Inhibition of Specificity Protein 1 Is Involved in Phloretin-Induced Suppression of Prostate Cancer

Recent advances in flavonoid compounds for the treatment of prostate cancer

Prostate cancer is a malignant epithelial tumor of the prostate gland and is the most common malignant tumor of the male genitourinary system. Pharmacological therapies, including chemotherapy and androgen deprivation therapy, play a key role in the treatment of prostate cancer. However, drug resistance and side effects limit the use of these drugs and so there is a need for new drug therapies for prostate cancer patients. Flavonoids, with their wide range of sources and diverse biological activities, have attracted much attention in the field of anti-tumor drug screening. In 2016, at least 58 flavonoids were reported to have anti-prostate cancer activity. In recent years, six additional flavonoid compounds have been found to have anti-prostate cancer potential. In this review, we have collected a large amount of evidence on the anti-prostate cancer effects of these six flavonoids, including a large number of cellular experiments and a small number of preclinical animal experiments. In addition, we predicted their drug-forming properties using Schrödinger's QikProp software and ADMETlab due to the lack of in vivo pharmacokinetic data for the six compounds. In conclusion, this review has fully confirmed the anti-prostate cancer effects of these six flavonoids, summarized their mechanisms of action and predicted their druggability. It provides a reference for the further development of these compounds into anti-prostate cancer drugs.

Phloretin inhibits transmissible gastroenteritis virus proliferation via multiple mechanisms

Transmissible gastroenteritis virus (TGEV), an enteropathogenic coronavirus, has caused huge economic losses to the pig industry, with 100% mortality in piglets aged 2 weeks and intestinal injury in pigs of other ages. However, there is still a shortage of safe and effective anti-TGEV drugs in clinics. In this study, phloretin, a naturally occurring dihydrochalcone glycoside, was identified as a potent antagonist of TGEV. Specifically, we found phloretin effectively inhibited TGEV proliferation in PK-15 cells, dose-dependently reducing the expression of TGEV N protein, mRNA, and virus titer. The anti-TGEV activity of phloretin was furthermore refined to target the internalization and replication stages. Moreover, we also found that phloretin could decrease the expression levels of proinflammatory cytokines induced by TGEV infection. In addition, we expanded the potential key targets associated with the anti-TGEV effect of phloretin to AR, CDK2, INS, ESR1, ESR2, EGFR, PGR, PPARG, PRKACA, and MAPK14 with the help of network pharmacology and molecular docking techniques. Furthermore, resistant viruses have been selected by culturing TGEV with increasing concentrations of phloretin. Resistance mutations were reproducibly mapped to the residue (S242) of main protease (Mpro). Molecular docking analysis showed that the mutation (S242F) significantly disrupted phloretin binding to Mpro, suggesting Mpro might be a potent target of phloretin. In summary, our findings indicate that phloretin is a promising drug candidate for combating TGEV, which may be helpful for developing pharmacotherapies for TGEV and other coronavirus infections.

Theranostic gold-in-gold cage nanoparticles enable photothermal ablation and photoacoustic imaging in biofilm-associated infection models

Biofilms are structured communities of microbial cells embedded in a self-produced matrix of extracellular polymeric substances. Biofilms are associated with many health issues in humans, including chronic wound infections and tooth decay. Current antimicrobials are often incapable of disrupting the polymeric biofilm matrix and reaching the bacteria within. Alternative approaches are needed. Here, we described a complex structure of a dextran-coated gold-in-gold cage nanoparticle that enabled photoacoustic and photothermal properties for biofilm detection and treatment. Activation of these nanoparticles with a near infrared laser could selectively detect and kill biofilm bacteria with precise spatial control and in a short timeframe. We observed a strong biocidal effect against both Streptococcus mutans and Staphylococcus aureus biofilms in mouse models of oral plaque and wound infections, respectively. These effects were over 100 times greater than those seen with chlorhexidine, a conventional antimicrobial agent. Moreover, this approach did not adversely affect surrounding tissues. We concluded that photothermal ablation using theranostic nanoparticles is a rapid, precise, and nontoxic method to detect and treat biofilm-associated infections.

