TCPs: privileged scaffolds for identifying potent LSD1 inhibitors for cancer therapy

Lysine-specific demethylase 1 activation by vitamin B2 attenuates efficacy of apatinib for proliferation and migration of gastric cancer cell MGC-803

B vitamins play an essential role in the biosynthesis of nucleotides, replication of DNA, supply of methyl-groups, growth and repair of cells, aberrancies of which have all been implicated in carcinogenesis. Although the potential role of vitamin B in relation to the risk of cancer, including breast, and colorectal cancer, has been investigated in several observational studies, the mechanism of action is still unclear. In this study, vitamin B2 exhibited efficient activation of LSD1 by occupying the active sites where FAD stands. Interestingly, vitamin B2 significantly downregulated expression of CD86, a sensitive surrogate biomarker of LSD1 inhibition, and showed marked activation of gastric cancer cell migration and invasion. Meanwhile, vitamin B2 induced activation of LSD1 may attenuate the proliferation inhibition, and anti-migration effects of apatinib in gastric cancer cells. These findings suggested that vitamin B supplementation may interfere with the efficacy of apatinib in patients with gastric cancer.

Novel spirocyclic tranylcypromine derivatives as lysine-specific demethylase 1 (LSD1) inhibitors

Herein we describe the design, synthesis, and biological evaluation of a novel series of tranylcypromine-based LSD1 inhibitors via conformational restriction using spiro ring systems.

Targeting histone methyltransferase and demethylase in acute myeloid leukemia therapy

Acute myeloid leukemia (AML) is a clonal disorder of myeloid progenitors characterized by the acquisition of chromosomal abnormalities, somatic mutations, and epigenetic changes that determine a consistent degree of biological and clinical heterogeneity. Advances in genomic technologies have increasingly shown the complexity and heterogeneity of genetic and epigenetic alterations in AML. Among the genetic alterations occurring in AML, frequent are the genetic alterations at the level of various genes involved in the epigenetic control of the DNA methylome and histone methylome. In fact, genes involved in DNA demethylation (such as DNMT3A, TET2, IDH1, and IDH2) or histone methylation and demethylation (EZH2, MLL, DOT1L) are frequently mutated in primary and secondary AML. Furthermore, some histone demethylases, such as LSD1, are frequently overexpressed in AML. These observations have strongly supported a major role of dysregulated epigenetic regulatory processes in leukemia onset and development. This conclusion was further supported by the observation that mutations in genes encoding epigenetic modifiers, such as DMT3A, ASXL1, TET2, IDH1, and IDH2, are usually acquired early and are present in the founding leukemic clone. These observations have contributed to development of the idea that targeting epigenetic abnormalities could represent a potentially promising strategy for the development of innovative treatments of AML. In this review, we analyze those proteins and their inhibitors that have already reached the first stages of clinical trials in AML, namely the histone methyltransferase DOT1L, the demethylase LSD1, and the MLL-interacting protein menin.

Identification of downstream metastasis-associated target genes regulated by LSD1 in colon cancer cells

Purpose

This study aims to identify downstream target genes regulated by lysine-specific demethylase 1 (LSD1) in colon cancer cells and investigate the molecular mechanisms of LSD1 influencing invasion and metastasis of colon cancer.

Method

We obtained the expression changes of downstream target genes regulated by small-interfering RNA-LSD1 and LSD1-overexpression via gene expression profiling in two human colon cancer cell lines. An Affymetrix Human Transcriptome Array 2.0 was used to identify differentially expressed genes (DEGs). We screened out LSD1-target gene associated with proliferation, metastasis, and invasion from DEGs via Gene Ontology and Pathway Studio. Subsequently, four key genes (CABYR, FOXF2, TLE4, and CDH1) were computationally predicted as metastasis-related LSD1-target genes. ChIp-PCR was applied after RT-PCR and Western blot validations to detect the occupancy of LSD1-target gene promoter-bound LSD1.

Result

A total of 3633 DEGs were significantly upregulated, and 4642 DEGs were downregulated in LSD1-silenced SW620 cells. A total of 4047 DEGs and 4240 DEGs were upregulated and downregulated in LSD1-overexpressed HT-29 cells, respectively. RT-PCR and Western blot validated the microarray analysis results. ChIP assay results demonstrated that LSD1 might be negative regulators for target genes CABYR and CDH1. The expression level of LSD1 is negatively correlated with mono- and dimethylation of histone H3 lysine4(H3K4) at LSD1- target gene promoter region. No significant mono-methylation and dimethylation of H3 lysine9 methylation was detected at the promoter region of CABYR and CDH1.

