Molecular epidemiology, biomarkers and cancer prevention

The era of nano-bionic: 2D materials for wearable and implantable body sensors

Nano-bionics have the potential of revolutionizing modern medicine. Among nano-bionic devices, body sensors allow to monitor in real-time the health of patients, to achieve personalized medicine, and even to restore or enhance human functions. The advent of two-dimensional (2D) materials is facilitating the manufacturing of miniaturized and ultrathin bioelectronics, that can be easily integrated in the human body. Their unique electronic properties allow to efficiently transduce physical and chemical stimuli into electric current. Their flexibility and nanometric thickness facilitate the adaption and adhesion to human body. The low opacity permits to obtain transparent devices. The good cellular adhesion and reduced cytotoxicity are advantageous for the integration of the devices in vivo. Herein we review the latest and more significant examples of 2D material-based sensors for health monitoring, describing their architectures, sensing mechanisms, advantages and, as well, the challenges and drawbacks that hampers their translation into commercial clinical devices.

Association of DNA repair and xenobiotic pathway gene polymorphisms with genetic susceptibility to gastric cancer patients in West Bengal, India

Gastric cancer is one of the most common malignancies in India. DNA repair gene or xenobiotic pathway gene polymorphisms have recently been shown to affect individual susceptibility to gastric cancer. Here, the possible interaction between common polymorphisms in X-ray repair cross complementing group I (XRCC1) gene and glutathione S-transferase (GST) genes (GSTM1, GSTT1 and GSTP1), smoking and alcohol consumption and overall survival in gastric cancer patients were evaluated. In this population-based case control study, 70 gastric cancer patients and 82 healthy controls were enrolled. The epidemiological data were collected by a standard questionnaire, and blood samples were collected from each individual. XRCC1 Arg194Trp, Arg280His and Arg399Gln polymorphisms were determined by polymerase chain reaction and direct DNA sequencing. GSTM1 and GSTT1 null polymorphisms and GSTP1 Ile105Val polymorphism were identified by multiplex polymerase chain reaction and restriction fragment length polymorphism (RFLP), respectively. The risk of gastric cancer was significantly elevated in individuals with XRCC1 Arg/Gln +Gln/Gln (p = 0.031; odds ratio = 2.32; 95 % confidence interval (CI) 1.07-5.06) and GSTP1 Val/Val genotype (p = 0.009; odds ratio = 8.64; 95 % CI 1.84-40.55). An elevated risk for GC was observed in smokers and alcohol consumers carrying GSTP1 Ile/Val +Val/Val genotype (p = 0.041; odds ratio = 3.71; 95 % CI 0.98-14.12; p = 0.002; odds ratio = 12.31; 95 % CI 1.71-88.59). These findings suggest that XRCC1 rs25487 and GSTP1 rs1695 can be considered as a risk factor associated with gastric cancer and might be used as a molecular marker for evaluating the susceptibility of the disease.

Molecular epidemiology of acute leukemia in children: causal model, interaction of three factors-susceptibility, environmental exposure and vulnerability period

Acute leukemias have a huge morphological, cytogenetic and molecular heterogeneity and genetic polymorphisms associated with susceptibility. Every leukemia presents causal factors associated with the development of the disease. Particularly, when three factors are present, they result in the development of acute leukemia. These phenomena are susceptibility, environmental exposure and a period that, for this model, has been called the period of vulnerability. This framework shows how the concepts of molecular epidemiology have established a reference from which it is more feasible to identify the environmental factors associated with the development of leukemia in children. Subsequently, the arguments show that only susceptible children are likely to develop leukemia once exposed to an environmental factor. For additional exposure, if the child is not susceptible to leukemia, the disease does not develop. In addition, this exposure should occur during a time window when hematopoietic cells and their environment are more vulnerable to such interaction, causing the development of leukemia. This model seeks to predict the time when the leukemia develops and attempts to give a context in which the causality of childhood leukemia should be studied. This information can influence and reduce the risk of a child developing leukemia.

Genetic variation and gastric cancer risk: a field synopsis and meta-analysis

BACKGROUND

Data on genetic susceptibility to sporadic gastric carcinoma have been published at a growing pace, but to date no comprehensive overview and quantitative summary has been available.

