Inhibition of telomerase activity and induction of apoptosis by curcumin in K-562 cells

Telomerase Inhibition in the Treatment of Leukemia: A Comprehensive Review

Leukemia, characterized by the uncontrolled proliferation and differentiation blockage of myeloid or lymphoid precursor cells, presents significant therapeutic challenges despite current treatment modalities like chemotherapy and stem cell transplantation. Pursuing novel therapeutic strategies that selectively target leukemic cells is critical for improving patient outcomes. Natural products offer a promising avenue for developing effective chemotherapy and preventive measures against leukemia, providing a rich source of biologically active compounds. Telomerase, a key enzyme involved in chromosome stabilization and mainly active in cancer cells, presents an attractive target for intervention. In this review article, we focus on the anti-leukemic potential of natural substances, emphasizing vitamins (such as A, D, and E) and polyphenols (including curcumin and indole-3-carbinol), which, in combination with telomerase inhibition, demonstrate reduced cytotoxicity compared to conventional chemotherapies. We discuss the role of human telomerase reverse transcriptase (hTERT), particularly its mRNA expression, as a potential therapeutic target, highlighting the promise of natural compounds in leukemia treatment and prevention.

Telomerase and hallmarks of cancer: An intricate interplay governing cancer cell evolution

Transformed cells must acquire specific characteristics to be malignant. Weinberg and Hanahan characterize these characteristics as cancer hallmarks. Though these features are independently driven, substantial signaling crosstalk in transformed cells efficiently promotes these feature acquisitions. Telomerase is an enzyme complex that maintains telomere length. However, its main component, Telomere reverse transcriptase (TERT), has been found to interact with various signaling molecules like cMYC, NF-kB, BRG1 and cooperate in transcription and metabolic reprogramming, acting as a strong proponent of malignant features such as cell death resistance, sustained proliferation, angiogenesis activation, and metastasis, among others. It allows cells to avoid replicative senescence and achieve endless replicative potential. This review summarizes both the canonical and noncanonical functions of TERT and discusses how they promote cancer hallmarks. Understanding the role of Telomerase in promoting cancer hallmarks provides vital insight into the underlying mechanism of cancer genesis and progression and telomerase intervention as a possible therapeutic target for cancer treatment. More investigation into the precise molecular mechanisms of telomerase-mediated impacts on cancer hallmarks will contribute to developing more focused and customized cancer treatment methods.

Combining old and new concepts in targeting telomerase for cancer therapy: transient, immediate, complete and combinatory attack (TICCA)

Telomerase can overcome replicative senescence by elongation of telomeres but is also a specific element in most cancer cells. It is expressed more vastly than any other tumor marker. Telomerase as a tumor target inducing replicative immortality can be overcome by only one other mechanism: alternative lengthening of telomeres (ALT). This limits the probability to develop resistance to treatments. Moreover, telomerase inhibition offers some degree of specificity with a low risk of toxicity in normal cells. Nevertheless, only one telomerase antagonist reached late preclinical studies. The underlying causes, the pitfalls of telomerase-based therapies, and future chances based on recent technical advancements are summarized in this review. Based on new findings and approaches, we propose a concept how long-term survival in telomerase-based cancer therapies can be significantly improved: the TICCA (Transient Immediate Complete and Combinatory Attack) strategy.

Accumulation of TERT in mitochondria exerts two opposing effects on apoptosis

Telomerase reverse transcriptase (TERT) is a protein that catalyzes the reverse transcription of telomere elongation. TERT is also expected to play a non-canonical role beyond telomere lengthening since it localizes not only in the nucleus but also in mitochondria, where telomeres do not exist. Several studies have reported that mitochondrial TERT regulates apoptosis induced by oxidative stress. However, there is still some controversy as to whether mitochondrial TERT promotes or inhibits apoptosis, mainly due to the lack of information on changes in TERT distribution in individual cells over time. Here, we simultaneously detected apoptosis and TERT localization after oxidative stress in individual HeLa cells by live-cell tracking. Single-cell tracking revealed that the stress-induced accumulation of TERT in mitochondria caused apoptosis, but that accumulation increased over time until cell death. The results suggest a new model in which mitochondrial TERT has two opposing effects at different stages of apoptosis: it predetermines apoptosis at the first stage of cell-fate determination, but also delays apoptosis at the second stage. As such, our data support a model that integrates the two opposing hypotheses on mitochondrial TERT's effect on apoptosis. Furthermore, detailed statistical analysis of TERT mutations, which have been predicted to inhibit TERT transport to mitochondria, revealed that these mutations suppress apoptosis independent of mitochondrial localization of TERT. Together, these results imply that the non-canonical functions of TERT affect a wide range of mitochondria-dependent and mitochondria-independent apoptosis pathways.

Cell Survival, Death, and Proliferation in Senescent and Cancer Cells: the Role of (Poly)phenols

Cellular senescence has long been considered a permanent state of cell cycle arrest occurring in proliferating cells subject to different stressors, used as a cellular defense mechanism from acquiring potentially harmful genetic faults. However, recent studies highlight that senescent cells might also alter the local tissue environment and concur to chronic inflammation and cancer risk by secreting inflammatory and matrix remodeling factors, acquiring a senescence-associated secretory phenotype (SASP). Indeed, during aging and age-related diseases, senescent cells amass in mammalian tissues, likely contributing to the inevitable loss of tissue function as we age. Cellular senescence has thus become one potential target to tackle age-associated diseases as well as cancer development. One important aspect characterizing senescent cells is their telomere length. Telomeres shorten as a consequence of multiple cellular replications, gradually leading to permanent cell cycle arrest, known as replicative senescence. Interestingly, in the large majority of cancer cells, a senescence escape strategy is used and telomere length is maintained by telomerase, thus favoring cancer initiation and tumor survival. There is growing evidence showing how (poly)phenols can impact telomere maintenance through different molecular mechanisms depending on dose and cell phenotypes. Although normally, (poly)phenols maintain telomere length and support telomerase activity, in cancer cells this activity is negatively modulated, thus accelerating telomere attrition and promoting cancer cell death. Some (poly)phenols have also been shown to exert senolytic activity, thus suggesting both antiaging (directly eliminating senescent cells) and anticancer (indirectly, via SASP inhibition) potentials. In this review, we analyze selective (poly)phenol mechanisms in senescent and cancer cells to discriminate between in vitro and in vivo evidence and human applications considering (poly)phenol bioavailability, the influence of the gut microbiota, and their dose-response effects.

