Fengming Lan, Qing Qin, Huiming Yu and Xiao Yue
Although glucose metabolism reengineering is a typical feature of various tumors, including glioma, key regulators of glycolytic reprogramming are still poorly understood. The authors sought to investigate whether glycolysis inhibition by microRNA (miR)–448 increases radiosensitivity in glioma cells.
The authors used glioma tissue samples from glioma patients, cells from glioblastoma (GBM) cell lines and normal human astrocyte cells, and subcutaneous tumor–bearing U87 cells in mice to examine the effects of signaling regulation by miR-448 in the response of glioma tissues and cells to radiation treatment. Techniques used for investigation included bioinformatics analyses, biochemical assays, luciferase reporter assays, and establishment of subcutaneous tumors in a mouse model. Glucose consumption, LDH activity, and cellular ATP were measured to determine the ability of glioma cells to perform glycolysis. Expression of HIF-1α was measured as a potential target gene of miR-448 in glycolysis.
miR-448 was detected and determined to be significantly downregulated in both glioma tissues from glioma patients and GBM cell lines. Furthermore, miR-448 acted as a tumor-inhibiting factor and suppressed glycolysis in glioma by negatively regulating the activity of HIF-1α signaling and then interfering with its downstream regulators relative to glycolysis, HK1, HK2, and LDHA. Interestingly, overexpression of miR-448 increased the x-radiation sensitivity of glioma cells. Finally, in in vivo experiments, subcutaneous tumor–bearing U87 cells in a mouse model verified that high expression of miR-448 also enhanced glioma radiosensitivity via inhibiting glycolytic factors.
miR-448 can promote radiosensitivity by inhibiting HIF-1α signaling and then negatively controlling the glycolysis process in glioma. A newly identified miR-448–HIF-1α axis acts as a potentially valuable therapeutic target that may be useful in overcoming radioresistance in glioma treatment.
Jun Dong, Quanbin Zhang, Qiang Huang, Hua Chen, Yuntian Shen, Xifeng Fei, Tianyi Zhang, Yi Diao, Zicheng Wu, Zhenghong Qin, Qing Lan and Xiaosong Gu
Although tissue remodeling plays a crucial role in the tumorigenesis and progression of human gliomas, its mechanisms remain largely uncertain. In the current study, the authors investigated the potential role of human glioma stem cells (hGSCs) in the tissue remodeling of gliomas.
Transgenic nude mice with ubiquitous green fluorescent protein (GFP) expression were obtained by crossing nontransgenic NC athymic nude mice with the GFP transgenic C57BL/6J mice. As a result, GFP was expressed in essentially all tissues in the offspring. Human glioma stem cells were then orthotopically implanted into the GFP nude mice in an effort to assess the hGSC–host brain interactions and thereby elucidate the roles of tissue remodeling during tumorigenesis and progression of human gliomas.
All of the essential tissues in the GFP transgenic nude mice, including the brain, fluoresced green under an excitation light; therefore, tumor remodeling by hGSCs can be unambiguously distinguished from a bright green background composed of adjacent host GFP-expressing components. This technique enabled the authors to address the following concerns: 1) hGSCs were involved in the invasiveness of gliomas and adjacent stroma degradation of the host. 2) An in vivo study demonstrated that cell fusion occurred between hGSCs and host cells. 3) Vasculogenic mimicry—the formation of patterned, tubular networks of vascular channels by transdifferentiated hGSCs—could be observed. 4) Differentiation mimicry—namely, the differentiation direction of hGSCs bearing multidifferentiation potentials—seemed to be decided by the local host cellular microenviroment.
The results of this study indicated that the GFP transgenic nude mice model with GFP expression in essentially all tissues could be obtained by crossing nontransgenic athymic nude mice with transgenic GFP mice. This model should greatly expand our knowledge of glioma-host interactions. The data indicated that hGSCs might play a decisive role in tissue remodeling of gliomas as well.