Yun-Yong Park

Identification of oncogenic microRNA-17-92/ZBTB4/specificity protein axis in breast cancer.

The human POK family members are transcription factors with a POZ domain and zinc-fingers that act primarily as transcriptional repressors. Several members of this family are involved in oncogenesis and this prompted us to assess whether expression levels of individual POK family members are associated with clinical outcomes in cancer. We have observed that ZBTB4 (zinc-finger and BTB domain containing 4) is downregulated in breast cancer patients, and that its expression is significantly correlated with relapse-free survival. Further integrative analysis of mRNA and microRNA (miR) expression data from the NCI-60 cell lines revealed an inverse correlation between ZBTB4 and oncogenic miRs derived from the miR-17-92 cluster and its paralogs. The experimental results using MDA-MB-231 and MCF-7 human breast cancer cells confirm that miRNAs derived from these clusters, containing miR-17-5p, miR-20a, miR-106a, miR-106b and miR-93, negatively regulate ZBTB4 expression. Overexpression of ZBTB4 or restoration of ZBTB4 by using an antagomir inhibit growth and invasion of breast cancer cells, and this effect is due, in part, to ZBTB4-dependent repression of the specificity protein 1 (Sp1), Sp3 and Sp4 genes, and subsequent downregulation of several Sp-dependent oncogenes, in part, through competition between ZBTB4 and Sp transcription factors for GC-rich promoter sequences. These results confirm that ZBTB4 functions as a novel tumor-suppressor gene with prognostic significance for breast cancer survival, and the oncogenic miR-17-92/ZBTB4/Sp axis may be a potential therapeutic target.

YAP1 and TAZ Activates mTORC1 Pathway by Regulating Amino Acid Transporters in hepatocellular carcinoma

Metabolic activation is a common feature of many cancer cells and is frequently associated with the clinical outcomes of various cancers, including hepatocellular carcinoma. Thus, aberrantly activated metabolic pathways in cancer cells are attractive targets for cancer therapy. Yes‐associated protein 1 (YAP1) and transcriptional coactivator with PDZ‐binding motif (TAZ) are oncogenic downstream effectors of the Hippo tumor suppressor pathway, which is frequently inactivated in many cancers. Our study revealed that YAP1/TAZ regulates amino acid metabolism by up‐regulating expression of the amino acid transporters solute carrier family 38 member 1 (SLC38A1) and solute carrier family 7 member 5 (SLC7A5). Subsequently, increased uptake of amino acids by the transporters (SLC38A1 and SLC7A5) activates mammalian target of rapamycin complex 1 (mTORC1), a master regulator of cell growth, and stimulates cell proliferation. We also show that high expression of SLC38A1 and SLC7A5 is significantly associated with shorter survival in hepatocellular carcinoma patients. Furthermore, inhibition of the transporters and mTORC1 significantly blocks YAP1/TAZ‐mediated tumorigenesis in the liver. These findings elucidate regulatory networks connecting the Hippo pathway to mTORC1 through amino acid metabolism and the mechanisms potential clinical implications for treating hepatocellular carcinoma. Conclusion: YAP1 and TAZ regulate cancer metabolism and mTORC1 through regulation of amino acid transportation, and two amino acid transporters, SLC38A1 and SLC7A5, might be important therapeutic targets. (Hepatology 2016;63:159–172)

The HGF/c-MET Pathway Is a Driver and Biomarker of VEGFR-inhibitor Resistance and Vascular Remodeling in Non–Small Cell Lung Cancer

