The antiproliferative and proapoptotic effects of cladosporols A and B are related to their different binding mode as PPARγ ligands

Cladosporols and PPARγ: Same Gun, Same Bullet, More Targets

Several natural compounds have been found to act as PPARγ agonists, thus regulating numerous biological processes, including the metabolism of carbohydrates and lipids, cell proliferation and differentiation, angiogenesis, and inflammation. Recently, Cladosporols, secondary metabolites purified from the fungus Cladosporium tenuissimum, have been demonstrated to display an efficient ability to control cell proliferation in human colorectal and prostate cancer cells through a PPARγ-mediated modulation of gene expression. In addition, Cladosporols exhibited a strong anti-adipogenetic activity in 3T3-L1 murine preadipocytes, preventing their in vitro differentiation into mature adipocytes. These data interestingly point out that the interaction between Cladosporols and PPARγ, in the milieu of different cells or tissues, might generate a wide range of beneficial effects for the entire organism affected by diabetes, obesity, inflammation, and cancer. This review explores the molecular mechanisms by which the Cladosporol/PPARγ complex may simultaneously interfere with a dysregulated lipid metabolism and cancer promotion and progression, highlighting the potential therapeutic benefits of Cladosporols for human health.

Proliferation and migration of PC-3 prostate cancer cells is counteracted by PPARγ-cladosporol binding-mediated apoptosis and a decreased lipid biosynthesis and accumulation

OBJECTIVES

Chemoprevention, consisting of the administration of natural and/or synthetic compounds, appears to be an alternative way to common therapeutical approaches to preventing the occurrence of various cancers. Cladosporols, secondary metabolites from Cladosporium tenuissimum, showed a powerful ability in controlling human colon cancer cell proliferation through a peroxisome proliferator-activated receptor gamma (PPARγ)-mediated modulation of gene expression. Hence, we carried out experiments to verify the anticancer properties of cladosporols in human prostate cancer cells. Prostate cancer represents one of the most widespread tumors in which several risk factors play a role in determining its high mortality rate in men.

MATERIALS AND METHODS

We assessed, by viability assays, PPARγ silencing and overexpression experiments and western blotting analysis, the anticancer properties of cladosporols in cancer prostate cell lines.

RESULTS

Cladosporols A and B selectively inhibited the proliferation of human prostate PNT-1A, LNCaP and PC-3 cells and their most impactful antiproliferative ability towards PC-3 prostate cancer cells, was mediated by PPARγ modulation. Moreover, the anticancer ability of cladosporols implied a sustained apoptosis. Finally, cladosporols negatively regulated the expression of enzymes involved in the biosynthesis of fatty acids and cholesterol, thus enforcing the relationship between prostate cancer development and lipid metabolism dysregulation.

CONCLUSION

This is the first work, to our knowledge, in which the role of cladosporols A and B was disclosed in prostate cancer cells. Importantly, the present study highlighted the potential of cladosporols as new therapeutical tools, which, interfering with cell proliferation and lipid pathway dysregulation, may control prostate cancer initiation and progression.

Multi-Faceted Role of Cancer-Associated Adipocytes in Colorectal Cancer

Colorectal cancer (CRC) is one of the most commonly diagnosed types of cancer, especially in obese patients, and the second cause of cancer-related death worldwide. Based on these data, extensive research has been performed over the last decades to decipher the pivotal role of the tumor microenvironment (TME) and its cellular and molecular components in CRC development and progression. In this regard, substantial progress has been made in the identification of cancer-associated adipocytes' (CAAs) characteristics, considering their active role in the CCR tumor niche, by releasing a panel of metabolites, growth factors, and inflammatory adipokines, which assist the cancer cells' development. Disposed in the tumor invasion front, CAAs exhibit a fibroblastic-like phenotype and establish a bidirectional molecular dialogue with colorectal tumor cells, which leads to functional changes in both cell types and contributes to tumor progression. CAAs also modulate the antitumor immune cells' response and promote metabolic reprogramming and chemotherapeutic resistance in colon cancer cells. This review aims to report recent cumulative data regarding the molecular mechanisms of CAAs' differentiation and their activity spectrum in the TME of CRC. A better understanding of CAAs and the molecular interplay between CAAs and tumor cells will provide insights into tumor biology and may open the perspective of new therapeutic opportunities in CRC patients.

