Blocking eIF5A Modification in Cervical Cancer Cells Alters the Expression of Cancer-Related Genes and Suppresses Cell Proliferation

Abstract

Cancer etiology is influenced by alterations in protein synthesis that are not fully understood. In this study, we took a novel approach to investigate the role of the eukaryotic translation initiation factor eIF5A in human cervical cancers, where it is widely overexpressed. eIF5A contains the distinctive amino acid hypusine, which is formed by a posttranslational modification event requiring deoxyhypusine hydroxylase (DOHH), an enzyme that can be inhibited by the drugs ciclopirox and deferiprone. We found that proliferation of cervical cancer cells can be blocked by DOHH inhibition with either of these pharmacologic agents, as well as by RNA interference–mediated silencing of eIF5A, DOHH, or another enzyme in the hypusine pathway. Proteomic and RNA analyses in HeLa cervical cancer cells identified two groups of proteins in addition to eIF5A that were coordinately affected by ciclopirox and deferiprone. Group 1 proteins (Hsp27, NM23, and DJ-1) were downregulated at the translational level, whereas group 2 proteins (TrpRS and PRDX2) were upregulated at the mRNA level. Further investigations confirmed that eIF5A and DOHH are required for Hsp27 expression in cervical cancer cells and for regulation of its key target IκB and hence NF-κB. Our results argue that mature eIF5A controls a translational network of cancer-driving genes, termed the eIF5A regulon, at the levels of mRNA abundance and translation. In coordinating cell proliferation, the eIF5A regulon can be modulated by drugs such as ciclopirox or deferiprone, which might be repositioned to control cancer cell growth.

Translational Downregulation of HSP90 Expression by Iron Chelators in Neuroblastoma Cells

“…Differently, upon treatment with CPX no induction of HSP70 proteins could be observed along with inhibition of HSP90, pointing out a mechanism of CPX action different from conventional HSP90 inhibitors and rendering it particularly interesting for therapy. In line with this, the recent work of Mémin et al (2014) described that CPX resulted in hypusyl-eIF5A-mediated translational downregulation of yet another member of the HSP group, HSP27. Our data corroborate these findings, although at 24 hours we detected CPX-mediated inhibition of HSP27 both at the transcriptome and translatome levels (data not shown).…”

“…Hence, G 0 /G 1 arrest might result from CPX-mediated inhibition of DOHH. Interestingly, CPX exerted inhibition of DOHH in HUVEC and HeLa cells in a concentration-dependent manner with IC 50 values of 5 and 6.25 mM, respectively (Clement et al, 2002;Mémin et al, 2014), coincident with the dose threshold region of CPX effects observed in CHP134 cells. In addition to DOHH, the G 1 arrest induced by CPX could be mediated by multiple mechanisms involving cyclin D1, CDK2, RB1, and CDK inhibitor p21 CIP1/WAF1 (Zhou et al, 2010).…”

“…This could be due to the capacity to target only a subset of iron-dependent proteins at lower concentrations, while for inhibiting other proteins higher concentrations of CPX could be needed. Several enzymes have been reported to be cellular targets for CPX, including ribonucleotide reductase (Eberhard et al, 2009) and DOHH (Clement et al, 2002;Mémin et al, 2014). Ribonucleotide reductase is a rate-limiting enzyme in DNA synthesis responsible for converting nucleoside diphosphates to deoxynucleoside diphosphates.…”

“…Hypusination of eIF5A is essential for its activity in promoting cell proliferation and survival (Park, 2006;Caraglia et al, 2013). CPX has been reported to inhibit DOHH both in biochemical (Csonga et al, 1996) and cellular assays (Clement et al, 2002;Mémin et al, 2014). Moreover, inhibition of DOHH was shown to coincide with proliferative arrest in the late G 1 phase of cell cycle (Hanauske-Abel et al, 1994).…”

Eukaryotic Translation Initiation Factor 5A (EIF5A) Regulates Pancreatic Cancer Metastasis by Modulating RhoA and Rho-associated Kinase (ROCK) Protein Expression Levels

“…In bacteria, EF-P was shown to control the expression of proteins with motifs other than polyproline tracts (36). Furthermore, a recent report by Memin et al (57) showed that polyproline stretches were not enriched in DOHH-regulated proteins in cervical cancer cells. In fact, RhoA does not contain a polyproline tract, but is regulated by eIF5A (Figs.…”