Asahi Hishida

Common Defects of ABCG2, a High-Capacity Urate Exporter, Cause Gout: A Function-Based Genetic Analysis in a Japanese Population

Dysfunctional genotype combinations of polymorphic adenosine 5′-triphosphate–binding cassette transporter gene ABCG2/BCRP, which encodes a high-capacity urate secretion transporter in human gut and kidney, are major causes of gout. Gout, the “Disease of Kings” as it is often known, is a painful medical condition characterized by sharp acute pain in bone joints, due to the high deposition of uric acid crystals from the blood serum into the surrounding cartilage. It affects approximately 1% of the U.S. population and remains a significant public health concern. The prevalence of gout is much higher in certain Asian ethnic groups, and is also reportedly rising in African Americans. Current medical treatments are aimed at ameliorating pain severity, but as the underlying genetic etiology of the disease unfolds, new targets for future therapies are likely to be found. Although genome-wide association studies (GWAS) have enabled the calculation of risk predispositions for a wide variety of complex diseases, the relation of gene function to the causality of disease-related mutations has remained largely unclear. A recent U.S. population–based study supported an association between urate levels and gout in individuals carrying variants in a multifunctional transporter gene, ABCG2. This study identified Q141K as a high-risk variant in nearly 10% of gout cases in Caucasians. Now, a team led by Hirotaka Matsuo report that in a Japanese population, another risk variant in ABCG2, namely the Q126X nonfunctional mutation, confers an even higher risk associated with an increase in uric acid deposition in the blood and may cause gout in Asians. Because this gene is responsible for giving rise to a protein that transports harmful waste products and metabolites out of the kidney and gut, they extensively validate the biological activity of ABCG2 using functional assays in vitro that effectively recapitulate human data obtained from Japanese individuals afflicted with the disease. These findings lend weight to previously reported GWAS; moreover, these newly identified specific high-risk variants that block urate secretion may serve as potential intervention points for quelling the disease. Gout based on hyperuricemia is a common disease with a genetic predisposition, which causes acute arthritis. The ABCG2/BCRP gene, located in a gout-susceptibility locus on chromosome 4q, has been identified by recent genome-wide association studies of serum uric acid concentrations and gout. Urate transport assays demonstrated that ABCG2 is a high-capacity urate secretion transporter. Sequencing of the ABCG2 gene in 90 hyperuricemia patients revealed several nonfunctional ABCG2 mutations, including Q126X. Quantitative trait locus analysis of 739 individuals showed that a common dysfunctional variant of ABCG2, Q141K, increases serum uric acid. Q126X is assigned to the different disease haplotype from Q141K and increases gout risk, conferring an odds ratio of 5.97. Furthermore, 10% of gout patients (16 out of 159 cases) had genotype combinations resulting in more than 75% reduction of ABCG2 function (odds ratio, 25.8). Our findings indicate that nonfunctional variants of ABCG2 essentially block gut and renal urate excretion and cause gout.

BMI-1 is Highly Expressed in M0-Subtype Acute Myeloid Leukemia

Recent studies have suggested that one of the polycomb group genes,BMI- 1, has an important role in the maintenance of normal and leukemic stem cells by repressing theINK4a/ARF locus. Here, we quantitatively examinedBMI- 1 expression level in samples from patients with acute myeloid leukemia (AML) and other hematologic malignancies. Moderate to highBMI- 1 expression was detected in AML patients, and theBMI- 1 expression levels in AML samples were significantly higher than in normal bone marrow controls(P =.0011). Specimens of French-American-British classification subtype M0 showed higher relative expression of the BMI-1 transcript (median, 390.2 x 10-3) than the other subtypes (median, 139.0 x 10-3)(P <.0001). Leukemia other than AML showed low to moderate expression. INK4a-ARF transcript expression tended to be inverse proportion to that of BMI-1. In an M0 patient with a high BMI-1 transcript level, the INK4a-ARF transcript level fell promptly and maintained a low value after the patient achieved complete remission. These results indicated that a subgroup of M0 patients has a high expression level of polycomb group geneBMI- 1, which may contribute to leukemogenesis.

