Abrogation of G2/M arrest sensitizes curcumin-resistant hepatoma cells to apoptosis

Defining the mechanisms behind the hepatoprotective properties of curcumin

As a critical cause of human dysfunctionality, hepatic failure leads to approximately two million deaths per year and is on the rise. Considering multiple inflammatory, oxidative, and apoptotic mechanisms behind hepatotoxicity, it urges the need for finding novel multi-targeting agents. Curcumin is a phenolic compound with anti-inflammatory, antioxidant, and anti-apoptotic roles. Curcumin possesses auspicious health benefits and protects against several diseases with exceptional safety and tolerability. This review focused on the hepatoprotective mechanisms of curcumin. The need to develop novel delivery systems of curcumin (e.g., nanoparticles, self-micro emulsifying, lipid-based colloids, solid lipid nanoparticles, cyclodextrin inclusion, phospholipid complexes, and nanoemulsions) is also considered.

Dendrosomal Curcumin Showed Cytotoxic Effects on Breast Cancer Cell Line by Inducing Mitochondrial Apoptosis Pathway and Cell Division Arrest

Background

Mutations in the p53 gene have been linked to the initiation and progression of breast cancer, as well as resistance to chemotherapy. Therefore, the development of novel treatment approaches is essential to combat this disease.

Objectives

This study aimed to evaluate the effects of dendrosomal curcumin (DNC) on the breast cancer cell line MDA-MB231.

Methods

MDA-MB231 cells were treated with 20 μM DNC, and the apoptosis rate and cell proliferation cycles were assessed using flow cytometry. Additionally, after RNA extraction and cDNA synthesis, the expression levels of Lnc-DANCR, EZH2, Noxa, bcl-2, bax, PUMA, p21, and p53 genes were analyzed using RT-PCR. Protein expression levels of P53, P21, Bcl-2, and Bax were evaluated through western blotting.

Results

Dendrosomal curcumin induced apoptosis in MDA-MB231 cells and caused cell cycle arrest at the SubG1 phase. Dendrosomal curcumin treatment downregulated Lnc-DANCR, EZH2, bcl-2, and p53 gene expression, while upregulating bax, Noxa, PUMA, and p21 gene expression in a time-dependent manner. Bax and P21 protein levels were significantly upregulated following DNC treatment, whereas Bcl-2 and P53 protein levels were downregulated in DNC-treated breast cancer cells.

Conclusions

In summary, dendrosomal nanocurcumin demonstrated potent anti-tumor effects against breast cancer cells, suggesting its potential as a therapeutic agent in breast cancer treatment.

Comparative analysis of the molecular mechanism of inhibiting proliferation and migration in cervical cancer HeLa cell by curcumin and resveratrol

Functional experiments indicated that curcumin displayed stronger inhibitory activity on the proliferation of cervical cancer HeLa cells, while resveratrol had a better inhibition effect on migration. Then, we compared the candidate target genes of curcumin and resveratrol in the treatment of cervical cancer through network pharmacology. GO enrichment results showed that curcumin exerted its anti-cervical cancer effect by regulating cell cycle mitosis, whereas resveratrol affected adhesion. Furthermore, the target genes were verified by molecular docking, qRT-PCR, and Western blot, the results revealed that curcumin and resveratrol significantly decreased the expression of CHEK1 and MAPK3, respectively. In conclusion, curcumin inhibited the proliferation of cervical cancer HeLa cells by specifically targeting CHEK1, while resveratrol specifically targeted MAPK3 to supress migration, and the combination of them can synergistically restrain the proliferation and migration of cervical cancer cells.

C0818, a novel curcumin derivative, induces ROS-dependent cytotoxicity in human hepatocellular carcinoma cells in vitro via disruption of Hsp90 function

Heat shock protein 90 (Hsp90) is the most common molecular chaperone that controls the maturation of many oncoproteins critical in tumor development. Hsp90 has been considered as a promising target for cancer treatment, but the clinical significance of Hsp90 and the mechanisms of Hsp90 regulating the tumor-promoting effects in hepatocellular carcinoma (HCC) remain obscure. Previous studies have shown that curcumin, a polyphenol derived from the plant turmeric (Curcuma longa), inhibits tumor growth, which may provide an effective alternative therapy for HCC. Compared to curcumin, a novel derivative of curcumin, 3,5-(E)-Bis(3-methoxy-4-hydroxybenzal)-4-piperidinone hydrochloride (C0818) that is more potent in Hsp90 inhibition and antitumor activity. In this study, we investigated the effect of C0818 on HCC cells in vitro and its relation to Hsp90 inhibition. We showed that C0818 concentration-dependently inhibited the proliferation, the colony formation and induced apoptosis in HepG2 and Sk-Hep-1 cells. C0818 concentration-dependently inhibited DNA synthesis and induced G2/M phase arrest in HepG2 and Sk-Hep-1 cells. We further demonstrated that C0818 induced ROS- and caspase-dependent apoptosis in HCC cells through the mitochondrial-mediated pathway. C0818 induced the degradation of Hsp90 client proteins as RAS, C-Raf, P-C-Raf, Erk, P-ERK, MEK, P-MEK, Akt and P-Akt, which led to subsequent inhibition of the RAS/RAF/MEK/ERK and PI3K/AKT pathways. We revealed that C0818 could inhibit the binding of Hsp90 with its clients without affecting their transcription, which subsequently induced the degradation of Hsp90 clients by the proteasome rather than the lysosome. These results are of potential importance for elucidating a novel Hsp90 inhibitor targeting HCC.

Coralyne Radiosensitizes A549 Cells by Upregulation of CDKN1A Expression to Attenuate Radiation Induced G2/M Block of the Cell Cycle

Coralyne is a synthetic analog of berberine related to protoberberine-isoquinoline alkaloids. Isoquinoline derivatives and analogs are renowned as potent radiosensitizers with potential medical application. In the present study, we investigated the effect of coralyne on the cell death, cytoskeletal changes and cell cycle progression of irradiated A549 cells. A clonogenic assay revealed that coralyne pretreatment decreased the viability of A549 cells in a time- and dose-dependent manner. Moreover, exposure to coralyne and ionizing radiation (IR) markedly altered the filamentous actin cytoskeletal architecture and integrin-β binding sites of A549 cells. Treatment with 1–25 µM coralyne in combination with 2 Gy of IR significantly reduced the percentage of cells in G2/M phase compared with 2 Gy IR alone. These results indicate that coralyne is a potent radiosensitizing agent that may find an application in medicine.

