Yuko Yamamura

Phytoestrogen intake and prostate cancer: a case-control study using a new database.

In the last several years, attention has been focused on comparing the Western diet, which is rich in fat, protein, and refined carbohydrates, with the Asian diet, which is rich in phytoestrogens, as a possible explanation for the contrasting rates of clinically relevant prostate cancer. Phytoestrogens, plant-derived nutrients, include several isoflavones, flavonoids, lignans, phytosterols, and coumestans, some of which have been postulated as having anticarcinogenic properties. Using a new database, we examined the role of phytoestrogen intake and prostate cancer risk in 83 Caucasian cases and 107 controls. Controls reported consuming higher amounts of foods containing genistein, daidzein, and coumestrol and lower amounts of foods containing campesterol and stigmasterol. Multivariate analysis, after adjustment for age, family history of prostate cancer, alcohol consumption, and total calorie intake, showed an inverse association between coumestrol (p = 0.03) and daidzein (p = 0.07) and prostate cancer risk. Genistein, the most studied phytoestrogen, showed a slight protective effect (p = 0.26). However, a positive association was found between campesterol (p = 0.08) and stigmasterol (p = 0.03) and risk of prostate cancer. These results are suggestive of a possible relationship between phytoestrogen intake and prostate cancer risk. Larger comprehensive studies are needed to further refine the role of phytoestrogen intake in prostate cancer risk.

The landscape of recombination in African Americans

Recombination, together with mutation, gives rise to genetic variation in populations. Here we leverage the recent mixture of people of African and European ancestry in the Americas to build a genetic map measuring the probability of crossing over at each position in the genome, based on about 2.1 million crossovers in 30,000 unrelated African Americans. At intervals of more than three megabases it is nearly identical to a map built in Europeans. At finer scales it differs significantly, and we identify about 2,500 recombination hotspots that are active in people of West African ancestry but nearly inactive in Europeans. The probability of a crossover at these hotspots is almost fully controlled by the alleles an individual carries at PRDM9 (P value < 10−245). We identify a 17-base-pair DNA sequence motif that is enriched in these hotspots, and is an excellent match to the predicted binding target of PRDM9 alleles common in West Africans and rare in Europeans. Sites of this motif are predicted to be risk loci for disease-causing genomic rearrangements in individuals carrying these alleles. More generally, this map provides a resource for research in human genetic variation and evolution.

Thyroid hormone and breast carcinoma: Primary hypothyroidism is associated with a reduced incidence of primary breast carcinoma

To investigate the role of primary hypothyroidism (HYPT) on breast carcinogenesis, the authors evaluated 1) the association between HYPT and a diagnosis of invasive breast carcinoma and 2) the clinicopathologic characteristics of breast carcinoma in patients with HYPT.

Genome-wide association study of prostate cancer in men of African ancestry identifies a susceptibility locus at 17q21

In search of common risk alleles for prostate cancer that could contribute to high rates of the disease in men of African ancestry, we conducted a genome-wide association study, with 1,047,986 SNP markers examined in 3,425 African-Americans with prostate cancer (cases) and 3,290 African-American male controls. We followed up the most significant 17 new associations from stage 1 in 1,844 cases and 3,269 controls of African ancestry. We identified a new risk variant on chromosome 17q21 (rs7210100, odds ratio per allele = 1.51, P = 3.4 × 10−13). The frequency of the risk allele is ∼5% in men of African descent, whereas it is rare in other populations (<1%). Further studies are needed to investigate the biological contribution of this allele to prostate cancer risk. These findings emphasize the importance of conducting genome-wide association studies in diverse populations.

Leptin and prostate cancer

Higher prostate cancer mortality rates among US immigrants from countries with lower rates suggest environmental influences on prostate carcinogenesis (e.g., diet, body composition).

Obesity, weight gain, and risk of biochemical failure among prostate cancer patients following prostatectomy.

Purpose: Several lines of evidence suggest that diet and weight gain may be important environmental factors implicated in prostate carcinogenesis, especially in tumor progression. The purpose of this study was to evaluate obesity at different ages in a well-characterized cohort of prostate cancer patients treated with prostatectomy and to develop a prognostic model that incorporates body mass index (BMI) as a measure of obesity. Experimental Design: We carried out a prospective study of 526 patients registered at the M.D. Anderson Cancer Center from 1992 to 2001. Kaplan-Meier and Cox proportional hazard analyses were done. Results: During an average follow-up of 54 months, 97 (18%) post-prostatectomy patients experienced biochemical failure. Patients who were obese (BMI ≥ 30 kg/m2) at diagnosis had a higher rate of biochemical failure than nonobese men (P = 0.07). Those obese at 40 years had an even greater rate of biochemical failure (P = 0.001). Higher BMI at diagnosis [hazard ratio (HR), 1.07; P = 0.01] and Gleason score = 7(4 + 3) and ≥8 (HR, 3.9; P = 0.03 and HR, 10.0; P ≤ 0.001, respectively) remained significant independent predictors of biochemical failure in multivariate analysis. Men who gained weight at the greatest rate (>1.5 kg/y) between 25 years and diagnosis progressed significantly sooner (mean time, 17 months) than those who exhibited a slower weight gain (mean time, 39 months; Ptrend = 0.005). The inclusion of obesity to the clinical nomogram improved performance. Conclusions: Our findings validate the importance for a role of obesity in prostate cancer progression and suggest a link to the biological basis of prostate cancer progression that can be therapeutically exploited.

