Garcinol regulates EMT and Wnt signaling pathways in vitro and in vivo, leading to anticancer activity against breast cancer cells

Regulation of microRNAs by natural agents: new strategies in cancer therapies

MicroRNAs (miRNAs) are short noncoding RNA which regulate gene expression by messenger RNA (mRNA) degradation or translation repression. The plethora of published reports in recent years demonstrated that they play fundamental roles in many biological processes, such as carcinogenesis, angiogenesis, programmed cell death, cell proliferation, invasion, migration, and differentiation by acting as tumour suppressor or oncogene, and aberrations in their expressions have been linked to onset and progression of various cancers. Furthermore, each miRNA is capable of regulating the expression of many genes, allowing them to simultaneously regulate multiple cellular signalling pathways. Hence, miRNAs have the potential to be used as biomarkers for cancer diagnosis and prognosis as well as therapeutic targets. Recent studies have shown that natural agents such as curcumin, resveratrol, genistein, epigallocatechin-3-gallate, indole-3-carbinol, and 3,3′-diindolylmethane exert their antiproliferative and/or proapoptotic effects through the regulation of one or more miRNAs. Therefore, this review will look at the regulation of miRNAs by natural agents as a means to potentially enhance the efficacy of conventional chemotherapy through combinatorial therapies. It is hoped that this would provide new strategies in cancer therapies to improve overall response and survival outcome in cancer patients.

Transcription regulation of E-cadherin by zinc finger E-box binding homeobox proteins in solid tumors

Downregulation of E-cadherin in solid tumors with regional migration and systematic metastasis is well recognized. In view of its significance in tumorigenesis and solid cancer progression, studies on the regulatory mechanisms are important for the development of target treatment and prediction of clinical behavior for cancer patients. The vertebrate zinc finger E-box binding homeobox (ZEB) protein family comprises 2 major members: ZEB1 and ZEB2. Both contain the motif for specific binding to multiple enhancer boxes (E-boxes) located within the short-range transcription regulatory regions of the E-cadherin gene. Binding of ZEB1 and ZEB2 to the spaced E-cadherin E-boxes has been implicated in the regulation of E-cadherin expression in multiple human cancers. The widespread functions of ZEB proteins in human malignancies indicate their significance. Given the significance of E-cadherin in the solid tumors, a deeper understanding of the functional role of ZEB proteins in solid tumors could provide insights in the design of target therapy against the migratory nature of solid cancers.

Nestin positively regulates the Wnt/β-catenin pathway and the proliferation, survival and invasiveness of breast cancer stem cells

INTRODUCTION

We investigated Nestin expression in triple-negative breast cancer and examined how the modulation of Nestin expression affects cell cycle progression, survival, invasion and regulatory signaling in breast cancer stem cells (CSC) in vitro.

METHODS

Nestin expression in 150 triple-negative breast cancer specimens were examined by immunohistochemistry. The role of Nestin expression in tumorigenesis was examined by assaying naturally occurring Nestinhigh/Nestinlow CSC from 12 breast cancer tissues, as well as CSC from 26 clinical specimens, where Nestin overexpression and silencing was achieved by genetic manipulation, for their ability to form mammospheres and induce solid tumors. Cell cycle progression, spontaneous apoptosis and invasiveness of Nestin-silenced breast CSC were investigated by flow cytometry and transwell assays. The relative levels of expression of epithelial-mesenchymal transition (EMT) and Wnt/β-catenin pathway-related molecules were determined by western blotting.

RESULTS

Nestin expression was significantly associated with poor survival in patients with triple-negative breast cancer (P = 0.01). Nestinhigh breast CSC rapidly formed typical mammospheres in vitro. Nestinhigh, but not Nestinlow CSC, efficiently formed solid tumors in vivo. Nestin silencing induced cell cycle arrest at G2/M (52.03% versus 19.99% in controls) and promoted apoptosis (36.45% versus 8.29% in controls). Nestin silencing also inhibited breast CSC invasiveness, and was associated with significantly upregulated E-cadherin, while N-cadherin, vimentin, a-smooth muscle actin (a-SMA), matrix metalloproteinase-2 (MMP-2), MMP-9 and vascular endothelial growth factor (VEGF) expression was downregulated (P <0.05 for all). Nestin silencing also upregulated Axin, glycogen synthase kinase-3 beta (GSK-3β), adenomatous polyposis coli (APC), and peroxisome proliferator-activated receptor alpha (PPARa), and downregulated β-catenin, c-Myc, cyclin D and MMP-7 expression in CSC. Inhibition of the Wnt/β-catenin pathway mitigated mammosphere formation in Nestinhigh CSC, while inhibition of GSK-3β promoted the mammosphere formation in Nestinlow CSC (P <0.05 for all).

