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1.  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
2.  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
3.  Non-Coding RNAs as Therapeutic Targets in Hepatocellular Cancer 
Current cancer drug targets  2012;12(9):1073-1080.
Hepatocellular carcinoma (HCC) is a common malignancy that affects a large number of patients worldwide, with an increasing incidence in the United States and Europe. The therapies that are currently available for patients with inoperable HCC have limited benefits. Although molecular targeted therapies against selected cell signaling pathways have shown some promising results, their impact has been minimal. There is a need to identify and explore other targets for the development of novel therapeutics. Several non-protein coding RNAs (ncRNA) have recently been implicated in hepatocarcinogenesis and tumor progression. These ncRNA genes represent promising targets for cancer. However, therapeutic targeting of ncRNA genes has not been employed for HCC. The use of antisense oligonucleotides and viral vector delivery approaches has been shown to be feasible approaches to modulate ncRNA expression. HCC is an optimal cancer to evaluate novel RNA based therapeutic approaches because of the potential of effective delivery and uptake of therapeutic agents to the liver. In this review, we discuss selected ncRNA that could function as potential targets in HCC treatment and outline approaches to target ncRNA expression. Future challenges include the need to achieve site-specific targeting with acceptable safety and efficacy.
PMCID: PMC3916140  PMID: 22873215
Antagomirs; HCC; LNA-antimiR; miRNA; non-coding RNA; ultraconserved
4.  HtrA Serine Proteases as Potential Therapeutic Targets in Cancer 
Current cancer drug targets  2009;9(4):451-468.
The human HtrA family of serine proteases consists of four members: HtrA1, HtrA2, HtrA3 and HtrA4. Although prokaryotic HtrA proteins are well characterized in their dual roles as chaperones and proteases that degrade misfolded proteins in the periplasm, some members of mammalian HtrA proteins are described as potential modulators of programmed cell death and chemotherapy-induced cytotoxicity. Goal of this review article is to describe the molecular alterations associated with these HtrA serine proteases and how these alterations may be associated with tumor behavior and response to chemotherapy. We will also discuss evidence that chemotherapeutic drugs regulate the expression and activation of HtrA serine proteases and that these proteases contributes to programmed cell death. Finally, we will discuss the potential role of epigenetic therapy in targeting the expression and activation of HtrA serine proteases and the mechanisms by which these proteases enhance cytotoxic effect of conventional chemotherapy.
PMCID: PMC3905973  PMID: 19519315
5.  The Histone Deacetylase Inhibitor, MS-275 (Entinostat), Downregulates c-FLIP, Sensitizes Osteosarcoma Cells to FasL, and Induces the Regression of Osteosarcoma Lung Metastases 
Current cancer drug targets  2013;13(4):411-422.
The purpose of this study was to determine the effects of the histone deacetylase inhibitor, MS-275, on the Fas signaling pathway and susceptibility of osteosarcoma (OS) to Fas ligand (FasL)-induced cell death. OS metastasizes almost exclusively to the lungs. We have shown that Fas expression in OS cells is inversely correlated with their metastatic potential. Fas+ cells are rapidly eliminated when they enter the lungs via interaction with FasL, which is constitutively expressed in the lungs. Fas− OS cells escape this FasL-induced apoptosis and survive in the lung microenvironment. Moreover, upregulation of Fas in established OS lung metastases results in tumor regression. Therefore, agents that upregulate Fas expression or activate the Fas signaling pathway may have therapeutic potential. Treatment of Fas− metastatic OS cell lines with 2 μM MS-275 sensitized cells to FasL-induced cell death in vitro. We found that MS-275 did not alter the expression of Fas on the cell surface; rather it resulted in the downregulation of the anti-apoptotic protein, c-FLIP (cellular FLICE-inhibitory protein), by inhibiting c-FLIP mRNA. Downregulation of c-FLIP correlated with caspase activation and apoptosis induction. Treatment of nu/nu-mice with established OS lung metastases with oral MS-275 resulted in tumor regression, increased apoptosis and a significant inhibition of c-FLIP expression in tumors. Histopathological examination of mice showed no evidence of significant toxicity. Overall, these results suggest that the mechanism by which MS-275 sensitizes OS cells and lung metastases to FasL-induced cell death may be by a direct reduction in the expression of c-FLIP.
PMCID: PMC3878976  PMID: 23410027
c-FLIP; Fas; FasL; histone deacetylase inhibitors; MS-275; Entinostat; osteosarcoma
6.  Targeting Epigenetics through Histone Deacetylase Inhibitors in Acute Lymphoblastic Leukemia 
Current cancer drug targets  2011;11(7):882-893.