Potential Role of Curcumin and Its Nanoformulations to Treat Various Types of Cancers

Cancer is a major burden of disease globally. Each year, tens of millions of people are diagnosed with cancer worldwide, and more than half of the patients eventually die from it. Significant advances have been noticed in cancer treatment, but the mortality and incidence rates of cancers are still high. Thus, there is a growing research interest in developing more effective and less toxic cancer treatment approaches. Curcumin (CUR), the major active component of turmeric (Curcuma longa L.), has gained great research interest as an antioxidant, anticancer, and anti-inflammatory agent. This natural compound shows its anticancer effect through several pathways including interfering with multiple cellular mechanisms and inhibiting/inducing the generation of multiple cytokines, enzymes, or growth factors including IκB kinase β (IκKβ), tumor necrosis factor-alpha (TNF-α), signal transducer, and activator of transcription 3 (STAT3), cyclooxygenase II (COX-2), protein kinase D1 (PKD1), nuclear factor-kappa B (NF-κB), epidermal growth factor, and mitogen-activated protein kinase (MAPK). Interestingly, the anticancer activity of CUR has been limited primarily due to its poor water solubility, which can lead to low chemical stability, low oral bioavailability, and low cellular uptake. Delivering drugs at a controlled rate, slow delivery, and targeted delivery are other very attractive methods and have been pursued vigorously. Multiple CUR nanoformulations have also been developed so far to ameliorate solubility and bioavailability of CUR and to provide protection to CUR against hydrolysis inactivation. In this review, we have summarized the anticancer activity of CUR against several cancers, for example, gastrointestinal, head and neck, brain, pancreatic, colorectal, breast, and prostate cancers. In addition, we have also focused on the findings obtained from multiple experimental and clinical studies regarding the anticancer effect of CUR in animal models, human subjects, and cancer cell lines.

Thymol induces mitochondrial pathway-mediated apoptosis via ROS generation, macromolecular damage and SOD diminution in A549 cells

BACKGROUND

Thymol is a monoterpene phenol found in thyme species plants. The present study was carried out to investigate the effect of thymol and its molecular mechanism on non-small lung cancer (A549) cells.

METHODS

The cytotoxic effect of thymol on A549 cells was assessed via MTT assay. ROS production, macromolecular damage, apoptosis were determined using DCF-DA, PI, AO/EtBr stains, respectively. ROS-dependent effect of thymol was confirmed using NAC. The expression of caspase-9, Bcl-2, Bax and cell cycle profile was analyzed via western blot and FACS, respectively.

RESULTS

The antiproliferative effect of thymol on A549 cells was found to be both dose and time dependent with IC₅₀ values of 112 μg/ml (745 μM) at 24 h. Thymol treatment favored apoptotic cell death and caused G0/G1 cell cycle arrest. It mediated cellular and nuclear morphological changes, phosphatidylserine translocation, and mitochondrial membrane depolarization. Additionally, upregulation of Bax, downregulation of Bcl-2, and apoptotic fragmented DNA were also observed. Thymol induced ROS by reducing the SOD level which was confirmed via in vitro and in silico analysis. Furthermore, the levels of lipid peroxides and protein carbonyl content were elevated in thymol-treated groups. Notably, N-acetyl cysteine pretreatment reversed the efficacy of thymol on A549 cells. Moreover, thymol-treated human PBMC cells did not show any significant cytotoxicity.

CONCLUSION

Overall, our results confirmed that thymol can act as a safe and potent therapeutic agent to treat NSCLC.

Anti-cancer properties of specific Chinese herbal medicines for hepatocellular carcinoma treatment

AIMS

This essay explores the anti-cancer activity of specific Chinese herbal medicines to clarify how effective Chinese herbal medicine is used for handling hepatocellular carcinoma.

METHODS

Literature form publica domain were studied and an analysis of anti-cancer activity of specific Chinese herbal medicines is presented in this review.

RESULTS

Hepatocellular carcinoma is one of the most dangerous malignant tumors in the world. The operative diagnosis of liver cancer remains a significant challenge. Although surgery tissue resection is encouraging, a high risk of recurrence and metastasis, illustrating disease-related mortality is desperately required to enhance postoperative preventive and therapeutic clinical procedures. The almost only effective clinical intervention seems to be developing advanced targeted therapies such as sorafenib for hepatocellular carcinoma patients, but there is little research in this field. Because their preventative/therapeutic properties strengthen Chinese herbal medicinal compounds, they are deemed relevant to the treatment of hepatocellular carcinoma. Conclusion: Chinese herbal medicine derivates provide multifaceted, orientated and orchestrated therapy, making it an ideal candidate for inhibiting hepatocellular tumor production and metastasis.

Pentagamavunon-1 (PGV-1) inhibits ROS metabolic enzymes and suppresses tumor cell growth by inducing M phase (prometaphase) arrest and cell senescence

We previously showed that curcumin, a phytopolyphenol found in turmeric (Curcuma longa), targets a series of enzymes in the ROS metabolic pathway, induces irreversible growth arrest, and causes apoptosis. In this study, we tested Pentagamavunon-1 (PGV-1), a molecule related to curcumin, for its inhibitory activity on tumor cells in vitro and in vivo. PGV-1 exhibited 60 times lower GI₅₀ compared to that of curcumin in K562 cells, and inhibited the proliferation of cell lines derived from leukemia, breast adenocarcinoma, cervical cancer, uterine cancer, and pancreatic cancer. The inhibition of growth by PGV-1 remained after its removal from the medium, which suggests that PGV-1 irreversibly prevents proliferation. PGV-1 specifically induced prometaphase arrest in the M phase of the cell cycle, and efficiently induced cell senescence and cell death by increasing intracellular ROS levels through inhibition of ROS-metabolic enzymes. In a xenograft mouse model, PGV-1 had marked anti-tumor activity with little side effects by oral administration, whereas curcumin rarely inhibited tumor formation by this administration. Therefore, PGV-1 is a potential therapeutic to induce tumor cell apoptosis with few side effects and low risk of relapse.

