Background and purpose Severe diarrhoea, a common gastrointestinal manifestation of anticancer treatment with irinotecan, might involve single nucleotide polymorphisms (SNPs) of toll‐like receptors (TLRs), described as critical bacterial sensors in the gut. Here, colorectal cancer patients carrying missense TLR4 A896G (rs4986790) or C1,196T (rs4986791) SNPs and Tlr4 knockout (Tlr4−/−) mice were given irinotecan to investigate the severity of the induced diarrhoea. Experimental approach Forty‐six patients treated with irinotecan‐based regimens had diarrhoea severity analysed according to TLR4 genotypes. In the experimental setting, wild‐type (WT) or Tlr4−/− mice were given irinotecan (45 or 75 mg·kg−1, i.p.) or saline (3 ml·kg−1). Diarrhoea severity was evaluated by measuring intestinal injury and inflammatory markers expression after animals were killed. Key results All patients with TLR4 SNPs chemotherapy‐treated presented diarrhoea, whereas gastrointestinal toxicity was observed in 50% of the wild homozygous individuals. Mice injected with irinotecan presented systemic bacterial translocation and increased TLR4 immunostaining in the intestine. In line with the clinical findings, Tlr4 gene deficiency enhanced irinotecan‐related diarrhoea and TLR9 expression in mice. An increased myeloperoxidase activity and Il‐18 expression along with IL‐10 decreased production in Tlr4−/− mice also indicated an intensified intestinal damage and inflammatory response. Conclusion and implications TLR4 deficiency upregulates TLR9 expression and enhances intestinal damage and the severity of late‐onset diarrhoea during irinotecan‐based treatment. Identifying patients genetically predisposed to chemotherapy‐associated diarrhoea is a strategy toward precision medicine.

ObjectiveA relation between transfusional IOL (iron overload), HFE status and oxidative damage was evaluated.Design, setting and participantsAn observational cross-sectional study involving 87 healthy individuals and 78 patients with myelodysplastic syndromes (MDS) with and without IOL, seen at University Hospital of the Federal University of Ceará, Brazil, between May 2010 and September 2011.MethodsIOL was defined using repeated measures of serum ferritin ≥1000 ng/mL. Variations in the HFE gene were investigated using PCR/restriction fragment length polymorphism (RFLP). The biomarkers of oxidative stress (plasmatic malonaldehyde (MDA), glutathione peroxidase (GPx) and superoxide dismutase (SOD)) were determined by spectrophotometry.ResultsThe HFE gene variations were identified in 24 patients (30.77%) and 5 volunteers (5.74%). The H63D variant was observed in 35% and the C282Y variant as heterozygous in 5% of patients with MDS with IOL. One patient showed double heterozygous variant (C282Y/H63D) and serum ferritin of 11 649 ng/mL. In patients without IOL, the H63D variant was detected in 29.34%. Serum MDA levels were highest in patients with MDS with IOL, with a significant difference when compared with patients without IOL and healthy volunteers, pointing to the relationship between IOL and oxidative stress. The GPx and SOD were also significantly higher in these patients, indicating that lipid peroxidation increase was followed by an increase in antioxidant capacity. Higher ferritin levels were observed in patients with HFE gene variation. 95.7% of patients with MDS with the presence of HFE gene variations had received more of 20 transfusions.ConclusionsWe observed a significant increase in MDA levels in patients with MDS and IOL, suggesting an increased lipid peroxidation in these patients. The accumulation of MDA alters the organisation of membrane phospholipids, contributing to the process of cellular degeneration. Results show that excess iron intensifies the process of cell damage through oxidative stress.Trial registration numberLocal Ethics Committee (licence 150/2009).

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Some studies show that alterations in DNA repair genes polymorphisms are associated with the pathogenesis and susceptibility of Myelodysplastic Syndrome (MDS). We genotyped 60 MDS patients for six DNA repair gene polymorphisms: BRCA1 rs4793191, BRCA2 rs9567623, RAD51 rs1801320, XRCC5 rs3835, XRCC6 rs2267437 and LIG4 rs1805388. The G/C heterozygote genotype of rs1801320 polymorphism was associated with a decreased chance of developing MDS (p = 0.05). Additionally, the G/G homozygous genotype was associated with the presence of one cytopenia in whole blood. The genotype C/G and CG + GG of the rs2267437 polymorphism was associated with normal karyotype (p = 0.010) and bone marrow cellularity normocellular + hypercellular (p = 0.023). We found that the A/G heterozygous genotype of the rs3835 polymorphism is associated with decreased chance of developing MDS (p < 0.001). These results support the importance of RAD51, XRCC5 and XRCC6 genes polymorphisms in the maintenance of genomic stability promoting a better understanding of the genesis and etiology of MDS.

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