Diosgenin Exerts Antitumor Activity via Downregulation of Skp2 in Breast Cancer Cells

SKping cell cycle regulation: role of ubiquitin ligase SKP2 in hematological malignancies

SKP2 (S-phase kinase-associated protein 2) is a member of the F-box family of substrate-recognition subunits in the SCF ubiquitin-protein ligase complexes. It is associated with ubiquitin-mediated degradation in the mammalian cell cycle components and other target proteins involved in cell cycle progression, signal transduction, and transcription. Being an oncogene in solid tumors and hematological malignancies, it is frequently associated with drug resistance and poor disease outcomes. In the current review, we discussed the novel role of SKP2 in different hematological malignancies. Further, we performed a limited in-silico analysis to establish the involvement of SKP2 in a few publicly available cancer datasets. Interestingly, our study identified Skp2 expression to be altered in a cancer-specific manner. While it was found to be overexpressed in several cancer types, few cancer showed a down-regulation in SKP2. Our review provides evidence for developing novel SKP2 inhibitors in hematological malignancies. We also investigated the effect of SKP2 status on survival and disease progression. In addition, the role of miRNA and its associated families in regulating Skp2 expression was explored. Subsequently, we predicted common miRNAs against Skp2 genes by using miRNA-predication tools. Finally, we discussed current approaches and future prospective approaches to target the Skp2 gene by using different drugs and miRNA-based therapeutics applications in translational research.

Diosgenyl glucosamine conjugates increase pro-apoptotic and selective activities in cancer cell lines

BACKGROUND INFORMATION

Antiproliferative and apoptotic activities have been attributed to the phytosteroid diosgenin ((25R)-spirost-5-en-3β-ol; 1). It is known that combining glucose with two rhamnoses (the chacotrioside framework) linked to diosgenin increases its apoptotic activity. However, the effects of diosgenin glucosamine glycosides on different cancer cell types and cell death have not been entirely explored.

RESULTS

This study reports the antiproliferative, cytotoxic, and apoptotic activities of diosgenin and its glycosylated derivative ((25R)-spirost-5-en-3β-yl β-D-glucopyranoside; 2). It also explores the effects of two diosgenin glucosamine derivates, diosgenin 2-acetamido-2-deoxy-β-D-glucopyranoside (3), and diosgenin 2-amino-2-deoxy-β-D-glucopyranoside hydrochloride (4), on different cancer cell lines. We found that all the compounds affected proliferative activity with minimal toxicity. In addition, all cancer cell lines showed morphological and biochemical characteristics corresponding to an apoptotic process. Apoptotic cell death was higher in all cell lines treated with compounds 2, 3 and 4 than in those treated with diosgenin. Moreover, compounds 3 and 4 induced apoptosis better than compounds 1 and 2. These results suggest that combining glucosamine with modified glucosamine attached to diosgenin has a greater apoptotic effect than diosgenin or its glycosylated derivative (compound 2). Furthermore, diosgenin and the abovementioned glycosides had a selective effect on tumour cells since the proliferative capacity of human lymphocytes, keratinocytes (HaCaT) and epithelial cells (CCD841) was not significantly affected.

CONCLUSIONS

Altogether, these results demonstrate that diosgenin glucosamine compounds exert an antiproliferative effect on cancer cell lines and induce apoptotic effects more efficiently than diosgenin alone without affecting non-tumour cells.

SIGNIFICANCE

This study evidences the pro-apoptotic and selective activities of diosgenyl glucosamine compounds in cancer cell lines.

Thioridazine reverses trastuzumab resistance in gastric cancer by inhibiting S-phase kinase associated protein 2-mediated aerobic glycolysis

BACKGROUND

Trastuzumab constitutes the fundamental component of initial therapy for patients with advanced human epidermal growth factor receptor 2 (HER-2)-positive gastric cancer (GC). However, the efficacy of this treatment is hindered by substantial challenges associated with both primary and acquired drug resistance. While S-phase kinase associated protein 2 (Skp2) overexpression has been implicated in the malignant progression of GC, its role in regulating trastuzumab resistance in this context remains uncertain. Despite the numerous studies investigating Skp2 inhibitors among small molecule compounds and natural products, there has been a lack of successful commercialization of drugs specifically targeting Skp2.

