Enhancement of p53-mutant human colorectal cancer cells radiosensitivity by flavonoid fisetin. Int J Radiat Oncol Biol Phys. 2010;77:1527-1535. [PMID: 20637980 DOI: 10.1016/j.ijrobp.2010.02.043]

PI3K/AKT/mTOR Targeting in Colorectal Cancer Radiotherapy: A Systematic Review

BACKGROUND

Radioresistance is a major challenge in the treatment of patients with colorectal cancer (CRC) and impairs the efficacy of radiotherapy. The PI3K/AKT/mTOR signaling pathway plays a critical role in CRC and contributes to the development of radioresistance. Accordingly, targeting this signaling pathway may be a promising strategy to improve oncotherapy.

METHODS

We performed a systematic search of Scopus, PubMed, Web of Science, Embase, and Medline databases. We included articles that investigated the effects of PI3K/AKT/mTOR pathway inhibitors on improving the efficacy of radiotherapy.

RESULT

Of the 32 articles included in our review, 27 were preclinical studies and 5 were clinical trials. We examined the effects of various signaling pathway inhibitors in combination with radiotherapy. While the efficacy of these therapies when used alone is limited, their combination is associated with reduced survival, induction of apoptosis, and cell cycle arrest, which may increase radiosensitivity. Despite the limited number of studies, this combination therapy has shown favorable treatment outcomes in patients with CRC.

CONCLUSION

PI3K/AKT/mTOR is a critical signaling pathway for cancer cell survival. By inhibiting this pathway, we can increase the efficacy of radiotherapy. These results provide valuable insights for the further development of research and clinical practice in the treatment of colorectal cancer.

A comprehensive view on the fisetin impact on colorectal cancer in animal models: Focusing on cellular and molecular mechanisms

Flavonoids, including fisetin, have been linked to a reduced risk of colorectal cancer (CRC) and have potential therapeutic applications for the condition. Fisetin, a natural flavonoid found in various fruits and vegetables, has shown promise in managing CRC due to its diverse biological activities. It has been found to influence key cell signaling pathways related to inflammation, angiogenesis, apoptosis, and transcription factors. The results of this study demonstrate that fisetin induces colon cancer cell apoptosis through multiple mechanisms. It impacts the p53 pathway, leading to increased levels of p53 and decreased levels of murine double minute 2, contributing to apoptosis induction. Fisetin also triggers the release of important components in the apoptotic process, such as second mitochondria-derived activator of caspase/direct inhibitor of apoptosis-binding protein with low pI and cytochrome c. Furthermore, fisetin inhibits the cyclooxygenase-2 and wingless-related integration site (Wnt)/epidermal growth factor receptor/nuclear factor kappa B signaling pathways, reducing Wnt target gene expression and hindering colony formation. It achieves this by regulating the activities of cyclin-dependent kinase 2 and cyclin-dependent kinase 4, reducing retinoblastoma protein phosphorylation, decreasing cyclin E levels, and increasing p21 levels, ultimately influencing E2 promoter binding factor 1 and cell division cycle 2 (CDC2) protein levels. Additionally, fisetin exhibits various effects on CRC cells, including inhibiting the phosphorylation of Y-box binding protein 1 and ribosomal S6 kinase, promoting the phosphorylation of extracellular signal-regulated kinase 1/2, and disrupting the repair process of DNA double-strand breaks. Moreover, fisetin serves as an adjunct therapy for the prevention and treatment of phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit α (PIK3CA)-mutant CRC, resulting in a reduction in phosphatidylinositol-3 kinase (PI3K) expression, Ak strain transforming phosphorylation, mTOR activity, and downstream target proteins in CRC cells with a PIK3CA mutation. These findings highlight the multifaceted potential of fisetin in managing CRC and position it as a promising candidate for future therapy development.

Polyphenols in the Prevention and Treatment of Colorectal Cancer: A Systematic Review of Clinical Evidence

Polyphenols are plant metabolites with potential anti-inflammatory and anti-proliferative effects, which may be advantageous for disorders like colorectal cancer (CRC). Despite promising in vitro and in vivo evidence, human clinical trials have yielded mixed results. The present study aimed to evaluate the clinical evidence of polyphenols for CRC prevention or treatment. A systematic review was performed according to PRISMA. Based on a PROSPERO registered protocol (CRD42024560044), online databases (PubMed and COCHRANE) were utilized for the literature search. A total of 100 studies articles were initially identified. After reviewing, 12 studies with a low risk of bias were selected, examining the effect of a variety of compounds. Curcumin demonstrated promise in various trials, mainly decreasing inflammatory cytokines, though results varied, and it did not lower intestinal adenomas or improve outcomes after chemotherapy. Neither epigallocatechin gallate nor artepillin C reduced the incidence of adenomas. Finally, fisetin seemed to improve the inflammatory status of patients under chemotherapy (5-fluorouracil). In summary, although certain polyphenols appear to exert some effect, their role in the prevention or treatment of CRC is inconclusive, and more clinical studies under more controlled conditions are needed.

