ABSTRACT
Understanding the cellular interactions during oral carcinogenesis has the potential to identify novel prognostic and therapeutic targets. This study aimed at investigating the cancer stem cell (CSC)-fibroblast niche interactions using in-vitro dysplastic cell line models developed from different stages of 4NQO-induced oral carcinogenic mice model. The spontaneously transformed epithelial cells (DysMSCTR6, 14 and 16) were developed from three time points (mild/moderate/severe), while two fibroblast cell lines (FibroMSCTR12, 16) were developed from moderate and severe dysplastic tissue. The epithelial (Epcam+/Ck+) and the fibroblast cell lines (Vimentin+/α-SMA+/Ck-) were authenticated and assessment of cells representing progressive grades of dysplastic severity indicated a significant increase in dysplastic marker profile (P < 0.05). Evaluation of the CSC characteristics showed that an increase in expression of Cd133, Cd44, Aldh1a1, Notch1, and Sox2 was accompanied by an increase in migratory (P > 0.05) and colony formation capacity (P > 0.005). Targeting Notch1 (GSI inhibitor PZ0187; 30 µM), showed a significant reduction in cell proliferation capacity (P < 0.05) and in the dysplastic marker profile. Further, Notch1 inhibition resulted in down regulation of Cd133 and Aldh1a 1 (P < 0.05) and a complete abrogation of colony formation ability (P < 0.0001). The effect of niche interactions evaluated using FibroMSCTR12-conditioned media studies, revealed an enrichment of ALDH1A1+ cells (P < 0.05), induction of spheroid formation ability (P < 0.0001) and increased proliferation capacity (3.7 fold; P < 0.005). Although PZ0187 reduced cell viability by â¼40%, was unable to abrogate the conditioned-media induced increase in proliferation capacity completely. This study reports a Notch-1 dependent enrichment of CSC properties during dysplastic progression and a Notch-1 independent dysplastic cell-fibroblast interaction during oral carcinogenesis.
