Project 3: Cellular Immunity and Immune Escape from EGFR Antibody Therapy
Robert L. Ferris, MD, PhD, FACS, Basic Science Co-Leader
Julie E. Bauman, MD, MPH, Clinical Science Co-Leader
Theresa L. Whiteside, PhD, Co-Investigator
There is convincing clinical evidence that the epidermal growth factor receptor (EGFR)-specific monoclonal antibody (mAb), cetuximab, is effective therapy for advanced head and neck squamous cell carcinoma (SCCHN). However, not all patients respond to cetuximab, and clinical responses are not correlated with the level of EGFR expression on tumor cells. Thus, there is a need to understand why clinical responses vary among patients, in order to select those most likely to respond to cetuximab therapy.
In contrast to EGFR tyrosine kinase inhibitors, the antitumor activity of cetuximab may benefit from its interactions with the host's immune system, since cetuximab induces significant killing of SCCHN cells in vitro only in combination with natural killer (NK) cells and monocytes. Furthermore, in an animal model system, the antitumor activity of cetuximab is enhanced by the addition of NK cells. We therefore hypothesize that the antitumor activity of cetuximab is influenced by its ability to trigger an EGFR-specific cellular immune response and by the escape mechanisms SCCHN cells utilize to avoid immune recognition and destruction.
This hypothesis is being tested in 3 parts:
Hypothesis I: the anti-tumor efficacy of cetuximab depends on the NK cell FcγRIIIa genotype, EGFR expression levels on SCCHN targets, and Treg mediated suppression of NK cell lytic activity
- Aim 1.1: To test the hypothesis that the FcγRIIIa genotype expressed by NK cells determines the extent of lysis in ADCC mediated by cetuximab
- Aim 1.2: To test the hypothesis that the EGFR expression level influences cetuximab-mediated lysis of SCCHN cells by NK cells
- Aim 1.3: To test the hypothesis that Treg influences the level of NK cell-mediated cytotoxicity against cetuximab-treated SCCHN cell targets
Hypothesis II: the anti-tumor efficacy of cetuximab depends on the induction of EGFR-specific CTL, which is influenced by the NK cell FcγR genotype, DC interactions with cetuximab-coated SCCHN cells and suppression mediated by regulatory T cells
- Aim 2.1: To test the hypothesis that FcγRIIIa 158VV or VF expressing NK cells are more effective than those expressing FcγRIIIa158FF at enhancing the cross-presentation of cetuximab-coated SCCHN cells by DC
- Aim 2.2: To test the hypothesis that anti-tumor efficacy of cetuximab is depedent on the Treg-mediated suppression of TA cross-presentation by DC loaded with cetuximab-coated SCCHN cells
- Aim 2.3.: To test the hypothesis that anti-tumor efficacy of cetuximab is depedent on Treg-mediated suppression of the cytotolytic activity of TA-specific CTL generated by priming with DC loaded with cetuximab-coated SCCHN cells
Hypothesis III: the in vivo anti-tumor activity of cetuximab in SCCHN patients is influenced by the NK cell FcγR genotype, EGFR-specific CTL activity, frequency of Treg and APM component expression in SCCHN lesions
- Aim 3.1: To perform a single-agent cetuximab clinical trial and establish the association between clinical responses to the neoadjuvant cetuximab therapy and immune/molecular biomarkers in the tumor and blood
- Aim 3.2: To test the hypothesis that clinical responses correlate with the FcγRIIIa polymorphism and activation of NK cells in cetuximab-treated SCCHN patients
- Aim 3.3: To test the hypothesis that clinical responses to cetuximab are related to the frequency of EGFR-specific T cells in SCCHN patients treated with cetuximab
- Aim 3.4: To test the hypothesis that clinical responses to cetuximab are related to the frequency of functional Treg in SCCHN patients
- Aim 3.5: To test the hypothesis that clinical responses to cetuximab correlate with expression of EGFR, HLA class I molecules and APM components in tumor specimens
In this project, we are first characterizing in vitro the variables which are involved in the generation of EGFR-specific cytotoxic T lymphocytes (CTL) by cetuximab. They include the polymorphism of the Fcγ receptors expressed by NK cells, the EGFR expression level on SCCHN cells, and the ability of dendritic cells (DC) to cross-present tumor antigens to T cells following loading with SCCHN cells coated with cetuximab. Subsequently, we are characterizing how the immunosuppressive activity of regulatory T cells interferes with the generation of EGFR-specific CTL as well as with their lytic activity and that of NK cells.
To assess the clinical relevance of the in vitro results, we will determine how the balance between the induction of an EGFR-specific CTL response triggered by cetuximab and the immune escape mechanisms utilized by SCCHN cells impacts the clinical response to (antitumor activity of) cetuximab in SCCHN patients who will be enrolled in a trial associated with this project.
The results derived from this project will have an impact on the clinical application of cetuximab-based immunotherapy in SCCHN patients by identifying predictive immune biomarkers of biological and clinical responses, optimizing the selection of patients to be treated with cetuximab-based immunotherapy, and contributing to the design of interventions to enhance its efficacy. Furthermore, the principles defined with cetuximab may be applicable to other TA-specific mAb; therefore, the information derived from this translational proposal may have a broad significance for the clinical application of antibody-based immunotherapy to the treatment of malignant diseases.