Preclinical Head and Neck Squamous Cell Carcinoma Models for Combined Targeted Therapy Approaches

Simple Summary Head and neck squamous cell carcinoma are characterized by a high degree of inter- and intratumoral heterogeneity. Well-characterized preclinical models represent the heterogeneity of this disease and enable the development of innovative therapeutic concepts. The present work dealt with the establishment of patient-individual tumor models to explore new treatment approaches for HNSCC patients and to identify suitable biomarkers for predicting treatment response. In this study, tumor specimens from advanced cancers of the oral cavity, hypopharynx, and larynx were used to establish individual tumor models. These novel cell lines were used to apply different combinations of strategies, preclinically, and to overcome intrinsic resistance mechanisms. This study aimed to refine combined targeted approaches on well-characterized, low-passage tumor models. Upon in vivo xenografting in immunodeficient mice, three cell lines from locally advanced or metastatic HNSCC were established. Following quality control and basic characterization, drug response was examined after therapy with 5-FU, Cisplatin, and cyclin-dependent kinase inhibitors (abemaciclib, THZ1). Our cell lines showed different in vitro growth kinetics, morphology, invasive potential, and radiosensitivity. All cell lines were sensitive to 5-FU, Cisplatin, and THZ1. One cell line (HNSCC48 P0 M1) was sensitive to abemaciclib. Here, Cyto-FISH revealed a partial CDKN2a deletion, which resulted from a R58* mutation. Moreover, this cell line demonstrated chromosome 12 polysomy, accompanied by an increase in CDK4-specific copy numbers. In HNSCC16 P1 M1, we likewise identified polysomy-associated CDK4-gains. Although not sensitive to abemaciclib per se, the cell line showed a G1-arrest, an increased number of acidic organelles, and a swollen structure. Notably, intrinsic resistance was conquered by Cisplatin because of cMYC and IDO-1 downregulation. Additionally, this Cisplatin-CDKI combination induced HLA-ABC and PD-L1 upregulation, which may enhance immunogenicity. Performing functional and molecular analysis on patient-individual HNSCC-models, we identified CDK4-gains as a biomarker for abemaciclib response prediction and describe an approach to conquer intrinsic CDKI resistance.

Automated summary

This study established patient-individual tumor models for head and neck squamous cell carcinoma (HNSCC) and identified CDK4-gains as a biomarker for predicting the response to abemaciclib treatment. The study also proposed an approach to overcome intrinsic resistance to cyclin-dependent kinase inhibitors (CDKIs).