Manganese superoxide dismutase polymorphism, treatment-related toxicity and disease-free survival in SWOG 8897 clinical trial for breast cancer

High Levels of Superoxide Dismutase 2 Are Associated With Worse Prognosis in Patients With Breast Cancer

OBJECTIVE

Breast cancer is classified based on hormone receptor status and human epidermal growth factor receptor 2 (HER2) expression, including luminal, HER2+, or triple-negative (TNBC). The absence of a therapeutic target in TNBC and the resistance to treatment associated with other subtypes means that research for new biomarkers remains important. In this context, superoxide dismutase 2 (SOD2) has emerged as a potential therapeutic target due to its clinicopathological associations and its ability to predict responses in human tumors. To analyze SOD2 staining in samples obtained from individuals with breast cancer and explore its transcriptional pattern across tumor subtypes.

MATERIALS AND METHODS

SOD2 staining was assessed using the immunohistochemistry (IHC) in 80 samples from breast cancer patients. To analyze the expression profile at the transcriptional level, international databases such as cBioPortal (1,980 patients) and PrognoScan were accessed.

RESULTS

Significant differences were observed between SOD2 expression analyzed by IHC, and estrogen (p = 0.0008) and progesterone (p = 0.0003) receptors, as well as tumor subtypes (p<0.0001). These differences were found in conjunction with other associations, including clinical and pathological data, such as tumor stage (p = 0.0129), tumor size (p = 0.0296), and node metastasis (p = 0.0486). Moreover, elevated SOD2 expression correlated with an unfavorable prognosis. The in silico analysis revealed a similar pattern, despite operating at the transcriptional level. Moreover, notable correlations were identified between elevated SOD2 expression and worse survival.

CONCLUSION

These results highlight the importance of SOD2 in breast cancer, particularly in aggressive subtypes. Increased SOD2 staining correlates with poorer outcomes, suggesting it as a potential therapeutic target.

Development of cervical intraepithelial lesions and cervical cancer is not influenced by SOD2 RS4880 polymorhism

Some of the more than 200 known HPV types are essential for cervical cancer development, the third type of cancer most incident in the female population. However, for the malignant transformation occur, some cofactors are needed, as the reactive oxygen species (ROS), which can be neutralized by the antioxidant system. The SOD2 enzyme, encoded by the same name gene, is found in mitochondria and is part of the first line of defense against oxidative stress damage. Genetic polymorphisms can act by altering the efficiency of the enzyme, among which the most studied is the rs4880. Thus, the purpose of the present study was to evaluate the association of this polymorphism with HPV infection and the development of low and high grade squamous intraepithelial lesions (LSIL and HSIL) and cervical cancer, in 407 women attended by the public health system in Brazil. HPV detection in cervical secretion samples was carried out by polymerase chain reaction (PCR) and blood samples were used for polymorphism genotyping through PCR followed by restriction fragment length polymorphism (RFLP). PCR and restriction products were subjected to 10% polyacrylamide gel electrophoresis. HPV negative group (control) included 158 women and the HPV positive group (case) 249 women. The infected group was divided into No Lesion (n = 90), LSIL (n = 20), HSIL (n = 67) and cervical cancer (n = 72). The data found on socio-epidemiological characteristics and habits corroborated with data found in the literature. The distribution of genotypes in the control group was 51.9% women TC, 29.8% TT and 18.3% CC. In the case group, the distribution was 55.0% women TC, 26.1% TT and 18.9% CC. This is the first study evaluating the influence of SOD2 rs4880 polymorphism on HPV infection, the development of cervical intraepithelial lesions and cervical cancer in a Brazilian population, although additional studies are needed to corroborate the results.