Purpose: Resistance to VEGFR inhibitors is a major obstacle in the treatment of non–small cell lung cancer (NSCLC). We investigated the cellular mechanisms mediating resistance of NSCLCs to VEGFR tyrosine kinase inhibitors. Experimental Design: We generated murine models of human NSCLC and performed targeted inhibition studies with the VEGFR TKIs cediranib and vandetanib. We used species-specific hybridization of microarrays to compare cancer (human) and stromal (mouse) cell transcriptomes of TKI-sensitive and -resistant tumors. We measured tumor microvascular density and vessel tortuosity to characterize the effects of therapy on the tumor vascular bed. Circulating cytokine and angiogenic factor levels in patients enrolled in VEGFR TKI trials were correlated with clinical outcomes. Results: Murine xenograft models of human lung adenocarcinoma were initially sensitive to VEGFR TKIs, but developed resistance to treatment. Species-specific microarray analysis identified increased expression of stromal-derived hepatocyte growth factor (HGF) as a candidate mediator of TKI resistance and its receptor, c-MET, was activated in cancer cells and tumor-associated stroma. A transient increase in hypoxia-regulated molecules in the initial response phase was followed by adaptive changes resulting in a more tortuous vasculature. Forced HGF expression in cancer cells reduced tumor sensitivity to VEGFR TKIs and produced tumors with tortuous blood vessels. Dual VEGFR/c-MET signaling inhibition delayed the onset of the resistant phenotype and prevented the vascular morphology alterations. In patients with cancer receiving VEGFR TKIs, high pretreatment HGF plasma levels correlated with poorer survival. Conclusions: HGF/c-MET pathway mediates VEGFR inhibitor resistance and vascular remodeling in NSCLC. Clin Cancer Res; 23(18); 5489–501. ©2017 AACR.

Rab25 augments cancer cell invasiveness through a β1 integrin/EGFR/VEGF-A/Snail signaling axis and expression of fascin

The small GTP-binding protein Rab25 is associated with tumor formation and progression. However, recent studies have shown discordant effects of Rab25 on cancer cell progression depending on cell lineage. In the present study, we elucidate the underlying mechanisms by which Rab25 induces cellular invasion. We demonstrate that Rab25 increases β1 integrin levels and subsequent activation of EGFR and upregulation of VEGF-A expression, leading to increased Snail expression, epithelial-to-mesenchymal transition and cancer cell invasiveness. Strikingly, we identify that Snail mediates Rab25-induced cancer cell invasiveness through fascin expression and that ectopic expression of Rab25 aggravates metastasis of ovarian cancer cells to the lung. We thus demonstrate a novel role of a β1 integrin/EGFR/VEGF-A/Snail signaling cascade in Rab25-induced cancer cell aggressiveness through induction of fascin expression, thus providing novel biomarkers and potential therapeutic targets for Rab25-expressing cancer cells.

Verteporfin inhibits gastric cancer cell growth by suppressing adhesion molecule FAT1

Gastric cancer (GC) is a leading cause of death worldwide and in urgent need of targeted drug development. In the current, we investigated the ability of a repositioned drug verteporfin (VP), originally a treatment for macular degeneration, to inhibit GC cell growth. VP inhibited growth of various GC cell lines. Gene expression profiling of GC cell lines treated with VP revealed that migration-related genes and those with oncogenic potential were down-regulated. Of these genes, we found that FAT1, an adhesion molecule promoting cell invasion, was highly suppressed by VP. Silencing of FAT1 suppressed cell migration and invasion as VP did. FAT1 expression was up-regulated in tumors, and patients with high FAT1-expressing tumors had a worse prognosis. We propose that VP- targeting FAT1 to suppress metastatic potential is a promising therapeutic strategy against GC.

Abstract 356: Reconstruction of nuclear receptor network reveals that NR2E3 is a novel upstream regulator of ESR1 in breast cancer

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL ESR1 is one of the most important oncogenes and therapeutic targets in breast cancer. By applying systems-level re-analysis of publicly available gene expression data, we uncovered potential regulator of ESR1. We demonstrated that orphan nuclear receptor NR2E3 regulates ESR1 via direct binding to the ESR1 promoter with concomitant recruitment of PIAS3 to promoter in breast cancer cells, and is essential for physiological cellular activity of ESR1 in estrogen receptor (ER)-positive breast cancer cells. Moreover, expression of NR2E3 was significantly associated with recurrence-free survival and favorable response to tamoxifen treatment in women with ER-positive breast cancer. Our results provide mechanistic insight into how ESR1 is regulated by NR2E3 and clinical relevance of NR2E3 in breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 356. doi:10.1158/1538-7445.AM2011-356

