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Tumor Promotion (tumor + promotion)
Selected AbstractsMechanisms by which inflammation may increase intestinal cancer risk in inflammatory bowel diseaseINFLAMMATORY BOWEL DISEASES, Issue 8 2010Pamela M. O'Connor PhD Abstract Patients with ulcerative colitis and Crohn's disease are at increased risk of developing intestinal cancers via mechanisms that remain incompletely understood. However, chronic inflammation and repeated events of inflammatory relapse in inflammatory bowel disease (IBD) expose these patients to a number of signals known to have tumorigenic effects including persistent activation of the nuclear factor-,B and cyclooxygenase-2/prostaglandin pathways, release of proinflammatory mediators such as tumor necrosis factor-, and interleukin-6, and enhanced local levels of reactive oxygen and nitrogen species. These inflammatory signals can contribute to carcinogenesis via 3 major processes: 1) by increasing oxidative stress, which promotes DNA mutagenesis thus contributing to tumor initiation; 2) by activating prosurvival and antiapoptotic pathways in epithelial cells, thereby contributing to tumor promotion; and 3) by creating an environment that supports sustained growth, angiogenesis, migration, and invasion of tumor cells, thus supporting tumor progression and metastasis. The present review integrates clinical and basic research observations in an attempt to provide a comprehensive understanding of how inflammatory processes may contribute to intestinal cancer development in IBD patients. (Inflamm Bowel Dis 2010) [source] Inositol hexaphosphate inhibits ultraviolet B,induced signal transductionMOLECULAR CARCINOGENESIS, Issue 3 2001Nanyue Chen Abstract Inositol hexaphosphate (InsP6) has an effective anticancer action in many experimental models in vivo and in vitro. Ultraviolet B (UVB) radiation is believed to be responsible for many of the carcinogenic effects related to sun exposure, and alteration in UVB-induced signal transduction is associated with UVB-induced carcinogenesis. Here we report the effects of InsP6 on UVB-induced signal transduction. InsP6 strongly blocked UVB-induced activator protein-1 (AP-1) and NF-,B transcriptional activities in a dose-dependent manner. InsP6 also suppressed UVB-induced AP-1 and nuclear factor ,B (NF-,B) DNA binding activities and inhibited UVB-induced phosphorylation of extracellular signal-regulated protein kinases (Erks) and c-Jun NH2-terminal kinases (JNKs). Phosphorylation of p38 kinases was not affected. InsP6 also blocked UVB-induced phosphorylation of I,B-,, which is known to result in the inhibition of NF-,B transcriptional activity. InsP6 does not block UVB-induced phosphotidylinositol-3, (PI-3) kinase activity, suggesting that the inhibition of UVB-induced AP-1 and NF-,B activities by InsP6 is not mediated through PI-3 kinase. Because AP-1 and NF-,B are important nuclear transcription factors that are related to tumor promotion, our work suggests that InsP6 prevents UVB-induced carcinogenesis by inhibiting AP-1 and NF-,B transcription activities. © 2001 Wiley-Liss, Inc. [source] 6-Shogaol is more effective than 6-gingerol and curcumin in inhibiting 12- O -tetradecanoylphorbol 13-acetate-induced tumor promotion in miceMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 9 2010Hou Wu Abstract We previously reported that 6-shogaol strongly suppressed lipopolysaccharide-induced overexpression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in murine macrophages. In this study, we further compared curcumin, 6-gingerol, and 6-shogaol's molecular mechanism of action and their anti-tumor properties. We demonstrate that topical application of 6-shogaol more effectively inhibited 12- O -tetradecanoylphorbol 13-acetate (TPA)-stimulated transcription of iNOS and COX-2 mRNA expression in mouse skin than curcumin and 6-gingerol. Pretreatment with 6-shogaol has resulted in the reduction of TPA-induced nuclear translocation of the nuclear factor-,B subunits. 6-Shogaol also reduced TPA-induced phosphorylation of I,B, and p65, and caused subsequent degradation of I,B,. Moreover, 6-shogaol markedly suppressed TPA-induced activation of extracellular signal-regulate kinase1/2, p38 mitogen-activated protein kinase, JNK1/2, and phosphatidylinositol 3-kinase/Akt, which are upstream of nuclear factor-,B and AP-1. Furthermore, 6-shogaol significantly inhibited 7,12-dimethylbenz[a]anthracene/TPA-induced skin tumor formation measured by the tumor multiplicity of papillomas at 20,wk. Presented data reveal for the first time that 6-shogaol is an effective anti-tumor agent that functions by down-regulating inflammatory iNOS and COX-2 gene expression in mouse skin. It is suggested that 6-shogaol is a novel functional agent capable of preventing inflammation-associated tumorigenesis. [source] Requirement for Metalloproteinase-dependent ERK and AKT Activation in UVB-induced G1-S Cell Cycle Progression of Human KeratinocytesPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2009Weinong Han UVB (280,315 nm) in natural sunlight represents a major environmental challenge to the skin and is clearly associated with human skin cancer. Here we demonstrate that low doses of UVB induce keratinocyte proliferation and cell cycle progression of human HaCaT keratinocytes. Different