Targeted suppression of EVI1 oncogene expression by sequence-specific pyrrole-imidazole polyamide

Orthogonal proteogenomic analysis identifies the druggable PA2G4-MYC axis in 3q26 AML

The overexpression of the ecotropic viral integration site-1 gene (EVI1/MECOM) marks the most lethal acute myeloid leukemia (AML) subgroup carrying chromosome 3q26 abnormalities. By taking advantage of the intersectionality of high-throughput cell-based and gene expression screens selective and pan-histone deacetylase inhibitors (HDACis) emerge as potent repressors of EVI1. To understand the mechanism driving on-target anti-leukemia activity of this compound class, here we dissect the expression dynamics of the bone marrow leukemia cells of patients treated with HDACi and reconstitute the EVI1 chromatin-associated co-transcriptional complex merging on the role of proliferation-associated 2G4 (PA2G4) protein. PA2G4 overexpression rescues AML cells from the inhibitory effects of HDACis, while genetic and small molecule inhibition of PA2G4 abrogates EVI1 in 3q26 AML cells, including in patient-derived leukemia xenografts. This study positions PA2G4 at the crosstalk of the EVI1 leukemogenic signal for developing new therapeutics and urges the use of HDACis-based combination therapies in patients with 3q26 AML.

Potentiometric Determination of Acid Dissociation Constants (pK a) for an Anticancer Pyrrole-Imidazole Polyamide

To optimize the pharmacological properties of an anticancer pyrrole-imidazole (Py-Im) polyamide (PIP-1), we characterized the acid dissociation constants of PIP-1, three other structurally related hairpin-shaped polyamides, and a cyclic polyamide bearing the same core sequence as PIP-1 via potentiometric titration. The acidities of the carboxylic acid at the C-terminus and the tertiary amine in the triamine linker remained very similar among the polyamides tested, whereas the pK a of the N-methylimidazole (Im) moieties varied with the peptide sequence and molecular architecture. A nearly 0.2 pH unit pK a shift of terminal Im toward the neutral state compared to internal Im was observed. Furthermore, according to the dissociation constants, a speciation diagram of PIP-1 as a function of pH is presented, which allows an assessment of the net charge and distribution of protonated species in the range of physiological pH.

Targeting the mutant PIK3CA gene by DNA-alkylating pyrrole-imidazole polyamide in cervical cancer

PIK3CA is the most frequently mutated oncogene in cervical cancer, and somatic mutations in the PIK3CA gene result in increased activity of PI3K. In cervical cancer, the E545K mutation in PIK3CA leads to elevated cell proliferation and reduced apoptosis. In the present study, we designed and synthesized a novel pyrrole-imidazole polyamide-seco-CBI conjugate, P3AE5K, to target the PIK3CA gene bearing the E545K mutation, rendered possible by nuclear access and the unique sequence specificity of pyrrole-imidazole polyamides. P3AE5K interacted with double-stranded DNA of the coding region containing the E545K mutation. When compared with conventional PI3K inhibitors, P3AE5K demonstrated strong cytotoxicity in E545K-positive cervical cancer cells at lower concentrations. PIK3CA mutant cells exposed to P3AE5K exhibited reduced expression levels of PIK3CA mRNA and protein, and subsequent apoptotic cell death. Moreover, P3AE5K significantly decreased the tumor growth in mouse xenograft models derived from PIK3CA mutant cells. Overall, the present data strongly suggest that the alkylating pyrrole-imidazole polyamide P3AE5K should be a promising new drug candidate targeting a constitutively activating mutation of PIK3CA in cervical cancer.

