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1.  Persistent GP130/STAT3 Signaling Contributes to the Resistance of Doxorubicin, Cisplatin, and MEK Inhibitor in Human Rhabdomyosarcoma Cells 
Current cancer drug targets  2016;16(7):631-638.
To test the role of STAT3 in human rhabdomyosarcoma cells, genetic approaches were used to either knockdown the expression of STAT3 and GP130, an upstream activator of STAT3 using short hairpin RNA (shRNA) or express persistently active STAT3 protein. Knockdown expression of GP130 or STAT3 sensitized cells to anti-cancer drugs doxorubicin, cisplatin, and MEK inhibitor AZD6244. On the other hand, expression of the constitutively active STAT3 protein reduced the sensitivity of rhabdomyosarcoma cells to those drugs.
In addition, we tested a small molecule STAT3 inhibitor LY5 and a GP130 inhibitor bazedoxifene in rhabdomyosarcoma cells. Our data demonstrated that the combination of LY5 or bazedoxifene with doxorubicin, cisplatin, and AZD6244 showed stronger inhibitory effects than single agent alone. In summary, our results demonstrated that GP130/STAT3 signaling contributes to the resistance of these drugs in rhabdomyosarcoma cells. They also suggested a potentially novel cancer therapeutic strategy using the combination of inhibitors of GP130/STAT3 signaling with doxorubicin, cisplatin, or AZD6244 for rhabdomyosarcoma treatments.
PMCID: PMC5014400  PMID: 26373715
STAT3; GP130; rhabdomyosarcoma; cisplatin; doxorubicin; MEK inhibitor
2.  Platycodin D Induces Tumor Growth Arrest by Activating FOXO3a Expression in Prostate Cancer in vitro and in vivo 
Current Cancer Drug Targets  2014;14(9):860-871.
Platycodin D (PD), a major saponin derived from Platycodin grandiflorum, exerted cytotoxicity against prostate cancer cell lines (PC3, DU145 and LNCaP cells) with IC50 values in the range of 11.17 to 26.13μmol/L, whereas RWPE-1cells (a non-malignant human prostate epithelial cell line) were not significantly affected. A further study in these cell lines showed that PD could potently affect cell proliferation (indicated by the bromodeoxyuridine assay), induce cell apoptosis (determined by Annexin V-FITC flow cytometry) and cause cell cycle arrest (indicated by PI staining). After being treated with PD for 48 hours, DU145 and LNCaP cells were arrested in the G0 /G1 phase, and PC3 cells were arrested in the G2/M phase. A Western blotting analysis indicated that PD increased the expression of the FOXO3a transcription factor, decreased the expression of p-FOXO3a and MDM2 and increased the expression of FOXO-responsive genes, p21 and p27. MDM2 silencing (transiently by siRNA-MDM2) increased the PD-induced FOXO3a protein expression, while MDM2 overexpression (in cells transiently transfected with a pcDNA3-MDM2 plasmid) decreased the PD-induced expression of the FOXO3a protein. Moreover, PD dose-dependently inhibited the growth of PC3 xenograft tumors in BALB/c nude mice. A Western blotting analysis of the excised xenograft tumors indicated that similar changes in protein expression also occurred in vivo. These results suggest that PD exhibits significant activity against prostate cancer in vitro and in vivo. The FOXO3a transcription factor appears to be involved in the activity of PD. Together, all of these findings provide a basis for the future development of this agent for human prostate cancer therapy.
PMCID: PMC4997962  PMID: 25431082
Cell cycle; FOXO3a; MDM2; Platycodin D; prostate cancer
3.  Fanconi Anemia Proteins, DNA Interstrand Crosslink Repair Pathways, and Cancer Therapy 
Current cancer drug targets  2009;9(1):101-117.
DNA interstrand crosslinkers, a chemically diverse group of compounds which also induce alkylation of bases and DNA intrastrand crosslinks, are extensively utilized for cancer therapy. Understanding the cellular response to DNA damage induced by these agents is critical for more effective utilization of these compounds and for the identification of novel therapeutic targets. Importantly, the repair of DNA interstrand crosslinks (ICLs) involves many distinct DNA repair pathways, including nucleotide excision repair, translesion synthesis (TLS), and homologous recombination (HR). Additionally, proteins implicated in the pathophysiology of the multigenic disease Fanconi anemia (FA) have a role in the repair of ICLs that is not well understood. Cells from FA patients are hypersensitive to agents that induce ICLs, therefore FA proteins are potentially novel therapeutic targets. Here we will review current research directed at identifying FA genes and understanding the function of FA proteins in DNA damage responses. We will also examine interactions of FA proteins with other repair proteins and pathways, including signaling networks, which are potentially involved in ICL repair. Potential approaches to the modulation of FA protein function to enhance therapeutic outcome will be discussed. Also, mutation of many genes that encode proteins involved in ICL repair, including FA genes, increases susceptibility to cancer. A better understanding of these pathways is therefore critical for the design of individualized therapies tailored to the genetic profile of a particular malignancy. For this purpose, we will also review evidence for the association of mutation of FA genes with cancer in non-FA patients.