Toll-Like Receptor 4 +3725 G/C Polymorphism, Helicobacter pylori Seropositivity, and the Risk of Gastric Atrophy and Gastric Cancer in Japanese

Background:  Toll‐like receptor 4 (TLR4) Asp299Gly and Thr399Ile polymorphisms were reported to be a risk factor of gastric carcinoma or its precursors in Caucasian and Indian population, but these polymorphisms are absent in Japanese. We investigated the associations of TLR4+3725 G/C polymorphism, another functional polymorphism of TLR4, with risk of gastric cancer and gastric atrophy in Japanese.

Transforming growth factor B1 T29C polymorphism and breast cancer risk in Japanese women.

BackgroundA cohort study for Caucasians aged 65 years or older demonstrated a marked breast cancer risk reduction for those with theCC genotype oftransforming growth factor B1 (TGF B1) T29C polymorphism. This is a prevalent case-control study to examine the reported risk reduction for Japanese women.Patients and MethodsA total of 232 histologically diagnosed breast cancer patients who visited Aichi Cancer Center Hospital between June 1999 and March 2000 were enrolled. The controls were 172 female outpatients without cancer at the same hospital. DNA was extracted from peripheral blood, andTGF B1 genotype was determined by PCR-CTPP.ResultsThe genotype frequency was 23.7% forTT, 49.2% forTC, and 27.1% forCC among controls, and 28.9%, 46.1%, and 25.0%, respectively, among cases. Age-adjusted odds ratio (OR) relative to theTT genotype was 0.81 (95% confidence interval, 0.50-1.31) for theTC genotype and 0.77 (0.45-1.34) for theCC genotype. For premenopausal women, theCC genotype was significantly associated with reduced risk of breast cancer in comparison with theTT genotype (OR =0.45, 0.20-0.98). The association was not observed for postmenopausal women (OR = 1.40, 0.64-3.08).ConclusionThe present study showed risk reduction for Japanese premenopausal women with theCC genotype, but not for postmenopausal Japanese women.

Common dysfunctional variants in ABCG2 are a major cause of early-onset gout

Gout is a common disease which mostly occurs after middle age, but more people nowadays develop it before the age of thirty. We investigated whether common dysfunction of ABCG2, a high-capacity urate transporter which regulates serum uric acid levels, causes early-onset gout. 705 Japanese male gout cases with onset age data and 1,887 male controls were genotyped, and the ABCG2 functions which are estimated by its genotype combination were determined. The onset age was 6.5 years earlier with severe ABCG2 dysfunction than with normal ABCG2 function (P = 6.14 × 10−3). Patients with mild to severe ABCG2 dysfunction accounted for 88.2% of early-onset cases (twenties or younger). Severe ABCG2 dysfunction particularly increased the risk of early-onset gout (odds ratio 22.2, P = 4.66 × 10−6). Our finding that common dysfunction of ABCG2 is a major cause of early-onset gout will serve to improve earlier prevention and therapy for high-risk individuals.

Polymorphisms of p53 arg72pro, p73 G4C14-to-A4T14 at exon 2 and p21 Ser31Arg and the risk of non-Hodgkin's lymphoma in Japanese

We hypothesized that the polymorphisms in the two p53 family genes (p53 Arg72Pro and p73 G4C14-to-A4T14 at exon 2 (G4A)) and p21 Ser31Arg polymorphism might modulate the risk of non-Hodgkins lymphoma, and conducted a hospital-based prevalent case control study at Aichi Cancer Center Hospital to clarify the association. Risk estimation for each genotype by the unconditional logistic model demonstrated the possible association between the p53 Pro72 allele and the risk of non-Hodgkins lymphoma in Japanese population (OR = 1.59; 95% CI, 0.99-2.57, P = 0.057), although no other significant association was observed. The analyses of statistical interactions between these three polymorphisms (p73 G4A, p53 Arg72Pro and p21 Ser31Arg polymorphisms) revealed the marginally significant OR for interaction between p53 Arg72Pro and p73 G4A polymorphisms (OR = 2.54; 95% CI, 0.97 6.62, P = 0.057). When those without p53 Pro72 and p73 A4T14 alleles were defined as a reference, those with p53 Pro72 and p73 A4T14 alleles demonstrated a significantly higher OR (2.08; 95% CI, 1.11-3.90, P = 0.023). Further examination with a sufficiently larger population and other ethnicities are required to confirm our findings.

