Microtubule disrupting agent-mediated inhibition of cancer cell growth is associated with blockade of autophagic flux and simultaneous induction of apoptosis

Apigenin-6-C-glucoside ameliorates MASLD in rodent models via selective agonism of adiponectin receptor 2

Adiponectin plays key roles in energy metabolism and ameliorates inflammation, oxidative stress, and mitochondrial dysfunction via its primary receptors, adiponectin receptors -1 and 2 (AdipoR1 and AdipoR2). Systemic depletion of adiponectin causes various metabolic disorders, including MASLD; however adiponectin supplementation is not yet achievable owing to its large size and oligomerization-associated complexities. Small-molecule AdipoR agonists, thus, may provide viable therapeutic options against metabolic disorders. Using a novel luciferase reporter-based assay here, we have identified Apigenin-6-C-glucoside (ACG), but not apigenin, as a specific agonist for the liver-rich AdipoR isoform, AdipoR2 (EC50: 384 pM) with >10000X preference over AdipoR1. Immunoblot analysis in HEK-293 overexpressing AdipoR2 or HepG2 and PLC/PRF/5 liver cell lines revealed rapid AMPK, p38 activation and induction of typical AdipoR targets PGC-1α and PPARα by ACG at a pharmacologically relevant concentration of 100 nM (reported cMax in mouse; 297 nM). ACG-mediated AdipoR2 activation culminated in a favorable modulation of key metabolic events, including decreased inflammation, oxidative stress, mitochondrial dysfunction, de novo lipogenesis, and increased fatty acid β-oxidation as determined by immunoblotting, QRT-PCR and extracellular flux analysis. AdipoR2 depletion or AMPK/p38 inhibition dampened these effects. The in vitro results were recapitulated in two different murine models of MASLD, where ACG at 10 mg/kg body weight robustly reduced hepatic steatosis, fibrosis, proinflammatory macrophage numbers, and increased hepatic glycogen content. Together, using in vitro experiments and rodent models, we demonstrate a proof-of-concept for AdipoR2 as a therapeutic target for MASLD and provide novel chemicobiological insights for the generation of translation-worthy pharmacological agents.

Structural and solution speciation studies on selected [Cu(NN)(OO)] complexes and an investigation of their biomimetic activity, ROS generation and their cytotoxicity in normoxic, hypoxic and anoxic environments in MCF-7 breast cancer-derived cells

Reactive oxygen species(ROS) generation with subsequent DNA damage is one of the principle mechanisms of action assigned to copper-based anticancer complexes. The efficacy of this type of chemotherapeutic may be reduced in the low oxygen environment of tumours. In this study the cytotoxicity of three complexes, [Cu(dips)(phen)] (1), [Cu(ph)(phen)]·2H2O (2) and [Cu(ph)(bpy)]·H2O (3) (disp: 3,5-diisopropylsalicylate, phen: 1,10- phenanthroline, ph: phthalate, bpy: 2,2'-bipyridyl) were assessed for anticancer activity in the breast-cancer derived MCF-7 line under normoxic, hypoxic and anoxic conditions. In an immortalised keratinocyte HaCaT cell line, the cytotoxicity of complexes 2 and 3 was significantly reduced under both normoxic and hypoxic conditions, whilst the cytotoxicity of complex 1 was increased under hypoxic conditions. The ability of the complexes to generate ROS in the MCF-7 cell line was evaluated as was their ability to act as superoxide dismutase(SOD) and catalase mimics using a yeast cell assay. ROS generation was significant for complexes 2 and 3, less so for complex 1 though all three complexes had SOD mimetic ability. Given the ternary nature of the complexes, solution speciation studies were undertaken but were only successful for complex 3, due to solubility issues with the other two complexes. The concentration distribution of various species, formed in aqueous solution, was evaluated as a function of pH and confirmed that complex 3 is the dominant species at physiological pH in the mM concentration range. However, as its concentration diminishes, it experiences a progressive dissociation, leading to the formation of binary complexes of bpy alongside unbound phthalate.

