Galangin sensitizes TRAIL-induced apoptosis through down-regulation of anti-apoptotic proteins in renal carcinoma Caki cells

Selected Flavonols Targeting Cell Death Pathways in Cancer Therapy: The Latest Achievements in Research on Apoptosis, Autophagy, Necroptosis, Pyroptosis, Ferroptosis, and Cuproptosis

The complex and multi-stage processes of carcinogenesis are accompanied by a number of phenomena related to the potential involvement of various chemopreventive factors, which include, among others, compounds of natural origin such as flavonols. The use of flavonols is not only promising but also a recognized strategy for cancer treatment. The chemopreventive impact of flavonols on cancer arises from their ability to act as antioxidants, impede proliferation, promote cell death, inhibit angiogenesis, and regulate the immune system through involvement in diverse forms of cellular death. So far, the molecular mechanisms underlying the regulation of apoptosis, autophagy, necroptosis, pyroptosis, ferroptosis, and cuproptosis occurring with the participation of flavonols have remained incompletely elucidated, and the results of the studies carried out so far are ambiguous. For this reason, one of the therapeutic goals is to initiate the death of altered cells through the use of quercetin, kaempferol, myricetin, isorhamnetin, galangin, fisetin, and morin. This article offers an extensive overview of recent research on these compounds, focusing particularly on their role in combating cancer and elucidating the molecular mechanisms governing apoptosis, autophagy, necroptosis, pyroptosis, ferroptosis, and cuproptosis. Assessment of the mechanisms underlying the anticancer effects of compounds in therapy targeting various types of cell death pathways may prove useful in developing new therapeutic regimens and counteracting resistance to previously used treatments.

TRAIL-Sensitizing Effects of Flavonoids in Cancer

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) represents a promising anticancer agent, as it selectively induces apoptosis in transformed cells without altering the cellular machinery of healthy cells. Unfortunately, the presence of TRAIL resistance mechanisms in a variety of cancer types represents a major hurdle, thus limiting the use of TRAIL as a single agent. Accumulating studies have shown that TRAIL-mediated apoptosis can be facilitated in resistant tumors by combined treatment with antitumor agents, ranging from synthetic molecules to natural products. Among the latter, flavonoids, the most prevalent polyphenols in plants, have shown remarkable competence in improving TRAIL-driven apoptosis in resistant cell lines as well as tumor-bearing mice with minimal side effects. Here, we summarize the molecular mechanisms, such as the upregulation of death receptor (DR)4 and DR5 and downregulation of key anti-apoptotic proteins [e.g., cellular FLICE-inhibitory protein (c-FLIP), X-linked inhibitor of apoptosis protein (XIAP), survivin], underlying the TRAIL-sensitizing properties of different classes of flavonoids (e.g., flavones, flavonols, isoflavones, chalcones, prenylflavonoids). Finally, we discuss limitations, mainly related to bioavailability issues, and future perspectives regarding the clinical use of flavonoids as adjuvant agents in TRAIL-based therapies.

Pharmacological activities and therapeutic potential of galangin, a promising natural flavone, in age-related diseases

BACKGROUND

The extension of average life expectancy and the aggravation of population aging have become the inevitable trend of human development. In an aging society, various problems related to medical care for the elderly have become increasingly prominent. However, most of the age-related diseases have the characteristics of multiple diseases at the same time, prone to complications, and atypical clinical manifestations, which bring great difficulties to its treatment. Galangin (3,5,7-trihydroxyflavone) is a natural active compound extracted from the root of Alpinia officinarum Hance (Zingiberaceae). Recently, many studies have shown that galangin has potential advantages in the treatment of neurodegenerative diseases and cardiovascular and cerebrovascular diseases, which are common in the elderly. In addition, it also showed that galangin had prospective activities in the treatment of tumor, diabetes, liver injury, asthma and arthritis.