8-Oxoguanine DNA Glycosylase (OGG1) Cys326 Variant: Increased Risk for Worse Outcome of Patients with Locally Advanced Rectal Cancer after Multimodal Therapy

Despite excellent loco-regional control by multimodal treatment of locally advanced rectal cancer, a substantial portion of patients succumb to this disease. As many treatment effects are mediated via reactive oxygen species (ROS), we evaluated the effect of single nucleotide polymorphisms (SNPs) in ROS-related genes on clinical outcome. Based on the literature, eight SNPs in seven ROS-related genes were assayed. Eligible patients (n = 287) diagnosed with UICC stage II/III rectal cancer were treated multimodally starting with neoadjuvant radiochemotherapy (N-RCT) according to the clinical trial protocols of CAO/ARO/AIO-94, CAO/ARO/AIO-04, TransValid-A, and TransValid-B. The median follow-up was 64.4 months. The Ser326Cys polymorphism in the human OGG1 gene affected clinical outcome, in particular cancer-specific survival (CSS). This effect was comparable in extent to the ypN status, an already established strong prognosticator for patient outcome. Homozygous and heterozygous carriers of the Cys326 variant (n = 105) encountered a significantly worse CSS (p = 0.0004 according to the log-rank test, p = 0.01 upon multiple testing adjustment). Cox regression elicited a hazard ratio for CSS of 3.64 (95% confidence interval 1.70-7.78) for patients harboring the Cys326 allele. In a multivariable analysis, the effect of Cys326 on CSS was preserved. We propose the genetic polymorphism Ser326Cys as a promising biomarker for outcome in rectal cancer.

Clinical and genetic risk factors for the prediction of hepatotoxicity induced by a docetaxel, epirubicin and cyclophosphamide regimen in breast cancer patients

Aim: To screen clinical and genetic risk factors and examine their combined effect on docetaxel, epirubicin and cyclophosphamide (TEC) regimen-induced liver injury (TEC-ILI). Patients & methods: We enrolled 396 breast cancer patients, and TEC-ILI-associated factors were screened by logistic regression analyses. Results: SOD2 rs4880 and ABCG2 rs2231142 polymorphisms correlated with an increased risk of TEC-ILI. Multivariate analysis incorporating clinical and genetic factors revealed that ABCC1 rs246221 (CC) and SOD2 rs4880 (AG/GG) increased the risk of TEC-ILI. Patients with at least two risk factors among nonalcoholic fatty liver disease, high low-density lipoproteinemia levels and the rs246221 or rs4880 adverse genotypes exhibited a significantly increased risk of developing TEC-ILI. Conclusion: The combination of clinical and genetic risk factors had higher predictive value for TEC-ILI than the interclinical risk factors alone.

Toxicity and Pharmacogenomic Biomarkers in Breast Cancer Chemotherapy

Breast cancer (BC) is one of the most prevalent types of cancer worldwide with high morbidity and mortality rates. Treatment modalities include systemic therapy, in which chemotherapy is a major component in many cases. Several chemotherapeutic agents are used in combinations or as single agents with many adverse events occurring in variable frequencies. These events can be a significant barrier in completing the treatment regimens. Germline genomic variants are thought of as potential determinants in chemotherapy response and the development of side effects. Some pharmacogenomic studies were designed to explore germline variants that can be used as biomarkers for predicting developing toxicity or adverse events during chemotherapy in BC. In this review, we reassess and summarize the major findings of pharmacogenomic studies of chemotherapy toxicity during BC management. In addition, deficiencies hampering utilizing these findings and the potential targets of future research are emphasized. Main insufficiencies in toxicity pharmacogenomics studies originate from study design, sample limitations, heterogeneity of selected genes, variants, and toxicity definitions. With the advent of high throughput genotyping techniques, researchers are expected to explore the identified as well as the potential genetic biomarkers of toxicity and efficacy to improve BC management. However, to achieve this, the limitations of previous work should be evaluated and avoided to reach more conclusive and translatable evidence for personalizing BC chemotherapy.

Diabetes mellitus, superoxide dismutase and peroxisome proliferator activated receptor gamma polymorphisms modify the outcome of end-stage renal disease patients of Han Chinese origin

AIM

Increased oxidative stress significantly modifies the outcome of patients with diabetes mellitus (DM) and end-stage renal disease (ESRD), and is counteracted by antioxidative capacity. We aimed to investigate whether antioxidant single nucleotide polymorphisms (SNPs) influence the outcome of ESRD individuals and the influences exerted by DM, which has not been tested before.

METHODS

We prospectively enrolled multi-centre ESRD patients of Han Chinese origin between 2002 and 2003, recording their antioxidant (superoxide dismutase [SOD2], glutathione peroxidase [GPX1]) and peroxisome proliferator activated receptor-γ (PPAR-γ) genotyping results, and stratified based on DM. They were followed up until 2008, with risk factors for mortality analyzed by Cox proportional hazard regression.