Chemical Approaches to the Development of Artificial Transcription Factors Based on Pyrrole-Imidazole Polyamides

To maintain the functions of living organisms, cells have developed complex gene regulatory networks. Transcription factors have a central role in spatiotemporal control of gene expression and this has motivated us to develop artificial transcription factors that mimic their function. We found that three functions could be mimicked by applying our chemical approaches: i) efficient delivery into organelles that contain target DNA, ii) specific DNA binding to the target genomic region, and iii) regulation of gene expression by interaction with other transcription coregulators. We chose pyrrole-imidazole polyamides (PIPs), sequence-selective DNA binding molecules, as DNA binding domains, and have achieved each of the required functions by introducing other functional moieties. The developed artificial transcription factors have potential as chemical tools that can be used to artificially modulate gene expression to enable cell fate control and to correct abnormal gene regulation for therapeutic purposes.

Enhanced nuclear accumulation of pyrrole-imidazole polyamides by incorporation of the tri-arginine vector

The tri-arginine moiety enhanced nuclear accumulation of a 12-ring pyrrole-imidazole polyamide (PIP) without compromising sequence-selectivity and achieved efficient repression of SOX2-downstream genes and HER2 transcription in live cells. This simple vector expands the application of long PIPs in live cells by overcoming the compound delivery problems associated with them.

Targeted suppression of metastasis regulatory transcription factor SOX2 in various cancer cell lines using a sequence-specific designer pyrrole-imidazole polyamide

Metastasis, a deadly feature of cancer, compromises the prognosis and accounts for mortality in the majority of cancer patients. SOX2, a well-known pluripotency transcription factor, plays a central role in cell fate determination and has an overlapping role as a regulatory factor in tumorigenesis and metastasis. The demand is increasing for clinically useful strategies for artificial control of SOX2 expression and its complex transcription machinery in cancer cells. N-Methylpyrrole (Py) and N-methylimidazole (Im) polyamides are small programmable designer ligands that can be pre-programmed to selectively recognize DNA sequence and control endogenous gene expression. Herein, we evaluated the anticancer activity of a designer ligand (SOX2i). SOX2i remarkably altered the expression of SOX2 at the mRNA and protein level in human cancer cell lines such as SW620 (colorectal adenocarcinoma), MKN45 (gastric adenocarcinoma), MCF7 (breast carcinoma), U2OS (osteosarcoma) and other cancer cell lines of different origin and type. Genome-wide transcriptome analysis and cell-based assays showed SOX2 to be a downregulated upstream regulator that alters cell proliferation, cell cycle progression, metabolism and apoptotic pathway. Studies in the mouse model confirmed the anti-metastatic property of SOX2i. SOX2i inhibited the expression of genes associated with EMT and stemness. Moreover, Wnt-canonical signaling was found to be downregulated in the SOX2i-treated group. Our proof-of-concept study supports the potential of DNA-based programmable small molecules for controlling the key regulatory factors associated with tumorigenesis and metastasis.

Therapeutic gene regulation using pyrrole-imidazole polyamides

Recent innovations in cutting-edge sequencing platforms have allowed the rapid identification of genes associated with communicable, noncommunicable and rare diseases. Exploitation of this collected biological information has facilitated the development of nonviral gene therapy strategies and the design of several proteins capable of editing specific DNA sequences for disease control. Small molecule-based targeted therapeutic approaches have gained increasing attention because of their suggested clinical benefits, ease of control and lower costs. Pyrrole-imidazole polyamides (PIPs) are a major class of DNA minor groove-binding small molecules that can be predesigned to recognize specific DNA sequences. This programmability of PIPs allows the on-demand design of artificial genetic switches and fluorescent probes. In this review, we detail the progress in the development of PIP-based designer ligands and their prospects as advanced DNA-based small-molecule drugs for therapeutic gene modulation.

Structural and Kinetic Profiling of Allosteric Modulation of Duplex DNA Induced by DNA-Binding Polyamide Analogues

A combined structural and quantitative biophysical profile of the DNA binding affinity, kinetics and sequence-selectivity of hairpin polyamide analogues is described. DNA duplexes containing either target polyamide binding sites or mismatch sequences are immobilized on a microelectrode surface. Quantitation of the DNA binding profile of polyamides containing N-terminal 1-alkylimidazole (Im) units exhibit picomolar binding affinities for their target sequences, whereas 5-alkylthiazole (Nt) units are an order of magnitude lower (low nanomolar). Comparative NMR structural analyses of the polyamide series shows that the steric bulk distal to the DNA-binding face of the hairpin iPr-Nt polyamide plays an influential role in the allosteric modulation of the overall DNA duplex structure. This combined kinetic and structural study provides a foundation to develop next-generation hairpin designs where the DNA-binding profile of polyamides is reconciled with their physicochemical properties.