The Role of PPARs in Breast Cancer

Breast cancer is a malignant tumor with high morbidity and lethality. Its pathogenesis is related to the abnormal expression of many genes. The peroxisome proliferator-activated receptors (PPARs) are a class of ligand-dependent transcription factors in the nuclear receptor superfamily. They can regulate the transcription of a large number of target genes, which are involved in life activities such as cell proliferation, differentiation, metabolism, and apoptosis, and regulate physiological processes such as glucose metabolism, lipid metabolism, inflammation, and wound healing. Further, the changes in its expression are associated with various diseases, including breast cancer. The experimental reports related to "PPAR" and "breast cancer" were retrieved from PubMed since the discovery of PPARs and summarized in this paper. This review (1) analyzed the roles and potential molecular mechanisms of non-coordinated and ligand-activated subtypes of PPARs in breast cancer progression; (2) discussed the correlations between PPARs and estrogen receptors (ERs) as the nuclear receptor superfamily; and (3) investigated the interaction between PPARs and key regulators in several signaling pathways. As a result, this paper identifies PPARs as targets for breast cancer prevention and treatment in order to provide more evidence for the synthesis of new drugs targeting PPARs or the search for new drug combination treatments.

Fungal Naphthalenones; Promising Metabolites for Drug Discovery: Structures, Biosynthesis, Sources, and Pharmacological Potential

Fungi are well-known for their abundant supply of metabolites with unrivaled structure and promising bioactivities. Naphthalenones are among these fungal metabolites, that are biosynthesized through the 1,8-dihydroxy-naphthalene polyketide pathway. They revealed a wide spectrum of bioactivities, including phytotoxic, neuro-protective, cytotoxic, antiviral, nematocidal, antimycobacterial, antimalarial, antimicrobial, and anti-inflammatory. The current review emphasizes the reported naphthalenone derivatives produced by various fungal species, including their sources, structures, biosynthesis, and bioactivities in the period from 1972 to 2021. Overall, more than 167 references with 159 metabolites are listed.

Iron catalyzed tandem ring opening/1,6-conjugate addition of cyclopropanols with p-quinone methides: new access to γ,γ-diaryl ketones

An iron(III) catalyzed tandem ring opening/1,6-conjugate addition of cyclopropanols to p-quinone methides leading to γ,γ-diaryl ketones has been described. This catalytic protocol provides a novel and efficient method to access γ,γ-diaryl ketone derivatives in good to excellent yields with high functional group tolerance. Importantly, γ,γ-diaryl ketone can be further functionalized to give a versatile set of useful products.

Titanium(IV)-Mediated Ring-Opening/Dehydroxylative Cross-Coupling of Diaryl-Substituted Methanols with Cyclopropanol Derivatives

A titanium(IV)-mediated ring-opening/dehydroxylative cross-coupling of diaryl-substituted methanols with a cyclopropanol derivative was developed. The reactions proceeded efficiently to provide synthetically useful γ,γ-diaryl esters in moderate to good yields, which could be applied to the functionalization of complex molecules derived from bioactive fenofibrate and isoxepac and the synthesis of a precursor of Zoloft.

PPAR-γ Modulators as Current and Potential Cancer Treatments

Worldwide, cancer has become one of the leading causes of mortality. Peroxisome Proliferator-Activated Receptors (PPARs) is a family of critical sensors of lipids as well as regulators of diverse metabolic pathways. They are also equipped with the capability to promote eNOS activation, regulate immunity and inflammation response. Aside from the established properties, emerging discoveries are also made in PPAR's functions in the cancer field. All considerations are given, there exists great potential in PPAR modulators which may hold in the management of cancers. In particular, PPAR-γ, the most expressed subtype in adipose tissues with two isoforms of different tissue distribution, has been proven to be able to inhibit cell proliferation, induce cell cycle termination and apoptosis of multiple cancer cells, promote intercellular adhesion, and cripple the inflamed state of tumor microenvironment, both on transcriptional and protein level. However, despite the multi-functionalities, the safety of PPAR-γ modulators is still of clinical concern in terms of dosage, drug interactions, cancer types and stages, etc. This review aims to consolidate the functions of PPAR-γ, the current and potential applications of PPAR-γ modulators, and the challenges in applying PPAR-γ modulators to cancer treatment, in both laboratory and clinical settings. We sincerely hope to provide a comprehensive perspective on the prospect of PPAR-γ applicability in the field of cancer treatment.

