MERTK on mononuclear phagocytes regulates T cell antigen recognition at autoimmune and tumor sites

Understanding mechanisms of immune regulation is key to developing immunotherapies for autoimmunity and cancer. We examined the role of mononuclear phagocytes during peripheral T cell regulation in type 1 diabetes and melanoma. MERTK expression and activity in mononuclear phagocytes in the pancreatic islets promoted islet T cell regulation, resulting in reduced sensitivity of T cell scanning for cognate antigen in prediabetic islets. MERTK-dependent regulation led to reduced T cell activation and effector function at the disease site in islets and prevented rapid progression of type 1 diabetes. In human islets, MERTK-expressing cells were increased in remaining insulin-containing islets of type 1 diabetic patients, suggesting that MERTK protects islets from autoimmune destruction. MERTK also regulated T cell arrest in melanoma tumors. These data indicate that MERTK signaling in mononuclear phagocytes drives T cell regulation at inflammatory disease sites in peripheral tissues through a mechanism that reduces the sensitivity of scanning for antigen leading to reduced responsiveness to antigen.

Regulation of intercellular biomolecule transfer-driven tumor angiogenesis and responses to anticancer therapies

Intercellular biomolecule transfer (ICBT) between malignant and benign cells is a major driver of tumor growth, resistance to anticancer therapies, and therapy-triggered metastatic disease. Here we characterized cholesterol 25-hydroxylase (CH25H) as a key genetic suppressor of ICBT between malignant and endothelial cells (ECs) and of ICBT-driven angiopoietin-2-dependent activation of ECs, stimulation of intratumoral angiogenesis, and tumor growth. Human CH25H was downregulated in the ECs from patients with colorectal cancer and the low levels of stromal CH25H were associated with a poor disease outcome. Knockout of endothelial CH25H stimulated angiogenesis and tumor growth in mice. Pharmacologic inhibition of ICBT by reserpine compensated for CH25H loss, elicited angiostatic effects (alone or combined with sunitinib), augmented the therapeutic effect of radio-/chemotherapy, and prevented metastatic disease induced by these regimens. We propose inhibiting ICBT to improve the overall efficacy of anticancer therapies and limit their prometastatic side effects.

Hexokinase 2 in Cancer: A Prima Donna Playing Multiple Characters

Hexokinases are a family of ubiquitous exose-phosphorylating enzymes that prime glucose for intracellular utilization. Hexokinase 2 (HK2) is the most active isozyme of the family, mainly expressed in insulin-sensitive tissues. HK2 induction in most neoplastic cells contributes to their metabolic rewiring towards aerobic glycolysis, and its genetic ablation inhibits malignant growth in mouse models. HK2 can dock to mitochondria, where it performs additional functions in autophagy regulation and cell death inhibition that are independent of its enzymatic activity. The recent definition of HK2 localization to contact points between mitochondria and endoplasmic reticulum called Mitochondria Associated Membranes (MAMs) has unveiled a novel HK2 role in regulating intracellular Ca²⁺ fluxes. Here, we propose that HK2 localization in MAMs of tumor cells is key in sustaining neoplastic progression, as it acts as an intersection node between metabolic and survival pathways. Disrupting these functions by targeting HK2 subcellular localization can constitute a promising anti-tumor strategy.

Cannabinoid Quinones-A Review and Novel Observations

A cannabinoid anticancer para-quinone, HU-331, which was synthesized by our group five decades ago, was shown to have very high efficacy against human cancer cell lines in-vitro and against in-vivo grafts of human tumors in nude mice. The main mechanism was topoisomerase IIα catalytic inhibition. Later, several groups synthesized related compounds. In the present presentation, we review the publications on compounds synthesized on the basis of HU-331, summarize their published activities and mechanisms of action and report the synthesis and action of novel quinones, thus expanding the structure-activity relationship in these series.

Nanobiosensor Reports on CDK1 Kinase Activity in Tumor Xenografts in Mice

Probing the dynamics and quantifying the activities of intracellular protein kinases that coordinate cell growth and division and constitute biomarkers and pharmacological targets in hyperproliferative and pathological disorders remain a challenging task. Here engineering and characterization of a nanobiosensor of the mitotic kinase CDK1, through multifunctionalization of carbon nanotubes with a CDK1-specific fluorescent peptide reporter, are described. This original reporter of CDK1 activity combines the sensitivity of a fluorescent biosensor with the unique physico-chemical and biological properties of nanotubes for multifunctionalization and efficient intracellular penetration. The functional versatility of this nanobiosensor enables implementation to quantify CDK1 activity in a sensitive and dose-dependent fashion in complex biological environments in vitro, to monitor endogenous kinase in living cells and directly within tumor xenografts in mice by fluorescence imaging, thanks to a ratiometric quantification strategy accounting for response relative to concentration in space and in time.

The level of oncogenic Ras determines the malignant transformation of Lkb1 mutant tissue in vivo

The genetic and metabolic heterogeneity of RAS-driven cancers has confounded therapeutic strategies in the clinic. To address this, rapid and genetically tractable animal models are needed that recapitulate the heterogeneity of RAS-driven cancers in vivo. Here, we generate a Drosophila melanogaster model of Ras/Lkb1 mutant carcinoma. We show that low-level expression of oncogenic Ras (RasLow) promotes the survival of Lkb1 mutant tissue, but results in autonomous cell cycle arrest and non-autonomous overgrowth of wild-type tissue. In contrast, high-level expression of oncogenic Ras (RasHigh) transforms Lkb1 mutant tissue resulting in lethal malignant tumors. Using simultaneous multiview light-sheet microcopy, we have characterized invasion phenotypes of Ras/Lkb1 tumors in living larvae. Our molecular analysis reveals sustained activation of the AMPK pathway in malignant Ras/Lkb1 tumors, and demonstrate the genetic and pharmacologic dependence of these tumors on CaMK-activated Ampk. We further show that LKB1 mutant human lung adenocarcinoma patients with high levels of oncogenic KRAS exhibit worse overall survival and increased AMPK activation. Our results suggest that high levels of oncogenic KRAS is a driving event in the malignant transformation of LKB1 mutant tissue, and uncovers a vulnerability that may be used to target this aggressive genetic subset of RAS-driven tumors.

Decreases in different Dnmt3b activities drive distinct development of hematologic malignancies in mice

DNA methylation regulates gene transcription and is involved in various physiological processes in mammals, including development and hematopoiesis. It is catalyzed by DNA methyltransferases including Dnmt1, Dnmt3a, and Dnmt3b. For Dnmt3b, its effects on transcription can result from its own DNA methylase activity, the recruitment of other Dnmts to mediate methylation, or transcription repression in a methylation-independent manner. Low-frequency mutations in human DNMT3B are found in hematologic malignancies including cutaneous T-cell lymphomas, hairy cell leukemia, and diffuse large B-cell lymphomas. Moreover, Dnmt3b is a tumor suppressor in oncogene-driven lymphoid and myeloid malignancies in mice. However, it is poorly understood how the different Dnmt3b activities contribute to these outcomes. We modulated Dnmt3b activity in vivo by generating Dnmt3b+/- mice expressing one wild-type allele as well as Dnmt3b+/CI and Dnmt3bCI/CI mice where one or both alleles express catalytically inactive Dnmt3bCI. We show that 43% of Dnmt3b+/- mice developed T-cell lymphomas, chronic lymphocytic leukemia, and myeloproliferation over 18 months, thus resembling phenotypes previously observed in Dnmt3a+/- mice, possibly through regulation of shared target genes. Interestingly, Dnmt3b+/CI and Dnmt3bCI/CI mice survived postnatal development and were affected by B-cell rather than T-cell malignancies with decreased penetrance. Genome-wide hypomethylation, increased expression of oncogenes such as Jdp2, STAT1, and Trip13, and p53 downregulation were major events contributing to Dnmt3b+/- lymphoma development. We conclude that Dnmt3b catalytic activity is critical to prevent B-cell transformation in vivo, whereas accessory and methylation-independent repressive functions are important to prevent T-cell transformation.

