The MAO inhibitors phenelzine and clorgyline revert enzalutamide resistance in castration resistant prostate cancer

The highs and lows of monoamine oxidase as molecular target in cancer: an updated review

The global burden of cancer as a major cause of death and invalidity has been constantly increasing in the past decades. Monoamine oxidases (MAO) with two isoforms, MAO-A and MAO-B, are mammalian mitochondrial enzymes responsible for the oxidative deamination of neurotransmitters and amines in the central nervous system and peripheral tissues with the constant generation of hydrogen peroxide as the main deleterious ancillary product. However, given the complexity of cancer biology, MAO involvement in tumorigenesis is multifaceted with different tumors displaying either an increased or decreased MAO profile. MAO inhibitors are currently approved for the treatment of neurodegenerative diseases (mainly, Parkinson's disease) and as secondary/adjunctive therapeutic options for the treatment of major depression. Herein, we review the literature characterizing MAO's involvement and the putative role of MAO inhibitors in several malignancies, and also provide perspectives regarding the potential biomarker role that MAO could play in the future in oncology.

MYO6 contributes to tumor progression and enzalutamide resistance in castration-resistant prostate cancer by activating the focal adhesion signaling pathway

BACKGROUND

Enzalutamide (Enz) resistance is a poor prognostic factor for patients with castration-resistant prostate cancer (CRPC), which often involves aberrant expression of the androgen receptor (AR). Myosin VI (MYO6), one member of the myosin family, plays an important role in regulating cell survival and is highly expressed in prostate cancer (PCa). However, whether MYO6 is involved in Enz resistance in CRPC and its mechanism remain unclear.

METHODS

Multiple open-access databases were utilized to examine the relationship between MYO6 expression and PCa progression, and to screen differentially expressed genes (DEGs) and potential signaling pathways associated with the MYO6-regulated Enz resistance. Both in vitro and in vivo tumorigenesis assays were employed to examine the impact of MYO6 on the growth and Enz resistance of PCa cells. Human PCa tissues and related clinical biochemical data were utilized to identify the role of MYO6 in promoting PCa progression and Enz resistance. The molecular mechanisms underlying the regulation of gene expression, PCa progression, and Enz resistance in CRPC by MYO6 were investigated.

RESULTS

MYO6 expression increases in patients with PCa and is positively correlated with AR expression in PCa cell lines and tissues. Overexpression of AR increases MYO6 expression to promote PCa cell proliferation, migration and invasion, and to inhibit PCa cell apoptosis; whereas knockdown of MYO6 expression reverses these outcomes and enhances Enz function in suppressing the proliferation of the Enz- sensitive and resistant PCa cells both in vitro and in vivo. Mechanistically, AR binds directly to the promoter region (residues - 503 to - 283 base pairs) of MYO6 gene and promotes its transcription. Furthermore, MYO6 activates focal adhesion kinase (FAK) phosphorylation at tyrosine-397 through integrin beta 8 (ITGB8) modulation to promote PCa progression and Enz resistance. Notably, inhibition of FAK activity by Y15, an inhibitor of FAK, can resensitize CRPC cells to Enz treatment in cell lines and mouse xenograft models.

CONCLUSIONS

MYO6 has pro-tumor and Enz-resistant effects in CRPC, suggesting that targeting MYO6 may be beneficial for ENZ-resistant CRPC therapy through the AR/MYO6/FAK signaling pathway.

Targeting monoamine oxidases in cancer: advances and opportunities

Monoamine oxidases (MAOs) are a crucial pair of isoenzymes responsible for degrading monoamine neurotransmitters and dietary amines. In addition to extensive studies of their roles in the context of brain functions and disorders over decades, emerging evidence indicates that MAOs are also often dysregulated and associated with clinical outcomes in diverse cancers, with the ability to differentially regulate cancer growth, invasion, metastasis, progression, and therapy response depending on the cancer type. In this review, we summarize recent advances in understanding the clinical relevance, functional importance, and mechanisms of MAOs in a broad range of cancers, and discuss the application and therapeutic benefit of MAO inhibitors (MAOIs) for cancer treatment, highlighting the roles of MAOs as novel regulators, prognostic biomarkers, and therapeutic targets in cancer.

Serotonin signalling in cancer: Emerging mechanisms and therapeutic opportunities

BACKGROUND

Serotonin (5-hydroxytryptamine) is a multifunctional bioamine serving as a neurotransmitter, peripheral hormone and mitogen in the vertebrate system. It has pleiotropic activities in central nervous system and gastrointestinal function via an orchestrated action of serotonergic elements, particularly serotonin receptor-mediated signalling cascades. The mitogenic properties of serotonin have garnered recognition for years and have been exploited for repurposing serotonergic-targeted drugs in cancer therapy. However, emerging conflicting findings necessitate a more comprehensive elucidation of serotonin's role in cancer pathogenesis.

MAIN BODY AND CONCLUSION

Here, we provide an overview of the biosynthesis, metabolism and action modes of serotonin. We summarise our current knowledge regarding the effects of the peripheral serotonergic system on tumourigenesis, with a specific emphasis on its immunomodulatory activities in human cancers. We also discuss the dual roles of serotonin in tumour pathogenesis and elucidate the potential of serotonergic drugs, some of which display favourable safety profiles and impressive efficacy in clinical trials, as a promising avenue in cancer treatment.

KEY POINTS

Primary synthesis and metabolic routes of peripheral 5-hydroxytryptamine in the gastrointestinal tract. Advanced research has established a strong association between the serotonergic components and carcinogenic mechanisms. The interplay between serotonergic signalling and the immune system within the tumour microenvironment orchestrates antitumour immune responses. Serotonergic-targeted drugs offer valuable clinical options for cancer therapy.

MiR26a reverses enzalutamide resistance in a bone-tumor targeted system with an enhanced effect on bone metastatic CRPC

Resistance to androgen receptor (AR) inhibitors, including enzalutamide (Enz), as well as bone metastasis, are major challenges for castration-resistant prostate cancer (CRPC) treatment. In this study, we identified that miR26a can restore Enz sensitivity and inhibit bone metastatic CRPC. To achieve the highest combination effect of miR26a and Enz, we developed a cancer-targeted nano-system (Bm@PT/Enz-miR26a) using bone marrow mesenchymal stem cell (BMSC) membrane and T140 peptide to co-deliver Enz and miR26a. The in vitro/in vivo results demonstrated that miR26a can reverse Enz resistance and synergistically shrink tumor growth, invasion, and metastasis (especially secondary metastasis) in both subcutaneous and bone metastatic CRPC mouse models. We also found that the EZH2/SFRP1/WNT5A axis may be involved in this role. These findings open new avenues for treating bone metastatic and Enz-resistant CRPC.