PURPOSE

This review aims to systematically summarize and discuss the effects and the underlying mechanism of galangin in the treatment of age-related diseases.

METHODS

We searched PubMed, SciFinder, Web of Science and CNKI literature database resources, combined with the keywords "galangin", "neurodegenerative disease", "tumor", "diabetes", "pharmacological activity", "drug combination", "pharmacokinetics", "drug delivery system" and "safety", and comprehensively reviewed the pharmacological activities and mechanism of galangin in treating age-related diseases.

RESULTS

According to the previous studies on galangin, the anti-neurodegenerative activity, cardiovascular and cerebrovascular protective activity, anti-tumor activity, anti-diabetes activity, anti-arthritis activity, hepatoprotective activity and antiasthmatic activity of galangin were discussed, and the related mechanisms were classified and summarized in detail. In addition, the drug combination, pharmacokinetics, drug delivery system and safety of galangin were furtherly discussed.

CONCLUSIONS

This review will provide reference for galangin in the treatment of age-related diseases. Meanwhile, further experimental research and long-term clinical trials are needed to determine the therapeutic safety and efficacy of galangin.

Analysis of Galangin and Its In Vitro/In Vivo Metabolites via Ultra-High-Performance Liquid Chromatography/Quadrupole Time-of-Flight Mass Spectrometry

Galangin, a naturally available flavonoid, induces a variety of pharmacological activities and biological effects via several mechanisms. However, in vivo metabolism of galangin has not been fully explored, which means knowledge of its pharmacodynamics and application potential is limited. The objective of this study was to establish an ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry method for the rapid profiling and identification of galangin metabolites in vitro and in vivo using unique online information-dependent acquisition with multiple mass defect filtering combined with dynamic background subtraction in positive ion mode. A total of 27 metabolites were detected and characterized, among which eight metabolites in liver microsomes and four metabolites in intestinal microflora were characterized, and 27 metabolites from rat plasma, bile, urine, feces, and a number of different tissue samples were characterized. Thirteen major metabolic pathways including hydrogenation, hydroxylation, glycosylation, methylation, acetylation, glucuronidation, and sulfation were observed to be attributable to the biotransformation of the metabolites. This study provides evidence for the presence of in vitro and in vivo metabolites and the pharmacokinetic mechanism of galangin. Moreover, the study promotes the further development and utilization of galangin and the plant from which it is derived, Alpinia officinarum Hance.

Modern aspects of the use of natural polyphenols in tumor prevention and therapy

Polyphenols are secondary plant metabolites or organic compounds synthesized by them. In other words, these are molecules that are found in plants. Due to the wide variety of polyphenols and the plants in which they are found, these compounds are divided according to the source of origin, the function of the polyphenols, and their chemical structure; where the main ones are flavonoids. All the beneficial properties of polyphenols have not yet been studied, since this group of substances is very extensive and diverse. However, most polyphenols are known to be powerful antioxidants and have anti-inflammatory effects. Polyphenols help fight cell damage caused by free radicals and immune system components. In particular, polyphenols are credited with a preventive effect that helps protect the body from certain forms of cancer. The onset and progression of tumors may be related directly to oxidative stress, or inflammation. These processes can increase the amount of DNA damage and lead to loss of control over cell division. A number of studies have shown that oxidative stress uncontrolled by antioxidants or an uncontrolled and prolonged inflammatory process increases the risk of developing sarcoma, melanoma, and breast, lung, liver, and prostate cancer. Therefore, a more in-depth study of the effect of polyphenolic compounds on certain signaling pathways that determine the complex cascade of oncogenesis is a promising direction in the search for new methods for the prevention and treatment of tumors.