Cladosporols A and B, two natural peroxisome proliferator-activated receptor gamma (PPARγ) agonists, inhibit adipogenesis in 3T3-L1 preadipocytes and cause a conditioned-culture-medium-dependent arrest of HT-29 cell proliferation

BACKGROUND

Obesity and type 2 diabetes mellitus, which are widespread throughout the world, require therapeutic interventions targeted to solve clinical problems (insulin resistance, hyperglycaemia, dyslipidaemia and steatosis). Several natural compounds are now part of the therapeutic repertoire developed to better manage these pathological conditions. Cladosporols, secondary metabolites from the fungus Cladosporium tenuissimum, have been characterised for their ability to control cell proliferation in human colon cancer cell lines through peroxisome proliferator-activated receptor gamma (PPARγ)-mediated modulation of gene expression. Here, we report data concerning the ability of cladosporols to regulate the differentiation of murine 3T3-L1 preadipocytes.

METHODS

Cell counting and MTT assay were used for analysing cell proliferation. RT-PCR and Western blotting assays were performed to evaluate differentiation marker expression. Cell migration was analysed by wound-healing assay.

RESULTS

We showed that cladosporol A and B inhibited the storage of lipids in 3T3-L1 mature adipocytes, while their administration did not affect the proliferative ability of preadipocytes. Moreover, both cladosporols downregulated mRNA and protein levels of early (C/EBPα and PPARγ) and late (aP2, LPL, FASN, GLUT-4, adiponectin and leptin) differentiation markers of adipogenesis. Finally, we found that proliferation and migration of HT-29 colorectal cancer cells were inhibited by conditioned medium from cladosporol-treated 3T3-L1 cells compared with the preadipocyte conditioned medium.

CONCLUSIONS

To our knowledge, this is the first report describing that cladosporols inhibit in vitro adipogenesis and through this inhibition may interfere with HT-29 cancer cell growth and migration.

GENERAL SIGNIFICANCE

Cladosporols are promising tools to inhibit concomitantly adipogenesis and control colon cancer initiation and progression.

Tetrazanbigen Derivatives as Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) Partial Agonists: Design, Synthesis, Structure-Activity Relationship, and Anticancer Activities

Tetrazanbigen (TNBG) is a novel sterol isoquinoline derivative with poor water solubility and moderate inhibitory effects on human cancer cell lines via lipoapoptosis induction. Herein, we developed a series of novel TNBG analogues with improved water solubility and antiproliferative activities. The CCK-8 assay enabled us to identify a novel compound, 14g, which strongly inhibited HepG2 and A549 cell growth with IC₅₀ values of 0.54 and 0.47 μM, respectively. The anticancer effects might be explained by the partial activation and upregulation of PPARγ expression, as indicated by the transactivation assay and western blotting evaluation. Furthermore, the in vitro antiproliferative activity was verified in an in vivo xenograft model in which 14g strongly reduced tumor growth at a dose of 10 mg/kg. In line with these positive observations, 14g exhibited an excellent water solubility of 31.4 mg/mL, which was more than 1000-fold higher than that of TNBG (4 μg/mL). Together, these results suggest that 14g is a promising anticancer therapeutic that deserves further investigation.

Alternol/Alteronol: Potent Anti-cancer Compounds With Multiple Mechanistic Actions

Alternol and its oxidate isomer Alteronol are small compounds isolated from the fermentation of a mutant fungus obtained from Taxus brevifolia bark. Preclinical studies showed their potent anti-cancer activities, including attenuating cellular survival pathways, altering protein levels of cell cycle regulators, activating xanthine dehydrogenase to cause accumulation of cellular reactive oxygen species and disrupting cell metabolism by disturbing four Krebs cycle enzymes specifically in malignant cells while having no significant effect on benign cells. In cancer cell culture models, Alternol or Alteronol exert their anti-cancer effect by inducing cell cycle arrest and triggering apoptotic cell death. In mice xenograft models, Alternol or Alteronol potently suppresses tumor growth with no obvious toxicity to the host with a wide therapeutic index over 30-fold. In conclusion, Alternol or Alteronol possess a great potential and feasibility to be developed as an effective anti-tumor therapeutic.

