lncRNA–mRNA Expression Patterns in Invasive Pituitary Adenomas: A Microarray Analysis

Differential expression of cancer-related lncRNAs in different subtypes of pituitary adenomas

Recent investigations have demonstrated abnormal expression of non-coding RNAs in pituitary adenomas. Cntribution of many lncRNAs to the pathogenesis of these tumors has not been evaluated yet. HOTTIP, ANRIL, PANDAR, PCGEM1 and HOTAIR are among lncRNAs with established roles in the pathogenesis of human cancers, particularly those originated from endocrine organs. The current study aims at assessment of expression of these lncRNAs in pituitary adenomas in comparison with the adjacent non-cancerous pituitary tissues. HOTAIR expression was absent from the majority of adenoma and non-tumoral samples. Expression of HOTTIP was significantly higher in non-functioning pituitary adenoma (NFPA) samples compared with paired normal samples (expression ratio (95 % CI)= 2.1 (1.13-2.1), P value=0.03). Expression of PANDAR was higher in total adenoma samples compared with paired normal samples (expression ratio (95 % CI)= 1.91 (1.16-3.13), P value=0.02). Expression of ANRIL was higher in NFPA samples compared with paired normal samples (expression ratio (95 % CI)= 1.94 (1.05-3.6), P value=0.048) and in total adenoma samples compared with paired normal samples (expression ratio (95 % CI)= 1.82 (1.11-2.98), P value=0.025). The current study raises the possibility of contribution of lncRNAs in the pathogenesis of at least some subtypes of pituitary adenomas and warrant further functional studies in this field.

Regulation of long noncoding RNAs in the pathogenesis and clinical implications of pituitary adenomas

BACKGROUND

Pituitary adenoma (PA) is a type of tumor that develops in the sella turcica and is one of the most frequent intracranial tumors. It belongs to a type of adenoma derived from a single clone of cells in the pituitary gland. PA ranks third among all intracranial tumors, following only gliomas and meningioma. The average prevalence rate is approximately 15% at autopsy and 22.5% at radiological examinations.

OBJECTIVE AND SIGNIFICANCE

Most PAs are benign and non-invasive adenomas that can be removed surgically or controlled with medication. However, approximately 35% of them show invasion into nearby anatomical structures and cannot be completely resected. 0.1%~0.2% of PA cases eventually develop into pituitary carcinomas. Additionally, PA may cause severe morbidity due to mass effects and the disorder of pituitary hormone secretion. Therefore, there is an urgent need to clarify the pathological mechanism of PA, improve the accuracy of diagnosis, and develop targeted therapies.

RESEARCH STATUS

Although current knowledge about the pathogenesis of PA remains limited, epigenetic modulation of PA has been increasingly implicated. Long non-coding RNAs (lncRNAs) are known to regulate gene expression post-transcriptionally and exert substantial roles in the initiation, progression, or suppression of various tumors. Accumulating evidence has shown close relationships between lncRNA dysregulation and PA development.

CONCLUSIONS

This review highlights recent progress in the study of lncRNAs in PA pathogenesis and their potential as diagnostic/prognostic biomarkers or therapeutic targets for PA patients.

Dysregulation of PVT1 and NEAT1 lncRNAs in pituitary adenomas

Pituitary adenomas are slow-growing tumors originated from the anterior part of pituitary gland. These tumors are associated with dysregulation of a number of long non-coding RNAs (lncRNAs). PVT1, TUG1, MALAT1, NEAT1 and GAS5 are among lncRNAs with important roles in the regulation of cell proliferation, cell apoptosis, cell differentiation and cell cycle transition. In the current study, we assessed expression levels of PVT1, TUG1, MALAT1, NEAT1 and GAS5 in the pituitary adenoma samples compared with adjacent non-cancerous samples to find their relevance with this type of tumors and their potential as diagnostic markers in these tumors. Expression of NEAT1 was significantly higher in total adenoma tissues (Expression ratio (95% CI)= 7.06 (2.31-21.4), P value= 0.02) and in non-functioning pituitary adenoma (NFPA) samples (Expression ratio (95% CI)= 8.5 (2.17-33.12), P value= 0.04) compared with corresponding controls. Although both lncRNAs had appropriate sensitivity values for discrimination of NFPAs from adjacent non-cancerous tissues (0.84 and 0.90 for PVT1 and NEAT1, respectively), the calculated AUC values were not adequate for either lncRNAs (0.63 ± 0.04 and 0.58 ± 0.04 for PVT1 and NEAT1, respectively). Therefore, NEAT1 and PVT1 lncRNAs are dysregulated in NFPA. The current study suggests the role of NEAT1 and PVT1 in the pathogenesis of NFPA.

Emerging Roles of miRNA, lncRNA, circRNA, and Their Cross-Talk in Pituitary Adenoma

Pituitary adenoma (PA) is a common intracranial tumor without specific biomarkers for diagnosis and treatment. Non-coding RNAs (ncRNAs), including microRNAs (miRNA), long non-coding RNA (lncRNA), and circular RNA (circRNA), regulate a variety of cellular processes, such as cell proliferation, differentiation, and apoptosis. Increasing studies have shown that the dysregulation of ncRNAs, especially the cross-talk between lncRNA/circRNA and miRNA, is related to the pathogenesis, diagnosis, and prognosis of PA. Therefore, ncRNAs can be considered as promising biomarkers for PA. In this review, we summarize the roles of ncRNAs from different specimens (i.e., tissues, biofluids, cells, and exosomes) in multiple subtypes of PA and highlight important advances in understanding the contribution of the cross-talk between ncRNAs (e.g., competing endogenous RNAs) to PA disease.