NOD2, a protein associated with susceptibility to Crohn's disease, confers responsiveness to bacterial preparations of lipopolysaccharide and peptidoglycan, but the precise moiety recognized remains elusive. Biochemical and functional analyses identified muramyl dipeptide (MurNAc-L-Ala-D-isoGln) derived from peptidoglycan as the essential structure in bacteria recognized by NOD2. Replacement of L-Ala for D-Ala or DisoGln for L-isoGln eliminated the ability of muramyl dipeptide to stimulate NOD2, indicating stereoselective recognition. Muramyl dipeptide was recognized by NOD2 but not by TLR2 or co-expression of TLR2 with TLR1 or TLR6. NOD2 mutants associated with susceptibility to Crohn's disease were deficient in their recognition of muramyl dipeptide. Notably, peripheral blood mononuclear cells from individuals homozygous for the major disease-associated L1007fsinsC NOD2 mutation responded to lipopolysaccharide but not to synthetic muramyl dipeptide. Thus, NOD2 mediates the host response to bacterial muropeptides derived from peptidoglycan, an activity that is important for protection against Crohn's disease. Because muramyl dipeptide is the essential structure of peptidoglycan required for adjuvant activity, these results also have implications for understanding adjuvant function and effective vaccine development.

Staging systems are key to predict the prognosis of patients with cancer, to stratify the patients according to prognostic variables in the setting of clinical trials, to allow the exchange of information among researchers, and finally to guide the therapeutic approach. The current knowledge of the disease, however, prevents recommendation of a staging system that can be used world-wide. The conventional staging systems for hepatocellular carcinoma (HCC), such as the Okuda stage or the TNM stage have shown important limitations in classifying patients. Several new systems have been proposed recently, and only three of them have been validated at this point. The BCLC staging classification links the stage of the disease to a specific treatment strategy. The JIS score has been proposed and used in Japan, although it needs Western validation. The CLIP score is used in patients with advanced tumors. Several reasons explain the difficulty in identifying a world-wide system. First, HCC is a complex neoplasm inserted on a pre-neoplastic cirrhotic liver, and thus variables of both diseases leading to death should be taken into account. Second, the disease is very heterogeneous around the world, and this reflects different underlying epidemiological backgrounds and risk factors. Third, HCC is the sole cancer treated by transplantation in a small proportion of patients. Fourth, only around 20% of the cases are currently treated by surgery, thus precluding the wide use of pathology-based systems, such as TNM. Finally, the potential relevance of a molecular signature identified in terms of outcome prediction is unknown, and further research is needed to obtain this valuable biological information that may aid in classifying the patients.

Surgical resection and liver transplantation offer a 5-year survival greater than 70% in patients with hepatocellular carcinoma, but the high recurrence rate impairs long-term outcome after resection. Pathological data such as vascular invasion and detection of additional nodules predict recurrence and divide patients into high and low risk profile. Based on this, we proposed salvage liver transplant to resected patients in whom pathology evidenced high recurrence risk even in the absence of proven residual disease. From January 1995 to August 2003 we have evaluated 1,638 patients. Resection was indicated in 77 patients, but only 17 (22%) (all cirrhotics, 14 hepatitis C virus؉) were optimal candidates for both resection and transplantation. Of them, 8 exhibited a high risk profile at pathology and were offered transplantation. Among the 8 high risk patients, 7 presented recurrence, compared with only 2 of the 9 at low risk (P ‫؍‬ .012). Two of the high risk patients refused transplant and developed multifocal disease during follow-up. The other 6 were enlisted and all but 1 had tumor foci in the explant. Only 1 presented extrahepatic dissemination early after transplant and died 4 months later. The others are free of disease after a median follow-up of 45 months. Two recurrences were detected in low risk patients, 1 of them being transplanted 18 months after surgery. These data in a small series of patients confirm that pathological parameters identify patients at higher risk of recurrence, which allow them to be listed for liver transplantation without proven malignant disease. In conclusion, this policy is clinically effective and could further improve the outcome of resected patients.