Purpose: The prognosis of breast cancer varies considerably among individuals, and inherited genetic factors may help explain this variability. Of particular interest are genes involved in defense against reactive oxygen species (ROS) because ROS are thought to cause DNA damage and contribute to the pathogenesis of cancer.Patients and Methods: We examined associations between 54 polymorphisms that tag the known common variants (minor allele frequency > 0.05) in 10 genes involved in oxidative damage repair (CAT, SOD1, SOD2, GPX1, GPX4, GSR, TXN, TXN2, TXNRD1, and TXNRD2) and survival in 4,470 women with breast cancer.Results: Two single nucleotide polymorphisms (SNPs) in GPX4 ( rs713041 and rs757229 ) were associated with all-cause mortality even after adjusting for multiple hypothesis testing (adjusted P = .0041 and P = .0035). These SNPs are correlated with each other (r²= 0.61). GPX4 rs713041 is located near the selenocysteine insertion sequence element in the GPX4 3′ untranslated region, and the rare allele of this SNP is associated with an increased risk of death, with a hazard ratio of 1.27 per rare allele carried (95% CI, 1.13 to 11.43). This effect was not attenuated after adjusting for tumor stage, grade, or estrogen receptor status. We found that the common allele is preferentially expressed in normal lymphocytes, normal breast, and breast tumors compared with the rare allele, but there were no differences in total levels of GPX4 mRNA across genotypes.Conclusion: These data provide strong support for the hypothesis that common variation in GPX4 is associated with prognosis after a diagnosis of breast cancer.

Endoplasmic reticulum (ER) is a central organelle in eukaryotic cells that regulates protein synthesis and maturation. Perturbation of ER functions leads to ER stress, which has been previously associated with a broad variety of diseases. ER stress is generally regarded as compensatory, but prolonged ER stress has been involved in apoptosis induced by several cytotoxic agents. Choline kinase α (ChoKα), the first enzyme in the Kennedy pathway, is responsible for the generation of phosphorylcholine (PCho) that ultimately renders phosphatidylcholine. ChoKα overexpression and high PCho levels have been detected in several cancer types. Inhibition of ChoKα has demonstrated antiproliferative and antitumor properties; however, the mechanisms underlying these activities remain poorly understood. Here, we demonstrate that ChoKα inhibitors (ChoKIs), MN58b and RSM932A, induce cell death in cancer cells (T47D, MCF7, MDA-MB231, SW620 and H460), through the prolonged activation of ER stress response. Evidence of ChoKIs-induced ER stress includes enhanced production of glucose-regulated protein, 78 kDa (GRP78), protein disulfide isomerase, IRE1α, CHOP, CCAAT/enhancer-binding protein beta (C/EBPβ) and TRB3. Although partial reduction of ChoKα levels by small interfering RNA was not sufficient to increase the production of ER stress proteins, silencing of ChoKα levels also show a decrease in CHOP overproduction induced by ChoKIs, which suggests that ER stress induction is due to a change in ChoKα protein folding after binding to ChoKIs. Silencing of CHOP expression leads to a reduction in C/EBPβ, ATF3 and GRP78 protein levels and abrogates apoptosis in tumor cells after treatment with ChoKIs, suggesting that CHOP maintains ER stress responses and triggers the pro-apoptotic signal. Consistent with the differential effect of ChoKIs in cancer and primary cells previously described, ChoKIs only promoted a transient and moderated ER stress response in the non-tumorogenic cells MCF10A. In conclusion, pharmacological inhibition of ChoKα induces cancer cell death through a mechanism that involves the activation of exaggerated and persistent ER stress supported by CHOP overproduction.

