Verrucarin A, a protein synthesis inhibitor, induces growth inhibition and apoptosis in breast cancer cell lines MDA-MB-231 and T47D

Decoding Ribosome Heterogeneity: A New Horizon in Cancer Therapy

The traditional perception of ribosomes as uniform molecular machines has been revolutionized by recent discoveries, revealing a complex landscape of ribosomal heterogeneity. Opposing the conventional belief in interchangeable ribosomal entities, emerging studies underscore the existence of specialized ribosomes, each possessing unique compositions and functions. Factors such as cellular and tissue specificity, developmental and physiological states, and external stimuli, including circadian rhythms, significantly influence ribosome compositions. For instance, muscle cells and neurons are characterized by distinct ribosomal protein sets and dynamic behaviors, respectively. Furthermore, alternative forms of ribosomal RNA (rRNAs) and their post-transcriptional modifications add another dimension to this heterogeneity. These variations, orchestrated by spatial, temporal, and conditional factors, enable the manifestation of a broad spectrum of specialized ribosomes, each tailored for potentially distinct functions. Such specialization not only impacts mRNA translation and gene expression but also holds significant implications for broader biological contexts, notably in the realm of cancer research. As the understanding of ribosomal diversity deepens, it also paves the way for exploring novel avenues in cellular function and offers a fresh perspective on the molecular intricacies of translation.

Metabolites of soil microorganisms modulate amyloid β production in Alzheimer's neurons

Microbial flora is investigated to be related with neuropathological conditions in Alzheimer’s disease (AD), and is attracting attention as a drug discovery resource. However, the relevance between the soil microbiota and the pathological condition has not been fully clarified due to the difficulty in isolation culture and the component complexity. In this study, we established a library of secondly metabolites produced in microorganism to investigate the potential effect of microorganisms on the production of amyloid β (Aβ), one of the most representative pathogens of AD. We conducted a library screening to quantify Aβ and neuronal toxicity by using cortical neurons from human induced pluripotent stem cells (iPSCs) of AD patients after adding secondary metabolites. Screening results and following assessment of dose-dependency identified Verrucarin A, produced in Myrothecium spp., showed 80% decrease in Aβ production. Furthermore, addition of Mer-A2026A, produced in Streptomyces pactum, showed increase in Aβ42/40 ratio at the low concentration, and decrease in Aβ production at the higher concentration. As a result, established library and iPSC-based phenotyping assay clarified a direct link between Aβ production and soil microorganisms. These results suggest that Aβ-microorganism interaction may provide insight into the AD pathophysiology with potential therapeutics.

A Drug Repurposing and Protein-Protein Interaction Network Study of Ribosomopathies Using Yeast as a Model System

Ribosomopathies result in various cancers, neurodegenerative and viral diseases, and other pathologies such as Diamond-Blackfan anemia and Shwachman-Diamond syndrome. Their pathophysiology at a proteome and functional level remains to be determined. Protein networks and highly connected hub proteins for ribosome biogenesis in Saccharomyces cerevisiae offer a potential as a model system to inform future therapeutic innovation in ribosomopathies. In this context, we report a ribosome biogenesis protein-protein interaction network in S. cerevisiae, created with 1772 proteins and 22,185 physical interactions connecting them. Moreover, by network decomposition analysis, we determined the linear pathways between the transcription factors and target proteins with a view to drug repurposing. While considering only the paths containing the three C/D box proteins (Nop56, Nop58, and Nop1), the most frequently encountered proteins were Aft1, Htz1, Ssa1, Ssb1, Ssb2, Gcn5, Cka1, Tef1, Nop1, Cdc28, Act1, Krr1, Rpl8B, and Tor1, which were then identified as potential drug targets. For drug repurposing, these candidate proteins were further searched in the DrugBank to find other diseases associated with them, as well as the drugs used to treat these diseases. To support the computational results, an experimental study was conducted using in-house manufactured microfluidic bioreactor platform, while the effect of the drug temsirolimus, Tor1 inhibitor, on yeast cells was investigated by following Nop56 protein expression. In conclusion, these results inform the ways in which ribosomopathies and associated common complex human diseases materialize and how drug repurposing might accelerate therapeutic innovation through bioinformatic studies of yeast.