CONCLUSIONS

Our data indicates that Nestin positively regulates the proliferation, survival and invasiveness of breast CSC by enhancing Wnt/β-catenin activation.

Garcinol suppresses inflammation-associated colon carcinogenesis in mice

SCOPE

Garcinol is a polyisoprenylated benzophenone derivative isolated from the fruit rind of Garcinia indica and has exhibited chemopreventive effects on azoxymethane)-induced colonic aberrant crypt foci in mice. In this study, we investigated whether garcinol protects against dextran sulfate sodium (DSS) induced colitis/inflammation and azoxymethane/DSS-induced inflammation-related colon tumorigenesis in male ICR mice. We also aimed to delineate the possible molecular mechanisms responsible for these effects.

METHODS AND RESULTS

Treatment with garcinol prevented shortening of the colon length and the formation of aberrant crypt foci and improved the inflammation score in the mouse colon stimulated by DSS. Moreover, administration of garcinol markedly decreased DSS-induced inducible nitric oxide synthase, cyclooxygenase-2, and proliferating cell nuclear antigen protein expression. The dietary administration of garcinol effectively reduced the tumor size and incidence in the mouse colon. Western blot and immunohistochemical analysis revealed that administration of garcinol significantly downregulated cyclooxygenase-2, cyclin D1, and vascular endothelial growth factor expression via inhibition of the extracellular signal-regulated protein kinase 1/2, phosphatidylinositol 3 kinase/Akt/p70 ribosomal S6 kinase, and Wnt/β-catenin signaling pathways.

CONCLUSION

Our results suggest that garcinol may merit further clinical investigation as a chemoprophylactic food that helps prevent colitis-associated colon cancer.

Glabridin attenuates the migratory and invasive capacity of breast cancer cells by activating microRNA-200c

Current treatments for breast cancer, a common malignancy in human females, are less than satisfactory because of high rates of metastasis. Glabridin (GLA), which acts through the FAK/ROS signaling pathway, has been used as an antioxidant and anti-metastatic agent. However, little is known regarding the effect of microRNA (miRNA) on GLA's anti-metastatic activity. The miRNA-200 family, which is frequently expressed at low levels in triple negative breast cancers, inhibits metastasis by blocking the epithelial–mesenchymal transition. Here, we found that GLA attenuated the migratory and invasive capacity of breast cancer cells by activating miR-200c. GLA induced the mesenchymal–epithelial transition in vitro and in vivo, as determined by increased expression of the epithelial marker, E-cadherin, and decreased expression of the mesenchymal marker, vimentin. Overexpression of miR-200c enhanced the expression of E-cadherin and decreased the expression of vimentin. Furthermore, in MDA-MB-231 and BT-549 breast cancer cells exposed to GLA, knockdown of miR-200c blocked the GLA-induced mesenchymal–epithelial transition and alleviated the GLA-induced inhibition of migration and invasion. Thus, elevation of miR-200c by GLA has considerable therapeutic potential for anti-metastatic therapy for breast cancer patients.

The therapeutic potential of targeting the epithelial-mesenchymal transition in cancer

INTRODUCTION

The process of epithelial-to-mesenchymal transition (EMT) has long been advocated as a process during tumor progression and the acquisition of metastatic potential of human cancers. EMT has also been linked with resistance to cancer therapies.

AREAS COVERED

Basic research has provided evidence connecting EMT to increased invasion, angiogenesis and metastasis of cancer cells. A number of signaling pathways such as notch, wnt, hedgehog and PI3K-AKT, and various other individual factors therein, have been intricately connected to the onset of EMT. Here, we provide latest updates on the evidences that further highlight an association between various signaling pathways and EMT, with a focus on therapeutic targets that may have the potential to reverse EMT.

EXPERT OPINION

Our understanding of EMT and its underlying causes is rapidly evolving and a number of putative targets have been identified. It is crucial, now than ever before, to design novel translational and clinical studies for the benefit of advanced stage cancer patients with metastatic disease.