PPARγ: Potential Therapeutic Target for Ailments Beyond Diabetes and its Natural Agonism

Intense research interests have been observed in establishing PPAR gamma as a therapeutic target for diabetes. However, PPARγ is also emerging as an important therapeutic target for varied disease states other than type 2 diabetes like neurodegenerative disorders, cancer, spinal cord injury, asthma, and cardiovascular problems. Furthermore, glitazones, the synthetic thiazolidinediones, also known as insulin sensitizers, are the largely studied PPARγ agonists and the only ones approved for the treatment of type 2 diabetes. However, they are loaded with side effects like fluid retention, obesity, hepatic failure, bone fractures, and cardiac failure; which restrict their clinical application. Medicinal plants used traditionally are the sources of bioactive compounds to be used for the development of successful drugs and many structurally diverse natural molecules are already established as PPARγ agonists. These natural partial agonists when compared to full agonist synthetic thiazolidinediones led to weaker PPARγ activation with lesser side effects but are not thoroughly investigated. Their thorough characterization and elucidation of mechanistic activity might prove beneficial for counteracting diseases by modulating PPARγ activity through dietary changes. We aim to review the therapeutic significance of PPARγ for ailments other than diabetes and highlight natural molecules with potential PPARγ agonistic activity.

Rational drug design, synthesis, and biological evaluation of novel chiral tetrahydronaphthalene-fused spirooxindole as MDM2-CDK4 dual inhibitor against glioblastoma

Simultaneous inhibition of MDM2 and CDK4 may be an effective treatment against glioblastoma. A collection of chiral spirocyclic tetrahydronaphthalene (THN)-oxindole hybrids for this purpose have been developed. Appropriate stereochemistry in THN-fused spirooxindole compounds is key to their inhibitory activity: selectivity differed by over 40-fold between the least and most potent stereoisomers in time-resolved FRET and KINOMEscan® in vitro assays. Studies in glioblastoma cell lines showed that the most active compound ent-4g induced apoptosis and cell cycle arrest by interfering with MDM2 -P53 interaction and CDK4 activation. Cells treated with ent-4g showed up-regulation of proteins involved in P53 and cell cycle pathways. The compound showed good anti-tumor efficacy against glioblastoma xenografts in mice. These results suggested that rational design, asymmetric synthesis and biological evaluation of novel tetrahydronaphthalene fused spirooxindoles could generate promising MDM2-CDK4 dual inhibitors in glioblastoma therapy.

Nickel-Catalyzed α-Carbonylalkylarylation of Vinylarenes: Expedient Access to γ,γ-Diarylcarbonyl and Aryltetralone Derivatives

We report a Ni-catalyzed regioselective α-carbonylalkylarylation of vinylarenes with α-halocarbonyl compounds and arylzinc reagents. The reaction works with primary, secondary, and tertiary α-halocarbonyl molecules, and electronically varied arylzinc reagents. The reaction generates γ,γ-diarylcarbonyl derivatives with α-secondary, tertiary, and quaternary carbon centers. The products can be readily converted to aryltetralones, including a precursor to Zoloft, an antidepressant drug.

Free Fatty Acids Promote the Development of Prostate Cancer by Upregulating Peroxisome Proliferator-Activated Receptor Gamma

Introduction

As one of the most common forms of cancer that threatens men's health, prostate cancer (PCa) is under a trend of increasing morbidity and mortality in most countries. More and more studies have pointed out that obesity is closely linked to the occurrence and development of PCa, although there are still many undiscovered molecular mechanisms between the two.

Methods

In the present study, we compare serum lipid levels in patients with PCa and normal individuals. PCa cells (PC3 and 22RV1) were cultured in vitro, the TC/TG/HDL/GLU assay kit was used to detect the glucose and lipid metabolism level of PCa cells, the flow cytometry technique was used to detect the proliferation ability of PCa cells, and the Transwell was used to detect the invasion and migration ability of PCa cells. Western blot/quantitative real-time PCR was used to detect peroxisome proliferator-activated receptor γ (PPARγ) and vimentin/vascular endothelial growth factor-A (VEGF-A) expression levels, and immunohistochemistry was used to observe tumor-associated gene expression levels in nude mice. All data were analysed using the Independent samples t-test or rank sum test.

Results

We found higher levels of FFA in the serum of patients with PCa. In vitro experiments have demonstrated that high levels of FFA can promote the proliferation, migration and invasion of two PCa cells (PC3 and 22RV1) and affect the energy metabolism of PCa cells. The upregulated PPARγ plays a key role in this process, and vimentin may be involved in this signaling pathway.

