Markers Of Individual Susceptibility Research Articles

The possible role of genetic testing in the early identification of patients at increased risk of developing anthracycline-induced cardiotoxicity

Abstract Background In the last years prognosis of cancer patients (pts) has been improved, but the develop of cardiotoxicity (CTX) in pts with low CV risk treated with cumulative doses of Anthracycline (ANT) considered safe, led to investigate the possible role of the genetic profile in the onset of CTX. Purpose To study the role of some single nucleotide polymorphisms (SNPs) as predictive genetic markers of individual susceptibility to CTX induced by anticancer treatment. Methods We have enrolled women with non-metastatic breast cancer who had to start a therapy with ANT. The presence of a known heart disease, a previous mediastinal irradiation and a previous treatment with ANT, were the main exclusion criteria. All pts underwent complete cardiological evaluation (ECG, echo) before the beginning of the therapy (T0), after each ANT cycle and every 3 months up to 1 year of follow-up after the end of treatment. During each visit, we performed the determination of troponin I (TnI) and NT-proBNP. The genetic profile of each pts was also investigated, analyzing 6 SNPs belonging to 3 different genes (two for each genes) coding for enzymes or enzyme systems involved in the metabolism of ANT. DNA extraction from blood samples was performed using the QIAamp DNA Mini kit (QIAGEN). The DNA extracted was genotyped (by performing TaqMan SNP Genotyping assays) identifying 3 possible variants for each SNPs: homozygosity for the protective and “at risk” variant and heterozygosity. Results 179 pts finished the follow-up and from the analysis of the trend of biomarkers we found that 53 pts (30%) showed a significant increase in TnI (>0.04ng/mL) or less than this cut-off but persistently >0.015ng/mL in at least 2 measurements (“TnI+ group”), in the remaining 126 pts the TnI remained non-measurable (“TnI− group”); 76 pts (43%) showed NT-proBNP values ≥125 ng/L in at least two consecutive determinations (“NT-proBNP + group”),in the remaining 57% of pts this increase was not detected (“NT-proBNP - group”). Comparing “TnI+ group” to “TnI− group” we observed that only the genotyping of the SNPs rs1149222 (G/T) belonging to the ABCB4 gene is distributed differently in the two groups, in particular the homozygosity for the “at risk” variant (G/G) was present in 13% of the pts of the “TnI+ group” vs 5% in the “TnI− group” (p 0.06). The results of the comparison of “NT-proBNP+ group” vs “NT-proBNP− group”, showed that the genotyping of the SNPs rs6759892 (G/T) belonging to the UGT1A6 gene was distributed differently, the homozygosity for the “at risk” variant (G/G) was present in 28% of the “NT-proBNP+ group” vs 17% in the “NT-proBNP− group” (p 0.07). Conclusion Together with the baseline clinical evaluation, genetic markers could contribute to the early identification of pts at high risk of developing CTX especially following treatment with ANT and they could support future therapeutic decisions and the planning of taylored strategies for the prevention of the CTX development. Funding Acknowledgement Type of funding source: None

Do GST Polymorphisms Modulate the Frequency of Chromosomal Aberrations in Healthy Subjects?

