Inhibition of HIF-1 alpha and VEGF expression by the chemopreventive bioflavonoid apigenin is accompanied by Akt inhibition in human prostate carcinoma PC3-M cells

Electro-Metabolic Coupling of Cumulus-Oocyte Complex

Oocyte-cumulus cell interaction is essential for oocyte maturation and competence. The bidirectional crosstalk network mediated by gap junctions is fundamental for the metabolic cooperation between these cells. As cumulus cells exhibit a more glycolytic phenotype, they can provide metabolic substrates that the oocyte can use to produce ATP via oxidative phosphorylation. The impairment of mitochondrial activity plays a crucial role in ovarian aging and, thus, in fertility, determining the success or failure of assisted reproductive techniques. This review aims to deepen the knowledge about the electro-metabolic coupling of the cumulus-oocyte complex and to hypothesize a putative role of potassium channel modulators in order to improve fertility, promote intracellular Ca2+ influx, and increase the mitochondrial biogenesis and resulting ATP levels in cumulus cells.

Potential anti-cancer activity of Moringa oleifera derived bio-active compounds targeting hypoxia-inducible factor-1 alpha in breast cancer

Breast cancer (BC) will become a highly detected malignancy in females worldwide in 2023, with over 2 million new cases. Studies have established the role of hypoxia-inducible factor-1α (HIF1α), a transcription factor that controls cellular response to hypoxic stress, and is essential for BC spread. HIF-1 is implicated in nearly every critical stage of the metastatic progression, including invasion, EMT, intravasation, extravasation, angiogenesis, and the formation of metastatic niches. HIF-1 overexpression has been associated with poor prognosis and increased mortality in BC patients. This is accomplished by controlling the expression of HIF-1 target genes involved in cell survival, angiogenesis, metabolism, and treatment resistance. Studies have indicated that inhibiting HIF-1 has an anti-cancer effect on its own and that inhibiting HIF-1-mediated signaling improves the efficacy of anti-cancer therapy. Approximately 74 % of recognized anti-cancer drugs are sourced from plant species. Studies on anti-cancer characteristics of phytochemicals derived from Moringa oleifera (MO), also known as the 'Tree of Life', have revealed a high therapeutic potential for BC. In this review, we have highlighted the various mechanisms through which bioactive compounds present in MO may modulate HIF and its regulatory genes/pathways, to prove their efficacy in treating and preventing BC.

Synthesis and anti-hepatocellular carcinoma evaluation of salicylic acid-modified indole trimethoxy flavonoid derivatives

Simultaneous inhibition of tumor vasculature and the glycolysis pathway may be a targeted anti-tumor strategy to inhibit tumor nutrient supply. Flavonoids are natural products with strong biological activity, which inhibit hypoxia induction factor 1α (HIF-1α) regulating glycolysis and tumor angiogenesis, while salicylic acid can reduce the glycolysis level of tumor cells by inhibiting related rate-limiting enzymes. A series of salicylic acid-modified indole trimethoxy-flavone derivatives were designed and synthesized by introducing benzotrimethoxy-structure commonly used in blood vessel blockers, and their anti-tumor activities were evaluated. Among them, compound 8f exhibited significant anti-proliferative activity against two hepatoma cells, HepG-2 and SMMC-7721, with IC50 values of 4.63 ± 1.13 μM and 3.11 ± 0.35 μM, respectively. Colony formation experiments also further verified its excellent in vitro anti-tumor activity. In addition, compound 8f showed the ability to induce apoptosis in SMMC-7721 cells in a concentration-dependent manner. After treatment with compound 8f, the expressions of the rate-limiting enzymes PKM2, PFKM, HK2 and tumor angiogenesis-related vascular endothelial growth factor of the glycolytic pathway were all down-regulated, and the lactate level in the hepatoma cell SMMC-7721 was significantly reduced. The morphology of the nucleus and tubulin was also observed to disperse gradually with the increase of compound 8f concentration. And compound 8f showed strong binding ability to tubulin. Our results suggest that the strategy of synthesizing the salicylic acid-modified indole flavone derivative 8f is a way to obtain active anti-tumor candidate compounds that may be further developed as targeted agents to inhibit tumor vasculature and glycolytic pathways.

A Randomized Double-blind Clinical Trial of Weierkang Pills for the Treatment of Chronic Atrophic Gastritis

BACKGROUND AND GOALS

There are currently no standard treatments for chronic atrophic gastritis and traditional Chinese medicine may be effective. This study aims to investigate the efficacy and safety of Weierkang pills in treating chronic atrophic gastritis.

MATERIALS AND METHODS

There were 108 patients in our study. They were randomly assigned to 2 groups. In group A, patients received Weierkang pills and patients in group B received folic acid combined with teprenone. Symptoms, endoscopic scores, and biopsy specimens were compared at baseline and 3 months after treatment. Meanwhile, the expressions of vascular endothelial growth factor and trefoil factor 3 (TFF3) in biopsy specimens were also compared.

RESULTS

Our study showed that the total effective rates of atrophy/intestinal metaplasia in group A reached the same level as group B (51.7% vs. 40.0%, P =0.419). Weierkang significantly improved the total effective rate of atrophy/intestinal metaplasia in gastric angle compared with group B (64.7% vs. 33.3%, P =0.024). Weierkang can significantly lower the total Kyoto risk score (2.6±1.1 vs. 3.3±1.0, P =0.002) and atrophy score (1.4±0.6 vs. 1.8±0.5, P =0.001) after treatment. In addition, Weierkang improves symptoms (1.3±1.3 vs. 2.3±1.8, P =0.003) and epigastric pain (0.2±0.4 vs. 0.5±0.6, P =0.041). The expression of TFF3 in gastric mucosa decreased significantly after treatment with Weierkang ( P =0.002).

CONCLUSIONS

Weierkang can improve the endoscopic appearance and pathologic changes of chronic atrophic gastritis patients. Symptoms also improved. TFF3 may be involved the pathophysiology mechanism.

Design, synthesis, and antitumor evaluation of trimethoxyflavonoid with arylurea structure against hepatocellular carcinoma

Simultaneous targeting of tumor vasculature and inhibitors of tumor cell glycolysis may be a promising antitumor strategy. Here, we reported the total synthesis and biological evaluation of A-ring arylurea flavonoid derivatives with B-ring trimethoxy group, which exhibited potent antitumor activity against a variety of tumor cells in vitro. Most of the derivatives showed in vitro antitumor activity on HepG-2, HGC-27, MDA-MB-231, and A549 cells. Among them, compounds 8e, 8f, 8g, 8h, 8j, and 8l also exhibited significant anti-proliferation effects on liver tumor cell subtypes BEL-7402 and SMMC-7721. Compound 8l had the lowest IC₅₀ value (5.61 ± 0.39 μM) on HepG-2 cells, and showed the effects of inhibiting colony formation, arresting the cell cycle in G₀ /G₁ phase, and inducing apoptosis in a concentration-dependent manner. In addition, the toxicity of compound 8l on human normal cells LO2 and GES-1 was lower than that of sorafenib. The inhibitory effects of compound 8l on the expression of glycolytic rate-limiting enzymes HKII, PFK-1, PKM2 and vascular endothelial growth factor were further evaluated. Corresponding reduction in intracellular lactate was also detected after compound 8 treatment. Our results support an antitumor strategy targeting tumor vasculature and glycolysis to discover and develop a new generation of antitumor drugs.

