Curcumin downregulates H19 gene transcription in tumor cells

Modulation of long noncoding RNAs by polyphenols as a novel potential therapeutic approach in lung cancer: A comprehensive review

Lung cancer stands as a formidable global health challenge, necessitating innovative therapeutic strategies. Polyphenols, bioactive compounds synthesized by plants, have garnered attention for their diverse health benefits, particularly in combating various cancers, including lung cancer. The advent of whole-genome and transcriptome sequencing technologies has illuminated the pivotal roles of long noncoding RNAs (lncRNAs), operating at epigenetic, transcriptional, and posttranscriptional levels, in cancer progression. This review comprehensively explores the impact of polyphenols on both oncogenic and tumor-suppressive lncRNAs in lung cancer, elucidating on their intricate regulatory mechanisms. The comprehensive examination extends to the potential synergies when combining polyphenols with conventional treatments like chemotherapy, radiation, and immunotherapy. Recognizing the heterogeneity of lung cancer subtypes, the review emphasizes the need for the integration of nanotechnology for optimized polyphenol delivery and personalized therapeutic approaches. In conclusion, we collect the latest research, offering a holistic overview of the evolving landscape of polyphenol-mediated modulation of lncRNAs in lung cancer therapy. The integration of polyphenols and lncRNAs into multidimensional treatment strategies holds promise for enhancing therapeutic efficacy and navigating the challenges associated with lung cancer treatment.

Regulation of main ncRNAs by polyphenols: A novel anticancer therapeutic approach

BACKGROUND

Plant polyphenols have shown promising applications in oncotherapy. Increasing evidence reveals that polyphenols possess the antitumor potential for multiple cancers. Non-coding RNAs (ncRNAs), mainly including small ncRNAs (microRNA) and long ncRNAs (lncRNAs), play critical roles in cancer initiation and progression.

PURPOSE

To establish the modulation of ncRNAs by polyphenols as a novel and promising approach in anticancer treatment.

STUDY DESIGN

The present research employed ncRNA, miRNA, lncRNA, and regulatory mechanism as keywords to retrieve the literature from PubMed, Web of Science, Science direct, and Google Scholar, in a 20-year period from 2003 to 2023. This study critically reviewed the current literature and presented the regulation of prominent ncRNAs by polyphenols. A comprehensive total of 169 papers were retrieved on polyphenols and their related ncRNAs in cancers.

RESULTS

NcRNAs, mainly including miRNA and lncRNA, play critical roles in cancer initiation and progression, which are potential modulatory targets of bioactive polyphenols, such as resveratrol, genistein, curcumin, EGCG, quercetin, in cancer management. The mechanism involved in polyphenol-mediated ncRNA regulation includes epigenetic and transcriptional modification, and post-transcriptional processing.

CONCLUSION

Regulatory ncRNAs are potential therapeutic targets of bioactive polyphenols, and these phytochemicals could modulate the level of these ncRNAs directly and indirectly. A better comprehension of the ncRNA regulation by polyphenols in cancers, their functional outcomes on tumor pathophysiology and regulatory molecular mechanisms, may be helpful to develop effective strategies to fight the devastating disease.

Curcuminoids as Anticancer Drugs: Pleiotropic Effects, Potential for Metabolic Reprogramming and Prospects for the Future

The number of published studies on curcuminoids in cancer research, including its lead molecule curcumin and synthetic analogs, has been increasing substantially during the past two decades. Insights on the diversity of inhibitory effects they have produced on a multitude of pathways involved in carcinogenesis and tumor progression have been provided. As this wealth of data was obtained in settings of various experimental and clinical data, this review first aimed at presenting a chronology of discoveries and an update on their complex in vivo effects. Secondly, there are many interesting questions linked to their pleiotropic effects. One of them, a growing research topic, relates to their ability to modulate metabolic reprogramming. This review will also cover the use of curcuminoids as chemosensitizing molecules that can be combined with several anticancer drugs to reverse the phenomenon of multidrug resistance. Finally, current investigations in these three complementary research fields raise several important questions that will be put among the prospects for the future research related to the importance of these molecules in cancer research.