Re: Population-Based Case–Control Study of HER2 Genetic Polymorphism and Breast Cancer Risk

The proto-oncogene human epidermal growth factor receptor 2 (HER2) is a transmembrane glycoprotein with tyrosine kinase activity and, among other functions, controls cellular proliferation. Overexpression of HER2 has been observed in many solid tumors, including 20%–30% of breast cancers (1) and 19%–59.4% of epithelial ovarian cancers (2), and is a predictive marker for response in breast cancer (3,4). A valine-to-isoleucine polymorphism at codon 655 (ValIle) (5) was reported in the Journal (6) to be associated with an increased risk of breast cancer among a Chinese population. Subsequently, Ameyaw et al. (7) reported in the Journal that the distribution of the polymorphism varied considerably between ethnic groups, with the valine allele being detected in 20% of Caucasians but absent from an African population. They raised the possibility that any influence of the valine allele on cancer susceptibility may vary considerably between different ethnic populations. We investigated the frequency of the HER2 ValIle polymorphism in a British-based case–control study. Patients with breast cancer (n 315) were selected who had an age at disease onset of under 40 years, a family history of breast cancer irrespective of age at onset, or bilateral breast cancer irrespective of family history of breast cancer or age at onset. Women with incident cases of ovarian carcinoma (n 314) were ascertained from those undergoing primary surgery for the disease in hospitals in southeast England from 1993 through 1998. Control subjects (n 256) were all white female volunteers who either were staff members at the Princess Anne Hospital (n 125) or were patients at the Princess Anne Hospital being treated for non-neoplastic disease conditions (n 131). The mean age of the women in the breast cancer, ovarian cancer, and control groups were 38, 62, and 39 years, respectively. The ValIle polymorphism was analyzed by use of an allele-specific polymerase chain reaction (PCR). The PCR used red and green fluorescently labeled forward primers (5 -CAGCCCTCTGACGTCCATCG-3 and 5 -CAGCCCTCTGACGTCCATCA3 ) and a common reverse primer (5 TGCGGAGACTGCTGCAGGAAACGGA-3 ). The alleles were separated by electrophoresis through 6% denaturing polyacrylamide gels and analyzed with a scanning laser fluorescence imager. Genotyping was confirmed for 100 patients with a PCR and restriction fragment length polymorphism assay described previously (5). The frequency of the valine allele was similar to that reported by Ameyaw et al. (7), and the genotype frequencies among the cancer and control groups were not statistically significantly different from those expected from Hardy–Weinberg equilibrium. We did not observe any statistically significant differences in the valine allele frequency or in the genotype distribution in the cancer groups compared with the control group (Table 1). When the ovarian cancers were stratified according to histologic subtype, stage, and grade, no statistically significant differences were observed (data not shown). We conclude that the HER2 valine allele does not represent a breast or ovarian cancer risk allele, at least in a British population. The association of the valine allele with breast cancer risk reported by Xie et al. (6) was strongest among women diagnosed with breast cancer under 45 years of age. We studied predominantly patients with early-onset breast cancer (mean age 38 years), so that a difference in the age distribution is unlikely to offer an explanation for the discrepancy. Whether the association reported by Xie et al. reflects a true ethnic variation in the penetrance of the valine allele or a type I statistical error warrants further investigation.

Genetic predisposition to Helicobacter pylori-induced gastric precancerous conditions.