PMCID: PMC4934657  PMID: 19200054
Fanconi anemia; DNA interstrand crosslinks; homologous recombination; DNA repair; DNA damage responses; chemotherapy; bifunctional alkylating agents; platinum compounds
4.  Expression of CDK8 and CDK8-interacting Genes as Potential Biomarkers in Breast Cancer 
Current cancer drug targets  2015;15(8):739-749.
CDK8 and its paralog CDK19, in complex with CCNC, MED12 and MED13, are transcriptional regulators that mediate several carcinogenic pathways and the chemotherapy-induced tumor-supporting paracrine network. Following up on our previous observation that CDK8, CDK19 and CCNC RNA expression is associated with shorter relapse-free survival (RFS) in breast cancer, we now found by immunohistochemical analysis that CDK8/19 protein is overexpressed in invasive ductal carcinomas relative to non-malignant mammary tissues. Meta-analysis of transcriptomic data revealed that higher CDK8 expression is associated with shorter RFS in all molecular subtypes of breast cancer. These correlations were much stronger in patients who underwent systemic adjuvant therapy, suggesting that CDK8 impacts the failure of systemic therapy. The same associations were found for CDK19, CCNC and MED13. In contrast, MED12 showed the opposite association with a longer RFS. The expression levels of CDK8 in breast cancer samples were directly correlated with the expression of MYC, as well as CDK19, CCNC and MED13 but inversely correlated with MED12. CDK8, CDK19 and CCNC expression was strongly increased and MED12 expression was decreased in tumors with mutant p53. Gene amplification is the most frequent type of genetic alterations of CDK8, CDK19, CCNC and MED13 in breast cancers (9.7% of which have amplified MED13), whereas point mutations are more common in MED12. These results suggest that the expression of CDK8 and its interactive genes has a profound impact on the response to adjuvant therapy in breast cancer in accordance with the role of CDK8 in chemotherapy-induced tumor-supporting paracrine activities.
PMCID: PMC4755306  PMID: 26452386
Breast cancer; CDK8; CDK19; Cyclin C; MED12; MED13; microarray data mining; tissue microarrays
5.  Procyanidin B2 3,3″-di-O-gallate inhibits endothelial cells growth and motility by targeting VEGFR2 and integrin signaling pathways 
Current cancer drug targets  2015;15(1):14-26.
Targeting angiogenesis, one of the hallmarks of carcinogenesis, using non-toxic phytochemicals has emerged as a translational opportunity for angioprevention and to control advanced stages of malignancy. Herein, we investigated the inhibitory effects and associated mechanism/s of action of Procyanidin B2-3,3″-di-O-gallate (B2G2), a major component of grape seed extract, on human umbilical vein endothelial cells (HUVECs) and human prostate microvascular endothelial cells (HPMECs). Our results showed that B2G2 (10–40 μM) inhibits growth and induces death in both HUVECs and HPMECs. Additional studies revealed that B2G2 causes a G1 arrest in cell cycle progression of HUVECs by down-regulating cyclins (D1 and A), CDKs (Cdk2 and Cdc2) and Cdc25c phosphatase and up-regulating CDK inhibitors (p21 and p27) expression. B2G2 also induced strong apoptotic death in HUVECs through increasing p53, Bax and Smac/Diablo expression while decreasing Bcl-2 and survivin levels. Additionally, B2G2 inhibited the growth factors-induced capillary tube formation in HUVECs and HPMECs. Interestingly, conditioned media (CCM) from prostate cancer (PCA) cells (LNCaP and PC3) grown under normoxic (~21% O2) and hypoxic (1% O2) conditions significantly enhanced the tube formation in HUVECs, which was compromised in presence of conditioned media from B2G2-treated PCA cells. B2G2 also inhibited the motility and invasiveness of both HUVECs and HPMECs. Mechanistic studies showed that B2G2 targets VEGFR2/PI3K/Akt and integrin signaling molecules which are important for endothelial cells survival, proliferation, tube formation and motility. Overall, we report that B2G2 inhibits several attributes of angiogenesis in cell culture; therefore, warrants further investigation for its efficacy for angioprevention and cancer control.
PMCID: PMC4586152  PMID: 25552257
Angioprevention; Apoptosis; B2G2; Cell cycle; Endothelial cells; Integrin; VEGFR2
6.  Cellular FLICE-Like Inhibitory Protein (C-FLIP): A Novel Target for Cancer Therapy 
Current cancer drug targets  2008;8(1):37-46.