PET imaging and pharmacological therapy targeting carbonic anhydrase-IX high-expressing tumors using US2 platform based on bivalent ureidosulfonamide

Carbonic anhydrase-IX (CA-IX) is attracting much attention as a target molecule for cancer treatment since high expression of CA-IX can lead to a poor prognosis of patients. We previously reported low-molecular-weight ¹¹¹In/⁹⁰Y complexes with a bivalent ureidosulfonamide scaffold ([¹¹¹In/⁹⁰Y]In/Y-US2) as cancer radiotheranostic agents for single photon emission computed tomography and radionuclide-based therapy targeting CA-IX. Here, we applied the US2 platform to positron emission tomography (PET) imaging and pharmacological therapy targeting CA-IX high-expressing tumors by introducing ⁶⁸Ga and ^natIn, respectively. In an in vitro cell binding assay, [⁶⁷Ga]Ga-US2, an alternative complex of [⁶⁸Ga]Ga-US2 with a longer half-life, markedly bound to CA-IX high-expressing (HT-29) cells compared with low-expressing (MDA-MB-231) cells. In a biodistribution study with HT-29 and MDA-MB-231 tumor-bearing mice, [⁶⁷Ga]Ga-US2 showed accumulation in the HT-29 tumor (3.81% injected dose/g at 60 min postinjection) and clearance from the blood pool with time. PET with [⁶⁸Ga]Ga-US2 clearly visualized the HT-29 tumor in model mice at 60 min postinjection. In addition, the administration of [^natIn]In-US2 to HT-29 tumor-bearing mice led to tumor growth delay and prolonged mouse survival, while no critical toxicity was observed. These results indicate that [⁶⁸Ga]Ga-US2 and [^natIn]In-US2 may be useful imaging and therapeutic agents targeting CA-IX, respectively, and that US2 may serve as an effective cancer theranostic platform utilizing CA-IX.

Enzyme-instructed self-aggregation of Fe3O4 nanoparticles for enhanced MRI T2 imaging and photothermal therapy of tumors

The aggregation of superparamagnetic iron oxide (SPIO) nanoparticles (NPs) can greatly enhance magnetic resonance imaging (MRI) T2-weighted imaging and near-infrared (NIR) absorption in experiments. In this study, an Ac-Arg-Val-Arg-Arg-Cys(StBu)-Lys-CBT probe was designed and coupled with monodispersed carboxyl-decorated SPIO NPs to form SPIO@1NPs, which use it for intracellular self-aggregation. In vitro experiments showed that the self-aggregation of SPIO@1NPs was induced by a condensation reaction mediated by the enzyme furin in furin-overexpressing tumor cells. Moreover, the NPs in the aggregated state showed significantly higher MR r2 values and photothermal conversion efficiency than the NPs in the monodisperse state. Then, the in vivo SPIO@1NP self-aggregation in tumors can facilitate accurate MRI T2 imaging-guided photothermal therapy for effectively killing cancer cells. We believe that this basic technique, based on tumor-specific enzyme-instructed intracellular self-aggregation of NPs, could be useful for the rational synthesis of other inorganic NPs for use in the fields of tumor diagnosis and treatment.

An Activating Mutation in ERK Causes Hyperplastic Tumors in a scribble Mutant Tissue in Drosophila

Receptor tyrosine kinase signaling plays prominent roles in tumorigenesis, and activating oncogenic point mutations in the core pathway components Ras, Raf, or MEK are prevalent in many types of cancer. Intriguingly, however, analogous oncogenic mutations in the downstream effector kinase ERK have not been described or validated in vivo To determine if a point mutation could render ERK intrinsically active and oncogenic, we have assayed in Drosophila the effects of a mutation that confers constitutive activity upon a yeast ERK ortholog and has also been identified in a few human tumors. Our analyses indicate that a fly ERK ortholog harboring this mutation alone (RolledR80S), and more so in conjunction with the known sevenmaker mutation (RolledR80S+D334N), suppresses multiple phenotypes caused by loss of Ras-Raf-MEK pathway activity, consistent with an intrinsic activity that is independent of upstream signaling. Moreover, expression of RolledR80S and RolledR80S+D334N induces tissue overgrowth in an established Drosophila cancer model. Our findings thus demonstrate that activating mutations can bestow ERK with pro-proliferative, tumorigenic capabilities and suggest that Drosophila represents an effective experimental system for determining the oncogenicity of ERK mutants and their response to therapy.

Matrix metallopeptidase 2 targeted delivery of gold nanostars decorated with IR-780 iodide for dual-modal imaging and enhanced photothermal/photodynamic therapy

Nanotheranostics has gained increasing interest, as it offers a great potential to realize personalized diagnostics and therapy. In this work, we report a facile approach of the fabrication of gold nanostars (GNS) attached with matrix metalloproteinases (MMP2) polypeptides (Ac-GPLGIAGQ) and IR-780 iodide through bovine serum albumin (BSA) for targeted dual-modal photoacoustic (PA)/near-infrared (NIR) fluorescence imaging and enhanced photothermal therapy (PTT)/photodynamic therapy (PDT) for lung cancer. MMP2 polypeptides served as the targeting ligand, IR-780 iodide functioned as the NIR fluorescence imaging agent as well as PTT/PDT agent, and GNS acted as the carrier of IR-780 molecules and performed PA imaging and PTT. DLS and CCK-8 assay demonstrated that the nanoprobes (GNS@BSA/I-MMP2) exhibited excellent stability and biocompatibility under physiological conditions. Subsequent in vitro studies verified that GNS@BSA/I-MMP2 nanoparticles (NPs) were effectively internalized by A549 cancer cells and exhibited remarkable antitumor efficacy. Furthermore, GNS@BSA/I-MMP2 NPs could specifically target the tumor and significantly suppress the tumor growth, and their antitumor effects were mainly through the synergistic effects of PDT and PTT based on IR-780 and GNS. These findings imply the potential of GNS@BSA/I-MMP2 NPs as a targeting PA/NIR probe in tumor diagnosis and combined therapy with a single light source. STATEMENT OF SIGNIFICANCE: We reported a convenient and facile approach to load IR-780 iodides in gold nanostars (GNS). This material could simultaneously perform near-infrared imaging/photoacoustic imaging and thermotherapy/photodynamic therapy. MMP2 coating on the surface of GNS@BSA/IR-780 promoted the prepared nanoparticles (GNS@BSA/I-MMP2) to target the tumor region. The heat generated by the synergistic effect of the GNS and IR-780 molecules resulted in the high temperature of the GNS@BSA/I-MMP2 NPs, which efficiently suppressed the growth of tumor, and the tumor volume decreased by 93% compared with that in the PBS groups with laser irradiation.

