Transformation of cultured fetal rat liver cells by MDAB and phenobarbital. Morphological, biochemical and immunocytochemical characterization of cell lines

The potential role of liver stem cells in initiation of primary liver cancer

Identification of the cellular origin of primary liver cancer remains challenging. Some data point toward liver stem cells (LSCs) or liver progenitor cells (LPCs) not only as propagators of liver regeneration, but also as initiators of liver cancer. LSCs exhibit a long lifespan and strong duplicative potential upon activation and are inclined to accumulate more mutations that can be passed down to the next generations. Recent evidence shows that dysregulation of signaling pathways associated with self-renewal of LSCs can drive their aberrant proliferation and even malignant transformation. If LSCs could be proved to be an initiator of liver carcinogenesis, they would be promising for ultra-early diagnosis and targeting therapy of liver cancer. This review mainly summarizes the potential role of LSCs in the carcinogenesis of primary liver cancer.

Bioenergetic differences selectively sensitize tumorigenic liver progenitor cells to a new gold(I) compound

A hallmark of cancer cells is their ability to evade apoptosis and mitochondria play a critical role in this process. Delineating mitochondrial differences between normal and cancer cells has proven challenging due to the lack of matched cell lines. Here, we compare two matched liver progenitor cell (LPC) lines, one non-tumorigenic [p53-immortalized liver (PIL) 4] and the other tumorigenic (PIL2). Analysis of these cell lines and a p53 wild-type non-tumorigenic cell line [bipotential murine oval liver (BMOL)] revealed an increase in expression of genes encoding the antiapoptotic proteins cellular inhibitor of apoptosis protein (cIAP) 1 and yes associate protein in the PIL2 cells, which resulted in an increase in the protein encoded by these genes. PIL2 cells have higher mitochondrial membrane potential (Deltapsi(m)) compared with PIL4 and BMOL and had greater levels of reactive oxygen species, despite the fact that the mitochondrial antioxidant enzyme, manganese superoxide disumutase, was elevated at transcript and protein levels. Taken together, these results may account for the observed resistance of PIL2 cells to apoptotic stimuli compared with PIL4. We tested a new gold compound to show that hyperpolarized Deltapsi(m) led to its increased accumulation in mitochondria of PIL2 cells. This compound selectively induces apoptosis in PIL2 cells but not in PIL4 or BMOL. The gold compound depolarized the Deltapsi(m), depleted the adenosine triphosphate pool and activated caspase-3 and caspase-9, suggesting that apoptosis was mediated via mitochondria. This investigation shows that the non-tumorigenic and tumorigenic LPCs are useful models to delineate the role of mitochondrial dysfunction in tumorigenesis and for the future development of mitochondria-targeted chemotherapeutics that selectively target tumor cells.