Expression and Prognostic Relevance of PD-1, PD-L1, and CTLA-4 Immune Checkpoints in Adrenocortical Carcinoma

Abstract

Context: Adrenocortical carcinoma (ACC) is a rare endocrine malignancy with poor prognosis in advanced stages. While therapies targeting the checkpoint molecules programmed cell death 1 (PD-1), its ligand PD-L1, and the cytotoxic T lymphocyte-associated protein 4 (CTLA-4) have revolutionized treatment in many cancers, the results in ACCs were heterogeneous.

Objective: Their expression in ACC has not been systematically studied and might explain the variable response to immune checkpoint inhibitors.

Methods: The expression of PD-1, PD-L1 and CTLA-4 was examined in 162 tumor samples from 122 patients with ACC by immunohistochemistry (threshold of >1%) and correlated with tumoral T lymphocyte infiltration and clinical endpoints. Finally, univariate and multivariate analyses of progression-free and overall survival were performed.

Results: PD-1 and PD-L1 were expressed in 26.5% and 24.7% of samples, respectively, with low expression in most tumor samples (median positive cells: 2.1% and 21.7%). In contrast, CTLA-4 expression was observed in 52.5% of ACC with a median of 38.4% positive cells. Positive PD-1 expression was associated with longer progression-free survival (HR 0.50, 95% CI 0.25-0.98, P = .04) even after considering prognostic factors. In contrast, PD-L1 and CTLA-4 did not correlate with clinical outcome. Additionally, PD-1 and PD-L1 expression correlated significantly with the amount of CD3+, CD4+, FoxP3+, and CD8+ T cells.

Conclusion: The heterogeneous expression of PD1, PD-L1, and CTLA-4 in this large series of well-annotated ACC samples might explain the heterogeneous results of the immunotherapies in advanced ACC. In addition, PD-1 expression is a strong prognostic biomarker that can easily be applied in routine clinical care and histopathological assessment.

Keywords: CTLA-4; PD-1; PD-L1; adrenocortical carcinoma; glucocorticoids; immune checkpoints; immunotherapy; prognostic marker.

Figure 1.

Immune checkpoint molecules in adrenocortical carcinoma. Representative chromogenic immunohistochemical staining of immune checkpoint molecules, PD-1, PD-L1, and CTLA-4 (>1%), in primary tumors (A-F) and lymph node metastases (G-I), n = 162.

Figure 2.

Expression of PD-1 (A), PD-L1 (B), and CTLA-4 (C) immune checkpoint molecules in primary tumors, local recurrences, lymph node metastases, and distant metastases of adrenocortical carcinoma (>1% of positive cells). *P < .05; **P < .01; ***P < .001; ****P < .0001. NS, not significant.

Figure 3.

Overall survival (Kaplan–Meier analysis; A-C) and progression-free survival (Kaplan–Meier analysis; D-F) of patients with adrenocortical carcinoma according to PD-1, PD-L1, and CTLA-4 expression. Due to the significant results of the univariate Cox regression for PD-1, a multivariate analysis was performed (G). For A-C only, primary tumors were analyzed; for the other analyses, samples from local recurrences and metastases were included.