Targeting Transcription Factors for Cancer Treatment

Transcription factors are involved in a large number of human diseases such as cancers for which they account for about 20% of all oncogenes identified so far. For long time, with the exception of ligand-inducible nuclear receptors, transcription factors were considered as “undruggable” targets. Advances knowledge of these transcription factors, in terms of structure, function (expression, degradation, interaction with co-factors and other proteins) and the dynamics of their mode of binding to DNA has changed this postulate and paved the way for new therapies targeted against transcription factors. Here, we discuss various ways to target transcription factors in cancer models: by modulating their expression or degradation, by blocking protein/protein interactions, by targeting the transcription factor itself to prevent its DNA binding either through a binding pocket or at the DNA-interacting site, some of these inhibitors being currently used or evaluated for cancer treatment. Such different targeting of transcription factors by small molecules is facilitated by modern chemistry developing a wide variety of original molecules designed to specifically abort transcription factor and by an increased knowledge of their pathological implication through the use of new technologies in order to make it possible to improve therapeutic control of transcription factor oncogenic functions.

Targeting Polo-like Kinase 1 by a Novel Pyrrole-Imidazole Polyamide-Hoechst Conjugate Suppresses Tumor Growth In Vivo

The serine/threonine kinase Polo-like kinase 1 (Plk1) plays a pivotal role in cell proliferation and has been validated as a promising anticancer drug target. However, very limited success has been achieved in clinical applications using existing Plk1 inhibitors, due to lack of sufficient specificity toward Plk1. To develop a novel Plk1 inhibitor with high selectivity and efficacy, we designed and synthesized a pyrrole-imidazole polyamide-Hoechst conjugate, PIP3, targeted to specific DNA sequence in the PLK1 promoter. PIP3 could specifically inhibit the cell cycle-regulated Plk1 expression and consequently retard tumor cell growth. Cancer cells treated with PIP3 exhibited severe mitotic defects and increased apoptosis, whereas normal cells were not affected by PIP3 treatment. Furthermore, subcutaneous injection of PIP3 into mice bearing human cancer xenografts induced significant tumor growth suppression with low host toxicity. Therefore, PIP3 exhibits the potential as an effective agent for targeted cancer therapy. Mol Cancer Ther; 17(5); 988-1002. ©2018 AACR.

Synthetic DNA-Binding Inhibitor of HES1 Alters the Notch Signaling Pathway and Induces Neuronal Differentiation

Synthetic DNA-binding inhibitors capable of gaining precise control over neurogenesis factors could obviate the current clinical barriers associated with the use of small molecules in regenerative medicine. Here, we report the design and bioefficacy of the synthetic ligand PIP-RBPJ-1, which caused promoter-specific suppression of neurogenesis-associated HES1 and its downstream genes. Furthermore, PIP-RBPJ-1 alone altered the neural-system-associated Notch-signaling factors and remarkably induced neurogenesis with an efficiency that was comparable to that of a conventional approach.

Mitochondria: promising organelle targets for cancer diagnosis and treatment

Mitochondrial-mediated tumor monitoring provides a new perspective on mitochondria-based therapy.