Anticancer Potential of Natural Chalcones: In Vitro and In Vivo Evidence

There is no doubt that significant progress has been made in tumor therapy in the past decades. However, the discovery of new molecules with potential antitumor properties still remains one of the most significant challenges in the field of anticancer therapy. Nature, especially plants, is a rich source of phytochemicals with pleiotropic biological activities. Among a plethora of phytochemicals, chalcones, the bioprecursors of flavonoid and isoflavonoids synthesis in higher plants, have attracted attention due to the broad spectrum of biological activities with potential clinical applications. Regarding the antiproliferative and anticancer effects of chalcones, multiple mechanisms of action including cell cycle arrest, induction of different forms of cell death and modulation of various signaling pathways have been documented. This review summarizes current knowledge related to mechanisms of antiproliferative and anticancer effects of natural chalcones in different types of malignancies including breast cancers, cancers of the gastrointestinal tract, lung cancers, renal and bladder cancers, and melanoma.

Specificity Proteins (Sp) and Cancer

The specificity protein (Sp) transcription factors (TFs) Sp1, Sp2, Sp3 and Sp4 exhibit structural and functional similarities in cancer cells and extensive studies of Sp1 show that it is a negative prognostic factor for patients with multiple tumor types. In this review, the role of Sp1, Sp3 and Sp4 in the development of cancer and their regulation of pro-oncogenic factors and pathways is reviewed. In addition, interactions with non-coding RNAs and the development of agents that target Sp transcription factors are also discussed. Studies on normal cell transformation into cancer cell lines show that this transformation process is accompanied by increased levels of Sp1 in most cell models, and in the transformation of muscle cells into rhabdomyosarcoma, both Sp1 and Sp3, but not Sp4, are increased. The pro-oncogenic functions of Sp1, Sp3 and Sp4 in cancer cell lines were studied in knockdown studies where silencing of each individual Sp TF decreased cancer growth, invasion and induced apoptosis. Silencing of an individual Sp TF was not compensated for by the other two and it was concluded that Sp1, Sp3 and Sp4 are examples of non-oncogene addicted genes. This conclusion was strengthened by the results of Sp TF interactions with non-coding microRNAs and long non-coding RNAs where Sp1 contributed to pro-oncogenic functions of Sp/non-coding RNAs. There are now many examples of anticancer agents and pharmaceuticals that induce downregulation/degradation of Sp1, Sp3 and Sp4, yet clinical applications of drugs specifically targeting Sp TFs are not being used. The application of agents targeting Sp TFs in combination therapies should be considered for their potential to enhance treatment efficacy and decrease toxic side effects.

Phloretin inhibits glucose transport and reduces inflammation in human retinal pigment epithelial cells

During age-related macular degeneration (AMD), chronic inflammatory processes, possibly fueled by high glucose levels, cause a breakdown of the retinal pigment epithelium (RPE), leading to vision loss. Phloretin, a natural dihydroxychalcone found in apples, targets several anti-inflammatory signaling pathways and effectively inhibits transporter-mediated glucose uptake. It could potentially prevent inflammation and cell death of RPE cells through either direct regulation of inflammatory signaling pathways or through amelioration of high glucose levels. To test this hypothesis, ARPE-19 cells were incubated with or without phloretin for 1 h before exposure to lipopolysaccharide (LPS). Cell viability and the release of pro-inflammatory cytokines interleukin 6 (IL-6), IL-8 and vascular endothelial growth factor (VEGF) were measured. Glucose uptake was studied using isotope uptake studies. The nuclear levels of nuclear factor erythroid 2-related factor 2 (Nrf2) were determined alongside the phosphorylation levels of mitogen-activated protein kinases. Phloretin pretreatment reduced the LPS-induced release of IL-6 and IL-8 as well as VEGF. Phloretin increased intracellular levels of reactive oxygen species and nuclear translocation of Nrf2. It also inhibited glucose uptake into ARPE-19 cells and the phosphorylation of Jun-activated kinase (JNK). Subsequent studies revealed that Nrf2, but not the inhibition of glucose uptake or JNK phosphorylation, was the main pathway of phloretin's anti-inflammatory activities. Phloretin was robustly anti-inflammatory in RPE cells and reduced IL-8 secretion via activation of Nrf2 but the evaluation of its potential in the treatment or prevention of AMD requires further studies.