CD123-Targeted Nano-Curcumin Molecule Enhances Cytotoxic Efficacy in Leukemic Stem Cells

Acute myeloblastic leukemia (AML) is a disease with a high rate of relapse and drug resistance due to the remaining leukemic stem cells (LSCs). Therefore, LSCs are specific targets for the treatment of leukemia. CD123 is specifically expressed on LSCs and performs as a specific marker. Curcumin is the main active compound of a natural product with low toxicity for humans. It has been reported to inhibit leukemic cell growth. However, curcumin is practically insoluble in water and has low bioavailability. In this study, we aimed to formulate curcumin nanoparticles and conjugate with the anti-CD123 to overcome the low water solubility and improve the targeting of LSCs. The cytotoxicity of both curcumin-loaded PLGA/poloxamer nanoparticles (Cur-NPs) and anti-CD123-curcumin-loaded PLGA/poloxamer nanoparticles (anti-CD123-Cur-NPs) were examined in KG-1a cells. The results showed that Cur-NPs and Cur-NPs-CD123 exhibited cytotoxic effects on KG-1a cells with the IC₅₀ values of 74.20 ± 6.71 and 41.45 ± 5.49 µM, respectively. Moreover, anti-CD123-Cur-NPs induced higher apoptosis than Cur-NPs. The higher uptake of anti-CD123-Cur-NPs in KG-1a cells was confirmed by using flow cytometry. In conclusion, the anti-CD123-Cur-NPs formulation improved curcumin's bioavailability and specific targeting of LSCs, suggesting that it is a promising drug delivery system for improving the therapeutic efficacy against AML.

Chemometric-enhanced metabolic profiling of five Pinus species using HPLC-MS/MS spectrometry: Correlation to in vitro anti-aging, anti-Alzheimer and antidiabetic activities

Detailed metabolic profiling of needles of five Pinus species was investigated using complementary HPLC-MS/MS techniques together with supervised and unsupervised chemometric tools. This resulted in putative identification of 44 compounds belonging to flavonoids, phenolics, lignans, diterpenes and fatty acids. Unsupervised principal component analysis showed that differences were maintained across the metabolites characteristic of each Pinus species, are mainly related to di-O-p-coumaroyltrifolin, p-coumaroyl quinic acid derivative, arachidonic acid, hydroxypalmitic acid, isopimaric acid and its derivative. A supervised Partial Least Squares regression analysis was performed to correlate HPLC-MS/MS profiles with the variation observed in the in vitro anticholinesterase, antiaging and anti-diabetic potential. All investigated Pinus extracts exerted their antiaging activity via increasing telomerase and TERT levels in normal human melanocytes cells compared to the control (untreated cells). Profound inhibition activities of acetylcholinesterase and dipeptidyl peptidase-4 were also observed with P. pinea and P. canariensis extracts having comparable antidiabetic activities to sitagliptin as a standard antidiabetic drug. Our findings suggested that pine needles are a good source of phenolics and diterpenoids that have possible health promoting activities in management and alleviation of diabetic conditions and Alzheimer disease.

Anti-proliferative and apoptotic effect of gemini curcumin in p53-wild type and p53-mutant colorectal cancer cell lines

BACKGROUND

Despite recent advances in therapy, colorectal cancer remains a leading cause of death in affected people. Curcumin is the main bioactive compound of turmeric that has been demonstrated as an effective agent against cancer. However, its poor stability and bioavailability limit therapeutic application. We previously showed that delivery of curcumin by using gemini surfactant nanoparticles called gemini curcumin (Gemini-Cur) could improve its solubility, uptake and toxic effect on breast and ovarian cancer cells. Here, we aimed to investigate the anticancer activity of Gemini-Cur in both p53-mutant and p53-wild type colorectal cancer cells. The toxicity of Gemini-Cur on HT-29 and HCT116 was studied through MTT, uptake kinetics, fluorescence microscopy, annexin V/FITC, and cell cycle assays. Also, real-time PCR and western blotting were performed to evaluate the expression of p53, p21, BAX, BCL-2, and NOXA genes. Our data showed that Gemini-Cur not only enters cells quite rapidly compared to free curcumin crystals, but also suppresses HT-29 and HCT-116 cells proliferation in a time- and dose-dependent manner (p < 0.001). The IC50 values as well as apoptosis assays showed that p53-wild type cells are sensitive to Gemini-Cur. Flow cytometry also revealed that the number of apoptotic cells is dramatically increased in HCT-116 cells earlier than HT-29 cells (p < 0.0001). Gemini-Cur upregulated apoptotic genes including p53 (in both mutant and wild-type forms), p21, NOXA and BAX while decreased anti-apoptotic BCL-2 in mRNA and protein level (p < 0.0001). As a hallmark of apoptosis, the expression ratio of BAX/BCL-2 was significantly increased in all treated cells. Taken together, our findings demonstrated that Gemini-Cur suppresses the proliferation of cancer cells via induction of apoptosis and could be considered as novel nano-formulated phytochemical for cancer targeting.

Design of New Improved Curcumin Derivatives to Multi-targets of Cancer and Inflammation

BACKGROUND

Curcumin is a major active principle of Curcuma longa. There are more than 1700 citations in the Medline, reflecting various biological effects of curcumin. Most of these biological activities are associated with the antioxidant, anti-inflammatory and antitumor activity of the molecule. Several reports suggest various targets of natural curcumin that include growth factors, growth factor receptor, cytokines, enzymes and gene regulators of apoptosis. This review focuses on the improved curcumin derivatives that target the cancer and inflammation.

METHODOLOGY

In this present review, we explored the anticancer drugs with curcumin-based drugs under pre-clinical and clinical studies with critical examination. Based on the strong scientific reports of patentable and non-patented literature survey, we have investigated the mode of the interactions of curcumin-based molecules with the target molecules.

RESULTS

Advanced studies have added new dimensions of the molecular response of cancer cells to curcumin at the genomic level. However, poor bioavailability of the molecule seems to be the major limitation of the curcumin. Several researchers have been involved to improve the curcumin derivatives to overcome this limitation. Sufficient data of clinical trials to various cancers that include multiple myeloma, pancreatic cancer and colon cancer, have also been discussed.

CONCLUSION

The detailed analysis of the structure-activity relationship (SAR) and common synthesis of curcumin-based derivatives have been discussed in the review. Utilising the predictions of in silico coupled with validation reports of in vitro and in vivo studies have concluded many targets for curcumin. Among them, cancer-related inflammation genes regulating curcumin-based molecules are a very promising target to overcome hurdles in the multimodality therapy of cancer.

Telomerase: A Target for Therapeutic Effects of Curcumin in Cancer

Telomerases are attractive targets for development of new anticancer agents. Most tumors express the enzyme telomerase that maintains telomere length and thus ensures indefinite cell proliferation, a hallmark of cancer. Curcumin has been shown to be effective against several types of malignancies and has also been shown to have inhibitory effects on telomerase activity. Hence, the aim of this chapter is to review the available investigations of curcumin on telomerase activity. Based on the findings obtained from the different studies here, we conclude that the telomerase inhibitory effects of curcumin are integral to its anticancer activity, and thus curcumin may be useful therapeutically in the cancer field.

