Phosphorylation-Mediated Activation of β-Catenin-TCF4-CEGRs/ALCDs Pathway Is an Essential Event in Development of Aggressive Hepatoblastoma

Inhibition of Histone Deacetylase Activity Increases Cisplatin Efficacy to Eliminate Metastatic Cells in Pediatric Liver Cancers

The pediatric liver cancers, hepatoblastoma and hepatocellular carcinoma, are dangerous cancers which often spread to the lungs. Although treatments with cisplatin significantly improve outcomes, cisplatin may not eliminate metastasis-initiating cells. Our group has recently shown that the metastatic microenvironments of hepatoblastoma contain Cancer Associated Fibroblasts (CAFs) and neuron-like cells, which initiate cancer spread from liver to lungs. In this study, we found that these cells express high levels of HDAC1; therefore, we examined if histone deacetylase inhibition improves cisplatin anti-proliferative effects and reduces the formation of tumor clusters in pediatric liver cancer metastatic microenvironments.

METHODS

New cell lines were generated from primary hepatoblastoma liver tumors (hbl) and lung metastases (LM) of HBL patients. In addition, cell lines were generated from hepatocellular neoplasm, not otherwise specified (HCN-NOS) tumor samples, and hcc cell lines. Hbl, LM and hcc cells were treated with cisplatin, SAHA or in combination. The effect of these drugs on the number of cells, formation of tumor clusters and HDAC1-Sp5-p21 axis were examined.

RESULTS

Both HBL and HCC tissue specimens have increased HDAC1-Sp5 pathway activation, recapitulated in cell lines generated from the tumors. HDAC inhibition with vorinostat (SAHA) increases cisplatin efficacy to eliminate CAFs in hbl and in hcc cell lines. Although the neuron-like cells survive the combined treatments, proliferation was inhibited. Notably, combining SAHA with cisplatin overcame cisplatin resistance in an LM cell line from an aggressive case with multiple metastases. Underlying mechanisms of this enhanced inhibition include suppression of the HDAC1-Sp5 pathway and elevation of an inhibitor of proliferation p21. Similar findings were found with gemcitabine treatments suggesting that elimination of proliferative CAFs cells is a key event in the inhibition of mitotic microenvironment.

CONCLUSIONS

Our studies demonstrate the synergistic benefits of HDAC inhibition and cisplatin to eliminate metastasis-initiating cells in pediatric liver cancers.

Cellular origin and molecular mechanisms of lung metastases in patients with aggressive hepatoblastoma

BACKGROUND AND AIMS

Lung metastases are the most threatening signs for patients with aggressive hepatoblastoma (HBL). Despite intensive studies, the cellular origin and molecular mechanisms of lung metastases in patients with aggressive HBL are not known. The aims of these studies were to identify metastasis-initiating cells in primary liver tumors and to determine if these cells are secreted in the blood, reach the lung, and form lung metastases.

APPROACH

We have examined mechanisms of activation of key oncogenes in primary liver tumors and lung metastases and the role of these mechanisms in the appearance of metastasis-initiating cells in patients with aggressive HBL by RNA-Seq, immunostaining, chromatin immunoprecipitation, Real-Time Quantitative Reverse Transcription PCR and western blot approaches. Using a protocol that mimics the exit of metastasis-initiating cells from tumors, we generated 16 cell lines from liver tumors and 2 lines from lung metastases of patients with HBL.

RESULTS

We found that primary HBL liver tumors have a dramatic elevation of neuron-like cells and cancer-associated fibroblasts and that these cells are released into the bloodstream of patients with HBL and found in lung metastases. In the primary liver tumors, the ph-S675-β-catenin pathway activates the expression of markers of cancer-associated fibroblasts; while the ZBTB3-SRCAP pathway activates the expression of markers of neurons via cancer-enhancing genomic regions/aggressive liver cancer domains leading to a dramatic increase of cancer-associated fibroblasts and neuron-like cells. Studies of generated metastasis-initiating cells showed that these cells proliferate rapidly, engage in intense cell-cell interactions, and form tumor clusters. The inhibition of β-catenin in HBL/lung metastases-released cells suppresses the formation of tumor clusters.

CONCLUSIONS

The inhibition of the β-catenin-cancer-enhancing genomic regions/aggressive liver cancer domains axis could be considered as a therapeutic approach to treat/prevent lung metastases in patients with HBL.

The Molecular Mechanisms Underlying Onset and Progression of Liver Cancers

Liver cancers, including hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), are deadly cancers that have risen in frequency globally and have limited curative therapeutic options [...].