Coding recognition of the dose-effect interdependence of small biomolecules encrypted on paired chromatographic-based microassay arrays

The discovery of small biomolecules has suffered from the lack of a comprehensive framework to express the intrinsic correlation between bioactivity and the contribution from small molecules in complex samples with molecular and bioactivity diversity. Here, by mapping a sample’s 2D-HPTLC fingerprint to microplates, paired chromatographic-based microassay arrays are created, which can be used as quasi-chips to characterize multiple attributes of chromatographic components; as the array differential expression of the bioactivity and molecular attributes of irregular chromatographic spots for dose–effect interdependent encoding; and also as the automatic-collimated array mosaics of the multi-attributes of each component itself encrypted by its chromatographic fingerprint. Based on this homologous framework, we propose a correlating recognition strategy for small biomolecules through their self-consistent chromatographic behavior characteristics. In the approach, the small biomolecule recognition in diverse compounds is transformed into a constraint satisfaction problem, which is addressed through examining the dose–effect interdependence of the homologous 2D code pairs by an array matching algorithm, instead of preparing diverse compound monomers of complex test samples for identification item-by-item. Furthermore, considering the dose–effect interdependent 2D code pairs as links and the digital-specific quasimolecular ions as nodes, an extendable self-consistent framework that correlates mammalian cell phenotypic and target-based bioassays with small biomolecules is established. Therefore, the small molecule contributions and the correlations of bioactivities, as well as their pathways, can be comprehensively revealed, so as to improve the reliability and efficiency of screening. This strategy was successfully applied to galangal, and demonstrated the high-throughput digital preliminary screening of small biomolecules in a natural product.

Galangin: A metabolite that suppresses anti-neoplastic activities through modulation of oncogenic targets

With the dramatic increase in cancer incidence all over the world in the last decades, studies on identifying novel efficient anti-cancer agents have been intensified. Historically, natural products have represented one of the most important sources of new lead compounds with a wide range of biological activities. In this article, the multifaceted anti-cancer action of propolis-derived flavonoid, galangin, is presented, discussing its antioxidant, anti-inflammatory, antiproliferative, pro-apoptotic, anti-angiogenic, and anti-metastatic effects in various cancer cells. In addition, co-effects with standard chemotherapeutic drugs as well as other natural compounds are also under discussion, besides highlighting modern nanotechnological advancements for overcoming the low bioavailability issue characteristic of galangin. Although further studies are needed for confirming the anti-cancer potential of galangin in vivo malignant systems, exploring this natural compound might open new perspectives in molecular oncology.

A comprehensive review on chemotherapeutic potential of galangin

Galangin, a non-toxic phytochemical is known to possess several therapeutic applications. Mounting evidences have demonstrated that galangin a naturally available flavonoid exerts anticancer effects via several mechanisms. The phytocompound induces apoptosis and renders antiangiogenic property. Additionally, galangin has demonstrated significate results in combating various cancer types when administered in combination with other phytocompounds or with gold nanoparticles (GNPs). The present article is a critical review of galangin for its treatment on different types of cancer and its usability as an alternative cancer therapeutics.

Alternol Sensitizes Renal Carcinoma Cells to TRAIL-Induced Apoptosis

Purpose: Tumor necrosis factor–related apoptosis-inducing ligand (TRAIL), a member of the TNF family, can selectively induce cancer cell death while sparing normal cells. However, the application of TRAIL-based antitumor therapies has been hindered due to drug resistance. Alternol is a new compound isolated from microbial fermentation that possesses antitumor activity in different tumors. In our research, we discovered that alternol can sensitize TRAIL-induced apoptosis in renal carcinoma cells (RCCs).

Materials and Methods: Cytotoxic activity was measured by MTT assay. Apoptosis was probed using the PI/annexin V method. Real-time PCR and western blot were used to test the levels of mRNA and protein, respectively. Luciferase assay was used to investigate whether CHOP regulated the expression of death receptor (DR) 5 through transcription. A xenogeneic tumor transplantation model was used to evaluate the anticancer effects of alternol/TRAIL in vivo.