Rossi et al. (2009) described an association between chromosomal aberration (CA) frequency and cancer risk in a case–control study on 107 cancer cases and 291 controls, whereby they observed no modifying effect of polymorphisms in glutathione S-transferase M1 (GSTM1) and GSTT1. In our studies of 488 healthy individuals who shared the same environmental exposure in Slovakia and the Czech Republic, we observed a CA frequency of 2.35 ± 1.73 (mean ± SD) (Halasova et al. 2007; Musak et al. 2008; Naccarati et al. 2006; Slyskova et al. 2007; Vodicka et al. 2001, 2004a, 2004b). The frequencies (mean ± SD) for chromatid-type abberations (CTA) and chromosome-type aberrations (CSA) were 1.22 ± 1.21 and 1.15 ± 1.35, respectively. By analyzing modulating effects of genetic polymorphisms in GSTT1, GSTM1, and GSTP1 on CAs, CTAs, and CSAs (Table 1), we found no significant association between chromosomal damage and any of the studied polymorphisms. The results were further confirmed by logistic regression: for the GSTT1 null genotype, odds ratio (OR) = 1.35 [95% confidence interval (CI), 0.79–2.32; p = 0.27]; for the GSTM1 genotype, OR = 1.09 [95% CI, 0.74–1.62; p = 0.65]; and for a variant GSTP1 Val105Val genotype, OR = 0.83 [95% CI, 0.55–1.24; p = 0.36]. These data on a larger healthy population [previously published separately by Halasova et al. (2007), Musak et al. (2008), Naccarati et al. (2006), Slyskova et al. (2007), and Vodicka et al. (2001, 2004a, 2004b)] confirm the findings of Rossi et al. (2009) regarding GSTM1 and GSTT1 polymorphisms. Additionally, in our reanalysis, we did not observe any modulating effect of GSTP1 polymorphism on CA frequency. However, the modulating role of GST polymorphisms may not be excluded, particularly in interaction with heavy occupational exposure. In our study exploring chromosomal damage in tire-plant workers (Musak et al. 2008), CAs were significantly higher in subjects with GSTT1-null than in those with GSTT1-plus genotypes, particularly in association with smoking. Table 1 Distribution of analyzed genotypes and CA frequencies. In the past decade, CAs have been accepted as a predictive marker of cancer (Hagmar et al. 2004), particularly for colo-rectal and lung cancers (Boffetta et al. 2007; Norppa et al. 2006). Nevertheless, these studies, as well as the study of Rossi et al. (2009) may have limitations: For example, cohorts were recruited in various regions with different lifestyle and environmental backgrounds, and different laboratories were involved in processing and scoring the samples over many years. In earlier studies, virtually no data on individual susceptibility were available because of the lack of DNA for molecular analysis. The data on CAs presented here were obtained on healthy subjects from a homogeneous region with fairly similar socioeconomic background. The analysis of CAs reported in these studies (Halasova et al. 2007; Musak et al. 2008; Naccarati et al. 2006; Slyskova et al. 2007; Vodicka et al. 2001, 2004a, 2004b) were performed in two laboratories, using the same protocol and the same scoring criteria with regular slide exchanges to minimize interlaboratory and inter scorer differences. Also, native DNA from whole-blood samples for molecular genetic studies was collected simultaneously with the samples for cytogenetic investigations. Future prospective studies regarding CAs and cancer should be designed by taking into account the lifestyle and occupational/environmental exposures, along with factors of individual susceptibility. Some GST polymorphisms may modulate CA frequency through interaction with environmental factors. The next logical step for a confirmation of predictive values of CA frequencies in relation to cancer will be their determination in lymphocytes of cancer patients in association with clinical– pathological characteristics.

Changes in erythrocyte enzymes in humans long-term exposed to pesticides: Influence of several markers of individual susceptibility

Changes in erythrocyte δ-aminolevulinic acid dehydratase (ALA-D) have been reported after exposure to different pesticides, including organophosphates and paraquat. In this study, we have determined ALA-D in 135 pesticide applicators (sprayers) from an intensive agriculture setting at two periods with different pesticide exposure. Acetylcholinesterase (AChE) was used as a reference biomarker. The effects of the combined polymorphism of enzymes involved in the detoxification of pesticides (paraoxonase (PON1), benzoylcholinesterase (BChE), and glutathione S-transferase (GSTM1 and GSTT1)) on the level of the target erythrocyte enzymes were also studied as biomarkers of individual susceptibility. Sprayers presented significant lower levels of ALA-D and AChE than controls (41.3% and 14.5%, respectively) at the high exposure period. When all biomarkers of individual susceptibility to pesticides were considered at the same time, the GSTT1 null allele determined higher ALA-D and AChE activities at the period of high exposure to pesticides. PON1 R allele in turn determined lower AChE activity at the low exposure period. Null genotype for both GST subclasses (GSTM1 and GSTT1) was found to be the unique independent predictor of pesticide-related symptomatology. Interestingly, sprayers were consistently underrepresented among carriers of “unfavourable” BChE variants. In conclusion, ALA-D appears to be an important biological indicator of pesticide exposure and PON1 and GSTT1 are relevant determinants of susceptibility to chronic pesticide poisoning.