Cellular FLICE-like inhibitory protein (c-FLIP) has been identified as a protease-dead, procaspase-8-like regulator of death ligand-induced apoptosis, based on observations that c-FLIP impedes tumor necrosis factor-α (TNF-α), Fas-L, and TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis by binding to FADD and/or caspase-8 or -10 in a ligand-dependent fashion, which in turn prevents death-inducing signaling complex (DISC) formation and subsequent activation of the caspase cascade. c-FLIP is a family of al ternatively spliced variants, and primarily exists as long (c-FLIPL) and short (c-FLIPS) splice variants in human cells. Although c-FLIP has apoptogenic activity in some cell contexts, which is currently attributed to heterodimerization with caspase-8 at the DISC, accumulat ing evidence indicates an anti-apoptotic role for c-FLIP in various types of human cancers. For example, small interfering RNAs (siRNAs) that specifically knocked down expression of c-FLIPL in diverse human cancer cell lines, e.g., lung and cervical cancer cells, augmented TRAIL-induced DISC recruitment, and thereby enhanced effector caspase stimulation and apoptosis. Therefore, the outlook for the therapeutic index of c-FLIP-targeted drugs appears excellent, not only from the efficacy observed in experimental models of cancer therapy, but also because the current understanding of dual c-FLIP action in normal tissues supports the notion that c-FLIP-targeted cancer therapy will be well tolerated. Interestingly, Taxol, TRAIL, as well as several classes of small molecules induce c-FLIP downregulation in neoplastic cells. Efforts are underway to develop small-molecule drugs that induce c-FLIP downregulation and other c-FLIP-targeted cancer therapies. In this review, we assess the outlook for improving cancer therapy through c-FLIP-targeted therapeutics.
PMCID: PMC4524510  PMID: 18288942
Taxol; apoptosis; caspase-8; caspase-10; c-FLIP; leukemia; death receptors
7.  Pleiotropic Role of HSF1 in Neoplastic Transformation 
Current Cancer Drug Targets  2014;14(2):144-155.
HSF1 (Heat Shock transcription Factor 1) is the main transcription factor activated in response to proteotoxic stress. Once activated, it induces an expression of heat shock proteins (HSPs) which enables cells to survive in suboptimal conditions. HSF1 could be also activated by altered kinase signaling characteristic for cancer cells, which is a probable reason for its high activity found in a broad range of tumors. There is rapidly growing evidence that HSF1 supports tumor initiation and growth, as well as metastasis and angiogenesis. It also modulates the sensitivity of cancer cells to therapy. Functions of HSF1 in cancer are connected with HSPs’ activity, which generally protects cells from apoptosis, but also are independent of its classical targets. HSF1-dependent regulation of non-HSPs genes plays a role in cell cycle progression, glucose metabolism, autophagy and drug efflux. HSF1 affects the key cell-survival and regulatory pathways, including p53, RAS/MAPK, cAMP/PKA, mTOR and insulin signaling. Although the exact mechanism of HSF1 action is still somewhat obscure, HSF1 is becoming an attractive target in anticancer therapies, whose inhibition could enhance the effects of other treatments.
PMCID: PMC4435066  PMID: 24467529
cancer; drug resistance; genomic instability; HSF1 inhibitors; HSPs; metastasis; p53 signaling
8.  Target Identification of Grape Seed Extract in Colorectal Cancer using Drug Affinity Responsive Target Stability (DARTS) Technique: Role of Endoplasmic Reticulum Stress Response Proteins 
Current cancer drug targets  2014;14(4):323-336.
Various natural agents, including grape seed extract (GSE), have shown considerable chemopreventive and anti-cancer efficacy against different cancers in pre-clinical studies; however, their specific protein targets are largely unknown and thus, their clinical usefulness is marred by limited scientific evidences about their direct cellular targets. Accordingly, herein, employing, for the first time, the recently developed drug affinity responsive target stability (DARTS) technique, we aimed to profile the potential protein targets of GSE in human colorectal cancer (CRC) cells. Unlike other methods, which can cause chemical alteration of the drug components to allow for detection, this approach relies on the fact that a drug bound protein may become less susceptible to proteolysis and hence the enriched proteins can be detected by Mass Spectroscopy methods. Our results, utilizing the DARTS technique followed by examination of the spectral output by LC/MS and the MASCOT data, revealed that GSE targets endoplasmic reticulum (ER) stress response proteins resulting in overall down regulation of proteins involved in translation and that GSE also causes oxidative protein modifications, specifically on methionine amino acids residues on its protein targets. Corroborating these findings, mechanistic studies revealed that GSE indeed caused ER stress and strongly inhibited PI3k-Akt–mTOR pathway for its biological effects in CRC cells. Furthermore, bioenergetics studies indicated that GSE also interferes with glycolysis and mitochondrial metabolism in CRC cells. Together, the present study identifying GSE molecular targets in CRC cells, combined with its efficacy in vast pre-clinical CRC models, further supports its usefulness for CRC prevention and treatment.