MAOB expression correlates with a favourable prognosis in prostate cancer, and its genetic variants are associated with the metastasis of the disease

Monoamine oxidase B (MAOB), a neurotransmitter-degrading enzyme, was reported to reveal conflicting roles in various cancers. However, the functional role of MAOB and impacts of its genetic variants on prostate cancer (PCa) is unknown. Herein, we genotyped four loci of MAOB single-nucleotide polymorphisms (SNPs), including rs1799836 (A/G), rs3027452 (G/A), rs6651806 (A/C) and rs6324 (G/A) in 702 PCa Taiwanese patients. We discovered that PCa patients carrying the MAOB rs6324 A-allele exhibited an increased risk of having a high initial prostate-specific antigen (iPSA) level (>10 ng/mL). Additionally, patients with the rs3027452 A-allele had a higher risk of developing distal metastasis, particularly in the subpopulation with high iPSA levels. In a subpopulation without postoperative biochemical recurrence, patients carrying the rs1799836 G-allele had a higher risk of developing lymph node metastasis and recurrence compared to those carrying the A-allele. Furthermore, genotype screening in PCa cell lines revealed that cells carrying the rs1799836 G-allele expressed lower MAOB levels than those carrying the A-allele. Functionally, overexpression and knockdown of MAOB in PCa cells respectively suppressed and enhanced cell motility and proliferation. In clinical observations, correlations of lower MAOB expression levels with higher Gleason scores, advanced clinical T stages, tumour metastasis, and poorer prognosis in PCa patients were noted. Our findings suggest that MAOB may act as a suppressor of PCa progression, and the rs3027452 and rs1799836 genetic variants of MAOB are linked to PCa metastasis within the Taiwanese population.

A second life for MAO inhibitors? From CNS diseases to anticancer therapy

Monoamine oxidases A and B (MAO A, B) are ubiquitous enzymes responsible for oxidative deamination of amine neurotransmitters and xenobiotics. Despite decades of studies, MAO inhibitors (MAOIs) find today limited therapeutic space as second-line drugs for the treatment of depression and Parkinson's disease. In recent years, a renewed interest in MAOIs has been raised up by several studies investigating the role of MAOs, particularly MAO A, in tumor insurgence and progression, and the efficacy of MAOIs as coadjutants in the therapy of chemoresistant tumors. In this survey, we highlight the implication of MAOs in the biochemical pathways of tumorigenesis and review the state-of-the-art of preclinical and clinical studies of MAOIs as anticancer agents used in monotherapy or in combination with antitumor chemotherapeutics.

Phenelzine protects against acetaminophen induced apoptosis in HepG2 cells

Acetaminophen (APAP) overdosing is the most common cause of drug-induced liver failure. Despite extensive study, N-acetylcysteine is currently the only antidote utilized for treatment. The purpose of this study was to evaluate the effect and mechanisms of phenelzine, an FDA-approved antidepressant, on APAP-induced toxicity in HepG2 cells. The human liver hepatocellular cell line HepG2 was used to investigate APAP-induced cytotoxicity. The protective effects of phenelzine were determined by examining the cell viability, combination index calculation, Caspase 3/7 activation, Cytochrome c release, H2O2 levels, NO levels, GSH activity, PERK protein levels, and pathway enrichment analysis. Elevated H2O2 production and decreased glutathione (GSH) levels were indicators of APAP-induced oxidative stress. The combination index of 2.04 indicated that phenelzine had an antagonistic effect on APAP-induced toxicity. When compared to APAP alone, phenelzine treatment considerably reduced caspase 3/7 activation, cytochrome c release, and H2O2 generation. However, phenelzine had minimal effect on NO and GSH levels and did not alleviate ER stress. Pathway enrichment analysis revealed a potential connection between APAP toxicity and phenelzine metabolism. These findings suggested that phenelzine's protective effect against APAP-induced cytotoxicity could be attributed to the drug's capacity to reduce APAP-mediated apoptotic signaling.

Molecular Imaging of Monoamine Oxidase A Expression in Highly Aggressive Prostate Cancer: Synthesis and Preclinical Evaluation of Positron Emission Tomography Tracers

The role of monoamine oxidase A (MAO-A) in the aggressiveness of prostate cancer (PCa) has been established in recent years. The molecular imaging of MAO-A expression could offer a noninvasive tool for the visualization and quantification of highly aggressive PCa. This study reports the synthesis and preclinical evaluation of 11C- and 18F-labeled MAO-A inhibitors as positron emission tomography (PET) tracers for proof-of-concept studies in animal models of PCa. Good manufacturing practice production and quality control of these radiotracers using an automated platform was achieved. PET imaging was performed in an LNCaP tumor model with high MAO-A expression. The tumor-to-muscle (T/M) uptake ratio of [11C]harmine (4.5 ± 0.5) was significantly higher than that for 2-[18F]fluoroethyl-harmol (2.3 ± 0.7) and [11C]clorgyline (2.0 ± 0.1). A comparable ex vivo biodistribution pattern in all radiotracers was observed. Furthermore, the tumor uptake of [11C]harmine showed a dramatic reduction (T/M = 1) in a PC3 tumor model with limited MAO-A expression, and radioactivity uptake in LNCaP tumors was blocked in the presence of nonradioactive harmine. Our findings suggest that [11C]harmine may serve as an attractive PET probe for the visualization of MAO-A expression in highly aggressive PCa. These radiotracers have the potential for clinical translation and may aid in the development of personalized therapeutic strategies for PCa patients.

Molecular Investigation of the Antitumor Effects of Monoamine Oxidase Inhibitors in Breast Cancer Cells

The catalytic activity of monoamine oxidase A (MAO-A) has been linked to tumorigenesis due to the production of reactive oxygen species (ROS) and the resulting oxidative stress. MAO-A inhibition revealed a beneficial role in prostate and lung cancer treatment. This study is aimed at evaluating the effect of different monoamine oxidase A inhibitors (MAO-AIs) on the proliferation and progression of breast cancer cell lines. The cell viability assay was used to evaluate the antiproliferative and combined effects of MAO-AIs. Cell migration was evaluated using wound healing, invasion, and colony formation assays. The underlying mechanism of cell death was studied using flow cytometry. The real-time polymerase chain reaction was used to determine the relative gene expression. Finally, MAO-A activity in breast cancer cells was evaluated using an MAO-A activity assay. According to the results, the examined MAO-AIs significantly inhibited the proliferation of breast cancer cells in a dose-dependent manner. In breast cancer cells, the combination of anticancer drugs (doxorubicin or raloxifene) with MAO-AIs resulted in a synergistic effect. MAO-AIs significantly reduced wound closure and invasion ability in breast cancer cells. Also, MAO-AIs reduced the colony count and size of breast cancer cells. MAO-AIs resulted in significant proapoptotic activity in breast cancer cells. Finally, the MAO-AIs suppressed MAO-A, Bcl-2, and VEGF gene expressions in breast cancer cells relative to untreated cells. This study provides solid evidence supporting the anticancer effect of MAO-A inhibitors in breast cancer cells.