Abstract 4734: Activation of yap1 is significantly associated with poor prognosis and cetuximab resistance in colorectal cancer patients

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Purpose: To investigate the clinical significance of activation of YAP1, a newly identified oncogene in colorectal cancer (CRC). Patients and Methods: A gene expression signature reflecting YAP1 activation was identified in CRC cells, and CRC patients were stratified into two groups according to this signature: activated YAP1 CRC (AYCC) or inactivated YAP1 CRC (IYCC). Stratified patients in six test cohorts were evaluated to determine the effect of the signature on CRC prognosis and response to treatment with cetuximab. Results: The activated YAP1 signature was associated with poor prognosis for CRC in four independent patient cohorts with stage I-III disease (total n = 1,028). In a multivariate analysis, the impact of the YAP1 signature on the disease-free survival rate was independent of other clinical variables [hazard ratio (HR), 1.63; 95% confidence interval (CI), 1.25-2.13; P < .001]. In patients with stage IV CRC, AYCC patients had a poorer disease control rate and progression-free survival duration after cetuximab-based monotherapy than did IYCC patients (HR, 1.82; 95% CI, 1.05-3.16; P = .03). In multivariate analysis, the effect of YAP1 activation on PFS was independent of KRAS mutation status and cetuximab-based therapy was effective only in IYCC patients without KRAS mutations. Conclusion: Activation of YAP1 is highly associated with poor prognosis for CRC and may be useful in identifying patients with CRC resistant to treatment with cetuximab. Citation Format: Keun-Wook Lee, Sung Sook Lee, Sang-Bae Kim, Yun-Yong Park, Bo Hwa Sohn, Hyun-Sung Lee, Ju-Seog Lee. Activation of yap1 is significantly associated with poor prognosis and cetuximab resistance in colorectal cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4734. doi:10.1158/1538-7445.AM2014-4734

Abstract 5398: TARDBP regulates glycolysis in hepatocellular carcinoma by regulating PFKP through miR-520.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Metabolic changes are common features of many cancer cells and are frequently associated with the clinical outcome of patients with various cancers including hepatocellular carcinoma (HCC). Thus, aberrant metabolic pathways in cancer cells are attractive targets for cancer therapy. However, our understanding of cancer-specific regulatory mechanisms of cell metabolism is still very limited. We found that Tat activating regulatory DNA-binding protein (TARDBP) is a novel regulator of glycolysis in HCC cells. TARDBP regulates expression of the platelet isoform of phosphofructokinase (PFKP), the rate-limiting enzyme of glycolysis that catalyzes the irreversible conversion of fructose-6-phosphate to fructose-1,6-bisphosphate. Silencing of TARDBP expression in multiple HCC cell lines leads to impaired glucose metabolism and inhibition of in vitro and in vivo growth of HCC cells. Notably, the miR-520 family is an intermediate regulator of TARDBP-mediated regulation of glycolysis. Mechanistically, TARDBP suppressed expression of the miR-520 family, which in turn inhibited expression of PFKP. We further showed that expression of PFKP is significantly associated with the overall survival of patients with HCC. Our study provides new mechanistic insights into the regulation of glycolysis in HCC cells and reveals TARDBP as a potential therapeutic target for HCC. Citation Format: Yun-Yong Park, Sang Bae Kim, Hee Dong Han, Bo-Hwa Sohn, Jiyong Liang, Yiling Lu, Gordon Mills, Anil Sood, Ju-Seog Lee. TARDBP regulates glycolysis in hepatocellular carcinoma by regulating PFKP through miR-520. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5398. doi:10.1158/1538-7445.AM2013-5398

Abstract 5222: Identification of cell signaling pathway associated miRNAs in cancer cells using a systems biological approach.

