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Although new generations of EGFR-tyrosine kinase inhibitors (EGFR-TKI) have been developed for the treatment of patients with non–small cell lung cancer (NSCLC) with EGFR-mutant tumors, TKI resistance often returns as a result of additional EGFR mutations. In addition to seeking for next-generation EGFR-TKI, developing novel EGFR-targeting strategies may hold the key to overcome the vicious cycle of TKI resistance. Endocan is known as a receptor tyrosine kinase ligand enhancer in tumorigenesis, but the impact of endocan on EGFR-driven NSCLC progression remains unknown. In this study, higher endocan levels were found in lung tumors compared with cancer-free tissues and correlated with poor prognosis in patients with NSCLC harboring mutant EGFR; circulating endocan levels were also significantly higher in patients with mutant EGFR. Endocan facilitated EGFR signaling via direct binding and enhancing of the EGF–EGFR interaction and supported the growth of tumors driven by mutated EGFR. Activated EGFR in turn upregulated expression of endocan via JAK/STAT3 and ERK/ELK cascades, thus forming a positive regulatory loop of endocan-EGFR signaling. On the basis of the binding region between endocan and EGFR, we designed therapeutic peptides and demonstrated promising therapeutic effects in xenografts harboring EGFR mutations including TKI-resistant T790M. Together, our findings highlight the novel interaction between endocan and EGFR and new opportunities to effectively target endocan-EGFR regulatory axis in patients with TKI-resistant NSCLC. Significance: Endocan is a novel and critical regulator of EGF/EGFR signaling and serves as an alternative target of EGFR-TKI resistance in NSCLC.

Increasing evidence suggests that there is a unique cell subpopulation in melanoma that can form nonadherent melanospheres in serum-free stem cell medium, mimicking aggressive malignancy. Using melanospheres as a model to investigate progression mechanisms, we found that miR-519d overexpression was sufficient to promote cell proliferation, migration, invasion, and adhesion in vitro and lung metastatic capability in vivo. The cell adhesion receptor EphA4 was determined to be a direct target of miR-519d. Forced expression of EphA4 reversed the effects of miR-519d overexpression, whereas silencing of EphA4 phenocopied the effect of miR-519d. Malignant progression phenotypes were also affected at the level of epithelial-to-mesenchymal transition and the ERK1/2 signaling pathway inversely affected by miR-519d or EphA4 expression. In clinical specimens of metastatic melanoma, we observed significant upregulation of miR-519d and downregulation of EphA4, in the latter case correlated inversely with overall survival. Taken together, our results suggest a significant functional role for miR-519d in determining EphA4 expression and melanoma progression. Significance: These results suggest a significant role for miR-519d in determining expression of a pivotal cell adhesion molecule that may impact risks of malignant progression in many cancers. Cancer Res; 78(1); 216–29. ©2017 AACR.

Ovarian cancer spheroids constitute a metastatic niche for transcoelomic spread that also engenders drug resistance. Spheroid-forming cells express active STAT3 signaling and display stem cell–like properties that may contribute to ovarian tumor progression. In this study, we show that STAT3 is hyperactivated in ovarian cancer spheroids and that STAT3 disruption in this setting is sufficient to relieve chemoresistance. In an NSG murine model of human ovarian cancer, STAT3 signaling regulated spheroid formation and self-renewal properties, whereas STAT3 attenuation reduced tumorigenicity. Mechanistic investigations revealed that Wnt signaling was required for STAT3-mediated spheroid formation. Notably, the Wnt antagonist DKK1 was the most strikingly upregulated gene in response to STAT3 attenuation in ovarian cancer cells. STAT3 signaling maintained stemness and interconnected Wnt/β-catenin signaling via the miR-92a/DKK1–regulatory pathways. Targeting STAT3 in combination with paclitaxel synergistically reduced peritoneal seeding and prolonged survival in a murine model of intraperitoneal ovarian cancer. Overall, our findings define a STAT3–miR-92a–DKK1 pathway in the generation of cancer stem–like cells in ovarian tumors, with potential therapeutic applications in blocking their progression. Cancer Res; 77(8); 1955–67. ©2017 AACR.

Gene therapy trials in human breast, ovarian, and head and neck tumors indicate that adenovirus E1A can sensitize cancer cells to the cytotoxic effects of paclitaxel in vitro and in vivo. Resistance to paclitaxel has been reported to occur in cells expressing low levels of the Forkhead transcription factor FOXO3a. In this article, we report that FOXO3a is critical for E1A-mediated chemosensitization to paclitaxel. RNA interference–mediated knockdown of FOXO3a abolished E1A-induced sensitivity to paclitaxel. Mechanistic investigations indicated that E1A indirectly stabilized FOXO3a by acting at an intermediate step to inhibit a ubiquitin-dependent proteolysis pathway involving the E3 ligase βTrCP and the FOXO3a inhibitory kinase IKKβ. E1A derepressed this inhibitory pathway by stimulating expression of the protein phosphatase 2A (PP2A)/C protein phosphatases, which by binding to the TGF-β–activated kinase TAK1, inhibited its ability to activate IKKβ and, thereby, to suppress βTrCP-mediated degradation of FOXO3a. Thus, by stimulating PP2A/C expression, E1A triggers a signaling cascade that stabilizes FOXO3a and mediates chemosensitization. Our findings provide a leap forward in understanding paclitaxel chemosensitization by E1A, and offer a mechanistic rational to apply E1A gene therapy as an adjuvant for improving therapeutic outcomes in patients receiving paclitaxel treatment. Cancer Res; 71(21); 6878–87. ©2011 AACR.