from UVA, UVB irradiation induced extracellular signal-regulated kinase (ERK) and AKT activation and their activation are both required for UVB-induced cell cycle progression. Activation of epidermal growth factor receptor (EGFR) was observed after UVB exposure and is upstream of ERK/AKT/cyclin D1 pathway activation and cell cycle progression following UVB radiation. Furthermore, metalloproteinase (MP) inhibitor GM6001 blocked UVB-induced ERK and AKT activation, cell cycle progression, and decreased the EGFR phosphorylation, demonstrating that MPs mediate the EGFR/ERK/AKT/cyclin D1 pathways and cell cycle progression induced by UVB radiation. In addition, ERK or AKT activation is essential for EGFR activation because ERK or AKT inhibitor blocks EGFR activation following UVB radiation, indicating that EGFR/AKT/ERK pathways form a regulatory loop and converge into cell cycle progression following UVB radiation. Identification of these signaling pathways in UVB-induced cell cycle progression of quiescent keratinocytes as a process mimicking tumor promotion in vivo will facilitate the development of efficient and safe chemopreventive and therapeutic strategies for skin cancer. [source] Cyclooxygenase-2 Expression in Murine and Human Nonmelanoma Skin Cancers: Implications for Therapeutic Approaches,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2002Kathy P. An ABSTRACT Inflammatory stimuli result in the production of cutaneous eicosanoids, which are known to contribute to the process of tumor promotion. Cyclooxygenase (COX), the rate-limiting enzyme for the production of prostaglandins (PG) from arachidonic acid, exists in at least two isoforms, COX-1 and COX-2. COX-1 is constitutively expressed in most tissues and plays various physiological roles, whereas increased COX-2 expression is known to occur in several types of epithelial neoplasms. Enhanced PG synthesis is a potential contributing factor in UVB-induced nonmelanoma skin cancers (NMSC). Increased COX-2 staining occurs in murine skin neoplasms after chronic exposure to carcinogenic doses of UVB. In this study, immunohistochemical and Western blot analyses were employed to assess longitudinally COX-2 expression in a standard mouse UVB complete carcinogenesis protocol and in human basal cell carcinomas (BCC) and squamous cell carcinomas (SCC). During UVB irradiation of mice, COX-2 expression consistently increased in the hyperplastic skin, the benign papillomas and the SCC. COX-2 expression was also increased in human actinic keratoses, SCC and BCC as well as in murine SCC and BCC. The pattern of COX-2 expression was quite variable, occurring in a patchy distribution in some lesions with staining confined mainly to suprabasal cell layers. In general, COX-2 expression progressively became more extensive in benign papillomas and well-differentiated murine SCC. The staining was predominantly cytoplasmic and perinuclear in some focal areas in tissue stroma around both murine and human tumors. Western blot analysis confirmed negative COX-2 expression in normal skin, whereas acute UVB exposure resulted in increased enzyme expression, which continued to increase in developing papillomas and SCC. Because of the evidence indicating a pathogenic role for eicosanoids in murine and human skin neoplasms, we performed studies to assess the anti-inflammatory and anticarcinogenic effects of green tea extracts, which are potent antioxidants. Acute exposure of the human skin to UVB (minimum erythema dose × 4) caused a transient enhancement of the COX-2 expression, which reverted to baseline within hours; however, in murine skin the expression persisted for several days. Pretreatment with the topically applied green tea extract (1 mg/cm2) largely abrogated the acute COX-2 response to UVB in mice or humans. In summary, enhanced COX-2 expression serves as a marker of epidermal UVB exposure for murine and human NMSC. These results suggest that COX-2 inhibitors could have potent anticarcinogenic effects in UVB-induced skin cancer. [source] Toward the development of new medicinal leads with selectivity for protein kinase C isozymesTHE CHEMICAL RECORD, Issue 4 2005Kazuhiro Irie Abstract Tumor promoters such as phorbol esters bind strongly to protein kinase C (PKC) isozymes to induce their activation. Since each PKC isozyme is involved in diverse biological events in addition to tumor promotion, the isozymes serve as promising therapeutic targets. Tumor promoters bind to the C1A and/or C1B domain of conventional (,, ,I, ,II, and ,) and novel PKC isozymes (,, ,, ,, and ,). As these C1 domains play differential roles in PKC activation and their translocation in cells, the development of agents with binding selectivity for individual C1 domains is a pressing need. For this purpose, we established a synthetic C1 peptide library of all PKC isozymes. The library enabled us to identify indolactam-V (1) as a promising lead compound. Our diverse structure,activity studies on 1 indicated that the position of the hydrophobic substituent on the indole ring dominates the PKC isozyme- and C1 domain-selective binding rather than conformation of the nine-membered lactam. Moreover, we suggested that the indole ring of 1 could be involved in the CH/, interaction with Pro-11 of the C1B domain of PKC,. This invaluable information will lead