Novel insights into chromosomal conformations in cancer

Exploring gene function is critical for understanding the complexity of life. DNA sequences and the three-dimensional organization of chromatin (chromosomal interactions) are considered enigmatic factors underlying gene function, and interactions between two distant fragments can regulate transactivation activity via mediator proteins. Thus, a series of chromosome conformation capture techniques have been developed, including chromosome conformation capture (3C), circular chromosome conformation capture (4C), chromosome conformation capture carbon copy (5C), and high-resolution chromosome conformation capture (Hi-C). The application of these techniques has expanded to various fields, but cancer remains one of the major topics. Interactions mediated by proteins or long noncoding RNAs (lncRNAs) are typically found using 4C-sequencing and chromatin interaction analysis by paired-end tag sequencing (ChIA-PET). Currently, Hi-C is used to identify chromatin loops between cancer risk-associated single-nucleotide polymorphisms (SNPs) found by genome-wide association studies (GWAS) and their target genes. Chromosomal conformations are responsible for altered gene regulation through several typical mechanisms and contribute to the biological behavior and malignancy of different tumors, particularly prostate cancer, breast cancer and hematologic neoplasms. Moreover, different subtypes may exhibit different 3D-chromosomal conformations. Thus, C-tech can be used to help diagnose cancer subtypes and alleviate cancer progression by destroying specific chromosomal conformations. Here, we review the fundamentals and improvements in chromosome conformation capture techniques and their clinical applications in cancer to provide insight for future research.

A synthetic DNA-binding inhibitor of SOX2 guides human induced pluripotent stem cells to differentiate into mesoderm

Targeted differentiation of human induced pluripotent stem cells (hiPSCs) using only chemicals would have value-added clinical potential in the regeneration of complex cell types including cardiomyocytes. Despite the availability of several chemical inhibitors targeting proteins involved in signaling pathways, no bioactive synthetic DNA-binding inhibitors, targeting key cell fate-controlling genes such as SOX2, are yet available. Here, we demonstrate a novel DNA-based chemical approach to guide the differentiation of hiPSCs using pyrrole-imidazole polyamides (PIPs), which are sequence-selective DNA-binding synthetic molecules. Harnessing knowledge about key transcriptional changes during the induction of cardiomyocyte, we developed a DNA-binding inhibitor termed PIP-S2, targeting the 5'-CTTTGTT-3' and demonstrated that inhibition of SOX2-DNA interaction by PIP-S2 triggers the mesoderm induction in hiPSCs. Genome-wide gene expression analyses revealed that PIP-S2 induced mesoderm by targeted alterations in SOX2-associated gene regulatory networks. Also, employment of PIP-S2 along with a Wnt/β-catenin inhibitor successfully generated spontaneously contracting cardiomyocytes, validating our concept that DNA-binding inhibitors could drive the directed differentiation of hiPSCs. Because PIPs can be fine-tuned to target specific DNA sequences, our DNA-based approach could be expanded to target and regulate key transcription factors specifically associated with desired cell types.

A Multi-target Small Molecule for Targeted Transcriptional Activation of Therapeutically Significant Nervous System Genes

An integrated multi‐target small molecule capable of altering dynamic epigenetic and transcription programs associated with the brain and nervous system has versatile applications in the regulation of therapeutic and cell‐fate genes. Recently, we have been constructing targeted epigenetic ON switches by integrating sequence‐specific DNA binding pyrrole‐imidazole polyamides with a potent histone deacetylase inhibitor SAHA. Here, we identified a DNA‐based epigenetic ON switch termed SAHA‐L as the first‐ever multi‐target small molecule capable of inducing transcription programs associated with the human neural system and brain synapses networks in BJ human foreskin fibroblasts and 201B7‐iPS cells. Ingenuity pathway analysis showed that SAHA‐L activates the signaling of synaptic receptors like glutamate and γ‐aminobutyric acid, which are key components of autism spectrum disorders. The long‐term incubation of SAHA‐L in 201B7‐iPS cells induced morphology changes and promoted a neural progenitor state. Our finding suggests that the tunable SAHA‐L could be advanced as a cell‐type‐independent multi‐target small molecule for therapeutic and/or cell‐fate gene modulation.