Pneumocystis jirovecii Rtt109, a novel drug target for Pneumocystis pneumonia in immunosuppressed humans

Pneumocystis pneumonia (PcP) is a significant cause of morbidity and mortality in immunocompromised patients. In humans, PcP is caused by the opportunistic fungal species Pneumocystis jirovecii. Progress in Pneumocystis research has been hampered by a lack of viable in vitro culture methods, which limits laboratory access to human-derived organisms for drug testing. Consequently, most basic drug discovery research for P. jirovecii is performed using related surrogate organisms such as Pneumocystis carinii, which is derived from immunosuppressed rodents. While these studies provide useful insights, important questions arise about interspecies variations and the relative utility of identified anti-Pneumocystis agents against human P. jirovecii. Our recent work has identified the histone acetyltransferase (HAT) Rtt109 in P. carinii (i.e., PcRtt109) as a potential therapeutic target for PcP, since Rtt109 HATs are widely conserved in fungi but are absent in humans. To further address the potential utility of this target in human disease, we now demonstrate the presence of a functional Rtt109 orthologue in the clinically relevant fungal pathogen P. jirovecii (i.e., PjRtt109). In a fashion similar to that of Pcrtt109, Pjrtt109 restores H3K56 acetylation and genotoxic resistance in rtt109-null yeast. Recombinant PjRtt109 is an active HAT in vitro, with activity comparable to that of PcRtt109 and yeast Rtt109. PjRtt109 HAT activity is also enhanced by the histone chaperone Asf1 in vitro. PjRtt109 and PcRtt109 showed similar low micromolar sensitivities to two reported small-molecule HAT inhibitors in vitro. Together, these results demonstrate that PjRtt109 is a functional Rtt109 HAT, and they support the development of anti-Pneumocystis agents directed at Rtt109-catalyzed histone acetylation as a novel therapeutic target for human PcP.

Induction of the mesenchymal to epithelial transition by demethylation- activated microRNA-200c is involved in the anti-migration/invasion effects of arsenic trioxide on human breast cancer cells

Breast cancer is a major health problem worldwide. Current standard practices for treatment of breast cancer are less than satisfactory because of high rates of metastasis. Arsenic trioxide (As(2)O(3)), which induces demethylation of DNA and causes apoptosis, has been used as an anti-tumor agent. Little is known, however, regarding its anti-metastatic effects. The microRNA-200c (miR-200c), which is frequently lowly expressed in triple negative breast cancers (TNBCs), inhibits metastasis by inducing the mesenchymal to epithelial transition (MET). Here, we report that As(2)O(3) attenuates the migratory and invasive capacities of breast cancer cells, MDA-MB-231 and BT-549. Notably, As(2)O(3) induces an MET in vitro and in vivo, as determined by the increased expression of the epithelial marker, E-cadherin and decreased expressions of mesenchymal markers, N-cadherin and vimentin. Moreover, As(2)O(3) up-regulates the expression of miR-200c through demethylation. Over-expression of miR-200c enhances the expression of E-cadherin and decreases the expressions of N-cadherin and vimentin. Further, in MDA-MB-231 cells exposed to As(2)O(3), knockdown of miR-200c blocks the As(2)O(3) -induced MET. Finally, in MDA-MB-231 and BT-549 cells exposed to As(2)O(3), knockdown of miR-200c decreases the As(2)O(3) -induced inhibition of the migratory and invasive capacities. By identifying a mechanism whereby As(2)O(3) regulates miR-200c and MET, the results establish the anti-migration/invasion potential of arsenic trioxide.

Epigenetic regulation of miRNA-cancer stem cells nexus by nutraceuticals

Nutraceuticals, the bioactive food components represented by many naturally occurring dietary compounds, have been investigated for a few decades for their numerous beneficial effects, including their anticancer properties. The initial interest in the cancer-preventing/therapeutic ability of these agents was based on their ability to affect multiple signaling pathways that are deregulated in cancer cells. With a shift in the focus of cancer research to the emerging areas such as epigenetic regulation, microRNAs (miRNAs) and the cancer stem cells (CSCs), nutraceuticals initially appeared out of place. However, research investigations over the last several years have slowly but firmly presented evidence that supports a relevance of these agents in modern day research. While nutraceuticals are increasingly being realized to alter miRNA/CSCs expression and function, the molecular mechanism(s) are not very clearly understood. Epigenetic regulation is one mechanism by which these agents exert their anticancer effects. In this focused mini review, we summarize our current understanding of epigenetic regulation of miRNAs and CSCs by nutraceuticals. We discuss both direct and indirect evidences that support such an activity of these compounds.

