The expressions of N-myc, cyclin D3, and Wnt10B were downregulated, whereas those of retinoblastoma (RB) and related genes (p107, RB2/p130, p300/CBP, E2F-1, DP-1) as well as others were upregulated.
Overexpression of p21waf1 leads to increased inhibition of E2F-1 phosphorylation and sensitivity to anticancer drugs in retinoblastoma-negative human sarcoma cells.
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.
E2F-1 activity is regulated by a number of proteins, including the retinoblastoma susceptibility gene product, cyclin-dependent kinases, and their inhibitors, proteins that have been implicated in the control of certain developmental processes.
These aberrations may reflect the inactivation of retinoblastoma pathway in these tumors which result in the activation of E2F transcription factors, since TAp73 is a known target of E2F1 gene.
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.
Following the subcloning of the promoter regions into a gene reporter system, we found that at least four promoter haplotypes associated with CCND1, E2F1, HDAC1 and RB1 significantly influenced transcriptional activity in an allele-specific manner.
This transformation was associated with an accelerated rate of androgen-independent LNCaP cell proliferation, resistance to apoptosis, hyperphosphorylation of the mitogen-activated protein kinase extracellular signal-regulated kinase and transcriptional repressor protein retinoblastoma, and increased expression of E2F-1 and other 5'-cap-dependent mRNAs, including the G(1) cyclins, c-myc, and caveolin-1.
Because XP-E cells deficient in the p48 subunit of the damaged DNA-binding protein are impaired in E2F-1-activated transcription, these results also suggest that the (pRb-regulated) transcription factor E2F-1 does not play an essential role in UV-enhanced expression from the CMV-IE promoter.
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.
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.