4, 5 SSeCKS, the rodent ortholog of AKAP12, has been demonstrated to act as tumor suppressor in vitro and in vivo.6, 7 This function was also described in human solid neoplasms, such as prostate and gastric cancer,7, 8 but data concerning the role of AKAP12 in human hepatocarcinogenesis are scarce. The AKAP12 gene locus in human and rodents encodes three major transcripts under the control of three independent promoters, designated α, β, and γ (Fig. 1). The two major protein isoforms of AKAP12, α and β, are expressed ubiquitously in most cell and tissue types, whereas the expression of isoform γ is restricted to testes.9 The proteins translated from each transcript are

encoded by selleck inhibitor a single large exon and share >95% amino acid sequence homology; however, they differ in their N-terminal domains. These isoforms are frequently posttranslationally modified; for example, only the α isoform is myristoylated at the N-terminus, a modification that facilitates AKAP12α association with plasma membranes and vesicles of the endoplasmic reticulum.9 In one of our recent Selleckchem VX809 studies analyzing 63 HCCs by aCGH, the AKAP12 gene locus on chromosome 6q24-25.2 showed chromosomal losses in 36% (23/63) of all analyzed cases, whereas gains were observed

only in 5% (3/63).10 Yet this is an incomplete explanation of the observed AKAP12 down-regulation in HCC. Here, we show protein expression data of the tumor suppressor AKAP12 in a large series of human liver specimens, containing typical pathohistological features of hepatocarcinogenesis. In order to elucidate mechanisms

of AKAP12 down-regulation, we have analyzed genetic, epigenetic, and posttranscriptional mechanisms. In summary, we here propose three different mechanisms of AKAP12 down-regulation in hepatocarcinogenesis: microRNA (miRNA) interference in preneoplastic lesions, genetic alterations, and AKAP12α promoter hypermethylation in HCCs. aCGH, array-based comparative genomic hybridization; AKAP12, a kinase anchor protein 12; 5-aza-dC, 5-aza-2′deoxycytidine; CL, cirrhotic liver; DN, dysplastic nodule; FFPE, formalin-fixed paraffin-embedded; HCC, hepatocellular carcinoma; HBV, hepatitis B virus; HCV, hepatitis C virus; miRNA, microRNA; NL, normal liver; PCR, polymerase chain reaction; PHH, primary Progesterone human hepatocytes; PT, noncirrhotic peritumorous tissue; SSeCKS, Src-suppressed C kinase substrate; TMA, tissue microarray; UTR, untranslated region. A total of 388 human liver tissue samples were evaluated by tissue microarrays (TMAs). TMA#1 (n = 225) contained two representative areas (diameter: 0.6 mm) of 14 histologically normal liver (NL), 38 dysplastic nodule (DN), 135 hepatocellular carcinoma (HCC; grading: 29 × G1, 76 × G2, 30 × G3), 14 cirrhotic (CL), and 24 noncirrhotic peritumorous (PT) liver tissue samples. The independently designed, processed, and evaluated TMA#2 (n = 163) contained two representative areas (diameter: 0.