Omega-3 Fatty Acids Prevent Early Pancreatic Carcinogenesis via Repression of the AKT Pathway

Pancreatic cancer remains a daunting foe despite a vast number of accumulating molecular analyses regarding the mutation and expression status of a variety of genes. Indeed, most pancreatic cancer cases uniformly present with a mutation in the KRAS allele leading to enhanced RAS activation. Yet our understanding of the many epigenetic/environmental factors contributing to disease incidence and progression is waning. Epidemiologic data suggest that diet may be a key factor in pancreatic cancer development and potentially a means of chemoprevention at earlier stages. While diets high in ω3 fatty acids are typically associated with tumor suppression, diets high in ω6 fatty acids have been linked to increased tumor development. Thus, to better understand the contribution of these polyunsaturated fatty acids to pancreatic carcinogenesis, we modeled early stage disease by targeting mutant KRAS to the exocrine pancreas and administered diets rich in these fatty acids to assess tumor formation and altered cell-signaling pathways. We discovered that, consistent with previous reports, the ω3-enriched diet led to reduced lesion penetrance via repression of proliferation associated with reduced phosphorylated AKT (pAKT), whereas the ω6-enriched diet accelerated tumor formation. These data provide a plausible mechanism underlying previously observed effects of fatty acids and suggest that administration of ω3 fatty acids can reduce the pro-survival, pro-growth functions of pAKT. Indeed, counseling subjects at risk to increase their intake of foods containing higher amounts of ω3 fatty acids could aid in the prevention of pancreatic cancer.

Polymerase-mediated ultramutagenesis in mice produces diverse cancers with high mutational load

Mutations underlie all cancers, and their identification and study are the foundation of cancer biology. We describe what we believe to be a novel approach to mutagenesis and cancer studies based on the DNA polymerase ε (POLE) ultramutator phenotype recently described in human cancers, in which a single amino acid substitution (most commonly P286R) in the proofreading domain results in error-prone DNA replication. We engineered a conditional PoleP286R allele in mice. PoleP286R/+ embryonic fibroblasts exhibited a striking mutator phenotype and immortalized more efficiently. PoleP286R/+ mice were born at Mendelian ratios but rapidly developed lethal cancers of diverse lineages, yielding the most cancer-prone monoallelic model described to date, to our knowledge. Comprehensive whole-genome sequencing analyses showed that the cancers were driven by high base substitution rates in the range of human cancers, overcoming a major limitation of previous murine cancer models. These data establish polymerase-mediated ultramutagenesis as an efficient in vivo approach for the generation of diverse animal cancer models that recapitulate the high mutational loads inherent to human cancers.

IDH1-mutated transgenic zebrafish lines: An in-vivo model for drug screening and functional analysis

Introduction

The gene encoding isocitrate dehydrogenase 1 (IDH1) is frequently mutated in several tumor types including gliomas. The most prevalent mutation in gliomas is a missense mutation leading to a substitution of arginine with histidine at the residue 132 (R132H). Wild type IDH1 catalyzes oxidative decarboxylation of isocitrate to α-ketoglutarate (α-KG) whereas mutant IDH1 converts α-KG into D2-hydroxyglutarate (D2HG). Unfortunately, there are few in vivo model systems for IDH-mutated tumors to study the effects of IDH1 mutations in tumor development. We have therefore created transgenic zebrafish lines that express various IDH1 mutants.

Materials and methods

IDH1 mutations (IDH1^R132H, IDH1^R132C and loss-of-function mutation IDH1^G70D), IDH1^wildtype or eGFP were cloned into constructs with several brain-specific promoters (Nestin, Gfap or Gata2). These constructs were injected into fertilized zebrafish eggs at the one-cell stage.

Results

In total more than ten transgenic zebrafish lines expressing various brain-specific IDH1 mutations were created. A significant increase in the level of D2HG was observed in all transgenic lines expressing IDH1^R132C or IDH1^R132H, but not in any of the lines expressing IDH1^wildtype, IDH1^G70D or eGFP. No differences in 5-hydroxymethyl cytosine and mature collagen IV levels were observed between wildtype and mutant IDH1 transgenic fish. To our surprise, we failed to identify any strong phenotype, despite increased levels of the oncometabolite D2HG. No tumors were observed, even when backcrossing with tp53-mutant fish which suggests that additional transforming events are required for tumor formation. Elevated D2HG levels could be lowered by treatment of the transgenic zebrafish with an inhibitor of mutant IDH1 activity.

Conclusions

We have generated a transgenic zebrafish model system for mutations in IDH1 that can be used for functional analysis and drug screening. Our model systems help understand the biology of IDH1 mutations and its role in tumor formation.

Methodologic Problems Encountered in the Assay of Proteinases in Lewis Lung Carcinoma, a Mouse Metastasizing Tumor

The proteolytic activity in homogenates and extracts of subcellular fractions prepared from subcutaneous Lewis lung carcinoma was determined using proteins and synthetic peptides as substrates. The presence of cathepsin D, plasminogen activator, cathepsin B-, cathepsin G-and elastase-like enzymes was observed. No difference was revealed between the proteolytic activity in homogenates of Lewis lung carcinoma, at the growth stage examined, and in homogenates of normal lung. High specific activities were found in the lysosomal extract, whereas decreasing activities were found in the nuclear extract, the homogenate and the post-lysosomal mitochondrial supernatant; no active or trypsin-activatable collagenase activity was detected. The presence in the tumor tissue of these enzymatic activities is in agreement with their proposed role in the process of metastasis. The lack of differences between homogenates of tumor and normal lung tissue suggests that the use of whole cells is required to selectively study tumor proteinases specifically involved in tumor malignancy.

3'-Deoxy-3'-[18F]Fluorothymidine Uptake Is Related to Thymidine Phosphorylase Expression in Various Experimental Tumor Models

PURPOSE

We recently reported that high thymidine phosphorylase (TP) expression is accompanied by low tumor thymidine concentration and high 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT) uptake in four untreated lung cancer xenografts. Here, we investigated whether this relationship also holds true for a broader range of tumor models.

PROCEDURES

Lysates from n = 15 different tumor models originating from n = 6 institutions were tested for TP and thymidylate synthase (TS) expression using western blots. Results were correlated to [18F]FLT accumulation in the tumors as determined by positron emission tomography (PET) measurements in the different institutions and to previously published thymidine concentrations.

RESULTS

Expression of TP correlated positively with [18F]FLT SUVmax (ρ = 0.549, P < 0.05). Furthermore, tumors with high TP levels possessed lower levels of thymidine (ρ = - 0.939, P < 0.001).

CONCLUSIONS

In a broad range of tumors, [18F]FLT uptake as measured by PET is substantially influenced by TP expression and tumor thymidine concentrations. These data strengthen the role of TP as factor confounding [18F]FLT uptake.