Counteracting survival functions of EBNA3C in Epstein-Barr virus (EBV)-driven lymphoproliferative diseases by combination of SAHA and bortezomib

Combination of suberoylanilide hydroxamic acid (SAHA) and bortezomib (SAHA/bortezomib) was shown to synergistically induce killing of lymphoblastoid cell lines (LCL) and Burkitt lymphoma (BL) of type III or Wp-restricted latency, both of which express EBNA3A, -3B and -3C proteins. We hypothesize that SAHA/bortezomib can counteract the survival functions conferred by the EBNA3 proteins. We tested the effect of SAHA/bortezomib on the survival of BL cell lines containing EBNA3A, -3B or -3C knockout EBV with or without the respective revertant EBNA3 genes. Isobologram analysis showed that SAHA/bortezomib induced significantly greater synergistic killing of EBNA3C-revertant cells when compared with EBNA3C-knockout cells. Such differential response was not observed in either EBNA3A or -3B revertant versus their knockout pairs. Interestingly, EBNA3C-knockout cells showed significant G2/M arrest whilst EBNA3C-revertant cells and LCLs escaped G2/M arrest induced by SAHA/bortezomib and became more susceptible to the induction of apoptosis. In parallel, SAHA/bortezomib induced stronger expression of p21^WAF1 but weaker expression of p-cdc25c, an M-phase inducer phosphatase, in EBNA3C-expressing cells when compared with EBNA3C-knockout cells. SAHA/bortezomib also induced greater growth suppression of EBNA3C-expressing xenografts (EBNA3C-revertant and LCL) than that of EBNA3C-knockout xenografts in SCID mice. In conclusion, our data showed that SAHA/bortezomib could synergistically induce killing of BL and LCL through counteracting the survival functions of EBNA3C, providing a strong basis for clinical testing of this drug combination in patients with EBV-associated lymphoproliferative diseases.

Yellow and green pigments from Calophyllum inophyllum L. seed oil induce cell death in colon and lung cancer cells

Natural compounds have been candidates for anticancer medicine over the last 20 years. During the process of isolating seed oil from Calophyllum inophyllum L., yellow and green pigments containing multiple compounds with an aromatic structure were identified. High-performance liquid chromatography and nuclear magnetic resonance analysis of these pigments revealed that the compounds present were identical, but the concentration of the compounds was different. Treatment with the pigments was able to induce the death of DLD-1 human colon cancer cells and increase the percentage of the cells in the sub-G₁ and sub-G₂/M phases in a dose-dependent manner. Additionally, the pigments were able to exhibit cytotoxic activity on A549 and H1975 human non-small cell lung cancer (NSCLC) cell lines at 24 h, with half-maximal inhibitory concentrations (IC₅₀) values of 0.1206 and 0.0676%, respectively for green pigments, and 0.0434 and 0.0501%, respectively for yellow pigments. Furthermore, a decrease in IC₅₀ value was associated with an increase in the duration of treatment. However, a sharp decrease in IC₅₀ value of the yellow pigment was observed for H1975 cells at 48 h and for A549 cells at 72 h compared with no change in IC₅₀ value for the green pigment with time, suggesting that the pigments function and induce cell death differently in the two cell lines. An investigation was performed into the synergistic effect of the green pigment and gefitinib (Iressa^®, ZD1839), which is a selective epidermal growth factor receptor-tyrosine kinase inhibitor to block growth factor-mediated cell proliferation. The combination of the green pigment and gefitinib resulted in an enhancement of the decrease in viability of A549 and H1975 cells compared with treatment with gefitinib alone, which suggested that treatment with the green pigments was able to enhance the sensitivity of NSCLC cells to gefitinib. In conclusion, these pigments may be considered for development as anti-colon cancer agents.

Virus-host interplay in hepatitis B virus infection and epigenetic treatment strategies

Worldwide, chronic hepatitis B virus (HBV) infection is a major health problem and no cure exists. Importantly, hepatocyte intrusion by HBV particles results in a complex deregulation of both viral and host cellular genetic and epigenetic processes. Among the attempts to develop novel therapeutic approaches against HBV infection, several options targeting the epigenomic regulation of HBV replication are gaining attention. These include the experimental treatment with 'epidrugs'. Moreover, as a targeted approach, the principle of 'epigenetic editing' recently is being exploited to control viral replication. Silencing of HBV by specific rewriting of epigenetic marks might diminish viral replication, viremia, and infectivity, eventually controlling the disease and its complications. Additionally, epigenetic editing can be used as an experimental tool to increase our limited understanding regarding the role of epigenetic modifications in viral infections. Aiming for permanent epigenetic reprogramming of the viral genome without unspecific side effects, this breakthrough may pave the roads for an ambitious technological pursuit: to start designing a curative approach utilizing manipulative molecular therapies for viral infections in vivo.

Antiangiogenic and antihepatocellular carcinoma activities of the Juniperus chinensis extract

Background

To identify a novel therapeutic agent for hepatocellular carcinoma (HCC), for which no promising therapeutic agent exists, we screened a panel of plants and found that Juniperus chinensis exhibited potential antiangiogenic and anti-HCC activities. We further investigated the antiangiogenic and anti-HCC effects of the active ingredient of J. chinensis extract, CBT-143-S-F6F7, both in vitro and in vivo.

Methods

A tube formation assay conducted using human umbilical vein endothelial cells (HUVECs) was first performed to identify the active ingredient of CBT-143-S-F6F7. A series of angiogenesis studies, including HUVEC migration, Matrigel plug, and chorioallantoic membrane (CAM) assays, were then performed to confirm the effects of CBT-143-S-F6F7 on angiogenesis. The effects of CBT-143-S-F6F7 on tumor growth were investigated using a subcutaneous and orthotopic mouse model of HCC. In vitro studies were performed to investigate the effects of CBT-143-S-F6F7 on the cell cycle and apoptosis in HCC cells. Moreover, protein arrays for angiogenesis and apoptosis were used to discover biomarkers that may be influenced by CBT-143-S-F6F7. Finally, nuclear magnetic resonance analysis was conducted to identify the compounds of CBT-143-S-F6F7.

Results

CBT-143-S-F6F7 showed significantly antiangiogenic activity in various assays, including HUVEC tube formation and migration, CAM, and Matrigel plug assays. In in vivo studies, gavage with CBT-143-S-F6F7 significantly repressed subcutaneous Huh7 tumor growth in severe combined immunodeficient (SCID) mice, and prolonged the survival of orthotopic Huh7 tumor-bearing SCID mice (a 40 % increase in median survival duration compared with the vehicle-treated mice). Immunohistochemical staining of subcutaneous Huh7 tumors in CBT-143-S-F6F7-treated mice showed a significantly decrease in the cell cycle regulatory protein cyclin D1, cellular proliferation marker Ki-67, and endothelial marker CD31. CBT-143-S-F6F7 caused arrest of the G2/M phase and induced Huh7 cell apoptosis, possibly contributing to the inhibition of HCC tumors. Protein array analysis revealed that several angiogenic and antiapoptotic factors were suppressed in CBT-143-S-F6F7-treated Huh7 cells. Finally, five compounds from CBT-143-S-F6F7 were identified.

Conclusions

According to these results, we report for the first time the antiangiogenic and anti-HCC activities of CBT-143-S-F6F7, the active fractional extract of J. chinensis. We believe that CBT-143-S-F6F7 warrants further evaluation as a new anti-HCC drug.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1250-6) contains supplementary material, which is available to authorized users.

