In addition, miR-598 was found to promote cell apoptosis and inactivate the protein kinase B (AKT) pathway in RB. miR-598 suppressed RB cell viability and metastasis through inhibiting E2F1 and inactivating AKT pathway, which may provide a new perspective for RB treatment.
E2F1 and retinoblastoma (RB) tumor-suppressor protein not only regulate the periodic expression of genes important for cell proliferation, but also localize to DNA double-strand breaks (DSBs) to promote repair.
Retinoblastoma is a pediatric solid tumor of the retina activated upon homozygous inactivation of the tumor suppressor <i>RB1</i> VCN-01 is an oncolytic adenovirus designed to replicate selectively in tumor cells with high abundance of free E2F-1, a consequence of a dysfunctional RB1 pathway.
Here we illustrate the usefulness of the dual luciferase reporter assay to detect E2F-mediated transcriptional activity upon overexpression of E2F1 in cultured cells as readout for RB status and function.
Immunoprecipitation assay and ChIP-quantitative PCR results showed that FGF9-induced Rb phosphorylation led to the dissociation of Rb-E2F1 complexes and thereby enhanced the transactivations of E2F1 target genes, Cyclin D1, Cyclin E1 and Cyclin A1.
Additionally, identification of protumorigenic transcriptional networks specific to RB loss that were validated in clinical samples demonstrated the ability of RB loss to differentially reprogram E2F1 in human cancers.
These promoter regions are known to be bound by the E2F family proteins (E2F-1 to E2F-8) and retinoblastoma (RB) family proteins (RB1, p107, and p130), among which E2F-4 and p130 were strongly up-regulated in HSP27-knockdown cells.
This holistic approach identified E2F1, a known mediator of the Rb tumor suppressor, as a transcriptional collaborator of EZH2 in castration-resistant prostate cancer.
We established a gene expression signature of Rb loss-of-function (RBsig) by identifying genes correlated with E2F1 and E2F2 expression in breast cancers within The Cancer Genome Atlas.
A knock-in mutation of the ATM phosphorylation site on E2F1 (S29A) prevents the interaction between E2F1 and TopBP1 and recruitment of RB, E2F1, and BRG1 to DSBs.
Studies on Radiation Therapy Oncology Group tissue samples have identified aberrant expression of p53, MDM2 (an E3 ubiquitin ligase that targets p53 for proteosomal degradation), and p16 (an upstream regulator of retinoblastoma and hence E2F1 in prostate cancer); abnormal expression of these biomarkers has been associated with clinical outcome after radiotherapy ± androgen deprivation therapy.
Observation of a direct interaction of retinoblastoma (Rb) and E2F1 proteins with RecQL4 promoter suggests that Rb-E2F1 pathway may regulate RecQL4 expression.
At the protein level, prolonged down-regulation of E2F-1 and proliferating cell nuclear antigen (PCNA), sustained expression of p21(WAF1/CIP1) and dephosphorylation of retinoblastoma (Rb) occurred in the sensitive cells.
Furthermore, a consequence of HMDB-induced CEBPD expression was linked with E2F1 and retinoblastoma (RB), which discloses the scenario of CEBPD, E2F1, and RB bindings and transcriptional regulation on the promoters of proapoptotic genes, PPARG2 and GADD153.
Restoration of Rb function led to the association of Rb/E2F1 repressor complexes with ICOVIR-5 ectopic E2F1 promoter and subsequent down-modulation of E1A, dramatically impairing adenoviral replication.