Genome-wide meta-analyses of smoking behaviors in African Americans

The identification and exploration of genetic loci that influence smoking behaviors have been conducted primarily in populations of the European ancestry. Here we report results of the first genome-wide association study meta-analysis of smoking behavior in African Americans in the Study of Tobacco in Minority Populations Genetics Consortium (n=32 389). We identified one non-coding single-nucleotide polymorphism (SNP; rs2036527[A]) on chromosome 15q25.1 associated with smoking quantity (cigarettes per day), which exceeded genome-wide significance (β=0.040, s.e.=0.007, P=1.84 × 10−8). This variant is present in the 5′-distal enhancer region of the CHRNA5 gene and defines the primary index signal reported in studies of the European ancestry. No other SNP reached genome-wide significance for smoking initiation (SI, ever vs never smoking), age of SI, or smoking cessation (SC, former vs current smoking). Informative associations that approached genome-wide significance included three modestly correlated variants, at 15q25.1 within PSMA4, CHRNA5 and CHRNA3 for smoking quantity, which are associated with a second signal previously reported in studies in European ancestry populations, and a signal represented by three SNPs in the SPOCK2 gene on chr10q22.1. The association at 15q25.1 confirms this region as an important susceptibility locus for smoking quantity in men and women of African ancestry. Larger studies will be needed to validate the suggestive loci that did not reach genome-wide significance and further elucidate the contribution of genetic variation to disparities in cigarette consumption, SC and smoking-attributable disease between African Americans and European Americans.

Characterizing Genetic Risk at Known Prostate Cancer Susceptibility Loci in African Americans

GWAS of prostate cancer have been remarkably successful in revealing common genetic variants and novel biological pathways that are linked with its etiology. A more complete understanding of inherited susceptibility to prostate cancer in the general population will come from continuing such discovery efforts and from testing known risk alleles in diverse racial and ethnic groups. In this large study of prostate cancer in African American men (3,425 prostate cancer cases and 3,290 controls), we tested 49 risk variants located in 28 genomic regions identified through GWAS in men of European and Asian descent, and we replicated associations (at p≤0.05) with roughly half of these markers. Through fine-mapping, we identified nearby markers in many regions that better define associations in African Americans. At 8q24, we found 9 variants (p≤6×10−4) that best capture risk of prostate cancer in African Americans, many of which are more common in men of African than European descent. The markers found to be associated with risk at each locus improved risk modeling in African Americans (per allele OR = 1.17) over the alleles reported in the original GWAS (OR = 1.08). In summary, in this detailed analysis of the prostate cancer risk loci reported from GWAS, we have validated and improved upon markers of risk in some regions that better define the association with prostate cancer in African Americans. Our findings with variants at 8q24 also reinforce the importance of this region as a major risk locus for prostate cancer in men of African ancestry.

p53 Expression as a Prognostic Marker in Inflammatory Breast Cancer

Purpose: Inflammatory breast cancer (IBC) is a rare and aggressive form of breast cancer. Nuclear expression of p53 protein in breast cancer correlates with more aggressive tumors. We retrospectively analyze the expression of p53 as a prognostic marker to predict pathological complete response and survival in patients with IBC. Experimental Design: Fifty-nine patients with IBC were treated from January 1994 to April 2000. Forty-eight patients were included. Diagnostic core biopsies were taken before treatment was started. Expression of hormone receptors and p53 was determined by immunohistochemistry. All patients received an anthracycline-based regimen preoperatively; 22 patients (46%) also received paclitaxel. Forty-four patients (92%) achieved an objective clinical response and underwent mastectomies. Results: Median age at diagnosis was 48 years. Thirty patients (63%) had hormone receptor-negative tumors. Twenty-eight patients (58%) had p53-positive tumors, and 20 patients (42%) had p53-negative tumors. Nine patients (19%) achieved a pathological complete response. At a median follow-up of 77 months, 28 recurrences (58%) and 26 deaths (54%) had occurred. Patients with p53-positive tumors were younger (P = 0.02) and tended to have lower 5-year progression-free survival rates (35% versus 55%; P = 0.3) and overall survival rates (44% versus 54%; P = 0.4). Conclusions: This retrospective analysis demonstrates that nuclear p53 protein expression may represent an adverse prognostic marker in IBC and may provide a valuable tool for selecting treatment for this aggressive disease.

Saturated fat intake predicts biochemical failure after prostatectomy

Previous reports show that obesity predicts biochemical failure after treatment for localized prostate cancer. Since obesity is associated with increased fat consumption, we investigated the role that dietary fat intake plays in modulating obesity‐related risk of biochemical failure. We evaluated the association between saturated fat intake and biochemical failure among 390 men from a previously described prostatectomy cohort. Participants completed a food frequency questionnaire collecting nutrient information for the year prior to diagnosis. Because fat and energy intake are highly correlated, the residual method was used to adjust fat (total and saturated) intakes for energy. Biochemical‐failure‐free‐survival rates were calculated using the Kaplan–Meier method. Crude and adjusted effects were estimated using Cox proportional hazards models. During a mean follow‐up of 70.6 months, 78 men experienced biochemical failure. Men who consumed high‐ saturated fat (HSF) diets were more likely to experience biochemical failure (p = 0.006) and had significantly shorter biochemical‐failure‐free‐survival than men with low saturated fat (LSF) diets (26.6 vs. 44.7 months, respectively, p = 0.002). After adjusting for obesity and clinical variables, HSF‐diet patients were almost twice as likely to experience biochemical failure (hazard ratio = 1.95, p = 0.008) compared to LSF diet patients. Men who were both obese and consumed HSF diets had the shortest biochemical‐failure‐free‐survival (19 months), and nonobese men who consumed LSF diets had the longest biochemical‐failure‐free‐survival (46 months, p < 0.001). Understanding the interplay between modifiable factors, such as diet and obesity, and disease characteristics may lead to the development of behavioral and/or targeted interventions for patients at increased risk of progression.