Gastric cancer is the most common malignancy of the gastrointestinal tract in East Asian populations and the second most frequent cause of cancer-related mortality in the world. While previous studies have investigated the genetic factors involved in gastric carcinogenesis, there still exist relatively few studies that have investigated the genetic traits associated with the risk of gastric precancerous conditions. In this paper we will review the biology and genetic polymorphisms involved in the genesis of gastric precancerous conditions reported to date and discuss the future prospects of this field of study. The associations of gastric precancerous conditions with polymorphisms in the cytotoxin-associated gene A-related genes (e.g. PTPN11 G/A at intron 3, rs2301756), those in the genes involved in host immunity against Helicobacter pylori (H. pylori) infection (e.g. TLR4 +3725G/C, rs11536889) or polymorphisms of the genes essential for the development/ differentiation of the gastric epithelial cells (e.g. RUNX3 T/A polymorphism at intron 3, rs760805) have been reported to date. Genetic epidemiological studies of the associations between H. pylori-induced gastric precancerous conditions and other gene polymorphisms in these pathways as well as polymorphisms of the genes involved in other pathways like oxidative DNA damage repair pathways would provide useful evidence for the individualized prevention of these H. pylori-induced gastric precancerous conditions.

Tumor Intrinsic Subtype Is Reflected in Cancer-Adjacent Tissue

Introduction: Overall survival of early-stage breast cancer patients is similar for those who undergo breast-conserving therapy (BCT) and mastectomy; however, 10% to 15% of women undergoing BCT suffer ipsilateral breast tumor recurrence. The risk of recurrence may vary with breast cancer subtype. Understanding the gene expression of the cancer-adjacent tissue and the stromal response to specific tumor subtypes is important for developing clinical strategies to reduce recurrence risk. Methods: We utilized two independent datasets to study gene expression data in cancer-adjacent tissue from invasive breast cancer patients. Complementary in vitro cocultures were used to study cell–cell communication between fibroblasts and specific breast cancer subtypes. Results: Our results suggest that intrinsic tumor subtypes are reflected in histologically normal cancer-adjacent tissue. Gene expression of cancer-adjacent tissues shows that triple-negative (Claudin-low or basal-like) tumors exhibit increased expression of genes involved in inflammation and immune response. Although such changes could reflect distinct immune populations present in the microenvironment, altered immune response gene expression was also observed in cocultures in the absence of immune cell infiltrates, emphasizing that these inflammatory mediators are secreted by breast-specific cells. In addition, although triple-negative breast cancers are associated with upregulated immune response genes, luminal breast cancers are more commonly associated with estrogen-response pathways in adjacent tissues. Conclusions: Specific characteristics of breast cancers are reflected in the surrounding histologically normal tissue. This commonality between tumor and cancer-adjacent tissue may underlie second primaries and local recurrences. Impact: Biomarkers derived from cancer-adjacent tissue may be helpful in defining personalized surgical strategies or in predicting recurrence risk. Cancer Epidemiol Biomarkers Prev; 24(2); 406–14. ©2014 AACR.

No associations of Toll-like receptor 2 (TLR2) -196 to -174del polymorphism with the risk of Helicobacter pylori seropositivity, gastric atrophy, and gastric cancer in Japanese

BackgroundRecently, the association between gastric cancer risk and a functional polymorphism of Toll-like receptor 2 (TLR2), -196 to -174del, was reported for a Japanese population. This study aimed to confirm the associations of the polymorphism with the risk of gastric cancer, as well as Helicobacter pylori seropositivity and the risk of gastric atrophy in Japanese.MethodsThe study subjects were 583 histologically diagnosed gastric cancer patients and 1636 age- and sex-frequencymatched control outpatients who visited Aichi Cancer Center Hospital from the years 2001 to 2005. Serum anti-H. pylori IgG antibody and pepsinogens were measured to evaluate H. pylori infection and gastric atrophy, respectively. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by a logistic model.ResultsThe age- and sex-adjusted ORs of gastric cancer were 1.13 (95% CI: 0.88–1.46) for ins/del, 1.17 (95% CI: 0.79–1.73) for del/del, and 1.14 (95% CI: 0.89–1.45) for ins/del + del/del, relative to the ins/ins genotype compared with gastric atrophy controls; none of these findings were statistically significant. The TLR2 -196 to 174del polymorphism was not significantly associated with either H. pylori seropositivity or gastric atrophy.ConclusionOur study did not reproduce the association between gastric cancer risk and the TLR2 -196 to -174del polymorphism in Japanese. Further examinations with sufficient numbers of study subjects are required to verify our findings.