Epigenetics play a critical role in controlling normal gene expression and altered epigenetics can lead to abnormal cellular differentiation, proliferation and survival. Acute lymphoblastic leukemia (ALL) is the most common malignancy in children and is characterized by numerous epigenetic abnormalities. These epigenetic changes correspond to repressed activity of some genes and inappropriate activation of others. In contrast to genetic alterations stemming from mutations, deletions or translocation, epigenetic changes are relatively reversible when treated with certain small molecule-based anticancer agents. Histone deacetylase inhibitors (HDI) are a class of drugs capable of modifying the epigenetic status of ALL cells. Several recent preclinical and clinical studies have demonstrated the potential of HDI as therapeutic agents in ALL. This review summarizes recent studies on (1) the principles of epigenetics and their importance in ALL tumorigenesis; (2) the structure, mechanism of action and anti-tumor activity of HDI; (3) the first comprehensive summary of data from preclinical and clinical studies for HDI as the therapeutic agents for ALL; and (4) novel directions for future research on HDI and ALL.
PMCID: PMC3855493  PMID: 21762078 CAMSID: cams3770
Leukemia; epigenetics; histone deacetylase inhibitors; therapeutic agent; anticancer agent; small molecule inhibitors
7.  Reactivation of p53 by Novel MDM2 Inhibitors: Implications for Pancreatic Cancer Therapy 
Current cancer drug targets  2010;10(3):319-331.
The present study is the first to show in pancreatic cancer (PC) the growth inhibition and apoptosis by novel MDM2 inhibitors (MI-319 & 219) through reactivation of p53 pathway. Our results highlight two new secondary targets of MDM2 inhibitor ‘SIRT1’ and Ku70. SIRT1 has a role in ageing and cancer and is known to regulate p53 signaling through acetylation. Ku70 is a key component of non-homologous end joining machinery in the DNA damage pathway and is known to regulate apoptosis by blocking Bax entry into mitochondria. Given the growth inhibition and apoptosis by MI-219, MI-319 was accompanied by increase in levels of p53 along with p21WAF1 and the proapoptotic Puma. SiRNA against p21WAF1 abrogated the growth inhibition of PC cells confirming p21WAF1 as a key player downstream of activated p53. Immunoprecipitation-western blot analysis revealed reduced association of MDM2-p53 interaction in drug exposed PC cells. In combination studies, the inhibitors synergistically augmented anti-tumor effects of therapeutic drug gemcitabine both in terms of cell growth inhibition as well as apoptosis. Surface plasmon resonance studies confirmed strong binding between MI-319 and Ku70 (KD 170 nM). Western blot revealed suppression of SIRT1 and Ku70 with simultaneous upregulation of acetyl-p53 (Lys379) and Bax. Co-Immunoprecipitation studies confirmed that MI-319 could disrupt Ku70-Bax and SIRT1-Bax interaction. Further, using wt-p53 xenograft of Capan-2, we found that oral administration of MI-319 at 300 mg/kg for 14 days resulted in significant tumor growth inhibition without any observed toxicity to the animals. No tumor inhibition was found in mut-p53 BxPC-3 xenografts. In light of our results, the inhibitors of MDM2 warrant clinical investigation as new agents for PC treatment.
PMCID: PMC3809102  PMID: 20370686
MDM2 and p53; Small molecule inhibitors; cell cycle arrest; apoptosis; pancreatic cancer
8.  Cyclooxygenase-2 (COX-2) Mediates Arsenite Inhibition of UVB-Induced Cellular Apoptosis in Mouse Epidermal Cl41 Cells 
Current cancer drug targets  2012;12(6):607-616.
Inorganic arsenic is an environmental human carcinogen, and has been shown to act as a co-carcinogen with solar ultraviolet (UV) radiation in mouse skin tumor induction even at low concentrations. However, the precise mechanism of its co-carcinogenic action is largely unknown. Apoptosis plays an essential role as a protective mechanism against neoplastic development in the organism by eliminating genetically damaged cells. Thus, suppression of apoptosis is thought to contribute to carcinogenesis. It is known that cyclooxygenase-2 (COX-2) can promote carcinogenesis by inhibiting cell apoptosis under stress conditions; and our current studies investigated the potential contribution of COX-2 to the inhibitory effect of arsenite in UV-induced cell apoptosis in mouse epidermal Cl41 cells. We found that treatment of cells with low concentration (5 μM) arsenite attenuated cellular apoptosis upon UVB radiation accompanied with a co-inductive effect on COX-2 expression and nuclear factor-κB (NFκB) transactivation. Our results also showed that the COX-2 induction by arsenite and UVB depended on an NFκB pathway because COX-2 co-induction could be attenuated in either p65-deficient or p50-deficient cells. Moreover, UVB-induced cell apoptosis could be dramatically reduced by the introduction of exogenous COX-2 expression, whereas the inhibitory effect of arsenite on UVB-induced cell apoptosis could be impaired in COX-2 knockdown Cl41 cells. Our results indicated that COX-2 mediated the anti-apoptotic effect of arsenite in UVB radiation through an NFκB-dependent pathway. Given the importance of apoptosis evasion during carcinogenesis, we anticipated that COX-2 induction might be at least partially responsible for the co-carcinogenic effect of arsenite on UVB-induced skin carcinogenesis.