Phloretin, as a Potent Anticancer Compound: From Chemistry to Cellular Interactions

Phloretin is a natural dihydrochalcone found in many fruits and vegetables, especially in apple tree leaves and the Manchurian apricots, exhibiting several therapeutic properties, such as antioxidant, antidiabetic, anti-inflammatory, and antitumor activities. In this review article, the diverse aspects of the anticancer potential of phloretin are addressed, presenting its antiproliferative, proapoptotic, antimetastatic, and antiangiogenic activities in many different preclinical cancer models. The fact that phloretin is a planar lipophilic polyphenol and, thus, a membrane-disrupting Pan-Assay Interference compound (PAIN) compromises the validity of the cell-based anticancer activities. Phloretin significantly reduces membrane dipole potential and, therefore, is expected to be able to activate a number of cellular signaling pathways in a non-specific way. In this way, the effects of this minor flavonoid on Bax and Bcl-2 proteins, caspases and MMPs, cytokines, and inflammatory enzymes are all analyzed in the current review. Moreover, besides the anticancer activities exerted by phloretin alone, its co-effects with conventional anticancer drugs are also under discussion. Therefore, this review presents a thorough overview of the preclinical anticancer potential of phloretin, allowing one to take the next steps in the development of novel drug candidates and move on to clinical trials.

Phloretin in Benign Prostate Hyperplasia and Prostate Cancer: A Contemporary Systematic Review

Currently, medication for benign prostate hyperplasia (BPH) and prostate cancer (PCa) are mainly based on modulating the hormone and nervous systems. However, side effects often affect patients, and might decrease their commitment to continuing the medication and lower their quality of life. Some studies have indicated that chronic inflammation might be the cause of BPH and PCa. Based on this hypothesis, the effect of phloretin, a potent anti-inflammatory and anti-oxidative flavonoid, has been researched since 2010. Results from animal and in-vitro studies, obtained from databases, also indicate that the use of phloretin in treating BPH and PCa is promising. Due to its effect on inflammatory cytokines, apoptosis or anti-apoptosis, reactive oxygen species, anti-oxidant enzymes and oxidative stress, phloretin is worthy of further study in human clinical trials regarding safety and effective dosages.

Chemotherapeutics activities of dietary phytoestrogens against prostate cancer: From observational to clinical studies

Prostate cancer remains one of the most frequent and deadliest malignancies in males, where the rate of disease progression is closely associated with the type of dietary intake, specifically Western-style diet. Indeed intake of the Asian diet, which contains abundant phytoestrogens, is inversely correlated with a higher risk of prostate cancer, suggesting a chemoprotective effect of phytoestrogen against cancer progression. Although the role of phytoestrogens in cancer treatment was well documented, their impact on prostate cancer is not well understood. Therefore, the present review discusses the possible chemopreventive effect of phytoestrogens, emphasizing their efficacy at the different stages of carcinogenesis. Furthermore, phytoestrogens provide a cytoprotective effect in conventional chemotherapy and enhance chemosensitivity to tumor cells, which have also been discussed. This compilation provides a solid basis for future research on phytoestrogens as a promising avenue for anticancer drug development and also recommends these beneficiary compounds in the daily diet to manage and prevent prostate cancer.

Phloretin Ameliorates Testosterone-Induced Benign Prostatic Hyperplasia in Rats by Regulating the Inflammatory Response, Oxidative Stress and Apoptosis

The inflammatory process is proposed to be one of the factors to benign prostatic enlargement (BPH), and this is the first study examining the anti-inflammatory ability of phloretin in treating rats with testosterone-induced BPH. BPH would be induced by testosterone (10 mg/kg/day testosterone subcutaneously for 28 days), and the other groups of rats were treated with phloretin 50 mg/kg/day or 100 mg/kg/day orally (phr50 or phr100 group) after induction. Prostate weight and prostate weight to body weight ratio were significantly reduced in the Phr100 group. Reduced dihydrotestosterone without interfering with 5α-reductase was observed in the phr100 group. In inflammatory proteins, reduced IL-6, IL-8, IL-17, NF-κB, and COX-2 were seen in the phr100 group. In reactive oxygen species, malondialdehyde was reduced, and superoxide dismutase and glutathione peroxidase were elevated in the phr100 group. In apoptotic assessment, elevated cleaved caspase-3 was observed in rats of the phr100 group. Enhanced pro-apoptotic Bax and reduced anti-apoptotic Bc1-2 could be seen in the phr100 group. In histological stains, markedly decreased glandular hyperplasia and proliferative cell nuclear antigen were observed with reduced expression in the phr100 group. Meanwhile, positive cells of terminal deoxynucleotidyl transferase dUTP nick end labeling were increased in the phr100 group. In conclusion, the treatment of phloretin 100 mg/kg/day could ameliorate testosterone-induced BPH.