Attenuation by genistein of sodium‐chloride‐enhanced gastric carcinogenesis induced by N‐methyl‐N′‐nitro‐N‐nitrosoguanidine in Wistar rats

The effects of prolonged administration of genistein, a tyrosine‐kinase inhibitor, on sodium‐chloride‐enhanced induction of gastric carcinogenesis induced by N‐methyl‐N′‐nitro‐N‐nitrosoguanidine, and the labeling and apoptotic indices and vessel counts in the gastric mucosa and gastric cancers, were investigated in Wistar rats. After 25 weeks of the carcinogen treatment, rats were fed chow pellets containing 10% sodium chloride and were given s.c. injections of genistein at dosages of 15 mg/kg or 30 mg/kg body weight every other day. In week 52, the incidence of gastric cancers was significantly greater in rats fed sodium chloride than in untreated control rats. Prolonged administration of genistein at a dosage of 30 mg/kg, but not 15 mg/kg, body weight significantly reduced the incidence of gastric cancers, which was increased by oral treatment with sodium chloride. Genistein at the higher dose significantly decreased the labeling index and vessel counts of the antral mucosa and the gastric cancers (which were increased by treatment with sodium chloride) and significantly increased the apoptotic index of the antral mucosa and the cancers (which was lowered by the treatment with sodium chloride). These findings suggest that genistein attenuates gastric carcinogenesis promoted by sodium chloride, by inducing increased apoptosis and lower cell proliferation and angiogenesis of antral mucosa and gastric cancers. Int. J. Cancer 80:396–399, 1999. © 1999 Wiley‐Liss, Inc.     

Attenuation by methionine of monochloramine-enhanced gastric carcinogenesis induced by N-methyl- N′-nitro- N-nitrosoguanidine in Wistar rats

Helicobacter pylori appears to play a major role in the development of gastric cancer in humans. The mechanism behind the carcinogenic or co-carcinogenic effects of H. pylorihas not been established. Ammonia, generated by urea from H. pylori, has been studied as a possible cause. However, the ammonia-monochloramine system has been shown to play a more important role in H. pylori-associated mucosal injury. Therefore, the effects of combined administration of monochloramine and methionine, singly or together, on the development of gastric cancers induced by N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) were investigated in inbred Wistar rats. After receiving oral MNNG and regular chow pellet for 25 weeks, rats received regular chow pellets or chow pellets containing 20% ammonium acetate, and normal tap water or water containing 30 mM sodium hypochlorite, with or without a subcutaneous injection of methionine, until the end of the experiment (week 52). Treatment with both ammonium acetate and sodium hypochlorite, which produce monochloramine, significantly increased the incidence of gastric cancers in week 52, whereas the concomitant administration of methionine with ammonium acetate and sodium hypochlorite significantly attenuated such enhanced gastric carcinogenesis. Spectrophotometric examination revealed that methionine scavenged monochloramine. Our findings suggest that H. pylori-associated gastric carcinogenesis may be mediated by monochloramine. Int. J. Cancer 76:73–76, 1998.© 1998 Wiley-Liss, Inc.     

α1-adrenoceptor stimulation enhances experimental gastric carcinogenesis induced by N-methyl- N′-nitro- N-nitrosoguanidine in Wistar rats

The effect of prolonged administration of the norepinephrine-mimicking agent metaraminol, the α₁-adrenergic agonist phenylephrine and the α₂-adrenergic agonist clonidine on the incidence of gastric cancers induced by N-methyl-N′-nitro-N-nitrosoguanidine (MNNG), the ornithine decarboxylase activity of the gastric cancer and the labeling index of the gastric mucosa were investigated in Wistar rats. Rats received s.c. injections of metaraminol, phenylephrine or clonidine every other day after 20 weeks of oral treatment with MNNG. At week 52, administration of metaraminol and phenylephrine at the higher dose significantly increased the incidence of gastric cancers, the ornithine decarboxylase activity of the gastric cancers and the labeling index of the antral epithelial cells. Administration of phenylephrine at the lower dose and clonidine at both doses had no significant effect on the incidence of gastric cancers, the ornithine decarboxylase activity of the gastric cancers or the labeling index of the gastric mucosa. Our results suggest that adrenoreceptor stimulation enhances gastric carcinogenesis and that such enhancement is mediated through α₁-adrenoceptors without α₂-adrenoceptor involvement. Int. J. Cancer 77:467–469, 1998. © 1998 Wiley-Liss, Inc.     