PMCID: PMC3782088  PMID: 22463588
Apoptosis; arsenite; COX-2; NF-κB; UVB
9.  Prevention of hepatocellular carcinoma: potential targets, experimental models, and clinical challenges 
Current cancer drug targets  2012;12(9):1129-1159.
Chronic fibrotic liver diseases such as viral hepatitis eventually develop liver cirrhosis, which causes occurrence of hepatocellular carcinoma (HCC). Given the limited therapeutic efficacy in advanced HCC, prevention of HCC development could be an effective strategy for improving patient prognosis. However, there is still no established therapy to meet the goal. Studies have elucidated a wide variety of molecular mechanisms and signaling pathways involved in HCC development. Genetically-engineered or chemically-treated experimental models of cirrhosis and HCC have been developed and shown their potential value in investigating molecular therapeutic targets and diagnostic biomarkers for HCC prevention. In this review, we overview potential targets of prevention and currently available experimental models, and discuss strategies to translate the findings into clinical practice.
PMCID: PMC3776581  PMID: 22873223
Animal model; chemoprevention; clinical trial; hepatocellular carcinoma; liver cirrhosis; prevention
10.  Gadd45 Proteins as Critical Signal Transducers Linking NF-κB to MAPK Cascades 
Current cancer drug targets  2009;9(8):915-930.
The growth arrest and DNA damage-inducible 45 (Gadd45) proteins are a group of critical signal transducers that are involved in regulations of many cellular functions. Accumulated data indicate that all three Gadd45 proteins (i.e., Gadd45α, Gadd45β, and Gadd45γ) play essential roles in connecting an upstream sensor module, the transcription Nuclear Factor-κB (NF-κB), to a transcriptional regulating module, mitogen-activated protein kinase (MAPK). This NF-κB-Gadd45(s)-MAPK pathway responds to various kinds of extracellular stimuli and regulates such cell activities as growth arrest, differentiation, cell survival, and apoptosis. Defects in this pathway can also be related to oncogenesis. In the first part of this review, the functions of Gadd45 proteins, and briefly NF-κB and MAPK, are summarized. In the second part, the mechanisms by which Gadd45 proteins are regulated by NF-κB, and how they affect MAPK activation, are reviewed.
PMCID: PMC3762688  PMID: 20025601
GADD45α; Gadd45β; Gadd45γ; NF-κB; JNK; P38; Cell survival and apoptosis
11.  Bid Mediates Anti-Apoptotic COX-2 Induction Through the IKKβ/NFκB Pathway Due to 5-MCDE Exposure 
Current cancer drug targets  2010;10(1):96-106.
Although Bid is considered to be a cell apoptotic mediator, current studies suggest that it has a possible role in cell survival for mouse embryonic fibroblasts (MEFs) in response to low doses of anti-(±)-5- methylchrysene-l,2-diol-3,4-epoxide (<0.25µM) (5-MCDE). We found that the exposure of MEFs to 0.25 µM 5-MCDE resulted in a slight apoptotic induction, while this apoptotic response was substantially increased in the Bid knockout MEFs (Bid−/−), suggesting that there is a Bid-mediated anti-apoptotic function in this response. This notion was further supported by the findings that re-constitution expression of Bid into Bid−/− cells could inhibit the increased apoptosis. Further studies show that the antiapoptotic function of Bid was associated with its mediation of COX-2 expression. This conclusion was based the reduction of COX-2 expression in Bid−/− cells, the restoration of low sensitivity to 5-MCDE-induced apoptosis by the introduction of Bid into Bid−/− cells, and increased sensitivity of WT MEFs to 5-MCDE-induced apoptosis by the knockdown of COX-2 expression. Furthermore, we found that Bid mediated COX-2 expression through the IKKβ/NFκB pathway because the deficiency of Bid in Bid−/− MEFs resulted in the blockade of IKK/NFκB activation and knockout of IKKβ caused abrogation of COX-2 expression induced by 5-MCDE. Collectively, our results demonstrate that Bid is critical for COX-2 induction through the IKKβ/NFκB pathway, which mediates its anti-apoptotic function, in cell response to low doses of 5-MCDE exposure.
