Long Non-coding RNA C5orf66-AS1 is Downregulated in Pituitary Null Cell Adenomas and is Associated with Their Invasiveness

Pituitary null cell adenoma is a challenging clinical condition, and its pathogenesis remains to be elucidated. We performed this study to determine the roles of C5orf66-AS1, NORAD, and TINCR in the pathogenesis and invasion of pituitary null cell adenomas. Expression of the three long non-coding RNAs in pituitary null cell adenoma tissues of 11 patients and normal pituitary tissues from four donors was examined by performing quantitative reverse transcription-polymerase chain reaction. We found that C5orf66-AS1 expression was lower in pituitary null cell adenoma tissues than in normal pituitary tissues. Moreover, C5orf66-AS1 expression level was significantly lower in invasive pituitary null cell adenomas than in non-invasive ones. After transfection of C5orf66-AS1 into pituitary adenoma cells, assessment of cell viability and invasion suggested that overexpressed C5orf66-AS1 inhibited cell viability and cell invasion. In silico algorithms predicted several cis- and trans-acting target genes of C5orf66-AS1, including PITX1 and SCGB3A1. In addition, expression of some of the predicted target genes was determined using microarray data of another cohort with pituitary null cell adenomas. It showed that some of these target genes were differentially expressed between pituitary null cell adenoma tissues and normal pituitary tissues as well as between invasive and non-invasive tumors. Co-expression analysis in RNA sequencing data showed that PAQR7 was the most correlated gene of C5orf66-AS1 and that several predicted trans-acting target genes, including SCGB3A1, were highly correlated with C5orf66-AS1. NORAD and TINCR expression was not statistically significant in the complete cohort; however, a negative correlation was observed between NORAD expression and maximum tumor diameter in some subgroups. These results indicate that C5orf66-AS1 suppresses the development and invasion of pituitary null cell adenomas. However, our results do not provide enough statistical evidence to support the roles of NORAD and TINCR in the development and invasion of pituitary null cell adenomas.