Endocrine Abstracts

Context: Adrenocortical carcinoma (ACC) are endocrine malignant neoplasms associated with severe aggressiveness. By applying of ‘multiple omics’ approach, we recently categorized ACC patients based on their steroidogenic activity and expression of immune activation marker, which is along with prognosis; an ‘immune’ phenotype with good and a ‘steroid’ phenotype with bad outcome.

Hypothesis: Our central hypothesis focuses on the steroid phenotype since it is associated with a glucocorticoid-induced T-cell anergy that ca be rescued by inhibitors of the adrenal steroidogenesis and by reactivating the immune system. Initially, we investigate tumor-infiltrating immune cells and try to identify tumor-specific mutant antigens (TSMA).

Methods: We performed immunofluorescence analysis targeting tumor-infiltrating CD4⁺ and CD8⁺T-cells, regulatory T-cells, B-cells and macrophages/dendritic cells in 58 primary ACC. Additionally, we quantified the expression of the immune checkpoint markers programmed-death 1 (PD1) and its ligand PD-L1 using IHC. Furthermore, ACC-associated somatic mutations were analyzed in silico. The binding affinity (BA) to MHC receptors of mutant peptide and wild type was predicted using netMHCpan.

Results: Most ACCs show infiltrates by T-cells (80%, 37±65 cells/HPF), both cytotoxic (72%, 24±53) and helper cells (57%, 19±16 cells/HPF), Tregs (48%, 4±4) and M?/DC (73%, 6±4) and an intra-tumoral expression of PD1 (36%, 15±30) and PD-L1 (83%, 34±82), while B-cells were absent. Interestingly, the CD4⁺ ACC-infiltrating immune cells are associated with overall survival (HR for death: 0.34, 95%CI 0.12–0.95, P=0.005). The in silico analyses revealed more than 30 potentially relevant TSMA (e.g. RPL22, CTNNB1, ATRX) and in some of them very strong altered BA was detected (RPL22: in HLA A*03:02: 30.3 nM mut. vs 2556.4 nM in wt).

Conclusion: First, tumors of ACC patients are characteristically infiltrated by CD3⁺ CD4⁺T-helper-cells that positively influence patients’ overall survival suggesting prognostic relevance. Second, mutated peptides change their BA to HLAs presenting tumor specific neoantigens that might be recognized by the immune system and be targetable via immunotherapeutic approaches. Prospectively, these generated data will be further investigated and verified in vitro.