Fundamental insights into the interaction between telomerase/TERT and intracellular signaling pathways

Telomerase activity is critical for cancer cells to provide unrestricted proliferation and cellular immortality through maintaining telomeres. Telomerase enzymatic activity is regulatable at the level of DNA, mRNA, post translational modifications, cellular transport and enzyme assembly. More recent studies confirm the interaction of the telomerase with various intracellular signaling pathways including PI3K/AKT/mTOR, NF-κB and Wnt/β-catenin which mainly participating in inflammation, epithelial to mesenchymal transition (EMT) and tumor cell invasion and metastasis. Furthermore, hTERT protein has been detected in non-nuclear sites such as the mitochondria and cytoplasm in cells. Mitochondrial TERT indicates various non-telomere-related functions such as decreasing reactive oxygen species (ROS) generation, boosting the respiration rate, protecting mtDNA by direct binding, interacting with mitochondrial tRNAs and increasing mitochondrial membrane potential which can lead to higher chemoresistance rate in cancer cells during therapies. Understanding the molecular mechanisms of the TERT function and depended interactions in tumor cells can suggest novel therapeutic approaches. Hence, in this review we will explain the telomerase activity regulation in translational and post translational levels besides the established correlations with various cell signaling pathways with possible pathways for therapeutic targeting.

TERT promoter mutation determines apoptotic and therapeutic responses of BRAF-mutant cancers to BRAF and MEK inhibitors: Achilles Heel

Combination use of BRAF V600E inhibitor dabrafenib and MEK inhibitor trametinib has become a standard treatment for human cancers harboring BRAF V600E. Its anticancer efficacies vary, however, with dramatic efficacy in some patients and drug resistance/tumor recurrence in others, which is poorly understood. Using thyroid cancer, melanoma, and colon cancer cell models, we showed that dabrafenib and trametinib induced robust apoptosis of cancer cells harboring both BRAF V600E and TERT promoter mutations but had little proapoptotic effect in cells harboring only BRAF V600E. Correspondingly, the inhibitors nearly completely abolished the growth of in vivo tumors harboring both mutations but had little effect on tumors harboring only BRAF V600E. Upon drug withdrawal, tumors harboring both mutations remained hardly measurable but tumors harboring only BRAF V600E regrew rapidly. BRAF V600E/MAP kinase pathway is known to robustly activate mutant promoter of TERT, a strong apoptosis suppressor. Thus, for survival, cancer cells harboring both mutations may have evolved to rely on BRAF V600E-promoted and high-TERT expression-mediated suppression of apoptosis. As such, inhibition of BRAF/MEK can trigger strong apoptosis-induced cell death and hence tumor abolishment. This does not happen in cells harboring only BRAF V600E as they have not developed reliance on TERT-mediated suppression of apoptosis due to the lack of mutant promoter-driven high-TERT expression. TERT promoter mutation governs BRAF-mutant cancer cells' apoptotic and hence therapeutic responses to BRAF/MEK inhibitors. Thus, the genetic duet of BRAF V600E and TERT promoter mutation represents an Achilles Heel for effective therapeutic targeting and response prediction in cancer.

Targeting telomerase for its advent in cancer therapeutics

Telomerase has emerged as an important primary target in anticancer therapy. It is a distinctive reverse transcriptase enzyme, which extends the length of telomere at the 3' chromosomal end, and uses telomerase reverse transcriptase (TERT) and telomerase RNA template-containing domains. Telomerase has a vital role and is a contributing factor in human health, mainly affecting cell aging and cell proliferation. Due to its unique feature, it ensures unrestricted cell proliferation in malignancy and plays a major role in cancer disease. The development of telomerase inhibitors with increased specificity and better pharmacokinetics is being considered to design and develop newer potent anticancer agents. Use of natural and synthetic compounds for the inhibition of telomerase activity can lead to an opening of new vistas in cancer treatment. This review details about the telomerase biochemistry, use of natural and synthetic compounds; vaccines and oncolytic virus in therapy that suppress the telomerase activity. We have discussed structure-activity relationships of various natural and synthetic telomerase inhibitors to help medicinal chemists and chemical biology researchers with a ready reference and updated status of their clinical trials. Suppression of human TERT (hTERT) activity through inhibition of hTERT promoter is an important approach for telomerase inhibition.

Delivery of natural phenolic compounds for the potential treatment of lung cancer

The application of natural products to treat various diseases, such as cancer, has been an important area of research for many years. Several phytochemicals have demonstrated anticarcinogenic activity to prevent or reduce the progression of cancer by modulating various cellular mechanisms. However, poor bioavailability has hindered clinical success and the incorporation of these drugs into efficient drug delivery systems would be beneficial. For lung cancer, local delivery via the pulmonary route would also be more effective. In this article, recent in vitro scientific literature on phenolic compounds with anticancer activity towards lung cancer cell lines is reviewed and nanoparticulate delivery is mentioned as a possible solution to the problem of bioavailability. The first part of the review will explore the different classes of natural phenolic compounds and discuss recent reports on their activity on lung cancer cells. Then, the problem of the poor bioavailability of phenolic compounds will be explored, followed by a summary of recent advances in improving the efficacy of these phenolic compounds using nanoparticulate drug delivery systems. Graphical abstract The rationale for direct delivery of phenolic compounds loaded in microparticles to the lungs.

Telomerase and poly(ADP-ribose) polymerase-1 activity sensing based on the high fluorescence selectivity and sensitivity of TOTO-1 towards G bases in single-stranded DNA and poly(ADP-ribose)

Telomerase and poly(ADP-ribose) polymerase-1 (PARP-1) are two potential cancer biomarkers and are closely related to tumor initiation and malignant progression. TOTO-1 is well-known for differentiating ss-DNA from ds-DNA because it is virtually non-fluorescent without DNA and exhibits very low fluorescence with ss-DNA, while it emits strong fluorescence with ds-DNA. In this paper, for the first time, it was found that TOTO-1 has high fluorescence selectivity and sensitivity towards the G bases in single-stranded DNA and poly(ADP-ribose) (PAR). Poly(dG) was used as the model target to explore its possible mechanism. Molecular dynamics (MD) simulation proved that intramolecular π-π stacking existed in TOTO-1 (in an aqueous solution), while intermolecular π-π stacking formed between TOTO-1 and poly(dG) in a similar way as that observed for dsDNA. Interestingly, telomerase and PARP-1 catalyzed the formation of G-rich DNA and PAR in vivo, respectively. Therefore, TOTO-1 was explored in detecting both of them, obtaining satisfactory results. To the best of our knowledge, no probe has been reported to recognize PAR. It is also the first time where telomerase is detected based on the specific recognition of G bases. Importantly, integrating multiple functions into one probe that can detect not only telomerase but also PARP-1 will significantly raise the specificity of screening cancer and decrease false positive proportion, which make TOTO-1 a promising candidate probe for clinical diagnosis and pharmaceutical screening.

