DNA of Helicobacter spp. and common gut bacteria in primary liver carcinoma

Background and aim. Gastric and enteric Helicobacter species have been associated with the pathogenesis of some extragastric diseases. Methods. We retrospectively investigated the presence of DNA of Helicobacter species in samples of the cancer and the surrounding tumour-free liver tissues of patients with hepatocellular carcinoma (HCC, n = 12) and cholangiocarcinoma (CC, n = 13). The patients were from an area with low liver cancer incidence and with low hepatitis B and C prevalence. Patients with a benign liver disease (n = 24) were included as controls. Paraffin-embedded liver samples were examined by a Helicobacter genus-specific PCR assay as well as group-specific PCR assays for Enterobacteriaceae, Bacteroides, Lactobacillus and Enterococcus. PCR products of positive samples were characterised by denaturing gradient gel electrophoresis (DGGE) and DNA sequencing. Results. PCR assay detected Helicobacter DNA in seven of 12 (58%) and eight of 13 (62%) normal liver tissue specimens from HCC and CC patients, respectively. Two cancer samples from HCC patients were Helicobacter-positive but none of the CC cancers. In the control group, three of 24 (12.5%) patients with a benign liver condition were positive for Helicobacter species (p < 0.01 compared to results of tumour-free liver tissue from the cancer patients). DGGE and DNA sequence analysis showed that 90% of the detected PCR products were "H. pylori-like". DNA of some other enteric bacteria was detected in the liver of one cancer patient and one control (4% of all patients). Conclusion. The presence of DNA of Helicobacter species in liver specimens, but not of other common gut bacteria, was associated with human hepatic carcinogenesis. (c) 2007 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.