Activation of Wnt signalling reduces the population of cancer stem cells in ameloblastoma

Objectives The treatment of ameloblastoma, an odontogenic epithelial tumour destroying jawbone, mainly depends on radical destructive resections. Other therapeutic options are limited by the characteristics of ameloblastoma, such as high recurrence rates and resistance to radiation and chemotherapy, which implies possible existence of cancer stem cells (CSCs) in ameloblastoma. Here, we identified a putative CSC population in immortalized and primary human ameloblastoma cells and examined possible therapeutic reagents to reduce the CSC population. Methods We investigated subpopulations of AM‐1 cell line and human ameloblastoma cells using immunocytochemistry and flow cytometry and the effects of Wnt signalling activators on the 2‐ and 3‐dimensional cultured ameloblastoma cells using molecular biological analyses. Result Among heterogenous ameloblastoma cells, small‐sized and round‐shaped cells were found to be proliferative and expressed a marker of dental epithelial stem cells, SRY‐box 2 (Sox2). Exogenous activation of Wnt signalling using glycogen synthase kinase 3β inhibitors, lithium chloride (LiCl) and valproic acid (VPA), increased the cell size and decreased proliferation of cells and expression of Sox2 in 2 dimensionally cultured AM‐1 and human primary ameloblastoma cells. Furthermore, the growth of 3 dimensionally cultured AM‐1 cells as suspended or embedded in gel was suppressed by treatment with Wnt signalling activators, VPA and CHIR99021, or antibodies to sclerostin, an antagonist of Wnt signalling. Conclusion We suggest that Wnt signalling activators are potential drug candidates to suppress CSCs in ameloblastoma.
Ameloblastoma, a benign tumour of the odontogenic epithelium, presents significant recurrence rates and resistance to radiotherapy and chemotherapy, which compel patients to undergo radical resections, potentially causing surgical morbidity. In this study, we found that the exogenous activation of Wnt signalling using antibody (α‐SOST antibody) or chemicals (LiCl, VPA or CHIR9902) increases β‐catenin (β‐cat) in ameloblastoma, leading to an increase in β‐cathigh and Sox2‐ cells and decrease in β‐catlow and Sox2+ cells, the putative cancer stem cells (CSCs). This change of sub‐population in ameloblastoma results in the suppression of spheroid‐forming activity and invasiveness. The results suggest that Wnt signalling activators may serve as potential drug candidates to suppress CSCs in ameloblastoma.