Hypoxia exerts a profound impact on diverse aspects of cancer biology. Increasing evidence has revealed novel functions of hypoxia in cancer cell epigenomics, epitranscriptomics, metabolism, and intercellular communication, all hotspots of cancer research. Several drugs have been developed to target intratumoral hypoxia and have entered clinical trials to treat refractory tumors. However, direct targeting of hypoxia signaling still has limitations in the clinic with regard to cancer progression and resistance to therapy. Comprehensive understanding of the molecular mechanisms by which hypoxia reshapes tumors and their microenvironment, as well as how tumor cells adapt to and thrive in hypoxic conditions, will therefore continue to be a focus of cancer research and will provide new directions for hypoxic tumor treatment.
Gliomas are the most common form of primary brain tumor in the adult central nervous system. Altered expression and prognostic value of transmembrane protein 97 (TMEM97) has been recently reported in different types of human tumors. However, the association of TMEM97and glioma is poorly defined. Here, we reported that TMEM97 was significantly increased in glioma tissues compared to non-tumorous brain tissues. Furthermore, TMEM97 levels were progressively increased with increasing histologic tumor grade in glioma. Higher TMEM97 expression level was correlated with shorter survival time of patients with glioma. Downregulation of TMEM97 through RNA interference inhibited cell proliferation and G1/S transition in two glioma cell lines, U87 and U373. More importantly, TMEM97 silencing induced a significant decrease in the expression of G1/S transition key regulators, cyclin D1, cyclin E, CDK2, and CDK4. Additionally, downregulation of TMEM97 in glioma cells notably repressed cell migration and cell invasion. Further analysis suggested that the decreased invasion was associated with alterations in EMT markers, including E-cadherin, β-catenin, and Twist. Since expression of TMEM97 seems to be associated with the oncogenic potential of glioma, and suppression of its expression can inhibit cancer cell growth and metastasis, TMEM97 may be a potential therapeutic target in human glioma.
F‐box and WD repeat domain‐containing 7 (FBW7) is a SCF‐type E3 ubiquitin ligase targeting a multitude of oncoproteins for degradation. Acting as one of the most important tumor suppressors, it is frequently inactivated in various tumors. In this study we aimed to evaluate the relationship of FBW7 with glioma pathology and prognosis, and examine its effect in glioma malignancies and temozolomide (TMZ)‐based therapy. Clinical tissues and TCGA database analysis revealed that FBW7 expression was correlated inversely with glioma histology and positively with patient survival time. Lentivirus transfection‐induced FBW7 overexpression significantly suppressed proliferation, invasion and migration of U251 and U373 cells, whereas knockdown of FBW7 by targeted shRNA promoted proliferation, invasion and migration of glioma cells. Most importantly, the expression level of FBW7 was found to affect the 50% inhibitory concentration (IC50) of U251 and the TMZ‐resistant variant. Combining TMZ with FBW7 overexpression notably increased the cytotoxicity compared to TMZ treatment alone, which was conversely attenuated by FBW7 knockdown. Moreover, flow cytometry (FC) analysis showed overexpression of FBW7, TMZ or the combination‐increased proportion of G2/M arrest and the apoptotic rate, whereas FBW7 inhibition reduced G2/M arrest and apoptosis in U251 cells. Finally, mechanistic study found that FBW7 overexpression downregulated Aurora B, Mcl1 and Notch1 levels in a time‐dependent pattern and this expressional suppression was independent of TMZ. These findings collectively demonstrate the critical role of FBW7 as a prognostic factor and a potential target to overcome chemoresistance of glioblastoma.
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