Endocrine Abstracts

Background: Immune checkpoint therapy response rate in adrenocortical carcinoma (ACC) is only ~15%. Glucocorticoid (GC) secretion is present in ~60% of tumours, associated with adverse outcome and has been associated with an immunologically cold tumoural microenvironment. On the other hand, activation of the Wnt/ß-Catenin pathway has been suggested to contribute to reduced immune infiltration.

Aims: First, we aim to improve the understanding of cellular responses to glucocorticoid receptor (GCR) activation and antagonism and additionally understand the effect of tumoural steroid excess onto glucocorticoid related genes. Second, we hypothesize that activation of the Wnt/ß-Catenin pathway is associated with less tumor infiltrating immune cells.

Methods: Cultured ACC cell lines NCI-H295R and JIL-2266 were treated with the selective GCR antagonist relacorilant and expression of GCR target genes analyzed by qPCR. Nanostring NCounter was used on FFPE extracted RNAs of hormonally active and inactive tumours. Cell viability was measured by CellTiter GloAssay and protein expression quantified by Western blotting for the glucocorticoid receptor (GR) and the cancer-testis antigen PRAME.

Results: Hormonally active tumours showed a downregulation of immune-related genes and an upregulation of glucocorticoid related genes. Up to 1 μM relacorilant in combination with 400 nM hydrocortisone had no effect on ACC cell viability, but expression of GCR target genes was significantly altered in a cell line specific manner. In NCI-H295R cells, the expression of CYP17A1 was dose-dependently repressed by relacorilant, while genes encoding the IL1 receptor were consistently up-regulated. PRAME was expressed in NCI-H295R and repressed by relacorilant.

Conclusion: Treatment with relacorilant leads to a downregulation of glucocorticoid related genes like CYP17A1 in NCIH295R and an upregulation in immune related genes like IL1R1. This might lead to lower steroid levels and higher immune cell infiltration and contribute to a better response to the immunotherapy.