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.

Curcumin Suppresses Phthalate-Induced Metastasis and the Proportion of Cancer Stem Cell (CSC)-like Cells via the Inhibition of AhR/ERK/SK1 Signaling in Hepatocellular Carcinoma

Recent evidence indicating that phthalates promote cancer development, including cell proliferation, migration, and invasion, has raised public health concerns. Here, we show that bis(2-ethylhexyl) phthalate promotes the migration, invasion, and epithelial-mesenchymal transition of hepatocellular carcinoma cells. In addition, bis(2-ethylhexyl) phthalate increased the proportion of cancer stem cell (CSC)-like cells and stemness maintenance in vitro as well as tumor growth and metastasis in vivo. The various activities of curcumin, including anticancer, anti-inflammation, antioxidation, and immunomodulation, have been investigated extensively. Curcumin suppressed phthalate-induced cell migration, invasion, and epithelial-mesenchymal transition, decreased the proportion of CSC-like cells in hepatocellular carcinoma cell lines in vitro, and inhibited tumor growth and metastasis in vivo. We also reveal that curcumin suppressed phthalate-induced migration, invasion, and CSC-like cell maintenance through inhibition of the aryl hydrocarbon receptor/ERK/SK1/S1P3 signaling pathway. Our results suggest that curcumin may be a potential antidote for phthalate-induced cancer progression.

Current Status of Herbal Medicines in Chronic Liver Disease Therapy: The Biological Effects, Molecular Targets and Future Prospects

Chronic liver dysfunction or injury is a serious health problem worldwide. Chronic liver disease involves a wide range of liver pathologies that include fatty liver, hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. The efficiency of current synthetic agents in treating chronic liver disease is not satisfactory and they have undesirable side effects. Thereby, numerous medicinal herbs and phytochemicals have been investigated as complementary and alternative treatments for chronic liver diseases. Since some herbal products have already been used for the management of liver diseases in some countries or regions, a systematic review on these herbal medicines for chronic liver disease is urgently needed. Herein, we conducted a review describing the potential role, pharmacological studies and molecular mechanisms of several commonly used medicinal herbs and phytochemicals for chronic liver diseases treatment. Their potential toxicity and side effects were also discussed. Several herbal formulae and their biological effects in chronic liver disease treatment as well as the underlying molecular mechanisms are also summarized in this paper. This review article is a comprehensive and systematic analysis of our current knowledge of the conventional medicinal herbs and phytochemicals in treating chronic liver diseases and on the potential pitfalls which need to be addressed in future study.

Synergistic effect of cucurbitacin B in combination with curcumin via enhancing apoptosis induction and reversing multidrug resistance in human hepatoma cells

Cucurbitacin B is a plant-derived tetracyclic triterpenoid, which has been used for a variety of cancers, especially human hepatoma. Curcumin, isolated from a plant Curcuma longa also has found the anti-tumor property. In the present study, the synergistic effect of cucurbitacin B and curcumin was studied on BEL7402/5-Fu cells in vitro and BEL7402 tumor-bearing mice in vivo. The synergistic anticancer activity of these two compounds involves the two mechanisms. Firstly, curcumin synergistically enhanced the apoptosis of BEL7402/5-Fu cells induced by cucurbitacin B in the optimal mass ratio of 2:1 (cucurbitacin B:curcumin). The mechanism may result from the cell arresting in different phases of cell cycles and the apoptotic change of ultrastructure in BEL7402/5-Fu cells. Secondly, curcumin reversed the multidrug resistance (MDR) caused by cucurbitacin B in the optimized concentration of 67.9μM (25μg/ml). The mechanism was associated with the P-gp reduction, ΔΨm collapse and mitochondrial colocalization in BEL7402/5-Fu cells. The findings were consistent with the changes of the body weight and tumor volume, caspase3 activation and ATP down-regulation in vivo. In conclusion, cucurbitacin B in the combination with curcumin could serve as a novel, promising approach for human hepatoma.

Targeting miR-21 sensitizes Ph+ ALL Sup-b15 cells to imatinib-induced apoptosis through upregulation of PTEN

Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL) cells are insensitive to BCR-ABL tyrosine kinase inhibitor imatinib, the underlying mechanisms remain largely unknown. Here, we showed that imatinib treatment induced significant upregulation of miR-21 and downregulation of PTEN in Ph+ ALL cell line Sup-b15. Transient inhibition of miR-21 resulted in increased apoptosis, PTEN upregulation and AKT dephosphorylation, whereas ectopic overexpression of miR-21 further conferred imatinib resistance. Furthermore, knockdown of PTEN protected the cells from imatinib-induced apoptosis achieved by inhibition of miR-21. Additionally, PI3K inhibitors also notably enhanced the effects of imatinib on Sup-b15 cells and primary Ph+ ALL cells similar to miR-21 inhibitor. Therefore, miR-21 contributes to imatinib resistance in Ph+ ALL cells and antagonizing miR-21 demonstrates therapeutic potential by sensitizing the malignancy to imatinib therapy.

Roles of signaling pathways in drug resistance, cancer initiating cells and cancer progression and metastasis

The EGFR/PI3K/PTEN/Akt/mTORC pathway plays prominent roles in malignant transformation, prevention of apoptosis, drug resistance, cancer initiating cells (CICs) and metastasis. The expression of this pathway is frequently altered in breast and other cancers due to mutations at or aberrant expression of: HER2, EGFR1, PIK3CA, and PTEN as well as other oncogenes and tumor suppressor genes. miRs and epigenetic mechanisms of gene regulation are also important events which regulate this pathway. In some breast cancer cases, mutations at certain components of this pathway (e.g., PIK3CA) are associated with a better prognosis than breast cancers lacking these mutations. The expression of this pathway has been associated with CICs and in some cases resistance to therapeutics. We will review the effects of activation of the EGFR/PI3K/PTEN/Akt/mTORC pathway primarily in breast cancer and development of drug resistance. The targeting of this pathway and other interacting pathways will be discussed as well as clinical trials with novel small molecule inhibitors as well as established drugs that are used to treat other diseases. In this manuscript, we will discuss an inducible EGFR model (v-ERB-B:ER) and its effects on cell growth, cell cycle progression, activation of signal transduction pathways, prevention of apoptosis in hematopoietic, breast and prostate cancer models.

