Characterization Of Tumor Initiating Cells In Esophageal Squamous Cell Carcinoma

Isabela GONZAGA, Instituto Nacional de Câncer, Brazil

1 Programa de Carcinogênese Molecular, Instituto Nacional de Câncer, Rio de Janeiro, Brazil
2 Departamento de Bioquímica, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
3 Departamento de Biofísica, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil

The presence and role of tumor initiating cells (TICs), also known as cancer stem cells, in esophageal squamous cell carcinoma (ESCC) are still poorly understood, mostly because of the lack of good biomarkers for their identification. Therefore, this study aims to isolate and characterize the TICs in ESCC. We first performed a sphere formation assay in order to isolate the possible TICs in four ESCC cell lines, using a stem cell-specific medium in non-adherent conditions. RT-qPCR analysis was performed to evaluate the expression of 26 genes, comparing the spheres with their respective parental cells. To investigate whether the possible TICs presented a re-differentiation capacity and were able to generate a cell population with the same morphological and molecular features of the parental cells, we dissociated the spheres and plated the cells in parental's condition. To ensure that the differential expression of the possible markers is not a consequence of the exposure to the stem cell-specific medium, parental cells were plated in adherent conditions in the presence of this specific medium. All ESCC cell lines were capable of forming spheroids. CXCR4, ITGA6, ABCG2 and NANOG showed an overexpression in this condition and were identified as possible TIC markers in TE1 and TE11, but only CXCR4, ITGA6 and ABCG2 were confirmed in TE13. In the re-differentiation assay, all sphere-derived ESCC cells were capable of forming populations with morphological and gene expression profiles similar to parental cells. Finally, ESCC cells cultured in adherent conditions in the presence of stem cell-specific medium showed ITGA6 upregulation, suggesting that this is not a good TIC marker . In conclusion, our data show that CXCR4 and ABCG2 could be possible markers for TICs in ESCC and must be tested for TIC's population enrichment in xenografic NOD-SCID mouse tumorigenesis assay. Funding sources: CNPq and FAPERJ.