The Potential Anticancer Potency of Kolaviron on Colorectal Adenocarcinoma (Caco-2) Cells

BACKGROUND

Globally, colorectal cancer (CRC) is categorized as the third type of cancer associated with mortalities. Chemotherapeutic drugs such as cisplatin can be used to treat cancer-affected patients. However, several adverse effects are associated with its application. This motivated the researchers to search for alternatives that are more efficient and have fewer undesirable effects. Kolaviron is a bioflavonoid that has been reported to have antioxidant and anti-inflammatory properties.

AIM

This study aimed to compare the anticancer effects of kolaviron and cisplatin on Caco-2 cells. The IC50 of kolaviron and cisplatin were calculated, and redox status, apoptotic-related proteins and the cell cycle were also examined.

METHODS

Caco-2 cells were treated with kolaviron ( ⅓, and ½ of IC50 dose) and cisplatin (IC50 dose) for 24 h and 48 h. Cell viability was assessed using the MTT protocol. Redox status and apoptotic-related proteins, in addition to the cell cycle, were examined.

RESULTS

The MTT assay showed the IC50 of kolaviron is 9.49 μg/mL, and that of cisplatin is 2.71 μg/ml against Caco-2 cells. Further, both doses of kolaviron significantly increased the leakage of lactate dehydrogenase (LDH), the production of reactive oxygen species (ROS), and lipoperoxidation (LPO), besides decreasing the antioxidant potency of tumor cells as revealed by the diminished reduced glutathione (GSH). At the molecular level, a significant increase in the levels of p53, cytochrome c, Bax, and caspase 3 was recorded, coupled with a decrease in the level of Bcl2, after treating the Caco-2 cells with kolaviron and cisplatin. Furthermore, kolaviron demonstrated asserted more effects on apoptosis and increased cell percentage in the subG1 phase. In addition, a notable decrease in the expression of proliferating cell nuclear antigen (PCNA) and cyclin D1 is associated with an increase in the expression of tumor protein P53 (TP53) in kolaviron-treated Caco-2 cells cancerous cells.

CONCLUSION

Conclusively, these data suggest that kolaviron has a potential antitumor capacity against colorectal cancer via multiple pathways, including enhancement of ROS production, redox status, p53 pathway, and apoptosis. Therefore, this study authenticated the capability of kolaviron as a valuable chemotherapeutic agent.

Fisetin's Promising Antitumor Effects: Uncovering Mechanisms and Targeting for Future Therapies

Background  Cancer remains a critical global health challenge and a leading cause of mortality. Flavonoids found in fruits and vegetables have gained attention for their potential anti-cancer properties. Fisetin, abundantly present in strawberries, apples, onions, and other plant sources, has emerged as a promising candidate for cancer prevention. Epidemiological studies linking a diet rich in these foods to lower cancer risk have sparked extensive research on fisetin's efficacy. Objective  This review aims to comprehensively explore the molecular mechanisms of fisetin's anticancer properties and investigate its potential synergistic effects with other anticancer drugs. Furthermore, the review examines the therapeutic and preventive effects of fisetin against various cancers. Methods  A systematic analysis of the available scientific literature was conducted, including research articles, clinical trials, and review papers related to fisetin's anticancer properties. Reputable databases were searched, and selected studies were critically evaluated to extract essential information on fisetin's mechanisms of action and its interactions with other anticancer drugs. Results  Preclinical trials have demonstrated that fisetin inhibits cancer cell growth through mechanisms such as cell cycle alteration, induction of apoptosis, and activation of the autophagy signaling pathway. Additionally, fisetin reduces reactive oxygen species levels, contributing to its overall anticancer potential. Investigation of its synergistic effects with other anticancer drugs suggests potential for combination therapies. Conclusion  Fisetin, a bioactive flavonoid abundant in fruits and vegetables, exhibits promising anticancer properties through multiple mechanisms of action. Preclinical trials provide a foundation for further exploration in human clinical trials. Understanding fisetin's molecular mechanisms is vital for developing novel, safe, and effective cancer prevention and treatment strategies. The potential synergy with other anticancer drugs opens new avenues for combination therapies, enhancing cancer management approaches and global health outcomes.