METHODS

We conducted a systematic review and meta-analysis of the evidence on the association between DNA variation and risk of developing stomach cancer. To assess result credibility, summary evidence was graded according to the Venice criteria and false positive report probability (FPRP) was calculated to further validate result noteworthiness. Meta-analysis was also conducted for subgroups, which were defined by ethnicity (Asian vs Caucasian), tumour histology (intestinal vs diffuse), tumour site (cardia vs non-cardia) and Helicobacter pylori infection status (positive vs negative).

RESULTS

Literature search identified 824 eligible studies comprising 2 530 706 subjects (cases: 261 386 (10.3%)) and investigating 2841 polymorphisms involving 952 distinct genes. Overall, we performed 456 primary and subgroup meta-analyses on 156 variants involving 101 genes. We identified 11 variants significantly associated with disease risk and assessed to have a high level of summary evidence: MUC1 rs2070803 at 1q22 (diffuse carcinoma subgroup), MTX1 rs2075570 at 1q22 (diffuse), PSCA rs2294008 at 8q24.2 (non-cardia), PRKAA1 rs13361707 5p13 (non-cardia), PLCE1 rs2274223 10q23 (cardia), TGFBR2 rs3087465 3p22 (Asian), PKLR rs3762272 1q22 (diffuse), PSCA rs2976392 (intestinal), GSTP1 rs1695 11q13 (Asian), CASP8 rs3834129 2q33 (mixed) and TNF rs1799724 6p21.3 (mixed), with the first nine variants characterised by a low FPRP. We also identified polymorphisms with lower quality significant associations (n=110).

CONCLUSIONS

We have identified several high-quality biomarkers of gastric cancer susceptibility. These data will form the backbone of an annually updated online resource that will be integral to the study of gastric carcinoma genetics and may inform future screening programmes.

Host genetic factors in hepatitis B infection, liver cancer and vaccination response: a review with a focus on Africa

The disease burden due to hepatitis B virus (HBV) infection remains significant; 350 million people are infected world-wide, and around half a million deaths each year are due to HBV-related liver disease and hepatocellular carcinoma (HCC). Infant immunisation against infection was introduced in the early 1980s, the vaccine is routinely administered across regions where the disease is endemic and has been shown to be safe and effective. However, the large number of older individuals with persistent infection means that disease will not be reduced significantly for several decades. Furthermore, failure to respond to the vaccination has been observed in about 5% of vaccinees and to date we have limited information on the durability of vaccine protection against infection. Hepatitis B infection and disease pathogenesis are known to be influenced by a number of factors including host genetics factors. This review aims to give an overview of the role of genetic variation in persistent HBV infection and the development of liver disease including HCC. Vaccine-induced immunity is, at least in part, heritable and we also discuss findings on the genetic control of responses to HBV vaccination. The epidemiology of HBV infection differs by world region, as does the genetic makeup of individuals originating from different regions. This review focuses on the situation in Africa, where hepatitis B is highly endemic.

Vitamin D and cancer: deciphering the truth

Vitamin D is a hormone-like micronutrient involved not only in calcium metabolism but also in a variety of biological activities (e.g., cell proliferation, apoptosis, angiogenesis, inflammation) that makes it a candidate anticancer agent. Preclinical studies support the therapeutic potential of vitamin D both alone and in combination with other therapeutics. Overall, epidemiological data suggest the existence of a link between vitamin D and cancer risk, whereas the results of clinical trials are quite conflicting. This article is a comprehensive and balanced overview of the current evidence in an attempt to critically interpret the wealth of scientific data thus far produced on this research field and to rationally envisage the next steps necessary to define the role of vitamin D in the therapeutic management of cancer.

Clinicopathologic features of metachronous or synchronous gastric cancer patients with three or more primary sites

PURPOSE

We investigated the clinicopathologic information of patients with gastric cancer with multiple primary cancers (GC-MPC) of three or more sites.

