Synergic effect of α-tocopherol and naringenin in transglutaminase-induced differentiation of human prostate cancer cells

STAT3 signaling in prostate cancer progression and therapy resistance: An oncogenic pathway with diverse functions

The categorization of cancers demonstrates that prostate cancer is the most common malignancy in men and it causes high death annually. Prostate cancer patients are diagnosed mainly via biomarkers such as PSA test and patients show poor prognosis. Prostate cancer cells rapidly diffuse into different parts of body and their metastasis is also a reason for death. Current therapies for prostate cancer patients include chemotherapy, surgery and radiotherapy as well as targeted therapy. The progression of prostate cancer cells is regulated by different factors that STAT3 signaling is among them. Growth factors and cytokines such as IL-6 can induce STAT3 signaling and it shows carcinogenic impact. Activation of STAT3 signaling occurs in prostate cancer and it promotes malignant behavior of tumor cells. Induction of STAT3 signaling increases glycolysis and proliferation of prostate cancer cells and prevents apoptosis. Furthermore, STAT3 signaling induces EMT mechanism in increasing cancer metastasis. Activation of STAT3 signaling stimulates drug resistance and the limitation of current works is lack of experiment related to role of STAT3 signaling in radio-resistance in prostate tumor. Calcitriol, capsazepine and β-elemonic are among the compounds capable of targeting STAT3 signaling and its inhibition in prostate cancer therapy. In addition to natural products, small molecules targeting STAT3 signaling have been developed in prostate cancer therapy.

In Vitro Combination of Ascorbic and Ellagic Acids in Sperm Oxidative Damage Inhibition

It is known that an altered redox balance interferes with normal spermatic functions. Exposure to genotoxic substances capable of producing oxidative stress (OS) can cause infertility in humans. The use of antioxidants to reduce oxidative stress contributes to the improvement in reproductive function. This study focused on an antigenotoxic evaluation of ellagic acid (EA) and ascorbic acid (AA) in combination against benzene genotoxic action on human spermatozoa in vitro. In addition to the evaluation of sperm parameters, damage in sperm genetic material and intracellular ROS quantification were assessed after AA, EA and benzene co-exposure using the TUNEL technique and DCF assay. The results showed that the combination of the two antioxidants generates a greater time-dependent antigenotoxic action, reducing both the sperm DNA fragmentation index and the oxidative stress. The genoprotective effect of AA and EA association in sperm cells lays the foundations for a more in-depth clinical study on the use of antioxidants as a therapy for male infertility.

DNA Damage in Human Amniotic Cells: Antigenotoxic Potential of Curcumin and α-Lipoic Acid

Oxidative imbalances in the gestational phase are responsible for certain complications during pregnancy and for foetal and neonatal genetic disorders. In this work, using human amniocytes, we aimed to evaluate the protection provided to foetal DNA by two concentrations of antioxidant molecules, α-lipoic acid (LA) and curcumin (Cur), against hydrogen peroxide (H₂O₂)-induced damage. Genotoxicity tests, performed by the random amplification of polymorphic DNA (RAPD-PCR) technique and TUNEL tests, showed that the lowest concentration of LA-protected cells and DNA from H₂O₂ insults. However, a greater ability to protect the amniocytes’ DNA against H₂O₂ was observed following co-treatment with the highest concentration of Cur with H₂O₂. In fact, a genomic template stability (GTS%) similar to that of the negative control and a statistically significant reduction in the DNA fragmentation index (DFI) were revealed. Moreover, following a combined treatment with both antioxidants and H₂O₂, no statistical difference from controls was observed, in terms of both induced mutations and DNA breaks. Furthermore, no effect on morphology or cell viability was observed. The results demonstrate the ability of LA and Cur to protect the genetic material of amniocytes against genotoxic insults, suggesting their beneficial effects in pathologies related to oxidative stress.