PMCID: PMC4217504  PMID: 24724981
chemoprevention; colorectal cancer; Grape seed extract; DARTS
9.  D-RNAi (Messenger RNA-antisense DNA Interference) as a Novel Defense System Against Cancer and Viral Infections 
Current cancer drug targets  2001;1(3):241-247.
D-RNAi (Messenger RNA-antisense DNA interference), a novel posttranscriptional phenomenon of silencing gene expression by transfection of mRNA-aDNA hybrids, was originally observed in the effects of bcl-2 on phorbol ester-induced apoptosis in human prostate cancer LNCaP cells. This phenomenon was also demonstrated in chicken embryos and a human CD4+ T cell line, H9. The in vivo transduction of β-catenin D-RNAi was shown to knock out more than 99% endogenous β-catenin gene expression, while the in cell transfection of HIV-1 D-RNAi homolog rejected viral gene replication completely. D-RNAi was found to have long-term gene knockout effects resulting from a posttranscriptional gene silencing mechanism that may involve the homologous recombination between intracellular mRNA and the mRNA components of a D-RNAi construct. These findings provide a potential intracellular defense system against cancer and viral infections.
PMCID: PMC4384701  PMID: 12188882
10.  NEDD4: A Promising Target for Cancer Therapy 
Current cancer drug targets  2014;14(6):549-556.
The Neuronally expressed developmentally downregulated 4 (NEDD4), functioning largely as an E3 ubiquitin ligase, has been demonstrated to play a critical role in the development and progression of human cancers. In this review, to understand the regulatory mechanism(s) of NEDD4 as well as the signaling pathways controlled by NEDD4, we briefly describe the NEDD4 upstream regulators and its downstream ubiquitin substrates. Moreover, we further discuss its oncogenic roles in human malignancies. Therefore, targeting NEDD4 could be a potential therapeutic strategy for treatment of human cancers.
PMCID: PMC4302323  PMID: 25088038
Cancer; E3 ligase; NEDD4; oncogene; target; therapy; ubiquitination
11.  Overview of Proteasome Inhibitor-Based Anti-cancer Therapies: Perspective on Bortezomib and Second Generation Proteasome Inhibitors versus Future Generation Inhibitors of Ubiquitin-Proteasome System 
Current cancer drug targets  2014;14(6):517-536.
Over the past ten years, proteasome inhibition has emerged as an effective therapeutic strategy for treating multiple myeloma (MM) and some lymphomas. In 2003, Bortezomib (BTZ) became the first proteasome inhibitor approved by the U.S. Food and Drug Administration (FDA). BTZ-based therapies have become a staple for the treatment of MM at all stages of the disease. The survival rate of MM patients has improved significantly since clinical introduction of BTZ and other immunomodulatory drugs. However, BTZ has several limitations. Not all patients respond to BTZ-based therapies and relapse occurs in many patients who initially responded. Solid tumors, in particular, are often resistant to BTZ. Furthermore, BTZ can induce dose-limiting peripheral neuropathy (PN). The second generation proteasome inhibitor Carfizomib (CFZ; U.S. FDA approved in August 2012) induces responses in a minority of MM patients relapsed from or refractory to BTZ. There is less PN compared to BTZ. Four other second-generation proteasome inhibitors (Ixazomib, Delanzomib, Oprozomib and Marizomib) with different pharmacologic properties and broader anticancer activities, have also shown some clinical activity in bortezomib-resistant cancers. While the mechanism of resistance to bortezomib in human cancers still remains to be fully understood, targeting the immunoproteasome, ubiquitin E3 ligases, the 19S proteasome and deubiquitinases in pre-clinical studies represents possible directions for future generation inhibitors of ubiquitin-proteasome system in the treatment of MM and other cancers.
PMCID: PMC4279864  PMID: 25092212
Bortezomib; carfilzomib; combination therapy; immunoproteasomes; multiple myeloma; proteasome inhibitor; resistance to proteasome inhibitors; ubiquitin-proteasome pathway
12.  Targeting CREB for Cancer Therapy: Friend or Foe 
Current cancer drug targets  2010;10(4):384-391.
The cyclic-AMP response element-binding protein (CREB) is a nuclear transcription factor activated by phosphorylation at Ser133 by multiple serine/threonine (Ser/Thr) kinases. Upon phosphorylation, CREB binds the transcriptional co-activator, CBP (CREB-binding protein), to initiate CREB-dependent gene transcription. CREB is a critical regulator of cell differentiation, proliferation and survival in the nervous system. Recent studies have shown that CREB is involved tumor initiation, progression and metastasis, supporting its role as a proto-oncogene. Overexpression and over-activation of CREB were observed in cancer tissues from patients with prostate cancer, breast cancer, non-small-cell lung cancer and acute leukemia while down-regulation of CREB in several distinct cancer cell lines resulted in inhibition of cell proliferation and induction of apoptosis, suggesting that CREB may be a promising target for cancer therapy. Although CREB, as a transcription factor, is a challenging target for small molecules, various small molecules have been discovered to inhibit CREB phosphorylation, CREB-DNA, or CREB-CBP interaction. These results suggest that CREB is a suitable transcription factor for drug targeting and therefore targeting CREB could represent a novel strategy for cancer therapy.
