codon 399Gln polymorphism is associated with radiotherapy-induced acute dermatitis and mucositis in nasopharyngeal carcinoma patients.

BACKGROUND: To evaluate the association between single nucleotide polymorphisms (SNPs) at the 194 and 399 codons of XRCC1, and the risk of severe acute skin and oral mucosa reactions in nasopharyngeal carcinoma patients in China. METHODS: 114 patients with nasopharyngeal carcinoma were sequentially recruited in this study. Heparinized peripheral blood samples were taken for SNPs analysis before the start of radiation treatment. SNPs in XRCC1 (194Arg/Trp and 399Arg/Gln) gene were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Dermatitis at upper neck and oral mucositis were clinically recorded according to the Common Terminology Criteria for Adverse Events v.3.0. RESULTS: The variant allele frequencies were 0.289 for XRCC1 194Trp and 0.263 for XRCC1 399Gln. Of the 114 patients, 24 experienced grade 3 acute dermatitis and 48 had grade 3 acute mucositis. The XRCC1 399Arg/Gln was significantly associated with the development of grade 3 dermatitis (Odds Ratio, 2.65; 95% CI, 1.04-6.73; p = 0.037, χ2 = 4.357). In addition, it was also associated with higher incidence of grade 3 mucositis with a borderline statistical significance (Odds Ratio, 2.11; 95% CI, 0.951-4.66; p = 0.065, χ2 = 3.411). The relationship between XRCC1 194Arg/Trp and acute dermatitis, and mucositis was not found. CONCLUSIONS: Our investigation shows, for the first time, that patients with the XRCC1 399Arg/Gln genotype were more likely to experience severe acute dermatitis and oral mucositis. With further validation, the information can be used to determine personalized radiotherapy strategy.

Cigarette smoking in China: public health, science, and policy.

Throughout the world, cigarette smoking is a habit that causes serious health, economic, and social problems. Therefore, many countries have taken an active role to control and to ban smoking. The chronic smoking problem in China is particularly acute because China has the largest population of smokers in the world, over 300 million currently. If 30% of these smokers were to die of smoke-related diseases in the next 20 years, the impact from the more than 90 million premature deaths could be damaging to China. In addition, numerous non-smokers also experience health problems from exposure to environmental tobacco smoke. China's efforts to reduce or to ban smoking in certain public places have not been well-coordinated or enforced compared with those in other countries. Therefore, success has been minimal. Consequently, leaders in China should not be complacent about combating the serious national health problem. A multiprong approach in combination with the MPOWER policy from the World Health Organization that targets different levels of acquisition of the smoking habit must be used. Examples may include the government's reduced reliance on profits from the sale of cigarettes, the elimination of advertisements that encourage smoking among young individuals, the presentation of more graphic illustration of harmful effects from smoking on every pack of cigarettes, higher taxes/prices on cigarettes, and the implementation of enforceable bans on smoking in public places. As shown in other countries, such coordinated effort can be highly effective in the reduction of smoking and can have healthy consequences.

XRCC1 Arg399Gln gene polymorphism and breast cancer risk: a meta-analysis based on case-control studies.

BACKGROUND: The Arg399Gln polymorphism in the XRCC1 DNA repair gene is likely to be involved with the development of breast cancer (BC). However, there have been inconsistent reports of association. The objective of this study was to systematically evaluate the published papers. METHODS: We performed a meta-analysis of 44 published case-control studies fitting our eligibility criteria. These studies involved XRCC1 Arg399Gln polymorphisms in 20,841 BC cases and 22,688 controls in dominant (GlnGln+ArgGln vs. ArgArg), recessive (GlnGln vs. ArgGln+ArgArg), and co-dominant (GlnGln vs. ArgArg) inheritance models. Analyses of Asian, African and Caucasian ethnic subgroups was also conducted. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of associations. RESULTS: Our overall analyses indicated Arg399Gln to be associated with a trend of increased BC risk when using recessive (OR=1.15, 95%CI: 1.05-1.27), and co-dominant models (OR=1.15, 95%CI: 1.04-1.27) to analyze the data. In ethnic subgroups, Arg399Gln significantly increased BC risk in Asians (OR=1.54, 95%CI: 1.18-2.01) when using recessive model analysis, in Africans (OR=1.30, 95%CI: 1.07-1.60) when using dominant model analysis, and in Asians (OR=1.50, 95%CI: 1.15-1.97) and Africans (OR=1.80, 95%CI: 1.08-3.02) when using the co-dominant model analysis. CONCLUSIONS: From our meta-analysis of data from 44 publications, we conclude that XRCC1 Arg399Gln allele is a risk factor for the development breast cancer, especially among Asian and African populations.

Infection and integration of human papillomavirus in esophageal carcinoma.

Infection with human papillomavirus (HPV) could be a suspected or potential modifiable risk factor in esophageal carcinoma (EC) but findings have not been consistent. We therefore investigated the epidemiology of HPV infection and integration in the pathogenesis of esophageal carcinoma (EC) in the Shantou region, China. This was a retrospective study involving nested PCR to evaluate HPV presence, HPV genotyping, and analyzing HPV-16 integration status in esophageal tumor tissues (n=106) and paired tumor-adjacent normal tissues, as well as normal esophagus tissue from control subjects (n=100). The detection rates of HPV DNA in EC and tumor-adjacent tissue were significantly higher than that in normal controls (77.4% and 80.2% vs. 33.0%). HPV infection was mainly found in adults, ages 35-47 years old, and the infection rate was negatively associated with the age of EC patients (P-trend<0.05). In addition, the HPV infection rates in patients who smoked was 3.27 times higher than in non-smoking patients (84.9% vs. 67.4%, P<0.05) but was not associated with gender, alcohol consumption, tumor grade or lymph-node metastasis of EC patients. The distribution of HPV genotypes in patients from high to low proportion was HPV-16, -58, -18, -33, -31 and -11. Infection with multiple HPV genotypes mainly included HPV-16/-18 and HPV-16/-33. The integration rate of HPV-16 in EC tissue was higher than that in tumor-adjacent and control tissues (93.4% vs. 50.9% and 45.5%). Our findings indicate that infection with HPV, especially the high-risk HPV, and their integration suggest an association in malignant transformation of EC in the high-incidence EC region in Shantou, China.