Investigation and multiscale modeling of PVA/SA coated poly lactic acid scaffold containing curcumin loaded layered double hydroxide nanohybrids

Applying hydrophilic coatings on polymeric nanofibers combined with layered double hydroxide (LDH) not only enhances the efficiency of drug delivery systems but also increases cell adhesion. This work aimed to prepare poly(vinyl alcohol)/sodium alginate (PVA/SA) (2/1)-coated poly(lactic acid) (PLA) nanofibers containing curcumin-loaded layered double hydroxide (LDH) and to investigate their drug release and mechanical properties and their biocompatibility. The optimum PLA nanofibrous sample was considered to be that based on 3 wt% of curcumin-loaded LDH (PLA-3%LDH) with a drug encapsulation efficiency of ∼18% in which a minimum average nanofiber diameter of ∼476 nm along with a high tensile strength of 3.00 MPa were obtained. In the next step, a PVA/SA (2/1) layer was coated on the PLA-3%LDH; as a result, the hydrophilicity of the sample was improved and the elongation at break was decreased remarkably. In this regard the cell viability reached 80% for the coated PLA. Moreover, the formation of a layer of (PVA/SA) on the PLA nanofibers lowered the burst release and resulted in a more sustained drug release, which is a vital feature in dermal applications. A multiscale modeling method was applied for simulation of the mechanical properties of the composite scaffold and the results showed that this method can predict the data with 83% accuracy. The results of this study indicate that the formation of a layer of PVA/SA (2/1) has a significant effect on hydrophilicity and consequently improves cell adhesion and proliferation.

Enhanced Cytotoxic Activity of PEGylated Curcumin Derivatives: Synthesis, Structure-Activity Evaluation, and Biological Activity

Curcumin has been modified in various ways to broaden its application in medicine and address its limitations. In this study, we present a series of curcumin-based derivatives obtained by replacing the hydroxy groups in the feruloyl moiety with polyethylene glycol (PEG) chains and the addition of the BF₂ moiety to the carbonyl groups. Tested compounds were screened for their cytotoxic activity toward two bladder cancer cell lines, 5637 and SCaBER, and a noncancerous cell line derived from lung fibroblasts (MRC-5). Cell viability was analyzed under normoxic and hypoxic conditions (1% oxygen). Structure-activity relationships (SARs) are discussed, and curcumin derivatives equipped within feruloyl moieties with 3-methoxy and 4-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy} substituents (5) were selected for further analysis. Compound 5 did not affect the viability of MRC-5 cells and exerted a stronger cytotoxic effect under hypoxic conditions. However, the flow cytometry studies showed that PEGylation did not improve cellular uptake. Another observation was that the lack of serum proteins limits the intracellular uptake of curcumin derivative 5. The preliminary mechanism of action studies indicated that compound 5 under hypoxic conditions induced G2/M arrest in a dose-dependent manner and increased the expression of stress-related proteins such as p21/CIP1, phosphorylated HSP27, ADAMTS-1, and phosphorylated JNK. In summary, the results of the studies indicated that PEGylated curcumin is a more potent compound against bladder cancer cell lines than the parent compound, and derivative 5 is worthy of further investigation to clarify its mechanism of anticancer action under hypoxic conditions.

Contribution of Non-Coding RNAs to Anticancer Effects of Dietary Polyphenols: Chlorogenic Acid, Curcumin, Epigallocatechin-3-Gallate, Genistein, Quercetin and Resveratrol

Growing evidence has been accumulated to show the anticancer effects of daily consumption of polyphenols. These dietary polyphenols include chlorogenic acid, curcumin, epigallocatechin-3-O-gallate, genistein, quercetin, and resveratrol. These polyphenols have similar chemical and biological properties in that they can act as antioxidants and exert the anticancer effects via cell signaling pathways involving their reactive oxygen species (ROS)-scavenging activity. These polyphenols may also act as pro-oxidants under certain conditions, especially at high concentrations. Epigenetic modifications, including dysregulation of noncoding RNAs (ncRNAs) such as microRNAs, long noncoding RNAs, and circular RNAs are now known to be involved in the anticancer effects of polyphenols. These polyphenols can modulate the expression/activity of the component molecules in ROS-scavenger-triggered anticancer pathways (RSTAPs) by increasing the expression of tumor-suppressive ncRNAs and decreasing the expression of oncogenic ncRNAs in general. Multiple ncRNAs are similarly modulated by multiple polyphenols. Many of the targets of ncRNAs affected by these polyphenols are components of RSTAPs. Therefore, ncRNA modulation may enhance the anticancer effects of polyphenols via RSTAPs in an additive or synergistic manner, although other mechanisms may be operating as well.