Conclusion

We infer that high levels of FFA may promote PCa development by upregulating PPARγ expression.

Racemic 3,4-dihydro-4-naphthyl-naphthalen-1(2H)-ones from Juglans regia flowers

Three previously undescribed (±)-3,4-dihydro-4-naphthyl-naphthalen-1(2H)-one derivatives were isolated from Juglans regia flowers. Elucidation of the 2D structures of these first-reported compounds was completed via regular spectroscopic methods. The assignment of racemic nature of these compounds was achieved using the examination of their chiral HPLC profiles. (±)-2,3-Dihydro-4',8,8'-trihydroxy-(1,1'-binaphthalen)-4(1H)-one, (±)-2,3-dihydro-4',5,8,8'-tetrahydroxy-(1,1'-binaphthalen)-4(1H)-one, and (±)-2,3-dihydro-1',5,5',8-tetrahydroxy-(1,2'-binaphthalen)-4(1H)-one were the structures of these racemic compounds, all taking on central chirality. The resolution of all the racemic compounds was conducted and achieved using a chiral HPLC procedure. The absolute configurations of the three isolated pairs of enantiomers were assigned via time-dependent density functional theory calculations from the electronic circular dichroism data. The findings in this paper demonstrated that the relevant biochemical reactions for the construction of these 3,4-dihydro-4-naphthyl-naphthalen-1(2H)-one derivatives in the test plant are nonselective. The (±)-2,3-dihydro-4',8,8'-trihydroxy-(1,1'-binaphthalen)-4(1H)-one showed selective inhibitory activity on tumor cells growth, preliminarily supporting the application of Juglans regia flowers to protect against cancers in a few Chinese folk areas.

Chiral phenoxyacetic acid analogues inhibit colon cancer cell proliferation acting as PPARγ partial agonists

Peroxisome Proliferator-Activated Receptor γ (PPARγ) is an important sensor at the crossroad of diabetes, obesity, immunity and cancer as it regulates adipogenesis, metabolism, inflammation and proliferation. PPARγ exerts its pleiotropic functions upon binding of natural or synthetic ligands. The molecular mechanisms through which PPARγ controls cancer initiation/progression depend on the different mode of binding of distinctive ligands. Here, we analyzed a series of chiral phenoxyacetic acid analogues for their ability to inhibit colorectal cancer (CRC) cells growth by binding PPARγ as partial agonists as assessed in transactivation assays of a PPARG-reporter gene. We further investigated compounds (R,S)-3, (S)-3 and (R,S)-7 because they combine the best antiproliferative activity and a limited transactivation potential and found that they induce cell cycle arrest mainly via upregulation of p21^waf1/cip1. Interestingly, they also counteract the β-catenin/TCF pathway by repressing c-Myc and cyclin D1, supporting their antiproliferative effect. Docking experiments provided insight into the binding mode of the most active compound (S)-3, suggesting that its partial agonism could be related to a better stabilization of H3 rather than H11 and H12. In conclusion, we identified a series of PPARγ partial agonists affecting distinct pathways all leading to strong antiproliferative effects. These findings may pave the way for novel therapeutic strategies in CRC.

A compound-based proteomic approach discloses 15-ketoatractyligenin methyl ester as a new PPARγ partial agonist with anti-proliferative ability

Proteomics based approaches are emerging as useful tools to identify the targets of bioactive compounds and elucidate their molecular mechanisms of action. Here, we applied a chemical proteomic strategy to identify the peroxisome proliferator-activated receptor γ (PPARγ) as a molecular target of the pro-apoptotic agent 15-ketoatractyligenin methyl ester (compound 1). We demonstrated that compound 1 interacts with PPARγ, forms a covalent bond with the thiol group of C285 and occupies the sub-pocket between helix H3 and the β-sheet of the ligand-binding domain (LBD) of the receptor by Surface Plasmon Resonance (SPR), mass spectrometry-based studies and docking experiments. 1 displayed partial agonism of PPARγ in cell-based transactivation assays and was found to inhibit the AKT pathway, as well as its downstream targets. Consistently, a selective PPARγ antagonist (GW9662) greatly reduced the anti-proliferative and pro-apoptotic effects of 1, providing the molecular basis of its action. Collectively, we identified 1 as a novel PPARγ partial agonist and elucidated its mode of action, paving the way for therapeutic strategies aimed at tailoring novel PPARγ ligands with reduced undesired harmful side effects.