AIM

To discover a Skp2 blocker among currently available medications and develop a therapeutic strategy for HER2-positive GC patients who have experienced progression following trastuzumab-based treatment.

METHODS

Skp2 exogenous overexpression plasmids and small interfering RNA vectors were utilized to investigate the correlation between Skp2 expression and trastuzumab resistance in GC cells. Q-PCR, western blot, and immunohistochemical analyses were conducted to evaluate the regulatory effect of thioridazine on Skp2 expression. A cell counting kit-8 assay, flow cytometry, a amplex red glucose/glucose oxidase assay kit, and a lactate assay kit were utilized to measure the proliferation, apoptosis, and glycolytic activity of GC cells in vitro. A xenograft model established with human GC in nude mice was used to assess thioridazine's effectiveness in vivo.

RESULTS

The expression of Skp2 exhibited a negative correlation with the sensitivity of HER2-positive GC cells to trastuzumab. Thioridazine demonstrated the ability to directly bind to Skp2, resulting in a reduction in Skp2 expression at both the transcriptional and translational levels. Moreover, thioridazine effectively inhibited cell proliferation, exhibited antiapoptotic properties, and decreased the glucose uptake rate and lactate production by suppressing Skp2/protein kinase B/mammalian target of rapamycin/glucose transporter type 1 signaling pathways. The combination of thioridazine with either trastuzumab or lapatinib exhibited a more pronounced anticancer effect in vivo, surpassing the efficacy of either monotherapy.

CONCLUSION

Thioridazine demonstrates promising outcomes in preclinical GC models and offers a novel therapeutic approach for addressing trastuzumab resistance, particularly when used in conjunction with lapatinib. This compound has potential benefits for patients with Skp2-proficient tumors.

Anticancer Activity of Methyl Protodioscin against Prostate Cancer by Modulation of Cholesterol-Associated MAPK Signaling Pathway <i>via</i> FOXO1 Induction

Methyl protodioscin (MPD), a furostanol saponin found in the rhizomes of Dioscoreaceae, has lipid-lowering and broad anticancer properties. However, the efficacy of MPD in treating prostate cancer remains unexplored. Therefore, the present study aimed to evaluate the anticancer activity and action mechanism of MPD in prostate cancer. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), wound healing, transwell, and flow cytometer assays revealed that MPD suppressed proliferation, migration, cell cycle, and invasion and induced apoptosis of DU145 cells. Mechanistically, MPD decreased cholesterol concentration in the cholesterol oxidase, peroxidase and 4-aminoantipyrine phenol (COD-PAP) assay, disrupting the lipid rafts as detected using immunofluorescence and immunoblot analyses after sucrose density gradient centrifugation. Further, it reduced the associated mitogen-activated protein kinase (MAPK) signaling pathway protein P-extracellular regulated protein kinase (ERK), detected using immunoblot analysis. Forkhead box O (FOXO)1, a tumor suppressor and critical factor controlling cholesterol metabolism, was predicted to be a direct target of MPD and induced by MPD. Notably, in vivo studies demonstrated that MPD significantly reduced tumor size, suppressed cholesterol concentration and the MAPK signaling pathway, and induced FOXO1 expression and apoptosis in tumor tissue in a subcutaneous mouse model. These results suggest that MPD displays anti-prostate cancer activity by inducing FOXO1 protein, reducing cholesterol concentration, and disrupting lipid rafts. Consequently, the reduced MAPK signaling pathway suppresses proliferation, migration, invasion, and cell cycle and induces apoptosis of prostate cancer cells.

Anticancer Activity of Diosgenin and Its Molecular Mechanism

Diosgenin, a steroidal sapogenin, obtained from Trigonella foenum-graecum, Dioscorea, and Rhizoma polgonati, has shown high potential and interest in the treatment of various cancers such as oral squamous cell carcinoma, laryngeal cancer, esophageal cancer, liver cancer, gastric cancer, lung cancer, cervical cancer, prostate cancer, glioma, and leukemia. This article aims to provide an overview of the in vivo, in vitro, and clinical studies reporting the diosgenin's anticancer effects. Preclinical studies have shown promising effects of diosgenin on inhibiting tumor cell proliferation and growth, promoting apoptosis, inducing differentiation and autophagy, inhibiting tumor cell metastasis and invasion, blocking cell cycle, regulating immunity and improving gut microbiome. Clinical investigations have revealed clinical dosage and safety property of diosgenin. Furthermore, in order to improve the biological activity and bioavailability of diosgenin, this review focuses on the development of diosgenin nano drug carriers, combined drugs and the diosgenin derivatives. However, further designed trials are needed to unravel the diosgenin's deficiencies in clinical application.

