YAP activation is an early event and a potential therapeutic target in liver cancer development.

BACKGROUND & AIMS: Although the growth suppressing Hippo pathway has been implicated in hepatocellular carcinoma (HCC) pathogenesis, it is unknown at which stage of hepatocarcinogenesis its dysregulation occurs. We investigated in rat and human preneoplastic lesions whether overexpression of the transcriptional co-activator Yes-associated protein (YAP) is an early event. METHODS: The experimental model used is the resistant-hepatocyte (R-H) rat model. Gene expression was determined by qRT-PCR or immunohistochemistry. Forward genetic experiments were performed in human HCC cells and in murine oval cells. RESULTS: All foci of preneoplastic hepatocytes, generated in rats 4weeks after diethylnitrosamine (DENA) treatment, displayed YAP accumulation. This was associated with down-regulation of the ß-TRCP ligase, known to mediate YAP degradation, and of microRNA-375, targeting YAP. YAP accumulation was paralleled by the up-regulation of its target genes. Increased YAP expression was also observed in human early dysplastic nodules and adenomas. Animal treatment with verteporfin (VP), which disrupts the formation of the YAP-TEAD complex, significantly reduced preneoplastic foci and oval cell proliferation. In vitro experiments confirmed that VP-mediated YAP inhibition impaired cell growth in HCC and oval cells; notably, oval cell transduction with wild type or active YAP conferred tumorigenic properties in vitro and in vivo. CONCLUSIONS: These results suggest that (i) YAP overexpression is an early event in rat and human liver tumourigenesis; (ii) it is critical for the clonal expansion of carcinogen-initiated hepatocytes and oval cells, and (iii) VP-induced disruption of the YAP-TEAD interaction may provide an important approach for the treatment of YAP-overexpressing cancers.

Met as a therapeutic target in HCC: facts and hopes.

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide, and its burden is expected to increase further in the next years. In spite of the advances of classical therapies, such as surgery, transplantation, use of radiofrequency and transarterial embolization, the prognosis of this neoplasm has not considerably improved over the past few years. The advent of targeted therapies and the approval of the systemic treatment of advanced HCC with the kinase inhibitor sorafenib have provided some hope for the future. Even if the molecular mechanisms responsible for the onset and progression of HCC are still largely unknown, new therapeutic targets have recently come to the spotlight. One of these targets is the tyrosine kinase receptor for the Hepatocyte Growth Factor, encoded by the MET gene, known to promote tumor growth and metastasis in many human organs. In this review we will summarize the contrasting results obtained in vitro (in HCC cell lines) and in animal experimental models and we will also try to analyze the reasons for the opposite findings, suggesting that the HGF/MET axis can have either a promoting or a suppressive role in the development of HCC. We will also reconsider the evidence of activation of this pathway in human HCCs and discuss the results of the clinical trials performed with MET inhibitors. The final purpose is to better clarify which can be the role of MET as a therapeutic target in HCC.

Rilotumumab, a mAb against human hepatocyte growth factor for the treatment of cancer.

Tyrosine kinase receptors and their ligands have become appealing candidates as molecular therapeutic agents for the treatment of cancer. Hepatocyte growth factor (HGF) and its receptor, mesenchymal-epithelial transition factor (c-Met), play a role in many human tumors, promoting cell proliferation and invasion, as well as resistance to apoptosis. Rilotumumab, being developed by Amgen Inc, is a humanized mAb directed against HGF, and is thus able to interfere with the interaction between HGF and c-Met to prevent c-Met activation. In preclinical studies, rilotumumab effectively blocked c-Met phosphorylation, inhibiting c-Met-activated downstream signaling pathways. In phase I clinical trials, rilotumumab was well tolerated at doses up to 20 mg/kg every 2 weeks. Data from preclinical studies and a phase Ib trial demonstrated that rilotumumab had an additive effect when combined with chemotherapeutic agents, leading to the initiation of several phase II trials that are enrolling patients with different tumor types to assess combinations of rilotumumab with chemotherapeutic regimens, as well as with other mAbs. Which tumor types might benefit most from treatment with rilotumumab remains to be determined, and the identification of candidate patients will be a critical issue for the further development of this drug.

Methylation analysis of the promoter F of estrogen receptor alpha gene: effects on the level of transcription on human osteoblastic cells.

In this study, the methylation status of the distal promoter F of estrogen receptor alfa (ERalpha) gene in human osteoblastic cells was investigated. The activity of this promoter is responsible for the ERalpha gene transcription in bone tissue. The methylation status of promoter F was here evaluated, for the first time, by direct sequencing of bisulfite-treated genomic DNA, at 10 CpG specific sites localized in a region of about 800 bp. An heterogeneous methylation pattern was observed. The most notable difference was found at four particular CpGs, distant from the exon F transcription start site, showing a methylation status that correlates with the expression level, being ERalpha mRNA transcription reduced in a partially methylated cells but preserved in demethylated cells. The other CpG sites, localized around the transcription start site, were always demethylated except for MG-63 cells showing the lowest level of ERalpha expression. By quantitative RT-PCR analysis we demonstrated that ERalpha gene expression was higher in primary osteoblasts than in bone-derived cells (MG-63 and SaOS-2) and in all cases the ERalpha mRNA is represented by the isoform F. The same 10 CpG sites were investigated in non-osseous cell lines and were found fully methylated in ERalpha-negative breast cancer cells (MDA-MB-231) and completely demethylated in ERalpha-positive breast cancer cells (MCF7). The overall results suggest that methylation of the CpG sites inside ERalpha gene promoter F here analyzed may contribute to ERalpha transcriptional control, directly or indirectly, influencing the tissue specific expression of the gene.