MATERIALS AND METHODS

Between 1995 and 2009, 105,908 patients were diagnosed with malignancy at Severance Hospital, Yonsei University Health System. Of these, 113 (0.1%) patients with MPC of three or more sites were registered, and 41 (36.3%) of these were GC-MPC. We retrospectively reviewed the clinical data and overall survival using the medical records of these 41 GC-MPC patients. We defined synchronous cancers as those occurring within 6 months of the first primary cancer, while metachronous cancers were defined as those occurring more than 6 months later.

RESULTS

Patients with metachronous GC-MPC were more likely to be female (p=0.003) and young than patients with synchronous GC-MPC (p=0.013). The most common cancer sites for metachronous GC-MPC patients were the colorectum, thyroid, lung, kidney and breast, while those for synchronous GC-MPC were the head and neck, esophagus, lung, and kidney. Metachronous GC-MPC demonstrated significantly better overall survival than synchronous GC-MPC, with median overall survival durations of 4.7 and 14.8 years, respectively, and 10-year overall survival rates of 48.2% and 80.7%, respectively (p<0.001).

CONCLUSION

Multiplicity of primary malignancies itself does not seem to indicate a poor prognosis. The early detection of additional primary malignancies will enable proper management with curative intent.

[Genetic epidemiological study on single nucleotide polymorphisms associated with hepatocellular carcinoma in patients with chronic HBV infection]

Hepatocellular carcinoma (HCC) is associated with hepatitis B virus (HBV) as an etiologic agent in 80% of cases, and is the major cause of death among HBV carriers. Family history of HCC is a known risk factor for the development of HCC among chronically HBV infected patients; therefore, genetic factors are likely to modify the risk of HCC. However, the genetic factors that determine progression to HCC remain mostly to be recovered. It is estimated that there are millions of single nucleotide polymorphisms (SNPs) within human genome and they are likely to explain much of the genetic diversity of individuals. In this review, the natural history of HBV infection and host genetic factors related to HCC, study design and target gene selection for the detection of SNPs related to the occurrence of HCC were discussed. Also, several SNPs or haplotypes, which were reportedly associated with increased or reduced risk of HCC occurrence in patients with chronic HBV infection, were reviewed. Especially, recent studies in Korea, one of the HBV endemic areas, were discussed. Screening of these polymorphisms might be useful in clinical practice to stratify the lower or higher risk group for HCC and might modify the design of HCC surveillance programs in patients with chronic HBV infection, if further genetic susceptibilities are identified. The ongoing studies of the distributions and functions of the implicated allele polymorphisms will not only provide insight into the pathogenesis of HCC, but may also provide a novel rationale for new methods of diagnosis and therapeutic strategies.

Asbestosis and catalase genetic polymorphism

Catalase (CAT) is part of the enzymatic defense system against reactive oxygen species (ROS), known to be involved in the pathogenesis of asbestosis. This study investigates whether CAT -262 C>T genetic polymorphism influences the risk of asbestosis in workers occupationally exposed to asbestos.The nested case-control study included 262 cases with asbestosis and 265 controls with no asbestos-related disease. Data on cumulative asbestos exposure and smoking were available. A real-time PCR assay was introduced for genotyping CAT -262 C>T promoter polymorphism.A slightly elevated risk of asbestosis was observed in subjects with the CAT -262 TT genotype compared to others (OR=1.36, CI 0.70-2.62). This risk did not change substantially after adjustment by sex, age, and smoking, but the involvement of cumulative asbestos exposure changed the OR to 1.91 (CI 0.93-3.91). These findings indicate that the CAT -262 TT genotype may be slightly associated with an increased risk of asbestosis. No synergistic effect was found between cumulative asbestos exposure and the CAT -262 TT genotype, but cumulative asbestos exposure acted as a confounder. These results are an important contribution to understanding the interactions between genetic and environmental factors that may modify the risk of asbestosis.

