Abstract 6742: PV 10 induces endoplasmic reticulum stress and autophagy, triggering immunogenic cell death and anti-tumor immunity in head and neck squamous cell carcinoma

Abstract Introduction: Head and neck squamous cell carcinoma (HNSCC) are complex, diverse cancers affecting mucosal linings of the upper aerodigestive tract. Globally, HNSCC is the sixth most common cancer, leading to over 890, 000 new cases and more than 450, 000 deaths annually. Primary risk factors include human papillomavirus (HPV) infection (HPV-positive HNSCC) and exposure to tobacco and excessive alcohol (HPV-negative HNSCC). Despite multimodal treatments, survival rates remain low due to recurrence and metastasis (R/M HNSCC), creating a need for safe, innovative therapies to reduce tumor burden with minimal adverse events. PV-10 (10% rose bengal sodium) is a novel intratumoral immunotherapeutic agent that has demonstrated promising anti-tumor activity in multiple solid tumor cancer types with few adverse effects in pre-clinical research and clinical trials. However, the role of PV-10 in HNSCCs and its role in enhancing immune response warrants further investigation. Methods: Cell viability was assessed using Alamar blue assay after PV-10 treatment of murine mEER and MTE-RAS HNSCC tumor cell lines. To evaluate the immunomodulatory properties of PV-10, we employed flow cytometry, confocal analysis, and luminescence-based assays. Additionally, we performed a DCFDA assay to measure the reactive oxygen species (ROS) and an Alexa Fluor 488 Annexin V/dead cell apoptosis assay to evaluate apoptosis. To gain insights into the mechanisms underlying PV-10's immunomodulatory effects in cancer cells and tumors from mice, western blotting and multiplex immunohistochemistry (mIHC) were used. Results: Our in vitro findings reveal that PV-10 induces cytotoxicity in both mEER and MTE-RAS cells. Notably, PV-10 promotes a significant increase in ROS, leading to an elevation in late apoptotic cells. Markers of immunogenic cell death (ICD), including a statistically significant increase in the release of damage-associated molecular pattern molecules HMGB1 and ATP, as well as enhanced surface expression of calreticulin, HSP-70, and HSP-90, were observed. At the molecular level, a remarkable activation of endoplasmic reticulum (ER) stress, pro-apoptotic protein, and autophagy markers were observed. Intratumoral PV-10 injection in vivo has shown significant tumor regression in both mEER and MTE-RAS tumors, and a complete response was noticed in some mice, indicating that PV-10 induces potent ICD in both mEER and MTE-RAS tumors. Conclusion: Our collated evidence strongly suggests that PV-10 induces ICD-associated immunogenicity in both mEER and MTE-RAS in vitro and in vivo, fostered by ROS-based ER stress and apoptosis. These findings hold promise for potential therapeutic avenues to manage HNSCC. Citation Format: Sowjanya Thatikonda, Ritu Chaudhary, Yeva Meshkovska, Maria I. Biernacki, Robbert Slebos, Shari P. Thomas, Amelio L. Antonio, Eric A. Wachter, Christine H. Chung. PV 10 induces endoplasmic reticulum stress and autophagy, triggering immunogenic cell death and anti-tumor immunity in head and neck squamous cell carcinoma abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 6742.