Review article: Role of satiety hormones in anorexia induction by Trichothecene mycotoxins

The trichothecenes, produced by Fusarium, contaminate animal feed and human food in all stages of production and lead to a large spectrum of adverse effects for animal and human health. An hallmark of trichothecenes toxicity is the onset of emesis followed by anorexia and food intake reduction in different animal species (mink, mice and pig). The modulation of emesis and anorexia can result from a direct action of trichothecenes in the brain or from an indirect action in the gastrointestinal tract. The direct action of trichothecenes involved specific brain areas such as nucleate tractus solitarius in the brainstem and the arcuate nuclei in the hypothalamus. Activation of these areas in the brain leads to the activation of specific neuronal populations containing anorexigenic factors (POMC and CART). The indirect action of trichothecenes in the gastrointestinal tract involved, by enteroendocrine cells, the secretion of several gut hormones such as cholecystokinin (CCK) and peptide YY (PYY) but also glucagon-like peptide 1 (GLP-1), gastric inhibitory peptide (GIP) and 5-hydroxytryptamine (5-HT), which transmitted signals to the brain via the gut-brain axis. This review summarizes current knowledge on the effects of trichothecenes, especially deoxynivalenol, on emesis and anorexia and discusses the mechanisms underlying trichothecenes-induced food reduction.

Trichothecenes: immunomodulatory effects, mechanisms, and anti-cancer potential

Paradoxically, trichothecenes have both immunosuppressive and immunostimulatory effects. The underlying mechanisms have not been fully explored. Early studies show that dose, exposure timing, and the time at which immune function is assessed influence whether trichothecenes act in an immunosuppressive or immunostimulatory fashion. Recent studies suggest that the immunomodulatory function of trichothecenes is also actively shaped by competing cell-survival and death-signaling pathways. Autophagy may also promote trichothecene immunosuppression, although the mechanism may be complicated. Moreover, trichothecenes may generate an "immune evasion" milieu that allows pathogens to escape host and vaccine immune defenses. Some trichothecenes, especially macrocyclic trichothecenes, also potently kill cancer cells. T-2 toxin conjugated with anti-cancer monoclonal antibodies significantly suppresses the growth of thymoma EL-4 cells and colon cancer cells. The type B trichothecene diacetoxyscirpenol specifically inhibits the tumor-promoting factor HIF-1 in cancer cells under hypoxic conditions. Trichothecin markedly inhibits the growth of multiple cancer cells with constitutively activated NF-κB. The type D macrocyclic toxin Verrucarin A is also a promising therapeutic candidate for leukemia, breast cancer, prostate cancer, and pancreatic cancer. The anti-cancer activities of trichothecenes have not been comprehensively summarized. Here, we first summarize the data on the immunomodulatory effects of trichothecenes and discuss recent studies that shed light on the underlying cellular and molecular mechanisms. These mechanisms include autophagy and major signaling pathways and their crosstalk. Second, the anti-cancer potential of trichothecenes and the underlying mechanisms will be discussed. We hope that this review will show how trichothecene bioactivities can be exploited to generate therapies against pathogens and cancer.

