Phenotype transition of fibroblasts incorporated into patient-derived oral carcinoma organoids

Objective: Cancer-associated fibroblasts (CAFs) are abundantly infiltrated in oral squamous cell carcinoma (OSCC), but the contact-dependent mechanisms that regulate CAFs phenotype in precursor cells, such as paracancerous fibroblasts (PFs), remain unclear. Here, a fibroblast-attached organoid (FAO) model was initiated to determine phenotype transition of fibroblasts triggered by contact with OSCC.

Material and methods: Organoids and fibroblasts were generated using OSCC and adjacent tissues. Cell-clusters containing fibroblasts and tumour cells were aggregated to allow for FAOs expansion. Immunoblotting assay was performed to compare expression of Notch intracellular domain (NICD) in CAFs and PFs. Colony formation assay was employed to evaluate morphological activation of fibroblasts.

Results: Compared to traditional 3D co-culture, FAOs better modulated the spatial distribution of fibroblasts with tumour nests. The presence of CAFs with multiple branches was stably observed in FAOs during serial passage. Incorporation with organoids promoted the ability of PFs to form multiple branches. Immunoblotting assay confirmed higher NICD level in CAFs than PFs. Treatment with Notch Inhibitor, N-[N-(3, 5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (i.e. DAPT) blocked morphological activation of fibroblasts incorporated into FAO.

Conclusion: We developed a robust strategy to study contact-dependent mechanisms underlying tumour-stromal interaction, and suggested that Notch activity contributes to biogenesis of OSCC-associated fibroblasts.