Induction and promotion of forestomach tumors by sodium nitrite in combination with ascorbic acid or sodium ascorbate in rats with or without N-metuyl-N′-nitro-N-nitrosoguanidine pre-treatment

In experiment I, short-term effects of combined treatment with anti-oxidants, sodium ascorbate (NaAsA) and sodium nitrite (NaNO₂) on forestomach cell proliferation were examined in F344 male rats. Groups of 5 animals aged 6 weeks were treated for 4 weeks with 0.8% catechol, 0.8% hydroquinone, 1% tert butyl-hydroquinone (TBHQ), 2% gallic acid or 2% pyrogallor alone or in combination with 0.3% NaNO₂ in the drinking water and/or I % NaAsA in the diet. The thicknesses of forestomach mucosa in rats treated with anti-oxidants and NaNO₂ in combination were greater than those with antioxidant alone and additional NaAsA treatment further enhanced the thickening of mucosa. It was noteworthy that values for mucosae of animals treated with NaNO₂ and NaAsA without anti-oxidant were similar to those for anti-oxidants. In experiment 2, effects of combined treatment with NaAsA or ascorbic acid '(AsA) and NaNO₂ on carcinogenesis were examined in F344 male rats with or without N-methyl-N' -nitro-N-nitrosogua-nidine (MNNG) pre-treatment. Groups of 20 or 15 rats, respectively, aged 6 weeks, were given a single intra-gastric administration of I SO mg/kg body weight of MNNG in DMSOwater =1:1 or the vehicle alone by stomach tube. Starting I week later, they received supplements of I % NaAsA or I % AsA in the diet and 0.3% NaNO_z in drinking water in combination, each of the individual chemicals alone, or basal diet until the end of week 52. In MNNG-treated animals, incidences of forestomach papillomas and carcinomas were significantly enhanced in the NaNO₂ alone group (84 and 47%, respectively) as compared with the basal diet group (30 and 10%), with further significant increase in carcinomas occurring with additional NaAsA (79%, p < 0.05) or AsA (85%, p < 0.05) treatment. In animals without MNNG, all animals in the NaNO₂ group demonstrated mild hyperplasia, additional administration of NaAsA or AsA remarkably enhancing the grade of hyperplasia, and resulting in 53% and 20% incidences, respectively, of papillomas. Thus NaNO₂ was demonstrated to exert promoter action for forestomach carcinogenesis, with NaAsA and AsA acting as co-promoters. The results strongly indicate that combined treatment with NaAsA or AsA and NaNO₂ may induce forestomach carcinomas in the long term. © 1994 WUey-Liss, Inc.     

Inhibition of morphological transformation induced with N-methyl-N′-nitro-N-nitrosoguanidine in cultures of hamster embryo cells by 5′-bromo-2′-deoxyuridine-photolysis

The present study was performed in order to determine whether type III transformed foci induced by N-methyl-N′-nitro-N-nitrosoguanidine originate from the small subpopulation of cells stimulated by the carcinogen to enter DNA synthesis. During the last 30 min of variable treatment periods using different doses of N-methyl-N′-nitro-N-nitrosoguanidine, administered alone or in association with the thymidine analogue, 5′-bromo-2′-deoxyuridine (0.98 × 10^?5 M), the density-inhibited monolayers of hamster embryo cells were exposed to fluorescent light and then assayed for abnormal growth patterns by the focus formation method. Mock-irradiated cultures as well as monolayers whose medium lacked N-methyl-N′-nitro-N-nitro-soguanidine, 5′-bromo-2′-deoxyuridine, or both, served as controls. The cytotoxicity of 5′-bromo-2′-deoxyuridine + N-methyl-N′-nitro-N-nitrosoguanidine + photolysis (BMP) protocol on confluent as well as logarithmically growing hamster embryo cells was estimated in single-cell survival experiments. Plating efficiency determinations have demonstrated that, unlike their actively growing counterparts, confluent hamster embryo cell mono-layers are extremely resistant to the cytotoxic effects of the BMP protocol. The quantitative transformation assays indicated that: (1) in non-illuminated cultures addition of 5′-bromo-2′-deoxyuridine to carcinogen-containing medium does affect transformation frequency of hamster embryo cells in the sense that the incidence of type III foci did not subside at later intervals during the post-carcinogen administration period as it did in the absence of the analogue; (2) irradiation of N-methyl-N′-nitro-N-nitrosoguanidine and halogenated pyrimidine analogue-treated cultures with fluorescent light practically suppressed transformation; (3) analogueadded and analogue-removed experiments pointed out that the event(s) on which 5′-bromo-2′-deoxy-uridine fluorescent light sensitization of morphological transformation largely depends, takes place between 5 and 15 h after N-methyl-N′-nitro-N-nitrosoguanidine administration, i.e., during the period of maximal carcinogen-stimulated DNA synthesis; and (4) neither fluorescent light nor 5′-bromo-2′-deoxyuridine, singly or in combination, were able to transform cultures of hamster embryo cells. These findings are strong indirect arguments for the concept that carcinogen-induced DNA synthesis and the initiation of transformed clones are causally related.     