Inhibition of p21 activates Akt kinase to trigger ROS-induced autophagy and impacts on tumor growth rate

Owing to its ability to induce cellular senescence, inhibit PCNA, and arrest cell division cycle by negatively regulating CDKs as well as being a primary target of p53, p21 is traditionally considered a tumor suppressor. Nonetheless, several reports in recent years demonstrated its pro-oncogenic activities such as apoptosis inhibition by cytosolic p21, stimulation of cell motility, and promoting assembly of cyclin D-CDK4/6 complex. These opposing effects of p21 on cell proliferation, supported by the observations of its inconsistent expression in human cancers, led to the emergence of the concept of "antagonistic duality" of p21 in cancer progression. Here we demonstrate that p21 negatively regulates basal autophagy at physiological concentration. Akt activation, upon p21 attenuation, driven ROS accumulation appears to be the major underlying mechanism in p21-mediated modulation of autophagy. We also find p21, as a physiological inhibitor of autophagy, to have oncogenic activity during early events of tumor development while its inhibition favors survival and growth of cancer cells in the established tumor. Our data, thereby, reveal the potential role of autophagy in antagonistic functional duality of p21 in cancer.

Inhibiting Cytoprotective Autophagy in Cancer Therapy: An Update on Pharmacological Small-Molecule Compounds

Autophagy is a self-degradation process in which damaged proteins and organelles are engulfed into autophagosomes for digestion and eventually recycled for cellular metabolism to maintain intracellular homeostasis. Accumulating studies have reported that autophagy has the Janus role in cancer as a tumor suppressor or an oncogenic role to promote the growth of established tumors and developing drug resistance. Importantly, cytoprotective autophagy plays a prominent role in many types of human cancers, thus inhibiting autophagy, and has been regarded as a promising therapeutic strategy for cancer therapy. Here, we focus on summarizing small-molecule compounds inhibiting the autophagy process, as well as further discuss other dual-target small-molecule compounds, combination strategies, and other strategies to improve potential cancer therapy. Therefore, these findings will shed new light on exploiting more small-molecule compounds inhibiting cytoprotective autophagy as candidate drugs for fighting human cancers in the future.

The Tubulin Code and Tubulin-Modifying Enzymes in Autophagy and Cancer

Simple Summary

Microtubules are tubulin polymers that constitute the structure of eukaryotic cells. They control different cell functions that are often deregulated in cancer, such as cell shape, cell motility and the intracellular movement of organelles. Here, we focus on the crucial role of tubulin modifications in determining different cancer characteristics, including metastatic cell migration and therapy resistance. We also discuss the influence of microtubule modifications on the autophagic process—the cellular degradation pathway that influences cancer growth. We discuss findings showing that inducing microtubule modifications can be used as a means to kill cancer cells by inhibiting autophagy.

Abstract

Microtubules are key components of the cytoskeleton of eukaryotic cells. Microtubule dynamic instability together with the “tubulin code” generated by the choice of different α- and β- tubulin isoforms and tubulin post-translational modifications have essential roles in the control of a variety of cellular processes, such as cell shape, cell motility, and intracellular trafficking, that are deregulated in cancer. In this review, we will discuss available evidence that highlights the crucial role of the tubulin code in determining different cancer phenotypes, including metastatic cell migration, drug resistance, and tumor vascularization, and the influence of modulating tubulin-modifying enzymes on cancer cell survival and aggressiveness. We will also discuss the role of post-translationally modified microtubules in autophagy—the lysosomal-mediated cellular degradation pathway—that exerts a dual role in many cancer types, either promoting or suppressing cancer growth. We will give particular emphasis to the role of tubulin post-translational modifications and their regulating enzymes in controlling the different stages of the autophagic process in cancer cells, and consider how the experimental modulation of tubulin-modifying enzymes influences the autophagic process in cancer cells and impacts on cancer cell survival and thereby represents a new and fruitful avenue in cancer therapy.

W436, a novel SMART derivative, exhibits anti-hepatocarcinoma activity by inducing apoptosis and G2/M cell cycle arrest in vitro and in vivo and induces protective autophagy