Results: When the mechanisms were investigated, we discovered that alternol increased DR5 expression. DR5 knockdown by siRNA eliminated the enhanced effect of alternol on TRAIL-mediated apoptosis. Alternol reduced the expression of antiapoptotic proteins and increased the levels of proapoptotic proteins. Moreover, alternol increased the level of CHOP, which is necessary for the enhancing effect of alternol on TRAIL-induced apoptosis, given that downregulation of CHOP abrogated the synergistic effect. DR5 upregulation induced by alternol required the production of reactive oxygen species (ROS). Removing ROS inhibited the induction of DR5 and blocked the antiapoptotic proteins induced by alternol.

Conclusion: Taken together, our research suggested that alternol increased TRAIL-mediated apoptosis via inhibiting antiapoptotic proteins and upregulating DR5 levels via ROS generation and the CHOP pathway.

Angelicin-A Furocoumarin Compound With Vast Biological Potential

Angelicin, a member of the furocoumarin group, is related to psoralen which is well known for its effectiveness in phototherapy. The furocoumarins as a group have been studied since the 1950s but only recently has angelicin begun to come into its own as the subject of several biological studies. Angelicin has demonstrated anti-cancer properties against multiple cell lines, exerting effects via both the intrinsic and extrinsic apoptotic pathways, and also demonstrated an ability to inhibit tubulin polymerization to a higher degree than psoralen. Besides that, angelicin too demonstrated anti-inflammatory activity in inflammatory-related respiratory and neurodegenerative ailments via the activation of NF-κB pathway. Angelicin also showed pro-osteogenesis and pro-chondrogenic effects on osteoblasts and pre-chondrocytes respectively. The elevated expression of pro-osteogenic and chondrogenic markers and activation of TGF-β/BMP, Wnt/β-catenin pathway confirms the positive effect of angelicin bone remodeling. Angelicin also increased the expression of estrogen receptor alpha (ERα) in osteogenesis. Other bioactivities, such as anti-viral and erythroid differentiating properties of angelicin, were also reported by several researchers with the latter even displaying an even greater aptitude as compared to the commonly prescribed drug, hydroxyurea, which is currently on the market. Apart from that, recently, a new application for angelicin against periodontitis had been studied, where reduction of bone loss was indirectly caused by its anti-microbial properties. All in all, angelicin appears to be a promising compound for further studies especially on its mechanism and application in therapies for a multitude of common and debilitating ailments such as sickle cell anaemia, osteoporosis, cancer, and neurodegeneration. Future research on the drug delivery of angelicin in cancer, inflammation and erythroid differentiation models would aid in improving the bioproperties of angelicin and efficacy of delivery to the targeted site. More in-depth studies of angelicin on bone remodeling, the pro-osteogenic effect of angelicin in various bone disease models and the anti-viral implications of angelicin in periodontitis should be researched. Finally, studies on the binding of angelicin toward regulatory genes, transcription factors, and receptors can be done through experimental research supplemented with molecular docking and molecular dynamics simulation.

CRISPR-mediated upregulation of DR5 and downregulation of cFLIP synergistically sensitize HeLa cells to TRAIL-mediated apoptosis

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has received attention as an anticancer therapy because it mediates apoptosis of several cancer cell types but not normal human cell types. In this study, we implemented genome editing techniques to upregulate DR5 and downregulate cFLIP in HeLa cells to stimulate TRAIL-induced apoptosis. We designed and validated sgRNAs to enrich the endogenous level of DR5 by dead Cas9 (dCas9). Similarly, we designed two sgRNAs to disrupt the cFLIP gene by CRISPR/Cas9. We analyzed the effect of TRAIL on tumor cells by co-transfecting HeLa cells with the best combinations of sgRNAs regulating DR5 and cFLIP genes. TRAIL-induced apoptosis in HeLa cells was evaluated by the γH2AX foci formation assay to check for double-strand break and propidium iodide and Annexin V staining to quantify apoptotic cells. Viable cells were identified by CCK-8 assay, and cleaved-PARP level was evaluated by Western blot. This is the first study to demonstrate that genome editing techniques can be used as an effective combinatorial treatment strategy to induce apoptosis of cancer cells. In particular, enhancement of DR5 expression and inhibition of cFLIP expression by genome editing had a synergistic effect of inhibiting proliferation and inducing apoptosis in TRAIL-resistant HeLa cells. These results suggest that combinatorial treatment strategies mediated by the CRISPR/Cas9 system may be effective for design of other human TRAIL-resistant cell types.

