Purpose: Oral squamous cell carcinoma (OSCC), like many solid tumors, contains a heterogeneous population of cancer cells. Recent data suggest that a rare subpopulation of cancer cells, termed cancer stem cells (CSC), is capable of initiating, maintaining, and expanding the growth of tumor. Identification and characterization of CSC from OSCC facilitates the monitoring, therapy, or prevention of OSCC. Experimental Design: We enriched oral cancer stem-like cells (OC-SLC) through sphere formation by cultivating OSCC cells from established OSCC cell lines or primary cultures of OSCC patients within defined serum-free medium. Differential expression profile of stemness genes between enriched OC-SLC and parental OSCC was elucidated. Furthermore, immunohistochemical staining of stemness markers on OSCC patient tissues was examined to evaluate the association between stemness genes and prognosis of OSCC. Results: Enriched OC-SLC highly expressed the stem/progenitor cell markers and ABC transporter gene (Oct-4, Nanog, CD117, Nestin, CD133, and ABCG2) and also displayed induced differentiation abilities and enhanced migration/invasion/malignancy capabilities in vitro and in vivo. Elevated expression of CD133 was shown in the enriched OC-SLC from OSCC patients' tumors. Positive correlations of Oct-4, Nanog, or CD133 expression on tumor stage were shown on 52 OSCC patient tissues. Kaplan-Meier analyses exhibited that Nanog/Oct-4/CD133 triple-positive patients predicted the worst survival prognosis of OSCC patients. Conclusion: We enriched a subpopulation of cancer stem-like cell from OSCC by sphere formation. The enriched OC-SLC possesses the characteristics of both stem cells and malignant tumors. Additionally, expression of stemness markers (Nanog/Oct-4/CD133) contradicts the survival prognosis of OSCC patients.

ALDH1þ CD44 þ cells are putative tumor-initiating cells (TIC) in head and neck squamous cell carcinomas (HNC). miR-145 regulates tumorigenicity in various cancers but the breadth of its mechanistic contributions and potential therapeutic applications are not completely known. Here, we report that ALDH1 þ CD44 þ -HNC cells express reduced levels of miR145. SPONGE-mediated inhibition of miR-145 (Spg-miR145) was sufficient to drive tumor-initiating characteristics in non-TICs/ALDH1 À CD44-negative HNC cells. Mechanistic analyses identified SOX9 and ADAM17 as two novel miR145 targets relevant to this process. miR-145 expression repressed TICs in HNC in a manner associated with SOX9 interaction with the ADAM17 promoter, thereby activating ADAM17 expression. Notably, the SOX9/ADAM17 axis dominated the TIC-inducing activity of miR-145. Either miR-145 suppression or ADAM17 overexpression in non-TICs/ALDH1À CD44 À -HNC cells increased expression and secretion of interleukin (IL)-6 and soluble-IL-6 receptor (sIL-6R). Conversely, conditioned medium from SpgmiR145-transfected non-TICs/ALDH1 À CD44 À -HNC cells was sufficient to confer tumor-initiating properties in non-TICs/ALDH1À CD44 À -HNC and this effect could be abrogated by an IL-6-neutralizing antibody. We found that curcumin administration increased miR-145 promoter activity, thereby decreasing SOX9/ADAM17 expression and eliminating TICs in HNC cell populations. Delivery of lentivral-miR145 or orally administered curcumin blocked tumor progression in HNC-TICs in murine xenotransplant assays. Finally, immunohistochemical analyses of patient specimens confirmed that an miR-145 low /SOX9 high /ADAM17 high phenotype correlated with poor survival. Collectively, our results show how miR-145 targets the SOX9/ADAM17 axis to regulate TIC properties in HNC, and how altering this pathway may partly explain the anticancer effects of curcumin. By inhibiting IL-6 and sIL-6R as downstream effector cytokines in this pathway, miR-145 seems to suppress a paracrine signaling pathway in the tumor microenvironment that is vital to maintain TICs in HNC. Cancer Res; 73(11); 3425-40. Ó2013 AACR.

These data indicate that cancer stem-like properties were expanded during the acquisition of cisplatin resistance in OSCC. Clinically, oral cancer stemness markers (Oct4 and Nanog) overexpression may promote the OSCC's recurrence to resist cisplatin.