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Updated: May 22, 2026
Experimental Melanoma Immunotherapy Model Using Tumor Vaccination with a Hematopoietic Cytokine
Published on: February 24, 2023
Toll-like receptor 4 gene polymorphism influences dendritic cell in vitro function and clinical outcomes in
Andrés Tittarelli1, Fermín E González, Cristián Pereda
1Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, 8380453, Santiago Chile, Chile. tittarelli@gmail.com
Abstract:
Toll-like receptor 4 (TLR4) is expressed on dendritic cells (DCs), sensing environmental danger molecules that induce their activation and maturation. Recently, we reported a method for the production of therapeutic DCs against melanoma, called tumor antigen-presenting cells (TAPCells), using a heat-shocked allogeneic melanoma cell lysate (TRIMEL) as an activation factor and antigen provider. Since TRIMEL contains endogenous TLR4 ligands, we evaluated the role of TLR4 in TAPCells differentiation by antibody neutralization and the association of a Tlr4 polymorphism (896A/G) (Asp299Gly), determined by PCR-RFLP, with the in vitro activation capacity and the clinical outcome of TAPCells-vaccinated patients. Antibody blocking of monocyte TLR4 inhibited surface expression, determined by flow cytometry, of the major histocompatibility complex class I, CCR7, CD80, CD83 and CD86 on TAPCells, reduced interleukin (IL)-6 and tumor necrosis factor -α gene expression evaluated by qRT-PCR, and also inhibited the TAPCells-mediated interferon-γ (IFN-γ) secretion of melanoma-specific CD8(+) T cells determined by ELISpot (p < 0.01). Moreover, CD8(+) T-cell activation capacity was significantly reduced in TAPCells bearing the TLR4 Asp299Gly receptor (p < 0.05). Finally, TAPCells-vaccinated stage-IV melanoma patients bearing the Tlr4 896G allele showed a shortened post-therapy median survival rate compared with those carrying the Tlr4 896A allele (p < 0.05; log-rank test). Our results indicate that TLR4 is a key receptor for the tumor lysate-mediated in vitro generation of clinically efficient antigen-presenting cells. Further analysis of patients included in different vaccine protocols is necessary for definitively establishing a role for TLR4 polymorphism in clinical responses.
Insights
Toll-like receptor 4 (TLR4) is crucial for generating effective therapeutic dendritic cells (TAPCells) from melanoma tumor lysate. TLR4 activation and specific genetic variations impact TAPCells
Area of Science:
- Immunology
- Oncology
- Genetics
Background:
- Toll-like receptor 4 (TLR4) is expressed on dendritic cells (DCs) and recognizes danger signals, promoting their activation.
- Therapeutic DCs, termed tumor antigen-presenting cells (TAPCells), are generated using heat-shocked melanoma cell lysate (TRIMEL).
- TRIMEL contains TLR4 ligands, suggesting a role for TLR4 in TAPCells differentiation.
Purpose of the Study:
- To investigate the role of TLR4 in TAPCells differentiation and function.
- To assess the impact of a TLR4 polymorphism (Asp299Gly) on TAPCells' in vitro activation capacity.
- To correlate TLR4 genotype with clinical outcomes in melanoma patients vaccinated with TAPCells.
Main Methods:
- Antibody neutralization of monocyte TLR4.
- Flow cytometry to assess surface marker expression on TAPCells.
- Quantitative reverse transcription PCR (qRT-PCR) for gene expression analysis (IL-6, TNF-α).
- ELISpot assay to measure interferon-γ (IFN-γ) secretion by T cells.
- PCR-RFLP to determine Tlr4 polymorphism (896A/G).
Main Results:
- TLR4 blockade inhibited TAPCells maturation markers (MHC class I, CCR7, CD80, CD83, CD86) and reduced IL-6 and TNF-α gene expression.
- TLR4 blockade also impaired TAPCells-mediated IFN-γ secretion by melanoma-specific CD8(+) T cells.
- TAPCells generated from monocytes with the TLR4 Asp299Gly receptor showed reduced CD8(+) T-cell activation capacity.
- Melanoma patients with the Tlr4 896G allele had a shorter survival rate after TAPCells vaccination compared to those with the 896A allele.
Conclusions:
- TLR4 is essential for the in vitro generation of clinically effective antigen-presenting cells using tumor lysate.
- The TLR4 Asp299Gly polymorphism is associated with reduced in vitro T-cell activation.
- TLR4 genotype may influence clinical response in melanoma patients receiving TAPCells immunotherapy, warranting further investigation.
