Abstract P5-04-09: Redefining the breast tumor margin through genomics of the tumor-stromal interaction
Authors: Dhage S , Wang J , Zavadil J , Berman R , Axelrod D , Roses D , Schneider R 
Published: August 2014

Objectives: Emerging data suggest that breast tumors enact gene expression changes in the surrounding stroma, facilitating future recurrence, cancer progression/invasion, metastasis, and altering therapeutic response. The extent to which this alteration penetrates the surrounding breast tissue has not been characterized. It is important to understand both the genomics of the tumor and the tissue that remains following surgery. This relationship could ultimately impact treatment decisions for effective surgery and adjuvant therapy based on the biological impact of the tumor on its anatomical surroundings.Methods: 32 patients undergoing mastectomy for invasive cancer from 2009-2012, had 9 tissue samples placed in RNA later: tumor, and stroma every 5 mm to 20 mm in two directions. A pathologist verified that the stroma was devoid of cancer cells. 108 tissues were analyzed for genome-wide mRNA expression by Affymetrix U133A 2+ arrays: 27 tumor, 29 5mm, 21 10mm, 11 15mm, and 20 20mm regions. RNA was purified by RNeasy chromatography (Qiagen) and assayed for integrity and concentration by Agilent Bioanalysis. SVM, ANOVA and PCA were performed to establish gene expression patterns, clustering and FDR in all tumor sets.Results We propose a gene expression profile/ map of the impact of the breast tumor on non-cancer stromal tissue in the breast. SVM analysis showed paired gene significance based on stromal proximity at all distances, which decreased in similarity with radial distance (closer stromal tissue to tumor had fewer differentially expressed genes). Analysis of gene expression patterns, PCA, unsupervised and supervised clustering demonstrate that the 5 mm region are significantly related to tumor gene expression profiles in almost all of the patients.In contrast, stromal tissue at 10mm, 15mm, and 20mm from the tumor-free margin display gene expression profiles that are similar to each other.But, with reduced similarity to tumor and 5mm. In a small number of patients, stroma at 10-15mm also displayed gene expression profiles significantly consistent with a tumor-like signature. Further analysis for the highest ranked 300 transcripts with the lowest FDR scores based on ANOVA are fully shared by the tumor and 5mm regions in over 30% the patients. A genomic signature is emerging that occurs in the stroma in both the tumor like and non-tumor like regions. Conclusion: These results show that breast tissue devoid of tumor cells is genomically highly related to the tumor at the 5mm, and even from regions 10, 15, and 20mm beyond cancer-free margins in some patients,, corresponding to regions considered histologically “normal”. We suggest that in a subset of patients, cancer-free stromal tissue is highly similar to the tumor. This implicates tumor imprinting as a means of genetically altering stromal tissues in a manner that is consistent with a potential for increased recurrence and de novo cancer development. In order to improve the effectiveness of breast cancer therapy, further determination of tumor/stromal interaction (determining optimal disease free tissue based on genomics and tumor promoting tissue), could directly impact both surgical and disease outcomes.Fig 1. Heatmap-Gene Expression in tumor&5mm are similar, but different from 10, 15, 20.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-04-09.