Correlation Between PD-L2 Expression and Clinical Outcome in Solid Cancer Patients: A Meta-Analysis

Area of Science:

• Oncology
• Immunology
• Cancer Research

Background:

• Immune checkpoint inhibitors targeting PD-1/PD-L1 are revolutionizing cancer treatment.
• The prognostic role of programmed cell death ligand 2 (PD-L2) in solid tumors remains debated.
• Understanding PD-L2's impact is crucial for refining cancer prognostication and therapy.

Purpose of the Study:

• To conduct a meta-analysis evaluating the prognostic significance of PD-L2 expression in solid cancer patients after surgical resection.
• To investigate the association between PD-L2 expression and survival outcomes (overall survival, disease-free survival, progression-free survival).
• To explore the correlation between PD-L2 expression and clinicopathological features, including lymphatic metastasis.

Main Methods:

• Systematic literature search of PubMed, Embase, and Cochrane Library up to January 2018 for relevant English-language studies.
• Meta-analysis of 16 studies involving 3,533 patients to pool hazard ratios (HRs) and odds ratios (ORs).
• Statistical analysis to determine the prognostic value of PD-L2 expression for survival and its association with clinicopathological parameters.

Main Results:

• PD-L2 overexpression was a negative predictor for overall survival (HR=1.38) and a strong predictor for poor disease-free/progression-free survival (HR=1.44).
• Subgroup analyses showed high PD-L2 expression predicted unfavorable prognosis in hepatocellular carcinoma (OS: HR=1.60; DFS/PFS: HR=1.50) and clear cell renal cell carcinoma (DFS/PFS: HR=1.45).
• A trend suggested PD-L2 expression is associated with increased lymphatic metastasis (OR=1.61).

Conclusions:

• Elevated PD-L2 expression may facilitate tumor metastasis in solid cancers.
• High PD-L2 levels are associated with an unfavorable prognosis in post-surgery solid cancer patients.
• Hepatocellular carcinoma patients with high PD-L2 expression face a particularly poor outlook.