Methionine sulfoxide reductase B1 regulates proliferation and invasion by affecting mitogen-activated protein kinase pathway and epithelial-mesenchymal transition in u2os cells

Methionine sulfoxide reductase B1 (MsrB1), a member of the selenoprotein family and contributes significantly to the reduction of methionine sulfoxides produced from reactive oxygen species (ROS). However, few studies have examined the role of MsrB1 in tumors. Here We tested the proliferation and invasion in MsrB1 knockdown u2os cells under H₂O₂/thioredoxin. As shown in our result, knockdown of MsrB1 inhibited the proliferation of u2os cells and regulates mitogen-activated protein kinase (MAPK) pathway by down-regulation of Erk, MeK phosphorylation and p53 expression in u2os cells. In a xenograft tumorigenicity mice, MsrB1 knockdown effectively inhibited tumor growth. Furthermore, MsrB1 knockdown resulted in migration and invasion reducement of u2os cells. MsrB1 regulates epithelial-mesenchymal transition (EMT) via affecting cytoskeleton by increasing E-cadherin expression and decreasing N-cadherin, TGF-β1, slug, fibronectin, vimentin, c-myc, snail and β-catenin expressions. In vivo, MsrB1 shRNAi can inhibit lung metastasis in metastasis model. In conclusion, MsrB1 regulates proliferation and invasion of u2os cells by affecting MAPK pathway and EMT, and MsrB1 gene may be a novel therapeutic target against tumors.

The tumor suppressor phosphatase PP2A-B56α regulates stemness and promotes the initiation of malignancies in a novel murine model

Protein phosphatase 2A (PP2A) is a ubiquitously expressed Serine-Threonine phosphatase mediating 30–50% of protein phosphatase activity. PP2A functions as a heterotrimeric complex, with the B subunits directing target specificity to regulate the activity of many key pathways that control cellular phenotypes. PP2A-B56α has been shown to play a tumor suppressor role and to negatively control c-MYC stability and activity. Loss of B56α promotes cellular transformation, likely at least in part through its regulation of c-MYC. Here we report generation of a B56α hypomorph mouse with very low B56α expression that we used to study the physiologic activity of the PP2A-B56α phosphatase. The predominant phenotype we observed in mice with B56α deficiency in the whole body was spontaneous skin lesion formation with hyperproliferation of the epidermis, hair follicles and sebaceous glands. Increased levels of c-MYC phosphorylation on Serine62 and c-MYC activity were observed in the skin lesions of the B56α^hm/hm mice. B56α deficiency was found to increase the number of skin stem cells, and consistent with this, papilloma initiation was accelerated in a carcinogenesis model. Further analysis of additional tissues revealed increased inflammation in spleen, liver, lung, and intestinal lymph nodes as well as in the skin lesions, resembling elevated extramedullary hematopoiesis phenotypes in the B56α^hm/hm mice. We also observed an increase in the clonogenicity of bone marrow stem cells in B56α^hm/hm mice. Overall, this model suggests that B56α is important for stem cells to maintain homeostasis and that B56α loss leading to increased activity of important oncogenes, including c-MYC, can result in aberrant cell growth and increased stem cells that can contribute to the initiation of malignancy.

Isoform-Specific Effects of Wild-Type Ras Genes on Carcinogen-Induced Lung Tumorigenesis in Mice

The gene KRAS is commonly mutated in lung cancer to encode a constitutively active and oncogenic protein that is well established to initiate and maintain lung tumorigenesis. However, the remaining wild-type KRAS protein, or the other family members HRAS and NRAS, can still be activated in the presence of oncogenic KRAS. Moreover, loss of any one of these three genes has been shown to increase the sensitivity of mice to the carcinogen urethane, which induces Kras mutation-positive early lung lesions. To determine the contribution of progressively disrupting Hras and Nras genes on urethane lung tumorigenesis, mice with different combinations of wild-type and null alleles of Hras and Nras were exposed with urethane and tumor burden was assessed. As previously reported, loss of one allele of Hras increased the sensitivity of mice to this carcinogen, and this effect was further exacerbated by the loss of the second Hras allele. However, loss of one or both alleles of Nras failed to alter tumor burden, either in the absence or presence of Hras, after exposure to urethane. Additionally, no obvious difference between lung lesions in mice with wild-type versus null alleles was detected, suggesting that wild-type Ras proteins may exert a tumor suppressive effects at the time of initiation, although other interpretations are certainly possible. In summary, these data suggest that in some genetic backgrounds inactivation of different wild-type Ras genes can have different effects on urethane-induced lung tumorigenesis.

Involvement of activation-induced cytidine deaminase in skin cancer development

Most skin cancers develop as the result of UV light-induced DNA damage; however, a substantial number of cases appear to occur independently of UV damage. A causal link between UV-independent skin cancers and chronic inflammation has been suspected, although the precise mechanism underlying this association is unclear. Here, we have proposed that activation-induced cytidine deaminase (AID, encoded by AICDA) links chronic inflammation and skin cancer. We demonstrated that Tg mice expressing AID in the skin spontaneously developed skin squamous cell carcinoma with Hras and Trp53 mutations. Furthermore, genetic deletion of Aicda reduced tumor incidence in a murine model of chemical-induced skin carcinogenesis. AID was expressed in human primary keratinocytes in an inflammatory stimulus-dependent manner and was detectable in human skin cancers. Together, the results of this study indicate that inflammation-induced AID expression promotes skin cancer development independently of UV damage and suggest AID as a potential target for skin cancer therapeutics.

Enzyme responsive drug delivery system based on mesoporous silica nanoparticles for tumor therapy in vivo

To reduce the toxic side effects of traditional chemotherapeutics in vivo, we designed and constructed a biocompatible, matrix metalloproteinases (MMPs) responsive drug delivery system based on mesoporous silica nanoparticles (MSNs). MMPs substrate peptide containing PLGLAR (sensitive to MMPs) was immobilized onto the surfaces of amino-functionalized MSNs via an amidation reaction, serving as MMPs sensitive intermediate linker. Bovine serum albumin was then covalently coupled to linker as end-cap for sealing the mesopores of MSNs. Lactobionic acid was further conjugated to the system as targeting motif. Doxorubicin hydrochloride was used as the model anticancer drug in this study. A series of characterizations revealed that the system was successfully constructed. The peptide-functionalized MSNs system demonstrated relatively high sensitivity to MMPs for triggering drug delivery, which was potentially important for tumor therapy since the tumor's microenvironment overexpressed MMPs in nature. The in vivo experiments proved that the system could efficiently inhibit the tumor growth with minimal side effects. This study provides an approach for the development of the next generation of nanotherapeutics toward efficient cancer treatment.