Hepatocellular carcinoma (HCC) is considered one of the most common primary liver cancers and the second leading cause of cancer-associated mortality around the world annually. Therefore, it is urgent to develop novel drugs for HCC therapy. We synthesized a novel 4-substituted-methoxybenzoyl-aryl-thiazole (SMART) analog, (5-(4-aminopiperidin-1-yl)-2-phenyl-2H-1,2,3-triazol-4-yl) (3,4,5-trimethoxyphenyl) methanone (W436), with higher solubility, stability, and antitumor activity than SMART against HCC cells in vivo. The purpose of this study was to investigate the mechanisms by which W436 inhibited cell growth in HCC cells. We observed that W436 inhibited the proliferation of HepG2 and Hep3B cells in a dose-dependent manner. Importantly, the anticancer activity of W436 against HCC cells was even higher than that of SMART in vivo. In addition, the antiproliferative effects of W436 on HCC cells were associated with G2/M cell cycle arrest and apoptosis via the activation of reactive oxygen species-mediated mitochondrial apoptotic pathway. W436 also induced protective autophagy by inhibiting the protein kinase B/mammalian target of rapamycin pathway. At the same time, W436 treatment inhibited the cell adhesion and invasion as well as the process of epithelial-to-mesenchymal transition Taken together, our results showed that W436 had the promising potential for the therapeutic treatment of HCC with improved solubility, stability, and bioavailability.

Demethylzeylasteral Exerts Antitumor Effects via Disruptive Autophagic Flux and Apoptotic Cell Death in Human Colorectal Cancer Cells and Increases Cell Chemosensitivity to 5-Fluorouracil

BACKGROUND

Demethylzeylasteral (ZST93), a pharmacologically active triterpenoid monomer extracted from Tripterygium wilfordii Hook F (TWHF), has been reported to exert antineoplastic effects in several cancer cell types. However, the anti-tumour effects of ZST93 in human colorectal cancer (CRC) cells are unknown.

OBJECTIVE

The aim of the present study was to evaluate the antitumor effects of ZST93 on cell cycle arrest, disruptive autophagic flux, apoptotic cell death, and enhanced chemosensitivity to 5-FU in humans CRC cells.

METHODS

The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide(MTT) assay, colony formation assay, flow cytometry, immunoblotting, immunofluorescence, 5-ethynyl-20-deoxyuridine (EdU) incorporation assay, and autophagy analysis were used to evaluate the effects of ZST93 on cell viability, cell cycle progression, apoptosis and autophagy in two human CRC cell lines. Moreover, ZST93's combined anti-tumour effects with 5-fluorouracil (5-FU) were evaluated.

RESULTS

ZST93 inhibited CRC cell proliferation and growth. It was responsible for blocked cell cycle transition by arresting CRC cells in the G0/G1 phase via down-regulation of CDK4, CDK6, Cyclin D1, and c-MYC. Moreover, ZST93 induced suppressive autophagic flux and caspase-3-dependent cell death, which were further strengthened by the blocking of the autophagy process using chloroquine (CQ). Moreover, ZST93 enhanced CRC cells' chemosensitivity to 5-FU via modulation of autophagy and apoptosis.

CONCLUSION

ZST93 exerts anti-tumour effects via disruptive autophagic flux and apoptotic cell death in human CRC cells and increases cell chemosensitivity to 5-FU. These results provide insights into the utilisation of ZST93 as an adjuvant or direct autophagy inhibitor and suggest ZST93 as a novel therapeutic strategy for treating CRC.

Gedunin isolated from the mangrove plant Xylocarpus granatum exerts its anti-proliferative activity in ovarian cancer cells through G2/M-phase arrest and oxidative stress-mediated intrinsic apoptosis

Gedunin is a natural tetranorterpenoid secondary metabolite found in plants of the Meliaceae family, which has been reported for its antiparasitic, antifungal and anticancer activities. Here, we describe the molecular mechanisms underlying the in vitro anti proliferative activity of gedunin (isolated from the mangrove plant Xylocarpus granatum) in human ovarian cancer cells. We observed that gedunin triggered severe ROS generation leading to DNA damage and cell cycle arrest in G2/M phase thus inhibiting cell proliferation. ROS upregulation also led to mitochondrial stress and membrane depolarization, which eventually resulted in mitochondria-mediated apoptosis following cytochrome C release, caspase 9, 3 activation, and PARP cleavage. Transmission electron microscopy of gedunin treated cells revealed sub-cellular features typical of apoptosis. Moreover, an upregulation in stress kinases like phospho-ERK 1/2, phospho-p38 and phospho-JNK was also observed in gedunin treated cells. Free radical scavenger N-Acetyl-L-Cysteine (NAC) reversed all these effects resulting in increased cell survival, abrogation of cell cycle arrest, rescue of mitochondrial membrane potential and suppression of apoptotic markers. Interestingly, gedunin is also an inhibitor of the evolutionarily conserved molecular chaperone Heat Shock Protein 90 (hsp90) responsible for maintaining cellular homeostasis. Targeting this chaperone could be an attractive strategy for developing cancer therapeutics since many oncogenic proteins are also client proteins of hsp90. Collectively, our findings provide insights into the molecular mechanism of action of gedunin, which may aid drug development efforts against ovarian cancer.