Systemic Effects Reflected in Specific Biomarker Patterns Are Instrumental for the Paradigm Change in Prostate Cancer Management: A Strategic Paper

Prostate cancer (PCa) is reported as the most common malignancy and second leading cause of death in America. In Europe, PCa is considered the leading type of tumour in 28 European countries. The costs of treating PCa are currently increasing more rapidly than those of any other cancer. Corresponding economic burden is enormous, due to an overtreatment of slowly developing disease on one hand and underestimation/therapy resistance of particularly aggressive PCa subtypes on the other hand. The incidence of metastatic PCa is rapidly increasing that is particularly characteristic for young adults. PCa is a systemic multi-factorial disease resulting from an imbalanced interplay between risks and protective factors. Sub-optimal behavioural patterns, abnormal stress reactions, imbalanced antioxidant defence, systemic ischemia and inflammation, mitochondriopathies, aberrant metabolic pathways, gene methylation and damage to DNA, amongst others, are synergistically involved in pathomechanisms of PCa development and progression. To this end, PCa-relevant systemic effects are reflected in liquid biopsies such as blood patterns which are instrumental for predictive diagnostics, targeted prevention and personalisation of medical services (PPPM/3P medicine) as a new paradigm in the overall PCa management. This strategic review article highlights systemic effects in prostate cancer development and progression, demonstrates evident challenges in PCa management and provides expert recommendations in the framework of 3P medicine.

Apigenin Induces Autophagy and Cell Death by Targeting EZH2 under Hypoxia Conditions in Gastric Cancer Cells

Hypoxia is a major obstacle to gastric cancer (GC) therapy and leads to chemoresistance as GC cells are frequently exposed to the hypoxia environment. Apigenin, a flavonoid found in traditional medicine, fruits, and vegetables and an HDAC inhibitor, is a powerful anti-cancer agent against various cancer cell lines. However, detailed mechanisms involved in the treatment of GC using APG are not fully understood. In this study, we investigated the biological activity of and molecular mechanisms involved in APG-mediated treatment of GC under hypoxia. APG promoted autophagic cell death by increasing ATG5, LC3-II, and phosphorylation of AMPK and ULK1 and down-regulating p-mTOR and p62 in GC. Furthermore, our results show that APG induces autophagic cell death via the activation of the PERK signaling, indicating an endoplasmic reticulum (ER) stress response. The inhibition of ER stress suppressed APG-induced autophagy and conferred prolonged cell survival, indicating autophagic cell death. We further show that APG induces ER stress- and autophagy-related cell death through the inhibition of HIF-1α and Ezh2 under normoxia and hypoxia. Taken together, our findings indicate that APG activates autophagic cell death by inhibiting HIF-1α and Ezh2 under hypoxia conditions in GC cells.

Antiproliferative and Mitochondrial Protective Effects of Apigenin in an Oxygen-Induced Retinopathy In Vivo Mouse Model

Purpose: To investigate the effects of a common dietary flavonoid apigenin on retinal endothelial cell proliferation, retinal morphological structure, and apoptotic cell death in an oxygen-induced retinopathy (OIR) mouse model to evaluate the possibility of the use of apigenin in the treatment of ocular neovascular diseases (ONDs). Methods: Ninety-six newborn C57BL/6J mice were included. Eight groups were randomized, each including 12 mice. Two negative control groups were kept in room air: the first without any injection and the second received intravitreal (IV) dimethyl sulfoxide (DMSO), which is the solvent we used. The OIR groups were exposed to 75% ± 2% oxygen from postnatal days (PD) 7 to 12. On PD 12, the mice were randomly assigned to 6 groups: 2 OIR control groups (1 received no injection, 1 received IV-DMSO), 2 IV-apigenin groups (10 and 20 μg/mL), and 2 intraperitoneal (IP)-apigenin groups (10 and 20 mg/kg). We quantified retinal endothelial cell proliferation by counting neovascular tufts in cross-sections and examined histological and ultrastructural changes through light and electron microscopy. We evaluated apoptosis by terminal deoxynucleotidyl transferase-mediated nick end-labeling (TUNEL). Results: We detected a significant increase in endothelial cell proliferation in the OIR groups. Groups receiving apigenin, both IP and IV, had significant decreases in endothelial cells, atypical mitochondrion count, and apoptotic cells compared with the groups receiving no injections. None of the apigenin-injected groups revealed cystic degeneration or cell loss. Conclusions: Apigenin suppresses neovascularization, has antiapoptotic and antioxidative effects in an OIR mouse model, and can be considered a promising agent for treating OND. Clinical trial (Project number: DA15/19).

Anticancer effects of root and beet leaf extracts (Beta vulgaris L.) in cervical cancer cells (HeLa)

Cervical cancer is the fourth leading cause of cancer mortality in women worldwide. Beetroot (Beta vulgaris L.) has bioactive compounds that can inhibit the progression of different types of cancer. To analyze the antiproliferative effects of beet leaf and root extracts, we performed MTT, clonogenic survival, cell cycle analysis, Annexin/PI labeling, and western blotting. Here, we report that 10 and 100 μg/ml of root and leaf extracts decreased cell viability and potentiated rapamycin and cisplatin effects while decreased the number of large colonies, especially at 10 μg/ml (293.6 of control vs. 200.0 of leaf extract, p = .0059; 138.6 of root extract, p = .0002). After 48 hr, 100 μg/ml of both extracts led to increased sub-G1 and G0/G1 populations. In accordance, 100 μg/ml of root extract induced early apoptosis (mean = 0.64 control vs. 1.56 root; p = .048) and decreased cell size (p < .0001). Both extracts decreased phosphorylation and expression of mechanistic Target of Rapamycin (mTOR) signaling, especially by inhibiting ribosomal protein S6 (S6) phosphorylation, increasing cleaved poly(ADP-ribose) polysomerase 1 (PARP1) and Bcl-2-like protein 11 (BIM), and decreasing cyclin D1 expression, which regulates cell cycle progression. Here, we demonstrate that beetroot and leaf extracts could be an efficient strategy against cervical cancer.

Bioassay-Guided Identification of the Antiproliferative Compounds of Cissus trifoliata and the Transcriptomic Effect of Resveratrol in Prostate Cancer Pc3 Cells

The bioassay-guided fractionation of a CHCl₃-MeOH extract from the stems of Cissus trifoliata identified an active fraction against PC3 prostate cancer cells. The treatment for 24 h showed an 80% reduction in cell viability (p ≤ 0.05) by a WST-1 assay at a concentration of 100 μg/mL. The HPLC-QTOF-MS analysis of the fraction showed the presence of coumaric and isoferulic acids, apigenin, kaempferol, chrysoeriol, naringenin, ursolic and betulinic acids, hexadecadienoic and octadecadienoic fatty acids, and the stilbene resveratrol. The exposure of PC3 cells to resveratrol (IC₂₅ = 23 μg/mL) for 24 h induced significant changes in 847 genes (Z-score ≥ ±2). The functional classification tool of the DAVID v6.8 platform indicates that the underlying molecular mechanisms against the proliferation of PC3 cells were associated (p ≤ 0.05) with the process of differentiation and metabolism. These findings provide experimental evidence suggesting the potential of C. trifoliata as a promising natural source of anticancer compounds.

