Histone lysine specific demethylase 1 (LSD1) is responsible for the demethylation of mono-/dimethylated lysine residue on histone proteins. LSD1 plays an extensive and essential role in the pathogenesis and progression of many human diseases such as cancers, and thus is becoming an attractive therapeutic target for cancer treatment. Tranylcypromine (TCP) is an important chemical template for developing irreversible LSD1 inhibitors, representing a major chemotype of clinical candidates. Here we report a novel pool of TCP derivatives with triazolopyrimidine as a privileged heterocylic motif. Starting from ticagrelor, a clinically available antiplatelet agent, as a hit compound, our medicinal efforts have led to the identification of compound 9j with nanomolar inhibitory potency against LSD1 as well as broad-spectrum antiproliferative activities against tumor cells. Enzyme studies show that compound 9j is selective over MAO-A/B enzymes, and also cellular active to elevate the expression of H3K4me2 by inhibiting LSD1 in cells. Furthermore, in a H1650 xenograft mouse model, oral administration of compound 9j at low 10 and 20 mg/kg dosages could enable a significant reduction in tumor size and a remarkable extension of survival. The current work is expected to provide an additional strategy to achieve new TCP-based LSD1 inhibitors.

As an important epigenetic regulator, histone lysine specific demethylase 1 (LSD1) has become an attractive target for the discovery of anticancer agents. In this work, a series of tranylcypromine-based derivatives were designed and synthesized. Among them, compound 12u exhibited the most potent inhibitory potency on LSD1 (IC50 = 25.3 nM), and also displayed good antiproliferative effects on MGC-803, KYSE450 and HCT-116 cells with IC50 values of 14.3, 22.8 and 16.3 μM, respectively. Further studies revealed that compound 12u could directly act on LSD1 and inhibit LSD1 in MGC-803 cells, thereby significantly increasing the expression levels of mono-/bi-methylation of H3K4 and H3K9. In addition, compound 12u could induce apoptosis and differentiation, inhibit migration and cell stemness in MGC-803 cells. All these findings suggested that compound 12u was an active tranylcypromine-based derivative as a LSD1 inhibitor that inhibited gastric cancer.

Mammary epithelial cells are the only cells in the mammary glands that are capable of lactation and they are ideal for studying cellular and molecular biology mechanisms during growth, development and lactation of the mammary glands. The limiting factors in most of the currently available mammary epithelial cells are low cell viability, transgenerational efficiency and lactation function that renders them unsuitable for subsequent studies on mammary gland\'s cellular and lactation mechanisms and utilizing them as bioreactors. Hence, new methods are required to obtain mammary epithelial cells with high transgenerational efficiency and lactation function. In this study, transdifferentiation of goat ear fibroblasts (GEFs) into goat mammary epithelial cells (CiMECs) was induced in only eight days by five small molecule compounds, including 500 μg/mL VPA, 10 μM Tranylcypromine, 10 μM Forskolin, 1 μM TTNPB, 10 μM RepSox. Morphological observation, marker genes comparison, specific antigen expression and comparison of gene expression levels by transcriptome sequencing between the two types of cells that led to the primary deduction that CiMECs have similar biological properties to goat mammary epithelial cells (GMECs) and comparatively more lactation capacity. Therefore, we establish a novel reprogramming route to convert fibroblasts into CiMECs under fully chemically conditions. This study is expected to provide an in vitro platform for understanding cellular mechanisms such as mammary epithelial cells\' fate determination and developmental differentiation, and also to find a new way to obtain a large number of functional mammary epithelial cells in vitro.

BACKGROUND: As a FAD (Flavin Adenine Dinucleotide) - dependent histone demethylase discovered in 2004, LSD1 (lysine specific demethylase 1) was reported to be overexpressed in diverse tumors, regulating target genes transcription associated with cancer development. Hence, LSD1 targeted inhibitors may represent a new insight in anticancer drug discovery. For these reasons, researchers in both the pharmaceutical industry and academia have been actively pursuing LSD1 inhibitors in the quest for new anti-cancer drugs.
OBJECTIVE: This review summaries patents about LSD1 inhibitors in recent 5 years in hope of providing a reference for LSD1 researchers to develop new modulators of LSD1 with higher potency and fewer adverse effects.
METHODS: This review collects LSD1 inhibitors disclosed in patents since 2016. The primary ways of patent searching are Espacenet®, Google Patents, and CNKI.
RESULTS: This review covers dozens of patents related to LSD1 inhibitors in recent five years. The compound structures are mainly divided into TCP (Tranylcypromine) derivatives, imidazole derivatives, pyrimidine derivatives, and other natural products and peptides. Meanwhile, the compounds that have entered the clinical phase are also described.
CONCLUSIONS: Most of the compounds in these patents have been subjected to activity analysis with LSD1 and multi-cell lines, showing good antitumor activity in vitro and in vivo. These patents exhibited the structural diversity of LSD1 inhibitors and the potential of natural products as novel LSD1 inhibitors.