Inhibition of induced nitric oxide synthase enhances the anti-tumor effects on cancer immunotherapy using TLR7 agonist in mice

Toll-like receptor (TLR) agonists have been shown to have anti-tumor activity in basic research and clinical studies. However, TLR agonist monotherapy in cancer treatment dose not sufficiently eliminate tumors. Activation of the innate immune response by TLR agonists and other pathogen-associated molecular patterns is effective for driving adaptive immunity via interleukin (IL)-12 or IL-1, but is counteracted by the simultaneous induction of immunosuppressive cytokines and other molecules, including IL-10, tumor growth factor-β, and induced nitric oxide synthase (iNOS). In the present study, we evaluated the anticancer effect of the TLR7 agonist, imiquimod (IMQ), in the absence of iNOS. The administration of IMQ in iNOS-knockout (KO) mice implanted with tumor cells significantly suppressed tumor progression as compared to that in wild-type mice and improved the survival rate. Moreover, injection with IMQ enhanced the tumor antigen-specific Th1 response in iNOS-KO mice with tumors. The enhancement of the antigen-specific Th1 response was associated with an increase in IL-2 and IL-12b expressions in the tumor-draining lymph nodes. Combination therapy with IMQ and an iNOS inhibitor also significantly inhibited tumor growth in the established tumor model. Finally, our results indicated that the enhancement of iNOS expression through the administration with TLR agonists impairs host anti-tumor immunity, while the inhibition of iNOS could enhance the therapeutic efficacy of TLR agonists via the increase in Th1 immune response.

SD-208, a novel protein kinase D inhibitor, blocks prostate cancer cell proliferation and tumor growth in vivo by inducing G2/M cell cycle arrest

Protein kinase D (PKD) has been implicated in many aspects of tumorigenesis and progression, and is an emerging molecular target for the development of anticancer therapy. Despite recent advancement in the development of potent and selective PKD small molecule inhibitors, the availability of in vivo active PKD inhibitors remains sparse. In this study, we describe the discovery of a novel PKD small molecule inhibitor, SD-208, from a targeted kinase inhibitor library screen, and the synthesis of a series of analogs to probe the structure-activity relationship (SAR) vs. PKD1. SD-208 displayed a narrow SAR profile, was an ATP-competitive pan-PKD inhibitor with low nanomolar potency and was cell active. Targeted inhibition of PKD by SD-208 resulted in potent inhibition of cell proliferation, an effect that could be reversed by overexpressed PKD1 or PKD3. SD-208 also blocked prostate cancer cell survival and invasion, and arrested cells in the G2/M phase of the cell cycle. Mechanistically, SD-208-induced G2/M arrest was accompanied by an increase in levels of p21 in DU145 and PC3 cells as well as elevated phosphorylation of Cdc2 and Cdc25C in DU145 cells. Most importantly, SD-208 given orally for 24 days significantly abrogated the growth of PC3 subcutaneous tumor xenografts in nude mice, which was accompanied by reduced proliferation and increased apoptosis and decreased expression of PKD biomarkers including survivin and Bcl-xL. Our study has identified SD-208 as a novel efficacious PKD small molecule inhibitor, demonstrating the therapeutic potential of targeted inhibition of PKD for prostate cancer treatment.

Synthesis and evaluation of (18)F-labeled tertiary benzenesulfonamides for imaging carbonic anhydrase IX expression in tumours with positron emission tomography

Three tertiary benzenesulfonamide inhibitors 4a-c were radiolabeled with (18)F and evaluated for imaging carbonic anhydrase IX (CA IX) expression with positron emission tomography. All three inhibitors exhibit <10 nM affinity for CA IX with no measurable affinity for CA II. Despite good affinity/selectivity to CA IX and excellent stability in plasma, uptake of [(18)F]4a-c in CA IX-expressing HT-29 tumours was low without significant contrast. [(18)F]4a,b were excreted rapidly, while [(18)F]4c exhibited significant in vivo defluorination leading to high bone uptake. Due to minimal uptake in HT-29 tumours compared to normal organs/tissues, (18)F-labeled benzenesulfonamides [(18)F]4a-c are not suitable as CA IX imaging agents.

[Functional activity of NADH-dependent reductase system in the liver microsomal fraction and Guerin's carcinoma in rats exposed to preliminary irradiation]

The activity of liver and Guerin's carcinoma microsomal NADH-dependent reductase system has been investigated in tumor-bearing rats exposed to preliminary irradiation. Preliminary irradiation of rats (before transplantation of Guerin's carcinoma) resulted in the decrease of NADH-cytochrome b5 reductase activity and contents of cytochrome b5 in the Guerin's carcinoma microsomal fraction in the logarithmic phases of oncogenesis compared with the non-irradiated tumor-bearing rats. The effect of irradiation preceding transplantation of the tumor to rats results in the increase of enzymatic activities of liver microsomal NADH-cytochrome b5 reductase in the latent and logarithmic phases of tumor growth as compared with non-irradiated tumor-bearing rats. At the same time the contents of cytochrome b5 decreases. During longer periods after irradiation the investigated parameters approached to those in the group of non-irradiated tumor-bearing animals.

Vascular RhoJ is an effective and selective target for tumor angiogenesis and vascular disruption

Current antiangiogenic therapy is limited by its cytostatic nature and systemic side effects. To address these limitations, we have unveiled the role of RhoJ, an endothelial-enriched Rho GTPase, during tumor progression. RhoJ blockade provides a double assault on tumor vessels by both inhibiting tumor angiogenesis and disrupting the preformed tumor vessels through the activation of the RhoA-ROCK (Rho kinase) signaling pathway in tumor endothelial cells, consequently resulting in a functional failure of tumor vasculatures. Moreover, enhanced anticancer effects were observed when RhoJ blockade was employed in concert with a cytotoxic chemotherapeutic agent, angiogenesis-inhibiting agent, or vascular-disrupting agent. These results identify RhoJ blockade as a selective and effective therapeutic strategy for targeting tumor vasculature with minimal side effects.

Muscle mTORC1 suppression by IL-6 during cancer cachexia: a role for AMPK

Although catabolic signaling has a well-established role in muscle wasting during cancer cachexia, the suppression of anabolic signaling also warrants further investigation. In cachectic tumor-bearing mice, circulating IL-6 levels are associated with suppressed muscle protein synthesis and mTORC1 signaling. We have found AMPK and IGF-I/insulin signaling, two well-known regulators of the mammalian target of rapamycin (mTOR), are altered with the progression of cachexia. How IL-6 can induce suppression of mTORC1 signaling remains to be established. The purpose of this study was to examine mTOR complex 1 (mTORC1) activation and regulation by IL-6 during cancer cachexia. IL-6 effects on mTOR activation were examined in Apc(Min/+) mouse skeletal muscle and C2C12 myotubes. Systemic IL-6 overexpression in Apc(Min/+) mice produced a dose-dependent suppression of mTOR signaling that corresponded to induction of STAT3 and AMPK phosphorylation. This result was also evident in IL-6-treated myotubes. Basal mTOR activation and mTOR responsiveness to glucose administration were suppressed in cachectic skeletal muscle. However, insulin induction of mTOR activity was maintained in IL-6-treated myotubes. Whereas IL-6 suppression of myotube mTOR activity was rescued by AMPK inhibition, inhibition of STAT3 signaling was not sufficient to rescue IL-6 suppression of mTOR activity. Last, treadmill exercise training was able to prevent IL-6-induced inhibition of mTOR signaling in Apc(Min/+) mice independently of activated STAT. In conclusion, we report dose-dependent suppression of mTOR activity by IL-6 and suppressed mTOR responsiveness to glucose administration in Apc(Min/+) mice. IL-6 suppression of mTOR activity was dependent on AMPK activation and independent of STAT signaling in myotubes.