Genetic polymorphisms and disease prevention

Building upon the resources of traditional epidemiology, molecular epidemiology has extended our understanding that disease risk varies based not only upon acquired factors (e.g., exposures, behaviors, demographics), but also as a function of inherited factors (e.g., genetic polymorphisms). Individual susceptibility to cancer is influenced by polymorphisms in phase I enzymes (e.g., activation), phase 2 enzymes (e.g., detoxification), defects in the repair of DNA damage and other cancer susceptibility genes. Because tobacco use and nutrition represent behaviors/exposures which account for a significant number of cancer cases and deaths, these two factors are used to illustrate the relationship between genetic polymorphisms and disease prevention. Susceptibility to the health risks of smoking appears to be influenced by genetic factors that impact initiation, dependence, and nicotine metabolism. Nutrient metabolism also involves polymorphic enzyme pathways and gene-nutrient interactions may influence cancer risk. While the discipline of molecular epidemiology continues to face methodologic challenges related to the need to study large numbers of subjects, current knowledge can be applied to prevention activities. Genetic polymorphisms, and other molecular markers, can be used to develop clinical prevention studies targeted to unique subsets of persons at the highest risk of developing disease. Knowledge about the relationships between polymorphisms and disease outcomes can also be used for reinforcing healthy lifestyles, motivating positive behavior changes, helping to target medical therapy, and aiding in better focusing surveillance activities.

Use of genotypic selection to detect P53 codon 273 CGT>CTT transversion: application to an occupationally exposed population

CGT>CTT transversion in codon 273 of the P53 tumor-suppressor gene is one of the major mutations detected in human tumors. Within an epidemiological framework, we investigated the use of a genotypic selection method to measure this point mutation. The allele-specific polymerase chain reaction (AS-PCR) that was developed was able to detect 10 mutant copies of the gene among a total of 5 x 10(5) wild-type copies. We used this assay to detect CGT>CTT transversions in buccal cell DNA of production workers (n=76) from a viscose factory exposed to carbon disulfide (amongst other pollutants) and in the DNA of non-exposed office workers (n=67). The mutation appeared more frequently in the exposed than in the non-exposed worker who were smokers. The results of the study indicate that occupational exposure results in a significant increase in P53 CGT>CTT transversions and more especially identified occupational exposure in combination with smoking as a significant risk factor for the mutation. We conclude that AS-PCR of the P53 273rd codon transversions is a suitable technique for studying the effects of occupational exposure.

MMP-9 and MMP-2 gelatinases and TIMP-1 and TIMP-2 inhibitors in breast cancer: correlations with prognostic factors

The goal of our study was to analyse the prognostic values for some matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) in breast cancer. We evaluated the activity and the expression levels of MMP-9, MMP-2, TIMP-1 and TIMP-2 in malignant versus benign fresh breast tumor extracts. For this purpose, gelatinzymography, immunoblotting and ELISA were used to analyse the activity and expression of MMPs and TIMPs. We found that MMP-9 expression level and activity are increased in malignant tumors. In addition, MMP-9/TIMP-1 and MMP-2/TIMP-2 ratio values obtained by us were significantly different in malignant tumors compared to benign tumors. We suggest that the abnormal MMP-9/TIMP-1 balance plays a role in the configuration of breast invasive carcinoma of no special type and also in tumor growth, while altered MMP-2/TIMP-2 ratio value could be associated with lymph node invasion and used as a prognostic marker in correlation with Nottingham Prognostic Index. Finally, we showed that in malignant tumors high expression of estrogen receptors is associated with enhanced activity of MMP-2 and increased bcl- 2 levels, while high expression of progesterone receptors is correlated with low TIMP-1 protein levels.

Single Nucleotide Polymorphisms Associated with Hepatocellular Carcinoma in Patients with Chronic Hepatitis B Virus Infection

It is estimated that there are millions of single nucleotide polymorphisms (SNPs) within human genome and there are likely to explain much of the genetic diversity of individuals. Hepatocellular carcinoma (HCC) is etiologically associated with hepatitis B virus (HBV) in 80% of cases, and is the dominant cause of death among HBV carriers. Among patients with chronic HBV infection, family history is a known risk factor for the development of HCC; therefore, genetic factors are likely to modify the risk of HCC. However, the genetic factors that determine progression to HCC remain mostly to be investigated. In this review, we discussed that the natural history of HBV infection and host genetic factors related to HCC, study design and target gene selection for the detection of SNPs related to the occurrence of HCC. Also, we reviewed that several SNPs or haplotypes, which were reportedly associated with increased or reduced risk of HCC occurrence in patients with chronic HBV infection. Screening of these polymorphisms might be useful in clinical practice to stratify the lower or higher risk group for HCC and might modify the design of HCC surveillance programs in patients with chronic HBV infection, if further genetic susceptibilities are identified.