PMCID: PMC3759233  PMID: 20088789
Bid; COX-2; 5-MCDE; NFκB; apoptosis
12.  A Cross-Talk Between NFAT and NF-κB Pathways is Crucial for Nickel-Induced COX-2 Expression in Beas-2B Cells 
Current cancer drug targets  2011;11(5):548-559.
Cyclooxygenase-2 (COX-2) is a critical enzyme implicated in chronic inflammation-associated cancer development. Our studies have shown that the exposure of Beas-2B cells, a human bronchial epithelial cell line, to lung carcinogenic nickel compounds results in increased COX-2 expression. However, the signaling pathways leading to nickel-induced COX-2 expression are not well understood. In the current study, we found that the exposure of Beas-2B cells to nickel compounds resulted in the activation of both nuclear factor of activated T cell (NFAT) and nuclear factor-κB (NF-κB). The expression of COX-2 induced upon nickel exposure was inhibited by either a NFAT pharmacological inhibitor or the knockdown of NFAT3 by specific siRNA. We further found that the activation of NFAT and NF-κB was dependent on each other. Since our previous studies have shown that NF-κB activation is critical for nickel-induced COX-2 expression in Beas-2B cells exposed to nickel compounds under same experimental condition, we anticipate that there might be a cross-talk between the activation of NFAT and NF-κB for the COX-2 induction due to nickel exposure in Beas-2B cells. Furthermore, we showed that the scavenging of reactive oxygen species (ROS) by introduction of mitochondrial catalase inhibited the activation of both NFAT and NF-κB, and the induction of COX-2 due to nickel exposure. Taken together, our results defining the evidence showing a key role of the cross-talk between NFAT and NF-κB pathways in regulating nickel-induced COX-2 expression, further provide insight into the understanding of the molecular mechanisms linking nickel exposure to its lung carcinogenic effects.
PMCID: PMC3759234  PMID: 21486220
Beas-2B cells; COX-2; nickel; NFAT; NF-κB; ROS
13.  PI3K/Akt/JNK/c-Jun Signaling Pathway is a Mediator for Arsenite-Induced Cyclin D1 Expression and Cell Growth in Human Bronchial Epithelial Cells 
Current cancer drug targets  2009;9(4):500-509.
Arsenite exposure is associated with an increased risk of human lung cancer. However, the molecular mechanisms underlying the arsenite-induced human lung carcinogenesis remain elusive. In this study, we demonstrated that arsenite upregulates cyclin D1 expression/activity to promote the growth of human bronchial epithelial Beas-2B cells. In this process, the JNKs (c-Jun N-terminal kinases)/c-Jun cascade is elicited. The inhibition of JNKs or c-Jun by chemical or genetic inhibitors blocks the cyclin D1 induction mediated by arsenite. Furthermore, using a loss of function mutant of p85 (Δp85, a subunit of PI3K) or dominant-negative Akt (DN-Akt), we showed that PI3K and Akt act as the upstream regulators of JNKs and c-Jun in arsenite-mediated growth promotion. Overall, our data suggest a pathway of PI-3K/Akt/JNK/c-Jun/cylin D1 signaling in response to arsenite in human bronchial epithelial cells.
PMCID: PMC3758122  PMID: 19519318
PI-3K; Akt; JNK; c-Jun; cyclin D1; arsenite; cell proliferation
14.  Jaridonin, a Novel Ent-Kaurene Diterpenoid from Isodon rubescens, Inducing Apoptosis via Production of Reactive Oxygen Species in Esophageal Cancer Cells 
Current cancer drug targets  2013;13(6):611-624.