Intermolecular Hydrazinative Halogenation of Alkenes with Potassium Halides as Nucleophilic Halogen Sources: Modular Entry to Phenelzine Derivatives

An approach for the efficient synthesis of halogenated hydrazines via acid-mediated electrophilic hydrazinative halogenation of alkenes is disclosed. This transformation proceeds with readily available diethyl azodicarboxylate as a hydrazine source and low-cost potassium halides as nucleophilic halogen sources. A series of iodinated, brominated, and chlorinated hydrazines are facilely produced with a wide range of functional groups. The obtained products are good platform molecules. They can be conveniently converted into a variety of valuable phenelzine analogues which are appealing for development of novel drugs treating depression.

Inhibition of phosphoglycerate dehydrogenase induces ferroptosis and overcomes enzalutamide resistance in castration-resistant prostate cancer cells

Phosphoglycerate dehydrogenase (PHGDH), the rate-limiting enzyme in the first step of the serine synthesis pathway (SSP), is overexpressed in multiple types of cancers. The androgen receptor inhibitor enzalutamide (Enza) is the primary therapeutic drug for patients with castration-resistant prostate cancer (CRPC). However, most patients eventually develop resistance to Enza. The association of SSP with Enza resistance remains unclear. In this study, we found that high expression of PHGDH was associated with Enza resistance in CRPC cells. Moreover, increased expression of PHGDH led to ferroptosis resistance by maintaining redox homeostasis in Enza-resistant CRPC cells. Knockdown of PHGDH caused significant GSH reduction, induced lipid peroxides (LipROS) increase and significant cell death, resulting in inhibiting growth of Enza-resistant CRPC cells and sensitizing Enza-resistant CRPC cells to enzalutamide treatment both in vitro and in vivo. We also found that overexpression of PHGDH promoted cell growth and Enza resistance in CRPC cells. Furthermore, pharmacological inhibition of PHGDH by NCT-503 effectively inhibited cell growth, induced ferroptosis, and overcame enzalutamide resistance in Enza-resistant CRPC cells both in vitro and in vivo. Mechanically, NCT-503 triggered ferroptosis by decreasing GSH/GSSG levels and increasing LipROS production as well as suppressing SLC7A11 expression through activation of the p53 signaling pathway. Moreover, stimulating ferroptosis by ferroptosis inducers (FINs) or NCT-503 synergistically sensitized Enza-resistant CRPC cells to enzalutamide. The synergistic effects of NCT-503 and enzalutamide were verified in a xenograft nude mouse model. NCT-503 in combination with enzalutamide effectively restricted the growth of Enza-resistant CRPC xenografts in vivo. Overall, our study highlights the essential roles of increased PHGDH in mediating enzalutamide resistance in CRPC. Therefore, the combination of ferroptosis inducer and targeted inhibition of PHGDH could be a potential therapeutic strategy for overcoming enzalutamide resistance in CRPC.

From Monoamine Oxidase Inhibition to Antiproliferative Activity: New Biological Perspectives for Polyamine Analogs

Monoamine oxidases (MAOs) are well-known pharmacological targets in neurological and neurodegenerative diseases. However, recent studies have revealed a new role for MAOs in certain types of cancer such as glioblastoma and prostate cancer, in which they have been found overexpressed. This finding is opening new frontiers for MAO inhibitors as potential antiproliferative agents. In light of our previous studies demonstrating how a polyamine scaffold can act as MAO inhibitor, our aim was to search for novel analogs with greater inhibitory potency for human MAOs and possibly with antiproliferative activity. A small in-house library of polyamine analogs (2-7) was selected to investigate the effect of constrained linkers between the inner amine functions of a polyamine backbone on the inhibitory potency. Compounds 4 and 5, characterized by a dianiline (4) or dianilide (5) moiety, emerged as the most potent, reversible, and mainly competitive MAO inhibitors (Ki < 1 μM). Additionally, they exhibited a high antiproliferative activity in the LN-229 human glioblastoma cell line (GI50 < 1 μM). The scaffold of compound 5 could represent a potential starting point for future development of anticancer agents endowed with MAO inhibitory activity.

Chemical and Biological Evaluation of Novel 1H-Chromeno[3,2-c]pyridine Derivatives as MAO Inhibitors Endowed with Potential Anticancer Activity

About twenty molecules sharing 1H-chromeno[3,2-c]pyridine as the scaffold and differing in the degree of saturation of the pyridine ring, oxidation at C10, 1-phenylethynyl at C1 and 1H-indol-3-yl fragments at C10, as well as a few small substituents at C6 and C8, were synthesized starting from 1,2,3,4-tetrahydro-2-methylchromeno[3,2-c]pyridin-10-ones (1,2,3,4-THCP-10-ones, 1) or 2,3-dihydro-2-methyl-1H-chromeno[3,2-c]pyridines (2,3-DHPCs, 2). The newly synthesized compounds were tested as inhibitors of the human isoforms of monoamine oxidase (MAO A and B) and cholinesterase (AChE and BChE), and the following main SARs were inferred: (i) The 2,3-DHCP derivatives 2 inhibit MAO A (IC₅₀ about 1 μM) preferentially; (ii) the 1,2,3,4-THCP-10-one 3a, bearing the phenylethynyl fragment at C1, returned as a potent MAO B inhibitor (IC₅₀ 0.51 μM) and moderate inhibitor of both ChEs (IC₅₀s 7-8 μM); (iii) the 1H-indol-3-yl fragment at C10 slightly increases the MAO B inhibition potency, with the analog 6c achieving MAO B IC₅₀ of 3.51 μM. The MAO B inhibitor 3a deserves further pharmacological studies as a remedy in the symptomatic treatment of Parkinson's disease and neuroprotectant for Alzheimer's disease. Besides the established neuroprotective effects of MAO inhibitors, the role of MAOs in tumor insurgence and progression has been recently reported. Herein, antiproliferative assays with breast (MCF-7), colon (HCT116) and cisplatin-resistant ovarian (SK-OV-3) tumor cells revealed that the 10-indolyl-bearing 2,3,4,10-THCP analog 6c exerts anti-tumor activity with IC₅₀s in the range 4.83-11.3 μM.

