Extraction of DNA and RNA from Breast Tissue

DNA and total RNA were extracted from fresh frozen non-neoplastic breast tissue samples from cohort-2 using the Allprep kit DNA/RNA/miRNA (Qiagen no. 80224). Nucleic acids were not isolated from normal tissue samples from cohort-1 as only a handful of samples exist. Since normal breast tissue is enriched in fatty tissue and stromal cells, as compared to the tumor, a section of normal breast tissue was stained with eosin and hematoxylin, before extraction, to ensure the presence of normal epithelial breast cells in the specimen. Thirty-five samples were chosen for continuation based on the presence of normal breast tissue, RNA quantity and RIN (RNA integrity number) value. DNA and total RNA was extracted from cohort-2 by the same method used for normal breast tissue [18 (link)], but total RNA from cohort-1 was extracted with Trizol, as described [19 (link)].