RESULTS

We discovered that diabetic ESRD carriers of CC genotype of SOD2 exon 2 had an increased risk of mortality compared to non-diabetic ones with other genotypes (hazard ratio [HR] 4.04, P = 0.04), while GPX1 SNPs had no influence. Interactions between SOD2 and PPAR-γ SNPs regarding the mortality influence were also detected (for SOD2 CC genotype x PPAR-γ exon 6 CT genotype, HR 3.19, P = 0.008), suggesting the importance of considering a combination panel of SNPs on patient survival.

CONCLUSION

This might be the largest study focusing on the relationship between antioxidant SNPs and the outcomes of diabetic ESRD patients of Han Chinese origin. More studies are needed to validate our findings.

There is no relationship between SOD2 Val-16Ala polymorphism and breast cancer risk or survival

Breast cancer is the most common diagnosed cancer among females worldwide. Superoxide dismutase 2 (SOD2), an antioxidant enzyme, may break the balance between the oxidant and antioxidant system to induce various diseases. The present study aimed to clarify the association between the SOD2 Val-16Ala polymorphism and breast cancer risk or survival. Thus, a meta-analysis of the relevant articles retrieved from PubMed and EMBASE databases was conducted to illuminate the association with odd ratios (ORs) or hazards ratios (HRs). A total of 26 eligible publications (n=38,008) were available in risk analysis and eight publications (n=5,746) in survival analysis. The results demonstrated a marginal association between breast cancer risk and SOD2 polymorphism in Caucasian patients [TT vs. CT + CC: (OR, 0.94; 95% confidence interval (CI), 0.88-1.00)]. However, no other positive results were observed in risk and survival of breast cancer in the whole study [T vs. C: (OR, 0.99; 95% CI, 0.96-1.02); CT vs. CC: (OR, 1.00; 95% CI, 0.95-1.05); TT vs. CC: (OR, 0.98; 95% CI, 0.92-1.05); TT vs. CT + CC: (OR, 1.00; 95% CI, 0.95-1.05); CT + TT vs. CC: (OR, 0.99; 95% CI, 0.95-1.05)]. The present meta-analysis indicated that there was no significant relationship between SOD2 Val-16Ala polymorphism and breast cancer risk or survival, although in Caucasian patients, the SOD2 TT genotype may marginally decrease the risk of breast cancer in comparison to the CT + CC genotype.

Actionable pharmacogenetic markers for prediction and prognosis in breast cancer

Breast cancer is a heterogeneous disease that necessitates proper patient classification to direct surgery, pharmacotherapy, and radiotherapy. Despite patients within the same subgroup receiving similar pharmacotherapy, substantial variation in clinical outcomes is observed. Pharmacogenetic variations with direct effect on pharmacokinetics and pharmacodynamics play a central role in clinical outcomes. Pharmacogenetic markers associated with clinical outcome are known as biomarkers. They are termed prognostic biomarkers when their presence is associated with a specific clinical outcome. If the presence of such biomarkers guides treatment, they are termed predictive biomarkers. A number of pharmacogenetic markers have been described in relation to breast cancer pharmacotherapy both in the adjuvant and neoadjuvant setting. CYP2D6 allelic variants produce variable rates of tamoxifen metabolism and are associated with survival outcomes. Other biomarkers have been described in relation to other forms of endocrine therapy and trastuzumab. In neoadjuvant and adjuvant breast cancer chemotherapy, specific biomarkers were correlated with clinical outcomes and risk of drug toxicity. This review highlights key biomarkers in breast cancer pharmacotherapy with the potential of translating such study outcomes into clinical practice.

