Wnt/-catenin pathway activation is associated with glucocorticoid secretion in adrenocortical carcinoma, but not directly with immune cell infiltration

Tanja Maier ¹ Laura-Sophie Landwehr ² Alexandra Triebig ¹ Stefan Kircher ^2* Marc P Schauer ² Thomas Knösel ^1* Silviu Sbiera ² Petra Zimmermann ^2* Martin Reincke ^1* Isabel Weigand ^1* Martin Fassnacht ² Matthias Kroiss ^1*

• ¹ LMU Munich University Hospital, Munich, Germany
• ² University Hospital Würzburg, Würzburg, Bavaria, Germany

Background: In advanced adrenocortical carcinoma (ACC), the response rate to immune checkpoint inhibition (ICI) is only ~15 %. Glucocorticoid (GC) secretion and the activation of the Wnt/β-catenin pathway have been suggested to contribute to low tumour immune cell infiltration. The transcription factor lymphoid enhancer factor 1 (LEF-1) transduces β-catenin (CTNNB1)-mediated transcriptional activation.Objective: To understand the contribution of Wnt/β-catenin pathway activation and glucocorticoid receptor (GR) signalling to the immunologically cold ACC tumour microenvironment.Methods: Semi-quantitative immunohistochemistry (IHC) of β-catenin (CTNNB1), LEF-1, GR and T cell markers CD3, CD4, CD8, FoxP3 in 59 ACC samples. Targeted RNA expression analysis of 486 immune-related genes in 58 additional ACC tissue specimens. Correlative analyses with clinical data.Results: Nuclear LEF-1 and CTNNB1 protein expression were positively correlated in ACC tissue (Pearson R 2 = 0.1283, p=0.0046). High, moderate and low protein expression was detected in 24.1 %, 53.2 % and 19.3 % of samples for LEF-1, and 30.6 %, 43.5 % and 19.3 % for CTNNB1, respectively. We found higher LEF-1 expression in GC-secreting tumours which did not differ from inactive tumours in terms of GR expression. T cell markers, as evaluated by IHC, were not associated with expression of Wnt/-catenin pathway markers. At RNA level, tumours with high LEF-1 expression showed significant downregulation of 37 transcripts (including 8 involved in antigen presentation). High LEF-1 expression levels correlated with worse overall survival in this cohort. This was not the case for CTNNB1 and GR. Conclusion: LEF-1 expression is useful as a biomarker of activated Wnt/-catenin signalling in ACC. Wnt/-catenin pathway activation was not associated with reduced immune cell markers in ACC but GC secretion and may be related to tumoural antigen presentation.