PMCID: PMC4206256  PMID: 20370681
Cancer; CBP; CREB; inhibitors; KID; KIX; naphthol AS-E; Ro 31-8220
13.  Molecular Targeted Approaches to Cancer Therapy and Prevention Using Chalcones 
Current cancer drug targets  2014;14(2):181-200.
There is an emerging paradigm shift in oncology that seeks to emphasize molecularly targeted approaches for cancer prevention and therapy. Chalcones (1,3-diphenyl-2-propen-1-ones), naturally-occurring compounds with widespread distribution in spices, tea, beer, fruits and vegetables, consist of open-chain flavonoids in which the two aromatic rings are joined by a three-carbon α, β-unsaturated carbonyl system. Due to their structural diversity, relative ease of chemical manipulation and reaction of α, β-unsaturated carbonyl moiety with cysteine residues in proteins, some lead chalcones from both natural products and synthesis have been identified in a variety of screening assays for modulating important pathways or molecular targets in cancers. These pathways and targets that are affected by chalcones include MDM2/p53, tubulin, proteasome, NF-kappa B, TRIAL/death receptors and mitochondria mediated apoptotic pathways, cell cycle, STAT3, AP-1, NRF2, AR, ER, PPAR-γ and β-catenin/Wnt. Compared to current cancer targeted therapeutic drugs, chalcones have the advantages of being inexpensive, easily available and less toxic; the ease of synthesis of chalcones from substituted benzaldehydes and acetophenones also makes them an attractive drug scaffold. Therefore, this review is focused on molecular targets of chalcones and their potential implications in cancer prevention and therapy.
PMCID: PMC4107204  PMID: 24467530
Chalcones; molecular targets; bioactive dietary compounds; chemoprevention
14.  ATM-NF-κB Connection as a Target for Tumor Radiosensitization 
Current cancer drug targets  2007;7(4):335-342.
Ionizing radiation (IR) plays a key role in both areas of carcinogenesis and anticancer radiotherapy. The ATM (ataxia-telangiectasia mutated) protein, a sensor to IR and other DNA-damaging agents, activates a wide variety of effectors involved in multiple signaling pathways, cell cycle checkpoints, DNA repair and apoptosis. Accumulated evidence also indicates that the transcription factor NF-κB (nuclear factor-kappaB) plays a critical role in cellular protection against a variety of genotoxic agents including IR, and inhibition of NF-κB leads to radiosensitization in radioresistant cancer cells. NF-κB was found to be defective in cells from patients with A-T (ataxia-telangiectasia) who are highly sensitive to DNA damage induced by IR and UV lights. Cells derived from A-T individuals are hypersensitive to killing by IR. Both ATM and NF-κB deficiencies result in increased sensitivity to DNA double strand breaks. Therefore, identification of the molecular linkage between the kinase ATM and NF-κB signaling in tumor response to therapeutic IR will lead to a better understanding of cellular response to IR, and will promise novel molecular targets for therapy-associated tumor resistance. This review article focuses on recent findings related to the relationship between ATM and NF-κB in response to IR. Also, the association of ATM with the NF-κB subunit p65 in adaptive radiation response, recently observed in our lab, is also discussed.
PMCID: PMC4156318  PMID: 17979628
ATM; NF-κB; ionizing radiation
15.  Regulation of EMT by KLF4 in Gastrointestinal Cancer 
Current cancer drug targets  2013;13(9):986-995.
Gastrointestinal (GI) cancer is characterized by its aggressiveness, but the underlying mechanism is not fully understood. Studies reveal that epithelial to mesenchymal transition (EMT), which is regulated by a series of transcription factors and signaling pathways, is strongly associated with GI cancer cell proliferation, invasion and metastasis. In essential, EMT is a product of crosstalk between signaling pathways. Krüppel-like factor 4 (KLF4), a zinc finger-type transcription factor, is decreased or lost in most GI cancers. By transcriptional regulating its downstream target genes, KLF4 plays important roles of GI cancer tumorigenesis, proliferation and differentiation. In this review, we focus on the mechanism of KLF4 in GI cancer EMT, and demonstrate that through crosstalk with TGF-β, Notch, and Wnt signaling pathways, KLF4 negatively regulates EMT of GI cancers. Finally, we indicate the challenging new frontiers for KLF4 which contributes to better understanding of the mechanism of GI cancer aggressiveness.