Isodon rubescens, a Chinese herb, has been used as a folk, botanical medicine in China for inflammatory diseases and cancer treatment for many years. Recently, we isolated a new ent-kaurene diterpenoid, named Jaridonin, from Isodon rubescens. The chemical structure of Jaridonin was verified by Infrared (IR), Nuclear magnetic resonance (NMR), and Mass spectrum (MS) data as well as X-ray spectra. Jaridonin potently reduced viabilities of several esophageal cancer cell lines, including EC109, EC9706 and EC1. Jaridonin treatment resulted in typical apoptotic morphological characteristics, increased the number of annexin V-positive staining cells, as well as caused a G2/M arrest in cell cycle progression. Furthermore, Jaridonin resulted in a significant loss of mitochondrial membrane potential, release of cytochrome c into the cytosol, and then activation of Caspase-9 and -3, leading to activation of the mitochondria mediated apoptosis. Furthermore, these effects of Jaridonin were accompanied by marked reactive oxygen species (ROS) production and increased expression of p53, p21waf1/Cip1 and Bax, whereas two ROS scavengers, N-acetyl-L-cysteine (L-NAC) and Vitamin C, significantly attenuated the effects of Jaridonin on the mitochondrial membrane potential, DNA damage, expression of p53 and p21waf1/Cip1 and reduction of cell viabilities. Taken together, our results suggest that a natural ent-kaurenoid diterpenoid, Jaridonin, is a novel apoptosis inducer and deserves further investigation as a new chemotherapeutic strategy for patients with esophageal cancer.
PMCID: PMC3750090  PMID: 23597192
Apoptosis; ent-kaurene diterpenoid; esophageal cancer; mitochondria pathway; rabdosia rubescens; reactive oxygen species
15.  The Biological Functions of NF-κB1 (p50) and its Potential as an Anti-Cancer Target 
Current cancer drug targets  2009;9(4):566-571.
Nuclear factor-κB (NF-κB) is a key transcriptional factor family that consists of five members in mammalian cells, including NF-κB1 (p50), NF-κB2 (p52), RelA (p65), RelB and c-Rel. NF-κB is implicated in multiple physiological and pathological processes, including cell proliferation and differentiation, inflammatory and immune response, cell survival and apoptosis, cellular stress reactions and tumorigenesis. Recent studies by our group and others have highlighted the novel functions of the p50 protein. In this review, we will focus on the regulation and functions of NF-κB p50.
PMCID: PMC3747820  PMID: 19519322
16.  Marizomib, a Proteasome Inhibitor for All Seasons: Preclinical Profile and a Framework for Clinical Trials 
Current cancer drug targets  2011;11(3):254-284.
The proteasome has emerged as an important clinically relevant target for the treatment of hematologic malignancies. Since the Food and Drug Administration approved the first-in-class proteasome inhibitor bortezomib (Velcade®) for the treatment of relapsed/refractory multiple myeloma (MM) and mantle cell lymphoma, it has become clear that new inhibitors are needed that have a better therapeutic ratio, can overcome inherent and acquired bortezomib resistance and exhibit broader anti-cancer activities. Marizomib (NPI-0052; salinosporamide A) is a structurally and pharmacologically unique β-lactone-γ-lactam proteasome inhibitor that may fulfill these unmet needs. The potent and sustained inhibition of all three proteolytic activities of the proteasome by marizomib has inspired extensive preclinical evaluation in a variety of hematologic and solid tumor models, where it is efficacious as a single agent and in combination with biologics, che-motherapeutics and targeted therapeutic agents. Specifically, marizomib has been evaluated in models for multiple myeloma, mantle cell lymphoma, Waldenstrom’s macroglobulinemia, chronic and acute lymphocytic leukemia, as well as glioma, colorectal and pancreatic cancer models, and has exhibited synergistic activities in tumor models in combination with bortezomib, the immunomodulatory agent lenalidomide (Revlimid®), and various histone deacetylase inhibitors. These and other studies provided the framework for ongoing clinical trials in patients with MM, lymphomas, leukemias and solid tumors, including those who have failed bortezomib treatment, as well as in patients with diagnoses where other proteasome inhibitors have not demonstrated significant efficacy. This review captures the remarkable translational studies and contributions from many collaborators that have advanced marizomib from seabed to bench to bedside.
PMCID: PMC3712795  PMID: 21247382
Proteasome inhibitor; marizomib; bortezomib; NF-κB; multiple myeloma; pharmacodynamics; combination therapy
17.  Histone Lysine-Specific Methyltransferases and Demethylases in Carcinogenesis: New Targets for Cancer Therapy and Prevention 
Current cancer drug targets  2013;13(5):558-579.
Aberrant histone lysine methylation that is controlled by histone lysine methyltransferases (KMTs) and demethylases (KDMs) plays significant roles in carcinogenesis. Infections by tumor viruses or parasites and exposures to chemical carcinogens can modify the process of histone lysine methylation. Many KMTs and KDMs contribute to malignant transformation by regulating the expression of human telomerase reverse transcriptase (hTERT), forming a fused gene, interacting with proto-oncogenes or being up-regulated in cancer cells. In addition, histone lysine methylation participates in tumor suppressor gene inactivation during the early stages of carcinogenesis by regulating DNA methylation and/or by other DNA methylation independent mechanisms. Furthermore, recent genetic discoveries of many mutations in KMTs and KDMs in various types of cancers highlight their numerous roles in carcinogenesis and provide rare opportunities for selective and tumor-specific targeting of these enzymes. The study on global histone lysine methylation levels may also offer specific biomarkers for cancer detection, diagnosis and prognosis, as well as for genotoxic and non-genotoxic carcinogenic exposures and risk assessment. This review summarizes the role of histone lysine methylation in the process of cellular transformation and carcinogenesis, genetic alterations of KMTs and KDMs in different cancers and recent progress in discovery of small molecule inhibitors of these enzymes.