Emerging roles of long noncoding RNAs in chemoresistance of pancreatic cancer

Pancreatic cancer is one of the most common causes of cancer death in the world due to the lack of early symptoms, metastasis occurrence and chemoresistance. Therefore, early diagnosis by detection of biomarkers, blockade of metastasis, and overcoming chemoresistance are the effective strategies to improve the survival of pancreatic cancer patients. Accumulating evidence has revealed that long noncoding RNA (lncRNA) and circular RNAs (circRNAs) play essential roles in modulating chemosensitivity in pancreatic cancer. In this review article, we will summarize the role of lncRNAs in drug resistance of pancreatic cancer cells, including HOTTIP, HOTAIR, PVT1, linc-ROR, GAS5, UCA1, DYNC2H1-4, MEG3, TUG1, HOST2, HCP5, SLC7A11-AS1 and CASC2. We also highlight the function of circRNAs, such as circHIPK3 and circ_0000284, in regulation of drug sensitivity of pancreatic cancer cells. Moreover, we describe a number of compounds, including curcumin, genistein, resveratrol, quercetin, and salinomycin, which may modulate the expression of lncRNAs and enhance chemosensitivity in pancreatic cancers. Therefore, targeting specific lncRNAs and cicrRNAs could contribute to reverse chemoresistance of pancreatic cancer cells. We hope this review might stimulate the studies of lncRNAs and cicrRNAs, and develop the new therapeutic strategy via modulating these noncoding RNAs to promote chemosensitivity of pancreatic cancer cells.

Long noncoding RNAs in intestinal homeostasis, regeneration, and cancer

Signaling pathways that regulate homeostasis and regeneration are found to be deregulated in various human malignancies. Accordingly, attempts have been made to target them at the protein level with little success. However, studies using high-throughput sequencing technologies suggest that only about 2% of the genome translates into proteins, whereas about 75% of the genome is transcribed into noncoding RNAs. Among noncoding RNAs, long noncoding RNAs (lncRNAs) have received tremendous attention in recent years as a crucial player in the regulation of almost all cellular processes involved in tissue homeostasis as well as in the development of various malignancies, including intestinal cancer. Emerging evidence suggests that lncRNAs play an instrumental role in the regulation of intestinal stem cells, injury-induced regeneration, and initiation and progression of intestinal tumors. Here, we summarize the recently discovered lncRNAs during intestinal homeostasis, regeneration, and tumorigenesis. We further present lncRNAs as diagnostic and therapeutic markers in intestinal pathologies.

Regulation of Long Non-Coding RNAs by Plant Secondary Metabolites: A Novel Anticancer Therapeutic Approach

Simple Summary

Cancer is caused by the rapid and uncontrolled growth of cells that eventually lead to tumor formation. Genetic and epigenetic alterations are among the most critical factors in the onset of carcinoma. Phytochemicals are a group of natural compounds that play an essential role in cancer prevention and treatment. Long non-coding RNAs (lncRNAs) are potential therapeutic targets of bioactive phytochemicals, and these compounds could regulate the expression of lncRNAs directly and indirectly. Here, we critically evaluate in vitro and in vivo anticancer effects of phytochemicals in numerous human cancers via regulation of lncRNA expression and their downstream target genes.