Fisetin induces DNA double-strand break and interferes with the repair of radiation-induced damage to radiosensitize triple negative breast cancer cells

Background

Triple-negative breast cancer (TNBC) is associated with aggressiveness and a poor prognosis. Besides surgery, radiotherapy serves as the major treatment modality for TNBC. However, response to radiotherapy is limited in many patients, most likely because of DNA damage response (DDR) signaling mediated radioresistance. Y-box binding protein-1 (YB-1) is a multifunctional protein that regulates the cancer hallmarks among them resisting to radiotherapy-induced cell death. Fisetin, is a plant flavonol of the flavonoid family of plant polyphenols that has anticancer properties, partially through inhibition of p90 ribosomal S6 kinase (RSK)-mediated YB-1 phosphorylation. The combination of fisetin with radiotherapy has not yet been investigated.

Methods

Activation status of the RSK signaling pathway in total cell lysate and in the subcellular fractions was analyzed by Western blotting. Standard clonogenic assay was applied to test post-irradiation cell survival. γH2AX foci assay and 3 color fluorescence in situ hybridization analyses were performed to study frequency of double-strand breaks (DSB) and chromosomal aberrations, respectively. The underlying repair pathways targeted by fisetin were studied in cells expressing genomically integrated reporter constructs for the DSB repair pathways via quantifying the expression of green fluorescence protein by flow cytometry. Flow cytometric quantification of sub-G1 cells and the protein expression of LC3-II were employed to measure apoptosis and autophagy, respectively. Kinase array and phosphoproteomics were performed to study the effect of fisetin on DDR response signaling.

Results

We showed that the effect of fisetin on YB-1 phosphorylation in TNBC cells is comparable to the effect of the RSK pharmacological inhibitors. Similar to ionizing radiation (IR), fisetin induces DSB. Additionally, fisetin impairs repair of IR-induced DSB through suppressing the classical non-homologous end-joining and homologous recombination repair pathways, leading to chromosomal aberration as tested by metaphase analysis. Effect of fisetin on DSB repair was partially dependent on YB-1 expression. Phosphoproteomic analysis revealed that fisetin inhibits DDR signaling, which leads to radiosensitization in TNBC cells, as shown in combination with single dose or fractionated doses irradiation.

Conclusion

Fisetin acts as a DSB-inducing agent and simultaneously inhibits repair of IR-induced DSB. Thus, fisetin may serve as an effective therapeutic strategy to improve TNBC radiotherapy outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02442-x.

Polyphenols: Immunomodulatory and Therapeutic Implication in Colorectal Cancer

Polyphenolic compounds, widely present in fruits, vegetables, and cereals, have potential benefits for human health and are protective agents against the development of chronic/degenerative diseases including cancer. More recently these bioactive molecules have been gaining great interest as anti-inflammatory and immunomodulatory agents, mainly in neoplasia where the pro-inflammatory context might promote carcinogenesis. Colorectal cancer (CRC) is considered a major public healthy issue, a leading cause of cancer mortality and morbidity worldwide. Epidemiological, pre-clinical and clinical investigations have consistently highlighted important relationships between large bowel inflammation, gut microbiota (GM), and colon carcinogenesis. Many experimental studies and clinical evidence suggest that polyphenols have a relevant role in CRC chemoprevention, exhibit cytotoxic capability vs. CRC cells and induce increased sensitization to chemo/radiotherapies. These effects are most likely related to the immunomodulatory properties of polyphenols able to modulate cytokine and chemokine production and activation of immune cells. In this review we summarize recent advancements on immunomodulatory activities of polyphenols and their ability to counteract the inflammatory tumor microenvironment. We focus on potential role of natural polyphenols in increasing the cell sensitivity to colon cancer therapies, highlighting the polyphenol-based combined treatments as innovative immunomodulatory strategies to inhibit the growth of CRC.

Combination of gold nanoparticles with low-LET irradiation: an approach to enhance DNA DSB induction in HT29 colorectal cancer stem-like cells

PURPOSE

High-linear energy transfer (high LET) irradiation has significant cytotoxic effects on different cancerous stem-like cells (CSLCs) such as colorectal CSLCs. A review of the literature has indicated that the presence of gold nanoparticles (GNPs) enables low-LET irradiation to produce highly non-homogeneous dose distributions like high-LET irradiation. The purpose of this study was to evaluate the radioresponsiveness of HT29 colorectal CSLCs under low-LET irradiation (X-ray) and in the presence of GNPs.

METHODS

Radioresponsiveness was evaluated using the ϒ-H2AX foci formation assay, the clonogenic assay, the cell cycle progression assay and analyses of radiobiological parameters.

