Abstract LB_B24: Validating novel therapeutic antibodies for targeting head & neck squamous cell malignancies
Authors: Basta Ameer S , Roche Marc de la 
Published: December 2023

Abstract
Introduction: Head and Neck Squamous Cell Carcinoma (HNSCC) encompasses cancers of the lips, oral cavity, larynx, pharynx, and salivary glands. The prevalence of HNSCC is approximately 890,000 new cancer cases per year, with a mortality rate of 450,000, making it the 7th most common cancer worldwide. Standard-of-care treatments involve surgery and conventional chemotherapy, underscoring the necessity for novel and effective targeted therapeutic interventions. The aim of my study was to determine whether the cancer stem cell marker LGR5 (leucine-rich repeat-containing G-protein receptor 5) is overexpressed in HNSCC, in order to validate our novel and highly specific LGR5 antibody (α-LGR5) as an effective diagnostic and therapeutic agent.
Objectives:1. Develop a fluorescently labeled version of α-LGR5. 2. Characterize LGR5 expression in HNSCC cell lines using western blot and immunofluorescence, relative to colorectal cancer cell lines that have previously demonstrated high LGR5 levels. 3. Establish a biobank of patient-derived HNSCC organoids for future functional studies of α-LGR5 in therapeutic applications.
Results: LGR5 expression was assessed in HNSCC cell lines including SCC-61 (tongue), SCC-15 (tongue), and FaDu (hypopharyngeal), as well as other cancer cell lines using western blotting (see Figure 1). Additionally, high levels of LGR5 were observed using the fluorescently labeled α-LGR5, with a localization pattern consistent with previous findings – minimal cell surface staining, and LGR5 primarily concentrated within intracellular puncta (see Figure 2). Organoids were successfully derived from two patient biopsy samples, albeit with varying success rates; none of the biopsied 'healthy' margin tissues yielded organoids, while only one of the HNSCC samples formed organoids (see Figure 3).
Conclusion: LGR5 continues to emerge as a promising diagnostic and therapeutic target across various cancers. The data from this study suggests that this includes HNSCC in the tongue and hypopharyngeal tissue. Earlier research in the de la Roche lab using α-LGR5 indicates that the LGR5 protein undergoes rapid internalization, accounting for its predominant internalized punctate distribution (doi: https://doi.org/10.1101/2022.09.01.506182). The hypothesis proposes that α-LGR5, as an antibody-drug conjugate (ADC), represents an ideal approach for targeting cancer cells with heightened LGR5 expression, thereby raising the intriguing prospect of a highly effective therapeutic strategy for HNSCC. Nevertheless, further experiments are warranted to assess the efficacy of α-LGR5 as a potential therapeutic agent in humans. With the demonstrated potential of an HNSCC organoid biobank, as indicated by the results of this study, there are substantial opportunities for conducting representative functional experiments to advance α-LGR5 ADCs into clinical studies. Overall, the findings of this project offer significant motivation to continue investigating the potential of α-LGR5 and patient-derived cancer organoids.
Citation Format: Ameer S Basta, Marc de la Roche. Validating novel therapeutic antibodies for targeting head & neck squamous cell malignancies [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_B24.