Giovanna Cruz

What can we Learn about Disease Etiology from Case-Case Analyses? Lessons from Breast Cancer

In this commentary, we discuss the challenges and opportunities for epidemiologic studies in evaluating breast cancer as a set of discrete diseases. We show examples of the strengths of the case-only design in assessing the relative correlation of established risk factors and the different cancer

Abstract A65: RNF8: The molecular modulator of breast cancer aggressiveness

Background: Women of Mexican and African-American descent have a higher mortality and a higher proportion of triple negative or basal-like breast cancer with BRCA like features. Basal-like breast cancer subtype is associated with an elevated Ki67 index and extensive genomic instability. This increase in the Ki67 index indicates cell proliferation and perhaps greater DNA damage; double strand breaks are the most consequential DNA lesions. Knockdown of RING-finger 8 (RNF8), an E3 ubiquitin-protein ligase, by siRNA inhibit focus formation at double strand breaks sites suggesting that RNF8 is an important regulator of the DNA repair system. We are investigating the hypothesis that RNF8 is a modulator of genomic integrity by acting as a regulator of BRCA1 and 53BP1 proteins in human breast cancers. Methods: We compared RNF8, p53 binding protein 1 (53BP1), cyclin B1 (CB1) and Ki67 mRNA expression in 57 formalin fixed paraffin embedded human breast cancer taken from a population of Mexican women enriched for basal-like tumors. Further we investigated copy number alterations in the 6p21.2 chromosomal region that contains RNF8 in a subset of 971 early stage breast cancers categorized by tumor subtype considering race/ethnicity. Results:RNF8 and 53BP1 were found to exhibit variable expression at the mRNA level by Ki67 and CB1 expression levels. The combined effect RNF8 high/53BP1 low was associated with high expression of Ki67 (p=0.028). Conversely, RNF8 low expression was associated with low expression of Ki67 (p = 0.017), low CB1 (p = 0.035) and was independent of the 53BP1 expression. In a sample set of 971 stage I/II breast cancers, copy number gain at 6p21.3 (RNF8 locus) was positively associated with triple negative breast cancer (p Different groups have established that RNF8 is recruited to DNA damaged sites and subsequently mediates DNA repair by accumulation of BRCA1 and 53BP1 at DNA lesions. Recently, two groups have independently determined, in a BRCA deficient environment, that chromosomal instability is promoted in the presence of 53BP1. Additionally, it was shown that 53BP1 depletion can restore the DNA repair functions. In this report, we demonstrate differential expression of RNF8 and 53BP1 in a series of human breast cancers and an association between RNF8/53BP1 levels, proliferation, and tumor subtype. Our findings suggest that some breast tumors present an altered DNA repair pathway resulting in activation of RNF8 and de-regulation of 53BP1, which we hypothesize, may contribute to genomic instability and more proliferative tumors. Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):A65.

Abstract A80: Parity and obesity in Mexican and Mexican-American women: Findings from the Ella Binational Breast Cancer Study

Background: Obesity rates are increasing rapidly around the globe. Obesity is associated with negative health consequences including increased risk of all-cause mortality and increased breast cancer morbidity. In the U.S., some of the highest rates of obesity are found among Hispanic women. Additionally, factors associated with low socioeconomic status have also been shown to be positively associated with obesity in the U.S., independent of race or ethnicity; higher parity (i.e., three or more full-term births) has also been implicated as a contributing factor. The aim of this study was to evaluate the independent contribution of parity on obesity in a highly parous population of Mexican and Mexican-American women diagnosed with breast cancer. Methods: Participants are from the Ella Binational Breast Cancer Study, a study of women of Mexican descent who were 18 years of age and older at time of enrollment and who were diagnosed with invasive breast cancer within 24 months of recruitment. Each participant completed an interviewer-administered risk factor questionnaire, provided a blood or saliva sample, and consented to provide tumor tissue and access to medical record data. Obesity was defined as having a body mass index (BMI) ≥30 kg/m2, which was calculated from self-reported height and weight. Parity was defined as the number of full-term live births. Age at interview, age at first full-term pregnancy, level of education, employment, smoking status, menopausal status, age at menarche, and breastfeeding were assessed as potential confounding factors. Among U.S. participants, level of acculturation, interview language and nativity were also evaluated as confounders. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using multinomial logistic regression. Results: Mean age was higher for U.S. compared to Mexican participants (54.4 ± 12.6 vs. 50.1 ± 12.0). Approximately 51% (n=608) of participants resided in Mexico and 49% (n=579) in the U.S. Among U.S. participants, 54% were born in Mexico and of these, 42% have lived in the U.S. Conclusions: Our results show a significant, positive association between parity and obesity that was not independent of education. Results of our work suggest that both pre and postnatal periods are important adult life periods for health care providers to implement obesity prevention strategies and interventions. Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):A80.

