Abstract A66: Comprehensive gene expression analysis of ductal carcinoma in situ (DCIS) progression to invasive breast cancer reveals potential biomarkers

The big challenge in breast cancer is to discriminate which patients with non-invasive disease would benefit from minimal clinical interventions from those who require a more traditional treatment approach, keeping the highest survival rates. Hence, identification of molecular alterations of epithelial cells that take place in earliest stages of ductal carcinoma in situ (DCIS) progression is crucial for understanding the invasion process and for guiding the design of intervention strategies. In order to assess the molecular changes that occur during progression of non-invasive breast cancer we analyzed gene expression of epithelial cells representative of two steps of DCIS progression - before and after invasion manifestation. Thus, for assessing the molecular alterations before invasion manifestation, epithelial cells were captured by laser microdissection from in situ component of both groups of lesions - pure DCIS and in situ component that co-exist with invasive breast carcinoma lesion (DCIS-IBC), and for alterations after invasion manifestation, epithelial cells were captured from in situ and invasive components of the same DCIS-IBC lesion. Their transcriptional profiles were interrogated by three different approaches (cDNA microarray, Rapid Subtraction Hybridization (RaSH) cDNA library and RT-qPCR assay) and gene expression profiles were assessed under a comprehensive manner for detecting differences in gene expression level that may occur in the two steps of progression. The candidate genes identified by the different approaches were selected and evaluated using RT-qPCR by TaqMan assay in novel microdissected samples to increase the significance of our findings. We identified 26 genes, 20 associated with the earlier step of DCIS progression (pure DCIS and in situ component DCIS-IBC) and 6 involved in the later step (in situ and invasive component of DCIS-IBC). The gene set of the earlier step was clearly marked by a preferential down-regulation toward invasion ability. Hierarchical clustering based on expression profile of this gene set was able to discriminate both types of epithelial cells captured from both pre-invasive lesions (pure DCIS and in situ component DCIS-IBC), which display fully distinct malignant potential. By the other side, the expression profile of gene set of the latter step was significantly lower and not able to discriminate the epithelial cells captured from both morphologically different lesions - in situ and invasive components of distinct DCIS-IBC lesions. Integrated analysis of the 26 genes showed an enrichment of gene categories related to cell death and survival, cell signaling, cellular function and maintenance. Altogether, this study reinforced that the molecular changes for DCIS progression occurs before the morphological manifestation of invasion and reveals genes involved in the earliest step of invasion process opening perspectives for tailoring treatment of DCIS patients. Citation Format: Eliana V. Elias, Nadia Pereira de Castro, Paulo H. Baldan Pineda, Carolina Sens Abuazar, Mabel G. Pinilla, Cynthia A. Osorio, Sabrina D. da Silva, Elisa Ferreira e Napolitano, Helena P. Brentani, Dirce M. Carraro. Comprehensive gene expression analysis of ductal carcinoma in situ (DCIS) progression to invasive breast cancer reveals potential biomarkers. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr A66.