Wedelia chinensis inhibits nasopharyngeal carcinoma CNE-1 cell growth by inducing G2/M arrest in a Chk1-dependent pathway

Although Wedelia chinensis, an herb in traditional Chinese medicine, has been widely used for the treatment of inflammation, the effects of W. chinensis on cancer cell growth and the related molecular mechanisms behind these effects have largely remained unexplored to date. In the present study, W. chinensis plant extracts were obtained using either ethanol (E), petroleum ether (PE), ethyl acetate (EA) or butyl alcohol (BA). Then, extracts were examined for bioactivity in vitro via MTT assay in five human cancer cell lines. Our results showed that one subfraction of the EA extract (EA6) was cytotoxic to nasopharyngeal carcinoma (NPC) CNE-1 cells, among all cell lines evaluated. Treatment of CNE-1 cells with EA6 resulted in significant G2/M cell cycle arrest and modest apoptosis. EA6 induced Chk1 activation and inhibition of Chk1 in CNE-1 cells by RNA interference (RNAi) markedly abrogated EA6-mediated G2/M arrest and abolished EA6-induced cytotoxicity. EA6 treatment resulted in notable reduction of c-myc expression in CNE-1 cells, whereas silencing Chk1 inhibited such effects of EA6. Our results indicate that Chk1 is a novel molecular target of EA6 in NPC cells and also suggest an intervention strategy for NPC by EA6 exploring its molecular mechanisms of action.

Characterization of CurcuEmulsomes: nanoformulation for enhanced solubility and delivery of curcumin

BACKGROUND

Curcumin is a polyphenolic compound isolated from the rhizomes of the plant Curcuma longa and shows intrinsic anti-cancer properties. Its medical use remains limited due to its extremely low water solubility and bioavailability. Addressing this problem, drug delivery systems accompanied by nanoparticle technology have emerged. The present study introduces a novel nanocarrier system, so-called CurcuEmulsomes, where curcumin is encapsulated inside the solid core of emulsomes.

RESULTS

CurcuEmulsomes are spherical solid nanoparticles with an average size of 286 nm and a zeta potential of 37 mV. Encapsulation increases the bioavailability of curcumin by up to 10,000 fold corresponding to a concentration of 0.11 mg/mL. Uptaken by HepG2 human liver carcinoma cell line, CurcuEmulsomes show a significantly prolonged biological activity and demonstrated therapeutic efficacy comparable to free curcumin against HepG2 in vitro - with a delay in response, as assessed by cell viability, apoptosis and cell cycle studies. The delay is attributed to the solid character of the nanocarrier prolonging the release of curcumin inside the HepG2 cells.

CONCLUSIONS

Incorporation of curcumin into emulsomes results in water-soluble and stable CurcuEmulsome nanoformulations. CurcuEmulsomes do not only successfully facilitate the delivery of curcumin into the cell in vitro, but also enable curcumin to reach its effective concentrations inside the cell. The enhanced solubility of curcumin and the promising in vitro efficacy of CurcuEmulsomes highlight the potential of the system for the delivery of lipophilic drugs. Moreover, high degree of compatibility, prolonged release profile and tailoring properties feature CurcuEmulsomes for further therapeutic applications in vivo.

Molecular mechanisms behind anti-cancer effects of curcumin in hepatocellular carcinoma

Primary liver cancer, also known as hepatocellular carcinoma (HCC), is one of the most lethal cancers worldwide. Most HCC cases are reported in the developing countries in Asia and Africa. Viral hepatitis, alcoholism as well as dietary carcinogens, such as aflatoxins and nitrosoamines, contribute to HCC. Surgical resection is the best treatment for early HCC, and Chinese medicine is one of the main measures for the treatment of advanced HCC. Numerous studies show that curcumin has anti-cancer, anti-oxidant and anti-inflammatory properties. This article will discuss the mechanisms behind anti-cancer effects of curcumin in HCC.

Chinese herbal medicine-derived compounds for cancer therapy: a focus on hepatocellular carcinoma

ETHNOPHARMACOLOGICAL RELEVANCE

Hepatocellular carcinoma (HCC) as the major histological subtype of primary liver cancer remains one of the most common malignancies worldwide. Due to the complicated molecular pathogenesis of HCC, the option for effective systemic treatment is quite limited. There exists a critical need to explore and evaluate possible alternative strategies for effective control of HCC. With a long history of clinical use, Chinese herbal medicine (CHM) is emerging as a noticeable choice for its multi-level, multi-target and coordinated intervention effects against HCC. With the aids of phytochemistry and molecular biological approaches, in the past decades many CHM-derived compounds have been carefully studied through both preclinical and clinical researches and have shown great potential in novel anti-HCC natural product development. The present review aimed at providing the most recent developments on anti-HCC compounds derived from CHM, especially their underlying pharmacological mechanisms.

MATERIALS AND METHODS

A systematic search of anti-HCC compounds from CHM was carried out focusing on literatures published both in English (PubMed, Scopus, Web of Science and Medline) and in Chinese academic databases (Wanfang and CNKI database).

RESULTS

In this review, we tried to give a timely and comprehensive update about the anti-HCC effects and targets of several representative CHM-derived compounds, namely curcumin, resveratrol, silibinin, berberine, quercetin, tanshinone II-A and celastrol. Their mechanisms of anti-HCC behaviors, potential side effects or toxicity and future research directions were discussed.

CONCLUSION

Herbal compounds derived from CHM are of much significance in devising new drugs and providing unique ideas for the war against HCC. We propose that these breakthrough findings may have important implications for targeted-HCC therapy and modernization of CHM.

Curcumin suppresses multiple DNA damage response pathways and has potency as a sensitizer to PARP inhibitor

Inhibitors of poly(ADP-ribose) polymerase (PARP) are promising anticancer drugs, particularly for the treatment of tumors deficient in the DNA damage response (DDR). However, it is challenging to design effective therapeutic strategies for use of these compounds against cancers without DDR deficiencies. In this context, combination therapies in which PARP inhibitors are used alongside DDR inhibitors have elicited a great deal of interest. Curcumin, a component of turmeric (Curcuma longa), has been tested in clinical studies for its chemosensitizing potential; however, the mechanisms of chemosensitization by curcumin have not been fully elucidated. This study demonstrates that curcumin suppresses three major DDR pathways: non-homologous end joining (NHEJ), homologous recombination (HR) and the DNA damage checkpoint. Curcumin suppresses the histone acetylation at DNA double-strand break (DSB) sites by inhibiting histone acetyltransferase activity, thereby reducing recruitment of the key NHEJ factor KU70/KU80 to DSB sites. Curcumin also suppresses HR by reducing expression of the BRCA1 gene, which regulates HR, by impairing histone acetylation at the BRCA1 promoter. Curcumin also inhibits ataxia telangiectasia and Rad3-related protein (ATR) kinase (IC50 in vitro = 493 nM), resulting in impaired activation of ATR-CHK1 signaling, which is necessary for HR and the DNA damage checkpoint pathway. Thus, curcumin suppresses three DDR pathways by inhibiting histone acetyltransferases and ATR. Concordantly, curcumin sensitizes cancer cells to PARP inhibitors by enhancing apoptosis and mitotic catastrophe via inhibition of both the DNA damage checkpoint and DSB repair. Our results indicate that curcumin is a promising sensitizer for PARP inhibitor-based therapy.

