ABSTRACT
RUNX1T1 has been found to be mutated in different cancers such as prostate, lung, colon, and breast cancer. A recent computational study involving the TCGA database of glioma patients found RUNX1T1 as one of the downregulated driver genes associated with poor overall survival of glioma patients. Hypoxia-inducible factor 1α (HIF1α) is upregulated in glioma and has been associated with the severity and drug resistance of glioma. Previously, we have shown that RUNX1T3 degrades HIF1α affecting the proliferation of leukemia cells. We hypothesize that RUNX1T1 might be associated with the growth and development of glioma through the regulation of HIF1α. We have evaluated the expression level of RUNX1T1 at different stages of glioma and the effect of RUNX1T1 on the proliferation and invasiveness of glioblastoma cells in vitro. We further looked at the effect of RUNX1T1 on the expression and stability of HIF1α in vitro. Expression of RUNX1T1 was significantly downregulated, both at RNA and protein levels in glioma samples as studied by quantitative real-time polymerase chain reaction and immunohistochemistry. While expression of HIF1α was higher in glioma tissues compared with its level in the normal brain. In vitro studies demonstrated that RUNX1T1 interacted with HIF1α and recruited HIF1α modification factor such as PHD2 and GSK3ß causing hydroxylation of HIF1α following ubiquitination by FBW7. RUNX1T1 led to the degradation of HIF1α and decreased proliferation/invasiveness of glioblastoma cell lines. Further, RUNX1T1 increased the effectiveness of temozolomide (TMZ), a conventional glioma drug toward glioblastoma cell lines. This study indicates that downregulation of RUNX1T1 might play an important role in the severity and development of glioma.
Subject(s)
Brain Neoplasms/pathology , Glioma/pathology , Hypoxia-Inducible Factor 1, alpha Subunit/metabolism , RUNX1 Translocation Partner 1 Protein/genetics , Adult , Aged , Aged, 80 and over , Brain Neoplasms/drug therapy , Brain Neoplasms/genetics , Cell Line, Tumor , Cell Proliferation/genetics , Female , Gene Expression Regulation, Neoplastic , Glioblastoma/genetics , Glioblastoma/pathology , Glioma/drug therapy , Glioma/genetics , Humans , Hydroxylation , Hypoxia-Inducible Factor 1, alpha Subunit/genetics , Male , Middle Aged , Protein Stability , RUNX1 Translocation Partner 1 Protein/metabolism , Temozolomide/pharmacologyABSTRACT
The oncogenic potential of Apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3G (APOBEC3G) was recently appreciated by the finding that revealed its ability to downregulate Kruppel-like factor 4 (KLF4) gene translation through its affinity for 3'UTR of KLF4 mRNA. Keeping in view the fact that KLF4 is known to repress apoptosis antagonizing transcription factor (AATF) gene expression, the present study employed stem cells as archetype model to explore the effect of APOBEC3G over-expression upon AATF gene expression within these cells as well as on the genes involved in oncogenic transformation. Such a study revealed that APOBEC3G had the ability to bind AATF mRNA within its third exon to facilitate the generation of truncated 23 kDa AATF translation product which, in turn, had the inherent capacity to be the crucial mediator of APOBEC3G induced oncogenic transformation within such cells.