Conclusion

LSD1- depletion contributed to the upregulation of CABYR and CDH1 through enhancing the dimethylation of H3K4 at the LSD1-target genes promoter. LSD1- overexpression mediated the downregulation of CABYR and CDH1expression through decreasing the mono- and dimethylation of H3K4 at LSD1-target gene promoter in colon cancer cells. CABYR and CDH1 might be potential LSD1-target genes in colon carcinogenesis.

Discovery of tranylcypromine analogs with an acylhydrazone substituent as LSD1 inactivators: Design, synthesis and their biological evaluation

Lysine specific demethylase 1 (LSD1), the first identified histone demethylase, plays an important role in epigenetic regulation of gene activation and repression, has been reported to be up-regulated and involved in numbers of solid malignant tumors. In this study, we identified a series of phenylalanyl hydrazones based LSD1 inhibitors, and the most potent one, compound 4q, can inactivate LSD1 with IC₅₀ = 91.83 nM. In cellular level, compound 4q can induce the accumulation of CD86 as well as H3K4me2, and inhibit gastric cancer cell proliferation by inactivating LSD1. Our findings indicated that compound 4q may serve as a potential leading compound to target LSD1 overexpressed gastric cancer.

Tying up tranylcypromine: Novel selective histone lysine specific demethylase 1 (LSD1) inhibitors

Aberrant expression of lysine specific histone demethylase 1 (LSD1) has been increasingly associated with numerous cancer cells and several proof-of-concept studies are strongly suggestive of its potential as a druggable target. Tranylcypromine (TCP) is an antidepressant originally known to target the monoamine oxidases A and B (MAO-A and MAO-B), which are structurally related to LSD1. A number of TCP derivatives have been identified as potent LSD1 inhibitors, with a handful of them currently being tested in clinical trials. However, thus far the majority of structure-activity relationship studies reported on these TCP derivatives have been mostly limited to the racemates. In this study, we present the SAR data for a novel series of conformationally-restricted TCP-based LSD1 inhibitors, both in their racemic and enantiomerically pure forms. Compounds 18b and 19b were identified as the most potent LSD1 inhibitors within this series, possessing excellent selectivity (>10,000-fold) against MAO-A and MAO-B. These compounds activated CD86 expression on the human MV4-11 AML cells following 10 days of exposure, accompanied with the apparent cytotoxicity. Taken together, these findings are consistent with the pharmacological inhibition of LSD1 and further provide structural insights on the binding modes of these TCP derivatives and their enantiomers at the LSD1.

Advances toward LSD1 inhibitors for cancer therapy

LSD1 has become an important biologically validated epigenetic target for cancer therapy since its identification in 2004. LSD1 mediates many cellular signaling pathways and is involved in the initiation and development of cancers. Aberrant overexpression of LSD1 has been observed in different types of cancers, and inactivation by small molecules suppresses cancer cell differentiation, proliferation, invasion and migration. To date, a large number of LSD1 inhibitors have been reported, RG6016, GSK-2879552, INCB059872, IMG-7289 and CC-90011 are currently undergoing clinical assessment for the treatment of acute myeloid leukemia, small-cell lung cancer, etc. In this review, we briefly highlight recent advances of LSD1 inhibitors mainly covering the literatures from 2015 to 2017 and tentatively propose our perspectives on the design of new LSD1 inhibitors for cancer therapy.

Design, synthesis and biological activity of 3-oxoamino-benzenesulfonamides as selective and reversible LSD1 inhibitors

Lysine specific demethylase 1 (LSD1) is a flavin-dependent amine oxidase that selectively removes one or two methyl groups from H3 at Lys4 and is recognized as a promising therapeutic target for cancer and other diseases. Here, a series of 3-oxoamino-benzenesulfonamides were synthesized and evaluated for their inhibitory activity against LSD1. Compounds 7b and 7h showed the most potent inhibition with the IC50 values of 9.5 and 6.9μM, respectively. Furthermore, the LSD1 inhibition of 7b and 7h were reversible and selective. Docking study presented the possible binding mode between 7b, 7h and the LSD1 active site. Taken together, 3-oxoamino-benzenesulfonamides may represent a new class of reversible LSD1 inhibitors and 7b and 7h were two hit compounds deserved further structural optimization.