The correlation between morphology and the expression of TGF-β signaling pathway proteins and epithelial-mesenchymal transition-related proteins in synovial sarcomas

Synovial sarcoma (SS) is a malignant tumor of soft tissue and is noted for late local recurrence and metastasis. Aberrant epithelial-mesenchymal transition (EMT) has been implicated in the pathogenesis of diverse human malignancies. Immunohistochemical techniques were used to assess EMT-related proteins (E-cadherin, N-cadherin, β-catenin, Snail, and Slug) and the TGF-β1 pathway (TGF-β1 and Smad2/3) proteins expression in different histological subtypes and epithelial mesenchymal compositions of SS. The expression of cell-surface (E-cadherin) and cytoskeletal proteins (β-catenin) were higher significantly in biphasic SSs (BSSs) (70.4%, 51.9%) than MFSSs (both for 10%). Among monophasic fibrous SSs (MFSSs) samples, E-cadherin protein expression was negatively correlated with expression Snail, Slug, TGF-β1, and Smad2/3. The expression levels of Snail and Smad2/3 were correlated with the pTNM stage (I-II vs. III-IV; P=0.047, P=0.021) and TGF-β1 exhibited a tendency toward a positive correlation with pTNM stage (I-II vs. III-IV; P=0.052), but did not correlate with the histological grade (p>0.05). Interestingly, our data showed that expression of E-cadherin protein correlated with greater survival in SS patients. Overexpression of Snail, and TGF-β1 is associated with suppressed expression of E-cadherin in MFSSs, which supports the hypothesis that the MFSS subtype may have developed via neoplastic EMT.

MicroRNAs and triple negative breast cancer

Triple Negative Breast Cancer (TNBC) is a very aggressive tumor subtype, which still lacks specific markers for an effective targeted therapy. Despite the common feature of negativity for the three most relevant receptors (ER, PgR and HER2), TNBC is a very heterogeneous disease where different subgroups can be recognized, and both gene and microRNA profiling studies have recently been carried out to dissect the different molecular entities. Moreover, several microRNAs playing a crucial role in triple negative breast cancer biology have been identified, providing the experimental basis for a possible therapeutic application. Indeed, the causal involvement of microRNAs in breast cancer and the possible use of these small noncoding RNA molecules as biomarkers has been extensively studied with promising results. Their application as therapeutic tools might represent an innovative approach, especially for a tumor subgroup still lacking an efficient and specific therapy such as TNBC. In this review, we summarize our knowledge on the most important microRNAs described in TNBC.

Targeted regulation of PI3K/Akt/mTOR/NF-κB signaling by indole compounds and their derivatives: mechanistic details and biological implications for cancer therapy

Indole compounds, found in cruciferous vegetables, are potent anti-cancer agents. Studies with indole-3-carbinol (I3C) and its dimeric product, 3,3'-diindolylmethane (DIM) suggest that these compounds have the ability to deregulate multiple cellular signaling pathways, including PI3K/Akt/mTOR signaling pathway. These natural compounds are also effective modulators of downstream transcription factor NF-κB signaling which might help explain their ability to inhibit invasion and angiogenesis, and the reversal of epithelial-to-mesenchymal transition (EMT) phenotype and drug resistance. Signaling through PI3K/Akt/mTOR and NF-κB pathway is increasingly being realized to play important role in EMT through the regulation of novel miRNAs which further validates the importance of this signaling network and its regulations by indole compounds. Here we will review the available literature on the modulation of PI3K/Akt/mTOR/NF-κB signaling by both parental I3C and DIM, as well as their analogs/derivatives, in an attempt to catalog their anticancer activity.