PMCID: PMC4127075  PMID: 24168184
KLF4; gastrointestinal cancer; EMT; TGF-β; Notch; Wnt
16.  Regulation of Mesenchymal Phenotype by MicroRNAs in Cancer 
Current cancer drug targets  2013;13(9):930-934.
Epithelial-mesenchymal transition (EMT) is a developmental process that converts epithelial cells into migratory and invasive cells. This process also plays an important role in cancer progression and metastasis by enabling tumor cells to leave primary sites. EMT is regulated by complex transcription networks and post-transcriptional modulators. MicroRNAs are single-stranded non-coding RNAs that represent a novel class of gene regulators. It has been shown that microRNAs are critical regulators of EMT process. The molecular mechanisms of EMT modulation by microRNAs include the suppression of transcription factors that directly regulate EMT and the down-regulation of cellular genes and pathways that are indirectly involved in EMT process. The expressions of microRNAs that control EMT process are dysregulated in cancer. In this review, we summarize the recent progress of microRNAs in EMT regulation.
PMCID: PMC4100067  PMID: 24168190
microRNA; cancer; epithelial-mesenchymal transition; transcription; non-coding RNA; migration
17.  β-Catenin Knockdown in Liver Tumor Cells by a Cell Permeable Gamma Guanidine-based Peptide Nucleic Acid 
Current cancer drug targets  2013;13(8):867-878.
Hepatocellular cancer (HCC) is the third cause of death by cancer worldwide. In the current study we target β-catenin, an oncogene mutated and constitutively active in 20–30% of HCCs, via a novel, cell permeable gamma guanidine-based peptide nucleic acid (γGPNA) antisense oligonucleotide designed against either the transcription or the translation start site of the human β-catenin gene. Using TOPflash, a luciferase reporter assay, we show that γGPNA targeting the transcription start site showed more robust activity against β-catenin activity in liver tumor cells that harbor β-catenin gene mutations (HepG2 & Snu-449). We identified concomitant suppression of β-catenin expression and of various Wnt targets including glutamine synthetase (GS) and cyclin-D1. Concurrently, γGPNA treatment reduced proliferation, survival and viability of HCC cells. Intriguingly, an angiogenesis quantitative Real-Time-PCR array identified decreased expression of several pro-angiogenic secreted factors such as EphrinA1, FGF-2, and VEGF-A upon β-catenin inhibition in liver tumor cells. Conversely, transfection of stabilized-β-catenin mutants enhanced the expression of angiogenic factors like VEGF-A. Conditioned media from HepG2 cells treated with β-catenin but not the mismatch γGPNA significantly diminished spheroid and tubule formation by SK-Hep1 cells, an HCC-associated endothelial cell line. Thus, we report a novel class of cell permeable and efficacious γGPNAs that effectively targets β-catenin, a known oncogene in the liver. Our study also identifies a novel role of β-catenin in liver tumor angiogenesis through paracrine mechanisms in addition to its roles in proliferation, survival, metabolism and cancer stem cell biology, thus further strengthening its effectiveness as a therapeutic target in HCC.
PMCID: PMC4098753  PMID: 23822752
β-Catenin; Wnt signaling; liver cancer; angiogenesis; proliferation and antisense
18.  Autophagy Fails to Alter Withaferin A-Mediated Lethality in Human Breast Cancer Cells 
Current cancer drug targets  2013;13(6):640-650.
We have shown previously that withaferin A (WA), which is a highly promising anticancer constituent of Ayurvedic medicine plant Withania somnifera, inhibits viability of cultured breast cancer cells in association with reactive oxygen species (ROS)-dependent apoptosis induction. Because ROS production is implicated in induction of autophagy, which is an evolutionary conserved process for bulk degradation of cellular components including organelles (e.g., mitochondria) and considered a valid cancer chemotherapeutic target, we questioned whether WA treatment resulted in autophagy induction. Indeed exposure of MDA-MB-231 and MCF-7 human breast cancer cells as well as a spontaneously immortalized and non-tumorigenic normal human mammary epithelial cell line (MCF-10A) to pharmacologic concentration of WA resulted in autophagy as evidenced by transmission electron microscopy, cleavage of microtubule-associated protein 1 light chain 3 isoform B (LC3B-II), and/or acridine orange staining. Inhibition of MDA-MB-231 xenograft growth in vivo by WA administration was also associated with a significant increase in level of total LC3 protein in the tumor. However, WA-mediated inhibition of MDA-MB-231 and MCF-7 cell viability was not compromised either by pharmacological suppression of autophagy using 3-methyl adenine or genetic repression of autophagy by RNA interference of Atg5, a critical component of the autophagic machinery. Finally, Beclin1 was dispensable for WA-mediated autophagy as well as inhibition of MDA-MB-231 cell viability. Based on these observations we conclude that autophagy induction fails to have any meaningful impact on WA-mediated lethality in breast cancer cells, which may be a therapeutic advantage because autophagy serves to protect against apoptosis by several anticancer agents.