The Hallmarks of Flavonoids in Cancer

Flavonoids represent an important group of bioactive compounds derived from plant-based foods and beverages with known biological activity in cells. From the modulation of inflammation to the inhibition of cell proliferation, flavonoids have been described as important therapeutic adjuvants against several diseases, including diabetes, arteriosclerosis, neurological disorders, and cancer. Cancer is a complex and multifactor disease that has been studied for years however, its prevention is still one of the best known and efficient factors impacting the epidemiology of the disease. In the molecular and cellular context, some of the mechanisms underlying the oncogenesis and the progression of the disease are understood, known as the hallmarks of cancer. In this text, we review important molecular signaling pathways, including inflammation, immunity, redox metabolism, cell growth, autophagy, apoptosis, and cell cycle, and analyze the known mechanisms of action of flavonoids in cancer. The current literature provides enough evidence supporting that flavonoids may be important adjuvants in cancer therapy, highlighting the importance of healthy and balanced diets to prevent the onset and progression of the disease.

Chronic atrophic gastritis and intestinal metaplasia induced by high-salt and N-methyl-N'-nitro-N-nitrosoguanidine intake in rats

The aim of the present study was to induce chronic atrophic gastritis (CAG) with intestinal metaplasia (IM) in rats by administering saturated salt and methyl-N'-nitro-N-nitrosoguanidine (MNNG) via oral gavage. Changes in gastric mucosal blood microcirculation and activation of the cyclo-oxygenase-2 (COX-2)/hypoxia inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) signaling pathway during CAG and IM development were investigated. After administering saturated salt and MNNG for 25 weeks, mild atrophy was detected in the stomach of model rats using hematoxylin and eosin staining. CAG with IM was successfully induced in the gastric mucosa of the model rats after 35 weeks. Gastric mucosal blood flow was decreased in comparison with controls as early as 15 weeks after treatment to induce CAG and the mRNA expression levels of COX-2, HIF-1α, vascular endothelial growth factor receptor (VEGFR)1 and VEGFR2 were increased in comparison with untreated rats as early as 25 weeks after treatment. HIF-1α, COX-2 and VEGFR2 expression levels were increased as early as 25 weeks after CAG induction treatment when compared to controls and HIF-1α, COX-2, VEGFR1 and VEGFR2 expression levels were significantly increased after 35 weeks. These findings indicated that administering saturated salt and MNNG by gavage for 35 weeks successfully induced CAG and IM in rats. Furthermore, the microcirculation was disturbed before activation of the COX-2/HIF-1α/VEGF signaling pathway.

Protein kinase 2 (CK2): a potential regulator of immune cell development and function in cancer

Protein kinase CK2, formally known as casein kinase II, is ubiquitously expressed and highly conserved serine/threonine or tyrosine kinase enzyme that regulates diverse signaling pathways responsible for cellular processes (i.e., cell proliferation and apoptosis) via interactions with over 500 known substrates. The enzyme's physiological interactions and cellular functions have been widely studied, most notably in the blood and solid malignancies. CK2 has intrinsic role in carcinogenesis as overexpression of CK2 subunits (α, α`, and β) and deregulation of its activity have been linked to various forms of cancers. CK2 also has extrinsic role in cancer stroma or in the tumor microenvironment (TME) including the immune cells. However, very few research studies have focused on extrinsic role of CK2 in regulating immune responses as a therapeutic alternative for cancer. The following review discusses CK2's regulation of key signaling events [Nuclear factor kappa B (NF-κB), Janus kinase/signal transducer and activators of transcription (JAK/STAT), Hypoxia inducible factor-1alpha (HIF-1α), Cyclooygenase-2 (COX-2), Extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK), Notch, Protein kinase B/AKT, Ikaros and Wnt] that can influence the development and function of immune cells in cancer. Potential clinical trials using potent CK2 inhibitors will facilitate and improve the treatment of human malignancies.

Reductive Stress, Bioactive Compounds, Redox-Active Metals, and Dormant Tumor Cell Biology to Develop Redox-Based Tools for the Treatment of Cancer

Significance: Cancer is related to redox biology from many points of view, such as initiation and promotion, metabolism and growth, invasion and metastasis, vascularization, or through the interaction with the immune system. In addition, this extremely complex relationship depends on the redox homeostasis of each cellular compartment, which might be used to fight cancer. Recent Advances: New ways of modulating specific and little explored aspects of redox biology have been revealed, as well as new delivery methods or uses of previously known treatments against cancer. Here, we review the latest experimental evidence regarding redox biology in cancer treatment and analyze its potential impact in the development of improved and more effective antineoplastic therapies. Critical Issues: A critical issue that deserves particular attention is the understanding that both extremes of redox biology (i.e., oxidative stress [OS] and reductive stress) might be useful or harmful in relation to cancer prevention and treatment. Future Directions: Additional research is needed to understand how to selectively induce reductive or OS adequately to avoid cancer proliferation or to induce cancer cell death.

Apigenin Enhanced Antitumor Effect of Cisplatin in Lung Cancer via Inhibition of Cancer Stem Cells

Cancer stem cell theory has been proposed to explain tumor heterogeneity and the carcinogenesis process. Highly tumorigenic lung cancer stem cells develop resistance to cisplatin (CDDP), a common chemotherapy drug. Herein, we attempted to clarify whether apigenin (API) can improve the antitumor efficiency of CDDP in lung cancer using cancer stem cells. Lung cancer stem cells were identified as CD 133 positive cancer cells in non-small cell lung cancer (NSCLC) A549, H1299 cells and CDDP-resistant NSCLC A549R cells. The cytotoxic effect of API was measured in CDDP-treated A549, H1299, and A549R cells. API repressed CD 133 positive cells and enhanced the antitumor effect of CDDP in A549, H1299, and A549R cells. The synergistic antitumor effect of API and CDDP was blocked by addition of the p53 inhibitor Pifithrin-α, and siRNA targeting the p53 gene in A549R cells. Furthermore, API eliminates CDDP-induced CSC via p53, since A549R cells lacking p53 and Pifithrin-α addition derepressed the decrease in CD 133 positive cells after API treatment in CDDP-treated A549 and A549R cells. The findings indicate that API might eliminate cancer stem cells and enhance the antitumor effects of CDDP in NSCLC via p53.