PMCID: PMC3703250  PMID: 23713993
Histone lysine-specific methyltransferases; histone lysine-specific demethylases; cell transformation; carcinogenesis; gene mutations; inhibitors
18.  Diverse mechanisms of AKT pathway activation in human malignancy 
Current cancer drug targets  2013;13(3):234-244.
AKT/PKB (Protein Kinase B) are central proteins mediating signals from receptor tyrosine kinases and phosphatidylinositol 3-kinase. AKT kinases are involved in a number of important cellular processes including cell proliferation and survival, cell size in response to nutrient availability, tumor invasion/metastasis, and angiogenesis. Various components of the AKT signaling pathway are encoded by tumor suppressor genes and oncogenes whose loss or activation, respectively, plays an important role in tumorigenesis. The growing body of evidence connecting deregulated AKT signaling with sporadic human cancers and inherited cancer predisposition syndromes is discussed. We also highlight new findings regarding the involvement of activating mutations of AKT1, AKT2, and AKT3 in somatic overgrowth disorders: Proteus syndrome, hypoglycemia with hypertrophy, and hemimegalencephaly, respectively. In addition, we review recent literature documenting the various ways the AKT signaling pathway is activated in human cancers and consequences for molecularly targeted therapies.
PMCID: PMC3678724  PMID: 23297823
AKT/PKB kinases; tumor suppressor genes; oncogenes; human malignancy; targeted therapies; Proteus syndrome; hypoglycemia; hemimegalencephaly
19.  Myeloid-derived suppressor cells: general characteristics and relevance to clinical management of pancreatic cancer 
Current cancer drug targets  2011;11(6):734-751.
Recent studies describe a heterogeneous population of cells of the myeloid lineage, termed myeloid derived suppressor cells (MDSC), which are observed with increased prevalence in the peripheral blood and tumor microenvironment of cancer patients, including pancreatic cancer. Accumulation of MDSC in the peripheral circulation has been related to extent of disease, and correlates with stage. MDSC have primarily been implicated in promoting tumor growth by suppressing antitumor immunity. There is also compelling evidence MDSC are also involved in angiogenesis and metastatic spread.
Two main subsets of MDSC have been identified in cancer patients: a monocytic subset, characterized by expression of CD14, and a granulocytic subset characterized by expression of CD15. Both subsets of MDSC actively suppress host immunity through a variety of mechanisms including production of reactive oxygen species and arginase. Just as in humans, accumulation of monocytic and granulocytic MDSC has been noted in the bone marrow, spleen, peripheral circulation, and tumors of tumor bearing mice.
Successful targeting of MDSC in mice is associated with improved immune responses, delayed tumor growth, improved survival, and increased efficacy of vaccine therapy. By further elucidating mechanisms of MDSC recruitment and maintenance in the tumor environment, strategies could be developed to reverse immune tolerance to tumor. We discuss here what is currently known about MDSC as well as some potential strategies targeting MDSC in the context of our work on pancreatic cancer and recent literature. Due to the number of new reports on MDSC, the most pertinent ones have been selected.
PMCID: PMC3670669  PMID: 21599634
myeloid-derived suppressor cells; pancreatic cancer; immune suppression; bone marrow; metastasis
20.  The Role of Fibroblast Growth Factors in Tumor Growth 
Current cancer drug targets  2009;9(5):639-651.
Biological processes that drive cell growth are exciting targets for cancer therapy. The fibroblast growth factor (FGF) signaling network plays a ubiquitous role in normal cell growth, survival, differentiation, and angiogenesis, but has also been implicated in tumor development. Elucidation of the roles and relationships within the diverse FGF family and of their links to tumor growth and progression will be critical in designing new drug therapies to target FGF receptor (FGFR) pathways. Recent studies have shown that FGF can act synergistically with vascular endothelial growth factor (VEGF) to amplify tumor angiogenesis, highlighting that targeting of both the FGF and VEGF pathways may be more efficient in suppressing tumor growth and angiogenesis than targeting either factor alone. In addition, through inducing tumor cell survival, FGF has the potential to overcome chemotherapy resistance highlighting that chemotherapy may be more effective when used in combination with FGF inhibitor therapy. Furthermore, FGFRs have variable activity in promoting angiogenesis, with the FGFR-1 subgroup being associated with tumor progression and the FGFR-2 subgroup being associated with either early tumor development or decreased tumor progression. This review highlights the growing knowledge of FGFs in tumor cell growth and survival, including an overview of FGF intracellular signaling pathways, the role of FGFs in angiogenesis, patterns of FGF and FGFR expression in various tumor types, and the role of FGFs in tumor progression.
