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-ß-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 ß-catenin in HBL/lung metastases-released cells suppresses the formation of tumor clusters. CONCLUSIONS: The inhibition of the ß-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.

Genetic Ablation of C/EBPα-p300 Pathway Blocks Development of Obese Pregnancy Associated Liver Disorders in Offspring.

BACKGROUND & AIMS: The obesity-associated nonalcoholic fatty liver disease represents a common cause of pediatric liver diseases, including the pediatric liver cancer hepatoblastoma. The mechanisms behind the development of fatty liver in children are not yet known. We examined the role of the C/EBPα-p300 pathway in the development of maternal obesity-associated fatty liver phenotype in offspring. METHODS: Because the ability of C/EBPα to promote fatty liver phenotype is enhanced by CDK4-mediated phosphorylation of C/EBPα at Ser193 and subsequent formation of C/EBPα-p300 complexes, we used wild-type (WT) and C/EBPα-S193D and C/EBPα-S193A mutant mice to study the effects of maternal high-fat diet (HFD) on the liver health of offspring. The females of these mouse lines were fed an HFD before mating, and the pups were further subjected to either an HFD or a normal diet for 12 weeks. RESULTS: WT female mice on the HFD before and during pregnancy and their subsequent offspring on the HFD had severe fatty liver, fibrosis, and an increased rate of liver proliferation. However, the HFD in C/EBPα-S193A mice did not cause development of these disorders. In HFD-HFD treated WT mice, C/EBPα is phosphorylated at Ser193 and forms complexes with p300, which activate expression of genes involved in development of fatty liver, fibrosis, and proliferation. However, S193A-C/EBPα mice do not have complexes of C/EBPα-S193A with p300, leading to a lack of activation of genes of fatty liver, fibrosis, and proliferation. The mutant C/EBPα-S193D mice have accelerated cdk4-dependent pathway and have developed steatosis at early stages. CONCLUSIONS: These studies identified the epigenetic cause of obese pregnancy-associated liver diseases and suggest a potential therapy based on inhibition of cdk4-ph-S193-C/EBPα-p300 pathway.

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

BACKGROUND AND AIMS: Hepatoblastoma (HBL), a deadly malignancy in children, is the most common type of pediatric liver cancer. We recently demonstrated that ß-catenin, phosphorylated at S675 (ph-S675-ß-catenin), causes pathological alterations in fibrolamellar hepatocellular carcinoma (FLC), by activating oncogenes and fibrotic genes via human genomic regions, known as cancer-enhancing genomic regions or aggressive liver cancer domains (CEGRs/ALCDs). The aim of this study was to determine the role of the ph-S675-ß-catenin-TCF4-CEGRs/ALCDs pathway in HBL. METHODS: The ph-S675-ß-catenin-TCF4-CEGRs/ALCDs pathway was examined in a large cohort of HBL specimens, in HBL cell lines HepG2 and Huh6, and in patient-derived xenografts (PDXs). RESULTS: ß-catenin is phosphorylated at S675 in a large portion of tested HBL patients. In these patients, ph-S675-ß-catenin forms complexes with TCF4 and opens CEGRs/ALCDs-dependent oncogenes for transcription, leading to a massive overexpression of the oncogenes. The inhibition of the ß-catenin-TCF4-CEGRs/ALCDs axis inhibits the proliferation of cancer cells and tumor growth in HBL cell lines and HBL-PDXs. The ph-S675-ß-catenin is abundant in mitotic cells. We found that markers of HBL Glypican 3 (GPC3) and Alpha Fetoprotein (AFP) are increased in HBL patients by ß-catenin-TCF4-p300 complexes. CONCLUSIONS: The phosphorylation-mediated activation of the ß-catenin-TCF4-p300-CEGRs/ALCDs pathway increases oncogene expression in patients with aggressive liver cancer and promotes the development of hepatoblastoma.

ß-catenin cancer-enhancing genomic regions axis is involved in the development of fibrolamellar hepatocellular carcinoma.

