Shigella invades the human intestinal mucosa, thus causing bacillary dysentery, an acute recto-colitis responsible for lethal complications, mostly in infants and toddlers. Conversely, commensal bacteria live in a mutualistic relationship with the intestinal mucosa that is characterized by homeostatic control of innate responses, thereby contributing to tolerance to the flora. Cross-talk established between commensals and the intestinal epithelium mediate this active process, the mechanisms of which remain largely uncharacterized. Probiotics such as Lactobacillus casei belong to a subclass of these commensals that modulate mucosal innate responses and possibly display anti-inflammatory properties. We analyzed whether L. casei could attenuate the pro-inflammatory signaling induced by Shigella flexneri after invasion of the epithelial lining. Cultured epithelial cells were infected with L. casei, followed by a challenge with S. flexneri. Using macroarray DNA chips, we observed that L. casei down-regulated the transcription of a number of genes encoding pro-inflammatory effectors such as cytokines and chemokines and adherence molecules induced by invasive S. flexneri. This resulted in an anti-inflammatory effect that appeared mediated by the inhibition of the NF-κB pathway, particularly through stabilization of I-κBα. In a time-course experiment using GeneChip hybridization analysis, the expression of many genes involved in ubiquitination and proteasome processes were modulated during L. casei treatment. Thus, L. casei has developed a sophisticated means to maintain intestinal homeostasis through a process that involves manipulation of the ubiquitin/proteasome pathway upstream of I-κBα.

Hepatocellular carcinoma (HCC) is a highly malignant tumor with poor prognosis and high mortality due to a lack of effective medical treatment and apparent early stage symptoms. Understanding molecular mechanism of cancer development is crucial for HCC diagnosis, prognosis, and treatment. Recently, microRNAs have been shown to play an important role in carcinogenesis, being regulated by DNA methylation in several cases. In this study, a whole genome approach was used to identify methylation-regulated miRNAs in HCC, finally focusing on miR-129-2. MiR-129-2 methylation and reduced expression were observed in all examined HCC cell lines but not in normal liver cells and tissues. In 39 (93%) of 42 HCC, the methylation levels of miR-129-2 were significantly increased in tumor tissues compared with adjacent normal tissues. Furthermore, miR-129-2 methylation was detectable in plasma samples from HCC patients, but not in plasma samples from healthy individuals or patients with liver cirrhosis. At a cut-off value of -2.36 (log2 transformation of methylation level), it was possible to distinguish HCC from healthy and cirrhotic controls with sensitivity and specificity of 88% and 100%, respectively. This study indicates that miR-129-2 methylation is highly accurate in distinguishing HCC patients from cirrhosis patients and healthy individuals, implying its potential utility as an early diagnostic marker for HCC.