Prostate cancer: Therapeutic prospect with herbal medicine

Prostate cancer (PCa) is a major cause of morbidity and mortality in men worldwide. A geographic variation on the burden of the disease suggested that the environment, genetic makeup, lifestyle, and food habits modulate one's susceptibility to the disease. Although it has been generally thought to be an older age disease, and awareness and timely execution of screening programs have managed to contain the disease in the older population over the last decades, the incidence is still increasing in the population younger than 50. Existing treatment is efficient for PCa that is localized and responsive to androgen. However, the androgen resistant and metastatic PCa are challenging to treat. Conventional radiation and chemotherapies are associated with severe side effects in addition to being exorbitantly expensive. Many isolated phytochemicals and extracts of plants used in traditional medicine are known for their safety and diverse healing properties, including many with varying levels of anti-PCa activities. Many of the phytochemicals discussed here, as shown by many laboratories, inhibit tumor cell growth and proliferation by interfering with the components in the pathways responsible for the enhanced proliferation, metabolism, angiogenesis, invasion, and metastasis in the prostate cells while upregulating the mechanisms of cell death and cell cycle arrest. Notably, many of these agents simultaneously target multiple cellular pathways. We analyzed the available literature and provided an update on this issue in this review article.

Research Progress in Flavonoids as Potential Anticancer Drug Including Synergy with Other Approaches

BACKGROUND

In chemotherapy for cancer, conventional drugs aim to target the rapidly growing and dividing cells at the early stages. However, at an advanced stage, cancer cells become less susceptible because of the multidrug resistance and the recruitment of alternative salvage pathways for their survival. Besides, owing to target non-selectivity, healthy proliferating cells also become vulnerable to the damage. The combination therapies offered using flavonoids to cure cancer not only exert an additive effect against cancer cells by targetting supplementary cell carnage pathways but also hampers the drug resistance mechanisms. Thus, the review aims to discuss the potential and pharmacokinetic limitations of flavonoids in cancer treatment. Further successful synergistic studies reported using flavonoids to treat cancer has been described along with potential drug delivery systems.

METHODS

A literature search was done by exploring various online databases like Pubmed, Scopus, and Google Scholar with the specific keywords like "Anticancer drugs", "flavonoids", "oncology research", and "pharmacokinetics".

RESULTS

Dietary phytochemicals, mainly flavonoids, hinder cell signalling responsible for multidrug resistance and cancer progression, primarily targeting cancer cells sparing normal cells. Such properties establish flavonoids as a potential candidate for synergistic therapy. However, due to low absorption and high metabolism rates, the bioavailability of flavonoids becomes a challenge. Such challenges may be overcome using novel approaches like derivatization, and single or co-delivery nano-complexes of flavonoids with conventional drugs. These new approaches may improve the pharmacokinetic and pharmacodynamic of flavonoids.

CONCLUSION

This review highlights the application of flavonoids as a potential anticancer phytochemical class in combination with known anti-cancer drugs/nanoparticles. It also discusses flavonoid's pharmacokinetics and pharmacodynamics issues and ways to overcome such issues. Moreover, it covers successful methodologies employed to establish flavonoids as a safe and effective phytochemical class for cancer treatment.

Reduction of oxidative stress and ornithine decarboxylase expression in a human prostate cancer cell line PC-3 by a combined treatment with α-tocopherol and naringenin

Differentiation of a human aggressive PC-3 cancer cell line was obtained, in a previous investigation, by the synergic effect of α-tocopherol (α-TOC) and naringenin (NG). This combined treatment induced apoptosis and subsequent reduction of the PC-3 cell proliferation and invasion, by a pro-differentiating action. Since one of the peculiar characteristics of NG and α-TOC is their strong antioxidant activity, this study aimed to investigate their potential effect on the activity of the main enzymes involved in the antioxidant mechanism in prostate cancer cells. NG and α-TOC administered singularly or combined in the PC-3 cell line, affected the activity of several enzymes biomarkers of the cellular antioxidant activity, as well as the concentration of total glutathione (GSH + GSSG) and thiobarbituric acid reactive substances (TBARS). The combined treatment increased the TBARS levels and superoxide dismutase (SOD) activity, while decreased the glutathione S-transferase (GST), glutathione reductase (GR), and glyoxalase I (GI) activities. The results obtained indicate that a combined treatment with these natural compounds mitigated the oxidative stress in the human PC-3 cell line. In addition, a significant reduction of both ornithine decarboxylase (ODC) expression and intracellular levels of polyamines, both well-known positive regulators of cell proliferation, accompanied the reduction of oxidative stress observed in the combined α-TOC and NG treatment. Considering the established role of polyamines in cell differentiation, the synergism with NG makes α-TOC a potential drug for further study on the differentiation therapy in prostate cancer patients.

