Background Metastatic pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors associated with poor prognosis and limited therapeutic options. Recent advances in oncology-related immunotherapy, specifically targeting of the programmed death 1 (PD-1)/-ligand 1 (PD-L1) pathways, have uncovered new treatment potential for a variety of tumors. The expression of PD-L1 and PD-L2 was recently found to be present in 18% and 16% of PPGL, respectively, but only PD-L2 expression correlated with malignancy, hypoxia markers, and shorter survival.¹ However, PD-L1 was suggested to be a malignant proliferation biomarker for PPGLs in another study.² Given the promising outcomes of a clinical study in 9 cases of PPGL using pembrolizumab, a humanized IgG4κ monoclonal antibody that targets the PD-1/PD-L1 pathway,³ we examined the PD-Ls expression in our representative PPGL cohort to explore if PD-Ls expression can predict malignancy and/or be a predictive marker for PD-Ls targeted therapy in PPGL.

Methods The Cancer Genome Atlas (TCGA) provided 173 patient samples to allow for observation of gene expression across four PPGL driver mutation groups (Cluster I: SDHB, VHL; Cluster II: NF1, RET) and NAM samples. Tumor RNA from the 48-patient cohort (sporadic; Cluster I: SDHB, VHL, EPAS1; Cluster II: RET, NF1) was evaluated to validate the results.

Results Expression of PD-L1, but not PD-L2, was elevated in our PPGL cohort, which aligns with TCGA analysis. Expression of PD-L1 was decreased in Cluster I PPGLs but not in Cluster II, suggesting that sporadic and Cluster II PPGLs could benefit from PD-1/PD-L1 targeted therapy more than Cluster I PPGL tumors. Within Cluster I, expression of PD-L1 was significantly lower in SDHB- and VHL-mutated tumors compared to sporadic tumors. Expression of PD-L2 did not differ between PPGL clusters. Metastatic PPGLs had significantly elevated Ki-67 levels, however PD-Ls expression was not affected by malignancy status.

Conclusions We conclude that PD-Ls expression in our cohort of PPGL tumors was not linked to malignancy, however, driver mutation analysis could be a selective marker for PD-Ls-targeted therapy.

References

1. Pinato DJ, Black JR, Trousil S, Dina RE, Trivedi P, Mauri FA, Sharma R. Programmed cell death ligands expression in phaeochromocytomas and paragangliomas: Relationship with the hypoxic response, immune evasion and malignant behavior. Oncoimmunology. 2017;6(11):e1358332

2. Guo D, Zhao X, Wang A, Xie Q, Xu X, Sun J. PD-L1 expression and association with malignant behavior in pheochromocytomas/paragangliomas. Hum. Pathol. 2019; 86:155–162.

3. Naing A, Gainor JF, Gelderblom H, Forde PM, Butler MO, Lin CC, Sharma S, Ochoa de Olza M, Varga A, Taylor M, Schellens JHM, Wu H, Sun H, Silva AP, Faris J, Mataraza J, Cameron S, Bauer TM. A first-in-human phase 1 dose escalation study of spartalizumab (PDR001), an anti-PD-1 antibody, in patients with advanced solid tumors. J Immunother Cancer. 2020; 8(1):e000530.

Ethics Approval The study protocol was approved by the Eunice Kennedy Shriver National Institute of Child Health and Human Development Institutional Review Board (NIH Protocol 00-CH-0093).

Consent All patients provided written informed consent approved by the National Institutes of Health ethics committee.