to the structural optimization of the PKC, ligand as exemplified by the design and synthesis of naphtholactam-V8 (21). © 2005 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 5: 185,195; 2005: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20044 [source] Cancer chronotherapy: Principles, applications, and perspectivesCANCER, Issue 1 2003Marie-Christine Mormont Ph.D. Abstract BACKGROUND Cell physiology is regulated along the 24-hour timescale by a circadian clock, which is comprised of interconnected molecular loops involving at least nine genes. The cellular clocks are coordinated by the suprachiasmatic nucleus, a hypothalamic pacemaker that also helps the organism adjust to environmental cycles. The rest-activity rhythm is a reliable marker of the circadian system function in both rodents and humans. This circadian organization is responsible for predictable changes in the tolerability and efficacy of anticancer agents, and possibly also may be involved in tumor promotion or growth. METHODS Expected least toxic times of chemotherapy were extrapolated from experimental models to human subjects with reference to the rest-activity cycle. The clinical relevance of the chronotherapy principle (i.e., treatment administration as a function of rhythms) has been investigated previously in randomized multicenter trials. RESULTS In the current study, chronotherapeutic schedules were used to safely document activity of the combination of oxaliplatin, 5-fluorouracil, and leucovorin against metastatic colorectal carcinoma and to establish new medicosurgical management for this disease, and were reported to result in unprecedented long-term survival. CONCLUSIONS Chronotherapy concepts appear to offer further potential to improve current cancer treatment options as well as to optimize the development of new anticancer or supportive agents. Cancer 2003;97:155,69. © 2003 American Cancer Society. DOI 10.1002/cncr.11040 [source] Insulin-independent promotion of chemically induced hepatocellular tumor development in genetically diabetic miceCANCER SCIENCE, Issue 1 2010Kohtaro Yamasaki Diabetes mellitus has been proposed as an epidemiological risk factor for human liver cancer development. One reasonable possibility is that this is attributable to hyperinsulinemia compensatory for obesity-related insulin resistance. However, diabetes mellitus is a complex disease with multiple abnormal conditions essentially caused by hyperglycemia. Therefore, it is not evident whether hyperinsulinemia is prerequisite for the elevated cancer risk. To gain a clue to answer this question, we characterized chemically induced hepatocarcinogenesis in diabetic model mice genetically deficient for insulin. Akita inbred mice originating from the C57BL/6 strain carry a heterozygous germline mutation of the insulin II gene and suffer from inherited insulin deficiency and diabetes in an autosomal dominant manner. They were mated with normal C3H/HeJ mice with high sensitivity to liver carcinogenesis and the resultant F1 littermates, which were either normal or insulin deficient, were exposed to diethylnitrosamine and induced hepatocellular tumors were evaluated for number, size, proliferative activity, and apoptosis. Unexpectedly, both mean and total volumes of hepatocellular tumors in the insulin-deficient animals were more than twofold larger than those in the normal controls, with no significant difference in tumor number. The tumors in insulin-deficient mice showed a significantly lower frequency of apoptosis but no alteration in cell proliferation. In conclusion, our results indicate that insulin-independent liver tumor promotion occurred in diabetic mice. Clearly, insulin-independent mechanisms for the human case also deserve consideration. (Cancer Sci 2009) [source] Antitumor-Promoting Effects and Cytotoxic Activities of Dammar Resin Triterpenoids and Their DerivativesCHEMISTRY & BIODIVERSITY, Issue 8 2010Motohiko Ukiya Abstract Nineteen known triterpenoids, 1,19, and one known sesquiterpenoid, 20, were isolated from dammar resin obtained from Shorea javanica K. & V. (Dipterocarpaceae). One of the acidic triterpenoids, dammarenolic acid (1), was converted to fourteen derivatives, namely, an alcohol, 21, an aldehyde, 22, and twelve L -amino acid conjugates, 23,34. Compounds 1,34 were examined for their inhibitory effects on the induction of Epstein,Barr virus early antigen (EBV-EA) by 12- O -tetradecanoylphorbol 13-acetate (TPA) in Raji cells, a known primary screening test for antitumor promoters. All of the compounds tested, except for compounds 4, 5, 12,14, 16, and 17, showed inhibitory effects against EBV-EA activation with potencies either comparable with or stronger than that of , -carotene, a known natural antitumor promoter. In addition, (20S)-20-hydroxy-3,4-secodammara-4(28),24-dien-3-al (22) exhibited inhibitory effects on skin tumor promotion in an in vivo two-stage mouse skin carcinogenesis test based on 7,12-dimethylbenz[a]anthracene (DMBA) as initiator, and with TPA as promoter. Furthermore, evaluation of the cytotoxic activities of compounds 1,34 against human cancer cell lines showed that reduction (i.e., 21 and 22) or conjugation with L -amino acids (i.e., 23,34) of compound 1 enhanced the cytotoxicity against human melanoma cell line CRL1579. [source] | ||||||||||||||||