FB-15 inhibits MGC-803 cells growth by regulating energy metabolism

In this study, we scrutinized the anticancer effects of FB-15 on human gastric carcinoma MGC-803 cells in vitro and vivo, and its preliminary effect on tubulin and HIF-1α. We confirmed that FB-15 not only inhibited the proliferation of a large number of cells in a concentration and time-dependent manner but also inhibited proliferation of a single cell to form clones. FB-15 manifested little cytotoxicity for normal stomach cells GES-1. The flow cytometry analysis displayed that FB-15 induced apoptosis MGC-803 cells and mainly arrested cells in the S phase in a concentration-dependent manner. The results of the wound healing assay indicated that FB-15 suppressed cell migration. Furthermore, the western blotting showed that FB-15 down-regulated the expression of β3-tubulin and HIF-1α, consistent with Immunohistochemical assay. The binding modes of FB-15 with tubulin were clarified by molecular docking. FB-15 significantly suppressed the growth of MGC-803 gastric cancer tumors. The inhibitory effect of FB-15 on tumor growth was superior to 5-Fu. Taken together, these results provided evidence for FB-15 to be used as an effective anticancer drug candidate for gastric cancer.

Resveratrol protects mitochondrial quantity by activating SIRT1/PGC-1α expression during ovarian hypoxia

PURPOSE

Resveratrol is a well-known potent activator of sirtuin-1 (SIRT1). We investigated the direct effects of hypoxia and resveratrol on SIRT1/ peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) pathways, vascular endothelial growth factor (VEGF), hypoxia-inducible factor (HIF)-1α, and mitochondrial quantity in a steroidogenic human ovarian granulosa-like tumor cell line (KGN) cells.

METHODS

KGN cells were cultured with cobalt chloride (CoCl2; a hypoxia-mimicking agent) and/or resveratrol. The mRNA and protein levels, protein secretion, and intracellular localization were assessed by real-time PCR, Western blot analysis, ELISA, and immunofluorescence staining, respectively. Mitochondrial quantity was measured based on the mitochondrial DNA (mtDNA) copy number.

RESULTS

CoCl2 simultaneously attenuated the levels of SIRT1 and mtDNA expression, and induced the levels of VEGF protein production. In contrast, resveratrol significantly increased the levels of SIRT1 and mtDNA copy number, but reduced VEGF production in normoxia. Resveratrol could recover CoCl2-suppressed SIRT1 and mtDNA expression and antagonize CoCl2-induced VEGF production. CoCl2 treatment resulted in a downregulation of PGC-1α expression, and this effect was recovered by resveratrol. Resveratrol significantly suppressed the production of the CoCl2-induced HIF-1α and VEGF proteins.

CONCLUSION

These results suggest that resveratrol improves mitochondrial quantity by activating the SIRT1/PGC-1α pathway and inhibits VEGF induction through HIF-1α under hypoxic conditions.

Overcoming the hypoxia-induced drug resistance in liver tumor by the concurrent use of apigenin and paclitaxel

The chemotherapeutic efficacy of paclitaxel against hypoxic tumors is usually unsatisfactory, which is partially due to the so-called hypoxia-induced drug resistance. The mechanism of hypoxia-induced resistance is primarily associated with hypoxia-inducible factor 1α (HIF-1α), which is an oxygen-sensitive transcriptional activator coordinating the cellular response to hypoxia. Apigenin is a natural occurring HIF-1α inhibitor that can suppress the expression of HIF-1α through multiple pathways and reverse the hypoxia-induced resistance found in cancer cells. Here we report that the use of apigenin can suppress the HIF-1α expression in hypoxic tumors through the simultaneous inhibition of the AKT/p-AKT pathway and HSP90, which is beneficial for enhancing the anticancer activity of the co-administered paclitaxel. The potential synergistic effect of apigenin and paclitaxel was further validated on HepG2 cell line and tumor-bearing mouse models.

Natural Compounds in Prostate Cancer Prevention and Treatment: Mechanisms of Action and Molecular Targets

Prostate cancer (PCa) represents a major cause of cancer mortality among men in developed countries. Patients with recurrent disease initially respond to androgen-deprivation therapy, but the tumor eventually progresses into castration-resistant PCa; in this condition, tumor cells acquire the ability to escape cell death and develop resistance to current therapies. Thus, new therapeutic approaches for PCa management are urgently needed. In this setting, natural products have been extensively studied for their anti-PCa activities, such as tumor growth suppression, cell death induction, and inhibition of metastasis and angiogenesis. Additionally, numerous studies have shown that phytochemicals can specifically target the androgen receptor (AR) signaling, as well as the PCa stem cells (PCSCs). Interestingly, many clinical trials have been conducted to test the efficacy of nutraceuticals in human subjects, and they have partially confirmed the promising results obtained in vitro and in preclinical models. This article summarizes the anti-cancer mechanisms and therapeutic potentials of different natural compounds in the context of PCa prevention and treatment.

Antitumor and Anti-Invasive Effect of Apigenin on Human Breast Carcinoma through Suppression of IL-6 Expression

Interleukin (IL)-6 plays a crucial role in the progression, invasion, and metastasis of breast cancer. Triple-negative breast cancer (TNBC) cell line MDA-MB-231 is known for its aggressive metastasis. Epithelial to mesenchymal transition (EMT) is a critical process in cancer metastasis. The positive correlation between IL-6 and EMT in tumor microenvironment is reported. We found significantly upregulated IL-6 expression in MDA-MB-231 cells. A blockade of IL-6 expression decreased levels of phosphorylated signal transducer and activator of transcription 3 (pSTAT3), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), phosphorylated protein kinase B (pAkt), and cell cycle-related molecules, including cyclin-dependent kinases (CDKs) and cyclins in MDA-MB-231 cells. A short-hairpin RNA (shRNA)-mediated blockade of IL-6 expression inhibited migration and N-cadherin expression and induced E-cadherin expression in MDA-MB-231 cells. Growth rate was slower for the tumors derived from IL-6 shRNA-treated MDA-MB-231 cells than for those derived from control shRNA-treated MDA-MB-231 cells. The expression of pSTAT3, phosphorylated extracellular signal-regulated kinase (pERK), PI3K, pAkt, snail, vimentin, and N-cadherin was significantly lower in tumors from IL-6 shRNA-treated MDA-MB cells. In addition, apigenin treatment significantly inhibited the growth of MDA-MB-231-derived xenograft tumors along with the protein expressions of pSTAT3, pERK, IL-6, PI3K, pAkt, and N-cadherin. Our results demonstrate that the anti-invasive effect of apigenin in MDA-MB-231-derived xenograft tumors is mediated by the inhibition of IL-6-linked downstream signaling pathway.

Weiqi Decoction Attenuated Chronic Atrophic Gastritis with Precancerous Lesion through Regulating Microcirculation Disturbance and HIF-1α Signaling Pathway

Aim

Chronic atrophic gastritis (CAG), the precancerous lesions of gastric cancer, plays an important role in the stepwise process of gastric cancer. The ancient Chinese medicine believes in that Qi deficiency and blood stasis are involved in the pathogenesis of CAG. Weiqi decoction, a classical formula from Longhua Hospital, could supplement Qi and activate blood circulation of human beings and has been used for treating CAG in clinic over twenty years. The study aims to clarify the effect and underlying molecular mechanism of Weiqi decoction on CAG rats.