Fibrolamellar hepatocellular carcinoma (FLC) is a disease that occurs in children and young adults. The development of FLC is associated with creation of a fusion oncoprotein DNAJB1-PKAc kinase, which activates multiple cancer-associated pathways. The aim of this study was to examine the role of human genomic regions, called cancer-enhancing genomic regions or aggressive liver cancer domains (CEGRs/ALCDs), in the development of FLC. Previous studies revealed that CEGRs/ALCDs are located in multiple oncogenes and cancer-associated genes, regularly silenced in normal tissues. Using the regulatory element locus intersection (RELI) algorithm, we searched a large compendium of chromatin immunoprecipitation-sequencing (ChIP) data sets and found that CEGRs/ALCDs contain regulatory elements in several human cancers outside of pediatric hepatic neoplasms. The RELI algorithm further identified components of the ß-catenin-TCF7L2/TCF4 pathway, which interacts with CEGRs/ALCDs in several human cancers. Particularly, the RELI algorithm found interactions of transcription factors and chromatin remodelers with many genes that are activated in patients with FLC. We found that these FLC-specific genes contain CEGRs/ALCDs, and that the driver of FLC, fusion oncoprotein DNAJB1-PKAc, phosphorylates ß-catenin at Ser675, resulting in an increase of ß-catenin-TCF7L2/TCF4 complexes. These complexes increase a large family of CEGR/ALCD-dependent collagens and oncogenes. The DNAJB1-PKAc-ß-catenin-CEGR/ALCD pathway is preserved in lung metastasis. The inhibition of ß-catenin in FLC organoids inhibited the expression of CEGRs/ALCDs-dependent collagens and oncogenes, preventing the formation of the organoid's structure. Conclusion: This study provides a rationale for the development of ß-catenin-based therapy for patients with FLC.

HDAC1-Dependent Repression of Markers of Hepatocytes and P21 Is Involved in Development of Pediatric Liver Cancer.

BACKGROUND & AIMS: Epigenetic regulation of gene expression plays a critical role in the development of liver cancer; however, the molecular mechanisms of epigenetic-driven liver cancers are not well understood. The aims of this study were to examine molecular mechanisms that cause the dedifferentiation of hepatocytes into cancer cells in aggressive hepatoblastoma and test if the inhibition of these mechanisms inhibits tumor growth. METHODS: We have analyzed CCAAT/Enhancer Binding Protein alpha (C/EBPα), Transcription factor Sp5, and histone deacetylase (HDAC)1 pathways from a large biobank of fresh hepatoblastoma (HBL) samples using high-pressure liquid chromatography-based examination of protein-protein complexes and have examined chromatin remodeling on the promoters of markers of hepatocytes and p21. The HDAC1 activity was inhibited in patient-derived xenograft models of HBL and in cultured hepatoblastoma cells and expression of HDAC1-dependent markers of hepatocytes was examined. RESULTS: Analyses of a biobank showed that a significant portion of HBL patients have increased levels of an oncogenic de-phosphorylated-S190-C/EBPα, Sp5, and HDAC1 compared with amounts of these proteins in adjacent regions. We found that the oncogenic de-phosphorylated-S190-C/EBPα is created in aggressive HBL by protein phosphatase 2A, which is increased within the nucleus and dephosphorylates C/EBPα at Ser190. C/EBPα-HDAC1 and Sp5-HDAC1 complexes are abundant in hepatocytes, which dedifferentiate into cancer cells. Studies in HBL cells have shown that C/EBPα-HDAC1 and Sp5-HDAC1 complexes reduce markers of hepatocytes and p21 via repression of their promoters. Pharmacologic inhibition of C/EBPα-HDAC1 and Sp5-HDAC1 complexes by Suberoylanilide hydroxamic acid (SAHA) and small interfering RNA-mediated inhibition of HDAC1 increase expression of hepatocyte markers, p21, and inhibit proliferation of cancer cells. CONCLUSIONS: HDAC1-mediated repression of markers of hepatocytes is an essential step for the development of HBL, providing background for generation of therapies for aggressive HBL by targeting HDAC1 activities.

Olaparib Inhibits Tumor Growth of Hepatoblastoma in Patient-Derived Xenograft Models.