Abstract

Long non-coding RNAs (lncRNAs) are a class of non-coding RNAs that play an essential role in various cellular activities, such as differentiation, proliferation, and apoptosis. Dysregulation of lncRNAs serves a fundamental role in the progression and initiation of various diseases, including cancer. Precision medicine is a suitable and optimal treatment method for cancer so that based on each patient’s genetic content, a specific treatment or drug is prescribed. The rapid advancement of science and technology in recent years has led to many successes in this particular treatment. Phytochemicals are a group of natural compounds extracted from fruits, vegetables, and plants. Through the downregulation of oncogenic lncRNAs or upregulation of tumor suppressor lncRNAs, these bioactive compounds can inhibit metastasis, proliferation, invasion, migration, and cancer cells. These natural products can be a novel and alternative strategy for cancer treatment and improve tumor cells’ sensitivity to standard adjuvant therapies. This review will discuss the antineoplastic effects of bioactive plant secondary metabolites (phytochemicals) via regulation of expression of lncRNAs in various human cancers and their potential for the treatment and prevention of human cancers.

Cell-Type Specific Metabolic Response of Cancer Cells to Curcumin

In order to support uncontrolled proliferation, cancer cells need to adapt to increased energetic and biosynthetic requirements. One such adjustment is aerobic glycolysis or the Warburg effect. It is characterized by increased glucose uptake and lactate production. Curcumin, a natural compound, has been shown to interact with multiple molecules and signaling pathways in cancer cells, including those relevant for cell metabolism. The effect of curcumin and its solvent, ethanol, was explored on four different cancer cell lines, in which the Warburg effect varied. Vital cellular parameters (proliferation, viability) were measured along with the glucose consumption and lactate production. The transcripts of pyruvate kinase 1 and 2 (PKM1, PKM2), serine hydroxymethyltransferase 2 (SHMT2) and phosphoglycerate dehydrogenase (PHGDH) were quantified with RT-qPCR. The amount and intracellular localization of PKM1, PKM2 and signal transducer and activator of transcription 3 (STAT3) proteins were analyzed by Western blot. The response to ethanol and curcumin seemed to be cell-type specific, with respect to all parameters analyzed. High sensitivity to curcumin was present in the cell lines originating from head and neck squamous cell carcinomas: FaDu, Detroit 562 and, especially, Cal27. Very low sensitivity was observed in the colon adenocarcinoma-originating HT-29 cell line, which retained, after exposure to curcumin, a higher levels of lactate production despite decreased glucose consumption. The effects of ethanol were significant.

The long non-coding RNA H19: an active player with multiple facets to sustain the hallmarks of cancer

Cancer cells exhibit hallmarks in terms of proliferation, resistance to cell death, angiogenesis, invasion, metastasis, and genomic instability. Despite the progress in cancer research and the comprehension of tumorigenesis mechanisms, cancer remains a major issue in public health. A better understanding of the molecular factors associated with the appearance or progression of cancer may allow the development of therapeutic alternatives. Increasing data highlight the role of long non-coding RNAs in many diseases, including cancer. The long non-coding RNA H19 was the first discovered riboregulator, and it has been shown to be involved at multiple steps of tumorigenesis. Indeed, this lncRNA exert its action at various molecular scales. Understanding the role of H19 in cancer progression may allow to set up therapeutic strategies to prevent tumor expansion and metastatic dissemination. In this review, we will summarize the overexpression of the long non-coding RNA H19 in several types of cancer and the multiple implications of the long non-coding RNA H19 in the different hallmarks that define human cancer.

Side Effects of Curcumin: Epigenetic and Antiproliferative Implications for Normal Dermal Fibroblast and Breast Cancer Cells

Background: Curcumin is a yellow-orange pigment obtained from the plant Curcuma longa, which is known to exert beneficial effects in several diseases, including cancer. However, at high doses, it may produce toxic and carcinogenic effects in normal cells. In this context, we studied the effects of curcumin on normal human dermal fibroblast (HDF) cells and breast cancer cells (MCF7). Methods: We used cellular viability and growth assays to evaluate the antiproliferative action of curcumin, analyzed the endogenous glutathione levels, conducted cell cycle, apoptosis, and necrosis analyses, and performed immunodetection of glutathionylated and acetylated H3 histones. Results: We found that HDFs are more sensitive to curcumin treatment than MCF7 cells, resulting in pronounced arrest of cell cycle progression and higher levels of cellular death. In both cell types, the homeostasis of the redox cellular environment did not change after curcumin treatment; however, significant differences were observed in glutathione (GSH) levels and in S-glutathionylation of H3 histones. Conclusion: Curcumin administration can potentially confer benefits, but high doses may be toxic. Thus, its use as a dietary supplement or in cancer therapies has a double edge.

