Identification of a novel p65-p68 loop: A crucial determinant for p68 gene regulation in oncogenesis

DEAD-box RNA helicase DDX5 (p68), located on chromosome 17, specifically at the 17q23.3 region), is overexpressed in most of the cancers, including colorectal cancer (CRC) and glioma, thereby gaining prominence as a potential biomarker. There is a paucity of research on the mechanisms of p68 gene regulation at the genetic level. RelA, (p65), belonging to the NF-κB signaling pathway plays a diversified role in accelerating oncogenesis. Here, we report for the first time a novel transcriptional positive feedback mechanism between p65 and p68 that drives oncogenesis in CRC and glioma. Using bioinformatics analysis, chromatin immunoprecipitation (ChIP), and luciferase reporter assays, we identified functional NF-κB binding sites in the p68 promoter region and demonstrated that p65 upregulates p68 expression. Functionally, increased p68 expression was associated with enhanced proliferation, migration, and invasion, established through in vitro as well as in vivo studies in glioma and CRC. Furthermore, the pharmacological inhibition of IKK (outside of the loop) via Bay-11 leads to the suppression of the "p65-p68 loop" and their oncogenic phenotypes. However, the analysis of patient-derived tumor samples revealed a positive correlation between p65 and p68, underscoring their clinical relevance. Hence, our findings elucidate novel transcriptional feedback "p65-68 loop" and its therapeutic potential in CRC and glioma.