Methods

Forty-eight male Wistar rats were divided randomly into six groups: control group, model group, folic acid group, and WQD-treated groups at doses of 4 g/kg, 2 g/kg, and 1 g/kg, with eight rats in each group. MNNG and saturated NaCl were used to induce CAG rat with precancerous lesion (intestinal metaplasia and dysplasia). After 40 weeks, gastric mucosal blood flow was measured using Laser Doppler Flowmetry. The pathological changes of the gastric mucosa were identified by H&E staining and AB-PAS staining. The protein expression of COX-2, HIF-1α, VEGFR1, VEGFR2, Ki67, and cleaved caspase 3 in the gastric tissues was measured by western blotting approach. Gene expression of COX-2, HIF-1α, VEGF, VEGFR1, VEGFR2, Ang-1, and Ang-2 was detected by using Quantitative PCR method. The PGE2 concentrations in serum were detected by ELISA method. The protein expression of Ki67 in gastric mucosa was also detected by immunohistochemistry.

Results

Compared with control rats, atrophy and intestinal metaplasia as well as the microcirculation disturbance of gastric mucosa were induced in the stomach of CAG rats identified by the H&E and AB-PAS staining as well as microcirculation measurement, which could be significantly attenuated by WQD treatment. Moreover, compared with the control group, the protein and gene expression of COX-2, HIF-1α, VEGFR1, and VEGFR2 in gastric tissues of pylorus was obviously increased and the serum PGE2 level was significantly deceased in CAG rats, which could be significantly counteracted by WQD administration. However, the gene expression of Ang-1 and Ang-2 was not significant difference between control rats and CAG rats, and WQD also had no significant effect on the gene expression of Ang-1 and Ang-2. Furthermore, the increased cell proliferation marked by upregulated protein expression of Ki67 and decreased cell apoptosis marked by downregulated protein expression of cleaved caspase 3 in stomach of pylorus in CAG rats were obviously reversed by WQD treatment.

Conclusion

WQD attenuated CAG with precancerous lesion through regulating gastric mucosal blood flow disturbance and HIF-1α signaling pathway.

The Role of Herbal Bioactive Components in Mitochondria Function and Cancer Therapy

Mitochondria are highly dynamic double-membrane organelles which play a well-recognized role in ATP production, calcium homeostasis, oxidation-reduction (redox) status, apoptotic cell death, and inflammation. Dysfunction of mitochondria has long been observed in a number of human diseases, including cancer. Targeting mitochondria metabolism in tumors as a cancer therapeutic strategy has attracted much attention for researchers in recent years due to the essential role of mitochondria in cancer cell growth, apoptosis, and progression. On the other hand, a series of studies have indicated that traditional medicinal herbs, including traditional Chinese medicines (TCM), exert their potential anticancer effects as an effective adjunct treatment for alleviating the systemic side effects of conventional cancer therapies, for reducing the risk of recurrence and cancer mortality and for improving the quality of patients' life. An amazing feature of these structurally diverse bioactive components is that majority of them target mitochondria to provoke cancer cell-specific death program. The aim of this review is to summarize the in vitro and in vivo studies about the role of these herbs, especially their bioactive compounds in the modulation of the disturbed mitochondrial function for cancer therapy.

A critical review on anti-angiogenic property of phytochemicals

Angiogenesis, a process involved in neovascularization, has been found to be associated with several metabolic diseases like cancer, retinopathy etc. Thus, currently, the focus on anti-angiogenic therapy for treatment and prevention of diseases has gained significant attention. Currently available Food and Drug Administration (FDA) approved drugs are targeting either vascular endothelial growth factor or it's receptor, but in the long term, these approaches were shown to cause several side effects and the chances of developing resistance to these drugs is also high. Therefore, identification of safe and cost-effective anti-angiogenic molecules is highly imperative. Over the past decades, dietary based natural compounds have been studied for their anti-angiogenic potential which provided avenues in improving the angiogenesis based therapy. In this review, major emphasis is given to the molecular mechanism behind anti-angiogenic effect of natural compounds from dietary sources.

Design, synthesis, and preliminary biological evaluation of 3′,4′,5′-trimethoxy flavonoid salicylate derivatives as potential anti-tumor agents

According to the combination principle, target compounds were designed; compound10vmight be a promising multiple target anti-tumor agent candidate.

Apigenin Inhibits UVB-Induced Skin Carcinogenesis: The Role of Thrombospondin-1 as an Anti-Inflammatory Factor

We have previously demonstrated that apigenin promotes the expression of antiangiogenic protein thrombospondin-1 (TSP1) via a mechanism driven by mRNA-binding protein HuR. Here, we generated a novel mouse model with whole-body THBS-1 gene knockout on SKH-1 genetic background, which allows studies of UVB-induced acute skin damage and carcinogenesis and tests TSP1 involvement in apigenin's anticancer effects. Apigenin significantly inhibited UVB-induced carcinogenesis in the wild-type (WT) animals but not in TSP1 KO (TKO) mice, suggesting that TSP1 is a critical component of apigenin's chemopreventive function in UVB-induced skin cancer. Importantly, TKO mice presented with the elevated cutaneous inflammation at baseline, which was manifested by increased inflammatory infiltrates (neutrophils and macrophages) and elevated levels of the two key inflammatory cytokines, IL-6 and IL-12. In agreement, maintaining normal TSP1 expression in the UVB-irradiated skin of WT mice using topical apigenin application caused a marked decrease of circulating inflammatory cytokines. Finally, TKO mice showed an altered population dynamics of the bone marrow myeloid progenitor cells (CD11b+), with dramatic expansion of the population of neutrophil progenitors (Ly6ClowLy6Ghigh) compared to the WT control. Our results indicate that the cutaneous tumor suppressor TSP1 is a critical mediator of the in vivo anticancer effect of apigenin in skin, specifically of its anti-inflammatory action.

ERβ regulation of NF-kB activation in prostate cancer is mediated by HIF-1

We examined the regulation of NF-κB in prostate cancer by estrogen receptor β (ERβ) based on the inverse correlation between p65 and ERβ expression that exists in prostate carcinomas and reports that ERβ can inhibit NF-κB activation, although the mechanism is not known. We demonstrate that ERβ functions as a gate-keeper for NF-κB p65 signaling by repressing its expression and nuclear translocation. ERβ regulation of NF-κB signaling is mediated by HIF-1. Loss of ERβ or hypoxia stabilizes HIF-1α, which we found to be a direct driver of IKKβ transcription through a hypoxia response element present in the promoter of the IKKβ gene. The increase of IKKβ expression in ERβ-ablated cells correlates with an increase in phospho-IκBα and concomitant p65 nuclear translocation. An inverse correlation between the expression of ERβ and IKKβ/p65 was also observed in the prostates of ERβ knockout (BERKO) mice, Gleason grade 5 prostate tumors and analysis of prostate cancer databases. These findings provide a novel mechanism for how ERβ prevents NF-κB activation and raise the exciting possibility that loss of ERβ expression is linked to chronic inflammation in the prostate, which contributes to the development of high-grade prostate cancer.