Nutritional Stress in Head and Neck Cancer Originating Cell Lines: The Sensitivity of the NRF2-NQO1 Axis

Nutritional stress disturbs the cellular redox-status, which is characterized by the increased generation of reactive oxygen species (ROS). The NRF2-NQO1 axis represents a protective mechanism against ROS. Its strength is cell type-specific. FaDu, Cal 27 and Detroit 562 cells differ with respect to basal NQO1 activity. These cells were grown for 48 hours in nutritional conditions (NC): (a) Low glucose-NC2, (b) no glucose, no glutamine-NC3, (c) no glucose with glutamine-NC4. After determining the viability, proliferation and ROS generation, NC2 and NC3 were chosen for further exploration. These conditions were also applied to IMR-90 fibroblasts. The transcripts/transcript variants of NRF2 and NQO1 were quantified and transcript variants were characterized. The proteins (NRF2, NQO1 and TP53) were analyzed by a western blot in both cellular fractions. Under NC2, the NRF2-NQO1 axis did not appear activated in the cancer cell lines. Under NC3, the NRF2-NQO1axis appeared slightly activated in Detroit 562. There are opposite trends with respect to TP53 nuclear signal when comparing Cal 27 and Detroit 562 to FaDu, under NC2 and NC3. The strong activation of the NRF2-NQO1 axis in IMR-90 resulted in an increased expression of catalytically deficient NQO1, due to NQO1*2/*2 polymorphism (rs1800566). The presented results call for a comprehensive exploration of the stress response in complex biological systems.

Phytochemicals as Modulators of Long Non-Coding RNAs and Inhibitors of Cancer-Related Carbonic Anhydrases

Long non-coding RNAs (lncRNAs) are classified as a group of transcripts which regulate various biological processes, such as RNA processing, epigenetic control, and signaling pathways. According to recent studies, lncRNAs are dysregulated in cancer and play an important role in cancer incidence and spreading. There is also an association between lncRNAs and the overexpression of some tumor-associated proteins, including carbonic anhydrases II, IX, and XII (CA II, CA IX, and CA XII). Therefore, not only CA inhibition, but also lncRNA modulation, could represent an attractive strategy for cancer prevention and therapy. Experimental studies have suggested that herbal compounds regulate the expression of many lncRNAs involved in cancer, such as HOTAIR (HOX transcript antisense RNA), H19, MALAT1 (metastasis-associated lung adenocarcinoma transcript 1), PCGEM1 (Prostate cancer gene expression marker 1), PVT1, etc. These plant-derived drugs or phytochemicals include resveratrol, curcumin, genistein, quercetin, epigallocatechin-3-galate, camptothcin, and 3,3'-diindolylmethane. More comprehensive information about lncRNA modulation via phytochemicals would be helpful for the administration of new herbal derivatives in cancer therapy. In this review, we describe the state-of-the-art and potential of phytochemicals as modulators of lncRNAs in different types of cancers.

Long non-coding RNAs are emerging targets of phytochemicals for cancer and other chronic diseases

The long non-coding RNAs (lncRNAs) are the crucial regulators of human chronic diseases. Therefore, approaches such as antisense oligonucleotides, RNAi technology, and small molecule inhibitors have been used for the therapeutic targeting of lncRNAs. During the last decade, phytochemicals and nutraceuticals have been explored for their potential against lncRNAs. The common lncRNAs known to be modulated by phytochemicals include ROR, PVT1, HOTAIR, MALAT1, H19, MEG3, PCAT29, PANDAR, NEAT1, and GAS5. The phytochemicals such as curcumin, resveratrol, sulforaphane, berberine, EGCG, and gambogic acid have been examined against lncRNAs. In some cases, formulation of phytochemicals has also been used. The disease models where phytochemicals have been demonstrated to modulate lncRNAs expression include cancer, rheumatoid arthritis, osteoarthritis, and nonalcoholic fatty liver disease. The regulation of lncRNAs by phytochemicals can affect multi-steps of tumor development. When administered in combination with the conventional drugs, phytochemicals can also produce synergistic effects on lncRNAs leading to the sensitization of cancer cells. Phytochemicals target lncRNAs either directly or indirectly by affecting a wide variety of upstream molecules. However, the potential of phytochemicals against lncRNAs has been demonstrated mostly by preclinical studies in cancer models. How the modulation of lncRNAs by phytochemicals produce therapeutic effects on cancer and other chronic diseases is discussed in this review.

