Abstract P3-08-10: A unique coding and non-coding benign breast transcriptome in post-menopausal ER+ breast cancer
Authors: Carter JM , Nair AA , Davila JI , Heinzen EP , Hoskin TL , Winham SJ , Radisky DC , Visscher DW , Degnim AC 
Published: May 2019

Background: Differences in ER+ and ER- breast cancer tumor biology are well-documented, but little is known about the field of background benign breast in which those cancers arise. We evaluated the transcriptome of benign breast tissues from women with concurrent ipsilateral ER+ and ER- breast cancers (BC) to characterize coding and non-coding RNA profiles. This pilot study provides insight into the transcriptomic landscapes of benign breast tissues in patients with BC, and the microenvironment of the at-risk benign tissue.

Methods: With institutional approval, cryobanked breast tissues from patients with concurrent ipsilateral ER+ BC (benign ER+BC, N=14) or ER- BC (benign ER-BC, N=10), were selected for benign tissues with similar epithelial:stromal ratios and grouped into pre (preM) and post-menopausal (PM) groups. Following RNA sequencing (Illumina TruSeq Stranded mRNA kit & Illumina HiSeq 4000), reads were processed (MAP-RSeq v3.0.0) and aligned (STAR aligner; hg38). Differential expression (DE) analysis (edgeR 2.6.2) identified DE genes from normalized RPKM reads (absolute log2 fold change (FC) &gt; 1 and false discovery rate (FDR) &lt; 0.10), corrected for intra-group biases. Over-representation analysis [Ingenuity pathway analysis (IPA), Ingenuity® Systems] and gene set enrichment analysis [(GSEA), GeneTrail 2.0] identified significantly-enriched pathways.

Results: In the PM group, there were 144 DE transcripts between benign ER+BC and benign ER-BC, including coding RNAs (40%), antisense RNAs (35%) and lncRNAs (7%). In contrast, the preM group had no significantly DE genes between benign ER+BC and benign ER-BC. In the PM DE coding gene set, the top DE transcripts in benign ER+BC included many genes implicated in BC development# or ER+ BC progression (*) (e.g. up-regulated: KAAG1*, DNAJB7/HSP40*, TMEM151B, ZBTB32# p &lt; 0.001 ; down-regulated: CPB1*, FOS, TPPP3#, CLEC3B#p &lt; 0.001). Top canonical pathways altered in benign ER+BC included MAPK, PI3K, and acute phase response pathways (p&lt;0.05). GSEA of the entire gene set (N=15,223; ranked in order of 144 DE genes) identified 72 altered pathways (P &lt; 0.005); those with the highest normalization enrichment scores (NES) (&gt; 0.4) functionally grouped as immune function-related (T cell function and antigen presentation). Depleted pathways with NES &gt; 0.4, (N=6) functionally grouped into proteasome-related, fatty acid biosynthesis and mitochondrial energy metabolism. Among the non-coding DE gene set, notably, the entire DE antisense RNA gene set (N=51 transcripts) was up-regulated in benign ER+ BC compared to benign ER-BC (P&lt; 0.001) with a subset (N=11) showing marked up-regulation (&gt; 4 log2FC). Among the DE antisense RNAs, 70% have reported roles in carcinogenesis or BC progression (e.g. KRT7-AS, NAV2-AS2, CCDC144NL-AS1, RP11-66B24.4, HSA-MIR4454).

Conclusion: The benign breast transcriptome differs between postmenopausal women with ER+ vs ER- BC, with distinctive coding and non-coding RNA signatures. In postmenopausal women with ER+ BC, benign breast expresses a unique antisense RNA set and is enriched in genes implicated in BC development or progression. These data provide insight into at-risk benign breast and facilitate identification of potential biomarkers of carcinogenesis.

Citation Format: Carter JM, Nair AA, Davila JI, Heinzen EP, Hoskin TL, Winham SJ, Radisky DC, Visscher DW, Degnim AC. A unique coding and non-coding benign breast transcriptome in post-menopausal ER+ breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-08-10.