Lysosome-dependent p300/FOXP3 degradation and limits Treg cell functions and enhances targeted therapy against cancers

p300 is one of several acetyltransferases that regulate FOXP3 acetylation and functions. Our recent studies have defined a complex set of histone acetyltransferase interactions which can lead to enhanced or repressed changes in FOXP3 function. We have explored the use of a natural p300 inhibitor, Garcinol, as a tool to understand mechanisms by which p300 regulates FOXP3 acetylation. In the presence of Garcinol, p300 appears to become disassociated from the FOXP3 complex and undergoes lysosome-dependent degradation. As a consequence of p300's physical absence, FOXP3 becomes less acetylated and eventually degraded, a process that cannot be rescued by the proteasome inhibitor MG132. p300 plays a complex role in FOXP3 acetylation, as it could also acetylate a subset of four Lys residues that repressively regulate total FOXP3 acetylation. Garcinol acts as a degradation device to reduce the suppressive activity of regulatory T cells (Treg) and to enhance the in vivo anti-tumor activity of a targeted therapeutic anti-p185(her2/neu) (ERBB2) antibody in MMTV-neu transgenics implanted with neu transformed breast tumor cells. Our studies provide the rationale for molecules that disrupt p300 stability to limit Treg functions in targeted therapies for cancers.

Clinical advances in molecular biomarkers for cancer diagnosis and therapy

Cancer diagnosis is currently undergoing a paradigm shift with the incorporation of molecular biomarkers as part of routine diagnostic panel. The molecular alteration ranges from those involving the DNA, RNA, microRNAs (miRNAs) and proteins. The miRNAs are recently discovered small non-coding endogenous single-stranded RNAs that critically regulates the development, invasion and metastasis of cancers. They are altered in cancers and have the potential to serve as diagnostic markers for cancer. Moreover, deregulating their activity offers novel cancer therapeutic approaches. The availability of high throughput techniques for the identification of altered cellular molecules allowed their use in cancer diagnosis. Their application to a variety of body specimens from blood to tissues has been helpful for appreciating their use in the clinical context. The development of innovative antibodies for immunohistochemical detection of proteins also assists in diagnosis and risk stratification. Overall, the novel cancer diagnostic tools have extended their application as prognostic risk factors and can be used as targets for personalized medicine.

Garcinol, a polyisoprenylated benzophenone modulates multiple proinflammatory signaling cascades leading to the suppression of growth and survival of head and neck carcinoma

Constitutive activation of proinflammatory transcription factors such as STAT3 and NF-κB plays a pivotal role in the proliferation and survival of squamous cell carcinoma of the head and neck (HNSCC). Thus, the agents that can modulate deregulated STAT3 and NF-κB activation have a great potential both for the prevention and treatment of HNSCC. In the present report, we investigated the potential effects of garcinol, an active component of Garcinia indica on various inflammatory mediators involved in HNSCC progression using cell lines and xenograft mouse model. We found that garcinol inhibited constitutively activated STAT3 in HNSCC cells in a time- and dose-dependent manner, which correlated with the suppression of the upstream kinases (c-Src, JAK1, and JAK2) in HNSCC cells. Also, we noticed that the generation of reactive oxygen species is involved in STAT3 inhibitory effect of garcinol. Furthermore, garcinol exhibited an inhibitory effect on the constitutive NF-κB activation, mediated through the suppression of TGF-β-activated kinase 1 (TAK1) and inhibitor of IκB kinase (IKK) activation in HNSCC cells. Garcinol also downregulated the expression of various gene products involved in proliferation, survival, and angiogenesis that led to the reduction of cell viability and induction of apoptosis in HNSCC cells. When administered intraperitoneally, garcinol inhibited the growth of human HNSCC xenograft tumors in male athymic nu/nu mice. Overall, our results suggest for the first time that garcinol mediates its antitumor effects in HNSCC cells and mouse model through the suppression of multiple proinflammatory cascades.

Pathways to breast cancer recurrence

Breast cancer remains a deadly disease, even with all the recent technological advancements. Early intervention has made an impact, but an overwhelmingly large number of breast cancer patients still live under the fear of “recurrent” disease. Breast cancer recurrence is clinically a huge problem and one that is largely not well understood. Over the years, a number of factors have been studied with an overarching aim of being able to prognose recurrent disease. This paper attempts to provide an overview of our current knowledge of breast cancer recurrence and its associated challenges. Through a survey of the literature on cancer stem cells (CSCs), epithelial-mesenchymal transition (EMT), various signaling pathways such as Notch/Wnt/hedgehog, and microRNAs (miRNAs), we also examine the hypotheses that are currently under investigation for the prevention of breast cancer recurrence.