Quartz crystal microbalance for telomerase sensing based on gold nanoparticle induced signal amplification

A mass-sensitive quartz crystal microbalance biosensor was constructed for telomerase sensing based on gold nanoparticle induced signal amplification.

Effect of therapies-mediated modulation of telomere and/or telomerase on cancer cells radiosensitivity

Cancer is one of the leading causes of death in the world. Many strategies of cancer treatment such as radiotherapy which plays a key role in cancer treatment are developed and used nowadays. However, the side effects post-cancer radiotherapy and cancer radioresistance are two major causes of the limitation of cancer radiotherapy effectiveness in the cancer patients. Moreover, reduction of the limitation of cancer radiotherapy effectiveness by reducing the side effects post-cancer radiotherapy and cancer radioresistance is the aim of several radiotherapy-oncologic teams. Otherwise, Telomere and telomerase are two cells components which play an important role in cancer initiation, cancer progression and cancer therapy resistance such as radiotherapy resistance. For resolving the problems of the limitation of cancer radiotherapy effectiveness especially the cancer radio-resistance problems, the radio-gene-therapy strategy which is the use of gene-therapy via modulation of gene expression combined with radiotherapy was developed and used as a new strategy to treat the patients with cancer. In this review, we summarized the information concerning the implication of telomere and telomerase modulation in cancer radiosensitivity.

Curcumin differentially affects cell cycle and cell death in acute and chronic myeloid leukemia cells

Curcumin is a phytochemical with potent anti-neoplastic properties. The antitumoral effects of curcumin in cells derived from chronic or acute myeloid leukemia have been already described. However, a comparative study of the cytostatic and cytotoxic effects of curcumin on chronic and acute myeloid leukemia cells has not yet been performed. In the present study, the cellular effects of curcumin on cell lines derived from chronic or acute myeloid leukemia were examined. Dose and time-response assays were performed with curcumin on HL-60 and K562 cells. Cell viability was evaluated with trypan blue exclusion test and cell death by flow cytometry using a fluorescent molecular probe. A cell cycle profile was analyzed, and protein markers of cell cycle progression and cell death were investigated. In the present study, the K562 cells showed a higher sensitivity to the cytostatic and cytotoxic effects of curcumin compared with HL-60. In addition, curcumin induced G1 phase arrest in HL-60 cells and G2/M phase arrest in K562 cells. Furthermore, curcumin-related cell death in HL-60 was associated with the processed forms of caspases-9 and -3 proteins, whereas in K562 cells, both the processed and the unprocessed forms were present. Accordingly, activity of these caspases was significantly higher in HL-60 cells compared with that in K562. In conclusion, curcumin elicits different cellular mechanisms in chronic or acute myeloid leukemia cells and the powerful antitumoral effect was more potent in K562 compared with HL-60 cells.

Telomerase Inhibitors from Natural Products and Their Anticancer Potential

Telomeres and telomerase are nowadays exploring traits on targets for anticancer therapy. Telomerase is a unique reverse transcriptase enzyme, considered as a primary factor in almost all cancer cells, which is mainly responsible to regulate the telomere length. Hence, telomerase ensures the indefinite cell proliferation during malignancy—a hallmark of cancer—and this distinctive feature has provided telomerase as the preferred target for drug development in cancer therapy. Deactivation of telomerase and telomere destabilization by natural products provides an opening to succeed new targets for cancer therapy. This review aims to provide a fundamental knowledge for research on telomere, working regulation of telomerase and its various binding proteins to inhibit the telomere/telomerase complex. In addition, the review summarizes the inhibitors of the enzyme catalytic subunit and RNA component, natural products that target telomeres, and suppression of transcriptional and post-transcriptional levels. This extensive understanding of telomerase biology will provide indispensable information for enhancing the efficiency of rational anti-cancer drug design.

Telomerase and drug resistance in cancer

It is well known that a decreased expression or inhibited activity of telomerase in cancer cells is accompanied by an increased sensitivity to some drugs (e.g., doxorubicin, cisplatin, or 5-fluorouracil). However, the mechanism of the resistance resulting from telomerase alteration remains elusive. There are theories claiming that it might be associated with telomere shortening, genome instability, hTERT translocation, mitochondria functioning modulation, or even alterations in ABC family gene expression. However, association of those mechanisms, i.e., drug resistance and telomerase alterations, is not fully understood yet. We review the current theories on the aspect of the role of telomerase in cancer cells resistance to therapy. We believe that revealing/unravelling this correlation might significantly contribute to an increased efficiency of cancer cells elimination, especially the most difficult ones, i.e., drug resistant.

Unraveling the Anticancer Effect of Curcumin and Resveratrol

Resveratrol and curcumin are natural products with important therapeutic properties useful to treat several human diseases, including cancer. In the last years, the number of studies describing the effect of both polyphenols against cancer has increased; however, the mechanism of action in all of those cases is not completely comprehended. The unspecific effect and the ability to interfere in assays by both polyphenols make this challenge even more difficult. Herein, we analyzed the anticancer activity of resveratrol and curcumin reported in the literature in the last 11 years, in order to unravel the molecular mechanism of action of both compounds. Molecular targets and cellular pathways will be described. Furthermore, we also discussed the ability of these natural products act as chemopreventive and its use in association with other anticancer drugs.

Apoptotic Effect of Biophytum sensitivum on B16F-10 Cells and Its Regulatory Effects on Nitric Oxide and Cytokine Production on Tumor-Associated Macrophages

The present study is part of a large-scale investigation of the antitumor effects of Biophytum sensitivum on B16F-10 melanoma cells. The investigation involved the regulatory effect of B sensitivum on nitric oxide and cytokine production in B16F-10 cells, tumor-associated macrophages, and peritoneal macrophages as well as on the apoptotic process in B16F-10 melanoma cells. B sensitivum at a concentration of 10 µg/mL could significantly ( P < .001) inhibit production of nitric oxide and proinflammatory cytokines such as interleukin-1β, interleukin-6, granulocyte monocyte-colony stimulating factor, and tumor necrosis factor-α in B16F-10 cells, tumor-associated macrophages, and peritoneal macrophages. Incubation of B16F-10 cells with B sensitivum showed the presence of apoptotic bodies and induced DNA fragmentation. Furthermore, B sensitivum showed an inhibitory effect on inducible nitric oxide synthase as well as bcl-2 expression, and up-regulated p53 and caspase-3 messenger RNA expression in B16F-10 melanoma cells. The observed results suggest that regulation of proinflammatory cytokine production by tumor cells, tumor-associated macrophages, and resident macrophages accompanied by altered inducible nitric oxide synthase, bcl-2, caspase-3, and p53 messenger RNA expression by B sensitivum methanol extract induces apoptosis in B16F-10 melanoma cells.

