GSTM1 and GSTT1 copy numbers and mRNA expression in lung cancer

Germline copy number variations in BRCA1/2 negative families: Role in the molecular etiology of hereditary breast cancer in Tunisia

Hereditary breast cancer accounts for 5-10% of all breast cancer cases. So far, known genetic risk factors account for only 50% of the breast cancer genetic component and almost a quarter of hereditary cases are carriers of pathogenic mutations in BRCA1/2 genes. Hence, the genetic basis for a significant fraction of familial cases remains unsolved. This missing heritability may be explained in part by Copy Number Variations (CNVs). We herein aimed to evaluate the contribution of CNVs to hereditary breast cancer in Tunisia. Whole exome sequencing was performed for 9 BRCA negative cases with a strong family history of breast cancer and 10 matched controls. CNVs were called using the ExomeDepth R-package and investigated by pathway analysis and web-based bioinformatic tools. Overall, 483 CNVs have been identified in breast cancer patients. Rare CNVs affecting cancer genes were detected, of special interest were those disrupting APC2, POU5F1, DOCK8, KANSL1, TMTC3 and the mismatch repair gene PMS2. In addition, common CNVs known to be associated with breast cancer risk have also been identified including CNVs on APOBECA/B, UGT2B17 and GSTT1 genes. Whereas those disrupting SULT1A1 and UGT2B15 seem to correlate with good clinical response to tamoxifen. Our study revealed new insights regarding CNVs and breast cancer risk in the Tunisian population. These findings suggest that rare and common CNVs may contribute to disease susceptibility. Those affecting mismatch repair genes are of interest and require additional attention since it may help to select candidates for immunotherapy leading to better outcomes.

Similarities in mRNA expression of peripheral blood drug metabolizing enzymes and cancer marker genes with biopsy samples of head and neck cancer patients

Purpose: To develop peripheral blood mRNA expression profiles of drug metabolizing enzymes (DMEs) as a surrogate to monitor tobacco induced head and neck squamous cell carcinoma (HNSCC), attempts were made to investigate (i) similarities in alterations with the cancer marker genes in biopsy samples and (ii) if alterations similar to that seen in biopsy samples are reflected in peripheral blood. Methods: Total RNA from eight soft gingival tissues and eight biopsy samples of HNSCC patients and total DNA and RNA from blood of healthy controls (n = 150) and HNSCC patients (n = 150) was processed for expression and genotyping studies. Blood from patients receiving chemo-radiotherapy was processed for follow-up study. Results: qRT-PCR revealed significant increase in mRNA expression of DMEs in biopsy and blood samples of HNSCC patients when compared to controls. Similar alterations were observed in cancer marker genes in these samples. Patients with variant genotypes of DMEs showed greater magnitude of alterations in mRNA expression when compared to wild type controls. Responders of chemo-radiotherapy showed significant decline in induction of mRNA expression of DMEs and cancer marker genes Conclusions: The data suggest that peripheral blood expression profiles could be used to monitor tobacco-induced HNSCC as well as the treatment response.

GSTM1 gene expression and copy number variation in prostate cancer patients-Effect of chemical exposures and physical activity

BACKGROUND

Many etiological factors have been related to prostate cancer (CaP) development, progression, and survival, such as age, population origin, geographic area, occupational exposures, and nutrition and lifestyle factors. However, physical activity affords health benefits to cancer patients, including those with CaP. Glutathione S-Transferases enzymes have been linked to CaP because of their role in the detoxification of a wide variety of potential carcinogens, steroid hormones and xenobiotics. Among the different glutathione S-transferases isoforms, null genotype for GSTM1 has been associated with an increased risk of CaP, although data are controversial. As the relationship between copy number variation and gene expression of GSTM1 in CaP remains unexplored, this study analyzed GSTM1 gene expression and/or dosage effect on CaP risk and aggressiveness. The potential protective role of physical activity was also explored.

