Abstract 3089: YAP and TAZ induce MCM protein expression to facilitate tumor-supporting properties in liver cancer

Overexpression and nuclear enrichment of the Hippo pathway-regulated transcriptional co-activator Yes-Associated Protein (YAP) is frequently detected in human hepatocellular carcinoma (HCC) and correlates with poor clinical outcome of cancer patients1. In mice, inducible overexpression of the constitutively active isoform YAPS127A induces hepatocellular proliferation leading to hepatomegaly followed by tumor formation within 12-15 weeks. How oncogenic YAP and its paralogue TAZ (syn. WWTR1, WW Domain Containing Transcription Regulator 1) induce uncontrolled proliferation in liver cells is not known, yet. Analysis of expression profiling data, derived from human liver cancer cells after siRNA-mediated inhibition of endogenous YAP, revealed that the Minichromosome Maintenance (MCMs) family members MCM2-7 were positively regulated. MCMs are key components of the pre-replication complex and involved in the formation of the replication fork, which is essential for efficient DNA duplication followed by mitosis2. We confirmed that silencing of YAP and TAZ by independent siRNAs reduced the mRNA and protein expression of MCM2-7 in liver cancer cell lines. In vitro analyses revealed that transcription factors of the TEAD family were the most relevant YAP binding partners needed for the transcriptional regulation of MCMs. Using chromatin immunoprecipitation and Dual Luciferase Reporter Assay, we showed that YAP, TAZ and TEAD4 directly bound the MCM promoter. First in vitro data suggested that viability of liver cancer cells, subjected to drug induced replication stress, was exclusively reduced in cells with reduced YAP, TAZ or MCM protein expression. Administration of the YAP/TAZ/TEAD inhibitor Verteporfin reduced the expression of all MCMs in liver cancer cells. Vice versa, the overexpression of YAPS127A in transgenic mice showed significantly increased levels of the proliferation marker Ki67 and MCM2-7. Expression data from 242 HCC patients illustrated an association between YAP and MCM mRNA levels, with elevated MCMs significantly correlating with worse overall survival and early cancer recurrence3. Immunohistochemical stains of HCC tissue micro-arrays revealed a highly significant correlation between Ki67 expression, nuclear YAP overexpression and nuclear MCM2-7 enrichment. In summary, our results strongly suggest that YAP and TAZ facilitate their tumor-supporting properties through the regulation of MCM2-6, a complete protein complex. We conclude that combined inhibition of YAP and TAZ or perturbation of MCM activity might represent an efficient therapeutic approach for the treatment of a subgroup of HCC patients. 1Tschaharganeh D, et al., Gastroenterol. 2013; 2Deegan TD, et al., Curr Opin Struct Biol. 2016; 3Roessler S, et al., Cancer Res. 2010.

Citation Format: Maria Knaub, Sofia Weiler, Stefan Thomann, Peter Schirmacher, Kai Breuhahn. YAP and TAZ induce MCM protein expression to facilitate tumor-supporting properties in liver cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3089.

Induction of Chromosome Instability by Activation of Yes-Associated Protein and Forkhead Box M1 in Liver Cancer

BACKGROUND & AIMS

Many different types of cancer cells have chromosome instability. The hippo pathway leads to phosphorylation of the transcriptional activator yes-associated protein 1 (YAP1, YAP), which regulates proliferation and has been associated with the development of liver cancer. We investigated the effects of hippo signaling via YAP on chromosome stability and hepatocarcinogenesis in humans and mice.

METHODS

We analyzed transcriptome data from 242 patients with hepatocellular carcinoma (HCC) to search for gene signatures associated with chromosomal instability (CIN); we investigated associations with overall survival time and cancer recurrence using Kaplan-Meier curves. We analyzed changes in expression of these signature genes, at mRNA and protein levels, after small interfering RNA-mediated silencing of YAP in Sk-Hep1, SNU182, HepG2, or pancreatic cancer cells, as well as incubation with thiostrepton (an inhibitor of forkhead box M1 [FOXM1]) or verteporfin (inhibitor of the interaction between YAP and TEA domain transcription factor 4 [TEAD4]). We performed co-immunoprecipitation and chromatin immunoprecipitation experiments. We collected liver tissues from mice that express a constitutively active form of YAP (YAP^S127A) and analyzed gene expression signatures and histomorphologic parameters associated with chromosomal instability. Mice were given injections of thiostrepton and livers were collected and analyzed by immunoblotting, immunohistochemistry, histology, and real-time polymerase chain reaction. We performed immunohistochemical analyses on tissue microarrays of 105 HCCs and 7 nontumor liver tissues.