SIRT4 has tumor-suppressive activity and regulates the cellular metabolic response to DNA damage by inhibiting mitochondrial glutamine metabolism

DNA damage elicits a cellular signaling response that initiates cell cycle arrest and DNA repair. Here, we find that DNA damage triggers a critical block in glutamine metabolism, which is required for proper DNA damage responses. This block requires the mitochondrial SIRT4, which is induced by numerous genotoxic agents and represses the metabolism of glutamine into tricarboxylic acid cycle. SIRT4 loss leads to both increased glutamine-dependent proliferation and stress-induced genomic instability, resulting in tumorigenic phenotypes. Moreover, SIRT4 knockout mice spontaneously develop lung tumors. Our data uncover SIRT4 as an important component of the DNA damage response pathway that orchestrates a metabolic block in glutamine metabolism, cell cycle arrest, and tumor suppression.

The Polo-Like Kinase 1 (PLK1) inhibitor NMS-P937 is effective in a new model of disseminated primary CD56+ acute monoblastic leukaemia

CD56 is expressed in 15-20% of acute myeloid leukaemias (AML) and is associated with extramedullary diffusion, multidrug resistance and poor prognosis. We describe the establishment and characterisation of a novel disseminated model of AML (AML-NS8), generated by injection into mice of leukaemic blasts freshly isolated from a patient with an aggressive CD56(+) monoblastic AML (M5a). The model reproduced typical manifestations of this leukaemia, including presence of extramedullary masses and central nervous system involvement, and the original phenotype, karyotype and genotype of leukaemic cells were retained in vivo. Recently Polo-Like Kinase 1 (PLK1) has emerged as a new candidate drug target in AML. We therefore tested our PLK1 inhibitor NMS-P937 in this model either in the engraftment or in the established disease settings. Both schedules showed good efficacy compared to standard therapies, with a significant increase in median survival time (MST) expecially in the established disease setting (MST = 28, 36, 62 days for vehicle, cytarabine and NMS-P937, respectively). Importantly, we could also demonstrate that NMS-P937 induced specific biomarker modulation in extramedullary tissues. This new in vivo model of CD56(+) AML that recapitulates the human tumour lends support for the therapeutic use of PLK1 inhibitors in AML.

[The change in the structural and functional organization of the Guerin's carcinoma cytochrome part of respiratory chain in tumor carriers in the conditions of preliminary low-level irradiation]

The effect of low-level irradiation of tumor-bearing rats on the structural and functional organization of the cytochrome part of respiratory chain of mitochondria isolated from Guerin's carcinoma has been investigated. The maximal reduction in the mitochondrial cytochromes a, b and c content was observed at the terminal stage of Guerin's carcinoma. A low-level irradiation during initial stages of oncogenesis produced opposite changes in the mitochondrial cytochrome content. The possible mechanism of mitochondrial haem-containing cytochromes content reduction may be attributed to impairment in their formation caused by inhibition of the key enzyme of haem synthesis, 5-aminolevulinate synthase. The determined changes of the mitochondrial cytochromes quantitative content were accompanied by decreased activity of cytochrome oxidase. The preliminary low-level irradiation of the tumor-bearing animals produced further reduction in the cytochrome oxidase activity observed in all experimental periods.

[The induction of Guerin's carcinoma cytochrome p450 hydroxylase activity by retinoids]

The interconnection of tumor growth process and the provision of the body with vitamin A was studied. The replenishment of vitamin A stores of vitamin-deficient tumor bearing animals modulated Guerin's carcinoma growth rate in a dose dependent manner (r = 0,83). The morphological parameters of tumor growth at different provision with vitamin A positively correlated with hydroxylase (r = 0,81) and demethylase (r = 0,49) activities of the Guerin's carcinoma cytochrome P450 system. The induction of hydroxylase and demethylase activities of cytochrome P450 in Guerin's carcinoma microsomal fraction, observed either under conditions of overdose supplementation, or selective liposomal form of all-trans-retinoic acid, suggests the stimulatory effect of retinoids on tumor growth.

Inhibition of cyclooxygenase-2 enhances immunotherapy against experimental brain tumors

Glioblastoma multiforme is the most common and aggressive malignant brain tumor in humans, and the prognosis is very poor despite conventional therapy. Immunotherapy represents a novel treatment approach, but the effect is often weakened by release of immune-suppressive molecules such as prostaglandins. In the current study, we investigated the effect of immunotherapy with irradiated interferon-γ (IFN-γ)-secreting tumor cells and administration of the selective cyclooxygenase-2 (COX-2) inhibitor parecoxib as treatment of established rat brain tumors. COX-2 inhibition and immunotherapy significantly enhanced the long-term cure rate (81% survival) compared with immunotherapy alone (19% survival), and there was a significant increase in plasma IFN-γ levels in animals treated with the combined therapy, suggesting a systemic T helper 1 immune response. COX-2 inhibition alone, however, did neither induce cure nor prolonged survival. The tumor cells were identified as the major source of COX-2 both in vivo and in vitro, and unmodified tumor cells produced prostaglandin E(2) in vitro, while the IFN-γ expressing tumor cells secreted significantly lower levels. In conclusion, we show that immunotherapy of experimental brain tumors is greatly potentiated when combined with COX-2 inhibition. Based on our results, the clinically available drug parecoxib may be added to immunotherapy against human brain tumors. Furthermore, the discovery that IFN-γ plasma levels can be used to determine the ongoing in vivo immune response has translational potential.

Quantitative determination of decursin, decursinol angelate, and decursinol in mouse plasma and tumor tissue using liquid-liquid extraction and HPLC

The pyranocoumarin compound decursin and its isomer decursinol angelate (DA) are the major hydrophobic phytochemicals in the root of Angelica gigas Nakai (AGN, Korean Angelica), a major traditional medicinal herb. The ethanol extract of AGN and especially the purified decursin and DA have been shown to exhibit antitumor activities by our collaborative team and others. Although decursinol has been identified as a major hydrolysis metabolite of decursin and DA in vivo in previous pharmacokinetic studies with mouse and rat, other recently published results sharply disputed this conclusion. In this study, we set up a practical method for the concurrent analysis of decursin, DA, and decursinol in mouse plasma and tumor tissues by liquid-liquid extraction and HPLC-UV and applied the method to several animal experiments. Plasma or tumor homogenate was extracted directly with ethyl acetate. The extraction efficiency for decursin/DA (quantitated together) and decursinol was between 82-95 % in both mouse plasma and tumor homogenate. The lower limit of quantitation (LLOQ) was approximately 0.25 µg/mL for decursin/DA and 0.2 µg/mL for decursinol in mouse plasma. In a pilot pharmacokinetic study, male C57BL/6 mice were given a single dose of 4.8 mg decursin/DA mixture (~240 mg/kg) per mouse either by oral gavage or intraperitoneal injection. Maximum plasma concentrations for decursin/DA and decursinol were 11.2 and 79.7 µg/mL, respectively, when decursin/DA was administered via intraperitoneal injection, and 0.54 and 14.9 µg/mL via oral gavage. Decursin/DA and decursinol contents in the tumor tissues from nude mouse xenografts correlated very well with those in plasma. Overall, our results confirm the conclusion that the majority of decursin/DA hydrolyze to decursinol in rodent models with a tiny fraction remaining as the intact compounds administered.

