Abstract C16: Feasibility study: Protein profiling of primary breast cancers from premenopausal women
Authors: Drendall Catherine Ibarra , Barry William , Ramos Corinne , Tolbert Nora , Geradts Joseph , Petricoin Emanuel , Seewaldt Victoria 
Published: May 2015

African American women are more likely to be diagnosed with aggressive breast cancer at a younger age, have a higher risk of death, and have a higher prevalence of obesity than their Caucasian counterparts. Moreover, African American (AA) women diagnosed with triple-negative breast cancer have the lowest survival rates of all racial/ethnic groups. Although these disparities have been attributed to differences in biology, family and reproductive history, mammographic breast density, body mass index, access to healthcare, diet and environment, more etiologic studies are needed to elucidate the complex association between race, biologic factors, and socioeconomic factors.

In the present study, we tested the feasibility of using high-throughput reverse phase protein microarray to identify protein(s) that are differentially expressed in the primary invasive breast cancers of premenopausal Caucasian and African American women. We examined the expression of 60 phosphorylated, total, and cleaved proteins in microdissected epithelial cells from 26 pre-treatment primary breast cancers. The impact of obesity on protein expression was also considered by stratifying samples into non-obese and obese based on a body mass index (BMI). Samples that come from women with BMI &lt; 30 kg/m2 are classified as non-obese, while those with BMI ≥ 30 kg/m2 are considered obese. All statistical analyses were done using SAS Enterprise Guide 5.1 (SAS Institute, Cary, NC). For comparison of 2 groups, t tests were used for continuous variables and Fisher exact tests for categorical variables. ANOVA was used for comparison of more than 2 groups. Two-tailed p-value &lt; 0.05 was considered statistically significant. Unsupervised hierarchical clustering analysis was performed on log 2-transformed values for each protein endpoint, using average linkage of the Pearson correlation coefficient.

In this exploratory study, 58% of the primary breast cancers come from Caucasian women, while 42% of the samples come from AA women. The mean age and BMI for the two groups of women did not differ significantly. While the majority of the samples were of luminal subtypes, the triple-negative breast cancers were represented in majority of AA women. The expression of MEK1/2 S217/S221, PKC pan beta S660, and total PTEN were significantly higher in Caucasian women. When the impact of breast cancer subtypes (triple-negative vs. luminal A) on protein expression was examined, only total PTEN was statistically significant. Given the role of obesity in breast cancer, we determined which proteins are differentially expressed in non-obese and obese samples. Few components of the insulin and insulin-like growth factor and inflammatory signaling pathways (e.g. PTEN, acetyl CoA carboxylase, PKC pan beta S660, Stat3) were highly expressed in samples of obese women. This preliminary data demonstrates (a) the feasibility of mapping cell signaling networks in limited number of pre-treatment samples from premenopausal women and (b) the potential of future proteomic and larger cohort studies to identify which women will likely benefit from combination of targeted agents.

Citation Format: Catherine Ibarra Drendall, William Barry, Corinne Ramos, Nora Tolbert, Joseph Geradts, Emanuel Petricoin, Victoria Seewaldt. Feasibility study: Protein profiling of primary breast cancers from premenopausal women. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C16. doi:10.1158/1538-7755.DISP13-C16