RESULTS

Gene expression patterns associated with chromosome instability, called CIN25 and CIN70, were detected in HCCs from patients with shorter survival time or early cancer recurrence. TEAD4 and YAP were required for CIN25 and CIN70 signature expression via induction and binding of FOXM1. Disrupting the interaction between YAP and TEAD4 with verteporfin, or inhibiting FOXM1 with thiostrepton, reduced the chromosome instability gene expression patterns. Hyperplastic livers and tumors from YAP^S127A mice had increased CIN25 and CIN70 gene expression patterns, aneuploidy, and defects in mitosis. Injection of YAP^S127A mice with thiostrepton reduced liver overgrowth and signs of chromosomal instability. In human HCC tissues, high levels of nuclear YAP correlated with increased chromosome instability gene expression patterns and aneuploidy.

CONCLUSIONS

By analyzing cell lines, genetically modified mice, and HCC tissues, we found that YAP cooperates with FOXM1 to contribute to chromosome instability. Agents that disrupt this pathway might be developed as treatments for liver cancer. Transcriptome data are available in the Gene Expression Omnibus public database (accession numbers: GSE32597 and GSE73396).

Human intervertebral disc cells are genetically modifiable by adenovirus-mediated gene transfer: implications for the clinical management of intervertebral disc disorders

STUDY DESIGN

Human intervertebral disc cells were cultured in monolayer and treated with adenovirus-containing marker genes to determine the susceptibility of the cells to adenovirus-mediated gene transfer.

OBJECTIVES

To test the efficacy of the adenovirus-mediated gene transfer technique for transferring exogenous genes to human intervertebral disc cells in vitro.

SUMMARY OF BACKGROUND DATA

Upregulated proteoglycan synthesis after direct in vivo adenovirus-mediated transfer of growth factor genes to the rabbit intervertebral disc has previously been reported. Before contemplating extending this approach to the treatment of human disc disease, it is necessary to demonstrate that human intervertebral disc cells are indeed susceptible to adenovirus-mediated gene transduction.

METHODS

Human intervertebral disc cells were isolated from disc tissue obtained from 15 patients during surgical disc procedures. The cells were cultured in monolayer and treated with saline containing five different doses of adenovirus carrying the lacZ gene (Ad/CMV-lacZ), saline containing adenovirus carrying the luciferase gene (Ad/CMV-luciferase), or saline alone. Transgene expression was analyzed by 5-bromo-4-chloro-3-indolyl-beta-galactosidase (X-Gal) staining and luciferase assay.

RESULTS

Adenovirus efficiently transferred lacZ and luciferase marker genes to cells from degenerated discs as well as to cells from nondegenerated discs. A minimum dose of 150 MOI Ad/CMV-lacZ was found to be sufficient to achieve transduction of approximately 100% of disc cells-regardless of patient age, sex, surgical indication, disc level, and degeneration grade. No statistically significant difference in the luciferase activities could be detected in disc cell cultures from degenerated and nondegenerated discs treated with Ad/CMV-luciferase.

CONCLUSIONS

In vitro transducibility of human intervertebral disc cells by adenovirus is relatively insensitive to disc degeneration grade. Because the rate-limiting step for successful gene therapy is the ability to transfer genes efficiently to the target tissue, the achievement of efficient gene transfer to human intervertebral disc cells(using a direct, adenovirus-mediated approach) is an important and necessary step in the development of gene therapy strategies for the management of human intervertebral disc disorders.

Comparison of the pharmacological effects of epinephrine administered by the intravenous and endotracheal routes

Epinephrine in various dosages was administered to anesthetized dogs by intravenous and endotracheal routes. Both methods produced measurable effects on heart rate, blood pressure, and respiration. Tachycardia occurred more rapidly after endotracheal administration than after intravenous administration. Respiration appeared to be supported more advantageously with the larger endotracheal dosages. The maximum blood pressure rise was delayed only 60 seconds by the endotracheal route. With an endotracheally administered dose of ten times the intravenous dose, equal responses in blood pressure were obtained. However, when equal doses are compared, there is only a two to three fold increase with the intravenous route. The endotracheal route may be less toxic at higher doses, affording greater safety when large amounts of epinephrine are used. It is concluded that endotracheally administered epinephrine produces significant pharmacologic effects in anesthetized dogs.