Network-based drug repurposing for potential stroke therapy

Stroke is the leading cause of death and disability worldwide, with a growing number of incidences in developing countries. However, there are currently few medical therapies for this disease. Emerged as an effective drug discovery strategy, drug repurposing which owns lower cost and shorter time, is able to identify new indications from existing drugs. In this study, we aimed at identifying potential drug candidates for stroke via computationally repurposing approved drugs from Drugbank database. We first developed a drug-target network of approved drugs, employed network-based approach to repurpose these drugs, and altogether identified 185 drug candidates for stroke. To validate the prediction accuracy of our network-based approach, we next systematically searched for previous literature, and found 68 out of 185 drug candidates (36.8 %) exerted therapeutic effects on stroke. We further selected several potential drug candidates with confirmed neuroprotective effects for testing their anti-stroke activity. Six drugs, including cinnarizine, orphenadrine, phenelzine, ketotifen, diclofenac and omeprazole, have exhibited good activity on oxygen-glucose deprivation/reoxygenation (OGD/R) induced BV2 cells. Finally, we showcased the anti-stroke mechanism of actions of cinnarizine and phenelzine via western blot and Olink inflammation panel. Experimental results revealed that they both played anti-stroke effects in the OGD/R induced BV2 cells via inhibiting the expressions of IL-6 and COX-2. In summary, this study provides efficient network-based methodologies for in silico identification of drug candidates toward stroke.

Monoamine oxidase A (MAOA): A promising target for prostate cancer therapy

Monoamine oxidase A (MAOA) is a mitochondrial enzyme that catalyzes the oxidative deamination of monoamine neurotransmitters and dietary amines. Previous studies have shown that MAOA is clinically associated with prostate cancer (PCa) progression and plays a key role in almost each stage of PCa, including castrate-resistant prostate cancer, neuroendocrine prostate cancer, metastasis, drug resistance, stemness, and perineural invasion. Moreover, MAOA expression is upregulated not only in cancer cells but also in stromal cells, intratumoral T cells, and tumor-associated macrophages; thus, targeting MAOA can be a multi-pronged approach to disrupt tumor promoting interactions between PCa cells and tumor microenvironment. Furthermore, targeting MAOA can disrupt the crosstalk between MAOA and the androgen receptor (AR) to restore enzalutamide sensitivity, blocks glucocorticoid receptor (GR)- and AR-dependent PCa cell growth, and is a potential strategy for immune checkpoint inhibition, thereby alleviating immune suppression and enhancing T cell immunity-based cancer immunotherapy. MAOA is a promising target for PCa therapy, which deserves further exploration in preclinical and clinical settings.

Doxorubicin-isoniazid conjugate regulates immune response and tumor microenvironment to enhance cancer therapy

Immune checkpoint inhibitors (ICIs) represent a new class of immunotherapy drugs, and are used to relieve immune suppression or enhance the immune response through the blockade of checkpoint ligands or receptors. ICIs have achieved great success in clinical cancer treatment. Monoamine oxidase A (MAOA) is a potent immune checkpoint of immunotherapy. Recently, it has been reported that MAOA inhibitors could enhance CD8⁺ T cell activity by upregulating 5-HT autocrine pathway in T cells. In this study, we synthesized doxorubicin (DOX) and isoniazid (INH, a MAOA inhibitor) conjugates through a pH sensitive hydrazone bond. Results of the in vivo studies showed that DOX-INH could effectively enhance the activity of CD8⁺ T cells and perform a synergistic anti-tumor effect with PD-L1 small molecular inhibitor (BMS202). In addition, in an orthotopic 4T1 breast cancer model, it was demonstrated that DOX-INH could inhibit the epithelial-mesenchymal transition process by blocking Shh, IL-6, and TGF-β signaling pathways, thereby inhibiting the growth and metastasis of breast cancer. Thus, a simple and effective small molecule conjugate produced by the combination of a chemotherapy drug and a MAOA inhibitor shows broad prospect in cancer therapy.

The application of antidepressant drugs in cancer treatment

Antidepressants refer to psychotropic drugs which are used to treat mental illness with prominent emotional depression symptoms. It was reported that antidepressants had associated with anti-carcinogenic function which was associated with various signaling pathways and changing of microenvironment. Its mechanism includes cell apoptosis, antiproliferative effects, mitochondria-mediated oxidative stress, DNA damaging, changing of immune response and inflammatory conditions, and acting by inhibiting multidrug resistance of cancer cells. Accumulated studies showed that antidepressants influenced the metabolic pathway of tumor cells. This review summarized recent developments with the impacts and mechanisms of 10 kinds of antidepressants in carcinostasis. Antidepressants are also used in combination therapy with typical anti-tumor drugs which shows a synergic effect in anti-tumor. By contrast, the promotion roles of antidepressants in increasing cancer recurrence risk, mortality, and morbidity are also included. Further clinical experiments and mechanism analyses needed to be achieved. A full understanding of the underlying mechanisms of antidepressants-mediated anticarcinogenic effects may provide new clues for cancer prevention and clinical treatment.

Monoamine oxidase A: An emerging therapeutic target in prostate cancer

Monoamine oxidase A (MAOA), a mitochondrial enzyme degrading biogenic and dietary amines, has been studied in the contexts of neuropsychiatry and neurological disorders for decades, but its importance in oncology, as best exemplified in prostate cancer (PC) to date, was only realized recently. PC is the most commonly diagnosed non-skin cancer and the second deadliest malignancy for men in the United States. In PC, the increased expression level of MAOA is correlated with dedifferentiated tissue microarchitecture and a worse prognosis. A wealth of literature has demonstrated that MAOA promotes growth, metastasis, stemness and therapy resistance in PC, mainly by increasing oxidative stress, augmenting hypoxia, inducing epithelial-to-mesenchymal transition, and activating the downstream principal transcription factor Twist1-dictated multiple context-dependent signaling cascades. Cancer-cell-derived MAOA also enables cancer-stromal cell interaction involving bone stromal cells and nerve cells by secretion of Hedgehog and class 3 semaphorin molecules respectively to modulate the tumor microenvironment in favor of invasion and metastasis. Further, MAOA in prostate stromal cells promotes PC tumorigenesis and stemness. Current studies suggest that MAOA functions in PC in both cell autonomous and non-autonomous manners. Importantly, clinically available monoamine oxidase inhibitors have shown promising results against PC in preclinical models and clinical trials, providing a great opportunity to repurpose them as a PC therapy. Here, we summarize recent advances in our understanding of MAOA roles and mechanisms in PC, present several MAOA-targeted strategies that have been nominated for treating PC, and discuss the unknowns of MAOA function and targeting in PC for future exploration.

