MicroRNAs differentially expressed in ACTH-secreting pituitary tumors.

CONTEXT: MicroRNAs (miRNAs) are small noncoding RNAs, functioning as antisense regulators of gene expression by targeting mRNA and contributing to cancer development and progression. More than 50% of miRNA genes are located in cancer-associated genomic regions or in fragile sites of the genome. OBJECTIVE: The aim of the study was to analyze the differential expression of let-7a, miR-15a, miR-16, miR-21, miR-141, miR-143, miR-145, and miR-150 in corticotropinomas and normal pituitary tissue and verify whether their profile of expression correlates with tumor size or remission after treatment. MATERIAL AND METHODS: ACTH-secreting pituitary tumor samples were obtained during transphenoidal surgery from patients with Cushing disease and normal pituitary tissues from autopsies. The relative expression of miRNAs was measured by real-time PCR using RNU44 and RNU49 as endogenous controls. Relative quantification of miRNA expression was calculated using the 2(-DeltaDeltaCt) method. RESULTS: We found underexpression of miR-145 (2.0-fold; P = 0.04), miR-21 (2.4-fold; P = 0.004), miR-141 (2.6-fold; P = 0.02), let-7a (3.3-fold; P = 0.003), miR-150 (3.8-fold; P = 0.04), miR-15a (4.5-fold; P = 0.03), miR-16 (5.0-fold; P = 0.004), and miR-143 (6.4-fold; P = 0.004) in ACTH-secreting pituitary tumors when compared to normal pituitary tissues. There were no differences between miRNA expression and tumor size as well as miRNA expression and ratio of remission after surgery, except in patients presenting lower miR-141 expression who showed a better chance of remission. CONCLUSION: Our results support the possibility that altered miRNA expression profile might be involved in corticotrophic tumorigenesis. However, the lack of knowledge about miRNA target genes postpones full understanding of the biological functions of down-regulated or up-regulated miRNAs in corticotropinomas.

SAGE analysis highlights the putative role of underexpression of ribosomal proteins in GH-secreting pituitary adenomas.

BACKGROUND: Although the molecular pathogenesis of pituitary adenomas has been assessed by several different techniques, it still remains partially unclear. Ribosomal proteins (RPs) have been recently related to human tumorigenesis, but they have not yet been evaluated in pituitary tumorigenesis. OBJECTIVE: The aim of this study was to introduce serial analysis of gene expression (SAGE), a high-throughput method, in pituitary research in order to compare differential gene expression. METHODS: Two SAGE cDNA libraries were constructed, one using a pool of mRNA obtained from five GH-secreting pituitary tumors and another from three normal pituitaries. Genes differentially expressed between the libraries were further validated by real-time PCR in 22 GH-secreting pituitary tumors and in 15 normal pituitaries. RESULTS: Computer-generated genomic analysis tools identified 13,722 and 14,993 exclusive genes in normal and adenoma libraries respectively. Both shared 6497 genes, 2188 were underexpressed and 4309 overexpressed in tumoral library. In adenoma library, 33 genes encoding RPs were underexpressed. Among these, RPSA, RPS3, RPS14, and RPS29 were validated by real-time PCR. CONCLUSION: We report the first SAGE library from normal pituitary tissue and GH-secreting pituitary tumor, which provide quantitative assessment of cellular transcriptome. We also validated some downregulated genes encoding RPs. Altogether, the present data suggest that the underexpression of the studied RP genes possibly collaborates directly or indirectly with other genes to modify cell cycle arrest, DNA repair, and apoptosis, leading to an environment that might have a putative role in the tumorigenesis, introducing new perspectives for further studies on molecular genesis of somatotrophinomas.

CTNNB1 gene mutations, pituitary transcription factors, and MicroRNA expression involvement in the pathogenesis of adamantinomatous craniopharyngiomas.

Genes involved in formation/development of the adenohypophysis, CTNNB1 gene, and microRNAs might be implicated in the craniopharyngioma pathogenesis. The objective of this study is to perform the molecular analysis of HESX1, PROP1, POU1F1, and CTNNB1 genes and evaluate a panel of miRNA expression in craniopharyngioma. We also verified whether the presence of CTNNB1 mutation is associated with clinical findings and miRNA expression. The study included 16 patients with adamantinomatous craniopharyngioma (nine children and seven adults; eight females and eight males; 6-55 years, median 15.5 years). DNA, RNA, and cDNA were obtained from craniopharyngioma and normal pituitaries. DNA was also extracted from peripheral blood of healthy subjects. All genes were amplified by polymerase chain reaction and direct sequenced. Relative quantification of miRNA expression was calculated using the 2(-ΔΔCt) method. We found no mutations in HESX1, PROP1, and POU1F1 genes and four polymorphisms in PROP1 gene which were in Hardy-Weinberg equilibrium and had similar allelic frequencies in craniopharyngioma and controls. We found seven different mutations in CTNNB1 in eight of 16 patients. Younger patients presented more frequently CTNNB1 mutation than adults. We observed hyperexpression of miR-150 (1.7-fold); no different expression of miR-16-1, miR-21, and miR23a; and an underexpression of miR-141, let-7a, miR-16, miR-449, miR-145, miR-143, miR-23b, miR-15a, and miR-24-2 (ranging from -7.5 to -2.5-fold; p = 0.02) in craniopharyngioma. There was no association between tumor size or the recurrence and the presence of CTNNB1mutations. miR-16 and miR-141 were underexpressed in craniopharyngioma presenting CTNNB1 mutations. miR-23a and miR24-2 were hyperexpressed in patients who underwent only one surgery. Mutations or polymorphisms in pituitary transcription factors are unlikely to contribute to the adamantinomatous craniopharyngioma pathogenesis, differently of CTNNB1 mutations. Our data suggest the potential involvement of the deregulation of miRNA expression in the craniopharyngioma pathogenesis and outcome and also that the miRNA could modulate the Wnt signaling pathway in craniopharyngioma tumorigenesis.

Differential expression of miR-143, miR-145 and miR-150 in colorectal cancer

Background: Recent reports indicated the involvement of microRNAs (miRNAs) deregulation in colorectal adenomatous mucosa and different stages of colorectal cancer (CRC). Aims: The purpose of this study was to analyze a panel of miRNAs previously selected by bioinformatics analysis from SAGE human colorectal cancer library compared to normal colorectal library in order to identify microRNA species with altered expression in colorectal cancer. Methods: We analyzed the expression of let-7a, miR-21, miR-15a, miR-141, miR-143, miR-145 and miR-150 in 15 tumor tissues from patients who undergone surgery for CRC and 4 non-tumor adjacent tissues. The expression of miRNAs was measured by real-time PCR. Relative quantification of miRNA expression was calculated using the 2(-Delta Delta C(T)) method. Results: Our findings showed under expression of miR-143, miR-150 and miR-145 in about 6-fold (p = 0.05), 5-fold and 4-fold (p = 0.01), respectively, in CRC compared to normal colorectal tissue. In addition, there was no association between each miRNA expression and tumor stage or tumor localization. Conclusion: Our results support that under expression of miR-143, miR-150 and miR-145 might be involved in colorectal carcinogenesis. However, the lack of knowledge about miRNA target genes postpones full understanding of the biological functions of downregulated miRNAs in CRC.