Specific association between alcohol intake, high grade of differentiation and 4q34-q35 deletions in hepatocellular carcinomas identified by high resolution allelotyping

One of the most frequent deletions in hepatocellular carcinoma (HCC) is that involving the long arm of chromosome 4 (30 to 70% of the cases). These chromosomal deletions are closely related to hepatitis B virus (HBV) infection. A tumor suppressor gene (TSG) located on 4q has been proposed in liver carcinogenesis, but has not been identified as yet. Despite previous LOH studies focused on 4q in HCC, a clear minimal common region of deletion (MCRD) could not be delimited. To further investigate the role of chromosome 4q LOH in the pathogenesis of HCC, 85 microsatellite markers spanning chromosome 4q were systematically analysed in a series of 154 well-characterized primary liver tumors. In 59 tumors (38%), LOHs were observed for at least two adjacent markers. Analysis of 31 tumors demonstrating a partial or interstitial 4q deletion allowed to define three MCRDs of 15, 9 and 8 Mb at the 4q22, 4q34 and 4q35 regions, respectively. Seven putative candidate genes located in 4q22, DAPP1, BMPR1B, PKD2, HERC3, SMARCAD1, CEB1 and ENH were screened for mutations but no somatic alterations were identified. Search for relationships between the specific regions of deletion and clinical parameters showed a significant association between loss of the 4q34-35 region with alcohol intake (P=0.005) and with high grade of differentiation (P=0.02). These results are in contrast with the close association between HBV infection and the whole 4q LOH and reveal heterogeneity of 4q LOH in relation to different risk factors. In the light of these new findings, which link different 4q LOH regions to different etiologic factors, the molecular mechanisms underlying 4q deletions in HCC and the targeted gene(s) remain to be identified.