No abstract

Notch signaling, a critical pathway for tissue development, also contributes to tumorigenesis in many cancers, but its pathological function in liver cancer is not well defined. In our study, Notch1 expression and its clinicopathological parameters were evaluated in 82 human hepatocellular carcinoma (HCC) patients. Plasmid-based siNotch1 shRNA was transiently or stably transfected into metastatic HCC cells and subsequently evaluated for the effects on orthotopic liver tumor metastasis in a mouse model as well as the effects on downstream pathways. Aberrant high expression of Notch1 was significantly associated with metastatic disease parameters in HCC patients, such as tumor-node-metastasis Stages III-IV and tumor venous invasion. Knocking-down Notch1 reduced cell motility in vitro and orthotopic tumor metastasis from the liver to the lung in vivo in a mouse model. In metastatic HCC cells, abnormal expression of Notch1 was associated with increased expression of Snail1 and repressed expression of E-cadherin; the Notch1-Snail1-E-cadherin association can also be found in HCC patient tumors. Inhibition of Notch1 by shRNA abolished Snail1 expression, which further resulted in the reestablishment of repressed E-cadherin in metastatic HCC cells. Thus, abnormal Notch1 expression was strongly associated with HCC metastatic disease, which might be mediated through the Notch1-Snail1-E-cadherin pathway. Knock-down of Notch1 reversed HCC tumor metastasis in a mouse model. Therefore, these data suggest that effective targeting of Notch signaling might also inhibit tumor metastasis.Hepatocellular carcinoma (HCC) is the fifth most common cancer globally and is ranked second amongst all cancer deaths in Hong Kong. HCC is correlated with an increased likelihood of vascular invasion, metastasis and recurrence (even after surgical resection), leading to poor prognosis. 1 Metastasis, both intrahepatic and extrahepatic, is of particular concern and occurs in more than half of HCC cases. 2 The incidence of high grade HCC that metastasize to distant sites is high. 2 However, the detailed mechanisms of metastasis are yet to be revealed.The process that converts adherent epithelial cells into migratory cells to invade the extracellular matrix is called the epithelial-mesenchymal transition (EMT). This process plays fundamental roles in tissue and organ formation during embryonic development and in wound healing and tissue repair during adult life. 3,4 However, the abnormal activation of EMT programs can be disadvantageous to cancer patients. 3 EMT can allow carcinoma cells to acquire mesenchymal cell gene expression profiles and properties, 5 leading to the transformation of the cells from being coherent and displaying apicobasal polarity to become nonpolarized cells that can move through the extracellular media. This transformation enables the spread of tumor cells to distant sites. 6,7 Although EMT is considered to be the first step in the metastatic progression of migratory cancer cells, EMT has not been confirmed to exist in vivo. 3...

Our findings revealed a novel role of largazole in the treatment of liver fibrosis. Through multiple mechanisms, largazole could be a potentially effective antifibrotic agent.

Inorganic polyphosphate (polyP) plays a number of critical roles in bacterial persistence, stress, and virulence. PolyP intracellular metabolism is regulated by the polyphosphate kinase (PPK) protein families, and inhibition of PPK activity is a potential approach to disrupting polyP-dependent processes in pathogenic organisms. Here, we biochemically characterized Mycobacterium tuberculosis (MTB) PPK2 and developed DNA-based aptamers that inhibit the enzyme's catalytic activities. MTB PPK2 catalyzed polyP-dependent phosphorylation of ADP to ATP at a rate 838 times higher than the rate of polyP synthesis. Gel filtration chromatography suggested MTB PPK2 to be an octamer. DNA aptamers were isolated against MTB PPK2. Circular dichroism revealed that aptamers grouped into two distinct classes of secondary structure; G-quadruplex and non-G-quadruplex. A selected G-quadruplex aptamer was highly selective for binding to MTB PPK2 with a dissociation constant of 870 nM as determined by isothermal titration calorimetry. The binding between MTB PPK2 and the aptamer was exothermic yet primarily driven by entropy. This G-quadruplex aptamer inhibited MTB PPK2 with an IC(50) of 40 nM and exhibited noncompetitive inhibition kinetics. Mutational mechanistic analysis revealed an aptamer G-quadruplex motif is critical for enzyme inhibition. The aptamer was also tested against Vibrio cholerae PPK2, where it showed an IC(50) of 105 nM and insignificant inhibition against more distantly related Laribacter hongkongensis PPK2.