5,7,3′‐trihydroxy‐3,4′‐dimethoxyflavone‐induced cell death in human Leukemia cells is dependent on caspases and activates the MAPK pathway

Flavonoids are polyphenolic compounds which display a vast array of biological activities and are promising anticancer agents. In this study we investigated the effect of 5,7,3′‐trihydroxy‐3,4′‐dimethoxyflavone (THDF) on viability of nine human tumor cell lines and found that it was highly cytotoxic against leukemia cells. THDF induced G₂–M phase cell‐cycle arrest and apoptosis through a caspase‐dependent mechanism involving cytochrome c release, processing of multiple caspases (caspase‐3, ‐6, ‐7, and ‐9) and cleavage of poly(ADP‐ribose) polymerase. Overexpression of the protective mitochondrial proteins Bcl‐2 and Bcl‐x_L conferred partial resistance to THDF‐induced apoptosis. This flavonoid induced the phosphorylation of members of the mitogen‐activated protein kinases (MAPKs) family and cell death was attenuated by inhibition of c‐jun N‐terminal kinases/stress‐activated protein kinases (JNK/SAPK) and of extracellular signal‐regulated kinases (ERK) 1/2. In the present study we report that THDF‐induced cell death is mediated by an intrinsic dependent apoptotic event involving mitochondria and MAPKs, and through a mechanism independent of the generation of reactive oxygen species. The results suggest that THDF could be useful in the development of novel anticancer agents. Mol. Carcinog. © 2010 Wiley‐Liss, Inc.     

A newly synthesized compound, 4′‐geranyloxyferulic acid–N(omega)‐nitro‐l‐arginine methyl ester suppresses inflammation‐associated colorectal carcinogenesis in male mice

We previously reported the cancer chemopreventive activity of 4′‐geranyloxyferulic acid (GOFA, Miyamoto et al., Nutr Cancer 2008; 60:675‐84) and a β‐cyclodextrin inclusion compound of GOFA (Tanaka et al., Int J Cancer 2010; 126:830‐40) in colitis‐related colorectal carcinogenesis. In our study, the chemopreventive effects of a newly synthesized GOFA‐containing compound, GOFA–N(omega)‐nitro‐l ‐arginine methyl ester (L‐NAME), which inhibits inducible nitric oxide (iNOS) and cyclooxygenase‐2 (COX) enzymes, were investigated using a colitis‐associated mouse colorectal carcinogenesis model with azoxymethane (AOM) and dextran sodium sulfate (DSS). The dietary administration of GOFA–L‐NAME after the AOM and DSS treatments significantly reduced the multiplicity of adenocarcinomas (inhibition rates: 100 ppm, 84%, p < 0.001; 500 ppm, 94%, p < 0.001) compared with the AOM + DSS group. Dietary GOFA–L‐NAME significantly decreased the proliferation (p < 0.001) and increased the apoptosis (p < 0.001) of colonic adenocarcinoma cells. A subsequent short‐term experiment revealed that dietary GOFA–L‐NAME decreased the mRNA expression of inflammatory enzymes, such as iNOS and COX‐2, and proinflammatory cytokines, such as tumor necrosis factor‐α, interleukin (IL)?1β, IL‐6 and macrophage inflammatory protein (MIP)?2 in the colonic mucosa of mice that received 1.5% DSS in their drinking water for 7 days. Our findings indicate that GOFA–L‐NAME is able to inhibit colitis‐associated colon carcinogenesis by modulating inflammation, proliferation, apoptosis and the expression of proinflammatory cytokines in mice.     