Androgen Receptor Signaling Inhibition in Advanced Castration Resistance Prostate Cancer: What Is Expected for the Near Future?

The androgen signaling pathway is the cornerstone in the treatment of high risk or advanced prostate cancer patients. However, in recent years, different mechanisms of resistance have been defined in this field, limiting the efficacy of the currently approved antiandrogen drugs. Different therapeutic approaches are under research to assess the role of combination therapies against escape signaling pathways or the development of novel antiandrogen drugs to try to solve the primary or acquired resistance against androgen dependent or independent pathways. The present review aims to summarize the current state of androgen inhibition in the therapeutic algorithm of patients with advanced prostate cancer and the mechanisms of resistance to those available drugs. In addition, this review conducted a comprehensive overview of the main present and future research approaches in the field of androgen receptor inhibition to overcome these resistances and the potential new drugs under research coming into this setting.

Metabolic inhibitor screening identifies dihydrofolate reductase as an inducer of the tumor immune escape mediator CD24

Immune checkpoint inhibitors have improved the clinical management of some cancer cases, yet patients still fail to respond to immunotherapy. Dysregulated metabolism is a common feature of many cancers, and metabolites are known to modulate functions in cancer cells. To identify potential metabolic pathways involved in anti-tumor immune response, we employed a metabolic inhibitor-based drug screen in human lung cancer cell lines and examined expression changes in a panel of immune regulator genes. Notably, pharmacologic inhibition of dihydrofolate reductase (DHFR) downregulated cancer cell expression of cluster of differentiation 24 (CD24), an anti-phagocytic surface protein. Genetic modulation of DHFR resulted in decrease of CD24 expression, whereas tetrahydrofolate, the product of DHFR, enhanced CD24 expression. DHFR inhibition and the consequent CD24 decrease enhanced T cell-mediated tumor cell killing, whereas replenishment of DHFR or CD24 partially mitigated the immune-mediated tumor cell killing that resulted from methotrexate treatment in cancer cells. Moreover, publicly available clinical data analyses further revealed the link between DHFR, CD24, and the antitumor immune response in lung cancer patients. Our study highlights a novel connection between folate metabolism and the anti-tumor immune response and partially interprets how DHFR inhibitors lead to clinical benefits when combined with cancer immunotherapy agents.

FOXA1 inhibits hypoxia programs through transcriptional repression of HIF1A

Intratumoral hypoxia is associated with castration-resistant prostate cancer (CRPC), a lethal disease. FOXA1 is an epithelial transcription factor that is down-regulated in CRPC. We have previously reported that FOXA1 loss induces epithelial-mesenchymal transition (EMT) and cell motility through elevated TGFβ signaling. However, whether FOXA1 directly regulates hypoxia pathways of CRPC tumors has not been previously studied. Here we report that FOXA1 down-regulation induces hypoxia transcriptional programs, and FOXA1 level is negatively correlated with hypoxia markers in clinical prostate cancer (PCa) samples. Mechanistically, FOXA1 directly binds to an intragenic enhancer of HIF1A to inhibit its expression, and HIF1A, in turn, is critical in mediating FOXA1 loss-induced hypoxia gene expression. Further, we identify CCL2, a chemokine ligand that modulates tumor microenvironment and promotes cancer progression, as a crucial target of the FOXA1-HIF1A axis. We found that FOXA1 loss leads to immunosuppressive macrophage infiltration and increased cell invasion, dependent on HIF1A expression. Critically, therapeutic targeting of HIF1A-CCL2 using pharmacological inhibitors abolishes FOXA1 loss-induced macrophage infiltration and PCa cell invasion. In summary, our study reveals an essential role of FOXA1 in controlling the hypoxic tumor microenvironment and establishes the HIF1A-CCL2 axis as one mechanism of FOXA1 loss-induced CRPC progression.

CDK6 is upregulated and may be a potential therapeutic target in enzalutamide-resistant castration-resistant prostate cancer

Background

Androgen deprivation therapy (ADT) is still the first-line treatment of prostate cancer (PCa). However, after a certain period of therapy, primary PCa inevitably progresses into castration-resistant PCa (CRPC). Enzalutamide (Enz) is an androgen receptor (AR) signal inhibitor which can delay the progression of CRPC and increase survival of patients with metastatic CRPC. However, the mechanisms involved in enzalutamide-resistant (EnzR) CRPC are still controversial. In the study, we used bioinformatic methods to find potential genes that correlated with the occurrence of EnzR CRPC.

Methods

We collected RNA sequencing data of the EnzR CRPC cell line LNCaP (EnzR LNCaP) from GSE44905, GSE78201, and GSE150807. We found the hub genes from the three datasets. Then we tested the expression of the hub genes in different databases and the potential drugs that can affect the hub genes. Finally, we verified the hub gene expression and drug function.

Results

From GSE44905, GSE78201 and GSE150807, we found 45 differentially expressed genes (DEGs) between LNCaP and EnzR LNCaP. Ten hub genes were found in the protein–protein interaction (PPI) network. The expression of hub gene and survival analysis were analyzed by different databases. We found that cyclin-dependent kinase 6 (CDK6) was highly expressed in both the EnzR LNCaP cell and PCa patients. Ten potential small molecules could suppress CDK6 expression as per “CLUE COMMAND” findings. Finally, we found the expression of CDK6 increased in both PCa patients’ samples, CRPC and EnzR PCa cell lines. Three potential CDK6 inhibitors, namely apigenin, chrysin and fisetin, can decrease cell proliferation.

Conclusions

The study proved that the abnormal overexpression of CDK6 may be a reason behind EnzR CRPC occurrence and suppression CDK6 expression may help treat EnzR CRPC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40001-022-00730-y.

A Phase 1 Proof of Concept Study Evaluating the Addition of an LSD1 Inhibitor to Nab-Paclitaxel in Advanced or Metastatic Breast Cancer (EPI-PRIMED)

Objective

Lysine-Specific Demethylase-1 (LSD1) is overexpressed in breast cancer cells and facilitate mesenchymal properties which may contribute to therapeutic resistance and cancer progression. The purpose of this study was to investigate the safety of combination, nab-paclitaxel and phenelzine, an irreversible LSD1 inhibitor in patients with metastatic breast cancer (mBC).

