Discovery of CX-5461, the First Direct and Selective Inhibitor of RNA Polymerase I, for Cancer Therapeutics

Haddach, Mustapha; Schwaebe, Michael K.; Michaux, Jerome; Nagasawa, Johnny; O’Brien, Sean; Whitten, Jeffrey P.; Pierre, Fabrice; Kerdoncuff, Pauline; Darjania, Levan; Stansfield, Ryan; Drygin, Denis; Anderes, Kenna; Proffitt, Chris; Bliesath, Josh; Siddiqui‐Jain, Adam; Omori, May; Huser, Nanni; Rice, William G.; Ryckman, David M.

doi:10.1021/ml300110s

Cited by 126 publications

(112 citation statements)

References 21 publications

Supporting

Mentioning

109

Contrasting

Unclassified

Order By: Relevance

“…Most importantly, CX-5461 single-agent therapy in PDX AML significantly reduced the leukemic load Figure 7I). Together, these data significantly extend the earlier study of CX-5461 in a xenografted human cell line, MV4-11 AML, 16 and provide compelling evidence of the therapeutic potential of pharmacologic inhibition of Pol I transcription in human AML, mediated in part by reducing the LIC population and suppression of the clonogenic potential.…”

Section: Org Fromsupporting

confidence: 70%

“…To support our findings that the antileukemic effect of CX-5461 is due to on-target inhibition of Pol I transcription, 7 AML cell lines were tested for their sensitivity to 2 additional Pol I inhibitors, BMH-21 14 and low-dose ActD, 15 and an inactive compound (CX-5447), which is structurally similar to CX-5461. 7,16 Both BMH-21 and ActD decreased cell viability after 48 hours in 7 AML cell lines with the level of sensitivity broadly correlating with that of CX-5461 ( Figure 3F). As expected, CX-5447 at equivalent concentrations to efficacious doses of CX-5461 did not decrease cell viability in any of the 7 AML cell lines (supplemental Figure 4A), nor altered Pol I transcription (supplemental Figure 4B; representative cell lines SHI-1 and KG-1 shown).…”

Section: Aml Cells Are Highly Sensitive To Inhibition Of Pol I Transcmentioning

confidence: 79%

See 1 more Smart Citation

Inhibition of Pol I transcription treats murine and human AML by targeting the leukemia-initiating cell population

Hein

Cameron

Hannan

et al. 2017

Blood

Self Cite

View full text Add to dashboard Cite

Key Points• Inhibition of RNA Pol I by CX-5461 treats aggressive AML and outperforms standard chemotherapy regimens.• CX-5461 induces p53-dependent apoptosis, p53-independent cell-cycle defects and differentiation, and reduces LICs.Despite the development of novel drugs, the prospects for many patients with acute myeloid leukemia (AML) remain dismal. This study reveals that the selective inhibitor of RNA polymerase I (Pol I) transcription, CX-5461, effectively treats aggressive AML, including mixed-lineage leukemia-driven AML, and outperforms standard chemotherapies. In addition to the previously characterized mechanism of action of CX-5461 (ie, the induction of p53-dependent apoptotic cell death), the inhibition of Pol I transcription also demonstrates potent efficacy in p53null AML in vivo. This significant survival advantage in both p53WT and p53null leukemic mice treated with CX-5461 is associated with activation of the checkpoint kinases 1/2, an aberrant G2/M cell-cycle progression and induction of myeloid differentiation of the leukemic blasts. The ability to target the leukemic-initiating cell population is thought to be essential for lasting therapeutic benefit. Most strikingly, the acute inhibition of Pol I transcription reduces both the leukemic granulocyte-macrophage progenitor and leukemia-initiating cell (LIC) populations, and suppresses their clonogenic capacity. This suggests that dysregulated Pol I transcription is essential for the maintenance of their leukemia-initiating potential. Together, these findings demonstrate the therapeutic utility of this new class of inhibitors to treat highly aggressive AML by targeting LICs. (Blood. 2017;129(21):2882-2895

show abstract

Section: Org Fromsupporting

confidence: 70%

Section: Aml Cells Are Highly Sensitive To Inhibition Of Pol I Transcmentioning

confidence: 79%

Inhibition of Pol I transcription treats murine and human AML by targeting the leukemia-initiating cell population

Hein

Cameron

Hannan

et al. 2017

Blood

Self Cite

View full text Add to dashboard Cite

show abstract

“…Ribosomal RNA is transcribed by RNA Pol I, which is not inhibited by α-Amanitin (Bensaude, 2011), and our experiments using EU (Figure 3B) do not distinguish between RNA polymerases. We therefore set out to revisit the roles of DNA replication and RNA transcription during mid-to-late zygote development using specific small molecule inhibitors added at 5 hpi: Aphidicolin, for DNA replication, α-Amanitin for RNA Pol II-mediated transcription and CX-5461 (Bywater et al, 2012; Drygin et al, 2011; Haddach et al, 2012) for RNA Pol I-mediated transcription. Of note, activity of both RNA Pol I and II has been detected indirectly in zygotes using specific promoter-driven reporter plasmids (Nothias et al, 1996).…”

Section: Resultsmentioning

confidence: 99%

“…Moreover, we found that nascent 18S rRNA, assessed as above by quantification of FISH signal in the PNs, is drastically reduced in both mPN and fPN in Hira mutant embryos at 10 hpi (Figure 4C). Thus, fixation procedures that are suboptimal for studying the nucleolus (Haukenes and Kalland, 1998), lower sensitivity RNA FISH protocols and the lack of specific RNA Pol I inhibitors until recently (Bywater et al, 2012; Drygin et al, 2011; Haddach et al, 2012) may all have contributed to the idea that rRNA transcription is either absent or irrelevant in the zygote.…”