Naringin and naringenin as anticancer agents and adjuvants in cancer combination therapy: Efficacy and molecular mechanisms of action, a comprehensive narrative review

Although the rates of many cancers are controlled in Western countries, those of some cancers, such as lung, breast, and colorectal cancer are currently increasing in many low- and middle-income countries due to increases in risk factors caused by development and societal problems. Additionally, endogenous factors, such as inherited mutations, steroid hormones, insulin, and insulin-like growth factor systems, inflammation, oxidative stress, and exogenous factors (including tobacco, alcohol, infectious agents, and radiation), are believed to compromise cell functions and lead to carcinogenesis. Chemotherapy, surgery, radiation therapy, hormone therapy, and targeted therapies are some examples of the approaches used for cancer treatment. However, various short- and long-term side effects can also considerably impact patient prognosis based on clinical factors associated with treatments. Recently, increasing numbers of studies have been conducted to identify novel therapeutic agents from natural products, among which plant-derived bioactive compounds have been increasingly studied. Naringin (NG) and its aglycone naringenin (NGE) are abundantly present in citrus fruits, such as grapefruits and oranges. Their anti-carcinogenic activities have been shown to be exerted through several cell signal transduction pathways. Recently, different pharmacological strategies based on combination therapy, involving NG and NGE with the current anti-cancer agents have shown prodigious synergistic effects when compared to monotherapy. Besides, NG and NGE have been reported to overcome multidrug resistance, resulting from different defensive mechanisms in cancer, which is one of the major obstacles of clinical treatment. Thus, we comprehensively reviewed the inhibitory effects of NG and NGE on several types of cancers through different signal transduction pathways, the roles on sensitizing with the current anticancer medicines, and the efficacy of the cancer combination therapy.

Naringenin as a potential immunomodulator in therapeutics

Naringenin, a citrus flavonoid that possesses various biological activities, has emerged as a potential therapeutic agent for the management of a variety of diseases. Studies using cell culture system have shown that naringenin can inhibit inflammatory response in diverse cell types. Moreover, research using various animal models has further demonstrated therapeutic potentials of naringenin in the treatment of several inflammation-related disorders, such as sepsis, fulminant hepatitis, fibrosis and cancer. The mechanism of action of naringenin is not completely understood but recent mechanistic studies revealed that naringenin suppresses inflammatory cytokine production through both transcriptional and post-transcriptional mechanisms. Surprisingly, naringenin not only inhibits cytokine mRNA expression but also promotes lysosome-dependent cytokine protein degradation. This unique property of naringenin stands in sharp contrast with some widely-studied natural products such as apigenin and curcumin, which regulate cytokine production essentially at the transcriptional level. Therefore, naringenin may provide modality for the development of novel anti-inflammatory agent. This review article summarizes our recent studies in understanding how naringenin acts in cells and animal models. Particularly, we will discuss the anti-inflammatory activities of naringenin in various disease context and its potential use, as an immunomodulator, in the treatment of inflammatory related disease.