Methods

Eligible patients with mBC were treated with nab-paclitaxel (100mg/m²) weekly for 3 weeks with one week break in a 28-day cycle. Dose escalation of phenelzine followed the Cumulative Cohort Design and phenelzine treatment commenced from day 2 of first cycle. Eleven patients were screened, and eligible patients were enrolled in cohorts with the dose of phenelzine ranging from 45mg to 90mg.

Results

The Optimum Biological Dose was established at 60mg of phenelzine daily in combination with nab-paclitaxel and considered as the recommended phase 2 dose. Most (95%) of adverse events were grade 1 or 2 with two grade 3 events being diarrhea and neutropenia at 45mg and 60mg phenelzine respectively, with no unexpected toxicity/deaths. Commonly reported toxicities were fatigue (n=4,50%), dizziness (n=6,75%), neutropenia (n=3,37.5%), peripheral neuropathy (n=3,37.5%), diarrhea (n=2,25%), and hallucination (n=2,25%). After a median follow up of 113 weeks, all patients showed disease progression on trial with 4 patients being alive at the time of data cut off, including one patient with triple negative breast cancer. Median progression-free survival was 34 weeks. Significant inhibition of LSD1 and suppression of mesenchymal markers in circulating tumor cells were noted.

Conclusion

Phenelzine in combination with nab-paclitaxel was well tolerated, without any unexpected toxicities in patients with mBC and demonstrated evidence of antitumor activity. For the first time, this proof-of-concept study showed in-vivo inhibition of LSD1 suppressed mesenchymal markers, which are known to facilitate generation of cancer stem cells with metastatic potential. Clinical Trial Registration: ClinicalTrials.Gov NCT03505528, UTN of U1111-1197-5518.

An updated patent review on monoamine oxidase (MAO) inhibitors

INTRODUCTION

: Monoamine oxidase (MAO) inhibitors are currently used as antidepressants (selective MAO-A inhibitors) or as co-adjuvants for neurodegenerative diseases (selective MAO-B inhibitors). The research within this field is attracting attention due to their crucial role in the modulation of brain functions, mood and cognitive activity, and monoamine catabolism.

AREAS COVERED

MAO inhibitors (2018-2021) are discussed according to their chemotypes. Structure-activity relationships are derived for each chemical scaffold (propargylamines, chalcones, indoles, benzimidazoles, (iso)coumarins, (iso)benzofurans, xanthones, and tetralones), while the chemical entities were divided into newly synthesized molecules and natural metabolites. The mechanism of action and type of inhibition are also considered. Lastly, new therapeutic applications are reported, which demonstrates the clinical potential of these inhibitors as well as the possibility of repurposing existing drugs for a variety of diseases.

EXPERT OPINION

MAO inhibitors here reported exhibit different potencies (from the micro- to nanomolar range) and isoform selectivity. These compounds are clinically licensed for multi-faceted neurodegenerative pathologies due to their ability to also act against other relevant targets (cholinesterases, inflammation, and oxidative stress). Moreover, the drug repurposing approach is an attractive strategy by which MAO inhibitors may be applied for the treatment of prostate cancer, inflammation, vertigo, and type 1 diabetes.

Design, Synthesis, and Biological Evaluation of Novel MAO-A Inhibitors Targeting Lung Cancer

Lung cancer is one of the most common causes of cancer-related deaths worldwide. Monoamine Oxidase-A (MAO-A) enzyme mediates the production of reactive oxygen species (ROS) that trigger DNA damage and oxidative injury of cells resulting in tumor initiation and progression. Available MAO-A inhibitors are used as antidepressants, however, their role as anticancer agents is still under investigation. Ligand- and structure-based drug design approaches guided the discovery and development of novel MAO-A inhibitors. A series of 1H indole-2-carboxamide derivatives was prepared and characterized using 1H-NMR, 13C-NMR, and IR. The antiproliferative effects of MAO-A inhibitors were evaluated using the cell viability assay (MTT), and MAO-A activity was evaluated using MAO-A activity assay. The presumed inhibitors significantly inhibited the growth of lung cell lines in a dose- and time dependent manner. The half maximal inhibitory concentration (IC₅₀) values of MAO-A inhibitors (S1, S2, S4, S7, and S10) were 33.37, 146.1, 208.99, 307.7, and 147.2 µM, respectively, in A549. Glide docking against MAO-A showed that the derivatives accommodate MAO-A binding cleft and engage with key binding residues. MAO-A inhibitors provide significant and consistent evidence on MAO-A activity in lung cancer and present a potential target for the development of new chemotherapeutic agents.

Heterocycle-containing tranylcypromine derivatives endowed with high anti-LSD1 activity

As regioisomers/bioisosteres of 1a, a 4-phenylbenzamide tranylcypromine (TCP) derivative previously disclosed by us, we report here the synthesis and biological evaluation of some (hetero)arylbenzoylamino TCP derivatives 1b-6, in which the 4-phenyl moiety of 1a was shifted at the benzamide C3 position or replaced by 2- or 3-furyl, 2- or 3-thienyl, or 4-pyridyl group, all at the benzamide C4 or C3 position. In anti-LSD1-CoREST assay, all the meta derivatives were more effective than the para analogues, with the meta thienyl analogs 4b and 5b being the most potent (IC₅₀ values = 0.015 and 0.005 μM) and the most selective over MAO-B (selectivity indexes: 24.4 and 164). When tested in U937 AML and prostate cancer LNCaP cells, selected compounds 1a,b, 2b, 3b, 4b, and 5a,b displayed cell growth arrest mainly in LNCaP cells. Western blot analyses showed increased levels of H3K4me2 and/or H3K9me2 confirming the involvement of LSD1 inhibition in these assays.

High expression of NPM1 via the Wnt/β-catenin signalling pathway might predict poor prognosis for patients with prostate adenocarcinoma

Prostate adenocarcinoma (PRAD) occurs only in males and has a higher incidence rate than other cancers. NPM1 is a nucleocytoplasmic shuttling protein that participates in the development of multiple tumours. The aim of this research was to explore the effect of the upregulation or downregulation of the NPM1 protein on the malignancy of prostate cancer and its possible signalling pathway. Prostate adenocarcinoma cell lines were used in this study, including RWPE-1, PC3, LNCap, and 22RV1 cells. Our research revealed that NPM1 was widely expressed in the PRAD cell lines, as determined by Western blotting, and that the levels of NPM1 protein were positively correlated with the degree of malignancy of the PRAD cell lines. Through interference and overexpression experiments, we found that PC3 cells growth was inhibited after NPM1 knockdown and that this inhibition was partly reversed by CTNNB1 overexpression; in contrast, PC3 cells growth was promoted after NPM1 overexpression, and this promotion was partly reversed by CTNNB1 knockdown, suggesting that NPM1 and CTNNB1 play important roles in the progression of prostate cancer cells via the Wnt/β-catenin signalling pathway. NPM1 may serve as an important biomarker and candidate therapeutic for patients with prostate cancer.

