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).

Abstract A60: Foxf1 transcription factor drives progression of benign lung adenomas to malignant adenocarcinomas

Lung cancer is the leading cause of cancer-related deaths in the United States with current 5-year survival only 8—12%. Patients with non-small cell lung cancer (NSCLC) develop metastases prior to clinical symptoms, which reduces successful treatment outcomes. The new therapeutic approaches targeting progression and metastasis of NSCLC are needed. Foxf1 transcription factor is expressed in mesenhyme-derived cells, such as fibroblasts, smooth muscle cells and endothelial cells, but absent from epithelial-derived cells, such as alveolar and airway epithelial cells, and benign lung adenoma cells. In present study, we used immunohistochemistry to demonstrate that Foxf1 expression is up-regulated in the invasive front of human lung adenocarcinomas. Foxf1 expression is also induced in mouse lung adenocarcinomas, caused by either activation of K-Ras G12D transgene or transplantation of Lewis Lung Carcinoma (LLC) cells. In vitro, shRNA-mediated depletion of Foxf1 from LLC cells decreased migration, invasion and colony formation of LLC cells on soft agar. Depletion of Foxf1 reduced mRNA and protein levels of Twist1, and prevented TGFbeta-induced EMT. In vivo, Foxf1-depleted LLC cells failed to form lung metastasis in the transplantation model of lung cancer. Furthermore, we generated transgenic mice with Doxycycline-inducible expression of Foxf1 under control of epithelial-specific SPC-promoter (epFoxf1 mice). Lung adenomas in these mice were induced by urethane. Activation of the Foxf1 transgene in pre-existing lung adenomas promoted their progression towards adenocarcinomas that invaded adjacent bronchiolar lumens and pleural surfaces. Transgenic expression of Foxf1 in tumor cells resulted in the loss of cell polarity, decreased E-cadherin, and increased expression of aSMA, Twist1 and other EMT associated genes. Foxf1 directly bound to promoter region of Twist1, implicating the Foxf1 in the regulation of the Twist1 gene. The present study provides the first genetic evidence that aberrant expression of Foxf1 induces EMT in lung tumors and promotes the progression of lung adenomas to invasive adenocarcinomas, suggesting that Foxf1 is a promising target for anti-cancer therapy.

Citation Format: Xinjian Wang, David Balli, Tien Le, Vladimir V. Kalinichenko, Tatiana V. Kalin. Foxf1 transcription factor drives progression of benign lung adenomas to malignant adenocarcinomas. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr A60.