RESULTS

In the presence of GNPs, the survival fraction of HT29 CSLCs was significantly reduced and caused significant changes in the radiobiological parameters after irradiation. In addition, ϒ-H2AX assay showed that in the presence of GNPs, the persistent DNA double-strand breaks were significantly increased in irradiated HT29 CSLCs. The relative biological effectiveness value of GNPs with X-rays was about 1.6 for HT-29 CSLCs at the 10% of cell survival fraction (D10 level) when compared to X-rays alone.

CONCLUSION

Therefore, the combination of GNPs with X-ray irradiation has the potential to kill HT29 CSLCs greater than the X-ray alone, and may be considered as an alternative for high-LET irradiation.

Radiotherapy Enhancement with Electroporation in Human Intestinal Colon Cancer HT-29 Cells

Background: The efficiency of radiotherapy for tumors can be enhanced with different radiosensitizers. Previous studies have shown that electroporation (EP) can sensitize some cancer cell lines to ionizing radiation (IR). HT-29 is a radiation resistant colorectal cancer cell line, representative of a cancer type which is the second cause of cancer mortalities in developed countries. The present study aimed to evaluate radiosensitizing effects of EP on HT-29 cells in vitro exposed to 6 MV X-ray photon beams. Methods: HT-29 cells were exposed to a 6 MV X-ray photon beam as the control or to a combination of electroporation and irradiation. The response of cells was evaluated by colony formation assay and survival curves. Results: The survival fraction of the HT-29 cells was significantly decreased by electroporation prior to radiotherapy. A single electric pulse increased colorectal HT-29 cancer cell sensitivity to megavoltage radiation by a factor of 1.36. Conclusion: Our findings showed that EP before radiotherapy can significantly enhance tumor cell sensitivity. This combined treatment modality should be assessed for its applicability in clinic settings for employment against radioresistant cancers. However, to facilitate achieving this goal, many different tumors with a broad range of radiosensitivities should be evaluated.

Fisetin and polymeric micelles encapsulating fisetin exhibit potent cytotoxic effects towards ovarian cancer cells

BACKGROUND

The anti-tumor activities of Natural compounds and their derivatives are of great interest to pharmaceutical industries. Fisetin is one of prospective natural compounds in this regard but unfortunately with poor hydrophilicity.

METHODS

The effects of unmodified and modified fisetin in cultured ovarian cancer cells were compared by transmission electronmicroscopy to determine apoptotic bodies, MTT assay to quantitate cell numbers, and fluorescence activated cell sorting analyse of various markers to determine the apoptotic state. In addition, the efficacy of fisetin and fisetin-micelles in vivo was determined by using immunocompromised mice. Apoptosis was measured by established markers using both western blot analysis and immunochemistry. Angiogenesis in a xenograft mouse model carring SKOV3 cells was evaluated by color Doppler ultrasound and immunohistochemistry.

RESULT

Multiple lines of evidence indicated that fisetin and fisetin micelles induce apoptosis in ovarian cancer cells in a dose-dependent manner. Histological analysis, terminal deoxynucleotidyltransferase-mediated nick-end labeling assay, western blot, immunohistochemical detection and microvessel density detection demonstrated that fisetin and fisetin micelles induced increased tumor apoptosis, proliferation suppression and antiangiogenesis activities.

CONCLUSION

As far as we know, the present study is the first time to demonstrate the potency of both fisetin and fisetin micelles inducing apoptosis in ovarian cancer cells. Further studies will be needed to validate the therapeutic potential of fisetin and fisetin micelles in ovarian cancer treatment.

Fisetin: A bioactive phytochemical with potential for cancer prevention and pharmacotherapy

A wide variety of chronic diseases, such as neurodegenerative and cardiovascular disorders, diabetes mellitus, osteoarthtitis, obesity and various cancers, are now being treated with cost effective phytomedicines. Since synthetic medicines are very expensive, concerted efforts are being made in developing and poor countries to discover cost effective medicines for the treatment of non-communicable diseases (NCDs). Understanding the underlying mechanisms of bioactive medicines from natural sources would not only open incipient avenues for the scientific community and pharmaceutical industry to discover new drug molecules for the therapy of NCDs, but also help to garner knowledge for alternative therapeutic approaches for the management of chronic diseases. Fisetin is a polyphenolic molecule of flavonoids class, and belongs to the bioactive phytochemicals that have potential to block multiple signaling pathways associated with NCDs such as cell division, angiogenesis, metastasis, oxidative stress, and inflammation. The emerging evidence suggests that fisetin may be useful for the prevention and management of several types of human malignancies. Efforts are being made to enhance the bioavailability of fisetin after oral administration to prevent and/or treat cancer of the liver, breast, ovary and other organs. The intent of this review is to highlight the in vitro and in vivo activities of fisetin and to provide up-to-date information about the molecular interactions of fisetin with its cellular targets involved in cancer initiation, promotion and progression as well as to focus on strategies underway to increase the bioavailability and reduce the risk of deleterious effects, if any, associated with fisetin administration.