MicroRNAs(miRNAs) are single-stranded, non-coding RNA molecules and on average only 22 nucleotides long that regulate gene expression at the post-transcriptional level. Target predictions of miRNA based on sequence are limited due to too many candidates resulting in high false positives. To overcome this limitation functional target prediction approaches have been investigated with mRNA and miRNA expression data. These approaches can be used in the computational assessment of functional miRNA-target association. However, these approaches with miRNA-mRNA association were not enough to verify real functional targets at protein level, which could affect on cell signaling pathway. Therefore, in the present study to compensate this limitation, we developed a novel correlation based approach (sequence-independence) to predict potential miRNA targets with genomic and proteomic data, protein, miRNA and mRNA array data, in NCI-60 cells. To establish a prediction model for identifying the association of miRNA-cell signaling pathways by analyzing genomic and proteomic data, we performed a correlation based method among miRNA, mRNA and protein expression profile. Using this approach, we generated the Association score matrix (ASM) between miRNA and protein probes. Based on ASM, we finally generated the highly associated miRNAs with cell signaling pathways called miRNA-pathway association map (miRPM). To validate our approach, we used miR-500 as an example to investigate the hypothetical target regulation mechanisms predicted by miRPM. We confirmed in-vitro that mir-500 highly is associated with ERK/MAPK signaling pathway in melanoma and breast cancer cells. Furthermore, we found PP1/PP2 might be a direct target of miR-500 to regulate activating the ERK/MAPK pathway. In conclusion, we developed a novel expression profile based approach to systematically predict potential miRNA functional targets which play critical roles in cell signaling pathways from the NCI-60 genomic and proteomic data at whole genomic scale. Our approach might be applied to investigate the unknown regulatory role of miRNAs in signaling pathways and gene regulatory networks. Citation Format: Sangbae Kim, Bo Hwa Sohn, Yun-Yong Park, Ji-Hoon Kim, Sung Sook Lee, Micheal A. Davies, Gordon B. Mills, Ju-Seog Lee. Identification of cell signaling pathway associated miRNAs in cancer cells using a systems biological approach. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5222. doi:10.1158/1538-7445.AM2013-5222

Abstract 5142: Up-regulation of glutamine synthetase attenuates the oncogenicity of wnt/β-catenin signaling in hepatocellular carcinoma

Wnt/β-catenin signaling has been known to be involved in many cellular processes including cell proliferation, migration, and survival. Aberrant activation of Wnt/β-catenin signaling has been widely reported in many cancers and associated with poor outcome after treatments. However, activation of Wnt/β-catenin signaling in hepatocellular carcinoma (HCC) has been known to be significantly associated with favorable outcome. In this study, we identified 82 genes as a β-catenin signature by analyzing expression data from tumor tissues of patients with HCC and liver tissues from active β-catenin mutant transgenic mice. HCC patients with the β-catenin signature have significantly better prognosis in both overall survival and recurrence-free survival than those without the signature. Further analysis of β-catenin signature revealed over-expression of glutamine synthetase (GS), liver-specific β-catenin target gene, and shift of glutamine metabolism. Cell growth rate were highly dependent on GS expression levels. Cell proliferation rate was increased by GS knockdown using shRNAs but decreased by GS overexpression in HCC cell lines. Intracellular glutamate concentrations were severely decreased by GS overexpression. GS overexpression in HCC cells also led to decrease intracellular α-ketoglutarate levels impeding TCA cycle, and intracellular glutathione levels accumulating high reactive oxygen species (ROS). In conclusion, we found GS up-regulation in HCC cells inhibited cell growth by glutamate depletion and thereby lower anaplerotic metabolic activity and higher ROS levels. Our results present molecular mechanisms for the favorable outcome in HCC patients with CTNNB1 mutations and importance of glutamine metabolism in cancer cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5142. doi:1538-7445.AM2012-5142