Association of MDR1 and ERCC1 polymorphisms with response and toxicity to cisplatin-based chemotherapy in non-small-cell lung cancer patients.

Among the cancer patient population, resistance to therapy is a major cause for therapeutic failure and for human sufferings, especially for the cancer with poor prognosis. Therefore, finding factors that contribute to drug resistance is a major research interest. In this study, we have investigated whether polymorphisms in genes that control import/export of drugs (MDR1) and that repair DNA adducts (ERCC1) are involved with drug resistance in non-small cell lung cancer (NSCLC) patients. We have recruited 95 patients with advanced NSCLC (stages IIIB-IV) who were specifically treated with platinum-based chemotherapy. We used the ligase detection reactions assay (LDR) to detect polymorphisms in ERCC1 118C/T, and MDR1 2677T/A, E1/-129T/C, and C3435T in peripheral blood lymphocytes from the patients. The haplotype of MDR1 gene single nucleotide polymorphisms (SNPs) were analyzed using the SHEsis software platform on line. We found that none of the single polymorphisms was associated with treatment response or related toxicity. However, patients carrying at least one variant MDR1 2677 T allele was associated with a significantly increased risk of drug resistance (OR=1.844, 95% CI=1.01-3.53, P=0.04) but also with a significantly increased risk of gastrointestinal toxicity (P=0.03) but not hemato-, hepato- or nephro-toxicities. Moreover, we analyzed the haplotypes of the three polymorphisms in MDR1. The patients harboring the E1/-129T-2677T-3435C haplotype had a significantly better response to chemotherapy compared with those having the other haplotypes (P=0.02, 95% CI=1.20-25.87), and a marginally significant association with increased risk of gastrointestinal toxicity (P=0.02, 95% CI=1.15-3.88). Our results suggested that gene polymorphisms in MDR1G2677T/A may be a predictive marker of platinum-based treatment response and of secondary effects, especially gastrointestinal toxicity for advanced NSCLC patients.

Association of polymorphisms in proinflammatory cytokine genes with the development of oral cancer in Southern Thailand.

Oral squamous cell carcinoma (OSCC) is highly prevalent in southeastern Asia suggesting that region-specific environmental and biological factors contribute to the development of this cancer. Exposure to oral carcinogens (i.e. betel quid) and pathogenic agents (i.e. papilloma virus) is common among individuals that develop OSCC in countries such as Thailand, India etc. However, not all individuals with such exposures develop the disease suggesting that other factors further increase susceptibility to OSCC. It is therefore plausible that functional variants in DNA repair genes and/or genes controlling inflammation and immunological response play a role in determining susceptibility to OSCC. Previous studies (including ours) have found an association between variants in DNA repair genes and increased susceptibility to OSCC. By extension, the current study examined the association between SNPs in genes encoding proteins involved in inflammation and immunomodulation (IL1alpha, IL1beta, IL8, TNFalpha) and OSCC. A total of 107 cases and 157 controls were analyzed. OSCC cases were more likely to carry the "T" allele at the IL1alpha(+4845) SNP than controls (OR=2.0, 1.0-4.4). OSCC cases that smoke and drink were more likely to carry either the "T" allele at the IL1beta(+3953) SNP (OR=10.4, 1.1-93.2) or the "C" allele at the TNFalpha(-1031) SNP (OR=3.4, 1.0-11.4) than controls. These results support the hypothesis that variants in inflammatory or immunomodulatory genes influence susceptibility to OSCC in Thailand. Larger studies are needed to confirm these results and more importantly to properly investigate the complex interactions among genetic variants in DNA repair and inflammation and other non-genetic susceptibility factors. In addition, laboratory experiments designed to determine the functional properties of the genetic variants are needed.

Challenge assay: A functional biomarker for exposure-induced DNA repair deficiency and for risk of cancer.

A variety of biomarkers have been used to monitor exposed populations to determine potential health hazards from their exposure to environmental toxic agents. However, the majority of these biomarkers have been focused onto the identification of biological damage from the exposure. Therefore, there is a need to develop functional biomarkers that can identify exposure-induced functional deficiencies. More importantly, these deficiencies should be positioned along pathways that are responsible for the development of specific diseases. One of such pathways belongs to the extensive and complex DNA-repair machinery. The machinery thus becomes a large target for damage from environmental toxic agents. The hypothesis is that damage to any component of a repair pathway will interfere with the pathway-specific repair activities. Therefore, when cells from exposed populations are challenged with a DNA-damaging agent in vitro, the in vivo exposure-induced repair deficiency will be dramatically amplified and the deficiency will be detectable in a challenge assay as increased chromosome aberrations, micronuclei or un-repaired DNA strand breaks. The challenge assay has been used in different laboratories to show that a variety of exposed populations (with exposure to air pollutants, arsenic, benzene, butadiene, cigarette smoke, incense smoke, lead, mercury, pesticides, uranium or xylene but not to low concentrations of air pollutants or butadiene) expressed abnormal challenge response. The predicted health consequences of some of these studies have also been validated. Therefore, the challenge assay is a useful functional biomarker for population studies. Details of the challenge assay and its application will be presented in this review.