Single-cell transcriptomics reveals cell atlas and identifies cycling tumor cells responsible for recurrence in ameloblastoma.

Ameloblastoma is a benign tumor characterized by locally invasive phenotypes, leading to facial bone destruction and a high recurrence rate. However, the mechanisms governing tumor initiation and recurrence are poorly understood. Here, we uncovered cellular landscapes and mechanisms that underlie tumor recurrence in ameloblastoma at single-cell resolution. Our results revealed that ameloblastoma exhibits five tumor subpopulations varying with respect to immune response (IR), bone remodeling (BR), tooth development (TD), epithelial development (ED), and cell cycle (CC) signatures. Of note, we found that CC ameloblastoma cells were endowed with stemness and contributed to tumor recurrence, which was dominated by the EZH2-mediated program. Targeting EZH2 effectively eliminated CC ameloblastoma cells and inhibited tumor growth in ameloblastoma patient-derived organoids. These data described the tumor subpopulation and clarified the identity, function, and regulatory mechanism of CC ameloblastoma cells, providing a potential therapeutic target for ameloblastoma.

Sox9+ cells are required for salivary gland regeneration after radiation damage via the Wnt/ß-catenin pathway.

Radiotherapy for head and neck cancer can cause serious side effects, including severe damage to the salivary glands, resulting in symptoms such as xerostomia, dental caries, and oral infection. Because of the lack of long-term treatment for the symptoms of xerostomia, current research has focused on finding endogenous stem cells that can differentiate into various cell lineages to replace lost tissues and restore functions. Here, we report that Sox9+ cells can differentiate into various salivary epithelial cell lineages under homeostatic conditions. After ablating Sox9+ cells, the salivary glands of irradiated mice showed more severe phenotypes and the reduced proliferative capacity. Analysis of online single-cell RNA-sequencing data reveals the enrichment of the Wnt/ß-catenin pathway in the Sox9+ cell population. Furthermore, treatment with a Wnt/ß-catenin inhibitor in irradiated mice inhibits the regenerative capability of Sox9+ cells. Finally, we show that Sox9+ cells are capable of forming organoids in vitro and that transplanting these organoids into salivary glands after radiation partially restored salivary gland functions. These results suggest that regenerative therapy targeting Sox9+ cells is a promising approach to treat radiation-induced salivary gland injury.