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Increased polyamine intake inhibits age-associated alteration in global DNA methylation and 1,2-dimethylhydrazine-induced tumorigenesis.

ABSTRACT: Polyamines (spermine and spermidine) play many important roles in cellular function and are supplied from the intestinal lumen. We have shown that continuous high polyamine intake inhibits age-associated pathologies in mice. The mechanism by which polyamines elicit these effects was examined. Twenty-four week old Jc1:ICR male mice were fed one of three experimental chows containing different polyamine concentrations. Lifetime intake of high polyamine chow, which had a polyamine content approximately three times higher than regular chow, elevated polyamine concentrations in whole blood, suppressed age-associated increases in pro-inflammatory status, decreased age-associated pathological changes, inhibited age-associated global alteration in DNA methylation status and reduced the mortality in aged mice. Exogenous spermine augmented DNA methyltransferase activity in Jurkat and HT-29 cells and inhibited polyamine deficiency-induced global alteration in DNA methylation status in vitro. In addition, increased polyamine intake was associated with a decreased incidence of colon tumors in BALB/c mice after 1,2-demethylhydrazine administration; 12 mice (60%) in the low polyamine group developed tumors, compared with only 5 mice (25%) in the high polyamine group (Fisher's exact probability = 0.027, p = 0.025). However, increased polyamine intake accelerated the growth of established tumors; maximal tumor diameter in the Low and High groups was 3.85±0.90 mm and 5.50±1.93 mm, respectively (Mann-Whitney test, p = 0.039). Spermine seems to play important roles in inhibiting age-associated and polyamine-deficient induced abnormal gene methylation as well as pathological changes including tumorigenesis.

SUBMITTER: Soda K

PROVIDER: S-EPMC3655973 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundEpigallocatechin gallate (EGCG) is a polyhydroxy phenolic compound extracted from tea and its antitumor effect has received widespread attention. We explored the inhibitory effect of EGCG on dimethylhydrazine (DMH)-induced colorectal cancer (CRC) using a rat model, predicted the interaction between EGCG and CRC target genes using a database, and explained the EGCG associated target pathways and mechanisms in CRC.AimTo understand the inhibitory mechanisms of EGCG on CRC cell proliferation and identify its pharmacological targets by network pharmacology analysis.MethodsDMH (40 mg/kg, s.c., twice weekly for eight weeks) was used to induce CRC in rats. After model establishment, the rats were administered with EGCG (50, 100, or 200 mg/kg, p.o., once daily for eight weeks) and killed 12 and 20 wk after the start of the experiment. Formation of aberrant crypt foci and tumor was studied by histological analysis. Using network pharmacology analysis, candidate and collective targets of EGCG and CRC were identified, and Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes analyses were used to predict the pathways altered by EGCG.ResultsAt week 12, high-dose EGCG treatment significantly reduced the tumor formation rate, total number of tumors, cancerous and non-cancerous tumors, tumor volume, ascites formation, and aberrant crypt foci count. At week 20, all three doses of EGCG were effective. Seventy-eight collective targets of EGCG and CRC were identified, of which 28 genes were dysregulated in CRC. Kyoto Encyclopedia of Genes and Genomes and GO analyses showed that the dysregulated genes were enriched in hsa05210 (CRC), hsa04115 (p53 signaling pathway), and hsa04151 (PI3K-Akt signaling pathway), GO:0043124 (negative regulation of I-kappaB kinase/NF-kappaB signaling pathway), GO:0043409 (negative regulation of mitogen-activated protein kinase cascade), and GO:2001244 (positive regulation of intrinsic apoptotic signaling pathway) respectively.ConclusionEGCG inhibits the formation of DMH-induced CRC by regulating key pathways involved in tumorigenesis.

Project description:BackgroundAzoxymethane (AOM) or 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis in rats shares many phenotypical similarities with human sporadic colon cancer and is a reliable model for identifying chemopreventive agents. Genetic mutations relevant to human colon cancer have been described in this model, but comprehensive gene expression and genomic analysis have not been reported so far. Therefore, we applied genome-wide technologies to study variations in gene expression and genomic alterations in DMH-induced colon cancer in F344 rats.MethodsFor gene expression analysis, 9 tumours (TUM) and their paired normal mucosa (NM) were hybridized on 4 x 44K Whole rat arrays (Agilent) and selected genes were validated by semi-quantitative RT-PCR. Functional analysis on microarray data was performed by GenMAPP/MappFinder analysis. Array-comparative genomic hybridization (a-CGH) was performed on 10 paired TUM-NM samples hybridized on Rat genome arrays 2 x 105K (Agilent) and the results were analyzed by CGH Analytics (Agilent).ResultsMicroarray gene expression analysis showed that Defcr4, Igfbp5, Mmp7, Nos2, S100A8 and S100A9 were among the most up-regulated genes in tumours (Fold Change (FC) compared with NM: 183, 48, 39, 38, 36 and 32, respectively), while Slc26a3, Mptx, Retlna and Muc2 were strongly down-regulated (FC: -500; -376, -167, -79, respectively). Functional analysis showed that pathways controlling cell cycle, protein synthesis, matrix metalloproteinases, TNFalpha/NFkB, and inflammatory responses were up-regulated in tumours, while Krebs cycle, the electron transport chain, and fatty acid beta oxidation were down-regulated. a-CGH analysis showed that four TUM out of ten had one or two chromosomal aberrations. Importantly, one sample showed a deletion on chromosome 18 including Apc.ConclusionThe results showed complex gene expression alterations in adenocarcinomas encompassing many altered pathways. While a-CGH analysis showed a low degree of genomic imbalance, it is interesting to note that one of the alterations concerned Apc, a key gene in colorectal carcinogenesis. The fact that many of the molecular alterations described in this study are documented in human colon tumours confirms the relevance of DMH-induced cancers as a powerful tool for the study of colon carcinogenesis and chemoprevention.

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Increased polyamine intake inhibits age-associated alteration in global DNA methylation and 1,2-dimethylhydrazine-induced tumorigenesis.

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