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Updated: Aug 4, 2025
Immunohistochemical Staining of B7-H1 PD-L1 on Paraffin-embedded Slides of Pancreatic Adenocarcinoma Tissue
Published on: January 3, 2013
Pan-cancer analysis identifies PD-L2 as a tumor promotor in the tumor microenvironment
Jingfang Lv1, Zheng Jiang1, Junhu Yuan2
1Department of Colorectal Surgery, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
Background:
Programmed cell death protein 1 (PD-1) receptor has two ligands,programmed death-ligand 1 (PD-L1) and PD-L2. When compared with PD-L1, PD-L2 has not received much attention, and its role remains unclear.
Methods:
The expression profiles of pdcd1lg2 (PD-L2-encoding gene) mRNA and PD-L2 protein were analyzed using TCGA, ICGC, and HPA databases. Kaplan-Meier and Cox regression analyses were used to assess the prognostic significance of PD-L2. We used GSEA, Spearman's correlation analysis and PPI network to explore the biological functions of PD-L2. PD-L2-associated immune cell infiltration was evaluated using the ESTIMATE algorithm and TIMER 2.0. The expressions of PD-L2 in tumor-associated macrophages (TAMs) in human colon cancer samples, and in mice in an immunocompetent syngeneic setting were verified using scRNA-seq datasets, multiplex immunofluorescence staining, and flow cytometry. After fluorescence-activated cell sorting, flow cytometry and qRT-PCR and transwell and colony formation assays were used to evaluate the phenotype and functions of PD-L2+TAMs. Immune checkpoint inhibitors (ICIs) therapy prediction analysis was performed using TIDE and TISMO. Last, a series of targeted small-molecule drugs with promising therapeutic effects were predicted using the GSCA platform.
Results:
PD-L2 was expressed in all the common human cancer types and deteriorated outcomes in multiple cancers. PPI network and Spearman's correlation analysis revealed that PD-L2 was closely associated with many immune molecules. Moreover, both GSEA results of KEGG pathways and GSEA results for Reactome analysis indicated that PD-L2 expression played an important role in cancer immune response. Further analysis showed that PD-L2 expression was strongly associated with the infiltration of immune cells in tumor tissue in almost all cancer types, among which macrophages were the most positively associated with PD-L2 in colon cancer. According to the results mentioned above, we verified the expression of PD-L2 in TAMs in colon cancer and found that PD-L2+TAMs population was not static. Additionally, PD-L2+TAMs exhibited protumor M2 phenotype and increased the migration, invasion, and proliferative capacity of colon cancer cells. Furthermore, PD-L2 had a substantial predictive value for ICIs therapy cohorts.
Conclusion:
PD-L2 in the TME, especially expressed on TAMs, could be applied as a potential therapeutic target.
Insights
Programmed death-ligand 2 (PD-L2) is expressed in many cancers and linked to poor outcomes. Targeting PD-L2 on tumor-associated macrophages may offer a new therapeutic strategy.
Area of Science:
- Immunology
- Oncology
- Molecular Biology
Background:
- Programmed cell death protein 1 (PD-1) has two ligands: PD-L1 and PD-L2.
- PD-L2's role in cancer is less understood compared to PD-L1.
Purpose of the Study:
- To investigate the expression, function, and prognostic significance of PD-L2 in human cancers.
- To explore PD-L2's role in the tumor microenvironment (TME) and its association with immune cells, particularly macrophages.
- To evaluate PD-L2 as a potential therapeutic target for cancer immunotherapy.
Main Methods:
- Analysis of PD-L2 mRNA and protein expression using TCGA, ICGC, and HPA databases.
- Prognostic significance assessed via Kaplan-Meier and Cox regression analyses.
- Exploration of biological functions and immune cell infiltration using GSEA, correlation analysis, and bioinformatics tools.
- Verification of PD-L2 expression in tumor-associated macrophages (TAMs) using scRNA-seq, immunofluorescence, and flow cytometry.
- Functional assays on PD-L2+ TAMs and prediction of immunotherapy response and drug targets.
Main Results:
- PD-L2 expression was detected in all common human cancers, correlating with poorer patient outcomes.
- PD-L2 is closely associated with immune molecules and plays a significant role in cancer immune response.
- PD-L2 expression strongly correlates with immune cell infiltration, especially macrophages, in colon cancer.
- PD-L2+ TAMs exhibit a protumor M2 phenotype, enhancing cancer cell migration, invasion, and proliferation.
- PD-L2 demonstrates predictive value for immune checkpoint inhibitor (ICI) therapy response.
Conclusions:
- PD-L2 expression in the TME, particularly on TAMs, presents a potential therapeutic target.
- Targeting PD-L2 may represent a novel strategy for enhancing cancer immunotherapy efficacy.
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