Comprehensive in Vitro Characterization of the LSD1 Small Molecule Inhibitor Class in Oncology

Lysine-specific demethylase 1 (LSD1 or KDM1A) is a chromatin modifying enzyme playing a key role in the cell cycle and cell differentiation and proliferation through the demethylation of histones and nonhistone substrates. In addition to its enzymatic activity, LSD1 plays a fundamental scaffolding role as part of transcription silencing complexes such as rest co-repressor (CoREST) and nucleosome remodeling and deacetylase (NuRD). A host of classical amine oxidase inhibitors such as tranylcypromine, pargyline, and phenelzine together with LSD1 tool compounds such as SP-2509 and GSK-LSD1 have been extensively utilized in LSD1 mechanistic cancer studies. Additionally, several optimized new chemical entities have reached clinical trials in oncology such as ORY-1001 (iadademstat), GSK2879552, SP-2577 (seclidemstat), IMG-7289 (bomedemstat), INCB059872, and CC-90011 (pulrodemstat). Despite this, no single study exists that characterizes them all under the same experimental conditions, preventing a clear interpretation of published results. Herein, we characterize the whole LSD1 small molecule compound class as inhibitors of LSD1 catalytic activity, disruptors of SNAIL/GFI1 (SNAG)-scaffolding protein-protein interactions, inducers of cell differentiation, and potential anticancer treatments for hematological and solid tumors to yield an updated, unified perspective of this field. Our results highlight significant differences in potency and selectivity among the clinical compounds with iadademstat being the most potent and reveal that most of the tool compounds have very low activity and selectivity, suggesting some conclusions derived from their use should be taken with caution.

The role of 5-HT metabolism in cancer

Serotonin (5-hydroxytryptamine, 5-HT) metabolism has long been linked to tumorigenesis and tumor progression. Numerous studies have shown the functions of 5-HT and its metabolites in the regulation of tumor biological processes like cell proliferation, invasion, metastasis, tumor angiogenesis and immunomodulatory through multi-step complex mechanisms. Reprogramming of 5-HT metabolism has been revealed in various tumors paving way for development of drugs that target enzymes, metabolites or receptors involved in 5-HT metabolic pathway. However, information on the role of 5-HT metabolism in cancer is scanty. This review briefly describes the main metabolic routes of 5-HT, the role of 5-HT metabolism in cancer and systematically summarizes the most recent advances in 5-HT metabolism-targeted cancer therapy.

Sizes and ligands tuned gold nanocluster acting as a new type of monoamine oxidase B inhibitor

Monoamine oxidase inhibitors (MAOIs) are a class of drugs that can be used in the treatment of Parkinson's disease, clinical depression, and anxiety by targeting monoamine oxidase B (MAO). However, the side effects of MAOIs drive the requirement of a new framework of enzyme inhibitors development. In this context, a new type of MAOI has been built on the framework of gold nanoclusters (AuNCs), realizing the transformation from no function of small molecules to MAOI function of ligand-modified AuNCs. The MAOI activity of fabricated AuNCs can be achieved by size control and specific ligands modification. In this work, AuNCs modified with cysteamine or 4-aminothiophenol, about 1-3 nm in size, were found to have MAOI activity (MAOI-like AuNCs) and their characterization has been extensively described. Meanwhile, the possible mechanism behind this MAOI activity has been explored and it is believed that the proper size of AuNCs with ligands containing amino groups can bind tightly with the entrance to active sites of MAO, blocking the enzyme interacting with its substrates, thereby realizing the function of MAOI. Last, the antimicrobial activity and the performance of the MAOI-like AuNCs in the human blood sample were explored and suggested that MAOI-like AuNCs do not possess strong antimicrobial activity and have no visualized side effect on blood cells, although the by-product peroxide of MAO reaction may reshape the white blood cells. The research in this work may shed some light on the development of a new type of enzyme inhibitor based on the framework of nanomaterials.

Targeting the glucocorticoid receptor signature gene Mono Amine Oxidase-A enhances the efficacy of chemo- and anti-androgen therapy in advanced prostate cancer

Despite increasing options for treatment of castration-resistant prostate cancer, development of drug resistance is inevitable. The glucocorticoid receptor (GR) is a prime suspect for acquired therapy resistance, as prostate cancer (PCa) cells are able to increase GR signaling during anti-androgen therapy and thereby circumvent androgen receptor (AR)-blockade and cell death. As standard AR-directed therapies fail to block the GR and GR inhibitors might result in intolerable side effects, the identification of GR signature genes, which are better suited for a targeted approach, is of clinical importance. Therefore, the specific epithelial and stromal GR signature was determined in cancer-associated fibroblasts as well as in abiraterone and enzalutamide-resistant cells after glucocorticoid (GC) treatment. Microarray and ChIP analysis identified MAO-A as a directly up-regulated mutual epithelial and stromal GR target, which is induced after GC treatment and during PCa progression. Elevated MAO-A levels were confirmed in in vitro cell models, in primary tissue cultures after GC treatment, and in patients after neoadjuvant chemotherapy with GCs. MAO-A expression correlates with GR/AR activity as well as with a reduced progression-free survival. Pharmacological MAO-A inhibition combined with 2nd generation AR signaling inhibitors or chemotherapeutics results in impaired growth of androgen-dependent, androgen-independent, and long-term anti-androgen-treated cells. In summary, these findings demonstrate that targeting MAO-A represents an innovative therapeutic strategy to synergistically block GR and AR dependent PCa cell growth and thereby overcome therapy resistance.

Kava root extracts hinder prostate cancer development and tumorigenesis by involvement of dual inhibition of MAO-A and LSD1

AIM

Here, we aim to evaluate the chemopreventive efficacy of kava root extracts (KRE) in transgenic adenocarcinoma of the mouse prostate (TRAMP) mice and investigate potential molecular targets of kavalactones, the main components of kava.

METHODS

TRAMP mice were administrated with KRE formulated food for different periods of time, and then the incidences of high-grade prostatic intraepithelial neoplasia (HG-PIN) and adenocarcinomas and tumor burdens were compared between vehicle control and KRE food fed groups. In addition, the inhibitory effect of the KRE and kavalactones on monoamine oxidase A (MAO-A) and lysine-specific demethylase 1 (LSD1) enzyme activities were examined by commercially available inhibitor screening kits. Histone H3 lysine 9 dimethylation was also evaluated in prostate cancer cells and tumor tissues using Western blotting analysis.

