Prostate tumor OVerexpressed-1 (PTOV1) down-regulates HES1 and HEY1 notch targets genes and promotes prostate cancer progression

Abstract

BackgroundPTOV1 is an adaptor protein with functions in diverse processes, including gene transcription and protein translation, whose overexpression is associated with a higher proliferation index and tumor grade in prostate cancer (PC) and other neoplasms. Here we report its interaction with the Notch pathway and its involvement in PC progression.MethodsStable PTOV1 knockdown or overexpression were performed by lentiviral transduction. Protein interactions were analyzed by co-immunoprecipitation, pull-down and/or immunofluorescence. Endogenous gene expression was analyzed by real time RT-PCR and/or Western blotting. Exogenous promoter activities were studied by luciferase assays. Gene promoter interactions were analyzed by chromatin immunoprecipitation assays (ChIP). In vivo studies were performed in the Drosophila melanogaster wing, the SCID-Beige mouse model, and human prostate cancer tissues and metastasis. The Excel package was used for statistical analysis.ResultsKnockdown of PTOV1 in prostate epithelial cells and HaCaT skin keratinocytes caused the upregulation, and overexpression of PTOV1 the downregulation, of the Notch target genes HEY1 and HES1, suggesting that PTOV1 counteracts Notch signaling. Under conditions of inactive Notch signaling, endogenous PTOV1 associated with the HEY1 and HES1 promoters, together with components of the Notch repressor complex. Conversely, expression of active Notch1 provoked the dismissal of PTOV1 from these promoters. The antagonist role of PTOV1 on Notch activity was corroborated in the Drosophila melanogaster wing, where human PTOV1 exacerbated Notch deletion mutant phenotypes and suppressed the effects of constitutively active Notch. PTOV1 was required for optimal in vitro invasiveness and anchorage-independent growth of PC-3 cells, activities counteracted by Notch, and for their efficient growth and metastatic spread in vivo. In prostate tumors, the overexpression of PTOV1 was associated with decreased expression of HEY1 and HES1, and this correlation was significant in metastatic lesions.ConclusionsHigh levels of the adaptor protein PTOV1 counteract the transcriptional activity of Notch. Our evidences link the pro-oncogenic and pro-metastatic effects of PTOV1 in prostate cancer to its inhibitory activity on Notch signaling and are supportive of a tumor suppressor role of Notch in prostate cancer progression.

PLCε knockdown inhibits prostate cancer cell proliferation via suppression of Notch signalling and nuclear translocation of the androgen receptor

“…These molecules can also be regulated by Notch signalling [23,24], suggesting that PLCε may be involved in the Notch signalling pathway. After silencing PLCε expression, we observed a decrease in Notch1 and Hes1 expression levels in both cell lines tested, which suggests that PLCε may be an upstream regulator of factors with a known critical role in prostate cancer progression [25][26][27].…”

Notch signaling in the prostate: critical roles during development and in the hallmarks of prostate cancer biology

“…Another study showed that Notch signaling inhibited cell invasiveness in prostate cancer; however, this anti-invasive role of Notch was repressed by prostate tumor overexpressed-1 (PTOV1) (Alana et al 2014), an adaptor protein whose expression is significantly increased in prostate cancer (Benedit et al 2001;Santamaria et al 2003). In PTOV1 knockdown prostate epithelial cells, Notch-dependent expression of Hey1 and Hes1 was up-regulated and constitutively active Notch1 receptor attenuated the invasion and anchorage-independent growth of prostate cancer cells (Alana et al 2014).…”

“…In PTOV1 knockdown prostate epithelial cells, Notch-dependent expression of Hey1 and Hes1 was up-regulated and constitutively active Notch1 receptor attenuated the invasion and anchorage-independent growth of prostate cancer cells (Alana et al 2014). …”

“…Although the association of FGF18 in prostate cancer was unclear, two other closely related FGFs, FGF8 and FGF17, were elevated in prostate tumor samples (Heer et al 2004;Valve et al 2001). Moreover, prostate tumor overexpressed-1 (PTOV1), the adapter protein up-regulated in prostate cancer, promotes prostate cancer progression by down-regulation of Notch downstream targets Hes1 and Hey1, indicating a tumor suppressing role of Notch in prostate cancer (Alana et al 2014). Contrarily, numerous reports have also indicated that Notch signaling promotes cell proliferation, prevents apoptosis, augments cell migration and invasion and facilitates cell metastasis, which will be discussed in detail later.…”

Inhibition of Recombining Binding Protein Suppressor of Hairless (RBPJ) Impairs the Growth of Prostate Cancer

“…Inhibition of Notch pathway has been shown to suppress tumorigenesis of prostate cancers [29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49]. Moreover, RBPJ acts downstream of the Notch pathway and has been shown to be essential for a functional activated Notch signaling [13,14,16,17,18,19,20,21].…”