Hepatitis C virus core protein down-regulates p21(Waf1/Cip1) and inhibits curcumin-induced apoptosis through microRNA-345 targeting in human hepatoma cells

Background

Hepatitis C virus (HCV) has been reported to regulate cellular microRNAs. The HCV core protein is considered to be a potential oncoprotein in HCV-related hepatocellular carcinoma, but HCV core-modulated cellular microRNAs are unknown. The HCV core protein regulates p21^Waf1/Cip1 expression. However, the mechanism of HCV core-associated p21^Waf1/Cip1 regulation remains to be further clarified. Therefore, we attempted to determine whether HCV core-modulated cellular microRNAs play an important role in regulating p21^Waf1/Cip1 expression in human hepatoma cells.

Methods

Cellular microRNA profiling was investigated in core-overexpressing hepatoma cells using TaqMan low density array. Array data were further confirmed by TaqMan real-time qPCR for single microRNA in core-overexpressing and full-length HCV replicon-expressing cells. The target gene of microRNA was examined by reporter assay. The gene expression was determined by real-time qPCR and Western blotting. Apoptosis was examined by annexin V-FITC apoptosis assay. Cell cycle analysis was performed by propidium iodide staining. Cell proliferation was analyzed by MTT assay.

Results

HCV core protein up- or down-regulated some cellular microRNAs in Huh7 cells. HCV core-induced microRNA-345 suppressed p21^Waf1/Cip1 gene expression through targeting its 3′ untranslated region in human hepatoma cells. Moreover, the core protein inhibited curcumin-induced apoptosis through p21^Waf1/Cip1-targeting microRNA-345 in Huh7 cells.

Conclusion and Significance

HCV core protein enhances the expression of microRNA-345 which then down-regulates p21^Waf1/Cip1 expression. It is the first time that HCV core protein has ever been shown to suppress p21^Waf1/Cip1 gene expression through miR-345 targeting.

Elevated snoRNA biogenesis is essential in breast cancer

Hyperactive ribosomal biogenesis is widely observed in cancer, which has been partly attributed to the increased rDNA transcription by Pol I in cancer. However, whether small nucleolar RNAs (snoRNAs), a class of non-coding RNAs crucial in ribosomal RNA (rRNA) maturation and functionality, are involved in cancer remains elusive. We report that snoRNAs and fibrillarin (FBL, an enzymatic small nucleolar ribonucleoprotein, snoRNP) are frequently overexpressed in both murine and human breast cancer as well as in prostate cancers, and significantly, that this overexpression is essential for tumorigenicity in vitro and in vivo. We demonstrate that when the elevated snoRNA pathway is suppressed, the tumor suppressor p53 can act as a sentinel of snoRNP perturbation, the activation of which mediates the growth inhibitory effect. On the other hand, high level of FBL interferes with the activation of p53 by stress. We further show that p53 activation by FBL knockdown is not only regulated by the ribosomal protein-MDM2-mediated protein stabilization pathway, but also by enhanced PTB-dependent, cap-independent translation. Together, our data uncover an essential role of deregulated snoRNA biogenesis in tumors and a new mechanism of nucleolar modulation of p53.

Curcumin induces FasL-related apoptosis through p38 activation in human hepatocellular carcinoma Huh7 cells

AIM

The aim of this study is to explore the underlying molecular mechanism of curcumin-induced apoptosis in human hepatocellular carcinoma (HCC) Huh7 cells.

MAIN METHODS

Fas and FasL mRNA expression was analyzed by reverse transcription PCR. Western blot was applied to detect the protein expression of Bcl-2 family members, MAPK family members, c-Jun, c-Fos, ATF-2, caspase-3, PARP, TNF receptor family members and the respective ligands. Apoptotic cells were assayed with annexin V/PI double staining and flow cytometry.

KEY FINDINGS

Curcumin treatment resulted in a fast and significant increase of Fas and Fas ligand (FasL) along with activation of caspase-3 and cleavage of PARP in Huh7 cells. Inhibition of caspase-3 activity by the specific inhibitor Z-DEVD-FMK rescued Huh7 cells from curcumin-induced apoptosis. Neutralization of FasL significantly protected the cells from curcumin-induced caspase-3 activation and apoptosis in a dose-dependent manner. Moreover, p38 was rapidly activated in response to curcumin, and inactivation of p38 by pharmacologic inhibitor SB203580 dramatically suppressed curcumin-induced FasL expression and apoptosis.

SIGNIFICANCE

Our results demonstrated that curcumin induces apoptosis through p38-denpendent up-regulation of FasL in Huh7 cells.

Zygotic G2/M cell cycle arrest induced by ATM/Chk1 activation and DNA repair in mouse embryos fertilized with hydrogen peroxide-treated epididymal mouse sperm

Human sperm cryopreservation for assisted reproduction is compromised by ROS-induced sperm cryodamage. Our previous model study in which mouse sperm were treated with H₂O₂ to simulate sperm DNA-damage caused by cryopreservation-induced ROS have discovered that mouse embryos fertilized with treated sperm showed a delay in cleavage that might be associated with cell cycle arrest. The DNA-damage checkpoint pathway underlying the delay remained elusive. Moreover, our previous study have also indicated that γH2AX, the DNA-damage repair marker, was functional in mouse embryos similarly fertilized, but the completeness and correctness are unknown and warrant more studies because insufficiency of completeness and correctness of DNA repair would otherwise trigger apoptosis. Based on the aforementioned model, we used embryo culture, inverted microscope, BrdU incorporation and immunofluorescence to explore the cell cycle phase that arrest occurred and the underlying DNA-damage checkpoint pathway in mouse zygotes fertilized with H₂O₂-treated sperm. We also adopted Tunel to investigate the apoptosis of mouse embryos similarly fertilized at different developmental stages to testify the completeness and correctness of sperm-derived DNA-damage repair. We found G2/M cell cycle arrest in zygotes fertilized with H₂O₂-treated sperm. ATM (pSer-1981) and Chk1 (pSer-345) activations, rather than ATR (pSer-428) and Chk2 (pThr-68), were detected in zygotes of the treated group. The apoptosis of embryos of different developmental stages of the treated group weren't different from those of the untreated group. In conclusions, ATM (pSer-1981)-Chk1 (pSer-345) cascade might have mediated G2/M cell cycle arrest and allowed time to facilitate sperm-derived DNA-damage repair in mouse zygotes fertilized with oxygen-stressed sperm, and the DNA-damage repair might be effective.