Sequence-specific DNA binding by long hairpin pyrrole-imidazole polyamides containing an 8-amino-3,6-dioxaoctanoic acid unit

With the aim of improving aqueous solubility, we designed and synthesized five N-methylpyrrole (Py)-N-methylimidazole (Im) polyamides capable of recognizing 9-bp sequences. Their DNA-binding affinities and sequence specificities were evaluated by SPR and Bind-n-Seq analyses. The design of polyamide 1 was based on a conventional model, with three consecutive Py or Im rings separated by a β-alanine to match the curvature and twist of long DNA helices. Polyamides 2 and 3 contained an 8-amino-3,6-dioxaoctanoic acid (AO) unit, which has previously only been used as a linker within linear Py-Im polyamides or between Py-Im hairpin motifs for tandem hairpin. It is demonstrated herein that AO also functions as a linker element that can extend to 2-bp in hairpin motifs. Notably, although the AO-containing unit can fail to bind the expected sequence, polyamide 4, which has two AO units facing each other in a hairpin form, successfully showed the expected motif and a KD value of 16nM was recorded. Polyamide 5, containing a β-alanine-β-alanine unit instead of the AO of polyamide 2, was synthesized for comparison. The aqueous solubilities and nuclear localization of three of the polyamides were also examined. The results suggest the possibility of applying the AO unit in the core of Py-Im polyamide compounds.

Deciphering the genomic targets of alkylating polyamide conjugates using high-throughput sequencing

Chemically engineered small molecules targeting specific genomic sequences play an important role in drug development research. Pyrrole-imidazole polyamides (PIPs) are a group of molecules that can bind to the DNA minor-groove and can be engineered to target specific sequences. Their biological effects rely primarily on their selective DNA binding. However, the binding mechanism of PIPs at the chromatinized genome level is poorly understood. Herein, we report a method using high-throughput sequencing to identify the DNA-alkylating sites of PIP-indole-seco-CBI conjugates. High-throughput sequencing analysis of conjugate 2: showed highly similar DNA-alkylating sites on synthetic oligos (histone-free DNA) and on human genomes (chromatinized DNA context). To our knowledge, this is the first report identifying alkylation sites across genomic DNA by alkylating PIP conjugates using high-throughput sequencing.

Clinical and prognostic significance of 3q26.2 and other chromosome 3 abnormalities in CML in the era of tyrosine kinase inhibitors

Chromosome 3q26.2 abnormalities in acute myeloid leukemia, including inv(3)/t(3;3) and t(3;21), have been studied and are associated with a poor prognosis. Their prevalence, response to tyrosine kinase inhibitor (TKI) treatment, and prognostic significance in chronic myelogenous leukemia (CML) are largely unknown. In this study, we explored these aspects using a cohort of 2013 patients with CML diagnosed in the era of TKI therapy. Chromosome 3 abnormalities were observed in 116 (5.8%) of 2013 cases. These cases were divided into 5 distinct groups: A, inv(3)(q21q26.2)/t(3;3)(q21;q26.2), 26%; B, t(3;21)(q26.2;q22), 17%; C, other 3q26.2 rearrangements, 7%; D, rearrangements involving chromosome 3 other than 3q26.2 locus, 32%; and E, gain or loss of partial or whole chromosome 3, 18%. In all, 3q26.2 rearrangements were the most common chromosome 3 abnormalities (50%, groups A-C). 3q26.2 rearrangements emerged at different leukemic phases. For cases with 3q26.2 rearrangements that initially emerged in chronic or accelerated phase, they had a high rate of transformation to blast phase. Patients with 3q26.2 abnormalities showed a marginal response to TKI treatment, and no patients achieved a long-term sustainable response at a cytogenetic or molecular level. Compared with other chromosomal abnormalities in CML, patients with 3q26.2 rearrangements had poorer overall survival. The presence or absence of other concurrent chromosomal abnormalities did not affect survival in these patients, reflecting the predominant role of 3q26.2 rearrangements in determining prognosis. Interestingly, although heterogeneous, chromosome 3 abnormalities involving non-3q26.2 loci (groups D, E) also conferred a worse prognosis compared with changes involving other chromosomes in this cohort.