Relations between approved platinum drugs and non-coding RNAs in mesothelioma

Malignant mesothelioma diseases feature an increasing risk due to their severe forms and their association with asbestos exposure. Platinum(II) complexes such as cisplatin and carboplatin are clinically approved for the therapy of mesothelioma often in combination with antimetabolites such as pemetrexed or gemcitabine. It was observed that pathogenic properties of mesothelioma cells and the response of mesothelioma tumors towards platinum-based drugs are strongly influenced by non-coding RNAs, in particular, by small microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). These non-coding RNAs controlled drug sensitivity and the development of tumor resistance towards platinum drugs. An overview of the interactions between platinum drugs and non-coding RNAs is given and the influence of non-coding RNAs on platinum drug efficacy in mesothelioma is discussed. Suitable non-coding RNA-modulating agents with potentially beneficial effects on cisplatin treatment of mesothelioma diseases are mentioned. The understanding of mesothelioma diseases concerning the interactions of non-coding RNAs and platinum drugs will optimize existing therapy schemes and pave the way to new treatment options in future.

Interplay of non-coding RNAs and approved antimetabolites such as gemcitabine and pemetrexed in mesothelioma

Gemcitabine and pemetrexed are clinically approved antimetabolites for the therapy of mesothelioma diseases. These drugs are often applied in combination with platinum complexes and other drugs. The activity of antimetabolites depended on the expression levels of certain non-coding RNAs, in particular, of small microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). The development of tumor resistance towards antimetabolites was regulated by non-coding RNAs. An overview of the interplay between gemcitabine/pemetrexed antimetabolites and non-coding RNAs in mesothelioma is provided. Further to this, various non-coding RNA-modulating agents are discussed which displayed positive effects on gemcitabine or pemetrexed treatment of mesothelioma diseases. A detailed knowledge of the connections of non-coding RNAs with antimetabolites will be constructive for the design of improved therapies in future.

Long Noncoding RNA lncARSR Promotes Doxorubicin Resistance in Hepatocellular Carcinoma via Modulating PTEN-PI3K/Akt Pathway

Hepatocellular carcinoma (HCC) is generally resistant to chemotherapy due to intrinsic or acquired drug resistances. Many molecules and signaling pathways are involved in chemo-resistance of HCC cells. However, the contribution of long noncoding RNA (lncRNA) to chemo-resistance of HCC cells is still largely unknown. In this study, we revealed the critical roles of long noncoding RNA lncARSR in chemo-resistance of HCC cells. lncARSR is upregulated in HCC, associated with large tumor size and advanced BCLC stage, and indicts poor prognosis. Functional assays showed that overexpression of lncARSR enhances doxorubicin resistance of HCC cells in vitro and in vivo. And while knockdown of lncARSR increases sensitivity of HCC cells to doxorubicin in vitro and in vivo. Mechanistically, we found that lncARSR physically associates with PTEN mRNA, promotes PTEN mRNA degradation, decreases PTEN expression, and activates PI3K/Akt pathway. PTEN is downregulated in HCC, and the expression of PTEN is negatively correlated with lncARSR in HCC tissues. Furthermore, the effects of lncARSR overexpression on doxorubicin resistance could be reversed by PI3K/Akt pathway inhibitor, and lncARSR knockdown-induced doxorubicin sensitivity could be reversed by PTEN depletion. Taken together, our results showed that upregulated lncARSR promotes doxorubicin resistance in HCC via modulating PTEN-PI3K/Akt pathway, and implied that lncARSR may serve as a promising prognostic biomarker and therapeutic target for HCC chemo-resistance. J. Cell. Biochem. 118: 4498-4507, 2017. © 2017 Wiley Periodicals, Inc.

