Dissertation
Anti-tumor responses of endosomal toll-like receptor-based immunotherapy in head and neck squamous cell carcinoma
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2020
DOI: 10.17077/etd.005411
Abstract
Immunotherapy with antibodies targeting programmed cell death protein-1 (anti-PD1) are FDA approved as first-line therapy for recurrent and/or metastatic (R/M) head and neck squamous cell carcinoma (HNSCC). Although unprecedented durable effects are observed, only a minority of HNSCC patients derive benefit from these therapies due to their ineffectiveness in poorly immunogenic tumors. Absent or limited dendritic cell (DC) activity is believed to impede on the ability of anti-PD1 to trigger anti-tumor immune responses. Therefore, strategies that enhance DC activity may improve tumor responses to immunotherapeutic agents.
DCs robustly express toll-like receptors (TLRs) which are a class of pattern-recognition receptors that recognize structurally conserved molecules and trigger innate and adaptive immune responses. TLR stimulation in cancer therapy can potentially show both pro-tumorigenic and anti-tumor responses. However, agonists for endosomal TLRs (e.g. TLR3/7/8/9) have demonstrated anti-tumor responses in various preclinical models. In particular, TLR8 and TLR9 signaling has been shown to increase the maturation and activity of DCs leading to the enhancement of natural killer (NK) and T cell responses. The overall goal of these studies is to determine if TLR8 and TLR9 agonists would enhance anti-tumor immune responses to immunotherapy agents used for R/M HNSCC.
The effects of the TLR8 agonist motolimod and the TLR9 agonist CMP-001 on immune cell activation and cytokine secretion was performed using co-cultures of human peripheral blood mononuclear cells (PBMCs) and HNSCC cells and analyzed by flow cytometry and ELISA. Correlations between TLR8 or TLR9 gene expression and survival outcomes were investigated in HNSCC patients using The Cancer Genome Atlas (TCGA) database and tissue microarray (TMA) analyses. In vivo anti-tumor effects, survival outcomes, immune cell infiltration and circulating cytokine levels were investigated using syngeneic tumor mouse models.
Results showed that both TLR8 and TLR9 gene expression were positively correlated with overall survival in HNSCC patients. With respect to TLR8, increased TLR8 protein expression was associated with increased CD8+ T cell infiltration and favorable survival outcomes especially in epidermal growth factor receptor (EGFR)-negative patients. When the TLR8 agonist motolimod was combined with cetuximab (EGFR monoclonal antibody that enhances NK cell activity) in a human-expressing EGFR tumor mouse model, a significant decrease in tumor growth accompanied by infiltration of splenic lymphoid DCs and tumor-specific CD4+/CD8+ T cells were observed compared to each agent alone. Depletion of CD4+ T cells, CD8+ T cells and NK cells were all able to abolish the anti-tumor effect of motolimod in combination with cetuximab. These studies suggest that TLR8 agonists may be promising as an adjuvant for cetuximab-based therapy particularly in patients with high TLR8 expression.
With respect to TLR9, results showed that the TLR9 agonist CMP-001 increased the activation of human plasmacytoid DCs and monocytes in vitro and in situ vaccination with CMP-001 suppressed injected tumors and contralateral (un-injected) tumors. When CMP-001 was combined with anti-PD1 therapy (PD1 monoclonal antibody that triggers anti-tumor T cell responses), significant durable tumor regression at both injected and un-injected tumor sites and prolonged survival was observed compared to anti-PD1 therapy alone. The anti-tumor effect of CMP-001 in combination with anti-PD1 was accompanied by increased CD4+/CD8+ T cell infiltration and was completely abrogated by CD8+ T cell depletion. These studies suggest that in situ vaccination with CMP-001 can induce both local and abscopal anti-tumor immune responses.
Altogether, the studies presented here demonstrate that TLR8 and TLR9 agonists can stimulate DC activation and anti-tumor immune responses alone and in combination with standard immunotherapeutic agents (i.e. cetuximab and anti-PD1 antibodies) used for the treatment of R/M HNSCC. These studies warrant further study of endosomal TLR activation as a novel immunotherapeutic strategy to enhance HNSCC therapy and improve survival outcomes for HNSCC patients.
Details
- Title: Subtitle
- Anti-tumor responses of endosomal toll-like receptor-based immunotherapy in head and neck squamous cell carcinoma
- Creators
- Yinwen Cheng
- Contributors
- Andrean L Simons-Burnett (Advisor)Aliasger K Salem (Committee Member)Douglas E Laux (Committee Member)Gabriele Ludewig (Committee Member)George J Weiner (Committee Member)Jon C Houtman (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Human Toxicology
- Date degree season
- Spring 2020
- DOI
- 10.17077/etd.005411
- Publisher
- University of Iowa
- Number of pages
- xi, 130 pages
- Copyright
- Copyright 2020 Yinwen Cheng
- Language
- English
- Description illustrations
- illustrations (some color)
- Description bibliographic
- Includes bibliographical references (pages 116-130).
- Public Abstract (ETD)
Most patients with late stage head and neck squamous cell carcinoma (HNSCC) cannot be cured with current therapies and have a poor survival rate. Immunotherapy using checkpoint blockade inhibitors is used to treat HNSCC, which accounts for more than 90% of head and neck cancers. Unfortunately, only a small subset of HNSCC patients respond to these therapies. It is believed that the lack of immune cells, especially activated dendritic cells (DCs) present in HNSCCs may be responsible for the poor responses observed in immunotherapy-treated HNSCC patients including those treated with checkpoint blockade therapy. Therefore, strategies that enhance DC activity may improve tumor responses to immunotherapeutic agents.
In this work we explore another class of immunostimulatory agents, toll-like receptor (TLR) agonists, as a strategy to increase DC activity and enhance tumor response to immunotherapy of HNSCC. Using the TLR8 agonist motolimod and the TLR9 agonist CMP-001, we show that both agents can stimulate DC activity and induce anti-tumor immune responses in tumor-bearing mice. We also show that the anti-tumor response to standard immunotherapeutic agents used to treat HNSCC (cetuximab, anti-programmed cell death protein 1 antibodies) can be greatly improved with the use of TLR agonists. Overall our results suggest that TLR8 and TLR9 agonists are promising for HNSCC therapy and warrant further study in order to improve survival outcomes for HNSCC patients.
- Academic Unit
- Craniofacial Anomalies Research Center; Interdisciplinary Graduate Program in Human Toxicology
- Record Identifier
- 9983966296302771
Metrics
21 File views/ downloads
91 Record Views