SOD2 rs4880 CT/CC genotype predicts poor survival for Chinese gastric cancer patients received platinum and fluorouracil based adjuvant chemotherapy

Adjuvant chemotherapy is a standard therapy for gastric cancer patients, however, treatment response is quite heterogeneous. Molecular biomarkers will be highly valuable to guide the therapy and predict the response and prognosis in these patients. The antioxidant enzymes superoxide dismutase 2 (SOD2) and glutathione S-transferase pi 1 (GSTP1) are involved in oxidative stress and drug detoxification, which modulate the efficacy of anticancer drugs. Here, we investigated the clinical associations of two functional single nucleotide polymorphisms of SOD2 and GSTP1 in stage II-III postoperative gastric cancer patients. SOD2 rs4880 and GSTP1 rs1695 were genotyped in 207 patients received postoperative platinum and fluorouracil based chemotherapy and 304 patients who did not. SOD2 rs4880 CT/CC significantly associated with decreased median overall survival time of 23 months when compared to the TT genotype (mean overall survival time of 65.2 months, P=0.002) only for patients received adjuvant chemotherapy. Stratification analysis showed SOD2 rs4880 CT/CC affected most significantly the clinical outcome for patients with tumor arising at gastric body (HR, 5.707, P=0.002), well to moderately differentiated adenocarcinoma (HR, 4.900, P<0.001), tumor of intestinal type (HR, 4.398, P<0.001), or tumor size less or equal to 5 cm (HR, 2.490, P=0.004); while GSTP1 rs1695 GA/GG was significant decreased overall survival time among patients with tumor arising at fundus or cardia (HR, 3.001, P=0.004), or mucinous or signet-ring cell carcinoma (HR, 4.750, P=0.042). The present study suggested the two polymorphisms would affect the adjuvant chemotherapy outcome in specific subtype of gastric cancer. SOD2 rs4880 could be used as a biomarker to predict the prognosis and response to therapy.

Oxidative stress-related genetic polymorphisms are associated with the prognosis of metastatic gastric cancer patients treated with epirubicin, oxaliplatin and 5-fluorouracil combination chemotherapy

Background

Oxidative stress genes are related to cancer development and treatment response. In this study, we aimed to determine the predictive and prognostic roles of oxidative stress-related genetic polymorphisms in metastatic gastric cancer (MGC) patients treated with chemotherapy.

Methods

In this retrospective study, we genotyped nine oxidative stress-related single nucleotide polymorphisms (SNPs) in NQO1, SOD2, SOD3, PON1, GSTP1, GSTT1, and NOS3 (rs1800566, rs10517, rs4880, rs1799895, rs662, rs854560, rs1695, rs2266637, rs1799983, respectively) in 108 consecutive MGC patients treated with epirubicin, oxaliplatin, and 5-fluorouracil (EOF) regimen as the first-line chemotherapy and analyzed the association between the genotypes and the disease control rate (DCR), progression-free survival (PFS), and overall survival (OS).

Results

We found that, in addition to a lower pathological grade (p = 0.017), NQO1 rs1800566 CT/TT genotype was an independent predictive factor of poor PFS (hazard ratio [HR] = 1.97, 95% confidence interval [CI] = 1.23–3.16; p = 0.005). PON1 rs662 AA/AG genotype was significantly associated with poor OS (HR = 1.95, 95% CI = 1.07–3.54; p = 0.029). No associations were detected between the nine SNPs and DCR.

Conclusions

NQO1 rs1800566 is an independent predictive factor of PFS for MGC patients treated with EOF chemotherapy, and PON1 rs662 is a noteworthy prognostic factor of OS. Information on oxidative stress-related genetic variants may facilitate optimization of individualized chemotherapy in clinical practice.

MnSOD rs4880 and XPD rs13181 polymorphisms predict the survival of breast cancer patients treated with adjuvant tamoxifen

The enzyme manganese superoxide dismutase (MnSOD) defends against oxidative stress caused by reactive oxygen species (ROS), whereas Xeroderma pigmentosum group D (XPD) protein is involved in DNA repair. Polymorphisms in these genes have previously been associated with the outcome of breast cancer.

MATERIAL AND METHODS

Two gene polymorphisms, the MnSOD Val16Ala (rs4880A>G) and the XPD Lys751Gln (rs13181A>C), were analyzed in a cohort of 396 Finnish breast cancer patients by using PCR-RFLP-based methods in a prospective case-control study. The overall survival (OS), breast cancer-specific survival (BCSS), and relapse-free survival (RFS), assessed by using Kaplan-Meier survival analysis and multivariate Cox regression analysis, were evaluated according to the adjuvant treatments and the rs4880 and rs13181 genotypes.