Polyphenols in Colorectal Cancer: Current State of Knowledge including Clinical Trials and Molecular Mechanism of Action

Polyphenols have been reported to have wide spectrum of biological activities including major impact on initiation, promotion, and progression of cancer by modulating different signalling pathways. Colorectal cancer is the second most major cause of mortality and morbidity among females and the third among males. The objective of this review is to describe the activity of a variety of polyphenols in colorectal cancer in clinical trials, preclinical studies, and primary research. The molecular mechanisms of major polyphenols related to their beneficial effects on colorectal cancer are also addressed. Synthetic modifications and other future directions towards exploiting of natural polyphenols against colorectal cancer are discussed in the last section.

The Healthy Effects of Strawberry Polyphenols: Which Strategy behind Antioxidant Capacity?

Current evidence indicates that the consumption of strawberries, a natural source of a wide range of nutritive and bioactive compounds, is associated with the prevention and improvement of chronic-degenerative diseases. Studies involving cells and animals provide evidence on the anti-inflammatory, anticarcinogenic and antiproliferative activity of the strawberry. Epidemiological and clinical studies demonstrate that its acute consumption increases plasma antioxidant capacity, improves circulating inflammatory markers and ameliorates postprandial glycemic response. At the same time, a protracted intake reduces chronic inflammation and improves plasma lipid profile, supporting cardiovascular health, especially in individuals with increased risk for metabolic syndrome. To explain these beneficial effects, much attention has been paid in the past to the antioxidant properties of strawberry polyphenols. However, recent research has shown that their biological and functional activities are related not only to the antioxidant capacity but also to the modulation of many cellular pathways involved in metabolism, survival, proliferation, and antioxidant defenses. The aim of this review is to update and discuss the molecular and cellular mechanisms proposed in recent studies to elucidate the healthy effects of strawberry polyphenols against the most common chronic diseases, such as cancer, cardiovascular diseases, metabolic syndrome, and inflammation.

Potentiality of syringetin for preferential radiosensitization to cancer cells

PURPOSE

To examine the enhancing effects of syringetin on the radiosensitivity of normal and cancer cells, and the related mechanism.

MATERIALS AND METHODS

We used normal human lung and mouse fibroblasts as well as human lung and mouse cancer cells derived from the above normal fibroblasts. Cell radiosensitivity was measured using a colony formation assay. Apoptosis was analyzed with DAPI staining and Western blots. DNA lesions were analyzed with γH2AX immunofluorescent staining.

RESULTS

The colony formation assay showed that syringetin enhanced radiosensitivity more effectively in cancer cells (H1299 and C3H/MCA clone 15) compared with normal cells (HFL-III and C3H/10T1/2). The radiosensitizing effect of syringetin was observed in mutated p53 and wild-type p53-transfected H1299 cells regardless of p53 status. Apoptosis was more frequently observed in X-ray-irradiated H1299 cells combined with syringetin compared with X-ray-only-treated cells. Enhanced apoptosis by syringetin was not observed in HFL-III cells. Western blot analysis showed that X-ray-induced Caspase-3 activation was enhanced by syringetin in H1299 cells. The number of X-ray-induced DNA double-strand breaks (DSB) measured by quantitative analysis of γH2AX foci was the same for H1299 cells treated with X-rays with or without syringetin.

CONCLUSIONS

This study supports the hypothesis that syringetin enhances radiosensitivity more effectively in cancer cells than in normal cells through enhancement of the Caspase-3-mediated apoptosis pathway. Syringetin could be useful in the development of novel efficacious radiosensitizers.

Combining fisetin and ionizing radiation suppresses the growth of mammalian colorectal cancers in xenograft tumor models

Fisetin (3,7,3′,4′-tetrahydroxyflavone), which belongs to the flavonoid group of polyphenols and is found in a wide range of plants, has been reported to exhibit a number of biological activities in human cancer cells, including antioxidant, anti-inflammatory, antiangiogenic, anti-invasive and antiproliferative effects. Although previous in vitro studies have shown that fisetin treatment increases the apoptotic rate and enhances the radiosensitivity of human colorectal cancer cells, the in vivo effects of fisetin on tumor growth remain unclear. In the present study a murine xenograft tumor model was employed to investigate the therapeutic effects of fisetin in combination with radiation on CT-26 colon cancer cells and human HCT116 colorectal cancer cells. This revealed that intratumoral injection of fisetin significantly suppressed the growth of CT-26 tumors compared with the untreated control group, but had little effect on the growth of HCT116 tumors. However, fisetin in combination with 2-Gy radiation enhanced tumor suppressor activity in murine colon and human colorectal xenograft tumors, as compared with 2-Gy fractionated radiation administered alone for 5 days and fisetin alone. Interestingly, fisetin downregulated the expression of the oncoprotein securin in a p53-independent manner. However, securin-null HCT116 tumors showed only moderate sensitivity to fisetin treatment, and the combination of fisetin and radiation did not significantly suppress securin-null HCT116 tumor growth compared with normal HCT116 tumors. Therefore, the role of securin in mediating the effect of fisetin on colorectal cancer growth warrants further investigation. In conclusion, the results of the current study provide important preclinical data for evaluating the efficacy of fisetin and radiation combination treatment as an adjuvant chemoradiotherapy for human colorectal cancers.