Abstract 2806: Factors that influence screening mammography among African American and Mexican American women with breast cancer: Findings from the ELLA Binational Breast Cancer Study

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Screening mammography is associated with early detection of breast cancer (BC) and reduced BC mortality. To understand factors that influence screening mammography receipt in minority women with unrecognized risk factors for BC, this study examined BC screening behaviors among women with BC. Due to the BC survival disparities observed in African American (AA) and Mexican American (MA) women compared to whites, AA and MA women living in Texas and Arizona who were participants of the ELLA Binational Breast Cancer Study were selected for this study based on a diagnosis of BC. Data on socioeconomic status (SES), reproductive history, family history, insurance status, acculturation, and breast health history were collected via questionnaires and medical record abstraction. 601 women aged 40 years or older at time of BC diagnosis were included in this study, including 270 AA, 151 MA women classified as high-acculturation (MA-HA) and 180 MA women classified as low-acculturation (MA-LA). Logistic regression analysis was used to assess differences in mammography receipt in the last five years prior to BC diagnosis stratified by race/ethnicity and acculturation and for all groups combined. MA women in this study suffer a larger disparity than AA women with regards to screening mammography. Despite high rates of screening mammography among AA and MA women, 62% of BC was self-detected in the study population. AA women (OR=1.0) and MA-HA (OR=0.91; 95% CI: 0.57-1.48) women were more than twice as likely to receive screening mammography compared to MA-LA (OR=0.38; 95% CI: 0.25-0.59), adjusted for age. After adjusting for age, education, and insurance, there was no significant difference in screening mammography receipt between these three groups. Women who had a known family history of BC were more than twice as likely to receive screening mammography than women who had unknown or no family history (OR=2.02; 95% CI: 1.19-3.55). However, although AA and MA-HA women were twice as likely as MA-LA to report a family history of BC (20% vs. 23% vs. 12%, respectively), recognized family history did not account for the differences in screening mammography use between these groups. Thus, the differences observed in screening mammography receipt by race/ethnicity and acculturation among AA, MA-HA, and MA-LA are likely explained by SES variables, including education and insurance. Due to the large proportion of AA and MA women who reported self-detecting their BC, women must be educated about the importance of breast awareness and prompt reporting of findings to a health professional after noticing breast changes. In addition, cancer screening programs targeting underserved women should provide culturally appropriate messages about the importance of knowing their family history and the benefits of screening mammography. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2806.

Abstract PR-5: Risk factor distribution among women of Mexican descent by level of acculturation: Findings from the ELLA Binational Breast Cancer Study

Purpose of Study: Studies have shown that breast cancer (BC) risk is higher in U.S.-born Hispanics than foreign-born Hispanics and is modified by age at migration, duration of residence in the U.S., and level of acculturation. Furthermore, epidemiological data support the notion of distinct reproductive factor associations for specific BC tumor subtypes. The aim of this study is to assess the association between established BC risk factors and level of acculturation and country of residence among Mexican American (MA) and Mexican BC cases. Experimental Procedures: This case-only study examined the risk factor profile in 606 Mexican and 488 MA (20% US-born and 80% foreign-born) women, with a confirmed diagnosis of invasive BC, who were recruited into the ELLA Binational Breast Cancer Study between March 1,2007, and May 31,2010. Participants completed an interviewer-administered risk factor questionnaire, consented to a medical record review, and provided tissue and saliva or blood specimens. An eight-item language-based Bidimensional Acculturation Scale (BAS) was used to classify MA women as English-dominant (n=88), bilingual (n=221), or Spanish-dominant (n=179). The BAS is highly correlated with nativity and time in the US, however language use/exposure was focal for this study since it is the single strongest predictor of acculturation. Chi-square tests, ANOVA, and regression models to test for trend were used to assess variation in the risk factor profile by level of acculturation. Summary of Results: Age at diagnosis was generally low; the lowest was among MA-bilingual women (48.9 = 12.0 years) and highest among Mexican women (53.7 = 12.7 years). Considering a gradient of increasing acculturation from Mexican (lowest) to MA-English dominant (highest) women, there were clear trends for decreasing rates of breastfeeding (80.2 to 35.2%; p-trend Conclusion: Our results show that heterogeneity in BC risk factor patterns by level of acculturation is present. Given the recent data supporting distinct correlations between specific risk factors and BC subtypes, it will be essential to consider level of acculturation and country of residence when assessing the prevalence of these subtypes. The trends observed in risk factor profiles by level of acculturation in the ELLA Study could provide important explanations for differences in disease patterns between groups. Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):PR-5.