PMCID: PMC3664927  PMID: 19508171
Fibroblast growth factors; gene expression regulation; neoplasms; angiogenesis/neovascularization; molecular targets
21.  The gene expression profiles of medulloblastoma cell lines resistant to preactivated cyclophosphamide 
Current cancer drug targets  2008;8(3):172-179.
The total expression profiles of two medulloblastoma cell lines resistant to the preactivated form of cyclophosphamide (4-hydroperoxycyclophosphamide, 4-HC) were examined using the Affymetrix GeneChip U133A array. Our primary objective was to look for possible genes, other than the well-studied aldehyde dehydrogenases (ALDH) that may be involved in cyclophosphamide (CP) resistance in medulloblastomas. We present here the lists of the most highly upregulated [30 for D341 MED (4-HCR); 20 for D283 MED (4-HCR)] and downregulated [19 for D341 MED (4-HCR); 15 for D283 MED (4-HCR)] genes which may be involved in conferring CP-resistance to the two medullobalstoma cell lines. The lists of genes from the two sublines almost had no overlap, suggesting different mechanisms of CP-resistance. One of the most noteworthy upregulated gene is TAP1 [90-fold increase in D341 MED (4-HCR) relative to D341 MED]. TAP1, a protein belonging to the ABC transporter family is normally involved in major histocompatibility class I (MHC I) antigen processing. This suggests the possible role of multidrug resistance (MDR), albeit atypical (which means it does not involve the usual MDR1 and MRP glycoproteins), in medulloblastoma’s CP-resistance. Apart from TAP1, a number of other genes involved in MHC1 processing were upregulated in D341 MED (4HCR). D341 MED (4-HCR) also had a 20-fold increase in the expression of the aldo-keto reductase gene, AKR1B10, which may deactivate the reactive cyclophosphamide metabolite, aldophosphamide. For D283 MED (4-HCR), the most notable increase in expression is that of ALDH1B1, a member of the aldehyde dehydrogenase (ALDH) family of proteins.
PMCID: PMC3633091  PMID: 18473730
cyclophosphamide; drug resistance; medulloblastoma; brain tumor; oxazaphosphorine; aldehyde dehydrogenase; microarray; aldo-keto reductase
22.  Targeting Ras-RAF-ERK and its Interactive Pathways as a Novel Therapy for Malignant Gliomas 
Current cancer drug targets  2010;10(8):840-848.
Malignant gliomas are the most common and the deadliest brain malignancies in adults. Despite the lack of a complete understanding of the biology of these tumors, significant advances have been made in the past decades. One of the key discoveries made in the area of malignant gliomas is that these tumors can be induced and maintained by aberrant signaling networks. In this context, the Ras pathway has been extensively exploited, from both basic and translational perspectives. Although somatic oncogenic mutations of Ras genes are frequent in several cancer types, early investigations on gliomas revealed disappointing facts that the Ras mutations are nearly absent in malignant gliomas and that the BRAF mutations are present in a very small percentage of gliomas. Therefore, the observed deregulation of the Ras-RAF-ERK signaling pathway in gliomas is attributed to its upstream positive regulators, including, EGFR and PDGFR known to be highly active in the majority of malignant gliomas. In contrast to the initial negative results on the somatic mutations of H-Ras, K-Ras and BRAF, recent breakthrough studies on pediatric low-grade astrocytomas uncovered genetic alterations of the BRAF gene involving copy number gains and rearrangements. The 7q34 rearrangements result in a novel in-frame KIAA1549:BRAF fusion gene that possesses constitutive BRAF kinase activity resembling oncogenic BRAF (V600E). In light of the earlier findings and recent breakthroughs, this review summarizes our current understanding of the Ras-RAF-ERK signaling pathway in gliomas and the outcome of preclinical and clinical studies that evaluated the efficacy of Ras-targeted therapy in malignant gliomas.