Chemomodulatory potential of Glycine max against murine skin and cervical papillomagenesis

In the present study, chemopreventive potential of Glycine max (G. Max) seeds was examined against DMBA-induced skin and MCA-induced cervical papillomagenesis in Swiss albino mice. Different doses (2.5, 5, and 7.5% w/w) of G. max were provided to animals in feed. Results exhibited a significant reduction in skin as well as cervical tumor incidence and tumor multiplicity (up to 75%) at all doses of test diet as compared to the control. Relatively, 7.5% test diet was most effective in protecting the animals against carcinogenesis. Further, detoxifying enzymes and antioxidative status was also evaluated in the liver of mice to understand the role of G. max in prevention of cancer. It was observed that the test diet containing G. max significantly elevated the specific activities of glutathione-S-transferase (GST), DT-diaphorase (DTD), superoxide dismutase (SOD), catalase (CAT), and glyoxalase I (Gly I). The test diet also elevated the content of reduced glutathione whereas it decreased the level of the peroxidative damage along with the specific activity of lactate dehydrogenase. It appeared that G. max seeds provided chemoprevention against skin and cervical papillomagenesis probably by modulating the detoxifying and antioxidative enzymes. It could be inferred that intake of G. max might help in reducing the risk of cancer.

ADP-ribosylarginine hydrolase regulates cell proliferation and tumorigenesis

Protein ADP-ribosylation is a reversible posttranslational modification of uncertain significance in cancer. In this study, we evaluated the consequences for cancer susceptibility in the mouse of a genetic deletion of the enzyme responsible for removing mono-ADP-ribose moieties from arginines in cellular proteins. Specifically, we analyzed cancer susceptibility in animals lacking the ADP-ribosylarginine hydrolase (ARH1) that cleaves the ADP ribose-protein bond. ARH1(-/-) cells or ARH1(-/-) cells overexpressing an inactive mutant ARH1 protein (ARH1(-/-)+dm) had higher proliferation rates than either wild-type ARH1(+/+) cells or ARH1(-/-) cells engineered to express the wild-type ARH1 enzyme. More significantly, ARH1(-/-) and ARH1(+/-) mice spontaneously developed lymphomas, adenocarcinomas, and metastases more frequently than wild-type ARH1(+/+) mice. In ARH1(+/-) mice, we documented in all arising tumors mutation of the remaining wild-type allele (or loss of heterozygosity), illustrating the strict correlation that existed between tumor formation and absence of ARH1 gene function. Our findings show that proper control of protein ADP-ribosylation levels affected by ARH1 is essential for cancer suppression.

Potential tumor-tropic effect of genetically engineered stem cells expressing suicide enzymes to selectively target invasive cancer in animal models

Stem cells have recently received a great deal of attention for their clinical and therapeutic potential to treat human disease and disorders. For instance, neural stem cells expressing a suicide gene which can concert prodrugs to their active metabolites may have great tropic and therapeutic potential for brain tumors, i.e., medulloblastoma and glioma. We are currently interested in therapeutic potential of these genetically engineered stem cells (GESTECs) to selectively target invasive tumors, i.e. ovarian, endometrial, breast, and lung cancer which can have a great impact on human and animal health. Thus, in this review we summarize the therapeutic potential of GESTEC, developed by us, and the putative mechanism(s) underlying their therapeutic and tropic potential in expressing suicide genes which can convert prodrugs to their active metabolites and in selectively targeting invasive tumors.

Inhibition of HIF prolyl hydroxylase-2 blocks tumor growth in mice through the antiproliferative activity of TGFβ

Virtually all solid tumors are dependent on a vascular network to provide them with the right amount of nutrients and oxygen. In that sense, low oxygen tension or hypoxia leads to an adaptive response that is transcriptionally regulated by the hypoxia-inducible factors (HIF), which are tightly controlled by the HIF prolyl hydroxylases (PHD). In this study, we show that inhibition of the oxygen sensor PHD2 in tumor cells stimulates vessel formation but paradoxically results in a profound reduction of tumor growth. This effect relies on the antiproliferative nature of the TGFβ signaling pathway, in a largely HIF-independent manner. Moreover, our findings reveal that PHD2 has an essential function in controlling the dual nature of TGFβ during tumorigenesis and may offer an alternative opportunity for anticancer therapy.

[Effect of low doses of x-ray irradiation on the liver detoxication system in rats with transplanted Guerin's carcinoma]

The activity of detoxication enzymes in liver microsomal fraction of preliminary radiation-exposed rats was investigated. It was shown that preliminary organism exposure to radiation reduced cytochrome P450 and glutathione-S-transferase activity in liver microsomal fraction in the latent and logarithmic phases of oncogenesis compared with the unirradiated rats with tumor. Low level of cytochrome P450 activity can be caused by transition of microsomal cytochrome P450 in P420 inactive form. The preliminary radiation does not influence the enzyme activity of liver cytochrome P450 and glutathione-S-transferase on terminal stages of Guerin's carcinoma growth.

Induction of thymidine kinase 1 after 5-fluorouracil as a mechanism for 3'-deoxy-3'-[18F]fluorothymidine flare

Imaging the pharmacodynamics of anti-cancer drugs may allow early assessment of anti-cancer effects. Increases in 3'-deoxy-3'-[(18)F]fluorothymidine ([(18)F]FLT) uptake early after thymidylate synthase inhibition (TS) inhibition, the so-called flare response, is considered to be largely due to an increase in binding sites for type-1 equilibrative nucleoside transporter. We investigated the induction of thymidine kinase 1 (TK1) after 5-fluorouracil (5-FU) treatment as one of mechanisms for [(18)F]FLT flare. Exposure of nine cancer cell lines to 5-FU for 24h induced a 2.5- to 3.5-fold increase in [(18)F]FLT uptake, significantly higher than the 1.5-fold increase observed 2h after treatment. The increase of [(18)F]FLT uptake 24h after 5-FU exposure accompanied TK1 induction in most cell lines. In representative cell lines (A431 and HT29), 5-FU time-dependently increased [(18)F]FLT uptake, kinase activity and the levels of protein and mRNA for TK1, sequential cyclin E and A induction, and G(1)-S phase transition. Cycloheximide treatment and knockdown of TK1 completely inhibited 5-FU-induced [(18)F]FLT flare. On the other hand, HCT8 cells showed a biphasic [(18)F]FLT flare with lacked TK1 induction in response to the dosage of 5-FU. Cycloheximide did not inhibit 5-FU-induced [(18)F]FLT flare in this cells. In vivo dynamic [(18)F]FLT-PET and ex vivo analysis in HT29 tumor-bearing mice showed significantly increased [(18)F]FLT flux and TK1 activity of tumor tissue 24h after 5-FU administration (P<0.05). Conclusively, 5-FU induced TK1 and TK1-mediated high [(18)F]FLT flare in most of cell lines. [(18)F]FLT-PET may be used to assess pharmacodynamics of TS inhibitor by a mechanism involving TK1 induction.