Therapeutic Targeting of Telomerase

Telomere length and cell function can be preserved by the human reverse transcriptase telomerase (hTERT), which synthesizes the new telomeric DNA from a RNA template, but is normally restricted to cells needing a high proliferative capacity, such as stem cells. Consequently, telomerase-based therapies to elongate short telomeres are developed, some of which have successfully reached the stage I in clinical trials. Telomerase is also permissive for tumorigenesis and 90% of all malignant tumors use telomerase to obtain immortality. Thus, reversal of telomerase upregulation in tumor cells is a potential strategy to treat cancer. Natural and small-molecule telomerase inhibitors, immunotherapeutic approaches, oligonucleotide inhibitors, and telomerase-directed gene therapy are useful treatment strategies. Telomerase is more widely expressed than any other tumor marker. The low expression in normal tissues, together with the longer telomeres in normal stem cells versus cancer cells, provides some degree of specificity with low risk of toxicity. However, long term telomerase inhibition may elicit negative effects in highly-proliferative cells which need telomerase for survival, and it may interfere with telomere-independent physiological functions. Moreover, only a few hTERT molecules are required to overcome senescence in cancer cells, and telomerase inhibition requires proliferating cells over a sufficient number of population doublings to induce tumor suppressive senescence. These limitations may explain the moderate success rates in many clinical studies. Despite extensive studies, only one vaccine and one telomerase antagonist are routinely used in clinical work. For complete eradication of all subpopulations of cancer cells a simultaneous targeting of several mechanisms will likely be needed. Possible technical improvements have been proposed including the development of more specific inhibitors, methods to increase the efficacy of vaccination methods, and personalized approaches. Telomerase activation and cell rejuvenation is successfully used in regenerative medicine for tissue engineering and reconstructive surgery. However, there are also a number of pitfalls in the treatment with telomerase activating procedures for the whole organism and for longer periods of time. Extended cell lifespan may accumulate rare genetic and epigenetic aberrations that can contribute to malignant transformation. Therefore, novel vector systems have been developed for a 'mild' integration of telomerase into the host genome and loss of the vector in rapidly-proliferating cells. It is currently unclear if this technique can also be used in human beings to treat chronic diseases, such as atherosclerosis.

Dendrosomal curcumin nanoformulation modulate apoptosis-related genes and protein expression in hepatocarcinoma cell lines

The side-effects observed in conventional therapies have made them unpromising in curing Hepatocellular carcinoma; therefore, developing novel treatments can be an overwhelming significance. One of such novel agents is curcumin which can induce apoptosis in various cancerous cells, however, its poor solubility is restricted its application. To overcome this issue, this paper employed dendrosomal curcumin (DNC) was employed to in prevent hepatocarcinoma in both RNA and protein levels. Hepatocarcinoma cells, p53 wild-type HepG2 and p53 mutant Huh7, were treated with DNC and investigated for toxicity study using MTT assay. Cell cycle distribution and apoptosis were analyzed using Flow-cytometry and Annexin-V-FLUOS/PI staining. Real-time PCR and Western blot were employed to analyze p53, BAX, Bcl-2, p21 and Noxa in DNC-treated cells. DNC inhibited the growth in the form of time-dependent manner, while the carrier alone was not toxic to the cell. Flow-cytometry data showed the constant concentration of 20μM DNC during the time significantly increases cell population in SubG1 phase. Annexin-V-PI test showed curcumin-induced apoptosis was enhanced in Huh7 as well as HepG2, compared to untreated cells. Followed by treatment, mRNA expression of p21, BAX, and Noxa increased, while the expression of Bcl-2 decreased, and unlike HepG2, Huh7 showed down-regulation of p53. In summary, DNC-treated hepatocellular carcinoma cells undergo apoptosis by changing the expression of genes involved in the apoptosis and proliferation processes. These findings suggest that DNC, as a plant-originated therapeutic agent, could be applied in cancer treatment.

Proteasome inhibitors, including curcumin, improve pancreatic β-cell function and insulin sensitivity in diabetic mice

Background:

Type 2 diabetes stems from obesity-associated insulin resistance, and in the genetically susceptible, concomitant pancreatic β-cell failure can occur, which further exacerbates hyperglycemia. Recent work by our group and others has shown that the natural polyphenol curcumin attenuates the development of insulin resistance and hyperglycemia in mouse models of hyperinsulinemic or compensated type 2 diabetes. Although several potential downstream molecular targets of curcumin exist, it is now recognized to be a direct inhibitor of proteasome activity. We now show that curcumin also prevents β-cell failure in a mouse model of uncompensated obesity-related insulin resistance (Lepr^db/db on the Kaliss background).

Results:

In this instance, dietary supplementation with curcumin prevented hyperglycemia, increased insulin production and lean body mass, and prolonged lifespan. In addition, we show that short-term in vivo treatment with low dosages of two molecularly distinct proteasome inhibitors celastrol and epoxomicin reverse hyperglycemia in mice with β-cell failure by increasing insulin production and insulin sensitivity.

Conclusions:

These studies suggest that proteasome inhibitors may prove useful for patients with diabetes by improving both β-cell function and relieving insulin resistance.

Curcumin and Health

Nowadays, there are some molecules that have shown over the years a high capacity to act against relevant pathologies such as cardiovascular disease, neurodegenerative disorders or cancer. This article provides a brief review about the origin, bioavailability and new research on curcumin and synthetized derivatives. It examines the beneficial effects on health, delving into aspects such as cancer, cardiovascular effects, metabolic syndrome, antioxidant capacity, anti-inflammatory properties, and neurological, liver and respiratory disorders. Thanks to all these activities, curcumin is positioned as an interesting nutraceutical. This is the reason why it has been subjected to several modifications in its structure and administration form that have permitted an increase in bioavailability and effectiveness against different diseases, decreasing the mortality and morbidity associated to these pathologies.

Evaluation of the Acute Toxicity, Cytotoxicity, and Genotoxicity of Chresta martii (Asteraceae)

Chresta martii (Asteraceae), found in the Xingó region, northeastern Brazil, is used in the treatment of gastrointestinal (GIT) and liver disorders and malaria. However, there are few studies regarding efficacy and safety of use for this species. Thus, the objective of this study was to determine in vivo acute toxicity and in vitro cytotoxicity of organic extracts of C. martii as well as in vivo genotoxicity of its semipurified fraction. Dried aerial parts of C. martii were extracted using three organic solvents (cyclohexane [ECCm], ethyl acetate [EACm], and ethanol [EECm]), and these extracts were examined for acute toxicity (50-2000 mg/kg ip or po) and cytotoxicity (50 μg/ml) in carcinogenic human cell lines (HL-60, NCIH-292, and MCF-7). The EACm, which showed evidence of toxicity (in vivo and in vitro), was fractionated on a silica column, yielding four fractions (F1-F4). The F1 was utilized for genotoxicity (50 mg/kg ip), by in vivo micronucleus (MN) assay. ECCm showed no indication of acute toxicity or occurrence of death, while the LD50 estimated for the extracts (EACm and EECm) was 500 mg/kg po and 200 mg/kg ip. The EACm (50 μg/ml) inhibited growth of tumor cells HL-60 (96.54%), NCIH-292 (73.43%), and MCF-7 (15%). The F1 fraction induced MN formation in polychromatic erythrocytes of Swiss Webster mice. Organic extracts from C. martii exhibited acute toxicity classified as mild to moderate, in addition to cytotoxicity (in vitro), while the F1 semipurified fraction induced genotoxicity (in vivo).

