Expression analysis of PPAR-related lncRNAs in breast cancer

Breast cancer is a genetically heterogeneous disorder associated with dysregulation of several genes. Peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-dependent transcription factor that is expressed by many tumoral cells such as transformed breast cancer cells. We investigated expressions of nine PPARγ-related lncRNAs, namely KCNIP2-AS1, TRHDE-AS1, FAM13A-AS1, ALDH1A1-AS2, SH3BP5-AS1, HID1-AS1, LINC01140, LIPE-AS1 and ABCA9-AS1 in paired breast cancer samples and non-tumoral tissues. Expression assays showed lower expression levels of TRHDE-AS1, ALDH1L1-AS2, KCNIP2-AS1, ABCA9-AS1, LIPE-AS1 and LINC01140 in tumoral compared with non-tumoral samples. The mentioned genes could differentiate between breast tumors and non-tumoral samples with AUC values ranging from 0.77 to 0.62 for LINC01140 and LIPE-AS1, respectively. The highest specificity and sensitivity values were reported for KCNIP2-AS1 and LINC01140, respectively. Significant correlations were reported between all pairs of genes in both tumoral and non-tumoral tissues. The most robust ones were between ABCA9-AS1 and KCNIP2-AS1 (correlation coefficient=0.85) in non-tumoral tissues and between LIPE-AS1 and TRHDE-AS1 (correlation coefficient=0.83) in tumoral tissues. There was a significant negative association between expression levels of KCNIP2-AS1 gene in tumor tissues and different histological grades. Besides, there was a significant negative association between expression levels of FAM13A-AS1, KCNIP2-AS1and LIPE-AS1 genes in tumor tissues and different mitotic rates. Taken together, PPARγ-related lncRNAs might be regarded as potential contributors to the pathogenesis of breast cancer.