Poster abstracts

Poster number 68 submitted by Julie Wallace

Gene Expression Analysis of Cellular Compartments in the Mammary Gland Microenvironment

Julie Wallace (Comprehensive Cancer Center), Anthony Trimboli (Comprehensive Cancer Center), Anand Merchant (Comprehensive Cancer Center), Parul Gulati (Department of Biostatistics), Lianbo Yu (Department of Biostatistics), Gustavo Leone (Comprehensive Cancer Center)

Abstract:
Objectives of the Study: PTEN is a well known tumor suppressor that has been shown to negatively regulate phosphorylation of the cell survival kinase Akt. Germline PTEN mutations in humans are associated with Cowden’s syndrome, in which patients have an increased risk of developing certain cancers, including breast cancer. Previous work in our laboratory using conditional mouse knockouts has shown that specific deletion of Pten in fibroblasts results in higher tumor incidence and tumor burden in the well characterized ErbB2 breast cancer model. We hypothesized that genetic manipulation of Pten specifically in fibroblasts would also lead to gene expression changes in the various surrounding cell compartments, including not only macrophages but also epithelial and endothelial cells, irrespective of the presence of oncogene.
Methodology: PTEN deletion in fibroblasts was achieved using a conditional Pten allele and Cre recombinase under the FSP1 promoter (fibroblast specific promoter 1). Mammary glands from our genetic groups of interest were harvested around 9 weeks, and four different cell types were extracted. RNA was extracted from all samples and submitted for microarray using exon chips. Both LIMMA and EBarrays statistical methods were used to extract differentially expressed genes from the raw data.
Results & Conclusions: Initial results indicate high quality data with four distinct expression sets corresponding to each different cell compartment. Gene ontology analysis on individual cell types showed biological processes correlated with previously observed in vivo data. Independently isolated samples have been used to confirm the differential expression of genes from the microarray. Bioinformatic analysis revealed connected signaling pathways between macrophage and fibroblast samples, indicating crosstalk between these cells. Additional examination of genes found to be differentially regulated in macrophages revealed several cytokines implicated in the M2 macrophage phenotype. Co-culture and other in vitro assays are currently ongoing to further dissect communication between these various cell types.
Significance: Understanding the signaling between a tumor and its microenvironment may have important implications in cancer therapeutics.

Keywords: Pten, Microenvironment