RESULTS

In the combined analysis of rs4880 and rs13181 genotypes for patients treated with adjuvant tamoxifen (TAM) an increasing number of low-risk genotypes (rs4880 AA, rs4880 AG, or rs13181 AA) was significantly associated with better RFS, BCSS, and OS (n=64). In addition, there was improved BCSS and RFS among TAM-treated patients carrying the wild-type rs4880 A allele as compared with the other genotypes (n=64). The wild-type rs13181 AA genotype was similarly associated with better RFS and BCSS in the TAM-treated population (n=65).

CONCLUSION

This is the first study to show that the MnSOD rs4880 and XPD rs13181 polymorphisms may influence the outcome of breast cancer patients receiving adjuvant TAM monotherapy. Patients carrying the rs4880 A allele or rs13181 AA genotype may have a reduced ability to scavenge ROS and repair the DNA damage generated by TAM treatment.

Manganese superoxide dismutase and breast cancer recurrence: a Danish clinical registry-based case-control study, and a meta-analysis

BACKGROUND

Manganese superoxide dismutase (MnSOD) inhibits oxidative damage and cancer therapy effectiveness. A polymorphism in its encoding gene (SOD2: Val16Ala rs4880) may confer poorer breast cancer survival, but data are inconsistent. We examined the association of SOD2 genotype and breast cancer recurrence (BCR) among patients treated with cyclophosphamide-based chemotherapy (Cyclo). We compared our findings with published studies using meta-analyses.

METHODS

We conducted a population-based case-control study of BCR among women in Jutland, Denmark. Subjects were diagnosed with non-metastatic breast cancer from 1990-2001, received adjuvant Cyclo, and were registered in the Danish Breast Cancer Cooperative Group. We identified 118 patients with BCR and 213 matched breast cancer controls. We genotyped SOD2 and used conditional logistic regression to compute the odds ratio (OR) and associated 95% confidence intervals (95% CI) of BCR. We used random-effects meta-analytic models to evaluate the association of SOD2 polymorphisms and BCR.

RESULTS

The frequency of the SOD2-Ala allele was 70% in cases versus 71% in controls; 40% versus 44% were heterozygotes, and 30% versus 25% were homozygotes, respectively. Heterozygote and homozygote carriers of the Ala allele had no increased rate of BCR (OR = 1.1, 95%CI = 0.65, 2.0, and OR = 0.87, 95%CI = 0.47, 1.6, respectively). Five studies informed the meta-analytic models; summary estimates associating BCR for homozygote, or any inheritance of the variant Ala allele were 1.18 (95%CI = 0.74, 1.88), and 1.18, (95%CI = 0.91, 1.54), respectively.

CONCLUSION

Our findings do not suggest that MnSOD enzymatic activity, as measured by SOD2 genotype, affects rates of BCR among patients treated with Cyclo.

Correlation between superoxide dismutase 1 and 2 polymorphisms and susceptibility to oral squamous cell carcinoma

Oxidative stress is significant in numerous types of cancer. Tobacco smoke, an important risk factor for oral squamous cell carcinoma (OSCC), is able to generate reactive oxygen species (ROS) and cause oxidative DNA damage. Superoxide dismutase (SOD) is an endogenous antioxidant enzyme that is critical in limiting the oxidative burden effectively. The purpose of this study was to investigate the effects of the mitochondrial SOD2 and Cu/Zn enzyme SOD1 gene polymorphisms on the susceptibility to and clinicopathological characteristics of OSCC, as well as the synergistic effect between these gene polymorphisms and the well-known risk factor of tobacco consumption. Patients with clinically diagnosed OSCC (n=362) and healthy normal individuals (n=358) were investigated for four single nucleotide polymorphisms (SNPs; rs4880, rs5746136, rs1804450 and rs11556620) by polymerase chain reaction-restriction fragment length polymorphism and DNA sequencing methods. Following adjustment for other confounders, no significant difference was observed in the rs5746136 SOD2 SNPs between the patients and controls. However, the incidence of the CT genotype of SOD2 SNP rs4880 was higher in the patients than in normal subjects in the additive model [CT vs. TT; P=0.045; adjusted odds ratio (AOR)=1.484; 95% confidence interval (CI), 1.009–2.182] and in the dominant model (CT/CC vs. TT; P=0.022; AOR=1.559; 95% CI, 1.067–2.278). For those who smoked, the incidence of the CT genotype of rs4880 increased markedly in the patients compared with the controls in the additive model (CT vs. TT; P=0.003; AOR=2.325; 95% CI, 1.330–4.064) and in the dominant model (CT/CC vs. TT; P=0.001; AOR=2.448; 95% CI, 1.417–4.230). For SOD1, polymorphisms at rs1804450 and rs11556620 were not present in any of the OSCC or control subjects. The results suggest that SOD2 rs4880 may be involved in the tumorigenesis of OSCC and may be useful as a genetic susceptibility marker for OSCC.