PMCID: PMC3723758  PMID: 23607597
Withaferin A; Breast Cancer; MDA-MB-231; MCF-7; Autophagy; Atg5; Beclin1
19.  Malignant Transformation of Mammary Epithelial Cells by Ectopic Overexpression of the Aryl Hydrocarbon Receptor 
Current cancer drug targets  2011;11(5):654-669.
The aryl hydrocarbon receptor (AhR) is a ligand activated basic helix-loop-helix transcription factor that binds to environmental poly aromatic hydrocarbons (PAH) and mediates their toxic and carcinogenic responses. There is ample documentation for the role of AhR in PAH-induced carcinogenicity. However, in this report we addressed whether overexpression of AhR alone is sufficient to induce carcinogenic transformation in human mammary epithelial cells (HMEC). Retroviral expression vectors were used to develop a series of stable cell lines expressing varying levels of AhR protein in an immortalized normal HMEC with relatively low endogenous AhR expression. The resulted increase in AhR expression and activity correlated with the development of cellular malignant phenotypes, most significantly epithelial-to-mesenchymal transition. Clones overexpressing AhR by more than 3-fold, exhibited a 50% decrease in population doubling time. Cell cycle analysis revealed that this increase in proliferation rates was due to an enhanced cell cycle progression by increasing the percentage of cells transiting into S- and G2/M phases. Cells overexpressing AhR exhibited enhanced motility and migration. Importantly, these cells acquired the ability to invade matrigel matrix, where more than 80% of plated cells invaded the matrigel matrix within 24 h, whereas none of parental or the vector control HMEC were able to invade matrigel. Collectively, these data provide evidence for a direct role of AhR in the progression of breast carcinoma. The results suggest a novel therapeutic target that could be considered for treatment and prevention of breast cancer progression.
PMCID: PMC4070443  PMID: 21486221
aryl hydrocarbon receptor; ectopic overexpression; mammary epithelia; transformation; breast cancer; progression
20.  Targeting Tumor Microenvironment with Silibinin: Promise and Potential for a Translational Cancer Chemopreventive Strategy 
Current cancer drug targets  2013;13(5):486-499.
Tumor microenvironment (TME) refers to the dynamic cellular and extra-cellular components surrounding tumor cells at each stage of the carcinogenesis. TME has now emerged as an integral and inseparable part of the carcinogenesis that plays a critical role in tumor growth, angiogenesis, epithelial to mesenchymal transition (EMT), invasion, migration and metastasis. Besides its vital role in carcinogenesis, TME is also a better drug target because of its relative genetic stability with lesser probability for the development of drug-resistance. Several drugs targeting the TME (endothelial cells, macrophages, cancer-associated fibroblasts, or extra-cellular matrix) have either been approved or are in clinical trials. Recently, non-steroidal anti-inflammatory drugs targeting inflammation were reported to also prevent several cancers. These exciting developments suggest that cancer chemopreventive strategies targeting both tumor and TME would be better and effective towards preventing, retarding or reversing the process of carcinogenesis. Here, we have reviewed the effect of a well established hepatoprotective and chemopreventive agent silibinin on cellular (endothelial, fibroblast and immune cells) and non-cellular components (cytokines, growth factors, proteinases etc.) of the TME. Silibinin targets TME constituents as well as their interaction with cancer cells, thereby inhibiting tumor growth, angiogenesis, inflammation, EMT, and metastasis. Silibinin is already in clinical trials, and based upon completed studies we suggest that its chemopreventive effectiveness should be verified through its effect on biological end points in both tumor and TME. Overall, we believe that the chemopreventive strategies targeting both tumor and TME have practical and translational utility in lowering the cancer burden.
PMCID: PMC3924886  PMID: 23617249
Angiogenesis; Chemoprevention; Inflammation; Metastasis; Silibinin; Tumor microenvironment
21.  Novel and Emerging Drugs for Acute Myeloid Leukemia 
Current cancer drug targets  2012;12(5):522-530.
Acute myeloid leukemia (AML) is a challenging disease to treat with the majority of patients dying from their illness. While overall survival has been markedly prolonged in acute promyelocytic leukemia (APL), survival in younger adults with other subtypes of AML has only modestly improved over the last twenty years. Physicians who treat AML eagerly await drugs like Imatinib for chronic myeloid leukemia, Cladribine for hairy cell leukemia, and Rituximab for non-Hodgkin Lymphoma which have had an important impact on improving outcome. Recent research efforts have focused on refining traditional chemotherapeutic agents to make them more active in AML, targeting specific genetic mutations in myeloid leukemia cells, and utilizing novel agents such as Lenalidomide that have shown activity in other hematologic malignancies. Here, we focus on reviewing the recent literature on agents that may assume a role in clinical practice for patients with AML over the next five years.
