Normal tissues adjacent to the tumour (
NAT) are widely used as controls in comparative studies to search for
cancer-associated genes. However, the gene expression profiles between
NAT and non-tumour-bearing tissues are different. The presence of
NAT-specific expressed genes often hinders traditional transcriptional profiles studies. Further, studies on the differences in gene expression profiles between
NAT and tumour-free tissues are infrequently performed. In this study, we sequenced and analysed the transcriptomes of tumour tissues (T), matched
NAT and contralateral breast normal tissues (CBN) of 14
breast cancer patients, and identified 102 differentially expressed genes (DEGs) between CBN and
NAT. Gene enrichment and
protein-
protein interaction (PPI) analyses revealed that these DEGs are significantly enriched in TNF (tumour
necrosis factor) signalling and EMT (epithelial-mesenchymal transition) gene sets closely associated with
oncogenesis. Comparative analyses of the transcriptomic profiles between
NAT and CBN,
NAT and T identified 23
NAT-specific highly-expressed genes, namely tumour-adjacent speci?cally activated (TASA) genes. These genes were significantly enriched in TNF signalling gene set, and 15 of which have not been previously reported. The results indicate that TASA genes are common in adjacent tissues and are related to the TNF signalling in the immune system. The tumour-adjacent tissues harbour tumour-like expressed genes that could contribute to tumour initiation but are often missed in
NAT-T pair-wise studies.