Epigenetic events, resulting changes in gene expression capacity, are important in tumour progression, and variation in genes involved in epigenetic mechanisms might therefore be important in cancer susceptibility. To evaluate this hypothesis, we examined common variants in 12 genes coding for DNA methyltransferases (DNMT), histone acetyltransferases, histone deacetyltransferases, histone methyltrasferases and methyl-CpG binding domain proteins, for association with breast cancer in a large case–control study ( N cases = 4474 and N controls = 4580). We identified 63 single nucleotide polymorphisms (SNPs) that efficiently tag all the known common variants in these genes, and are also expected to tag any unknown SNP in each gene. We found some evidence for association for six SNPs: DNMT3b-c 31721 t [ P (2 df) = 0.007], PRDM2-c 99243 t [ P (2 df) = 0.03] and t 105413 c [ P -recessive = 0.05], EHMT1-g -9441 a [ P (2df) = 0.05] and g 41451 t ( P -trend = 0.04), and EHMT2- S237S [ P (2df) = 0.04]. The most significant result was for DNMT3b-c 31721 t ( P -trend = 0.124 after adjusting for multiple testing). However, there were three other results with P < 0.05. The permutation-based probability of this occurring by chance was 0.335. These significant SNPs were genotyped in 75 human cancer cell lines from different tumour types to assess if there was an association between them and six epigenetic measures. No statistically significant association was found. However, a trend was observed: homozygotes for the rare alleles of the EHMT1 , EHMT2 and PRDM2 had a mean value for both trimethylation of K9 and K27 of histone H3 remarkably different to the homozygotes for the common alleles. Thus, these preliminary observations suggest the possible existence of a functional consequence of harbouring these genetic variants in histone methyltransferases, and warrant the design of larger epidemiological and biochemical studies to establish the true meaning of these findings.

It is generally believed that the initiation of breast cancer is a consequence of cumulative genetic damage leading to genetic alterations and provoking uncontrolled cellular proliferation and/or aberrant programmed cell death, or apoptosis. Reactive oxygen species have been related to the etiology of cancer as they are known to be mitogenic and therefore capable of tumor promotion. The aim of this study was to assess the role of common variation in 10 polymorphic genes coding for antioxidant defense enzymes in modulating individual susceptibility to breast cancer using a case-control study (N cases = 4,474 and N controls = 4,580). Both cases and controls were from the East Anglian region of the United Kingdom. We have identified a set of 54 single nucleotide polymorphisms (SNPs) that efficiently tag all the known SNPs in the 10 genes and are also expected to tag any unknown SNPs in each gene. We found no evidence for association of common variants in SOD1, SOD2, GPX1, GPX4, GSR, TXNRD1, and TXN2. There was borderline evidence for association of variants in CAT g27168a {P [2 degrees of freedom (df)] = 0.05}, TXN t2715c [P (2 df) = 0.007], and TXNRD2 A66S and TXNRD2 g23524a (P_trend = 0.074 and 0.046, respectively). For TXNRD2 A66S [AS versus AA: odds ratio (OR), 1.05; 95% confidence intervals (95% CI), 0.96-1.15; SS versus AA: OR, 1.12; 95% CI, 0.98-1.29], there are bioinformatics data to suggest that it is functional but confirmation in independent data sets is required before they can be regarded as definitive breast cancer susceptibility alleles. Even if confirmed, these four alleles would account for just 0.32% of the excess familial risk of breast cancer. (Cancer Res 2006; 66(2): 1225-33)

Context: Medullary thyroid carcinoma (MTC) is a characteristic tumor occurring in individuals with multiple endocrine neoplasia type 2 who carry germ-line mutations in RET (rearranged during transfection). However, most MTC occur in individuals without a family history. Objectives: The objective of this study was to explore the possibility that susceptibility in these cases results from low penetrance alleles of RET, its coreceptors, and ligands. Design: We carried out an association study in 135 sporadic MTC (sMTC) patients and 533 controls from the United Kingdom population. Results and Conclusions: We analyzed 33 polymorphisms in all nine genes involved in the glial cell line-derived neurotropic factor receptor-α (GFRα)-RET complex. This is the first association study in which all genes involved in this complex have been investigated for susceptibility to sMTC. We did not find any association between single nucleotide polymorphisms in the exonic regions of the GFRα2, GFRα3, GFRα4, glial cell line-derived neurotropic factor, neurturin, or persephin genes and risk of developing sMTC. We found a strong association between the disease and specific haplotypes of RET. We not only confirmed the previously described association with G691S and S904S (for heterozygotes: odds ratio, 1.85; range, 1.22–2.82; P = 0.004), but we found a novel protective effect associated with a specific haplotype (odds ratio, 0.39; range, 0.21–0.72; P = 0.005) revealing the existence of different genetic variants in the RET oncogene that either increase or decrease risk of sMTC.