PMCID: PMC4030742  PMID: 22483153
Acute Myeloid Leukemia; novel drugs; emerging agents
22.  Ras-induced Senescence and its Physiological Relevance in Cancer 
Current cancer drug targets  2010;10(8):869-876.
Because activated oncogenes like Ras have traditionally been thought as promoting unrestrained proliferation, the concept of oncogene-induced senescence has been, and still is, controversial. The counter-intuitive notion that activation of oncogenes leads to the prevention of cellular proliferation has initially been fueled by in vitro studies using ectopic expression of activated Ras in primary fibroblasts. While these initial studies demonstrated unambiguously the existence of a new type of cellular senescence, induced by oncogenes in an ex-vivo system, questions were raised about the physiological relevance of this process. Indeed, recent technical advances in mouse modeling for cancer have suggested that the occurrence of Ras-induced senescence is highly dependent on the cellular context, as well as the level of expression of activated Ras, and may not be pertinent to the study of human cancer initiation and/or progression. However, our increased knowledge of the molecular basis for cellular senescence has led to a better understanding of the molecular events modulating cancer progression in vivo. Recent studies have not only clearly established the incidence of cellular senescence in pre-neoplasic lesions, but also its role as a potential tumor-suppressor mechanism in vivo. Here, we review the recent and exciting new findings regarding the physiological relevance of Ras-induced senescence, and discuss their implications in terms of cancer therapy.
PMCID: PMC4023163  PMID: 20718709
Senescence; cell cycle; cancer; chromatin; Rb; SAHF; SASP
23.  The Role of Snail in EMT and Tumorigenesis 
Current cancer drug targets  2013;13(9):963-972.
Epithelial-mesenchymal transition (EMT) is a highly conserved process in which polarized, immotile epithelial cells lose adherent and tight junctions, and become migratory mesenchymal cells. As a key transcriptional repressor of E-cadherin expression in EMT, Snail plays an important role in embryonic development and cancer progression. Emerging evidences indicate that Snail confers tumor cells with cancer stem cell-like traits, and promotes drug resistance, tumor recurrence and metastasis. In this review, we summarize recent developments underlying the regulation and functions of Snail in tumor progression, and discuss new approaches against EMT in preventing metastatic cancers.
PMCID: PMC4004763  PMID: 24168186
Breast cancer; EMT; metastasis; signaling pathway; Snail
24.  Emerging Role of Mucins in Epithelial to Mesenchymal Transition 
Current cancer drug targets  2013;13(9):945-956.
Epithelial to mesenchymal transition (EMT) is an important and complex phenomenon that determines the aggressiveness of cancer cells. The morphological transformation of cancerous cells is accompanied by various cellular processes such as alterations in cell-cell adhesion, cell matrix degradation, down regulation of epithelial marker E-cadherin and upregulation of mesenchymal markers N-cadherin and Vimentin. Besides these markers several other important tumor antigens/mucins are also involved in the EMT process. Mainly high molecular weight glycoproteins such as mucin molecules (MUC1, MUC4 and MUC16) play a major role in the cellular transformation and signaling alteration in EMT process. In addition to these factors, EMT may be an essential process triggering the emergence or expansion of the CSC population, which slowly results in the initiation of tumor at metastatic sites. Furthermore, mucins have been demonstrated to be involved in the EMT process and also in the enrichment of cancer stem cell population. Mucin mediated EMT is very complex since the key components of tumor microenvironment are also regulating mucin molecules. In this review, we have discussed all the aforementioned factors and their mechanistic involvement for EMT process.
PMCID: PMC3924542  PMID: 24168188
EMT transcription factors; EMT signaling; Mucins; MUC1; MUC4; MUC16; Cancer stem cells; Tumor microenvironment
25.  The Biology of the Sodium Iodide Symporter and its Potential for Targeted Gene Delivery 
Current cancer drug targets  2010;10(2):242-267.
The sodium iodide symporter (NIS) is responsible for thyroidal, salivary, gastric, intestinal and mammary iodide uptake. It was first cloned from the rat in 1996 and shortly thereafter from human and mouse tissue. In the intervening years, we have learned a great deal about the biology of NIS. Detailed knowledge of its genomic structure, transcriptional and post-transcriptional regulation and pharmacological modulation has underpinned the selection of NIS as an exciting approach for targeted gene delivery. A number of in vitro and in vivo studies have demonstrated the potential of using NIS gene therapy as a means of delivering highly conformal radiation doses selectively to tumours. This strategy is particularly attractive because it can be used with both diagnostic (99mTc, 125I, 124I) and therapeutic (131I, 186Re, 188Re, 211At) radioisotopes and it lends itself to incorporation with standard treatment modalities, such as radiotherapy or chemoradiotherapy. In this article, we review the biology of NIS and discuss its development for gene therapy.
PMCID: PMC3916908  PMID: 20201784

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