Aspartate‐modified doxorubicin on its N‐terminal increases drug accumulation in LAT1‐overexpressing tumors

L‐type amino acid transporter 1 (LAT1), overexpressed on the membrane of various tumor cells, is a potential target for tumor‐targeting therapy. This study aimed to develop a LAT1‐mediated chemotherapeutic agent. We screened doxorubicin modified by seven different large neutral amino acids. The aspartate‐modified doxorubicin (Asp‐DOX) showed the highest affinity (Km = 41.423 μmol/L) to LAT1. Aspartate was attached to the N‐terminal of DOX by the amide bond with a free carboxyl and a free amino group on the α‐carbon atom of the Asp residue. The product Asp‐DOX was characterized by HPLC/MS. In vitro, Asp‐DOX exerted stronger inhibition on the cancer cells overexpressing LAT1 and the uptake of Asp‐DOX was approximately 3.5‐fold higher than that of DOX in HepG2 cells. Pharmacokinetic data also showed that Asp‐DOX was expressed over a longer circulation time (t_1/2 = 49.14 min) in the blood compared to DOX alone (t_1/2 = 15.12 min). In HepG2 and HCT116 tumor‐bearing mice, Asp‐DOX achieved 3.1‐fold and 6.4‐fold accumulation of drugs in tumor tissue, respectively, than those of the unmodified DOX. More importantly, treatment of tumor‐bearing mice with Asp‐DOX showed a significantly stronger inhibition of tumor growth than mice treated with free DOX in HepG2 tumor models. Furthermore, after Asp modification, Asp‐DOX avoided MDR mediated by P‐glycoprotein. These results suggested that the Asp‐DOX modified drug may provide a new treatment strategy for tumors that overexpress LAT1 and MDR1.     

Synergistic efficacy of RLIP inhibition and 2′‐hydroxyflavanone against DMBA‐induced mammary carcinogenesis in SENCAR mice

Substantial evidence suggests that 7,12‐dimethylbenzanthracene (DMBA)‐induced mammary carcinogenesis in mice mimics human breast cancer (BC) in many respects. Therefore, it has been used extensively to evaluate preventive and therapeutic agents for human BC. Mammary carcinogenesis induced by DMBA administration in female SEN sitive to CAR cinogen (SENCAR) mice was characterized by histopathological analysis of the mammary glands and alterations to the phosphatidylinositol 3‐kinase/protein kinase B/cyclin‐dependent kinase 1 (PI3K/Akt/CDK1) pathway. We recently reported that 2′‐hydroxyflavanone (2HF) is a promising diet‐derived chemotherapeutic agent that suppresses BC growth in vitro and in vivo by targeting a 76 kDa ral‐interacting protein (RLIP). The objective of the current study was to investigate the synergistic anticarcinogenic effects of RLIP inhibition/depletion and 2HF in an in vivo model of DMBA‐induced mammary carcinogenesis in SENCAR mice. Mice were given 2HF (50 mg/kg, bw, orally on alternate days), RLIP antibody (Rab; 5 mg/kg, bw, ip weekly), RLIP antisense (RAS; 5 mg/kg, b.w., ip weekly), or a combination of 2HF + Rab + RAS. Animals were monitored daily, and 7 days after the first appearance of moribund behavior, tissues were harvested for morphological and immunohistological analysis. Western blot analyses were performed to determine the expression of anti‐ and proapoptotic proteins in the mammary glands. Our results reveal that 2HF, RAS, and Rab significantly prevented the carcinogenic effects of DMBA administration in the mammary glands and other organs. Further, mice treated with a combination of 2HF + RAS + Rab exhibited no carcinogenic effect of DMBA as compared to either or the single agent‐treated mice. This study demonstrates for the first time the anticarcinogenic effects of 2HF and RLIP inhibition/depletion in vivo in a novel DMBA‐induced model of BC in SENCAR mice and provides the rationale for further clinical investigation.     

Prevention of cigarette smoke–induced lung tumors in mice by budesonide,phenethyl isothiocyanate,and N‐acetylcysteine