Inositol 1,4,5-trisphosphate 3-kinase-A is a new cell motility-promoting protein that increases the metastatic potential of tumor cells by two functional activities

Cellular migration is an essential prerequisite for metastatic dissemination of cancer cells. This study demonstrates that the neuron/testis-specific F-actin-targeted inositol 1,4,5-trisphosphate 3-kinase-A (ITPKA) is ectopically expressed in different human tumor cell lines and during tumor progression in the metastatic tumor model Balb-neuT. High expression of ITPKA increases invasive migration in vitro and metastasis in a xenograft SCID mouse model. Mechanistic studies show that ITPKA promotes migration of tumor cells by two different mechanisms as follows: growth factor independently high levels of ITPKA induce the formation of large cellular protrusions by directly modulating the actin cytoskeleton. The F-actin binding activity of ITPKA stabilizes and bundles actin filaments and thus increases the levels of cellular F-actin. In growth factor-stimulated cells, the catalytically active domain enhances basal ITPKA-induced migration by activating store-operated calcium entry through production of inositol 1,3,4,5-tetrakisphosphate and subsequent inhibition of inositol phosphate 5-phosphatase. These two functional activities of ITPKA stimulating tumor cell migration place the enzyme among the potential targets of anti-metastatic therapy.

Distinct concentration-dependent effects of the polo-like kinase 1-specific inhibitor GSK461364A, including differential effect on apoptosis

Polo-like kinase 1 (Plk1) is a conserved serine/threonine kinase that plays an essential role in regulating the many processes involved in mitotic entry and progression. In humans, Plk1 is expressed primarily during late G(2) and M phases and, in conjunction with Cdk1/cyclin B1, acts as master regulatory kinases for the myriad protein substrates involved in mitosis. Plk1 overexpression is strongly associated with cancer and has been correlated with poor prognosis in a broad range of human tumor types. We have identified a potent, selective, reversible, ATP-competitive inhibitor of Plk1, GSK461364A, capable of inhibiting cell growth of most proliferating cancer cell lines tested. We observe distinct cell cycle effects of GSK461364A depending on the dose used. The predominant phenotype for cells treated with GSK461364A is prometaphase arrest with characteristic collapsed polar polo spindle. At high concentrations, GSK461364A delays mitotic entry in G(2) followed by gradual progression into terminal mitosis; in some cell lines, this correlates with decreased apoptosis. Cell culture growth inhibition by GSK461364A can be cytostatic or cytotoxic but leads to tumor regression in xenograft tumor models under proper dose scheduling. Finally, we describe pharmacodynamic biomarkers of GSK461364A activity (pHH3 and Plk1) that are currently being evaluated in human cancer clinical trials.

Development of a novel cell-based assay to evaluate the malignant potential of cancer in vitro

BACKGROUND

Metastasis is a leading cause of cancer death. To evaluate the complex metastatic process in vitro, an attempt was made to develop a cell-based assay (Can kit) that could evaluate the late stages of metastasis.

MATERIALS AND METHODS

Two membrane chambers were set up of which the upper membrane chamber with 8 mum pores was covered with normal cell layers. Cancer cells were introduced to the upper chamber and after passing through the normal cell layers dropped through onto the lower chamber membrane where cancer colonies formed and were evaluated based on the reduction of transepithelial electrical resistance (TEER) with a Madin-Darby canine kidney (MDCK) cell monolayer.

RESULTS

When two pairs of cancer cell lines, with different metastatic potentials in vivo, were applied to the Can kit assay, differences in potentials between the two cell lines in vitro were demonstrated. The reduction in the TEER was correlated with the total area of the cancer colonies and the production of matrix metalloproteinases (MMPs).

CONCLUSION

A cell-based assay able to evaluate the malignant potential of cancer in vitro was developed and is considered to be useful for research and the clinical examination of cancer metastatic potential.

Capsaicin alleviates the imbalance in xenobiotic metabolizing enzymes and tumor markers during experimental lung tumorigenesis

Lung cancer is currently a leading cause of death all over the world. Environmental risk factors, particularly genotoxic chemicals such as polycyclic aromatic hydrocarbons (PAH), are likely to account for a much higher mortality. Xenobiotic metabolizing enzymes are potentially chief determinants in both the susceptibility to the mutagenic effects of chemical carcinogens and in the response of tumors to chemotherapy. The well-known carcinogen benzo(a)pyrene (B(a)P) of PAH family was given orally (50 mg/kg body weight) to induce lung cancer in Swiss albino mice. B(a)P induction altered the levels of cytochromes (P450, b5), activities of phase I biotransformation enzymes (NADPH-cytochrome P450 reductase, NADH-cytochrome b5 reductase and epoxide hydrolase), phase II enzymes (glutathione-S-transferase, UDP-glucuronyl transferase and DT-diaphorase), and the levels of serum tumor markers. Treatment with capsaicin (CAP) (10 mg/kg body weight) to the lung carcinoma mice restored back the activities of phase I and II biotransformation enzymes and the levels of tumor markers to near normalcy. The above findings were substantiated by immunoblotting and immunohistochemical analysis of cytochrome P450 1A1 (CYP1A1) in the lung tissues. Our present study unravels that CAP can effectively detoxify the carcinogens which discloses its anti-carcinogenic effect during experimental lung cancer.

Organ-specific profiles of genetic changes in cancers caused by activation-induced cytidine deaminase expression

Various molecular changes characterizing organ-specific carcinogenesis have been identified in human tumors; however, the molecular mechanisms of the genomic changes specific for each cancer are not well defined. A transgenic (Tg) mouse model with constitutive expression of the nucleotide-editing enzyme, activation-induced cytidine deaminase (AID), develops tumors in various organs as a result of the mutagenic activities of AID. This phenotypic character of AID Tg mice allowed us to analyze the organ-specific genetic changes in tumor-related genes commonly triggered by AID-mediated mutagenesis. Among the 80 AID Tg mice analyzed, 11 mice developed hepatocellular carcinomas, and 7 developed lung cancers. In addition, 1 developed the gastric cancer and 3 developed gastric adenomas. Organ-specific preferences for nucleotide changes were observed in some of the tumor-related genes in each epithelial tissue of the AID Tg mice. Of note, the c-myc and K-ras genes were the preferential targets of the mutagenic activity of AID in lung and stomach cancers, respectively, whereas mutations in the p53 and beta-catenin genes were commonly observed in all 3 organs. Quantitative RT-PCR analyses revealed that alpha-fetoprotein, insulin-like growth factor-2 and cyclin D1 genes were specifically upregulated in HCC, whereas upregulation of the matrix metalloproteinase-7 gene was more marked in lung cancer. Our findings suggest that AID, a DNA mutator that plays a critical role linking inflammation to human cancers, might be involved in the generation of organ-specific genetic diversity in oncogenic pathways during cancer development.

[Xanthine oxidase activity in transplantable Guerin's carcinoma in rats]

Influence of low-dosage pre-irradiation on xanthine oxidase levels in Guerin's carcinoma was studied with particular emphasis on free oxygen generation and free sulphohydrils in a fraction of proteins characterized by xanthine oxidase activity. Enhanced growth of tumor correlated with that of xanthine oxidase activity involving higher levels of enzymatic O-form due to thiol groups oxidation. Under similar conditions, xanthine oxidase and free oxygen generation levels were higher due to SH-group oxidation than in intact animals. Terminal stages involved dropping xanthine oxidase levels and enzymatic protein degradation.