Small-molecule compounds inhibiting S-phase kinase-associated protein 2: A review

S-phase kinase-associated protein 2 (Skp2) is a substrate-specific adaptor in Skp1-CUL1-ROC1-F-box E3 ubiquitin ligases and widely regarded as an oncogene. Therefore, Skp2 has remained as an active anticancer research topic since its discovery. Accordingly, the structure of Skp2 has been solved and numerous Skp2 inhibiting compounds have been identified. In this review, we would describe the structural features of Skp2, introduce the ubiquitination function of SCF^Skp2, and summarize the diverse natural and synthetic Skp2 inhibiting compounds reported to date. The IC₅₀ data of the Skp2 inhibitors or inhibiting compounds in various kinds of tumors at cellular levels implied that the cancer type, stage and pathological mechanisms should be taken into consideration when selecting Skp2-inhibiting compound for cancer treatment.

Comparative study of steroidal sapogenins content in leaves of five Agave species

BACKGROUND

Agaves are mainly used to produce alcoholic beverages such as tequila, mezcal and bacanora. However, the leaves constitute more than 50% of the plant and are not used in the production process, so they are considered waste. This plant material can be used as a source of bioactive compounds such as terpenes, flavonoids and saponins. Therefore, the objective of this study was to characterize the aglycone type of saponins and to quantify three steroidal sapogenins in leaves of five Agave species collected in different regions of Guerrero and Oaxaca, Mexico.

RESULTS

Analysis by gas chromatography-flame ionization detection of the hydrolyzed methanolic extracts showed that diosgenin and tigogenin were the most abundant sapogenins identified in the five Agave species. Differences in the content of these sapogenins were found in the same species collected in different localities. The leaves of Agave americana var. oaxacensis L. (Oaxaca) had the highest diosgenin-derived saponin content, while the leaves of A. angustifolia Haw. (Guerrero) had the highest tigogenin-derived saponin content. Only in A. cupreata was sarsasapogenin identified, all three sapogenins occurring in the leaves of this species. For the first time, information is provided on the aglycones of the saponins produced in A. potatorum Zucc. and A. karwinskii Zucc.

CONCLUSION

This study made it possible to compare the content of diosgenin and tigogenin-derived saponins in leaves of Agave species from Guerrero and Oaxaca. This information will be useful for better utilization of this plant material and add value to the process of mezcal elaboration. © 2022 Society of Chemical Industry.

Exploring the anticancer activities of novel bioactive compounds derived from endophytic fungi: mechanisms of action, current challenges and future perspectives

Cancer is the second leading cause of death all around the world. The natural compounds derived from the endophytic flora of fungi are possible solutions to cancer treatment because they are safe for health, cost-effective, biocompatible and have fewer toxicity issues. The active ingredients in endophytic fungi that are responsible for anti-cancer activities are alkaloids, terpenoids, glycosides, saponin, peptides, steroids, phenols, quinones, and flavonoids. This review highlights the anti-cancer activities of entophytic fungus against human papillary thyroid carcinoma (IHH4), human pancreatic (PANC-1), ovarian (OVCAR-3), hepatic (HepG2), lung (A-549), human lymphoma (U937), human skin carcinoma (A431), breast (MCF-7), and Kaposi's sarcoma. The emerging evidence suggested that bioactive compounds isolated from endophytic fungi showed their anti-cancer activities by revealing the disturbance of the microtubule network caused by increased levels of Bax and Bcl-2 proteins that triggers cell cycle arrest at the G2-M phase, by inhibiting the DNA replication via binding with topoisomerase II, by regulating the activity of extracellular signal-regulated kinase and NF-kB, by evaluating the levels of p21, p27, and cyclins B/D1/E that led to cell death by apoptosis and cell cycle arrest. This review will assist readers in better comprehending bioactive chemicals and the beneficial interaction between the fungal endophytes and medicinal plants.

