The potential of hydrogel-free tumoroids in head and neck squamous cell carcinoma.

Background: Head and neck malignancy, and in particular squamous cell carcinoma (SCC), is responsible for a significant disease burden globally. The lack of an optimal in vitro model system to accurately recapitulate in vivo response to therapy in HNSCC remains a challenge. The development of patient-derived three-dimensional tumour cultures, or tumoroids, has enabled improved modelling of the tumour microenvironment through simulation of important characteristics such as tumour hypoxia, cell-cell interactions and nutrient diffusion characteristics.

Methods: We performed a comprehensive English-language literature review of current methods of tumoroid development utilising Matrigel and Cultrex Basement Membrane Extract 2 (key terms: tumour organoids, tumoroids, hydrogels, Matrigel, Cultrex, squamous cell carcinoma, head and neck)-two common proprietary murine-derived hydrogels containing extracellular matrix proteins. Nascent literature on the establishment of a novel hydrogel-free platform for tumoroid development as distinct from these existing methods was also explored.

Results: Whilst useful for facilitating cell-matrix interactions and providing a scaffold for three-dimensional cell growth and organisation, murine-derived cell matrix methods were noted to have notable limitations including temperature sensitivity and the medium forming a barrier to analysis of the supernatant. A novel hydrogel-free method of establishing in vitro tumoroid cultures has been subject to experimentation in colorectal but not head and neck malignancy. The absence of a hydrogel provides for the de novo synthesis of extracellular matrix native to the tumour and self-organisation of cells within this scaffold through the use of ultralow attachment plates. This model demonstrates similar structural and physiological properties to native tissue, whilst enabling more accurate biomimicry of the tumour microenvironment for drug testing.

Conclusions: In the absence of prior experimentation on a hydrogel-free method for establishing HNSCC tumoroids, and comparisons between hydrogel and hydrogel-free models, the future development of a comparative protocol encompassing recruitment, collection, processing and analysis represents a valuable opportunity.