Expression variation of OGG1 and HPRT gene and DNA damage in arsenic exposed industrial workers

Arsenic exposure alters redox balance, induces DNA damage, and deregulates many genes. OGG1 gene involved in base repair mechanism, for excision of 8-oxoguanine (8-oxoG) from DNA formed as a result of accumulation of ROS in cell. HPRT gene encode transferase enzymes involved in purine recycling mechanism. The main focus of the study was to evaluate the expression variation in HPRT, OGG1 gene expression, and DNA damage of industrial workers. Blood samples of 300 occupational workers were collected from welding, brick kiln, furniture, pesticide, and paint industry (n = 60/industry) to evaluate the expression variation in HPRT, OGG1 gene expression, and DNA damage in blood cells by comet assay along with age and gender matched 300 control individuals. Blood arsenic content was higher (P\u3c0.001) in an industrial group compared to the control. OGG1 and HPRT expression were (P\u3c0.05) downregulated in exposed workers compared to controls. Spearman correlation analysis showed a significant positive correlation between HPRT vs OGG1 (P\u3c 0.0001) in exposed workers compared to controls. Altered expression of both genes was observed between workers with \u3c25years and \u3e25years of age as well as between workers with \u3c10years and \u3e10year exposure. Reduced expression (P\u3c0.05) of both genes and a high extent of DNA damage was evident in exposed smokers compared to respective non-smokers. DNA fragmentation was higher (P\u3c0.05) in the furniture, welding and brick kiln group compared to control, and other industries. The present study suggests that altered expression of OGG1 and HPRT gene induce oxidative stress, showed a negative impact on the recycling of purines leading to DNA damage which increase the vulnerability of workers to carcinogenicity

Loss of Mitochondrial Tumor Suppressor Genes Expression Is Associated with Unfavorable Clinical Outcome in Head and Neck Squamous Cell Carcinoma: Data from Retrospective Study

<div><p>Mitochondrial genes play important roles in cellular energy metabolism, free radical generation, and apoptosis. Dysregulation of these genes have long been suspected to contribute to the generation of reactive oxygen species (ROS), increased proliferation and progression of cancer. A family of orthologues of yeast silent information regulator 3 (SIRT3), 4 (SIRT4) and mitochondrial tumor suppressor 1 (MTUS1) are important mitochondrial tumor suppressor genes which play an important role in the progression of multiple cancers. However, their role in the development of oxidative stress, enhanced proliferation and progression of head and neck squamous cell carcinoma (HNSCC) has not yet been studied. In this study we aimed to test the association between reduced mitochondrial tumor suppressor genes’ activities and enhancement in tissue oxidative stress and cell proliferation in HNSCC cases. The expression of mitochondrial tumor suppressor genes (SIRT3, SIRT4 and MTUS1), mitochondrial DNA repair gene (OGG1-2a) and a proliferation marker (Ki-67) was studied in a study cohort of 120 HNSCC patients and controls with reverse transcriptase polymerase chain reaction (RT-PCR) and real-time PCR (qPCR) in order to determine the potential prognostic significance of these genes. A statistically significant downregulation of SIRT3 (p<0.001), SIRT4 (p<0.0001), MTUS1 (p<0.002) and OGG1 (p<0.0001) was observed in HNSCC compared to control samples. Ki-67 was also overexpressed (p<0.0001) in HNSCC versus control samples. Additionally, to explore gene–gene relationship, we observed a positive spearmen correlation between SIRT3 versus SIRT4 (r = 0.523***, p<0.0001), SIRT3 versus MTUS1 (r = 0.273***, p<0.001), SIRT3 versus OGG1-2a (r = 0.213*, p<0.03), SIRT4 versus OGG1 (r = 0.338***, p<0.0001) and MTUS1 versus OGG1-2a (r = 0.215*, p<0.03) in HNSCC cases. A negative spearman correlation was observed between OGG1 versus Ki-67 (r = -0.224**, p<0.01) and OGG1-2a versus Ki-67 (r = -0.224**, p<0.01) in HNSCC cases. Here we report that the deregulation of mitochondrial tumor suppressor genes (SIRT3, SIRT4 and MTUS1) in relation to decreased expression of mitochondrial DNA repair gene OGG1-2a and increased proliferation (measured by proliferation marker Ki-67) may be considered important factors in the development of head and neck squamous cell carcinoma.</p></div

mRNA expression of Ki-67 in HNSCC cases of study cohort.

<p>Box plot comparing the Ki-67 mRNA levels of HNSCC and normal control samples, HNSCC samples with clinical stage I–II and clinical stage III–IV, with different T stages, with lymph node (N1–N2) and without lymph node (N0), with metastasis (M1-M2) and without metastasis (M0), with survival status and HNSCC samples with different grades. The p-values were computed using one-way analysis of variance and Tukey s’ post hoc test.</p

mRNA expression of MTUS1 in HNSCC cases of study cohort.