Significance of Rumex vesicarius as anticancer remedy against hepatocellular carcinoma: a proposal-based on experimental animal studies

Rumex vesicarius is an edible herb distributed in Egypt and Saudi Arabia. The whole plant has significant value in folk medicine and it has been used to alleviate several diseases. Hepatocellular carcinoma (HCC), the major primary malignant tumor of the liver, is one of the most life-threatening human cancers. The goal of the current study was to explore the potent role of Rumex vesicarius extract against HCC induced in rats. Thirty adult male albino rats were divided into 3 groups: (I): Healthy animals received orally 0.9% normal saline and served as negative control group, (II): HCC group in which rats were orally administered N-nitrosodiethylamine NDEA, (III): HCC group treated orally with R. vesicarius extract in a dose of 400 mg/kg b.wt daily for two months. ALT and AST, ALP and γ-GT activities were estimated. CEA, AFP, AFU, GPC-3, Gp-73 and VEGF levels were quantified. Histopathological examination of liver tissue sections was also carried out. The results of the current study showed that the treatment of the HCC group with R. vesicarius extract reversed the significant increase in liver enzymes activity, CEA, AFP, AFU, glypican 3, golgi 73 and VEGF levels in serum as compared to HCC-untreated counterparts. In addition, the favorable impact of R. vesicarius treatment was evidenced by the marked improvement in the histopathological features of the liver of the treated group. In conclusion, the present experimental setting provided evidence for the significance of R. vesicarius as anticancer candidate with a promising anticancer potential against HCC. The powerful hepatoprotective properties, the potent antiangiogenic activity and the effective antiproliferative capacity are responsible for the anticancer effect of this plant.

Inhibition of mTOR by apigenin in UVB-irradiated keratinocytes: A new implication of skin cancer prevention

Ultraviolet B (UVB) radiation is the major environmental risk factor for developing skin cancer, the most common cancer worldwide, which is characterized by aberrant activation of Akt/mTOR (mammalian target of rapamycin). Importantly, the link between UV irradiation and mTOR signaling has not been fully established. Apigenin is a naturally occurring flavonoid that has been shown to inhibit UV-induced skin cancer. Previously, we have demonstrated that apigenin activates AMP-activated protein kinase (AMPK), which leads to suppression of basal mTOR activity in cultured keratinocytes. Here, we demonstrated that apigenin inhibited UVB-induced mTOR activation, cell proliferation and cell cycle progression in mouse skin and in mouse epidermal keratinocytes. Interestingly, UVB induced mTOR signaling via PI3K/Akt pathway, however, the inhibition of UVB-induced mTOR signaling by apigenin was not Akt-dependent. Instead, it was driven by AMPK activation. In addition, mTOR inhibition by apigenin in keratinocytes enhanced autophagy, which was responsible, at least in part, for the decreased proliferation in keratinocytes. In contrast, apigenin did not alter UVB-induced apoptosis. Taken together, our results indicate the important role of mTOR inhibition in UVB protection by apigenin, and provide a new target and strategy for better prevention of UV-induced skin cancer.

Sulforaphane inhibits hypoxia-induced HIF-1α and VEGF expression and migration of human colon cancer cells

The effects of sulforaphane (a natural product commonly found in broccoli) was investigated on hypoxia inducible factor-1α (HIF-1α) expression in HCT116 human colon cancer cells and AGS human gastric cancer cells. We found that hypoxia-induced HIF-1α protein expression in HCT116 and AGS cells, while treatment with sulforaphane markedly and concentration-dependently inhibited HIF-1α expression in both cell lines. Treatment with sulforaphane inhibited hypoxia-induced vascular endothelial growth factor (VEGF) expression in HCT116 cells. Treatment with sulforaphane modulated the effect of hypoxia on HIF-1α stability. However, degradation of HIF-1α by sulforaphane was not mediated through the 26S proteasome pathway. We also found that the inhibition of HIF-1α by sulforaphane was not mediated through AKT and extracellular signal-regulated kinase phosphorylation under hypoxic conditions. Finally, hypoxia-induced HCT116 cell migration was inhibited by sulforaphane. These data suggest that sulforaphane may inhibit human colon cancer progression and cancer cell angiogenesis by inhibiting HIF-1α and VEGF expression. Taken together, these results indicate that sulforaphane is a new and potent chemopreventive drug candidate for treating patients with human colon cancer.

Hypoxia-induced autophagy promotes human prostate stromal cells survival and ER-stress

Benign prostatic hyperplasia (BPH) is emerging as one of the most common diseases seriously threatening the health of elderly men. Accumulating evidences indicate that hypoxia could induce BPH. However, the underlying mechanism of BPH induced by hypoxia is not clear. In the study, hypoxia-induced autophagy could promote cell survival and endoplasmic reticula stress (ER stress) in WPMY-1 cells. Cell viability induced by hypoxia could been decreased by autophagy inhibitors (3-methyladenine, bafilomycin A1) or siRNA interference in two autophagy genes (Beclin1, ATG5) in WPMY-1 cells. Furthermore, ER stress was present in hypoxia-treated WPMY-1 cells, while autophagy and cell survival could been inhibited by C/EBP-homologous protein siRNA (CHOP), which is an important protein of ER stress pathway. Taken together, our data support a novel model that autophagy as a cytoprotective response promotes cell survival via ER stress under hypoxia in human prostate stromal cells.

The tyrosine phosphatase SHP-1 regulates hypoxia inducible factor-1α (HIF-1α) protein levels in endothelial cells under hypoxia

Introduction

The tyrosine phosphatase SHP-1 negatively influences endothelial function, such as VEGF signaling and reactive oxygen species (ROS) formation, and has been shown to influence angiogenesis during tissue ischemia. In ischemic tissues, hypoxia induced angiogenesis is crucial for restoring oxygen supply. However, the exact mechanism how SHP-1 affects endothelial function during ischemia or hypoxia remains unclear. We performed in vitro endothelial cell culture experiments to characterize the role of SHP-1 during hypoxia.

Results

SHP-1 knock-down by specific antisense oligodesoxynucleotides (AS-Odn) increased cell growth as well as VEGF synthesis and secretion during 24 hours of hypoxia compared to control AS-Odn. This was prevented by HIF-1α inhibition (echinomycin and apigenin). SHP-1 knock-down as well as overexpression of a catalytically inactive SHP-1 (SHP-1 CS) further enhanced HIF-1α protein levels, whereas overexpression of a constitutively active SHP-1 (SHP-1 E74A) resulted in decreased HIF-1α levels during hypoxia, compared to wildtype SHP-1. Proteasome inhibition (MG132) returned HIF-1α levels to control or wildtype levels respectively in these cells. SHP-1 silencing did not alter HIF-1α mRNA levels. Finally, under hypoxic conditions SHP-1 knock-down enhanced intracellular endothelial reactive oxygen species (ROS) formation, as measured by oxidation of H₂-DCF and DHE fluorescence.

Conclusions

SHP-1 decreases half-life of HIF-1α under hypoxic conditions resulting in decreased cell growth due to diminished VEGF synthesis and secretion. The regulatory effect of SHP-1 on HIF-1α stability may be mediated by inhibition of endothelial ROS formation stabilizing HIF-1α protein. These findings highlight the importance of SHP-1 in hypoxic signaling and its potential as therapeutic target in ischemic diseases.