Section: Resultsmentioning

confidence: 99%

Hira-Mediated H3.3 Incorporation Is Required for DNA Replication and Ribosomal RNA Transcription in the Mouse Zygote

et al. 2014

View full text Add to dashboard Cite

SUMMARY Extensive chromatin reprogramming occurs at fertilization and is thought to be under the control of maternal factors, but the underlying mechanisms remain poorly understood. We report that maternal Hira, a chaperone for the histone variant H3.3, is required for mouse development past the zygote stage. Male pronucleus formation is inhibited upon deletion of Hira due to a lack of nucleosome assembly in the sperm genome. Hira mutant oocytes are incapable of developing parthenogenetically, indicative of a role for Hira in the female genome. Both parental genomes show highly reduced levels of DNA replication and transcription in the mutants. It has long been thought that transcription is not required for zygote development. Surprisingly, we found that Hira/H3.3-dependent transcription of ribosomal RNA is required for first cleavage. Our results demonstrate that Hira-mediated H3.3 incorporation is essential for parental genome reprogramming, and reveal an unexpected role for rRNA transcription in the mouse zygote.

show abstract

“…It is always assumed that the mechanism of action relevant to cancer is related to the well-known role of miRNA in cytoplasmic RNAi. However, cancer cells are often associated with aberrant nucleoli (46), and a Pol I inhibitor is currently in stage I trials as an anti-cancer compound (47,48). Thus, the connection between miRNA and cancer may be related to this poorly understood role in the nucleolus.…”

Section: Discussionmentioning

confidence: 99%

Human Argonaute 2 Is Tethered to Ribosomal RNA through MicroRNA Interactions

Atwood

Woolnough

Lefèvre

et al. 2016

Journal of Biological Chemistry

View full text Add to dashboard Cite

The primary role of the RNAi machinery is to promote mRNA degradation within the cytoplasm in a microRNA-dependent manner. However, both Dicer and the Argonaute protein family have expanded roles in gene regulation within the nucleus. To further our understanding of this role, we have identified chromatin binding sites for AGO2 throughout the 45S region of the human rRNA gene. The location of these sites was mirrored by the positions of AGO2 cross-linking sites identified via PAR-CLIP-seq. AGO2 binding to the rRNA within the nucleus was confirmed by RNA immunoprecipitation and quantitative-PCR. To explore a possible mechanism by which AGO2 could be recruited to the rRNA, we identified 1174 regions within the 45S rRNA transcript that have the ability to form a perfect duplex with position 2-6 (seed sequence) of each microRNA expressed in HEK293T cells. Of these potential AGO2 binding sites, 479 occurred within experimentally verified AGO2-rRNA crosslinking sites. The ability of AGO2 to cross-link to rRNA was almost completely lost in a DICER knock-out cell line. The transfection of miR-92a-2-3p into the noDICE cell line facilitated AGO2 cross-linking at a region of the rRNA that has a perfect seed match at positions 3-8, including a single G-U base pair. Knockdown of AGO2 within HEK293T cells causes a slight, but statistically significant increase in the overall rRNA synthesis rate but did not impact the ratio of processing intermediates or the recruitment of the Pol I transcription factor UBTF.The RNAi machinery has many functions in the eukaryotic cell, and aspects of the RNAi molecular mechanism are highly conserved between yeast and humans (1). Essentially, a small RNA is bound by a member of the Argonaute family of proteins and contributes sequence specificity to a larger protein complex. In the cytoplasm, the RNAi machinery uses Watson-Crick base pairing to target the RNA-induced silencing complex to a specific mRNA and facilitate its degradation. A related process is well established in the nucleus of Schizosaccharomyces pombe, where instead of targeting cytoplasmic mRNAs for destruction, a small RNA targets the RNA-induced transcriptional silencing complex to the pericentromeric regions of each chromosome and facilitates the generation of heterochromatin (2, 3).Work in a chicken-human hybrid cell line supports the possibility that the RNAi machinery is responsible for centromeric chromatin structure in vertebrates as well (4). Indeed, when Dicer is conditionally inactivated, transcription of ␣-satellite DNA from human chromosome 21 increases. Furthermore, the loss of Dicer results in a loss of siRNAs originating from these repeat regions, a delocalization of HP1, and disruption of mitosis (4). The RNAi machinery is also implicated in the creation and/or maintenance of heterochromatin at various sites throughout the genome, in addition to the centromeric regions. Transfection of a siRNA homologous to the EF1a promoter in human cells silences the endogenous gene (5). In a related study, human Argonaute 1 (A...

show abstract

Discovery of CX-5461, the First Direct and Selective Inhibitor of RNA Polymerase I, for Cancer Therapeutics

Cited by 126 publications

References 21 publications

Inhibition of Pol I transcription treats murine and human AML by targeting the leukemia-initiating cell population

Inhibition of Pol I transcription treats murine and human AML by targeting the leukemia-initiating cell population

Hira-Mediated H3.3 Incorporation Is Required for DNA Replication and Ribosomal RNA Transcription in the Mouse Zygote

Human Argonaute 2 Is Tethered to Ribosomal RNA through MicroRNA Interactions

Contact Info

Product

Resources

About