The expression of lncRNAs CASC2, NEAT1, LINC00299 in breast cancer tissues and their relationship with the XBP1 splicing rate in Iranian patients during 2014–2019: A cross‐sectional study

BACKGROUND AND AIMS: Breast cancer is a leading cause of incidence and mortality in women globally. Identifying new molecular markers can aid in cancer diagnosis, targeted therapy, and treatment monitoring. This study aimed to measure the expression of the X‐box binding protein 1 (XBP1) gene, an index of the unfolded protein response (UPR), and long noncoding RNAs (lncRNAs), including Nuclear Enriched Abundant Transcript 1 (NEAT1), Cancer Susceptibility Candidate 2 (CASC2), and Long Intergenic Nonprotein Coding RNA 299 (LINC00299), as possible regulators of the UPR pathway. METHODS: Total RNA was extracted from 40 samples of breast tumor tissues and their respective controls. The expression level of lncRNAs CASC2, NEAT1, and LINC00299 was quantified using reverse transcription‐polymerase chain reaction (RT‐PCR). The ratio of the spliced form of XBP1 to its unspliced form (XBP1u) was determined by PCR and electrophoresis. RESULTS: The results showed a 2.8‐fold increase in the ratio of XBP1s/u in breast cancer tissues compared to adjacent nonmalignant samples (p < 0.05). Additionally, the level of lncRNAs NEAT1, CASC2, and LINC00299 in breast tumor tissues increased significantly by twofold, 1.5‐fold, and 2.3‐fold, respectively, compared to adjacent nonmalignant samples (p < 0.05). CONCLUSIONS: Based on the association between the expression of lncRNAs CASC2, LINC00299, and NEAT1 and the XBP1s/u ratio, these lncRNAs could be potential regulators of the UPR pathway. Also, CASC2 and NEAT1 genes could be suggested as suitable biomarkers to distinguish cancerous tissue from noncancerous breast tissue due to their significant increase in expression in cancerous samples compared to adjacent noncancerous.