Inhibition of IL-6/STAT3 axis and targeting Axl and Tyro3 receptor tyrosine kinases by apigenin circumvent taxol resistance in ovarian cancer cells

Ovarian cancer is the number one cause of death from gynaecological malignancy. Platinum-based and taxol-based chemotherapy has been used as a standard therapy, but intrinsic and acquired resistance to chemotherapy is a major obstacle to treat the disease. In the present study, we found that in the chemoresistant ovarian cancer SKOV3/TR cells, interleukin-6 (IL-6), IL-6 receptor and signal transducers and activators of transcription 3 (STAT3) expression as well as STAT3 phosphorylation were upregulated compared to those in parental cells. Silencing of IL-6 using IL-6 siRNA was found to suppress IL-6 production, STAT3 and phosphoSTAT3 levels, which eventually reduced proliferation and clonogenicity of taxol-resistant SKOV3/TR cells. In addition, stattic, a STAT3 inhibitor, was found to result in decrease of cell viability and clonogenicity of these cells, indicating that the elevated IL-6 and STAT3, phosphoSTAT3 levels are associated with the development of taxol resistance. Next, we found anti-proliferative effect of apigenin on both SKOV3 and SKOV3/TR cells. RT-PCR and western blot results showed that apigenin significantly reduced the expression of Axl and Tyro3 receptor tyrosine kinases (RTKs) at mRNA and protein level, which account for its cytotoxic activity. We further found that apigenin decreased Akt phosphorylation and the level of B-cell lymphoma-extra large (Bcl-xl or BCL2-like 1 isoform 1), an inhibitor of apoptosis. On the contrary to these results, apigenin had no effect on IL-6 production, STAT3 and phosphoSTAT3 protein levels, suggesting that apigenin exerts its anti-proliferative activity via downregulation of Axl and Tyro3 expression, Akt phosphorylation and Bcl-xl expression, but not modulation of IL-6/STAT3 axis. Taken together, our data suggest that inhibition of IL-6/STAT3 signaling pathway and downregulation of Axl and Tyro3 RTKs expression might be a therapeutic strategy to overcome taxol resistance in ovarian cancer cells.

Chemopreventive apigenin controls UVB-induced cutaneous proliferation and angiogenesis through HuR and thrombospondin-1

Plant flavonoid apigenin prevents and inhibits UVB-induced carcinogenesis in the skin and has strong anti-proliferative and anti-angiogenic properties. Here we identify mechanisms, by which apigenin controls these oncogenic events. We show that apigenin acts, at least in part, via endogenous angiogenesis inhibitor, thrombospondin-1 (TSP1). TSP1 expression by the epidermal keratinocytes is potently inhibited by UVB. It inhibits cutaneous angiogenesis and UVB-induced carcinogenesis. We show that apigenin restores TSP1 in epidermal keratinocytes subjected to UVB and normalizes proliferation and angiogenesis in UVB-exposed skin. Importantly, reconstituting TSP1 anti-angiogenic function in UVB-irradiated skin with a short bioactive peptide mimetic representing exclusively its anti-angiogenic domain reproduced the anti-proliferative and anti-angiogenic effects of apigenin. Cox-2 and HIF-1α are important mediators of angiogenesis. Both apigenin and TSP1 peptide mimetic attenuated their induction by UVB. Finally we identified the molecular mechanism, whereby apigenin did not affect TSP1 mRNA, but increased de novo protein synthesis. Knockdown studies implicated the RNA-binding protein HuR, which controls mRNA stability and translation. Apigenin increased HuR cytoplasmic localization and physical association with TSP1 mRNA causing de novo TSP1 synthesis. HuR cytoplasmic localization was, in turn, dependent on CHK2 kinase. Together, our data provide a new mechanism, by which apigenin controls UVB-induced carcinogenesis.

Apigenin induces apoptosis by targeting inhibitor of apoptosis proteins and Ku70-Bax interaction in prostate cancer

Dysfunction of the apoptotic pathway in prostate cancer cells confers apoptosis resistance towards various therapies. A novel strategy to overcome resistance is to directly target the apoptotic pathway in cancer cells. Apigenin, an anticancer agent, selectively toxic to cancer cells induces cell cycle arrest and apoptosis through mechanisms which are not fully explored. In the present study we provide novel insight into the mechanisms of apoptosis induction by apigenin. Treatment of androgen-refractory human prostate cancer PC-3 and DU145 cells with apigenin resulted in dose-dependent suppression of XIAP, c-IAP1, c-IAP2 and survivin protein levels. Apigenin treatment resulted in significant decrease in cell viability and apoptosis induction with the increase of cytochrome C in time-dependent manner. These effects of apigenin were accompanied by decrease in Bcl-xL and Bcl-2 and increase in the active form of Bax protein. The apigenin-mediated increase in Bax was due to dissociation of Bax from Ku70 which is essential for apoptotic activity of Bax. Apigenin treatment resulted in the inhibition of class I histone deacetylases and HDAC1 protein expression, thereby increasing the acetylation of Ku70 and the dissociation of Bax resulting in apoptosis of cancer cells. Furthermore, apigenin significantly reduced HDAC1 occupancy at the XIAP promoter, suggesting that histone deacetylation might be critical for XIAP downregulation. These results suggest that apigenin targets inhibitor of apoptosis proteins and Ku70-Bax interaction in the induction of apoptosis in prostate cancer cells and in athymic nude mouse xenograft model endorsing its in vivo efficacy.

Axl receptor tyrosine kinase is a novel target of apigenin for the inhibition of cell proliferation

The Axl receptor tyrosine kinase (RTK), along with Tyro 3 and Mer, belongs to the TAM subfamily that promotes survival, stimulates proliferation and/or inhibits apoptosis. In various types of human cancer, including breast, lung and prostate cancer, Axl expression is increased and correlates with an advanced clinical stage. In this study, we examined whether apigenin has an effect on Axl expression, which in turn can affect cell proliferation. The treatment of the non‑small cell lung cancer (NSCLC) cells, A549 and H460, with apigenin decreased Axl mRNA and protein expression in a dose‑dependent manner. Axl promoter activity was also inhibited by apigenin, indicating that apigenin suppressed Axl expression at the transcriptional level. Upon treatment with apigenin, the viability of both the A549 and H460 cells was gradually decreased and the anti-proliferative effects were further confirmed by the dose‑dependent decrease in the clonogenic ability of the apigenin‑treated cells. Subsequently, we found that the viability and clonogenic ability of the cells treated with apigenin was less or more affected by transfection of the cells with a Axl-expressing plasmid or Axl targeting siRNA, compared to transfection with the empty vector or control siRNA, respectively. In addition, apigenin increased the expression of p21, a cyclin-dependent kinase inhibitor, but reduced the expression of X-linked inhibitor of apoptosis protein (XIAP). These cell cycle arrest and pro-apoptotic effects of apigenin were also attenuated or augmented by the up- or downregulation of Axl expression, respectively, which suggests that Axl is a novel target of apigenin through which it exerts its inhibitory effects on cell proliferation. Taken together, our data indicate that apigenin downregulates Axl expression, which subsequently results in the inhibition of NSCLC cell proliferation through the increase and decrease of p21 and XIAP expression, respectively.

