Related Experiment Video
Updated: Jun 3, 2025
Multiplexed Immunofluorescence Analysis and Quantification of Intratumoral PD-1+ Tim-3+ CD8+ T Cells
Published on: February 8, 2018
Disruption of tumor-intrinsic PGAM5 increases anti-PD-1 efficacy through the CCL2 signaling pathway
Xiaoying Wei1,2, Hong Wang1,2,3, Huiquan Liu1,2
1Department of Radiation Oncology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, 230001, China.
Background:
Immunosuppressive phenotype compromised immunotherapy efficacy of hepatocellular carcinoma. Tumor cells intrinsic mitochondria dynamics could pass effects on the extracellular microenvironment through mtDNA stress. PGAM5 anchors at mitochondria and regulates mitochondria functions. We aim to explore whether the regulation of tumor-intrinsic PGAM5 on mitochondria affects tumor-infiltrating immune cells in the microenvironment and whether tumor-intrinsic PGAM5 can be a therapeutic target to enhance the immunotherapy efficacy of hepatocellular carcinoma (HCC).
Methods:
We analyzed the correlation of PGAM5 expression and immune cells infiltration using Gene Expression Omnibus (GEO) and The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) data sets based on cibersort algorithm and tumor-tissue arrays from two independent cohorts. To further validate our findings, we established subcutaneous and orthotopic mouse HCC models with tumor-intrinsic Pgam5 deficiency and analyzed tumor-infiltrating immune cells by flow cytometry and single-cell RNA sequencing. Mechanistically, we established an in vitro co-culture system and analyzed proteomics data to find out the bridge between tumor cell PGAM5 and tumor-associated macrophages (TAMs) in the microenvironment. Immunofluorescence, chromatin-immunoprecipitation, ELISA, mass spectrometry were conducted to explore the molecular pathway. Macrophages were depleted to investigate whether the effects of tumor-intrinsic PGAM5 on TAMs could affect immunotherapy efficacy in HCC orthotopic and subcutaneous mouse models.
Results:
PGAM5 expression in tumor was positively correlated with M2-phenotype TAM infiltration in patients with both HCC and mouse HCC tumor models. High tumor-intrinsic PGAM5 expression promoting M2 TAMs infiltration correlated with poor clinical-pathological characteristics and prognosis in patients with HCC. Disruption of tumor-intrinsic Pgam5 reduced TAM M2 polarization and inhibited HCC tumor growth in tumor-bearing mice. Mechanistically, in HCC cells PGAM5 deficiency inhibited mitochondria fission by promoting TRIM28 binding with DRP1, which increased ubiquitination and degradation of DRP1. Tumor-intrinsic PGAM5 deficiency mediated mitochondria fusion and reduced cytosolic mtDNA stress which attenuated TLR9 activation and downstream NF-κB-regulated CCL2 secretion. Furthermore, disruption of tumor-intrinsic Pgam5 significantly facilitated CD8+ T cells activation and improved anti-programmed cell death protein-1 therapeutic efficacy with macrophages depletion compromising synergistic antitumor immune response.
Conclusion:
Our results shed light on the effect of tumor mitochondria dynamics on TAMs in tumor microenvironment. Tumor-intrinsic PGAM5 can be a therapeutic target to improve immunotherapy efficacy in patients with HCC.
Insights
Tumor-intrinsic PGAM5 promotes M2 TAMs in hepatocellular carcinoma (HCC), hindering immunotherapy. Inhibiting PGAM5 enhances CD8+ T cell activation and improves anti-PD-1 therapy efficacy in HCC models.
Area of Science:
- Mitochondrial dynamics in cancer biology
- Immunology and cancer immunotherapy
Background:
- Immunosuppressive tumor microenvironments limit hepatocellular carcinoma (HCC) immunotherapy effectiveness.
- Tumor cell mitochondrial dynamics influence the extracellular microenvironment via mtDNA stress.
- PGAM5, a mitochondrial protein, regulates mitochondrial functions and is explored for its role in HCC.
Purpose of the Study:
- To investigate if tumor-intrinsic PGAM5 affects mitochondria and tumor-infiltrating immune cells in HCC.
- To determine if targeting tumor-intrinsic PGAM5 can enhance HCC immunotherapy efficacy.
Main Methods:
- Correlation analysis of PGAM5 expression and immune cell infiltration using GEO and TCGA-LIHC datasets.
- Validation in subcutaneous and orthotopic mouse HCC models with tumor-intrinsic Pgam5 deficiency.
- In vitro co-culture systems, proteomics, immunofluorescence, and ChIP assays to elucidate molecular mechanisms.
- Macrophage depletion studies to assess immunotherapy efficacy.
Main Results:
- PGAM5 expression positively correlates with M2 TAM infiltration in HCC patients and models.
- High PGAM5 correlates with poor prognosis; Pgam5 deficiency reduces M2 TAMs and inhibits tumor growth.
- PGAM5 deficiency alters mitochondrial dynamics, reduces mtDNA stress, attenuates TLR9 activation, and decreases CCL2 secretion.
- Disruption of PGAM5 enhances CD8+ T cell activation and improves anti-PD-1 therapy, though macrophage depletion affects synergistic response.
Conclusions:
- Tumor mitochondria dynamics significantly impact TAMs within the tumor microenvironment.
- Tumor-intrinsic PGAM5 represents a potential therapeutic target for enhancing HCC immunotherapy.
Related Concept Videos
01:19Interactions Between Signaling Pathways
Convergence and divergence, and cross-talk between signaling pathways
Two distinct signaling pathways can converge on a single functional unit, which may either be a single protein or a complex of proteins. The response is either functionally distinct or synergistic between the two pathways but different from the response...
02:23Abnormal Proliferation
01:27Tumor Immunotherapy
01:31The Intrinsic Apoptotic Pathway