Role of Plant-Derived Active Constituents in Cancer Treatment and Their Mechanisms of Action

Despite significant technological advancements in conventional therapies, cancer remains one of the main causes of death worldwide. Although substantial progress has been made in the control and treatment of cancer, several limitations still exist, and there is scope for further advancements. Several adverse effects are associated with modern chemotherapy that hinder cancer treatment and lead to other critical disorders. Since ancient times, plant-based medicines have been employed in clinical practice and have yielded good results with few side effects. The modern research system and advanced screening techniques for plants’ bioactive constituents have enabled phytochemical discovery for the prevention and treatment of challenging diseases such as cancer. Phytochemicals such as vincristine, vinblastine, paclitaxel, curcumin, colchicine, and lycopene have shown promising anticancer effects. Discovery of more plant-derived bioactive compounds should be encouraged via the exploitation of advanced and innovative research techniques, to prevent and treat advanced-stage cancers without causing significant adverse effects. This review highlights numerous plant-derived bioactive molecules that have shown potential as anticancer agents and their probable mechanisms of action and provides an overview of in vitro, in vivo and clinical trial studies on anticancer phytochemicals.

Anti-Allergic Diarrhea Effect of Diosgenin Occurs via Improving Gut Dysbiosis in a Murine Model of Food Allergy

Although the anti-allergic and prebiotic activities of diosgenin have been reported, the influence of diosgenin on intestinal immune and epithelial cells remains unclear. As the gut microbiota plays an important role in allergic disorders, this study aimed to investigate whether the anti-allergic diarrhea effect of diosgenin occurs via improving gut dysbiosis. In a murine food allergy model, the density of fecal bacterial growth on de Man, Rogossa and Sharpe (MRS) plates was diminished, and growth on reinforced clostridial medium (RCM) and lysogeny broth (LB) agar plates was elevated. However, the oral administration of diosgenin reduced the density of fecal bacteria and ameliorated diarrhea severity. Concordantly, reshaped diversity and an abundance of fecal microbes were observed in some of the diosgenin-treated mice, which showed a milder severity of diarrhea. The relevant fecal strains from the diosgenin-treated mice were defined and cultured with Caco-2 cells and allergen-primed mesenteric lymph node (MLN) cells. These strains exhibited protective effects against the cytokine/chemokine network and allergen-induced T-cell responses to varying degrees. By contrast, diosgenin limitedly regulated cytokine production and even reduced cell viability. Taken together, these findings show that diosgenin per se could not directly modulate the functionality of intestinal epithelial cells and immune cells, and its anti-allergic effect is most likely exerted via improving gut dysbiosis.

Imatinib and GNF-5 Exhibit an Inhibitory Effect on Growth of Hepatocellar Carcinoma Cells by Downregulating S-phase Kinase-associated Protein 2

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and is one of the leading causes of cancer-related deaths worldwide. Imatinib and GNF-5 are breakpoint cluster region-Abelson murine leukemia tyrosine kinase inhibitors which have been approved for the treatment of chronic myeloid leukemia and various solid tumors. However, the effect and underlying mechanisms of imatinib and GNF-5 in HCC remain poorly defined. In this study, we investigated the anticancer activity and underlying mechanisms of imatinib and GNF-5 in HepG2 human hepatocarcinoma cells. Cell proliferation and anchorage-independent colony formation assays were done to evaluate the effects of imatinib and GNF-5 on the growth of HepG2 cells. The cell cycle was assessed by flow cytometry and verified by immunoblot analysis. Gene overexpression and knockdown assays were conducted to evaluate the function of S-phase kinase-associated protein 2 (Skp2). Imatinib and GNF-5 significantly inhibited the growth of HepG2 cells. Imatinib and GNF-5 induced G0/G1 phase cell cycle arrest by downregulating Skp2 and upregulating p27 and p21. Overexpression of Skp2 reduced the effect of imatinib and GNF-5 on HepG2 cells. Knockdown of Skp2 suppressed the proliferation and induced G0/G1 phase arrest. Furthermore, knockdown of Skp2 enhanced the effect of imatinib and GNF-5 on growth of HepG2 cells. In conclusion, imatinib and GNF-5 effectively suppress HepG2 cell growth by inhibiting Skp2 expression. Skp2 promotes the cell proliferation and reverse G0/G1 phase cell cycle arrest and it represents a potential therapeutic target for HCC treatment.