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Faecal (FM) and colon mucosal associated microbiota (MAM) were studied in a model of colorectal cancer (CRC), the Apc-mutated Pirc rats, and in age-paired wt F344 rats. Principal Coordinates Analysis indicated that samples' distribution was driven by age, with samples of young rats (1 month old; without tumours) separated from older ones (11-month-old; bearing tumours). Diversity analysis showed significant differences between FM and MAM in older Pirc rats, and between MAM of both Pirc and wt rats and the tumour microbiota, enriched in Enterococcus, Escherichia/Shigella, Proteus and Bifidobacteriaceae. In young animals, Pirc FM was enriched in the genus Delftia, while wt FM was enriched in Lactobacillus and Streptococcus. Some CRC biomarkers and faecal short chain fatty acids (SCFAs) were also measured. Colon proliferation and DClK1 expression, a pro-survival mucosal marker, were higher in Pirc than in wt rats, while the mucin MUC2, was lower in Pirc rats. Branched SCFAs were higher in Pirc than in wt animals. By Spearman analysis CRC biomarkers correlated with FM (in both young and old rats) and with MAM (in young rats), suggesting a specific relationship between the gut microbiota profile and these functional mucosal parameters deserving further investigation. [ABSTRACT FROM AUTHOR]

The role of fibroblast APC mutation in carcinogenesis is not clear. Apc+/− colon fibroblasts have been previously characterized: however, little is known about their behavior at very early‐stage of colon carcinogenesis. We cultured colon mucosa fibroblasts (PCF, Apc+/−) of Pirc rats (F344/NTac‐Apcam1137) at an early stage of tumorigenesis, in absence of preneoplastic lesions, and of age‐matched wt (WCF): DNA damage levels, inflammatory phenotype and the expression of known markers of CAFs were analyzed. The latter were also assessed by microarray analysis on colon normal mucosa of Pirc and wt animals. PCF exhibited higher proliferative rates (P <.001) and delayed replicative senescence onset (P <.05) compared to WCF, along with a lower level of oxidative DNA damage (P <.05). Furthermore, a constitutively higher expression of COX‐2 and sensitivity to inflammatory stimuli was found in PCF compared to WCF (P <.05), accompanied by higher invasive capability (P <.05) and presence of cytoplasmic chromatin foci (cytoplasmic chromatin foci, P <.05). However, they neither expressed CAFs markers (α‐SMA, IL‐6) nor responded to CAFs activating stimuli (TGF‐β). Accordingly, CAFs markers and activating stimuli resulted down‐regulated in Pirc normal mucosa compared to wt, whereas DNA damage response and tolerance pathways were overexpressed. These data show for the first time that a proliferative and inflammatory phenotype characterizes Apc+/− colon fibroblasts since very early stages of colon tumorigenesis, and indicate a role of Apc mutation in driving fibroblast phenotypic alterations that could support the establishment of a protumorigenic environment. Early pharmacological targeting of these dysfunctions might impact on tumor prevention in FAP patients. What's new? Heterozygous mutations in APC represent the earliest event in sporadic colorectal carcinogenesis onset and cause familial adenomatous polyposis syndrome. However, the role of APC‐mutated fibroblasts remains unclear. Here, Apc+/‐ fibroblasts isolated from apparently‐normal colon tissue of Pirc rats showed proliferative, inflammatory features and resistance to oxidative DNA damage, although they did not show cancer‐associated fibroblast features. These data suggest that, at the very early stages of colon tumourigenesis, Apc‐mutated colon fibroblasts favour the establishment of a pro‐tumourigenic environment for pre‐neoplastic lesion development. Early pharmacological targeting of these dysfunctions might be valuable for tumour prevention in familial adenomatous polyposis patients. [ABSTRACT FROM AUTHOR]

• The comet assay in assessing genomic stability in relation to folate status and human cancer. • Impact of folate deficiency/supplementation on genomic stability in vitro , in rodents and humans. • The impact of MTHFR genotype on folate status and genomic stability in human carcinogenesis. • Adaptation of the comet assay in measuring DNA methylation and impact on diet and epigenetics. Intake of folate (vitamin B 9) is strongly inversely linked with human cancer risk, particularly colon cancer. In general, people with the highest dietary intake of folate or with high blood folate levels are at a reduced risk (approx. 25%) of developing colon cancer. Folate acts in normal cellular metabolism to maintain genomic stability through the provision of nucleotides for DNA replication and DNA repair and by regulating DNA methylation and gene expression. Folate deficiency can accelerate carcinogenesis by inducing misincorporation of uracil into DNA, by increasing DNA strand breakage, by inhibiting DNA base excision repair capacity and by inducing DNA hypomethylation and consequently aberrant gene and protein expression. Conversely, increasing folate intake may improve genomic stability. This review describes key applications of single cell gel electrophoresis (the comet assay) in assessing genomic instability (misincorporated uracil, DNA single strand breakage and DNA repair capacity) in response to folate status (deficient or supplemented) in human cells in vitro , in rodent models and in human case-control and intervention studies. It highlights an adaptation of the SCGE comet assay for measuring genome-wide and gene-specific DNA methylation in human cells and colon tissue. [ABSTRACT FROM AUTHOR]