miR-1207-5p and miR-1266 suppress gastric cancer growth and invasion by targeting telomerase reverse transcriptase

hTERT is the catalytic subunit of the telomerase complex. Elevated expression of hTERT is associated with the expansion and metastasis of gastric tumor. In this study, we aimed to identify novel tumor suppressor miRNAs that restrain hTERT expression. We began our screen for hTERT-targeting miRNAs with a miRNA microarray. miRNA candidates were further filtered by bioinformatic analysis, general expression pattern in different cell lines, gain-of-function effects on hTERT protein and the potential of these effects to suppress hTERT 3′ untranslated region (3′UTR) luciferase activity. The clinical relevance of two miRNAs (miR-1207-5p and miR-1266) was evaluated by real-time RT-PCR. The effects of these miRNAs on cell growth, cell cycle and invasion of gastric cancer cells were measured with CCK-8, flow cytometry and transwell assays. Finally, the ability of these miRNAs to suppress the transplanted tumors was also investigated. Fourteen miRNAs were identified using a combination of bioinformatics and miRNA microarray analysis. Of these fourteen miRNAs, nine were expressed at significantly lower levels in hTERT-positive cell lines compared with hTERT-negative cell lines and five could downregulate hTERT protein expression. Only miR-1207-5p and miR-1266 interacted with the 3′ UTR of hTERT and the expression levels of these two miRNAs were significantly decreased in gastric cancer tissues. These two miRNAs also inhibited gastric tumor growth in vitro and in vivo. Altogether, miR-1207-5p and miR-1266 were determined to be hTERT suppressors in gastric cancer, and the delivery of these two miRNAs represents a novel therapeutic strategy for gastric cancer treatment.

Synthesis, molecular modeling and biological evaluation of N-benzylidene-2-((5-(pyridin-4-yl)-1,3,4-oxadiazol-2-yl)thio)acetohydrazide derivatives as potential anticancer agents

A series of new 1,3,4-oxadiazole derivatives (6a-6x) containing pyridine and acylhydrazone moieties were synthesized and developed as potential telomerase inhibitors. The bioassay tests demonstrated that compounds 6n, 6o, 6q, 6s and 6t exhibited significant broad-spectrum anticancer activity with IC₅₀ range from 0.76 to 9.59 μM against the four cancer cell lines (HEPG2, MCF7, SW1116 and BGC823). Moreover, all the title compounds were assayed for telomerase inhibition using the TRAP-PCR-ELISA assay. Compound 6s showed the highest anticancer activity with IC₅₀ of 0.76-1.54 μM against the tested cancer cell lines and exhibited the most potent telomerase inhibitory activity with IC₅₀ of 1.18 ± 0.14 μM. The docking simulation was carried out to investigate a possible binding mode of compound 6s into the active site of telomerase (pdb. 3DU6) while the QSAR model was built to check the previous work as well as to introduce new directions.

Targeting heat shock proteins by phenethyl isothiocyanate results in cell-cycle arrest and apoptosis of human breast cancer cells

Heat shock proteins (HSPs) are chaperones for several client proteins involved in transcriptional regulation, signal transduction, and cell cycle control. HSPs (27, 70, and 90) are abundantly expressed in a wide range of cancers and are transcriptionally regulated by heat shock factor (HSF1). Most of the synthetic HSP inhibitors exhibit toxicity, therefore, searching for inhibitors with limited or no toxicity will be of help. The objective of the present study was to determine the effect of natural isothiocyanate (phenethyl isothiocyanate; PEITC) on different HSPs (27, 70, and 90) and HSF1 in 2 breast cancer cell lines, namely breast adenocarcinoma MCF-7 (with wild type p53) and highly metastatic breast cancer cell MDA-MB-231 (with mutated p53). PEITC significantly inhibited the expression of HSPs (particularly HSP 90) and HSF1. Molecular consequences due to HSP inhibition were downregulation of cell-cycle regulatory proteins like Cyclin B1, CDK1, Cdc25C, PLK-1, and upregulation of p21 irrespective of p53 status. These modulations were accompanied by cell-cycle arrest at G2/M phase and apoptosis by activation of caspases 3 and 9. PEITC therefore may be regarded as a potent HSP inhibitor and an antitumor agent in the treatment of breast cancer.

Telomerase regulation: a key to inhibition? (Review)

Telomerase has been recognized as a common factor in most tumor cells, and in turn a distinctive feature with respect to non-malignant cells. This feature has made telomerase a promising target for cancer therapy. Telomerase studies revealed that it is a multi-subunit complex possessing different levels of regulation, including control of expression, phosphorylation state, assembly and transportation to sites of activity. Thus, we emphasize that targeting telomerase expression or activity is not the only way to shorten telomeres, induce cell senescence and apoptosis. Therefore, there are multiple sites capable of allowing the modulation of its enzymatic activity. In the development of strategies based on the regulation of telomerase activity the understanding of the mechanisms regulating their subunits is essential. Based on this, in this review we summarize the current state of knowledge of some regulatory mechanisms of the components of the telomerase complex, and hypothetize their potential therapeutic application against cancer.

Visible light and/or UVA offer a strong amplification of the anti-tumor effect of curcumin

Curcumin, a dietary pigment from the plant Curcuma longa, inhibits cell proliferation and induces apoptosis in different cell lines. The therapeutic benefit is hampered by a very low absorption after trans-dermal or oral application. Therefore, great efforts were undertaken to enhance the effectiveness of curcumin. Recently, it was demonstrated that curcumin offers the described effects also at low concentrations (0.2-1 μg/ml) when applied in combination with UVA or visible light. The efficacy of this combination was shown in human epidermal keratinocytes and in a panel of other cell species in vitro as well as in a xenograft tumor model with A431 tumor cells injected subcutaneously in the flanks of NMRI nude mice in vivo. The treatment of keratinocytes with curcumin and light resulted in the inhibition of cell growth, and in the induction of apoptosis, whereas no toxic cell membrane damage was detectable. The treatment of tumor bearing nude mice with curcumin and visible light resulted in reduced tumor volumes, reduced proliferation rates, and the induction of apoptosis in the tumors. On the molecular level inhibition of extracellular regulated kinases 1/2 and epidermal growth factor receptor was observed which may aid to inhibition of proliferation and induction of apoptosis. This review covers the experiences of the new combination treatment of human tumors.