Dietary flavonoid fisetin for cancer prevention and treatment

Cancer remains a major public health concern and a significant cause of death worldwide. Identification of bioactive molecules that have the potential to inhibit carcinogenesis continues to garner interest among the scientific community. In particular, flavonoids from dietary sources are the most sought after because of their safety, cost-effectiveness, and feasibility of oral administration. Emerging data have provided newer insights into understanding the molecular mechanisms that are essential to identify novel mechanism-based strategies for cancer prevention and treatment. Dietary flavonoid fisetin (3,3',4',7-tetrahydroxyflavone) found in many fruits and vegetables has been shown in preclinical studies to inhibit cancer growth through alteration of cell cycle, inducing apoptosis, angiogenesis, invasion, and metastasis without causing any toxicity to normal cells. Although data from in-vitro and in-vivo studies look convincing, well-designed clinical trials in humans are needed to conclusively determine the efficacy across various cancers. This review highlights the chemopreventive and therapeutic effects, molecular targets, and mechanisms that contribute to the observed anticancer activity of fisetin against various cancers.

Exploring the molecular targets of dietary flavonoid fisetin in cancer

The last few decades have seen a resurgence of interest among the scientific community in exploring the efficacy of natural compounds against various human cancers. Compounds of plant origin belonging to different groups such as alkaloids, flavonoids and polyphenols evaluated for their cancer preventive effects have yielded promising data, thereby offering a potential therapeutic alternative against this deadly disease. The flavonol fisetin (3,3',4',7-tetrahydroxyflavone), present in fruits and vegetables such as strawberries, apple, cucumber, persimmon, grape and onion, was shown to possess anti-microbial, anti-inflammatory, anti-oxidant and more significantly anti-carcinogenic activity when assessed in diverse cell culture and animal model systems. The purpose of this review is to update and discuss key findings obtained till date from in vitro and in vivo studies on fisetin, with special focus on its anti-cancer role. The molecular mechanism(s) described in the observed growth inhibitory effects of fisetin in different cancer cell types is also summarized. Moreover, an attempt is made to delineate the direction of future studies that could lead to the development of fisetin as a potent chemopreventive/chemotherapeutic agent against cancer.

Polymeric micelles encapsulating fisetin improve the therapeutic effect in colon cancer

The natural flavonoid fisetin (3,3',4',7-tetrahydroxyflavone) was discovered to possess antitumor activity, revealing its potential value in future chemotherapy. However, its poor water solubility makes it difficult for intravenous administration. In this study, the monomethyl poly(ethylene glycol)-poly(ε-caprolactone) (MPEG-PCL) copolymer was applied to prepare nanoassemblies of fisetin by a self-assembly procedure. The prepared fisetin micelles gained a mean particle size of 22 ± 3 nm, polydisperse index of 0.163 ± 0.032, drug loading of 9.88 ± 0.14%, and encapsulation efficiency of 98.53 ± 0.02%. Compared with free fisetin, fisetin micelles demonstrated a sustained and prolonged in vitro release behavior, as well as enhanced cytotoxicity, cellular uptake, and fisetin-induced apoptosis in CT26 cells. As for in vivo studies, fisetin micelles were more competent for suppressing tumor growth and prolonging survival time than free fisetin in the subcutaneous CT26 tumor model. Furthermore, histological analysis, terminal deoxynucleotidyl transferase-mediated nick-end labeling assay, immunohistochemical detection of Ki-67, and microvessel density detection were conducted, demonstrating that fisetin micelles gained increased tumor apoptosis induction, proliferation suppression, and antiangiogenesis activities. In conclusion, we have successfully produced a MPEG-PCL-based nanocarrier encapsulating fisetin with enhanced antitumor activity.