Curcumin suppresses the proliferation of gastric cancer cells by downregulating H19

Curcumin, a major phytochemical in turmeric, inhibits the proliferation of many types of solid cancer cells by enhancing p53 expression. However, the long non-coding RNA H19 directly inhibits p53 activation and thus promotes gastric cancer progression. The aim of this study was to assess the role of H19 in curcumin-induced proliferative inhibition of gastric cancer. The gastric cancer cell line SGC-7901 was treated with curcumin at different concentrations and time points. The effect of curcumin on proliferation was assessed using cell counting kit-8 assays and flow cytometry with Ki67 staining. In addition, H19 expression was quantified by reverse transcription-quantitative polymerase chain reaction, and apoptosis was evaluated by flow cytometric detection of Annexin V and propidium iodide double staining. The protein expression of p53, B-cell lymphoma (Bcl)-2, Bcl-2-associated X protein (Bax) and c-Myc in curcumin-treated cells was detected by western blotting. The present study demonstrated that curcumin inhibited the proliferation of SGC7901 cells and suppressed H19 expression in a concentration-dependent manner, while p53 expression was enhanced. Ectopic expression of H19 in SGC7901 cells reversed curcumin-induced proliferative inhibition and downregulated p53 expression. Furthermore, while curcumin induced cell apoptosis and enhanced the expression ratio of Bax/Bcl-2, which are downstream molecules of p53, ectopic expression of H19 inhibited curcumin-induced cell apoptosis. In addition, curcumin decreased the expression of the c-Myc oncogene, and exogenous c-Myc protein reversed the curcumin-induced downregulation of H19 expression. These results suggested that curcumin inhibits the proliferation of gastric cancer cells by downregulating the c-Myc/H19 pathway. Therefore, curcumin may be considered a novel therapeutic strategy to inhibit gastric cancer cell growth.

The H19 Long non-coding RNA in cancer initiation, progression and metastasis - a proposed unifying theory

The imprinted oncofetal long non-coding RNA (lncRNA) H19 is expressed in the embryo, down-regulated at birth and then reappears in tumors. Its role in tumor initiation and progression has long been a subject of controversy, although accumulating data suggest that H19 is one of the major genes in cancer. It is actively involved in all stages of tumorigenesis and is expressed in almost every human cancer. In this review we delineate the various functions of H19 during the different stages in the complex process of tumor progression. H19 up-regulation allows cells to enter a "selfish" survival mode in response to stress conditions, such as destabilization of the genome and hypoxia, by accelerating their proliferation rate and increasing overall cellular resistance to stress. This response is tightly correlated with nullification, dysfunction or significant down-regulation of the master tumor suppressor gene P53. The growing evidence of H19's involvement in both proliferation and differentiation processes, together with its involvement in epithelial to mesenchymal transition (EMT) and also mesenchymal to epithelial transition (MET), has led us to conclude that some of the recent disputes and discrepancies arising from current research findings can be resolved from a viewpoint supporting the oncogenic properties of H19. According to a holistic approach, the versatile, seemingly contradictory functions of H19 are essential to, and differentially harnessed by, the tumor cell depending on its context within the process of tumor progression.

Curcumin inhibits proliferation of breast cancer cells through Nrf2-mediated down-regulation of Fen1 expression

Curcumin can inhibit cell proliferation of breast cancer, but the mechanism for this inhibition remains unclear. Over-expression of Flap endonuclease 1 (Fen1), a DNA repair-specific nuclease, is involved in the development of breast cancer. Nrf2 is a master regulator of cellular antioxidant defense systems. Curcumin can induce the expression of Nrf2 in both non-breast cancer cells and breast cancer cells. However, whether curcumin-induced inhibition of breast cancer cell proliferation may involve Nrf2-mediated Fen1 expression is not yet understood. In this study, we demonstrated that curcumin inhibited Fen1-dependent proliferation of MCF-7 cells and significantly induced Nrf2 protein expression while inhibiting Fen1 protein expression. Curcumin could down-regulate Fen1 gene expression in a Nrf2-dependent manner. Further investigation revealed that curcumin could lead to Nrf2 translocation from the cytoplasm to the nucleus and decrease Fen1 promoter activity by decreasing the recruitment of Nrf2 to the Fen1 promoter. These data suggest that curcumin may inhibit the proliferation of breast cancer cells through Nrf2-mediated down-regulation of Fen1 expression, which may be a new mechanism of curcumin-induced tumor growth inhibition.

