Development of an efficient method of ex vivo 2*2*2 tumor tissue explant culture to test drug efficacy in head and neck cancer patients

Introduction: Head and neck cancer (HNSCC) is one of the most common cancer types in South Asian Countries and the 6^th common cancer in western countries. Despite of remarkable progress made in the head and neck cancer therapy, an unmet need is there in tailoring the appropriate patient specific therapy due to a variety of treatment options. Our aim was to develop a high-throughput drug screening method using tumor ex-vivo analysis (TEVA) which can predict patient-specific drug response and thus can be employed for personalized treatment.

Materials and Methods: Freshly operated tumor tissue samples from HNSCC patients were received from Soroka Medical Center and implanted in NOD/SCID mice to establish patient-derived xenografts (PDXs). We developed a method that enabled us to cut PDXs into 2*2*2 tissue explants and then treated with clinically relevant drugs in 48 well plates for 24 hours. TMA blocks were prepared and IHC was performed. Parameters, such as Ki67 and TUNEL were chosen to predict the drug response ex vivo and a formulated score was given to each drug based upon those parameters. This was followed by in vivo drug validation in the respective PDX bearing mice. All experiments were done under BGU-IACUC (Ethical number: IL-80-12-2015).

Results and discussion: While optimizing culture conditions, we observed that the tissue explants remain viable for 48hours and retained best tissue structures and signalling pathways for 24 hours. When treated with specific pathways inhibitors for 24 hours, respective signalling pathways were significantly blocked. The system also enabled us to test multiple drugs. Tumor responses to drugs in TEVA and in vivo were correlated, enabling the system to test small molecule inhibitors, monoclonal antibodies and even drug combinations.

Conclusion: Overall, this low cost, fast, relatively simple and efficient 3D tissue-based method can bypass the necessity of drug validation in immune-incompetent PDX-bearing mice, saving significant time and substantially reducing cost and can be used for multiple drug screening to select patient-personalized treatment in near future.