Lung cancer is the most important cause of death among neoplastic diseases worldwide, and cigarette smoke (CS) is the major risk factor for cancer. Complementarily to avoidance of exposure to CS, chemoprevention will lower the risk of cancer in passive smokers, ex‐smokers, and addicted current smokers who fail to quit smoking. Unfortunately, chemoprevention clinical trials have produced disappointing results to date and, until recently, a suitable animal model evaluating CS carcinogenicity was not available. We previously demonstrated that mainstream CS induces a potent carcinogenic response when exposure of mice starts at birth. In the present study, neonatal mice (strain H) were exposed to CS for 120 consecutive days, starting at birth. The chemopreventive agents budesonide (2.4 mg/kg diet), phenethyl isothiocyanate (PEITC, 1,000 mg/kg diet), and N‐acetyl‐L‐cysteine (NAC, 1,000 mg/kg body weight) were administered orally according to various protocols. The experiment was stopped after 210 days. Exposure to CS resulted in a high incidence and multiplicity of benign lung tumors and in significant increases of malignant lung tumors and other histopathological alterations. All three chemopreventive agents, administered to current smokers after weaning, were quite effective in protecting both male and female mice from CS pulmonary carcinogenicity. When given to ex‐smokers after withdrawal of exposure to CS, the protective capacity of budesonide was unchanged, while PEITC lost part of its cancer chemopreventive activity. In conclusion, the proposed experimental model provides convincing evidence that it is possible to prevent CS‐induced lung cancer by means of dietary and pharmacological agents.     

3,3′‐diindolylmethane suppresses 12‐O‐tetradecanoylphorbol‐13‐acetate‐induced inflammation and tumor promotion in mouse skin via the downregulation of inflammatory mediators

3,3′‐Diindolylmethane (DIM) is a major acid‐condensation product of indole‐3‐carbinol and is present in cruciferous vegetables. In this study, we evaluated the effects of DIM on antiinflammatory and antitumor promotion activity in mouse skin and explored the relevant mechanisms. When 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) was applied topically to the mouse ear to induce inflammation, DIM pretreatment effectively inhibited TPA‐induced ear edema formation. To evaluate the mechanisms underlying DIM's antiinflammatory effects, DIM was topically treated to the shaved backs of mice 30 min before TPA treatment. DIM inhibited the TPA‐induced increases in the expression of cyclooxygenase (COX)‐2, inducible nitric oxide synthase (iNOS), chemokine (C‐X‐C motif) ligand (CXCL) 5, and interleukin (IL)‐6 in mouse skin. DIM also inhibited nuclear factor‐kappa B (NF‐κB)'s DNA binding activity, the nuclear translocation of p65, and the degradation of inhibitor of κB (IκB) α in TPA‐stimulated mouse skin. Furthermore, DIM reduced TPA‐induced increases in the activity of extracellular signal regulated protein kinase (ERK)‐1/2 and IκB kinase (IKK). When mouse skin papillomas were initiated via the topical application of 7,12‐dimethylbenz[α]anthracene (DMBA) and promoted with repeated topical applications of TPA, repeated topical applications of DIM prior to each TPA treatment significantly suppressed the incidence and multiplicity of the papillomas. DIM also reduced the expression of COX‐2 and iNOS, ERK phosphorylation, and the nuclear translocation of p65 in papillomas. Collectively, these results show that DIM exerts antiinflammatory and chemopreventive effects in mouse skin via the downregulation of COX‐2, iNOS, CXCL5, and IL‐6 expression, which may be mediated by reductions in NF‐κB activation. © 2010 Wiley‐Liss, Inc.     

Prepubertal exposure to cow's milk reduces susceptibility to carcinogen‐induced mammary tumorigenesis in rats

Cow's milk contains high levels of estrogens, progesterone and insulin‐like growth factor 1 (IGF‐1), all of which are associated with breast cancer. We investigated whether prepubertal milk exposure affects mammary gland development and carcinogenesis in rats. Sprague–Dawley rats were given either whole milk or tap water to drink from postnatal day (PND) 14 to PND 35, and thereafter normal tap water. Mammary tumorigenesis was induced by administering 7,12‐dimethylbenz[a]anthracene on PND 50. Milk exposure increased circulating E2 levels on PND 25 by 10‐fold (p < 0.001) and accelerated vaginal opening, which marks puberty onset, by 2.5 days (p < 0.001). However, rats exposed to milk before puberty exhibited reduced carcinogen‐induced mammary carcinogenesis; that is, their tumor latency was longer (p < 0.03) and incidence was lower (p < 0.05) than in the controls. On PND 25 and 50, mammary glands of the milk‐exposed rats had significantly less terminal end buds (TEBs) than the tap water‐exposed controls (p < 0.019). ER‐α protein levels were elevated in the TEBs and lobules of milk rats, compared to rats given tap water (p < 0.019), but no changes in cyclin D1 expression, cell proliferation or apoptosis were seen. IGF‐1 mRNA levels were reduced on PND 50 in the mammary glands of rats exposed to milk at puberty. Our results suggest that drinking milk before puberty reduces later risk of developing mammary cancer in rats. This might be mediated by a reduction in the number of TEBs and lower expression of IGF‐1 mRNA in the mammary glands of milk‐exposed animals.     