14-3-3σ mediates G2-M arrest produced by 5-aza-2'-deoxycytidine and possesses a tumor suppressor role in endometrial carcinoma cells

OBJECTIVES

To determine the effect of 5-aza-2'-deoxycytidine (DAC) on human endometrial carcinoma cell (HECC) oncogenicity and demonstrate a molecular mechanism by which DAC modulates HECC oncogenicity.

METHODS

The effect of DAC was tested on HECC RL95-2, AN3, Ishikawa and ECC1 cells. The role of 14-3-3σ on HECC oncogenicity in response to DAC treatment was evaluated in RL95-2 and AN3 cells after forced expression or silencing of 14-3-3σ gene expression.

RESULTS

Treatment of HECC with DAC produced non-cytotoxic cell growth inhibition and G2/M cell cycle arrest. This effect was strongly correlated with increased expression of p21 and 14-3-3σ. Silencing of 14-3-3σ induced cellular proliferation and reduced the effect of DAC on cell cycle arrest in G2/M phases. Conversely, forced expression of 14-3-3σ showed the opposite effect. Furthermore, forced expression of 14-3-3σ in human endometrial cell lines reduced cell growth and colony formation.

CONCLUSIONS

We suggest that 14-3-3σ in HECC suppresses cell proliferation and mediates DAC induced G2/M arrest and inhibition of cell proliferation in HECC.

MicroRNA-26a/b and their host genes cooperate to inhibit the G1/S transition by activating the pRb protein

The functional association between intronic miRNAs and their host genes is still largely unknown. We found that three gene loci, which produced miR-26a and miR-26b, were embedded within introns of genes coding for the proteins of carboxy-terminal domain RNA polymerase II polypeptide A small phosphatase (CTDSP) family, including CTDSPL, CTDSP2 and CTDSP1. We conducted serum starvation-stimulation assays in primary fibroblasts and two-thirds partial-hepatectomies in mice, which revealed that miR-26a/b and CTDSP1/2/L were expressed concomitantly during the cell cycle process. Specifically, they were increased in quiescent cells and decreased during cell proliferation. Furthermore, both miR-26 and CTDSP family members were frequently downregulated in hepatocellular carcinoma (HCC) tissues. Gain- and loss-of-function studies showed that miR-26a/b and CTDSP1/2/L synergistically decreased the phosphorylated form of pRb (ppRb), and blocked G1/S-phase progression. Further investigation disclosed that miR-26a/b directly suppressed the expression of CDK6 and cyclin E1, which resulted in reduced phosphorylation of pRb. Moreover, c-Myc, which is often upregulated in cancer cells, diminished the expression of both miR-26 and CTDSP family members, enhanced the ppRb level and promoted the G1/S-phase transition. Our findings highlight the functional association of miR-26a/b and their host genes and provide new insight into the regulatory network of the G1/S-phase transition.

Kinase gene expression and subcellular protein expression pattern of protein kinase C isoforms in curcumin-treated human hepatocellular carcinoma Hep 3B cells

Curcumin, a yellow component of turmeric or curry powder, has been demonstrated to exhibit anti-carcinogenic effects in vitro, in vivo, and in human clinical trials. One of its molecular targets is protein kinase C (PKC) which has been reported to play essential roles in apoptosis, cell proliferation, and carcinogenesis. In this study, PKC mRNA expression was significantly inhibited in curcumin-treated human hepatocellular carcinoma (HCC) Hep 3B cells identified using a kinase cDNA microarray. Furthermore, curcumin decreased total protein expression of all PKCs in a time-related manner by immunoblotting of whole cell lysates, nuclear, membrane, and cytosolic fractions. In cytosolic fraction, the expression of PKC-α was totally inhibited by curcumin. In contrast, the expression levels of PKC-ζ and -μ were dramatically increased. Increases in expression of PKC-δ and PKC-ζ in the membrane and nucleus, and PKC-ι in the membrane were detected. In summary, the changes in expression and distribution of subcellular PKC isoforms in curcumin-treated Hep 3B cells suggest possible PKC-associated anti-tumor mechanisms of curcumin and provide alternative therapies for human HCC.

Therapeutic potential of curcumin in gastrointestinal diseases

Curcumin, also known as diferuloylmethane, is derived from the plant Curcuma longa and is the active ingredient of the spice turmeric. The therapeutic activities of curcumin for a wide variety of diseases such as diabetes, allergies, arthritis and other chronic and inflammatory diseases have been known for a long time. More recently, curcumin’s therapeutic potential for preventing and treating various cancers is being recognized. As curcumin’s therapeutic promise is being explored more systematically in various diseases, it has become clear that, due to its increased bioavailability in the gastrointestinal tract, curcumin may be particularly suited to be developed to treat gastrointestinal diseases. This review summarizes some of the current literature of curcumin’s anti-inflammatory, anti-oxidant and anti-cancer potential in inflammatory bowel diseases, hepatic fibrosis and gastrointestinal cancers.

Curcumin stimulates reactive oxygen species production and potentiates apoptosis induction by the antitumor drugs arsenic trioxide and lonidamine in human myeloid leukemia cell lines

Arsenic trioxide (ATO, Trisenox) is an important antileukemic drug, but its efficacy is frequently low when used as a single agent. Here, we demonstrate that the apoptotic action of ATO is greatly increased when combined with subcytotoxic curcumin concentrations in U937 and HL60 human acute myeloid leukemia cells, and with lower efficacy in K562 chronic myelogenous leukemia cells. Curcumin exerts similar cooperative effect with the mitochondria-targeting drug lonidamine, whereas the response is negligible in combination with the DNA-targeting drug cisplatin. Curcumin plus ATO or lonidamine stimulates typical events of the mitochondrial executioner pathway (Bax and Bid activation, cytochrome c release, X-linked inhibitor of apoptosis down-regulation, and caspase-9/-3 activation) and causes mitochondrial transmembrane potential dissipation, which nevertheless represents a late event in the apoptotic response. Curcumin increases anion superoxide production, and its proapoptotic action in combination with ATO and lonidamine is mimicked by pro-oxidant agents (2-methoxyestradiol and H(2)O(2)) and prevented by antioxidant agents [Mn(III)tetrakis(4-benzoic acid)porphyrin chloride and N-acetyl-l-cysteine]. Within the assayed time period (16-24 h), curcumin does not significantly modify p38-mitogen-activated protein kinase and c-Jun NH(2)-terminal kinase phosphorylation/activation or nuclear factor-κB activity, but it greatly stimulates extracellular signal-regulated kinase (ERK) phosphorylation, and decreases Akt phosphorylation. Experiments using mitogen-activated protein kinase kinase/ERK inhibitors [2'-amino-3'-methoxyflavone (PD98059) and 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene (U0126)] and phosphatidylinositol 3-kinase inhibitor 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) indicate that ERK activation does not mediate and even restrains apoptosis potentiation, whereas Akt down-regulation facilitates apoptosis generation. In summary, cotreatment with curcumin may represent a useful manner of increasing the efficacy of ATO and lonidamine as antitumor drugs in myeloid leukemia cells.