<p>Box plot comparing the MTUS1 mRNA levels of HNSCC and normal control samples, HNSCC samples with clinical stage I–II and clinical stage III–IV, with different T stages, with lymph node (N1–N2) and without lymph node (N0), with metastasis (M1-M2) and without metastasis (M0), with survival status and HNSCC samples with different grades. The p-values were computed using one-way analysis of variance and Tukey s’ post hoc test.</p

Correlations between mitochondrial tumor suppressor genes (<i>SIRT3</i>, <i>SIRT4</i>, <i>MTUS1</i>), mitochondrial DNA repair gene (<i>OGG1-2a</i>), proliferation marker (<i>Ki-67</i>) expression and clinicopathological characteristics of primary HNSCC^†.

<p>Correlations between mitochondrial tumor suppressor genes (<i>SIRT3</i>, <i>SIRT4</i>, <i>MTUS1</i>), mitochondrial DNA repair gene (<i>OGG1-2a</i>), proliferation marker (<i>Ki-67</i>) expression and clinicopathological characteristics of primary HNSCC<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0146948#t002fn001" target="_blank">^†</a>.</p

mRNA expression of SIRT4 in HNSCC cases of study cohort.

<p>Box plot comparing the SIRT4 mRNA levels of HNSCC and normal control samples, HNSCC samples with clinical stage I–II and clinical stage III–IV, with different T stages, with lymph node (N1–N2) and without lymph node (N0), with metastasis (M1-M2) and without metastasis (M0), with survival status and HNSCC samples with different grades. The p-values were computed using one-way analysis of variance and Tukey s’ post hoc test.</p

Association of expression deregulation of SIRT3, SIRT4, MTUS1, OGG1-2a and Ki-67 in HNSCC and lymph node and metastasis.

<p>Association of expression deregulation of SIRT3, SIRT4, MTUS1, OGG1-2a and Ki-67 in HNSCC and lymph node and metastasis.</p

Interaction among susceptibility genotypes of PARP1 SNPs in thyroid carcinoma.

Polymorphisms in DNA repair genes may alter the repair mechanism which makes the person susceptible to DNA damage. Polymorphic variants in these DNA repair pathway genes such as Poly (ADP-ribose) polymerase- 1 (PARP1) have been associated with susceptibility of several types of cancer including thyroid. Many studies have been published on PARP1 gene polymorphisms and carcinogenesis with inconsistent results. The present study was designed to explore the link between the PARP1 polymorphisms and thyroid cancer risk. This case-control study was comprised of 456 thyroid cancer patients and 400 healthy controls. Three SNPs of PARP1 gene; rs1136410, rs1805414 and rs1805404 were analyzed using ARMS-PCR. The combined genotype and haplotype analysis were performed using haploview software 4.2. Major allele homozygote (CC) of rs1136410 and combined genotype (TT+TC) of rs180414 showed a significant association with thyroid cancer risk (OR = 1.30; 95% CI 0.99-1.77; P = 0.05) and (OR = 0.43; 95% CI = 0.27-0.67; P = 0.03). Histological subtype analysis showed the significant association of selected PARP1 SNPs with papillary, follicular and anaplastic subtypes in thyroid cancer patients. Haplotype analysis showed that TCT (p = 0.01), CTT (p = 0.02) and CTC (p = 0.03) were significantly higher in controls when compared to cases. However, TTC (p = 0.05) and TCC (p = 0.01) haplotype frequency was significantly higher in cases compared to controls. Global haplotype analysis showed that there was an overall significant difference between cases and controls (p = 0.001). Identification of these genetic risk markers may provide evidence for exploring insight into mechanisms of pathogenesis and subsequently aid in developing novel therapeutic strategies for thyroid cancer

OGG1 Mutations and Risk of Female Breast Cancer: Meta-Analysis and Experimental Data

In first part of this study association between OGG1 polymorphisms and breast cancer susceptibility was explored by meta-analysis. Second part of the study involved 925 subjects, used for mutational analysis of OGG1 gene using PCR-SSCP and sequencing. Fifteen mutations were observed, which included five intronic mutations, four splice site mutations, two 3′UTR mutations, three missense mutations, and a nonsense mutation. Significantly (pG and 3′UTR variant g.9798848G>A. Among intronic mutations, highest (~15 fold) increase in breast cancer risk was associated with g.9793680G>A (p<0.009). Similarly ~14-fold increased risk was associated with Val159Gly (p<0.01), ~17-fold with Gly221Arg (p<0.005), and ~18-fold with Ser326Cys (p<0.004) in breast cancer patients compared with controls, whereas analysis of nonsense mutation showed that ~13-fold (p<0.01) increased breast cancer risk was associated with Trp375STOP in patients compared to controls. In conclusion, a significant association was observed between OGG1 germ line mutations and breast cancer risk. These findings provide evidence that OGG1 may prove to be a good candidate of better diagnosis, treatment, and prevention of breast cancer