Identification of candidate polymorphisms on stress oxidative and DNA damage repair genes related with clinical outcome in breast cancer patients

Diverse polymorphisms have been associated with the predisposition to develop cancer. On fewer occasions, they have been related to the evolution of the disease and to different responses to treatment. Previous studies of our group have associated polymorphisms on genes related to oxidative stress (rs3736729 on GCLC and rs207454 on XDH) and DNA damage repair (rs1052133 on OGG1) with a predisposition to develop breast cancer. In the present work, we have evaluated the hypothesis that these polymorphisms also play a role in a patient's survival. A population-based cohort study of 470 women diagnosed with primary breast cancer and a median follow up of 52.44 months was conducted to examine the disease-free and overall survival in rs3736729, rs207454 and rs1052133 genetic variants. Adjusted Cox regression analysis was used to that end. The Kaplan-Meier analysis shows that rs3736729 on GCLC presents a significant association with disease-free survival and overall survival. The polymorphisms rs1052133 on OGG1 and rs207454 on XDH show a trend of association with overall survival. The analysis based on hormonal receptor status revealed a stronger association. The CC genotype on rs207454 (XDH) was significantly associated with lower time of disease free survival (p = 0.024) in progesterone receptor negative (PGR-) patients and rs3736729 (GCLC) was significantly associated with disease free survival (p = 0.001) and overall survival (p = 0.012) in the subgroup of estrogen receptor negative (ER-) patients. This work suggests that unfavorable genetic variants in the rs207454 (XDH) and rs3736729 (GCLC) polymorphisms may act as predictors of the outcome in negative progesterone receptor and negative estrogen receptor breast cancer patients, respectively.

Leveraging epidemiology and clinical studies of cancer outcomes: recommendations and opportunities for translational research

As the number of cancer survivors continues to grow, research investigating the factors that affect cancer outcomes, such as disease recurrence, risk of second malignant neoplasms, and the late effects of cancer treatments, becomes ever more important. Numerous epidemiologic studies have investigated factors that affect cancer risk, but far fewer have addressed the extent to which demographic, lifestyle, genomic, clinical, and psychosocial factors influence cancer outcomes. To identify research priorities as well as resources and infrastructure needed to advance the field of cancer outcomes and survivorship research, the National Cancer Institute sponsored a workshop titled "Utilizing Data from Cancer Survivor Cohorts: Understanding the Current State of Knowledge and Developing Future Research Priorities" on November 3, 2011, in Washington, DC. This commentary highlights recent findings presented at the workshop, opportunities to leverage existing data, and recommendations for future research, data, and infrastructure needed to address high priority clinical and research questions. Multidisciplinary teams that include epidemiologists, clinicians, biostatisticians, and bioinformaticists will be essential to facilitate future cancer outcome studies focused on improving clinical care of cancer patients, identifying those at high risk of poor outcomes, and implementing effective interventions to ultimately improve the quality and duration of survival.