RESULTS

Dietary feeding of 0.3% and 0.6% KRE to TRAMP mice from ages of 6 weeks to 12 weeks inhibited HG-PIN by 43.5% and 59.7%, respectively, and prostate adenocarcinoma by 53.5% and 66.4%, respectively. In addition, 0.6% KRE fed TRAMP mice from ages of 6 weeks to 24 weeks exhibited a significant reduction of genitourinary weight (a surrogate of tumor burden) by 54.5% and reduced body weight gain. Furthermore, the KRE and kavalactones showed a significant inhibition of LSD1 and MAO-A enzyme activities.

CONCLUSION

Our results suggest that consumption of kava products through diet can delay prostate cancer development and progression and that kavalactones may be a new structure model for developing a potent dual inhibitor of LSD1 and MAO-A.

Mechanisms of enzalutamide resistance in castration-resistant prostate cancer and therapeutic strategies to overcome it

Prostate cancer is the second most common malignancy in men and androgen deprivation therapy is the first-line therapy. However, most cases will eventually develop castration-resistant prostate cancer after androgen deprivation therapy treatment. Enzalutamide is a second-generation androgen receptor antagonist approved by the Food and Drug Administration to treat patients with castration-resistant prostate cancer. Unfortunately, patients receiving enzalutamide treatment will ultimately develop resistance via various complicated mechanisms. This review examines the emerging information on these resistance mechanisms, including androgen receptor-related signalling pathways, glucocorticoid receptor-related pathways and metabolic effects. Notably, lineage plasticity and phenotype switching, gene polymorphisms and the relationship between microRNAs and drug resistance are addressed. Furthermore, potential therapeutic strategies for enzalutamide-resistant castration-resistant prostate cancer treatment are suggested, which can help discover more effective and specific regimens to overcome enzalutamide resistance.

Association of Monoamine Oxidase A with Tumor Burden and Castration Resistance in Prostate Cancer

BACKGROUND

Metastatic burden and aggressive behavior determine severity stratification and guide treatment decisions in prostate cancer (PCa). Monoamine oxidase A (MAOA) may promote tumor burden and drug/castration resistance in PCa. A positive association will pave the way for MAOA inhibitors such as moclobemide for PCa therapy.

OBJECTIVE

To analyze MAOA in peripheral blood mononuclear cells qualitatively and p38, c-Jun N-terminal kinases, nuclear factor kappa B, and their phosphorylated forms, vascular endothelial growth factor (angiogenesis), transforming growth factor beta, interleukin 6, and tumor necrosis factor-α (cytokines), Bcl-2 associated X, B-cell lymphoma 2, and P53 (apoptosis), prostate-specific membrane antigen, and epithelial cell adhesion molecules (surface markers) in plasma of patients with PCa.

METHODS

This was a 1-year pilot study in which patients with PCa were recruited and stratified into 2 groups and subgroups: treatment-naive with (M1) (n = 23) or without (M0) (n = 23) bone metastasis; hormone-sensitive prostate cancer (n = 26) or hormone/castration-resistant prostate cancer (n = 26). MAOA was detected using ELISA and other proteins were detected using immunoblotting technique.

RESULTS

MAOA was detected in 8.6% of M0 compared with 30.4% of M1 patients, and in 7.7% of hormone-sensitive compared with 27% of hormone/castration resistant PCa patients, associating it with bone metastasis and castration resistance. Multivariable regression analysis showed a correlation of MAOA with serum prostate-specific antigen, a marker for progression in PCa (Pearson correlation coefficient r = 0.30; P < 0.01). In patients with positive MAOA, there was overexpression of p38, phosphorylated-p38, c-Jun N-terminal kinases, phosphorylated c-Jun N-terminal kinases, nuclear factor kappa B, phosphorylated nuclear factor kappa B, transforming growth factor beta, vascular endothelial growth factor, interleukin 6, tumor necrosis factor α, Bcl-2 associated X, B-cell lymphoma 2, prostate-specific membrane antigen, and epithelial cell adhesion molecule in M1 compared with M0 group patients, associating these proteins with tumor burden. Overexpression of Bcl-2 associated X, tumor protein 53, c-Jun N-terminal kinases, nuclear factor kappa B, transforming growth factor beta, vascular endothelial growth factor, and prostate-specific membrane antigen and underexpression of B-cell lymphoma 2 and phosphorylated nuclear factor kappa B were observed in hormone-sensitive prostate cancer compared with hormone/castration-resistant prostate cancer, associating these proteins with castration resistance.

CONCLUSIONS

Association of key molecules of oncogenesis and metastasis with MAOA suggests that MAOA inhibitors such as moclobemide might be effective in the management of PCa.

Imipramine Inhibits Migration and Invasion in Metastatic Castration-Resistant Prostate Cancer PC-3 Cells via AKT-Mediated NF-κB Signaling Pathway

Imipramine (IMI) is a tricyclic synthetic antidepressant that is used to treat chronic psychiatric disorders, including depression and neuropathic pain. IMI also has inhibitory effects against various cancer types, including prostate cancer; however, the mechanism of its anticancer activity is not well understood. In the present study, we investigated the antimetastatic and anti-invasive effects of IMI in metastatic castration-resistant prostate cancer PC-3 cells, with an emphasis on the serine/threonine protein kinase AKT-mediated nuclear factor kappa B (NF-κB) signaling pathway. While IMI did not induce cell death, it attenuated PC-3 cell proliferation. According to the wound healing assay and invasion assay, migration and invasion in PC-3 cells were significantly inhibited by IMI in a dose-dependent manner. IMI significantly downregulated p-AKT protein expression but upregulated phospho-extracellular signal-regulated kinase (ERK1)/2 protein expression levels. Furthermore, IMI treatment resulted in decreased AKT-mediated downstream signaling, including p-inhibitor of κB kinase (IKK)α/β, p-inhibitor of κB (IκBα), and p-p65. Inhibited NF-κB signaling reduced the secretion of several proinflammatory cytokines and chemokine by PC-3 cells. Overall, our study explored the negative correlation between the use of antidepressants and prostate cancer progression, showing that IMI attenuated cell viability, migration, and invasion of PC-3 cells by suppressing the expression of AKT and NF-κB-related signaling proteins and secretion of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and monocyte chemoattractant protein-1 (MCP-1).