Azaindolylsulfonamides, with a more selective inhibitory effect on histone deacetylase 6 activity, exhibit antitumor activity in colorectal cancer HCT116 cells

A series of indolylsulfonylcinnamic hydroxamates has been synthesized. Compound 12, (E)-3-(3-((1H-pyrrolo[2,3-b]pyridin-1-yl)sulfonyl)phenyl)-N-hydroxyacrylamide, which has a 7-azaindole core cap, was shown to have antiproliferative activity against KB, H460, PC3, HSC-3, HONE-1, A549, MCF-7, TSGH, MKN45, HT29, and HCT116 human cancer cell lines. Pharmacological studies indicated that 12 functions as a potent HDAC inhibitor with an IC50 value of 0.1 μM. It is highly selective for histone deacetylase 6 (HDAC6) and is 60-fold more active than against HDAC1 and 223-fold more active than against HDAC2. It has a good pharmacokinetic profile with oral bioavailability of 33%. In in vivo efficacy evaluations in colorectal HCT116 xenografts, compound 12 suppresses tumor growth more effectively than SAHA (1, N-hydroxy-N'-phenyloctanediamide) and is therefore seen as a suitable candidate for further investigation.

Anticarcinogenic effects of the ethanolic extract of Salix aegyptiaca in colon cancer cells: involvement of Akt/PKB and MAPK pathways

The bark from Salix species of plants has been traditionally consumed for its antiinflammatory properties. Because inflammation frequently accompanies the progress of colorectal cancer (CRC), we have evaluated the anticancer properties of the ethanolic extract from the bark (EEB) of S. aegyptiaca, a Salix species endogenous to the Middle East, using HCT-116 and HT29 CRC cell lines. Fresh bark from S. aegyptiaca was extracted with ethanol, fractionated by solvent-solvent partitioning and the fractions were analyzed by tandem mass spectrometry. Catechin, catechol, and salicin were the most abundant constituents of the extract. Interestingly, EEB showed the highest anticancer effect in the colon cancer cells followed by its fractions in ethyl acetate and water, with catechin, catechol, and salicin showing the least efficacy. EEB could strongly reduce the proliferation of the cancer cells, but not of CCD-18Co, normal colon fibroblast cell line. Accompanying this was cell cycle arrest at G1/S independent of DNA damage in the cancer cells, induction of apoptosis through a p53 dependent pathway and an inhibition of PI3K/Akt and MAP Kinase pathways at levels comparable to known commercial inhibitors. We propose that the combination of the polyphenols and flavonoids in EEB contributes toward its potent anticarcinogenic effects. [Supplementary materials are available for this article. Go to the publisher's online edition of Nutrition and Cancer for the following free supplemental resource(s): Supplementary Figure 1 and Supplementary Figure 2.].

Fisetin: a dietary antioxidant for health promotion

SIGNIFICANCE

Diet-derived antioxidants are now being increasingly investigated for their health-promoting effects, including their role in the chemoprevention of cancer. In general, botanical antioxidants have received much attention, as they can be consumed for longer periods of time without any adverse effects. Flavonoids are a broadly distributed class of plant pigments that are regularly consumed in the human diet due to their abundance. One such flavonoid, fisetin (3,3',4',7-tetrahydroxyflavone), is found in various fruits and vegetables, such as strawberry, apple, persimmon, grape, onion, and cucumber.

RECENT ADVANCES

Several studies have demonstrated the effects of fisetin against numerous diseases. It is reported to have neurotrophic, anticarcinogenic, anti-inflammatory, and other health beneficial effects.

CRITICAL ISSUES

Although fisetin has been reported as an anticarcinogenic agent, further in-depth in vitro and in vivo studies are required to delineate the mechanistic basis of its observed effects. In this review article, we describe the multiple effects of fisetin with special emphasis on its anticancer activity as investigated in cell culture and animal models.

FUTURE DIRECTIONS

Additional research focused toward the identification of molecular targets could lead to the development of fisetin as a chemopreventive/chemotherapeutic agent against cancer and other diseases.

Progress in understanding the relationship between ATM gene and radiosensitivity of colorectal cancer

Ataxia telangiectasia (AT) is an autosomal recessive disease, and the responsible gene is ATM. One clinical characteristic of AT is exquisite radiosensitivity to ionizing radiation. The ATM gene has been one of the most important targets in radiobiology field that are used to elucidate the mechanisms of radiosensitivity and radioresistance. This gene is located on human chromosome 11q22-q23 and is involved in the repair of DNA damage and regulation of cell cycle checkpoints. This article reviews the structure and functions of the ATM gene and the relationship between ATM and radiosensitivity of colorectal cancer.