METHODS

Three hundred and seventeen patients (159 non-CaP and 158 CaP) were recruited from the Service of Urology (Hospital Virgen de las Nieves, Granada, Spain) over the period 2012 to 2014 and were followed-up until January 2018 to ensure a correct classification of control and patients. Individuals were classified in each group based on histological analysis of tissue biopsy, along with data on PSA level, Gleason score and T stage in patients with biopsies positive for CaP. Individuals with a negative biopsy were considered as controls. All controls underwent a systematic 20-core ultrasound guided biopsy in order to limit the false negative rate. Genomic DNA was extracted from peripheral blood to determine the exact copy numbers of GSTM1, and RNA was extracted from prostate tissue samples to determine GSTM1 gene expression. Both analyses were performed using the qPCR method. A questionnaire was administered to all patients to assess environmental exposures, lifestyle, and physical activity. The association of GSTM1 copy number variation and expression with the rest of variables was assessed by chi-square test and the Mann-Whitney test. Multiple logistic regression was used to assess which factors were associated with the risk of CaP.

RESULTS

The presence of 1 or 2 copies of the GSTM1 gene was not less prevalent in CaP compared to non-CaP patients; however, a significant decreased GSTM1 gene expression was observed in CaP tissue relative to non-CaP tissue (P = 0.003). CaP patients with environmental exposure to dust and smoke, and smoking habit had a significantly decreased GSTM1 gene expression (and near-significantly decreased for living in urban areas) as compared to non-CaP patients with the same exposures. In addition, physical activity was significantly associated with a lower risk of CaP (P = 0.006) and with increased GSTM1 gene expression (P = 0.002).

CONCLUSIONS

A reduced GSTM1 gene expression in prostate tissue was observed in CaP patients with some environmental chemical exposures. Intriguingly, physical activity might play a protective role against CaP development, possibly as a result of increasing GSTM1 gene expression in prostate tissue. However, this observation warrants further confirmation.

Polymorphisms of GSTM1, GSTT1, GSTP1 genes and chromosomal aberrations in lung cancer patients

PURPOSE

To study the potential links between genetic polymorphisms in the GSTT1, GSTM1, GSTP1 genes and the frequency of chromosomal aberrations (CAs) in lung cancer patients and healthy residents in Russian Federation.

METHODS

200 cells in well-spread metaphase with 46 chromosomes were examined for 353 newly diagnosed lung cancer patients (males) who received medical treatment in the Kemerovo Regional Oncology Center (Kemerovo, Russian Federation), and 300 healthy males from Kemerovo, Russian Federation. The polymorphisms of the GSTM1 del and GSTT1 del genes were analysed by multiplex PCR. Genotyping of the polymorphic variants in the GSTP1 (A313G, T341C) gene was performed using Real-time PCR with competing TaqMan probes complementary to the polymorphic DNA sites. The data analysis was performed using software STATISTICA 8.0 (StatSoft Inc., USA).

RESULTS

We discovered that a GSTM1 del polymorphism increases the frequency of chromosomal damage in smoking patients with lung cancer, a general group of lung cancer patients, donors with non-small cell lung cancer and patients in the latest stages of the malignant process. The synergetic effects of occupational exposure and the malignant process can induce some modifications in the cytogenetic status in lung cancer patients harbouring the GSTM1 del polymorphism.

CONCLUSIONS

CAs in peripheral blood lymphocytes can be used as biomarkers of the early biological effects of exposure to genotoxic carcinogens and may predict future cancer incidence in several epidemiologic studies. Genetic changes in genes encoding phase II detoxification enzymes are linked to decreases in the metabolic detoxification of environmentally derived genotoxic carcinogens.

GSTT1 is deregulated in left colon tumors

Our aim was to determine GSTT1 expression levels in left colon tumors and paired normal tissue in order to identify specific alterations in GSTT1 mRNA levels. Alterations in GSTT1 expression in twenty-four left- sided colon tumors and paired cancer free tissue were determined by qRT-PCR. Significant fold changes were determined with t-test. When compared with cancer free tissue, left colon cancers showed a significant decrease in GSTT1 expression. However, GSTT1 mRNA levels among different grades increased gradually in correlation with tumor grade. Our results suggest that downregulation of GSTT1 in left-sided colon cancers is an early event and is reversed with cancer progression, probably due to cellular defense mechanisms as a response to changes in the microenvironment.