OBJECTIVE: To explore the role of prostacyclin (PGI2) and thromboxane A2 (TXA2) in lung hyper-permeability induced by mechanical ventilation (MV) in rabbits.
OBJECTIVE: Forty-eight healthy Japanese white rabbits were randomly allocated to vehicle treatment group (group V), tranylcypromine (a PGI2 synthase inhibitor) treatment group (group T), dazoxiben (a TXA2 synthase inhibitor) treatment group (group D), vehicle-treated MV group (group VM), tranylcyprominetreated MV group (group TM) and dazoxiben-treated MV group (group DM). The contents of PGI2 and TXA2 in the lung tissues and TNF-α level in BALF and lung tissues were measured by ELISA. The lung wet/dry weight (W/D) ratio, lung permeability index and pulmonary expressions of myosin light chain kinase (MLCK) protein and mRNA were detected to evaluate the pulmonary permeability. The severities of lung injury were assessed by lung histological scores.
OBJECTIVE: The measured parameters did not differ significantly among the rabbits receiving different treatments without MV. In rabbits in group VM, the contents of PGI2 and TXA2 in the lungs, TNF-α in BALF and lung tissues, PGI2/TXA2 ratio, lung W/D ratio, lung permeability index, pulmonary expressions of MLCK protein and mRNA and histological scores of the lungs all increased significantly (P < 0.05) as compared with those in group V, group T and group D. In rabbits undergoing MV, inhibition of PGI2 production by tranylcypromine significantly decreased the PGI2/TXA2 ratio (P < 0.05), further enhanced the production of TNF-α in the BALF and lung tissue (P < 0.05), and worsened lung hyper-permeability and lung injury (P < 0.05), while treatment with dazoxiben significantly reduced TXA2 production in the lung tissue (P < 0.05), increased the PGI2/TXA2 ratio (P < 0.05) and decreased TNF-α production in the BALF and lung tissue (P < 0.05), thus resulting in alleviated lung hyperpermeability and lung injury (P < 0.05).
OBJECTIVE: PGI2 plays a protective role against MV-induced lung hyper-permeability and lung injury by downregulating TNF-α/MLCK signaling pathway, while TXA2 can exacerbate MV-induced lung hyperpermeability in rabbits by up-regulating TNF-α/ MLCK signaling pathway.

Tranylcypromine (TCP)-based structural modifications lead to the discovery of new LSD1 inhibitors, of which compounds 26b and 29b effectively inhibit LSD1 with the IC50 values of 17 and 11 nM, respectively and also show good selectivity over MAO-B. Mechanistic studies showed that compound 29b concentration-dependently induced H3K4me1/2 accumulation in LSD1 overexpressed MGC-803 cells and also inhibited metastasis of MGC-803 cells. Collectively, both compounds could be promising lead compounds for further investigation.

Histone lysine-specific demethylase 1 (LSD1/KDM1A) has become an important and promising anticancer target since it was first identified in 2004 and specially demethylates lysine residues of histone H3K4me1/2 and H3K9me1/2. LSD1 is ubiquitously overexpressed in diverse cancers, and abrogation of LSD1 results in inhibition of proliferation, invasion, and migration in cancer cells. Over the past decade, a number of biologically active small-molecule LSD1 inhibitors have been developed. To date, six trans-2-phenylcyclopropylamine (TCP)-based LSD1 inhibitors (including TCP, ORY-1001, GSK-2879552, INCB059872, IMG-7289, and ORY-2001) that covalently bind to the flavin adenine dinucleotide (FAD) within the LSD1 catalytic cavity have already entered into clinical trials. Here, we provide an overview about the structures, activities, and structure-activity relationship (SAR) of TCP-based LSD1 inhibitors that mainly covers the literature from 2008 to date. The opportunities, challenges, and future research directions in this emerging and promising field are also discussed.