Gambogic acid suppresses hypoxia-induced hypoxia-inducible factor-1α/vascular endothelial growth factor expression via inhibiting phosphatidylinositol 3-kinase/Akt/mammalian target protein of rapamycin pathway in multiple myeloma cells

In multiple myeloma (MM), the hypoxic environment is an important factor causing tumor angiogenesis, which is strongly correlated to disease progression and unfavorable outcome by activating the key transcription factor, hypoxia-inducible factor-1α (HIF-1α). Gambogic acid (GA) is the major active ingredient of gamboge, which has been shown to possess antitumor effect by in vitro and in vivo study. However, the underlying molecular mechanism of whether GA inhibits tumor angiogenesis remains poorly understood. In this study, we investigated the effects of GA on expression of HIF-1α, and its downstream target gene vascular endothelial growth factor (VEGF) in human MM U266 cells. We found that hypoxia induced increase in the level of HIF-1α subunit protein and activated the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target protein of rapamycin (mTOR) pathway. Moreover, the treatment with GA markedly decreased HIF-1α and VEGF expression under hypoxic conditions. Mechanistic studies exhibited that GA inhibited the production of HIF-1α by reducing phosphorylation of Akt and mTOR in U266 cells. Furthermore, in vivo study revealed that intravenous injection of GA once every other day for 2 weeks could suppress tumor volumes by antiangiogenesis activity. Taken together, our results identify that GA suppresses hypoxia-activated pathways that are linked to MM progression, at least partly, by the inhibition of the PI3K/Akt/mTOR signaling pathway. Therefore, GA may be a new potent therapeutic agent against human MM cells.

Apigenin-induced apoptosis is enhanced by inhibition of autophagy formation in HCT116 human colon cancer cells

Apigenin (4',5,7-trihydroxyflavone) is a natural flavonoid, shown to have chemopreventive and/or anticancer properties in a variety of human cancer cells. The involvement of autophagy in apigenin-induced apoptotic cell death of HCT116 human colon cancer cells was investigated. Apigenin induced suppression of cell growth in a concentration-dependent manner in HCT116 cells. Flow cytometric analyses indicated that apigenin resulted in G2/M phase arrest. This flavone also suppressed the expression of both cyclin B1 and its activating partners, Cdc2 and Cdc25c, whereas the expression of cell cycle inhibitors, such as p53 and p53-dependent p21(CIP1/WAF1), was increased after apigenin treatment. Apigenin induced poly (ADP-ribose) polymerase (PARP) cleavage and decreased the levels of procaspase-8, -9 and -3. In addition, the apigenin-treated cells exhibited autophagy, as characterized by the appearance of autophagosomes under fluorescence microscopy and the accumulation of acidic vesicular organelles by flow cytometry. Furthermore, the results of the western blot analysis revealed that the levels of LC3-II, the processed form of LC3-I, was increased by apigenin. Treatment with the autophagy inhibitor 3-methyladenine (3-MA) significantly enhanced the apoptosis induced by apigenin, which was accompanied by an increase in the levels of PARP cleavage. These results indicate that apigenin has apoptosis- and autophagy-inducing effects in HCT116 colon cancer cells. Autophagy plays a cytoprotective role in apigenin-induced apoptosis, and the combination of apigenin and an autophagy inhibitor may be a promising strategy for colon cancer control.

Methylseleninic acid elevates REDD1 and inhibits prostate cancer cell growth despite AKT activation and mTOR dysregulation in hypoxia

Methylseleninic acid (MSeA) is a monomethylated selenium metabolite theoretically derived from subsequent β-lyase or transamination reactions of dietary Se-methylselenocysteine that has potent antitumor activity by inhibiting cell proliferation of several cancers. Our previous studies showed that MSeA promotes apoptosis in invasive prostate cancer cells in part by downregulating hypoxia-inducible factor HIF-1α. We have now extended these studies to evaluate the impact of MSeA on REDD1 (an mTOR inhibitor) in inducing cell death of invasive prostate cancer cells in hypoxia. In both PTEN+ and PTEN− prostate cancer cells we show that MSeA elevates REDD1 and phosphorylation of AKT along with p70S6K in hypoxia. Furthermore, REDD1 induction by MSeA is independent of AKT and the mTOR inhibition in prostate cancer cells causes partial resistance to MSeA-induced growth reduction in hypoxia. Our data suggest that MSeA induces REDD1 and inhibits prostate cancer cell growth in hypoxia despite activation of AKT and dysregulation of mTOR.

MSeA elevates REDD1 and AKT to promote cell death in invasive prostate cancer cells in hypoxia.

Subtoxic Levels of Apigenin Inhibit Expression and Secretion of VEGF by Uveal Melanoma Cells via Suppression of ERK1/2 and PI3K/Akt Pathways

The effects of apigenin on the expression of VEGF in uveal melanoma cells have not been reported. We studied this effect and relevant signaling pathways in two human uveal melanoma cell lines (SP6.5 and C918). ELISA assay revealed that the constitutive secretion of VEGF by uveal melanoma cells was 21-fold higher than that in normal uveal melanocytes. Apigenin at subtoxic levels (1-5  μ M) significantly suppressed the secretion of VEGF in a dose- and time-dependent manner in melanoma cells. VEGF levels in the conditioned culture media from SP6.5 and C918 cell lines treated with 5  μ M apigenin for 24 h reduced to 29% and 21% of those in cells not treated with apigenin, respectively. RT-PCR analysis found that apigenin also decreased the expression of VEGF mRNA in melanoma cells. ELISA study of various signal pathways showed that apigenin significantly decreased phosphorylated Akt and ERK1/2 but increased phosphorylated JNK1/2 and p38 MAPK levels in melanoma cells. PI3K/Akt or ERK1/2 inhibitors significantly decreased, but JNK1/2 and p38 MAPK inhibitors did not influence the secretion of VEGF by melanoma cells, suggesting that apigenin suppresses the secretion of VEGF mainly through the inhibition of PI3K/Akt and ERK1/2 pathways.

A novel resveratrol analogue, HS-1793, inhibits hypoxia-induced HIF-1α and VEGF expression, and migration in human prostate cancer cells

In many studies, resveratrol has been shown to have a chemopreventive effect in various types of cancer cells. However, the biological activity of resveratrol is limited by its photosensitivity and metabolic instability. This study investigated the effects of a novel analogue of resveratrol, HS-1793, on the expression of HIF-1α and vascular endothelial growth factor (VEGF) in PC-3 human prostate cancer cells. Hypoxic condition induced HIF-1α protein level in PC-3 cells in a time-dependent manner, and treatment with HS-1793 markedly decreased HIF-1α expression levels. HS-1793 also inhibited VEGF level. Mechanistically, HS-1793 inhibited HIF-1α and VEGF expression through multiple mechanisms. Firstly, HS-1793 inhibited phosphorylation of PI3K and Akt in PC-3 cells. Furthermore, HS-1793 substantially induced HIF-1α protein degradation through the proteasome pathway. Finally, HS-1793 inhibited hypoxia-induced PC-3 cell migration. These data suggest that HS-1793 may inhibit human prostate cancer progression and angiogenesis by inhibiting the expression of HIF-1α and VEGF. Moreover, HS-1793 showed more potent effects than resveratrol on the cytotoxic effects on PC-3 cells. Taken together, these results implied that HS-1793, a novel analogue of resveratrol, may be a new potent chemopreventive agent against human prostate cancer cells.