Identification of ENC1 gene specific to invasiveness in pituitary null cell adenomas

Abstract

Objective Non-functioning pituitary adenomas (NFPAs) may be locally invasive.Surgery is a treatment option,but unlike the case for functional pituitary adenomas,there are almost no drug treatments available for NFPAs.To identify the relationship of ENC1 gene with invasiveness in NFPAs and to observe whether the ENC1 expression level was different between invasive null cell adenomas and invasive oncocytomas.Methods In this study,we selected 23 null cell adenomas (14 invasive and 9 non-invasive tumors),20 oncocytomas (10 invasive and 10 non-invasive tumors) and 3 normal pituitary glands.ENC1 mRNA and protein expression level in all pituitary tumors and normal pituitary glands was detected by QPCR and western-blot.ENC1 protein expression level was observed by immunohistochemistry (IHC).Results Low levels of ENC1 were found in null cell adenomas and oncocytoma,while high levels were detected in normal pituitary glands.ENC1 mRNA expression level was reduced in invasive null cell adenomas compared to non-invasive null cell adenomas (P ＜ 0.0001) but the results were not found between invasive and non-invasive oncocytomas.Western blot analyses showed that ENC1 expression was significantly lower in invasive null cell adenomas compared with non-invasive null cell adenomas (P ＜ 0.005) and normal pituitary glands.The immunostaining results indicated the ENC1 staining was lighter in invasive null cell adenomas than in non-invasive null cell adenomas,and it was darker in normal pituitary tissues.Conclusion ENC1 may play an important role in invasive null cell adenomas.It could be a specific biomarker for invasive null cell adenomas. Key words: Pituitary neoplasms ; Neoplasm invasiveness ; Gene; ENC1