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.

CD133 (prominin-1), a 5-transmembrane glycoprotein, has recently been considered to be an important marker that represents the subset population of cancer stem-like cells. Herein we report the isolation of CD133-positive cells (LC-CD133⁺) and CD133-negative cells (LC-CD133⁻) from tissue samples of ten patients with non-small cell lung cancer (LC) and five LC cell lines. LC-CD133⁺ displayed higher Oct-4 expressions with the ability to self-renew and may represent a reservoir with proliferative potential for generating lung cancer cells. Furthermore, LC-CD133⁺, unlike LC-CD133⁻, highly co-expressed the multiple drug-resistant marker ABCG2 and showed significant resistance to chemotherapy agents (i.e., cisplatin, etoposide, doxorubicin, and paclitaxel) and radiotherapy. The treatment of Oct-4 siRNA with lentiviral vector can specifically block the capability of LC-CD133⁺ to form spheres and can further facilitate LC-CD133⁺ to differentiate into LC-CD133⁻. In addition, knock-down of Oct-4 expression in LC-CD133⁺ can significantly inhibit the abilities of tumor invasion and colony formation, and increase apoptotic activities of caspase 3 and poly (ADP-ribose) polymerase (PARP). Finally, in vitro and in vivo studies further confirm that the treatment effect of chemoradiotherapy for LC-CD133⁺ can be improved by the treatment of Oct-4 siRNA. In conclusion, we demonstrated that Oct-4 expression plays a crucial role in maintaining the self-renewing, cancer stem-like, and chemoradioresistant properties of LC-CD133⁺. Future research is warranted regarding the up-regulated expression of Oct-4 in LC-CD133⁺ and malignant lung cancer.