Identification of Siah-interacting protein as a potential regulator of apoptosis and curcumin resistance

The mechanism underlying curcumin (diferuloylmethane) resistance is still largely unknown. Here we employed proteomic approach to identify the Siah-interacting protein (SIP) as a candidate for detailed study, because the spot intensity of SIP on a two-dimensional gel displayed 70-90% reduction in curcumin-sensitive cells, but remained unchanged in curcumin-resistant sublines, after curcumin treatment. Both gain- and loss-of-function studies revealed that SIP promoted curcumin-induced apoptosis. Moreover, SIP underwent phosphorylation and nuclear translocation in curcumin-sensitive but not resistant cells, upon curcumin exposure. The nuclear translocation of SIP was remarkably impaired when a putative nuclear localization sequence (NLS, amino acid (aa) 143-159) was deleted or the serine 141 was mutated into alanine, whereas truncation of the N-terminal region (aa 1-43) obviously increased the nuclear import of SIP. In accordance with their nuclear localization, N-terminal truncation significantly enhanced the proapoptotic effect of SIP, whereas NLS deletion or Ser141Ala mutation attenuated the apoptosis-promoting activity of both wild-type- and N-terminal truncated-SIP. These data suggest that SIP plays a role in apoptosis and curcumin resistance, and the function of SIP may be regulated by different motifs, such as the NLS, N-terminal region and serine 141. Our findings provide new insights into the biological significance of SIP and the mechanisms of drug resistance.

Curcumin and cancer cells: how many ways can curry kill tumor cells selectively?

Cancer is a hyperproliferative disorder that is usually treated by chemotherapeutic agents that are toxic not only to tumor cells but also to normal cells, so these agents produce major side effects. In addition, these agents are highly expensive and thus not affordable for most. Moreover, such agents cannot be used for cancer prevention. Traditional medicines are generally free of the deleterious side effects and usually inexpensive. Curcumin, a component of turmeric (Curcuma longa), is one such agent that is safe, affordable, and efficacious. How curcumin kills tumor cells is the focus of this review. We show that curcumin modulates growth of tumor cells through regulation of multiple cell signaling pathways including cell proliferation pathway (cyclin D1, c-myc), cell survival pathway (Bcl-2, Bcl-xL, cFLIP, XIAP, c-IAP1), caspase activation pathway (caspase-8, 3, 9), tumor suppressor pathway (p53, p21) death receptor pathway (DR4, DR5), mitochondrial pathways, and protein kinase pathway (JNK, Akt, and AMPK). How curcumin selectively kills tumor cells, and not normal cells, is also described in detail.

MicroRNA-195 suppresses tumorigenicity and regulates G1/S transition of human hepatocellular carcinoma cells

Growing evidence indicates that deregulation of microRNAs (miRNAs) contributes to tumorigenesis. Down-regulation of miR-195 has been observed in various types of cancers. However, the biological function of miR-195 is still largely unknown. In this study we aimed to elucidate the pathophysiologic role of miR-195. Our results showed that miR-195 expression was significantly reduced in as high as 85.7% of hepatocellular carcinoma (HCC) tissues and in all of the five HCC cell lines examined. Moreover, introduction of miR-195 dramatically suppressed the ability of HCC and colorectal carcinoma cells to form colonies in vitro and to develop tumors in nude mice. Furthermore, ectopic expression of miR-195 blocked G(1)/S transition, whereas inhibition of miR-195 promoted cell cycle progression. Subsequent investigation characterized multiple G(1)/S transition-related molecules, including cyclin D1, CDK6, and E2F3, as direct targets of miR-195. Silencing of cyclin D1, CDK6, or E2F3 phenocopied the effect of miR-195, whereas overexpression of these proteins attenuated miR-195-induced G(1) arrest. In addition, miR-195 significantly repressed the phosphorylation of Rb as well as the transactivation of downstream target genes of E2F. These results imply that miR-195 may block the G(1)/S transition by repressing Rb-E2F signaling through targeting multiple molecules, including cyclin D1, CDK6, and E2F3.

CONCLUSION

Our data highlight an important role of miR-195 in cell cycle control and in the molecular etiology of HCC, and implicate the potential application of miR-195 in cancer therapy.

Activation of ATM/Chk1 by curcumin causes cell cycle arrest and apoptosis in human pancreatic cancer cells

Curcumin has been shown to inhibit the growth of various types of cancer cells; however, at concentrations much above the clinically achievable levels in humans. The concentration of curcumin achieved in the plasma after oral administration in humans was estimated to be around 1.8 microM. Here, we report that treatment of BxPC-3 human pancreatic cancer cells with a low and single exposure of 2.5 microM curcumin for 24 h causes significant arrest of cells in the G2/M phase and induces significant apoptosis. Immunoblot studies revealed increased phosphorylation of H2A.X at Ser-139 and Chk1 at Ser-280 and a decrease in DNA polymerase-beta level in curcumin-treated cells. Phosphorylation of H2A.X and Chk1 proteins are an indicator of DNA damage whereas DNA polymerase-beta plays a role in the repair of DNA strand breaks. Normal immortalised human pancreatic ductal epithelial (HPDE-6) cells remained unaffected by curcumin treatment. In addition, we also observed a significant increase in the phosphorylation of Chk1 at Ser-345, Cdc25C at Ser-216 and a subtle increase in ATM phosphorylation at Ser-1981. Concomitant decrease in the expressions of cyclin B1 and Cdk1 were seen in curcumin-treated cells. Further, curcumin treatment caused significant cleavage of caspase-3 and PARP in BxPC-3 but not in HPDE-6 cells. Silencing ATM/Chk1 expression by transfecting BxPC-3 cells with ATM or Chk1-specific SiRNA blocked the phosphorylation of ATM, Chk1 and Cdc25C and protected the cells from curcumin-mediated G2/M arrest and apoptosis. This study reflects the critical role of ATM/Chk1 in curcumin-mediated G2/M cell cycle arrest and apoptosis in pancreatic cancer cells.