Abstract A89: HER2-overexpressing tumors and time since last pregnancy

Background: Risk of dying from breast cancer is higher among Hispanic women compared to non-Hispanic whites (NHW) despite lower overall incidence rates and a more favorable risk factor profile. Part of the observed disparity can be explained by aggressive tumor biology although unequal access to care is also a key factor. A recent pooled case-only study suggests Hispanic women are more likely to be diagnosed with HER2-positive tumors compared to NHWs. Given the high parity rates among Hispanics and recent interest in the differential effect of reproductive factors on breast tumor subtypes, we investigated the relative correlation between reproductive factors and tumor phenotype stratified on HER2 status. Methods: A total of 459 women of Mexican origin from the case-only ELLA Binational Breast Cancer Study were classified into hormone receptor (HR) positive cases (estrogen or progesterone-receptor positive, HER2-negative) and HER2-overexpressing cases (HER2+, HR-). Women negative for all three markers (triple negative) were not considered in these analyses. Reproductive factors considered in the analysis include age at first full-term pregnancy, total number of full-term pregnancies, ever breastfeeding, breastfeeding after last pregnancy, and time since last pregnancy. Time to diagnosis since last pregnancy was classified as either ≤10 years or >10 years. We conducted separate analyses for women diagnosed at ≤ 40 years (n=72) and at >40 years of age (n=386). Differences were tested using a Pearson chi-square test or Student9s t-test. We calculated case-case odds ratios (OR) and 95% confidence intervals (CI) using logistic regression to estimate the relative correlation between time since last pregnancy and HER2+ tumors in reference to HR+ tumors. Models included age at diagnosis, recruitment site, age at first pregnancy, number of pregnancies and breastfeeding. Results: Out of 459 women, 338 (74%) were HR+ and 121 (26%) HER2+. No significant differences were observed in the proportion of HR+ tumors among women ≤ 40 and those > 40 (79% vs. 73%, respectively; p=0.22). HER2+ cases were younger at diagnosis compared to HR+ cases (mean age 51.8 vs. 53.1, respectively; p= 0.30). HER2+ cases were more likely to be diagnosed after the age of 40 compared to HR+ cases (OR 4.37; 95% CI: 1.84,10.40) and were more likely to occur within the 10-year period following the last pregnancy (OR=3.99; 95% CI: 1.95,8.16). No difference was observed for age at first full-term pregnancy (OR 0.99; 95% CI: 0.95,1.03), number of full-term pregnancies (OR 0.95; 95% CI: 0.84,1.07) or ever breastfeeding (OR 0.98; 95% CI: 0.59,1.62). A significant interaction was observed between time since last pregnancy and age at diagnosis (p=0.03). Stratified results suggest the relationship between time since last pregnancy and tumor phenotype is stronger in the >40 age group (OR 3.68; 95% CI: 1.60,8.44) compared to those ≤40 (OR 2.68; 95% CI: 0.19,37.16). Conclusions: HER2+ tumors were more likely to be diagnosed in the 10-year period after the last pregnancy compared to HR+ tumors, independent of age. These findings suggest a relationship between HER2+ breast cancer and pregnancy history that differs from that with HR+ tumors, supporting the presence of etiologic heterogeneity in these subtypes. Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):A89.