PMCID: PMC3615246  PMID: 20718706
Akt; Avastin; BRAF; chemotherapy; EGFR; glioma; PDGFR; RAF; Ras
23.  Adding to the Mix: Fibroblast Growth Factor and Platelet-derived Growth Factor Receptor Pathways as Targets in Non–small Cell Lung Cancer 
Current cancer drug targets  2012;12(2):107-123.
The treatment of advanced non–small cell lung cancer (NSCLC) increasingly involves the use of molecularly targeted therapy with activity against either the tumor directly, or indirectly, through activity against host-derived mechanisms of tumor support such as angiogenesis. The most well studied signaling pathway associated with angiogenesis is the vascular endothelial growth factor (VEGF) pathway, and the only antiangiogenic agent currently approved for the treatment of NSCLC is bevacizumab, an antibody targeted against VEGF. More recently, preclinical data supporting the role of fibroblast growth factor receptor (FGFR) and platelet-derived growth factor receptor (PDGFR) signaling in angiogenesis have been reported. The platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF) pathways may also stimulate tumor growth directly through activation of downstream mitogenic signaling cascades. In addition, 1 or both of these pathways have been associated with resistance to agents targeting the epidermal growth factor receptor (EGFR) and VEGF. A number of agents that target FGF and/or PDGF signaling are now in development for the treatment of NSCLC. This review will summarize the potential molecular roles of PDGFR and FGFR in tumor growth and angiogenesis, as well as discuss the current clinical status of PDGFR and FGFR inhibitors in clinical development.
PMCID: PMC3418220  PMID: 22165970
angiogenesis; fibroblast growth factor (FGF); fibroblast growth factor receptor (FGFR); non–small cell lung cancer (NSCLC); platelet-derived growth factor (PDGF); platelet-derived growth factor receptor (PDGFR)
Current cancer drug targets  2011;11(4):451-464.
Patients with inflammatory bowel diseases, such as ulcerative colitis and Crohn's disease, are at increased risk of developing colon cancer, confirming that chronic inflammation predisposes to development of tumors. Moreover, it appears that colon cancers that do not develop as a complication of inflammatory bowel disease are also driven by inflammation, because it has been shown that regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) lowers the mortality from sporadic colon cancer and results in regression of adenomas in familial adenomatous polyposis (FAP) patients, who inherit a mutation in the Apc gene. Colorectal cancer therefore represents a paradigm for the link between inflammation and cancer.
Inflammation is driven by soluble factors, cytokines and chemokines, which can be produced by tumor cells themselves or, more often, by the cells recruited to the tumor microenvironment. Inflammatory cytokines and chemokines promote growth of tumor cells, perturb their differentiation, and support the survival of cancer cells.
Tumor cells become addicted to inflammatory stroma, suggesting that the tumor microenvironment represents an attractive target for preventive and therapeutic strategies. Proinflammatory cytokines, such as TNFα, IL-6 and IL-1β, or transcription factors that are required for signaling by these cytokines, including NF-κB and STATs, are indeed emerging as potential targets for anticancer therapy. TNFα antagonists are in phase I/II clinical trials and have been shown to be well tolerated in patients with solid tumors, and IL-1β antagonists that ameliorate several inflammatory disorders characterized by excessive IL-1β production, will likely follow. Therefore, development of drugs that normalize the tumor microenvironment or interrupt the crosstalk between the tumor and the tumor microenvironment is an important approach to the management of cancer.
PMCID: PMC3540985  PMID: 21247378
inflammation; colon cancer; TNF; IL1; NFκB; STAT; TRAIL
25.  Targeting EGFR for Treatment of Glioblastoma: Molecular Basis to Overcome Resistance 
Current cancer drug targets  2012;12(3):197-209.
Glioblastoma (glioblastoma multiforme; GBM; WHO Grade IV) accounts for the majority of primary malignant brain tumors in adults. Amplification and mutation of the epidermal growth factor receptor (EGFR) gene represent signature genetic abnormalities encountered in GBM. A range of potential therapies that target EGFR or its mutant constitutively active form, ΔEGFR, including tyrosine kinase inhibitors (TKIs), monoclonal antibodies, vaccines, and RNA-based agents, are currently in development or in clinical trials for the treatment of GBM. Data from experimental studies evaluating these therapies have been very promising; however, their efficacy in the clinic has so far been limited by both upfront and acquired drug resistance. This review discusses the current status of anti-EGFR agents and the recurrent problem of resistance to these agents that strongly indicates that a multiple target approach will provide a more favorable future for these types of targeted therapies in GBM.
PMCID: PMC3464093  PMID: 22268382
Epidermal growth factor receptor; EGFR-targeted therapy; Glioblastoma; therapeutic resistance

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