Endogenous estrogens and breast cancer risk: the case for prospective cohort studies.

It is generally agreed that estrogens, and possibly androgens, are important in the etiology of breast cancer, but no consensus exists as to the precise estrogenic or androgenic environment that characterizes risk, or the exogenous factors that influence the hormonal milieu. Nearly all the epidemiological studies conducted in the 1970s and 1980s were hospital-based case-control studies in which specimen sampling was performed well after the clinical appearance of the disease. Early prospective cohort studies also had limitations in their small sample sizes or short follow-up periods. However, more recent case-control studies nested within large cohorts, such as the New York University Women's Health Study and the Ormoni e Dieta nell'Eziologia dei Tumori study in Italy, are generating new data indicating that increased levels of estrone, estradiol and bioavailable estradiol, as well as their androgenic precursors, may be associated with a 4- to 6-fold increase in the risk of postmenopausal breast cancer. Further new evidence, which complements and expands the observations from the latter studies, shows that women with the thickest bone density, which may be a surrogate for cumulated exposure to hormones, experience severalfold increased risk of subsequent breast cancer as compared to women with thin bones. These data suggests that endogenous sex hormones are a key factor in the etiology of postmenopausal breast cancer. New prospective cohort studies should be conducted to examine the role of endogenous sex hormones in blood and urine samples obtained early in the natural history of breast cancer jointly with an assessment of bone density and of other important risk factors, such as mammographic density, physical activity, body weight, and markers of individual susceptibility, which may confer increased risk through an effect on the metabolism of endogenous hormones or through specific metabolic responses to Western lifestyle and diet.

Application of biomarkers in population studies for respiratory non-malignant diseases

Though the use of biomarkers has been mainly suggested for cancer studies, the possibility of its use in non malignant disease is considered. Markers of internal dose, markers of biologically effective dose and markers of early biologically effect have been typically used in basic research and, more recently, in epidemiology to characterize genotoxic carcinogenic agents. These markers (e.g. adducts to DNA or proteins) may be used mainly in the presence of chronic exposure to toxic agents (e.g. benzene or benzopyrene), additional markers such as carboxyhemoglobin, expired air to measure various VOC and heavy metals in biological fluids are also considered in the paper. Since airway obstructive disease (asthma, chronic bronchitis, emphysema) are the main disorders influenced by environmental factors (including air pollution), markers of individual susceptibility, such as atopy increased responsiveness of airways, initial level of lung function, must be considered for a more precise evaluation of the relationship between environmental exposure and health effects. Currently, the application of the determination of markers of exposure in non malignant disorders is very limited. In fact, the relationships between acute adverse respiratory effects and the exposure to air pollutants appears difficult since markers for common air pollutants are not available, and their detection appears difficult in acute conditions. Characterization of long term exposure may be performed in organ fluids (blood, urine, saliva) however it is important to recognize that concentration at that level may not reflect that observed in the target organ (e.g. lung).

Biochemical Epidemology of Bladder Cancer

Cooperation between epidemiology and the laboratory represents a promising perspective for the understanding of the carcinogenic process. We describe three collaborative investigations involving the use of markers of internal dose (in particular, hemoglobin adducts) and markers of individual susceptibility in the study of bladder cancer induction by tobacco smoke. These investigations suggest that (a) hemoglobin adducts formed by aromatic amines are a valid indicator of "biologically effective" internal dose and (b) genetically determined susceptibility due to metabolic polymorphism may play a role in chemically induced bladder cancer.

Biochemical epidemiology: Uses in the study of human carcinogenesis

The use of biochemical markers may improve the potentialities of etiologic epidemiology. Exposure markers or markers of biologically effective dose allow better exposure assessment, therefore decreasing misclassification in epidemiological studies. Markers of individual susceptibility (such as metabolic polymorphism) permit the identification of subgroups of subjects at higher risk of cancer. In general, the integration of biochemical methods and an epidemiological design is helpful in the study of the sources of interindividual variability in response to carcinogenic stimuli. We review several investigations making use of biochemical measurements in the field of cigarette-induced bladder cancer.