The role of genetic breast cancer susceptibility variants as prognostic factors

Recent genome-wide association studies identified 11 single nucleotide polymorphisms (SNPs) associated with breast cancer (BC) risk. We investigated these and 62 other SNPs for their prognostic relevance. Confirmed BC risk SNPs rs17468277 (CASP8), rs1982073 (TGFB1), rs2981582 (FGFR2), rs13281615 (8q24), rs3817198 (LSP1), rs889312 (MAP3K1), rs3803662 (TOX3), rs13387042 (2q35), rs4973768 (SLC4A7), rs6504950 (COX11) and rs10941679 (5p12) were genotyped for 25 853 BC patients with the available follow-up; 62 other SNPs, which have been suggested as BC risk SNPs by a GWAS or as candidate SNPs from individual studies, were genotyped for replication purposes in subsets of these patients. Cox proportional hazard models were used to test the association of these SNPs with overall survival (OS) and BC-specific survival (BCS). For the confirmed loci, we performed an accessory analysis of publicly available gene expression data and the prognosis in a different patient group. One of the 11 SNPs, rs3803662 (TOX3) and none of the 62 candidate/GWAS SNPs were associated with OS and/or BCS at P<0.01. The genotypic-specific survival for rs3803662 suggested a recessive mode of action [hazard ratio (HR) of rare homozygous carriers=1.21; 95% CI: 1.09-1.35, P=0.0002 and HR=1.29; 95% CI: 1.12-1.47, P=0.0003 for OS and BCS, respectively]. This association was seen similarly in all analyzed tumor subgroups defined by nodal status, tumor size, grade and estrogen receptor. Breast tumor expression of these genes was not associated with prognosis. With the exception of rs3803662 (TOX3), there was no evidence that any of the SNPs associated with BC susceptibility were associated with the BC survival. Survival may be influenced by a distinct set of germline variants from those influencing susceptibility.

Clinical significance of SOD2 and GSTP1 gene polymorphisms in Chinese patients with gastric cancer

BACKGROUND

Excessive reactive oxygen species (ROS) accumulation is a common phenomenon in carcinogenesis. However, the rationale behind ROS involvement in gastric cancer is unclear. In this study, the authors investigated the clinical significance of the single nucleotide polymorphisms (SNPs) of 2 ROS metabolic process-related genes: superoxide dismutase 2 (SOD2) and glutathione S-transferase π (GSTP1).

METHODS

In total of 929 patients with gastric cancer who had definitive clinicopathologic and follow-up data were collected. SOD2 reference SNP 4880 (rs4880) and GSTP1 rs1695 genotyping were examined in DNA samples extracted from paraffin-embedded tumor tissue. Association of the 2 SNPs with each clinicopathologic feature was analyzed using the Pearson chi-square test and the independent Student t test. Gastric cancer-specific overall survival was analyzed using Kaplan-Meier curves and log-rank tests. Multivariate Cox regression analyses of these SNPs also were performed.

RESULTS

The SOD2 rs4880 CT + CC genotypes were significantly associated with a high level of lymph node metastasis (P = .023), whereas the GSTP1 rs1695 GA + GG genotypes were significantly associated with larger tumor size (>5 cm long; P = .048). Kaplan-Meier and Cox regression data indicated that the SOD2 rs4880 CT + CC genotypes alone (hazard ratio, 1.299; 95% confidence interval, 1.053-1.603; P = .015) and the GSTP1 rs1695 GA + GG combined genotypes (hazard ratio, 1.496; 95% CI, 1.078-2.074; P = .016) were independent predictors for overall survival.

CONCLUSIONS

The current data, based on a large cohort (n = 929) of Chinese patients with gastric cancer, suggested that the presence of SOD2 rs4880 and GSTP1 rs1695 genotypes may contribute to cancer progression as well as tumor aggressiveness. The components of ROS metabolism pathways may be potential therapeutic targets for this aggressive malignancy.

Clair DK. Manganese superoxide dismutase: guardian of the powerhouse

The mitochondrion is vital for many metabolic pathways in the cell, contributing all or important constituent enzymes for diverse functions such as β-oxidation of fatty acids, the urea cycle, the citric acid cycle, and ATP synthesis. The mitochondrion is also a major site of reactive oxygen species (ROS) production in the cell. Aberrant production of mitochondrial ROS can have dramatic effects on cellular function, in part, due to oxidative modification of key metabolic proteins localized in the mitochondrion. The cell is equipped with myriad antioxidant enzyme systems to combat deleterious ROS production in mitochondria, with the mitochondrial antioxidant enzyme manganese superoxide dismutase (MnSOD) acting as the chief ROS scavenging enzyme in the cell. Factors that affect the expression and/or the activity of MnSOD, resulting in diminished antioxidant capacity of the cell, can have extraordinary consequences on the overall health of the cell by altering mitochondrial metabolic function, leading to the development and progression of numerous diseases. A better understanding of the mechanisms by which MnSOD protects cells from the harmful effects of overproduction of ROS, in particular, the effects of ROS on mitochondrial metabolic enzymes, may contribute to the development of novel treatments for various diseases in which ROS are an important component.