Recent progress in fungus-derived bioactive agents for targeting of signaling machinery in cancer cells

It is becoming increasingly understood that tumor cells may have different mutations and dependencies on diverse intracellular signaling cascades for survival or metastatic potential. Overexpression of oncogenes, inactivation of tumor suppressor genes, genetic/epigenetic mutations, genomic instability, and loss of apoptotic cell death are some of the mechanisms that have been widely investigated in molecular oncology. We partition this multicomponent review into the most recent evidence on the anticancer activity of fungal substances obtained from in vitro and xenografted models, and these fungal substances modulate expression of oncogenic and tumor suppressor miRNAs. There are some outstanding questions regarding fungus-derived chemical-induced modulation of intracellular signaling networks in different cancer cell lines and preclinical models. Certain hints have emerged, emphasizing mechanisms via which apoptosis can be restored in TRAIL-resistant cancer cells. Reconceptualization of the knowledge obtained from these emerging areas of research will enable us to potentially identify natural agents with notable anticancer activity and minimal off-target effects. Integration of experimentally verified evidence obtained from cancer cell line gene expression with large-scale functional screening results and pharmacological sensitivity data will be helpful in identification of therapeutics with substantial efficacy. New tools and technologies will further deepen our understanding of the signaling networks that underlie the development of cancer, metastasis, and resistance to different therapeutics at both a personal and systems-wide level.

Verrucarin A alters cell-cycle regulatory proteins and induces apoptosis through reactive oxygen species-dependent p38MAPK activation in the human breast cancer cell line MCF-7

Verrucarin A (VA), an active constituent of pathogenic fungus Myrothecium verrucaria, which has the ability to inhibit the growth of breast cancer cells. However, the mechanism by which VA exerts its inhibitory potential remains elusive. Here, we demonstrated that VA inhibited the growth of MCF-7 breast cancer cells, increased the levels of reactive oxygen species (ROS), and subsequently induced mitochondrial membrane potential (Δψm) loss, leading to the increase of Bax/Bcl-2 ratio, cytochrome c release, caspase activation, PARP degradation, and apoptosis. VA effectively increased the phosphorylation of p38MAPK and diminished the phosphorylation of ERK/Akt. In addition, VA caused cell cycle deregulation through the induction of p21 and p53. Furthermore, ROS scavenger (n-acetyl-L-cysteine) and p38MAPK inhibitor (SB202190) effectively abrogated the VA-induced cell cycle deregulation and apoptosis. Conversely, U0126, an ERK1/2 inhibitor, enhanced the VA-induced apoptotic signals. Taken together, our results suggest that VA-induces apoptosis and cell cycle deregulation in MCF-7 cells through ROS-dependent p38MAPK activation.

Identification of verrucarin a as a potent and selective steroid receptor coactivator-3 small molecule inhibitor

Members of the steroid receptor coactivator (SRC) family are overexpressed in numerous types of cancers. In particular, steroid receptor coactivator 3 (SRC-3) has been recognized as a critical coactivator associated with tumor initiation, progression, recurrence, metastasis, and chemoresistance where it interacts with multiple nuclear receptors and other transcription factors to enhance their transcriptional activities and facilitate cross-talk between pathways that stimulate cancer progression. Because of its central role as an integrator of growth signaling pathways, development of small molecule inhibitors (SMIs) against SRCs have the potential to simultaneously disrupt multiple signal transduction networks and transcription factors involved in tumor progression. Here, high-throughput screening was performed to identify compounds able to inhibit the intrinsic transcriptional activities of the three members of the SRC family. Verrucarin A was identified as a SMI that can selectively promote the degradation of the SRC-3 protein, while affecting SRC-1 and SRC-2 to a lesser extent and having no impact on CARM-1 and p300 protein levels. Verrucarin A was cytotoxic toward multiple types of cancer cells at low nanomolar concentrations, but not toward normal liver cells. Moreover, verrucarin A was able to inhibit expression of the SRC-3 target genes MMP2 and MMP13 and attenuated cancer cell migration. We found that verrucarin A effectively sensitized cancer cells to treatment with other anti-cancer drugs. Binding studies revealed that verrucarin A does not bind directly to SRC-3, suggesting that it inhibits SRC-3 through its interaction with an upstream effector. In conclusion, unlike other SRC SMIs characterized by our laboratory that directly bind to SRCs, verrucarin A is a potent and selective SMI that blocks SRC-3 function through an indirect mechanism.