Background: Liver resection represents the first choice of treatment for primary and secondary liver malignancies, offering the patient the best chance of long-term survival. The extensive use of major hepatectomy increases the risk of post-hepatectomy liver failure (PHLF), which is associated with a high frequency of postoperative complications, mortality and increased length of hospital stay. Aims: The aim of this review is to investigate the different risk factors related to the occurrence of PHLF and to identify the limits for a safe liver resection in patients with normal liver and injured liver (cirrhosis, cholestasis, steatosis and post-chemotherapy liver injury). Methods: A literature search was undertaken in PubMed and related search engines, looking for articles relating to hepatic failure following hepatectomy in normal liver or injured liver. Results: In spite of improvements in surgical and postoperative management, the parameters determining how much liver can be resected are still largely undefined. A number of preoperative, intraoperative and postoperative factors all contribute to the likelihood of liver failure after surgery. The safe limits for liver resection can be estimated from the data of the literature for patients with normal liver and for those with different types of liver injury. Conclusions: Preoperative assessment that includes evaluation of liver volume and function of the remnant liver is a mandatory prerequisite before major hepatectomy. The critical residual liver volume for patients able to predict PHLF is mainly related to the presence of pre-existing liver disease and liver function. Among patients with normal liver, the limit for safe resection ranges from 20 to 30% future remnant liver of total liver volume. In patients with injured liver (cirrhosis, cholestasis or steatosis), preoperative assessment of the risk of PHLF should include future remnant liver volumetry and accurate liver function evaluation, including different dynamic liver function tests.

Alcohol is a well-known risk factor for hepatocellular carcinoma (HCC), but the mechanisms underlying the alcohol-related hepatocarcinogenesis are still poorly understood. Alcohol alters the provision of methyl groups within the hepatic one-carbon metabolism, possibly inducing aberrant DNA methylation. Whether specific pathways are epigenetically regulated in alcohol-associated HCC is, however, unknown. The aim of the present study was to investigate the genome-wide promoter DNA methylation and gene expression profiles in non-viral, alcohol-associated HCC. From eight HCC patients undergoing curative surgery, array-based DNA methylation and gene expression data of all annotated genes were analyzed by comparing HCC tissue and homologous cancer-free liver tissue. After merging the DNA methylation with gene expression data, we identified 159 hypermethylated-repressed, 30 hypomethylated-induced, 49 hypermethylated-induced, and 56 hypomethylated-repressed genes. Notably, promoter DNA methylation emerged as a novel regulatory mechanism for the transcriptional repression of genes controlling the retinol metabolism (ADH1A, ADH1B, ADH6, CYP3A43, CYP4A22, RDH16), iron homeostasis (HAMP), one-carbon metabolism (SHMT1), and genes with a putative, newly identified function as tumor suppressors (FAM107A, IGFALS, MT1G, MT1H, RNF180). A genome-wide DNA methylation approach merged with array-based gene expression profiles allowed identifying a number of novel, epigenetically regulated candidate tumor-suppressor genes in alcohol-associated hepatocarcinogenesis. Retinol metabolism genes and SHMT1 are also epigenetically regulated through promoter DNA methylation in alcohol-associated HCC. Due to the reversibility of epigenetic mechanisms by environmental/nutritional factors, these findings may open up to novel interventional strategies for hepatocarcinogenesis prevention in HCC related to alcohol, a modifiable dietary component.

In addition to DNA methylation, hydroxymethylation of DNA is recognized as a novel epigenetic mark. Primary liver cancers, i.e., hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC), are highly prevalent but epigenetically poorly characterized, so far. In the present study we measured global methylcytosine (mCyt) and hydroxymethylcytosine (hmCyt) in HCC and CC tissues and in peripheral blood mononuclear cell (PBMC) DNA to define mCyt and hmCyt status and, accordingly, the survival rate. Both mCyt and hmCyt were measured by a liquid chromatography/tandem mass spectrometry method in neoplastic and homologous nonneoplastic tissues, i.e., liver and gallbladder, and in PBMCs of 31 HCC and 16 CC patients. Content of mCyt was notably lower in HCC than in CC tissues (3.97% versus 5.26%, respectively; P < 0.0001). Significantly reduced mCyt was also detected in HCC compared to nonneoplastic tissue (3.97% versus 4.82% mCyt, respectively; P < 0.0001), but no such difference was found for CC versus homologous nonneoplastic tissue. Hydroxymethylation was significantly decreased in HCC versus nonneoplastic liver tissue (0.044 versus 0.128, respectively; P < 0.0001) and in CC versus both liver and gallbladder nonneoplastic tissue (0.030 versus 0.124, P = 0.026, and 0.030 versus 0.123, P = 0.006, respectively). When the survival rate was evaluated according to mCyt PBMC content by Kaplan‐Meier analysis, patients with mCyt ≥5.59% had a significantly higher life expectancy than those with mCyt <5.59% (P = 0.034) at a follow‐up period up to 48 months. Conclusion: A significant DNA hypomethylation distinguishes HCC from CC, while DNA hypo‐hydroxymethylation characterizes both HCC and CC, and a PBMC DNA mCyt content ≥5.59% relates to a favorable outcome in primary liver cancers. (Hepatology 2015;62:496–504