Association of superoxide dismutases and NAD(P)H quinone oxidoreductases with prognosis of patients with breast carcinomas

Associations of transcript levels of oxidative stress-modifying genes SOD2, SOD3, NQO1 and NQO2 and their functional single nucleotide polymorphisms (SNPs) rs4880, rs1799895, rs2536512, rs699473, rs1800566 and rs1143684 with prognosis of breast cancer patients were studied. SNPs were assessed by allelic discrimination in a cohort of 321 breast cancer patients from the Czech Republic. Transcript levels were determined by real-time polymerase chain reaction (PCR) with absolute quantification in tumor and adjacent non-neoplastic control tissues. Both genotypes and transcript levels were then compared with available clinical data on patients. Patients carrying low activity allele Leu in NQO2 rs1143684 had a greater incidence of stage 0 or I disease (i.e., better prognosis) than patients with the Phe/Phe genotype. This association was more evident in patients without expression of progesterone receptors (p = 0.031). Patients carrying the Thr allele in SOD3 rs2536512 SNP had a significantly greater incidence of tumors expressing estrogen receptors than patients carrying the Ala/Ala genotype (p = 0.007). SOD3 transcript level was significantly higher in grade 1 or 2 tumors than in grade 3 tumors (p = 0.006). Patients carrying T allele in SOD3 rs699473 SNP had significantly poorer progression-free survival (PFS) than patients carrying the CC genotype (p = 0.038). The same applied to the subgroup of patients treated by hormonal regimens (p = 0.021). Patients carrying the high activity Ala/Ala genotype in SOD2 (rs4880) had significantly poorer PFS than Val allele carriers in the group treated by cyclophosphamide but not hormonal regimens (p = 0.004). Our results suggest that NQO2, SOD2 and SOD3 may significantly modify prognosis of breast cancer patients and that their significance should be further characterized.

Gene polymorphisms in cyclophosphamide metabolism pathway,treatment-related toxicity, and disease-free survival in SWOG 8897 clinical trial for breast cancer

PURPOSE

There are no established genetic markers for prediction of outcomes after cyclophosphamide (CP)-containing adjuvant therapy for breast cancer. In an ancillary study to a SWOG (Southwest Oncology Group) trial (S8897), we investigated functional polymorphisms in 4 genes in CP pharmacokinetic pathways in relation to hematologic toxicity and disease-free survival (DFS).

EXPERIMENTAL DESIGN

Germline DNA was available from 458 women who were at high risk of relapse and was randomized to CAF (CP, intravenous doxorubicin, and 5-fluorouracil) versus CMF (CP, intravenous methotrexate, and 5-fluorouracil) ± tamoxifen, and from 874 women who had a presumed favorable prognosis and did not receive adjuvant therapy. Odds ratios for grade 3 and 4 hematologic toxicity in the treated group and hazard ratios for DFS associated with selected functional polymorphisms in CYP2B6CYP3A4GSTA1 and GSTP1 were estimated by logistic regression and Cox proportional hazard regression.

RESULTS

Compared with women with AA genotypes, those with at least 1 GSTP1 variant G allele had reduced risk of grade 3 and 4 neutropenia [odds ratios (OR) = 0.63, 95% CI = 0.41-0.97] and leucopenia (OR = 0.59, 95% CI = 0.39-0.89). No other associations between single nucleotide polymorphisms and toxicity or survival were found in the treated or untreated group.

CONCLUSION

Known genetic variants in genes involved in CP pharmacokinetics may not have major effects on DFS in breast cancer patients. The lower risk of developing high-grade hematologic toxicity among women with variant GSTP1 alleles suggests that genetic markers in combination with clinical factors may be useful in defining a subgroup of women who are less susceptible to adverse hematologic toxicities with CP-containing therapies.