Identification and characterization of CD133+CD44+ cancer stem cells from human laryngeal squamous cell carcinoma cell lines

Background: Laryngeal squamous cell carcinoma ranks second among head and neck squamous-cell carcinomas. Cancer stem cells can support cancer growth and malignant behavior. Therefore, cancer stem cells isolated from laryngeal squamous cell carcinoma tissue could be used to investigate the initiation, progression, and treatment strategies of this cancer. Methods: We isolated CD133-CD44-, CD133-CD44+, CD133+CD44- and CD133+CD44+ cell populations from laryngeal squamous-cell carcinoma cell lines Hep2 and TU-177 by magnetic-activated cell sorting. Sphere formation, cell proliferation, migration, invasion, colony formation, resistance to radio- and chemotherapy, and in vivo tumorigenicity of these populations were evaluated. Moreover, we investigated the expression of the stem-cell markers (sex determining region Y)-box 2 (SOX2) and octamer-binding transcription factor 4 (OCT4) in CD133-CD44-, CD133-CD44+, CD133+CD44-, CD133+CD44+ cell populations and parental Hep2 and TU-177 cells. Results: As compared with CD133-CD44-, CD133-CD44+, CD133+CD44- populations and parental cells, CD133+CD44+ cells showed higher cell viability, migration and invasive capability and colony formation ability as well as stronger resistance to cisplatin and irradiation. Moreover, levels of SOX2 and OCT4 and tumorigenicity in nude mice were greater in CD133+CD44+ Hep2 and TU-177 cells than other cell populations and parental cells. Conclusion: The CD133+CD44+ population of laryngeal squamous-cell carcinoma Hep2 and TU-177 cells have stem cell properties and showed more malignant features than CD133+CD44- and CD133-CD44+ cell populations. CD133+CD44+ cancer stem cells may be a promising target for developing anticancer drugs and treatment strategies for laryngeal squamous cell carcinoma.