Dietary flavonoid fisetin: a novel dual inhibitor of PI3K/Akt and mTOR for prostate cancer management

Epidemiologic and case control population based studies over the past few decades have identified diet as an important determinant of cancer risk. This evidence has kindled interest into research on bioactive food components and has till date resulted in the identification of many compounds with cancer preventive and therapeutic potential. Among such compounds has been fisetin (3,7,3',4'-tetrahydroxyflavone), a flavonol and a member of the flavonoid polyphenols that also include quercetin, myricetin and kaempferol. Fisetin is commonly found in many fruits and vegetables such as apples, persimmons, grapes, kiwis, strawberries, onions and cucumbers. We evaluated the effects of fisetin against melanoma and cancers of the prostate, pancreas and the lungs. Using prostate and lung adenocarcinoma cells, we demonstrated that fisetin acts as a dual inhibitor of the PI3K/Akt and the mTOR pathways. This is a significant finding considering the fact that mTOR is phosphorylated and its activation is more frequent in tumors with overexpression of PI3K/Akt. Dual inhibitors of PI3K/Akt and mTOR signaling have been suggested as valuable agents for treating such cancers. Here, we summarize our findings on the dietary flavonoid fisetin and its effects on cancer with particular focus on prostate cancer. Our observations and findings from other laboratories suggest that fisetin could be a useful chemotherapeutic agent that could be used either alone or as an adjuvant with conventional chemotherapeutic drugs for the management of prostate and other cancers.

Effects of phytochemicals on ionization radiation-mediated carcinogenesis and cancer therapy

Ionizing radiation (IR)-induced cellular damage is implicated in carcinogenesis as well as therapy of cancer. Advances in radiation therapy have led to the decrease in dosage and localizing the effects to the tumor; however, the development of radioresistance in cancer cells and radiation toxicity to normal tissues are still the major concerns. The development of radioresistance involves several mechanisms, including the activation of mitogenic and survival signaling, induction of DNA repair, and changes in redox signaling and epigenetic regulation. The current strategy of combining radiation with standard cytotoxic chemotherapeutic agents can potentially lead to unwanted side effects due to both agents. Thus agents are needed that could improve the efficacy of radiation killing of cancer cells and prevent the damage to normal cells and tissues caused by the direct and bystander effects of radiation, without have its own systemic toxicity. Chemopreventive phytochemicals, usually non-toxic agents with both cancer preventive and therapeutic activities, could rightly fit in this approach. In this regard, naturally occurring compounds, including curcumin, parthenolide, genistein, gossypol, ellagic acid, withaferin, plumbagin and resveratrol, have shown considerable potential. These agents suppress the radiation-induced activation of receptor tyrosine kinases and nuclear factor-κB signaling, can modify cell survival and DNA repair efficacy, and may potentiate ceramide signaling. These radiosensitizing and counter radioresistance mechanisms of phytochemicals in cancer cells are also associated with changes in epigenetic gene regulation. Because radioresistance involves multiple mechanisms, more studies are needed to discover novel phytochemicals having multiple mechanisms of radiosensitization and to overcome radioresistance of cancer cells. Pre-clinical studies are needed to address the appropriate dosage, timing, and duration of the application of phytochemicals with radiation to justify clinical trials. Nonetheless, some phytochemicals in combination with IR may play a significant role in enhancing the therapeutic index of cancer treatment.

Polyphenols as small molecular inhibitors of signaling cascades in carcinogenesis

Multiple lines of evidences suggest that oxidative stress induced by reactive oxygen species are closely related to multi-stage carcinogenesis. Polyphenols, a group of chemicals with more than one phenol unit or building block per molecule, have been recognized for possessing many health benefits including cancer-preventive effects mainly due to their antioxidant activity. However, polyphenols can directly bind with signaling molecules involved in carcinogenesis and regulate its activity. Moreover, it is noteworthy that the binding between the polyphenol and the target protein is determined by their structural relationship, which implies that different polyphenols have different target proteins, leading to divergent chemopreventive effects. Extracellular stimuli transmit signals into a cell by activating their target signaling cascades involved in carcinogenesis. As an example, Src family kinase, a family of proto-oncogenic tyrosine kinases activated by a variety of oxidative stress and proinflammatory agents, is known to regulate cell proliferation, differentiation, survival and angiogenesis. Src family kinase subsequently activates downstream signal cascades including mitogen-activated protein kinase, phosphoinositol-3-kinase, and nuclear factor-kappaB, thereby inducing cell proliferation and causing cancer. Recent studies demonstrate that polyphenols can directly target signaling cascades involved in inflammation and the development of cancer. Inhibition of the kinases by polyphenols contributes to the attenuation of carcinogenesis. Therefore, the development of polyphenols as direct inhibitors against target proteins is regarded as a rational approach for chemoprevention. This review describes and discusses recent results about the direct interactions of polyphenols and protein kinases in cancer chemoprevention.