Garcinol Enhances TRAIL-Induced Apoptotic Cell Death through Up-Regulation of DR5 and Down-Regulation of c-FLIP Expression

Garcinol is a polyisoprenylated benzophenone derived from the Garcinia indica fruit that possess potential therapeutic effects such as inhibition of inflammation and tumor expansion. Here, we investigated whether garcinol induces TRAIL sensitization in renal carcinoma cells. Single treatment with garcinol or TRAIL did not effect on apoptosis. However, combined treatment with garcinol plus TRAIL significantly induced apoptosis in renal carcinoma (Caki, ACHN and A498), lung carcinoma (A549), and hepatoma (SK-Hep1) cells. In contrast, garcinol plus TRAIL did not alter cell viability in normal cells. Garcinol plus TRAIL induced up-regulation of DR5 and down-regulation of c-FLIP expression at post-translational levels. Furthermore, knock-down of DR5 by siRNA and ectopic expression of c-FLIP blocked apoptotic cell death induced by garcinol plus TRAIL. Overall, our study provides evidence that garcinol can be exploited as a potential TRAIL sensitizer.

Flavonoids in Kidney Health and Disease

This review summarizes the latest advances in knowledge on the effects of flavonoids on renal function in health and disease. Flavonoids have antihypertensive, antidiabetic, and antiinflammatory effects, among other therapeutic activities. Many of them also exert renoprotective actions that may be of interest in diseases such as glomerulonephritis, diabetic nephropathy, and chemically-induced kidney insufficiency. They affect several renal factors that promote diuresis and natriuresis, which may contribute to their well-known antihypertensive effect. Flavonoids prevent or attenuate the renal injury associated with arterial hypertension, both by decreasing blood pressure and by acting directly on the renal parenchyma. These outcomes derive from their interference with multiple signaling pathways known to produce renal injury and are independent of their blood pressure-lowering effects. Oral administration of flavonoids prevents or ameliorates adverse effects on the kidney of elevated fructose consumption, high fat diet, and types I and 2 diabetes. These compounds attenuate the hyperglycemia-disrupted renal endothelial barrier function, urinary microalbumin excretion, and glomerular hyperfiltration that results from a reduction of podocyte injury, a determinant factor for albuminuria in diabetic nephropathy. Several flavonoids have shown renal protective effects against many nephrotoxic agents that frequently cause acute kidney injury (AKI) or chronic kidney disease (CKD), such as LPS, gentamycin, alcohol, nicotine, lead or cadmium. Flavonoids also improve cisplatin- or methotrexate-induced renal damage, demonstrating important actions in chemotherapy, anticancer and renoprotective effects. A beneficial prophylactic effect of flavonoids has been also observed against AKI induced by surgical procedures such as ischemia/reperfusion (I/R) or cardiopulmonary bypass. In several murine models of CKD, impaired kidney function was significantly improved by the administration of flavonoids from different sources, alone or in combination with stem cells. In humans, cocoa flavanols were found to have vasculoprotective effects in patients on hemodialysis. Moreover, flavonoids develop antitumor activity against renal carcinoma cells with no toxic effects on normal cells, suggesting a potential therapeutic role in patients with renal carcinoma.