Protective effects of rutin against potassium bromate induced nephrotoxicity in rats

BACKGROUND

Rutin, a polyphenolic flavonoid, was investigated for its protective effects against the KBrO(3) induced renal injuries in rat.

METHODS

Group I was control (untreated), group II was given saline 0.5 ml/kg bw (0.9% NaCl), group III was administered KBrO(3) (20 mg/kg bw) intragastric twice a week for four weeks. Rutin was administered to group VI (50 mg/kg bw) and Group V (70 mg/kg bw) along with KBrO(3) (20 mg/kg bw) while group VI was given rutin (70 mg/kg bw) alone twice a week for four weeks. Protective effects of rutin on KBrO(3)-induced nephrotoxicity in rats were determined for biochemical parameter of urine, and serum, various antioxidant enzymes, DNA and histopathological damages in kidneys.

RESULTS

The level of urinary red blood cells, leucocytes count, specific gravity, urea, creatinine and urobilinogen was increased (P<0.01) whereas creatinine clearance was reduced. Serum level of protein, albumin, globulin, nitrite, creatinine and blood urea nitrogen (BUN) was significantly increased (P<0.01) by KBrO(3). Marked histopathological lesions, elevated DNA fragmentation and AgNORs count in renal tissues was determined. Activity of antioxidant enzymes; catalase, superoxide dismutase, glutathione peroxidase, glutathione-S-transferase, glutathione reductase, and reduced glutathione contents were decreased (P<0.01) while thiobarbituric acid reactive substances were increased (P<0.01) with KBrO(3) treatment in kidneys. DNA ladder assay was intimately related with the DNA fragmentation assay. Telomerase activity was found positive in the KBrO(3) treated kidneys. Treatment with rutin effectively ameliorated the alterations in the studied parameters of rat. Rutin administration alone to rats did not exhibit any significant change in any of the parameters studied.

CONCLUSION

These results suggest that rutin works as an antioxidant in vivo by scavenging reactive oxygen species and this serves to prevent oxidative renal damage in rat treated with KBrO(3).

Antiglioma activity of curcumin-loaded lipid nanoparticles and its enhanced bioavailability in brain tissue for effective glioblastoma therapy

Glioblastoma, the most aggressive form of brain and central nervous system tumours, is characterized by high rates proliferation, migration and invasion. The major road block in the delivery of drugs to the brain is the blood-brain barrier, along with the expression of various multi-drug resistance (MDR) proteins that cause the efflux of a wide range of chemotherapeutic drugs. Curcumin, a herbal drug, is known to inhibit cellular proliferation, migration and invasion and induce apoptosis of glioma cells. It also has the potential to modulate MDR in glioma cells. However, the greatest challenge in the administration of curcumin stems from its low bioavailability and high rate of metabolism. To circumvent the above pitfalls of curcumin we have developed curcumin-loaded glyceryl monooleate (GMO) nanoparticles (NP) coated with the surfactant Pluronic F-68 and vitamin E D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) for brain delivery. We demonstrated that our curcumin-loaded NPs inhibit cellular proliferation, migration and invasion along with a higher percentage of cell cycle arrest and telomerase inhibition, thus leading to a greater percentage apoptotic cell death in glioma cells compared with native curcumin. An in vivo study demonstrated enhanced bioavailability of curcumin in blood serum and brain tissue when delivered by curcumin-loaded GMO NPs compared with native curcumin in a rat model. Thus, curcumin-loaded GMO NPs can be used as an effective delivery system to overcome the challenges of drug delivery to the brain, providing a new approach to glioblastoma therapy.

Pharmaceutical regulation of telomerase and its clinical potential

Telomeres serve the dual function of protecting chromosomes from genomic instability as well as protecting the ends of chromosomes from DNA damage machinery. The enzyme responsible for telomere maintenance is telomerase, an enzyme capable of reverse transcription. Telomerase activity is typically limited to specific cell types. However, telomerase activation in somatic cells serves as a key step toward cell immortalization and cancer. Targeting telomerase serves as a potential cancer treatment with significant therapeutic benefits. Beyond targeting cancers by inhibiting telomerase, manipulating the regulation of telomerase may also provide therapeutic benefit to other ailments, such as those related to aging. This review will introduce human telomeres and telomerase and discuss pharmacological regulation of telomerase, including telomerase inhibitors and activators, and their use in human diseases.

In silico evaluation of TERT inhibition by anticancer drugs

The activation of telomerase represents an early step in carcinogenesis. Increased telomerase expression in malignant tumors suggests that telomerase inactivation may represent a potential chemotherapeutic target. In this work, existing anticancer drugs were docked against telomerase reverse transcriptase (TERT) using a Lamarckian genetic algorithm (LGA). Autodock's scoring function was applied to each of the molecules in order to identify the inhibitor with the strongest pharmacological action. The structural insights provided by this study regarding binding poses and possible interactions, free energies of binding, and drug scores aided in the identification of potential inhibitory compounds. The ranks of the various ligands investigated were based on the final docked energy values. Among nine selected compounds, vindesine, temsirolimus, and cyclosporine were found to be more potent TERT inhibitors than the standard inhibitor, curcumin.

Apoptotic effects of curcumin on human osteosarcoma U2OS cells

OBJECTIVE

 Curcumin, an active ingredient derived from the rhizome of the plant, Curcuma longa, has antioxidant, anti-inflammatory and anti-cancer activities. The aims of this study were to examine whether curcumin can induce apoptosis in an osteosarcoma cell line.

METHODS

Curcumin-induced apoptosis in human osteosarcoma U2OS cells was investigated using morphological analysis, marked nuclear condensation and fragmentation of chromatin, which were observed by Hoechst 33258 staining and DNA ladder formation. The U2OS cells were treated with or without curcumin. Cell viability was assessed by the 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium (MTT) method. Cell-cycle, apoptosis and apoptosis-related proteins in U2OS cells were evaluated by flow cytometry and western blotting.

RESULTS

Curcumin showed growth inhibitory effects on U2OS cells in a dose-and time-dependent manner, inducing significant G1 arrest and apoptosis in U2OS cells. This curcumin-induced apoptosis in U2OS cells was accompanied by up-regulation of Bax, Bak, and p-Bad and down-regulation of Bcl-2, but no effect on the levels of Bcl-X(L) or Bad proteins was noted. Moreover, curcumin treatment resulted in a significant reduction of mitochondrial membrane potential and increase in the concentrations of mitochondrial cytochrome C and caspase-3.

CONCLUSION

Multiple molecular pathways are involved in curcumin-induced apoptosis of human U2OS cells. These include pro-and anti-apoptotic Bcl-2 family proteins, mitochondrial membrane potential, mitochondrial cytochrome C and caspase-3.