Preclinical and clinical studies into the bioactivity of low-dose naltrexone (LDN) for oncotherapy

Naltrexone (NTX) is a nonspecific opioid antagonist that exerts pharmacological effects on the opioid axis by blocking opioid receptors distributed in cytoplastic and nuclear regions. NTX has been used in opioid use disorder (OUD), immune-associated diseases, alcoholism, obesity, and chronic pain for decades. However, low-dose naltrexone (LDN) also exhibits remarkable inhibition of DNA synthesis, viability, and other functions in numerous cancers and is involved in immune remodeling against tumor invasion and chemical toxicity. The potential anticancer activity of LDN is a focus of basic research. Herein, we summarize the associated studies on LDN oncotherapy to highlight the potential mechanisms and prospective clinical applications.

Beclin-1 is a Promising Prognostic Biomarker in a Specific Esophageal Squamous Cell Carcinoma Population

The effects of autophagy and apoptosis in the prognostic assessment and treatment of Esophageal squamous cell carcinoma (ESCC) remain to be elucidated. Here, we conducted a retrospective study on the histopathology of ESCC, investigated the expression of Beclin-1 and Bcl-2 proteins (both autophagy- and apoptosis-related) in esophageal cancer tissue, and analyzed the significance of these proteins for the prognosis of ESCC. In the present study, the expression level of Beclin-1 in ESCC was significantly lower than that in adjacent tissues (p < 0.01), whereas the expression level of Bcl-2 showed the opposite pattern (p < 0.01). Furthermore, low expression of Beclin-1 was associated with more advanced ESCC stages and lymph node metastasis. However, high expression of Bcl-2 was associated with more advanced ESCC stages, deeper tumor invasion, and lymph node metastasis. Moreover, the relationship between Bcl-2 expression and OS was not significant (p > 0.05), whereas Beclin-1 expression was significantly associated with OS (p < 0.05). Subgroup analysis showed that Beclin-1 expression was significantly associated with OS in the high-Bcl-2-expression group but not in the low-Bcl-2-expression group. Importantly, Beclin-1 upregulation or downregulation significantly upregulated or downregulated invasion, respectively, in EC9706 cells in combination with high expression but not low expression of Bcl-2. These findings reveal that differences in autophagy and apoptotic states and their activities may promote malignant tumor differentiation, which could lead to a more aggressive esophageal squamous cell phenotype and a worse survival prognosis. Here, Beclin-1 was shown to be a promising prognostic biomarker and therapeutic target for patients with ESCC in the high-Bcl-2-expression population.

Microtubule disrupting agent-mediated inhibition of cancer cell growth is associated with blockade of autophagic flux and simultaneous induction of apoptosis

Objectives

Given that autophagy inhibition is a feasible way to enhance sensitivity of cancer cells towards chemotherapeutic agents, identifying potent autophagy inhibitor has obvious clinical relevance. Here, we investigated ability of TN‐16, a microtubule disrupting agent, on modulation of autophagic flux and its significance in promoting in vitro and in vivo cancer cell death.

Materials and methods

The effect of TN‐16 on cancer cell proliferation, cell division, autophagic process and apoptotic signalling was assessed by various biochemical (Western blot and SRB assay), morphological (TEM, SEM, confocal microscopy) and flowcytometric assays. In vivo anti‐tumour efficacy of TN‐16 was investigated in syngeneic mouse model of breast cancer.

Results

TN‐16 inhibited cancer cell proliferation by impairing late‐stage autophagy and induction of apoptosis. Inhibition of autophagic flux was demonstrated by accumulation of autophagy‐specific substrate p62 and lack of additional LC3‐II turnover in the presence of lysosomotropic agent. The effect was validated by confocal micrographs showing diminished autophagosome‐lysosome fusion. Further studies revealed that TN‐16–mediated inhibition of autophagic flux promotes apoptotic cell death. Consistent with in vitro data, results of our in vivo study revealed that TN‐16–mediated tumour growth suppression is associated with blockade of autophagic flux and enhanced apoptosis.

Conclusions

Our data signify that TN‐16 is a potent autophagy flux inhibitor and might be suitable for (pre‐) clinical use as standard inhibitor of autophagy with anti‐cancer activity.