Reduced levels of E-cadherin correlate with progression of corticotroph pituitary tumours

Objectives Loss of E‐cadherin is an important marker of epithelial tumour progression. The aims of this study were to explore whether E‐cadherin expression and localization correlate to corticotroph tumour progression, relate the expression of the E‐cadherin gene (CDH1) to immunohistochemical E‐cadherin staining pattern, and study whether the E‐cadherin levels were correlated to methylation status of the CDH1 promoter region. Design Immunohistochemical analyses of E‐cadherin protein were performed, as was RT‐qPCR of the CDH1 and the POMC genes. Methylation pattern of the promoter region of CDH1 was measured using pyrosequencing of bisulfite‐treated DNA. Patients Forty‐five patients operated at a tertiary referral centre in Oslo, Norway. Adenoma tissue sections and RNA samples from patients with verified Cushing’s disease or Nelson’s syndrome were collected. Measurements Expression of E‐cadherin mRNA and protein in pituitary corticotroph adenomas and average percentage of methylated cytosines in a cytosine‐phosphate‐guanosine island of the CDH1 promoter. Results Correlations were observed between tumour progression and both nuclear expression of E‐cadherin and reduced CDH1 mRNA. The E‐cadherin expression was not determined by the methylation pattern of the CDH1 promoter. Conclusions Corticotroph tumour progression was associated with reduced expression of the epithelial marker E‐cadherin.