Curcumin sensitizes chemotherapeutic drugs via modulation of PKC, telomerase, NF-κB and HDAC in breast cancer

Background: Several tumor markers are overexpressed in breast cancer. Chemotherapy in breast cancer fails due to resistance to chemotherapeutic drugs. A phytochemical such as curcumin can be used in a therapeutic modality as it elicits anti-tumor effects. Methods: Action of curcumin on the expression of several tumor markers, such as protein kinase C, telomerase, NF-κB and histone deacetylase in MCF-7 (ER positive), MDA-MB-231 (ER negative), MCF-12F (control) and also in mice mammary tumors were investigated. Results: Curcumin downregulated the expression of tumor markers both in vitro and in vivo and sensitized tumor cells to the chemotherapeutic drugs cyclophosphamide and paclitaxel. Discussion: Curcumin may be of considerable value in synergistic therapy of cancer such that the drug dose level could be minimized reducing the associated toxicity.

Investigation into the biological properties of the olive polyphenol, hydroxytyrosol: mechanistic insights by genome-wide mRNA-Seq analysis

The medicinal properties of the leaves and fruit of Olea Europaea (olive tree) have been known since antiquity. Numerous contemporary studies have linked the Mediterranean diet with increased health. In particular, consumption of olive oil has been associated with a decreased risk of cardiovascular disease and certain cancers. Increasingly, there has been an interest in the biological properties of polyphenols, which are minor constituents of olive oil. For example, hydroxytyrosol has been shown to be a potent antioxidant and has anti-atherogenic and anti-cancer properties. The overall aim of this study was to provide insights into the molecular mechanisms of action of hydroxytyrosol using genome-wide mRNA-Seq. Initial experiments were aimed at assessing cytotoxicity, apoptosis and cell cycle effects of hydroxytyrosol in various cell lines. The findings indicated a dose-dependent reduction in cell viability in human erythroleukemic K562 and human keratinocytes. When comparing the viability in parental CEM-CCRF and R100 cells (which overexpress the P-glycoprotein pump), it was determined that the R100 cells were more resistant to effects of hydroxytyrosol suggesting efflux by the multi-drug resistance pump. By comparing the uptake of Hoechst 33342 in the two cell lines that had been pretreated with hydroxytyrosol, it was determined that the polyphenol may have P-glycoprotein-modulating activity. Further, initial studies indicated modest radioprotective effects of relatively low doses of hydroxytyrosol in human keratinocytes. Analysis of mRNA sequencing data identified that treatment of keratinocytes with 20 μM hydroxytyrosol results in the upregulation of numerous antioxidant proteins and enzymes, including heme oxygenase-1 (15.46-fold upregulation), glutaredoxin (1.65) and glutathione peroxidase (1.53). This may account for the radioprotective activity of the compound, and reduction in oxidative stress suggests a mechanism for chemoprevention of cancer by hydroxytyrosol. Alteration in the expression of transcription factors may also contribute to the anti-cancer effects described in numerous studies. These include changes in the expression of STAT3, STAT6, SMAD7 and ETS-1. The telomerase subunit TERT was also found to be downregulated in K562 cells. Overall, our findings provide insights into the mechanisms of action of hydroxytyrosol, and more generally, we identify potential gene candidates for further exploration.

Colorectal cancer: chemopreventive role of curcumin and resveratrol

Colorectal cancer (CRC) is a second leading cause of cancer deaths in the Western world. Currently there is no effective treatment except resection at a very early stage with or without chemotherapy. Of various epithelial cancers, CRC in particular has a potential for prevention, since most cancers follow the adenoma-carcinoma sequence, and the interval between detection of an adenoma and its progression to carcinoma is usually about a decade. However no effective chemopreventive agent except COX-2 inhibitors, limited in their scope due to cardiovascular side effects, have shown promise in reducing adenoma recurrence. To this end, natural agents that can target important carcinogenic pathways without demonstrating discernible adverse effects would serve as ideal chemoprevention agents. In this review, we discuss merits of two such naturally occurring dietary agents-curcumin and resveratrol-for chemoprevention of CRC.

Effects of cadmium on telomerase activity, expressions of TERT, c-myc and P53, and apoptosis of rat hepatocytes

This study investigated the effect of cadmium on the telomerase activity, the expression of TERT, c-myc and p53 and the apoptosis of rat hepatocytes. The rats were administrated 5, 10 and 20 μmol/kg cadmium chloride intraperitoneally and sacrificed 48 h after the initial treatment. The telomerase activity of the rat hepatocytes was measured by the telomeric repeat amplification protocol (TRAP), and apoptosis was detected by flow cytometry. The mRNA expressions of TERT, c-myc and p53 were measured by reverse transcription-polymerase chain reaction (RT-PCR). C-myc and P53 proteins were determined by immunochemistry. The results showed that cadmium chloride increased the hepatocellular telomerase activity in a dose-dependant manner and induced the apoptosis of hepatocytes significantly. The value of relative coefficient between the telomerase activity and the apoptosis rate was 0.9398. RT-PCR revealed that specific bands corresponding to the TERT mRNA, c-myc mRNA, and p53 mRNA were displayed at 185, 342 and 538 bp respectively. Cadmium chloride could substantially increase the mRNA expressions of TERT, c-myc and p53 in rat hepatocytes, as compared with control. Moreover, cadmium chloride at the doses of 5, 10 and 20 μmol/kg could increase the content of P53 protein in rat hepatocytes obviously, but only that at the doses of 10 and 20 μmol/kg substantially promoted the c-myc protein level in rat hepatocytes. Our study herein suggested that cadmium may contribute to the carcinogenesis by activating telomerase, and overexpressing the mRNAs of TERT, c-myc and p53, and causing apoptosis of normal cells.

Curcumin p38-dependently enhances the anticancer activity of valproic acid in human leukemia cells

Valproic acid (VPA) is a broad-spectrum inhibitor of histone deacetylase, which has been used in cancer therapy. Recently, the combination of VPA with other anticancer agents has been considered as a useful and necessary strategy to specifically induce anticancer gene expression. Curcumin (Cur) is a promising natural anticancer agent that can specifically regulate the expression of NF-kappaB, bcl-2, and bax in leukemia cells. However, no literature is available on the anticancer effects of the combination of VPA and Cur. Here we show that this combination significantly increases Sp1 binding, histone H3 and H4 acetylation in the promoter region of bax, but not in that of bcl-2. This specifically up-regulates bax expression and leads to HL-60 cell proliferation arrest, sub-G1 DNA accumulation and cell death. Further studies reveal that Cur specifically activates p38 MAPK, an essential factor for Sp1 binding at the bax promoter. Moreover, both inhibition of p38 MAPK and knock-down of bax expression significantly prevent VPA and Cur-induced proliferation arrest and death in HL-60 cells. These results suggest that Cur could p38-dependently promote bax expression and hence enhance the anticancer activity of VPA in human leukemia cells.