BACKGROUND AND AIMS: Hepatoblastoma (HBL) is a devastating pediatric liver cancer with multiple treatment options, but it ultimately requires surgery for a cure. The most malicious form of HBL is a chemo-resistant aggressive tumor that is characterized by rapid growth, metastases, and poor response to treatment. Very little is known of the mechanisms of aggressive HBL, and recent focuses have been on developing alternative treatment strategies. In this study, we examined the role of human chromosomal regions, called aggressive liver cancer domains (ALCDs), in liver cancer and evaluated the mechanisms that activate ALCDs in aggressive HBL. RESULTS: We found that ALCDs are critical regions of the human genome that are located on all human chromosomes, preferentially in intronic regions of the oncogenes and other cancer-associated genes. In aggressive HBL and in patients with Hepatocellular (HCC), JNK1/2 phosphorylates p53 at Ser6, which leads to the ph-S6-p53 interacting with and delivering the poly(adenosine diphosphate ribose) polymerase 1 (PARP1)/Ku70 complexes on the oncogenes containing ALCDs. The ph-S6-p53-PARP1 complexes open chromatin around ALCDs and activate multiple oncogenic pathways. We found that the inhibition of PARP1 in patient-derived xenografts (PDXs) from aggressive HBL by the Food and Drug Administration (FDA)-approved inhibitor olaparib (Ola) significantly inhibits tumor growth. Additionally, this is associated with the reduction of the ph-S6-p53/PARP1 complexes and subsequent inhibition of ALCD-dependent oncogenes. Studies in cultured cancer cells confirmed that the Ola-mediated inhibition of the ph-S6-p53-PARP1-ALCD axis inhibits proliferation of cancer cells. CONCLUSIONS: In this study, we showed that aggressive HBL is moderated by ALCDs, which are activated by the ph-S6-p53/PARP1 pathway. By using the PARP1 inhibitor Ola, we suppressed tumor growth in HBL-PDX models, which demonstrated its utility in future clinical models.

Small Molecule Cjoc42 Improves Chemo-Sensitivity and Increases Levels of Tumor Suppressor Proteins in Hepatoblastoma Cells and in Mice by Inhibiting Oncogene Gankyrin.

Objective: Relapsed hepatoblastoma (HBL) and upfront hepatocellular carcinoma (HCC) are notoriously chemoresistant tumors associated with poor outcomes. Gankyrin (Gank) is a known oncogene that is overexpressed in pediatric liver cancer and implicated in chemo-resistance. The goal of this study was to evaluate if the Gank-tumor suppressor axis is activated in chemoresistant hepatoblastoma patients and examine if an inhibitor of Gank, Cjoc42, might improve the chemosensitivity of cancer cells. Methods: Expression of Gank and its downstream targets were examined in fresh human HBL samples using immunostaining, QRT-PCR, and Western Blot. Cancer cells, Huh6 (human HBL) and Hepa1c1c7 (mouse HCC) were treated with Cjoc42 and with Cjoc42 in combination with cisplatin or doxorubicin. Cell proliferation, apoptosis, and chemoresistance were examined. To examine activities of Cjoc42 in vivo, mice were treated with different doses of Cjoc42, and biological activities of Gank and cytotoxicity of Cjoc42 were tested. Results: Elevation of Gank and Gank-mediated elimination of TSPs are observed in patients with minimal necrosis after chemotherapy and relapsed disease. The treatment of Huh6 and Hepa1c1c7 with Cjoc42 was not cytotoxic; however, in combination with cisplatin or doxorubicin, Cjoc42 caused a significant increase in cytotoxicity compared to chemotherapy alone with increased apoptosis. Examination of Cjoc42 in WT mice showed that Cjoc42 is well tolerated without systemic toxicity, and levels of tumor suppressors CUGBP1, Rb, p53, C/EBPα, and HNF4α are increased by blocking their Gank-dependent degradation. Conclusions: Our work shows that Cjoc42 might be a promising adjunct to chemotherapy for the treatment of severe pediatric liver cancer and presents mechanisms by which Cjoc42 increases chemo-sensitivity.