Naringenin-Induced Apoptotic Cell Death in Prostate Cancer Cells Is Mediated via the PI3K/AKT and MAPK Signaling Pathways

Prostate cancer is the most common cancer in men and the second most common cause of cancer-related deaths in men. Although, various drugs targeting the androgen receptor are normally used, the patients frequently undergo recurrence of the disease. To overcome these limitations, natural compounds have been researched for evidence that they suppress progression and metastasis of various cancer cells. In the present study, we investigated effects of naringenin, a natural anti-oxidant flavonoid derived from citrus, on prostate cancer cells (PC3 and LNCaP). Results of present study with PC3 and LNCaP cells revealed that naringenin inhibited proliferation and migration, while inducing apoptosis and ROS production by those cells. In addition, naringenin-induced loss of mitochondrial membrane potential and increased Bax and decreased Bcl-2 proteins in PC3 cells, but not LNCaP cells. In a dose-dependent manner, naringenin decreased phosphorylation of ERK1/2, P70S6K, S6, and P38 in PC3 cells, and reduced phosphorylation of ERK1/2, P53, P38, and JNK proteins in LNCaP cells. However, naringenin activated phosphorylation of AKT in both PC3 and LNCaP cells. Then, targeted signaling proteins associated with viability of PC3 and LNCaP cells were analyzed using pharmacological inhibitors of AKT and ERK1/2 cell signaling pathways. Moreover, we compared the apoptotic effects of naringenin and paclitaxel alone and in combination to find that naringenin enhanced the efficiency of paclitaxel to suppress progression of prostate cancer cell lines. Collectively, these results indicate that naringenin is a potential chemotherapeutic agent for treatment of prostate cancer. J. Cell. Biochem. 118: 1118-1131, 2017. © 2016 Wiley Periodicals, Inc.

γ-Tocopherol inhibits human prostate cancer cell proliferation by up-regulation of transglutaminase 2 and down-regulation of cyclins

To establish a system to study differentiation therapy drugs, we used the androgen-independent human prostate PC-3 tumor cell line as a target and α- and γ-tocopherol as inducers. Effects of α- and γ-tocopherol on the cell cycle, proliferation and differentiation, were examined. A more significant growth inhibition activity for γ- than for α-tocopherol was observed. Flow cytometry analysis of α- and γ-tocopherol-treated prostate carcinoma PC3 cells showed decreased progression into the S-phase. This effect, particularly evident for γ-tocopherol, was associated with an up-regulation and increased activity of transglutaminase 2 (TG2), a reduced DNA synthesis and a remarkable decreased levels of cyclin D1 and cyclin E. Activation of TG2 suggests that γ-tocopherol has an evident differentiative capacity on PC3 cells, leading to an increased expression of TG2, and reduced cyclin D1 and cyclin E levels, affecting cell cycle progression. It is feasible that up-regulation and activation of TG2, associated with a reduced proliferation, are parts of a large-scale reprogramming that can attenuate the malignant phenotype of PC3 cells in vitro. These data suggest further investigation on the potential use of this γ-form of vitamin E as a differentiative agent, in combination with the common cytotoxic treatments for prostate cancer therapy.

Enhancing the anticancer effect of the histone deacetylase inhibitor by activating transglutaminase

Histone deacetylase (HDAC) inhibitors have shown promising anticancer effects in clinical trials. However, a proportion of patients do not respond to HDAC inhibitor therapy. We have previously demonstrated that tissue transglutaminase (TG2) is one of the genes commonly up-regulated by HDAC inhibitors in vitro and in vivo, and that two structurally distinct TG2 protein isoforms, the full-length (TG2-L) and the short form (TG2-S), exert opposing effects on cell differentiation due to difference in transamidation activity. Here we show that the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) transcriptionally activates the expression of both TG2-L and TG2-S, and that up-regulation of TG2-L renders neuroblastoma cells less sensitive to SAHA-induced cytotoxicity. Combination therapy with SAHA and the transamidation activator Naringenin, a natural product found in citrus fruits, synergistically enhanced transamidation activity and SAHA-induced cytotoxicity in neuroblastoma cells, but not in normal non-malignant cells. In tumour-bearing N-Myc transgenic mice, SAHA and Naringenin synergistically suppressed tumour progression. Taken together, our data demonstrate that SAHA-induced TG2-L over-expression renders cancer cells less sensitive to SAHA therapy, and suggest the addition of Naringenin to SAHA and probably also other HDAC inhibitors in future clinical trials in cancer patients.