LPE-1, an orally active pyrimidine derivative, inhibits growth and mobility of human esophageal cancers by targeting LSD1

Histone lysine specific demethylase 1 (LSD1) plays an important role in epigenetic modifications, and aberrant expression of LSD1 predicts tumor progression and poor prognosis in human esophageal cancers. In this study, a series of LSD1 inhibitors were synthesized and proved to be highly potent against human esophageal squamous cell carcinoma (ESCC). Our data showed that these LSD1 inhibitors selectively suppressed the viability of esophageal cancer cell line (EC-109) bearing overexpressed LSD1. Among these, compound LPE-1 (LSD1 IC₅₀=0.336±0.003μM) significantly suppressed proliferation, induced apoptosis, arrested cell cycle of EC109 cells at G2/M phase, and caused changes of the associated protein markers correspondingly. We also found that compound LPE-1 potently inhibited the migration and invasion of EC-109 cells. Docking studies showed that the cyano group formed hydrogen bonds with Val811 and Thr810. Additionally, the thiophene moiety formed arene-H interaction with Trp761 residue. In vivo studies showed that compound LPE-1 inhibited tumor growth of xenograft models bearing EC-109 without obvious toxicity. Collectively, our findings indicate that LSD1 may be a potential therapeutic target in ESCC, and compound LPE-1 could serve as a lead compound for further development for anti-ESCC drug discovery.

Discovery of [1,2,3]Triazolo[4,5-d]pyrimidine Derivatives as Novel LSD1 Inhibitors

Lysine specific demethylase 1 (LSD1) plays a pivotal role in regulating the lysine methylation. The aberrant overexpression of LSD1 has been reported to be involved in the progression of certain human malignant tumors. Abrogation of LSD1 with RNAi or small molecule inhibitors may lead to the inhibition of cancer proliferation and migration. Herein, a series of [1,2,3]triazolo[4,5-d]pyrimidine derivatives were synthesized and evaluated for their LSD1 inhibitory effects. The structure-activity relationship studies (SARs) were conducted by exploring three regions of this scaffold, leading to the discovery of compound 27 as potent LSD1 inhibitor (IC₅₀ = 0.564 μM). Compound 27 was identified as a reversible LSD1 inhibitor and showed certain selectivity to LSD1 over monoamine oxidase A/B (MAO-A/B). When MGC-803 cells were treated with compound 27, the activity of LSD1 can be significantly inhibited, and the cell migration ability was also suppressed. Docking studies indicated that the hydrogen interaction between the nitrogen atom in the pyridine ring and Met332 could be responsible for the improved activity of 2-thiopyridine series. The [1,2,3]triazolo[4,5-d]pyrimidine scaffold can be used as the template for designing new LSD1 inhibitors.

Structural insight into inhibitors of flavin adenine dinucleotide-dependent lysine demethylases

Until 2004, many researchers believed that protein methylation in eukaryotic cells was an irreversible reaction. However, the discovery of lysine-specific demethylase 1 in 2004 drastically changed this view and the concept of chromatin regulation. Since then, the enzymes responsible for lysine demethylation and their cellular substrates, biological significance, and selective regulation have become major research topics in epigenetics and chromatin biology. Many cell-permeable inhibitors for lysine demethylases have been developed, including both target-specific and nonspecific inhibitors. Structural understanding of how these inhibitors bind to lysine demethylases is crucial both for validation of the inhibitors as chemical probes and for the rational design of more potent, target-specific inhibitors. This review focuses on published small-molecule inhibitors targeted at the two flavin adenine dinucleotide-dependent lysine demethylases, lysine-specific demethylases 1 and 2, and how the inhibitors interact with the tertiary structures of the enzymes.

Regulation of gene expression in human cancers by TRIM24

Tripartite Motif-containing protein 24 (TRIM24) functions as an E3 ligase targeting p53 for ubiquitination, a histone 'reader' that interacts with a specific signature of histone post-translational modifications and a co-regulator of nuclear receptor-regulated transcription. Although mouse models of Trim24 depletion suggest that TRIM24 may be a liver-specific tumor suppressor, several studies show that human TRIM24 is an oncogene when aberrantly over expressed. This review focuses on the mechanisms of TRIM24 functions in oncogenesis and metabolic reprogramming, which underlie recent interest in therapeutic targeting of aberrant TRIM24 in human cancers.