When one is better than two: RNA with dual functions

The central dogma of biology, until not long ago, held that genetic information stored on DNA molecules was translated into the final protein products through RNA as intermediate molecules. Then, an additional level of complexity in the regulation of genome expression was added, implicating new classes of RNA molecules called non-coding RNA (ncRNA). These ncRNA are also often referred to as functional RNA in that, although they do not contain the capacity to encode proteins, do have a function as RNA molecules. They have been thus far considered as truly non-coding RNA since no ORF long enough to be considered, nor protein, have been associated with them. However, the recent identification and characterization of bifunctional RNA, i.e. RNA for which both coding capacity and activity as functional RNA have been reported, suggests that a definite categorization of some RNA molecules is far from being straightforward. Indeed, several RNA primarily classified as non-protein-coding RNA has been showed to hold coding capacities and associated peptides. Conversely, mRNA, usually regarded as strictly protein-coding, may act as functional RNA molecules. Here, we describe several examples of these bifunctional RNA that have been already characterized from bacteria to mammals. We also extend this concept to fortuitous acquisition of dual function in pathological conditions and to the recently highlighted duality between information carried by a gene and its pseudogenes counterparts.

The regulation of non-coding RNA expression in the liver of mice fed DDC

Mallory-Denk bodies (MDBs) are found in the liver of patients with alcoholic and chronic nonalcoholic liver disease, and hepatocellular carcinoma (HCC). Diethyl 1,4-dihydro-2,4,6,-trimethyl-3,5-pyridinedicarboxylate (DDC) is used as a model to induce the formation of MDBs in mouse liver. Previous studies in this laboratory showed that DDC induced epigenetic modifications in DNA and histones. The combination of these modifications changes the phenotype of the MDB forming hepatocytes, as indicated by the marker FAT10. These epigenetic modifications are partially prevented by adding to the diet S-adenosylmethionine (SAMe) or betaine, both methyl donors. The expression of three imprinted ncRNA genes was found to change in MDB forming hepatocytes, which is the subject of this report. NcRNA expression was quantitated by real-time PCR and RNA FISH in liver sections. Microarray analysis showed that the expression of three ncRNAs was regulated by DDC: up regulation of H19, antisense Igf2r (AIR), and down regulation of GTL2 (also called MEG3). S-adenosylmethionine (SAMe) feeding prevented these changes. Betaine, another methyl group donor, prevented only H19 and AIR up regulation induced by DDC, on microarrays. The results of the SAMe and betaine groups were confirmed by real-time PCR, except for AIR expression. After 1 month of drug withdrawal, the expression of the three ncRNAs tended toward control levels of expression. Liver tumors that developed also showed up regulation of H19 and AIR. The RNA FISH approach showed that the MDB forming cells' phenotype changed the level of expression of AIR, H19 and GTL2, compared to the surrounding cells. Furthermore, over expression of H19 and AIR was demonstrated in tumors formed in mice withdrawn for 9 months. The dysregulation of ncRNA in MDB forming liver cells has been observed for the first time in drug-primed mice associated with liver preneoplastic foci and tumors.

Syzygium cumini inhibits growth and induces apoptosis in cervical cancer cell lines: a primary study

Cervical cancer is common among women in the Indian subcontinent and the incidences and death rates are gradually increasing over the years. Several dietary phytochemicals have been reported to have growth inhibitory and apoptotic effect on HeLa and other cervical cell lines. In this study, using Hoechst 33342 staining, MTT, Annexin V-FLUOS/PI and TUNEL assays we demonstrated that Syzygium cumini extract inhibits the growth and induces apoptosis in HeLa and SiHa cervical cancer cell lines in a dose- and time-dependent manner. The phytochemical, its mode of action and safety issues are yet to be determined.