Lysine-specific demethylase 1 (LSD1) is frequently elevated in acute myeloid leukemia (AML) and often leads to tumorigenesis. In recent years, numerous LSD1 inhibitors based on tranylcypromine (TCP) scaffolding have reached clinical trials. Most TCP derivatives were modified at the amino site of cyclopropane motif. Herein, we for the first time introduced a sulfonamide group in TCP benzene ring of series a compounds and performed a systematical study on structure and activity relationships by varying sulfonamide groups. The introduction of sulfonamide significantly increased the targeting capacity of TCP against LSD1. Moreover, we discovered that the Boc attached LSD1 inhibitors (labelled as series b compounds) substantially improved their anti-proliferation capacity towards AML cells. The intracellular thermal shift and LC-MS/MS results implied that Boc enhanced the drug lipophilicity and might be removed under the cancerous acidic environment to release the real pharmacophore, evidenced by the fact that a structurally similar but acidic inert pivaloyl to replace Boc dramatically dropped the cellular anti-proliferation effect. Finally, a benzyl group installed at the amino site to appropriately increase lipophilicity led to trans-4-(2-(benzylamino)-cyclopropyl)-N,N-diethylbenzenesulfonamide a10 that showed better anti-proliferation activity in AML cells and enzymatic inhibition against LSD1. Taken together, our work offers a novel TCP-based structure and provides a prodrug strategy for the discovery of potent LSD1 inhibitors by having appropriate lipophilicity.

The histone demethylase LSD1 is a key mediator driving tumorigenesis, which holds potential as a promising therapeutic target. However, treatment with LSD1 inhibitors alone failed to result in complete cancer regression.
The synergistic effects of TCP (a LSD1 inhibitor) and GSK-J1 (a JMJD3 inhibitor) against HNSCC were determined in vitro and in preclinical animal models. Genes modulated by chemical agents or siRNAs in HNSCC cells were identified by RNA-seq and further functionally interrogated by bioinformatics approach. Integrative siRNA-mediated gene knockdown, rescue experiment and ChIP-qPCR assays were utilised to characterise the mediators underlying the therapeutic effects conferred by TCP and GSK-J1.
Treatment with TCP and GSK-J1 impaired cell proliferation, induced apoptosis and senescence in vitro, which were largely recapitulated by simultaneous LSD1 and JMJD3 knockdown. Combinational treatment inhibited tumour growth and progression in vivo. Differentially expressed genes modulated by TCP and GSK-J1 were significantly enriched in cell proliferation, apoptosis and cancer-related pathways. SPP1 was identified as the mediator of synergy underlying the pro-apoptosis effects conferred by TCP and GSK-J1. Co-upregulation of LSD1 and JMJD3 associated with worse prognosis in patients with HNSCC.
Our findings revealed a novel therapeutic strategy of simultaneous LSD1 and JMJD3 inhibition against HNSCC.

Identification of anti-osteoclastogenic agents is important for the treatment of bone loss diseases that feature excessive osteoclast (OC) activity and bone resorption. Tranylcypromine (TCP), an irreversible inhibitor of monoamine oxidase (MAO), has been used as an antidepressant and anxiolytic agent in the clinical treatment of mood and anxiety disorders. TCP has been discovered to exert anabolic effect on osteoblasts, and MAO-A has also been verified as an important mediator in prostate cancer cells to accelerate osteoclastogenesis. In current study, we were focused on TCP and MAO-A effects on osteoclastogenesis. As illustrated by tartrate-resistant acid phosphatase staining, TCP was capable of inhibiting osteoclastogenesis induced by receptor activators of the NF-κB ligand (RANKL) in bone marrow-derived macrophage cells without any cytotoxicity. It was also shown to effectively suppress bone resorption of OCs. The subsequent study revealed that TCP inhibited osteoclastogenesis-related genes in a time-dependent manner through protein kinase B (AKT)-mediated mechanism followed by the nuclear factor of activated T cells, cytoplasmic 1 (NFATc1)-c-fos pathway. And TCP could overcome the osteoclastogenic effects of AKT activator SC79. In addition, our results indicated that the expression and catalytic activity of MAO-A were up-regulated by RANKL stimulation and down-regulated by TCP in vitro and in vivo. Furthermore, the effects of MAO-A knockdown on OC differentiation indicated that MAO-A played an important role in osteoclastogenesis in vitro and might contribute to the inhibitory effects of TCP. And AKT, NFATc1, and c-fos were involved in the MAO-A pathway. Notably, our in vivo study reflected that TCPs were capable of restoring the bone loss in LPS-induced calvaria osteolysis and estrogen deficiency-induced osteoporosis models. Thus, our current work provided a potential option for the treatment of bone loss diseases and highlighted the important role of MAO-A in osteoclastogenesis as well.-Liu, Z., Yang, K., Yan, X., Wang, T., Jiang, T., Zhou, Q., Qi, J., Qian, N., Zhou, H., Chen, B., Huang, P., Guo, L., Zhang, X., Xu, X., Jiang, M., Deng, L. The effects of tranylcypromine on osteoclastogenesis in vitro and in vivo.