YM155 sensitizes TRAIL-induced apoptosis through cathepsin S-dependent down-regulation of Mcl-1 and NF-κB-mediated down-regulation of c-FLIP expression in human renal carcinoma Caki cells

YM155, a small-molecule survivin inhibitor, has been reported for its anti-cancer activity in various cancer cells. In this study, we investigated the effect of YM155 to enhance TRAIL-mediated apoptosis in human renal carcinoma cells. We found that YM155 alone had no effect on apoptosis, however, combined treatment with YM155 and TRAIL markedly induced apoptosis in human renal carcinoma cells (Caki, ACHN, and A498), breast cancer cells (MDA-MB231), and glioma cells (U251MG), but not normal cells [mesangial cell (MC) and human skin fibroblast (HSF)]. YM155 induced down-regulation of Mcl-1 expression at the post-translational levels, and the overexpression of Mcl-1 markedly inhibited YM155 plus TRAIL-induced apoptosis. Furthermore, YM155 induced down-regulation of c-FLIP mRNA expression through inhibition of NF-κB transcriptional activity. Ectopic expression of c-FLIP markedly blocked YM155-induced TRAIL sensitization. Taken together, our results suggested that YM155 sensitizes TRAIL-mediated apoptosis via down-regulation of Mcl-1 and c-FLIP expression in renal carcinoma Caki cells.

Galangin inhibits human osteosarcoma cells growth by inducing transforming growth factor-β1-dependent osteogenic differentiation

Osteosarcoma is the most common primary malignancy of the musculoskeletal system, and is associated with excessive proliferation and poor differentiation of osteoblasts. Currently, despite the use of traditional chemotherapy and radiotherapy, no satisfactory and effective agent has been developed to treat the disease. Herein, we found that a flavonoid natural product, galangin, could significantly attenuate human osteosarcoma cells proliferation, without causing obvious cell apoptosis. Moreover, galangin enhanced the expression of osteoblast differentiation markers (collagen type I, alkaline phosphatase, osteocalcin and osteopontin) remarkably and elevated the alkaline phosphatase activity in human osteosarcoma cells. And galangin could also attenuated osteosarcoma growth in vivo. These bioactivities of galangin resulted from its selective activation of the transforming growth factor (TGF)-β1/Smad2/3 signaling pathway, which was demonstrated by pathway blocking experiments. These findings suggested that galangin could be a promising agent to treat osteosarcoma. In addition, targeting TGF-β1 to induce osteogenic differentiation might represent a novel therapeutic strategy to treat osteosarcoma with minimal side effects.

Galangin suppresses human osteosarcoma cells: An exploration of its underlying mechanism

Osteosarcoma is the most common malignant bone tumor that frequently affects adolescents. Osteosarcoma cells tend to proliferate and invade other tissues such as those of the lungs. Currently, neoadjuvant chemotherapy is the primary strategy to prevent tumor progression. However, its adverse effects result in poor long-term outcomes. Previous research has shown that galangin exhibits antitumor properties on several types of cancer cells; however its effect on osteosarcoma cells is yet unknown. The aims of this study were to evaluate the effects of galangin on the proliferation, apoptosis, migration, and invasion of osteosarcoma cells and to explore the underlying mechanisms. We found that the proliferation of MG63 and U20S osteosarcoma cells decreased significantly, while the apoptosis of MG63 cells accelerated significantly after exposure to galangin. In addition, the migration and invasion of MG63 cells were significantly inhibited by galangin. Moreover, phosphoinositide 3-kinase (PI3K) and Aktp-Thr308 expression levels were found to be significantly lower in galangin-treated MG63 cells than in the control cells, and the protein expression levels of their downstream regulators cyclin D1 and matrix metalloproteinase 2/9 were also downregulated in galangin-treated groups, while those of p27Kip1, caspase-3, and caspase-8 were upregulated. These findings suggest that galangin suppresses osteosarcoma cells by inhibiting their proliferation and invasion and accelerating their apoptosis, and the mechanism may be associated with the inhibition of PI3K and its downstream signaling pathway.