Searching for cancer-associated gene polymorphisms: promises and obstacles

Low-penetrance genetic variations appear to form the most essential component of the heritability of cancer risk. Search for relevant polymorphic candidates faces significant obstacles, due to both the high number of potentially promising single nucleotide polymorphisms (SNPs) and the intrinsic difficulties in identification of weak gene-disease interactions. At present, extensive case-control studies can be applied only to a limited number of gene polymorphisms. Therefore, the choice of SNPs that deserve an exhaustive populational analysis is of primary importance. Preferences are usually given to those genetic pathways, whose variability and role in cancer causation have been already shown by prior studies. The available electronic databases and software tools may allow further SNP sorting, based on functional predictions. The design for the pilot study may need to be different from the one for large-scale case-control analysis. Some investigations justify non-random patient selection for preliminary assessment of low-penetrance effects, with the emphasis on particularly susceptible individuals (familial, early onset, multiple cancer cases). Other presumably accelerating approaches suggest a decisive exclusion of SNP candidates showing only marginal effects, relaxed formats for rapid dissemination of preliminary data, use of more demonstrative controls such as elderly tumor-free subjects, etc. These short-cuts cannot be properly validated for the time being, due to the paucity of identified low-penetrance risk modifiers. It is expected that the increasing capacities of available DNA collections, coupled with the rapid development of high-throughput genotyping technologies, will vastly accelerate the research on polygenic cancer susceptibility.

The evolution of current medical and popular attitudes toward ultraviolet light exposure: part 3

In the 1930s, attitudes toward ultraviolet (UV) light exposure began to change significantly within the medical profession. UV radiation had been promoted as healthful since the century's start, and particularly after the discovery of its role in vitamin-D metabolism. Increasingly, however, attention would focus on the risks of UV light exposure from sunlamps and sunbathing. During this time, the American Medical Association established guidelines for the approval of UV lamps and the appropriate therapeutic uses of phototherapy. The landmark experiments of Findlay and other researchers, in which malignant skin tumors were induced in rodents after exposure to UV lamps or sunlight, would lead to widespread recognition of the carcinogenicity of UV radiation. The role of sunlight in the etiology of skin cancer was increasingly mentioned in articles in popular magazines in the 1940s and 1950s. There was rapid growth of the sunscreen industry as well, although product efficacy remained highly variable. In the 1950s, interest developed in the use of 8-methoxypsoralen ("the suntan pill") and dihyroxyacetone ("suntan in a bottle"). In spite of the known risks of UV exposure and attempts by physicians and other health professionals to educate the public and modify behavior, suntanning has remained tenaciously popular. Today, excessive UV light exposure is recognized as the major cause of the approximately 1.3 million cases of skin cancer in the United States each year.

Convergence of clinical toxicology and epidemiology in relation to health effects of chemicals

An integrated approach of clinical toxicology and epidemiology is an essential ingredient in environmental health risk management through molecular epidemiology and environmental genomics. The last decade has also seen the emergence of several biochemical markers useful in chemical risk assessment and in epidemiological studies. An appraisal of the concepts involved, the approaches required, and the potential scope of this approach is attempted here.

Surrogate endpoints in cancer drug development

Over the next three years a large number of novel, mechanistically targeted drugs will enter clinical trials for cancer. The remarkable progress in understanding the molecular biology of cancer has provided an enormous range of validated targets for drug discovery. Following lead optimisation and suitable pharmaceutical formulation these compounds have undergone rapid screening in preclinical models. Innovative methods of clinical development are now essential to ensure optimal dose determination and scheduling. The discovery of novel surrogates for efficacy is essential in this fast moving area and requires imaginative partnerships between academic groups and the pharmaceutical industry.