Antitumor Effects of Dendritic Cell Immunoradiotherapy Combined with an Immune Checkpoint Inhibitor in a Murine Head and Neck Cancer Model = 마우스 두경부암에서 수지상세포 면역방사선치료와 면역관문억제제 병합의 항암효과

다국어 초록 (Multilingual Abstract)

Objectives: Head and neck squamous cell carcinoma (HNSCC) remains a therapeutic challenge because of tumor immune evasion and the limited efficacy of current immunotherapies. This study evaluated the antitumor efficacy of combining programmed death-1 (PD-1) blockade with dendritic cell (DC)-based immunoradiotherapy in a murine model of HNSCC, with a focus on tumor control and immune modulation.

Materials and Methods: SCC-VII cells were subcutaneously injected into the right thigh and both flanks of C3H/HeJ mice. Tumor growth inhibition, survival, and immune cell profiles were evaluated among six treatment groups: control, anti-PD-1 (aPD-1), radiotherapy (RT), aPD-1 + RT, immature dendritic cell + RT (iDC/RT), and aPD-1 + iDC/RT.

Results: The triple combination (aPD-1 + iDC/RT) showed the strongest inhibition of tumor growth and the longest survival. The response was observed in the irradiated primary tumor and also in non-irradiated distant tumors. Immune analyses demonstrated increased effector T cells, antigen-specific IFN-γ responses, and cytotoxic activity, together with decreased regulatory T cells.

Conclusions: DC-based immunoradiotherapy in combination with aPD-1 synergistically enhances tumor-specific antitumor immunity and enhances the abscopal effect, highlighting its potential as an effective therapeutic strategy for HNSCC.

국문 초록 (Abstract)

목적: 두경부 편평세포암(HNSCC)은 종양의 면역 회피와 현재 면역치료의 제한된 효과로 인해 여전히 치료가 어렵다. 본 연구는 마우스 HNSCC 모델에서 PD-1(programmed death-1) 차단 요법과 수지상세포(DC) 기반 면역방사선치료를 병합했을 때의 항종양 효과를 평가하고, 종양 조절 및 면역 반응 변화를 확인하고자 하였다.

재료 및 방법: SCC-VII 세포를 C3H/HeJ 마우스의 우측 대퇴부 및 양측 옆구리에 피하 주입하여 두경부 편평세포암 모델을 구축하였다. 대조군, 항PD-1 단독군, 방사선치료(RT) 단독군, 항PD-1 + RT군, 미성숙 수지상세포(iDC) + RT군, 항PD-1 + iDC/RT군의 6개 치료군에서 종양 성장 억제, 생존율, 면역세포 프로파일을 비교하였다.

결과: 삼중 병합요법인 aPD-1 + iDC/RT군에서 종양 성장 억제 효과가 가장 컸고, 생존 기간도 가장 길었다. 이러한 효과는 방사선이 조사된 원발 종양뿐 아니라 비조사된 원격 종양에서도 확인되었다. 면역학적 분석에서 효과 T 세포, 항원 특이 IFN-γ 반응, 세포독성 활성이 증가하였고, 조절 T 세포는 감소하였다.

결론: DC 기반 면역방사선치료와 PD-1 차단 요법을 병합한 치료는 종양 특이적 항종양 면역을 강화하고, 원격 종양에 대한 반응(압스코팔 효과, abscopal effect)을 향상시켰으며, 생존 기간을 개선하였다. 따라서 본 병합 치료 전략은 HNSCC에서 임상 적용의 잠재력을 제시한다.

목차 (Table of Contents)

• Abstract i
• Table of Contents iii
• List of Figures v
• List of Abbreviations vi
• Chapter 1. Introduction 1
• Chapter 2. Materials and Methods 4
• 1. Animals 4
• 2. Cell Line 4
• 3. Preparation of Bone Marrow-derived Dendritic Cells 4
• 4. Radiation-induced Apoptosis Assay in SCC-VII Cells 5
• 5. In Vitro Assay for PD-L1 Expression on Tumor Cells and iDCs 5
• 6. Radiotherapy and Immunization Procedure 6
• 7. Treatment Groups 7
• 8. Flow Cytometric Analysis for T Cells 7
• 9. Enzyme-linked Immunospot (ELISpot) Assay 8
• 10. Cytotoxicity Assay 9
• 11. Statistical Analysis 9
• Chapter 3. Results 13
• 1. Irradiation Induces a Dose- and Time-Dependent Increase in Apoptosis in SCC-VII Cells 13
• 2. Irradiation Induces Time-Dependent Upregulation of PD-L1 Expression on SCC-VII Tumor Cells 17
• 3. Combination of PD-1 Blockade and iDC Immunoradiotherapy Exhibits the Most Potent Antitumor Effect in HNSCC 20
• 4. Combination of PD-1 Blockade and iDC Immunoradiotherapy Extends Survival in SCC-VII Tumor-Bearing Mice 32
• 5. Combined Immunoradiotherapy Enhances Effector T cells and Suppresses Regulatory T Cells in the spleen 36
• 6. Combined Immunoradiotherapy Enhances Antigen-Specific IFN-γ Responses 42
• 7. Combined Immunoradiotherapy Enhances Cytotoxic Activity Against SCC-VII Tumor Cells 46
• Chapter 4. Discussion 50
• Chapter 5. Conclusions 62
• Conflict of Interest 63
• Bibliography 64
• Abstract in Korean 72
• Acknowledgments 73