Dr Ueyama has completed his PhD from Okayama University in 1990 and works for Yamaguchi University Medical Scholl in oral and maxillofacial surgern. He is a medical specialist in oral cancer.
The cancer stem cells (CSCs), a small subpopulation of cells in tumor are responsible for the tumor initiation, growth, recurrence and metastasis of cancer, as well as resistance of cancers to drugs or radiotherapy. CSCs are an important target for the development of novel strategies in cancer treatment. However, CSCs-targeted new anti-cancer drug discovery is currently hindered by the lack of easy and reliable methods for isolating, collecting and maintaining sufficient number of CSCs. Here, we examined whether introduction of defined reprogramming factors (Oct4, shp53, Sox2, Klf4, l-Myc and Lin28) into HSC2 oral cancer cells could transform the HSC2 into HSC2 with CSCs properties. Methods: We introduced the defined reprogramming factors into HSC2 oral cancer cells via episomal vectors by electroporation method to generate transfectant cells. We investigated the malignant properties of the transfectant cells by cell proliferation assay, migration assay, wound healing assay, sphere formation assay, chemosensitivity and radiosensitivity assay in vitro; and also examined the tumorigenic potential of the transfectants in vivo. Results: The transfectant cells (HSC2/hOCT3/4-shp53-F, HSC2/hSK, HSC2/hUL, HSC2/hOCT3/4-shp53-F+hSK, HSC2/hOCT3/4-shp53-F+hUL, HSC2/hSK+hUL, HSC2/hOCT3/4-shp53-F+hSK+hUL) displayed a malignant phenotype in culture and form tumors on the back of nude mice more efficiently than parental HSC2 and control HSC2/EGFP transfectant cells. They exhibited increased resistance to chemotherapeutic agents; 5-fluorouracil, cisplatin, docetaxel, trifluorothymidine, zoledronic acid, cetuximab, bortezomib and radiation when compared with HSC2 and HSC2/EGFP. Among all the transfected cells, HSC2/hOCT3/4-shp53-F+hSK+hUL cell containing all of the reprogramming factors showed the most aggressive and malignant properties and presented the highest number of spheres in the culture medium containing human recombinant fibroblast Growth Factor-2 (FGF-2) and epidermal Growth Factor (EGF). Conclusion: These findings suggest that artificial cancer stem cells obtained by the induction of cellular reprogramming may be useful for investigating the acquisition of potential malignancy as well as screening the CSCs-targeting drugs.
Dr. Tomihara received his Ph.D. degree in 2006 from Sapporo Medical University, working on immune gene therapy by adenovirus vector. He then moved to Cancer Therapy and Research Center (CTRC) at The University of Texas Health Science Center at San Antonio (UTHSCSA) to work with Dr. Shin as a post-doctoral fellow. He obtained an assistant professor position in 2013 in the Department of Oral and Maxillofacial Surgery Graduate School of Medicine and Pharmaceutical Sciences for Research, University of Toyama, where he started independent research on cancer immunology.
Cancer is often associated with destruction in both the humoral and cellular immune responses, and this phenomenon has been suggested to be attributed by the alteration of several cell populations. Myeloid derived suppressor cells (MDSC), one of the myeloid lineage cells, has been shown to be accumulated within either the tumor microenvironment or peripheral blood which collates with the impairment of immune response and the promotion of tumor growth. However, this cell type is a heterogeneous cell population that can be altered by type of the tumor and its anatomical location, and the characterization of their function during cancer has not been still fully elucidated. Here, we show that MDSCs are increased in the spleen, bone marrow, peripheral blood and the tumor site in the murine oral squamous cell carcinoma-bearing mice, however, the phenotype and function of the cells from each origin are not consistent. MDSCs in the tumor site, but not in the spleen, bone marrow, and peripheral blood exhibit increased expression of PD-L1 on their cell surface and strong immune suppression against in vitro cocultured T cells through the expression of PD-L1, indicating that MDSCs accumulated in tumor bearing host may not be originally immune suppressive, however, they could be phenotypically and functionally altered by the influence of tumor-derived factors and converted into immune suppressive cells. Our results suggest that targeting MDSCs would be more efficient strategy for cancer treatment in combination with PD-L1 blocking.