NADPH oxidase overexpression in human colon cancers and rat colon tumors induced by 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP)

NADPH oxidase/dual‐oxidase (Nox/Duox) family members have been implicated in nuclear factor kappa‐B (NFκB)‐mediated inflammation and inflammation‐associated pathologies. We sought to examine, for the first time, the role of Nox/Duox and NFκB in rats treated with the cooked meat heterocyclic amine carcinogen 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP). In the PhIP‐induced colon tumors obtained after 1 year, Nox1, Nox4, NFκB‐p50 and NFκB‐p65 were all highly overexpressed compared with their levels in adjacent normal‐looking colonic mucosa. Nox1 and Nox4 mRNA and protein levels also were markedly elevated in a panel of primary human colon cancers, compared with their matched controls. In HT29 human colon cancer cells, Nox1 knockdown induced G1 cell cycle arrest, whereas in Caco‐2 cells there was a strong apoptotic response, with increased levels of cleaved caspase‐3, ‐6, ‐7 and poly(ADP‐ribose)polymerase. Nox1 knockdown blocked lipopolysaccharide‐induced phosphorylation of IκB kinase, inhibited the nuclear translocation of NFκB (p50 and p65) proteins, and attenuated NFκB DNA binding activity. There was a corresponding reduction in the expression of downstream NFκB targets, such as MYC, CCND1 and IL1β. The results provide the first evidence for a role of Nox1, Nox4 and NFκB in PhIP‐induced colon carcinogenesis, including during the early stages before tumor onset. Collectively, the findings from this investigation and others suggest that further work is warranted on the role of Nox/Duox family members and NFκB in colon cancer development.     

Blockade of MEK signaling potentiates 5‐Aza‐2′‐deoxycytidine‐induced apoptosis and upregulation of p21waf1 in acute myelogenous leukemia cells

We have recently reported that the mitogen‐activated protein kinase/ERK kinase (MEK) inhibitor AZD6244 (ARRY‐142886) strikingly potentiated the effects of histone deacetylase inhibitor to induce growth arrest and apoptosis of acute myelogeneous leukemia (AML) cells in association with enhanced upregulation of p21^waf1. This study examined the effects of the MEK inhibitor on the action of DNA methyltransferase inhibitor 5‐Aza‐2′‐deoxycytidine (5‐AzadC), another epigenetic agent in AML cells. AZD6244 significantly potentiated the ability of 5‐AzadC to induce growth arrest and apoptosis of NB4, and freshly isolated AML cells. In parallel, 5‐AzadC induced expression of p21^waf1 in AML cells, which was potently enhanced in the presence of AZD6244. Further studies explored the molecular mechanisms by which 5‐AzadC induced expression of p21^waf1 and found that a low dose of 5‐AzadC (1 μM) induced acetylation of histone H3 on the p21^waf1 gene promoter; however, higher dose of this compound (3 or 5 μM) potently induced DNA damage as assessed by expression of γH2AX, in NB4 cells. These effects were strikingly enhanced by concomitant blockade of MEK signaling. Furthermore, knock‐down of p21^waf1 by the siRNA rescued NB4 cells from 5‐AzadC‐mediated growth inhibition. Taken together, combination of 5‐AzadC and the MEK inhibitor may be useful for treatment of individuals with a subset of AML. © 2009 UICC     

Transplantation of three tumors induced in rats by dimethylnitrosamine

Three renal tumors induced in rats by dimethylnitrosamine were serially transplanted in animals of the same strain and one of these tumors was further studied in tissue culture. Originally, these tumors exhibited the histologic characteristics of two different types of stromal nephromas. Their growth rate tended to increase with the number of passages and the percentage of takes was higher in males than in females. In the course of successive passages, the three tumors retained their sarcomatous aspect and either remained undifferentiated or underwent progressive differentiation into primitive mesenchyme, into smooth or striated muscle tissue. The epithelial component of one of these tumors persisted until the third passage; it was well delimited from the surrounding sarcomatoid tissue so that the possibility of a metaplastic transformation seems unlikely. It appears that the transplantation of these neoplasms resulted in a simplification of their structural organization and that they evolved towards a mesenchymal differentiation of the muscular type.