Background: Activation of the Wnt/β-catenin pathway is frequent in adrenocortical tumors (ACTs). This pathway and DAX1, a negative regulator of SF1 expression, control adrenal stem/progenitor cells, which can be involved in ACTs formation.
Objective: To analyse the association between the Wnt/β-catenin pathway and the expression of a stem cell marker (NANOG), STAT3, DAX1 and SF1 in ACTs.
Methods: Patients: 70 paediatric and 18 adults with ACTs; Control adrenals: 13 children and 13 adults. mRNA expression of DAX1, SF1, STAT3 and NANOG evaluated by qPCR. Protein expression of SF1 and DAX1 evaluated by immunohistochemistry. Copy number variation of SF1 and DAX1 evaluated by MLPA. In vitro the effect of inhibition of the Wnt/β-catenin pathway with PNU on NANOG expression was evaluated in H295 adrenal tumour cells.
Results: Decreased expression of SF1 mRNA was found in 84% of paediatric ACTs (P=0.02) but not in adult ACTs (P=0.49). Conversely, overexpression of DAX1 mRNA was found in 89% of adult ACTs (P<0.01) but not in paediatric ACTs (P=0.65). STAT3 mRNA expression was higher in adult than in paediatric ACTs (P<0.01). p.S45P CTNNB1/β-catenin mutated ACTs presented increased expression of NANOG (P<0.01). In vitro inhibition of the Wnt/β-catenin pathway impaired NANOG mRNA expression in a dose-dependent manner (P<0.01). At protein level, moderate or strong nuclear staining of SF1 was found in 78 and 19% of paediatric and adult ACTs, respectively. Moderate to strong nuclear staining of DAX1 was found in 48% of paediatric ACTs but not in adult ACTs, in which only weak nuclear staining was present. MLPA analysis revealed SF1 gene amplification in 23 and 15% of paediatric and adult ACTs, respectively.
Conclusion: Post-translational mechanisms, likely associated with the loss of inhibition exerted by DAX1, regulate the overexpression of SF1 in paediatric ACTs. NANOG may play a role in Wnt/β-catenin activation in ACTs, particularly in the presence of the p.S45P β-catenin mutation.
Funding: CAPES, FAPESP and CNPq.
01 - 03 Oct 2015
European Society for Paediatric Endocrinology