KH-type splicing regulatory protein (KSRP) is a single-strand RNA binding protein which regulates mRNA stability either by binding to AU-rich elements (AREs) of mRNA 3′UTR or by facilitating miRNA biogenesis to target mRNA. Unlike its well-characterized function at the molecular level in maintaining RNA homeostasis, the role of KSRP in cancer progression remains largely unknown. Here we investigate the role of KSRP in non-small cell lung cancer (NSCLC). We first examined KSRP expression by immunohistochemistry in a cohort containing 196 NSCLC patients and observed a strong positive correlation between KSRP expression and survival of NSCLC patients. Multivariate analysis further identified KSRP as an independent prognostic factor. Manipulating KSRP expression significantly affected in vitro cell mobility and in vivo metastatic ability of NSCLC cells. Microarray analysis identified an ARE-containing gene, EGR3, as a downstream effector of KSRP in NSCLC. Interestingly, we found that KSRP decreased EGR3 mRNA stability in an ARE-independent manner. By screening KSRP-regulated miRNAs in NSCLC cells, we further found that miR-23a directly binds to EGR3 3′UTR, reducing EGR3 expression and thereby inhibiting NSCLC cell mobility. Our findings implicate a targetable KSRP/miR-23a/EGR3 signaling axis in advanced tumor phenotypes Citation Format: Ke-Fan Pan, Ming-Hsien Chien, Wei-Jiunn Lee, Michael Hsiao, Kuo-Tai Hua. KSRP suppresses cell invasion and metastasis through miR-23a-mediated EGR3 mRNA degradation in non-small cell lung 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 5181.

Purpose: Kelch-like ECH-associated protein 1 (Keap1) is an E3 ligase participated in the cellular defense response against oxidative stress through nuclear factor erythroid-2–related factor 2 (Nrf2). However, the role of Keap1 in regulating cancer motility is still controversial. We investigated the contribution of the Keap1–Nrf2 axis in the progression of non-small cell lung cancer (NSCLC). Experimental Design: The expression of Keap1 and Nrf2 was examined via immunohistochemistry, real-time PCR, and Western blot analysis in a cohort of NSCLC tissues and cells. A series of in vivo and in vitro assays was performed to elucidate the contribution of the Keap1–Nrf2 axis in lung cancer mobility and progression. Results: Keap1 expression was decreased in specimens from NSCLC patients with lymph node metastasis compared with patients without metastasis. Higher Keap1 expression levels were correlated with the survival ofNSCLC patients. Moreover,manipulation of Keap1 expression affected cell migration/invasion abilities. Depletion of Nrf2 relieved the migration promotion imposed by Keap1 suppression. Mechanistic investigations found that S100Pwas downregulated in both Keap1-overexpressing and Nrf2-knockdown NSCLC cells. Overexpression of Keap1 and knockdown of Nrf2 both suppressed S100P expression in NSCLC cells. Knockdown of S100P inhibited cell migration in highly invasive NSCLC cells and also relieved the migration promotion imposed by Keap1 suppression in weakly invasive NSCLC cells. Conclusions: Our findings suggest that Keap1 functions as a suppressor of tumor metastasis by targeting the Nrf2/S100P pathway in NSCLC cells. In addition, overexpression of Keap1 may be a novel NSCLC treatment strategy and/or useful biomarker for predicting NSCLC progression. Citation Format: Kuo-Tai Hua, Min-Liang Kuo. Keap1–Nrf2 interaction suppresses cell motility in lung adenocarcinomas by targeting the S100P protein. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr B08.

Emerging evidence indicates that alteration of epigenetic regulation might be a key event for cancer progression. Abnormal expression of histone methyltransferase G9a, which contributes to transcriptional repression of tumor suppressor genes, has been implicated in maintaining cancer cells proliferation. Recent study suggests that inhibition of G9a reduces cancer cell growth. However, its molecular process has not been fully explored. In this study, we show that G9a expression is positively correlated to poor prognosis in head and neck squamous cell carcinoma (HNSCC) patients. Knockdown of G9a or inhibition of its catalytic activity by bix-01294 in HNSCC cells reduced proliferation, colony formation and anchorage-independent growth without inducing necrosis or apoptosis. Instead, complementary approaches including immunoblot analysis, LC3-GFP-fluorescent microscopy and morphologic study by electron microscopy revealed inhibition of G9a inducing autophagy. Pre-treatment with autophagy inhibitor 3-methyladenine (3-MA) or chloroquine (CQ) antagonized the inhibition effect of bix-01294 on cells viability, demonstrating that autophagic cell death is the major consequences in G9a suppressed cells. Mechanistic investigation suggested that ERK phosphatase, DUSP4, may be a downstream target of G9a. Knockdown of G9a and then suppression of DUSP4 expression restored ERK phosphorylation and colony formation but inhibits autophagy induced by G9a silencing. This effect was further reversed by treatment with MAPK/ERK selective inhibitor U0126. Moreover, knockdown of G9a resulted in growth inhibition and autophagy in orthotopic tumor model in mice. Taken together, our results not only point out the mechanism of autophagic cell death induced by inhibition of G9a but also pave a way for new targeting therapy utility for HNSCC in clinical. Citation Format: KAI-CHUN LI, KUO-TAI HUA, CHING-TING TAN, MIN-LIANG KUO. Inhibition of G9a induces DUSP4-dependent autophagic cell death in head and neck squamous cell carcinoma. [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 1332. doi:10.1158/1538-7445.AM2014-1332

80%-90% of eukaryotic proteins are N-α-terminally acetylated. They are mediated by specific N-α-acetyltransferases. However, the biological importance of these N-α-acetyltransferases remains largely unknown. Recently, these N-α-acetyltransferases have been recognized as important characters in many biological processes, including embryonic development, neuron disease and cancer. N-α-acetyltransferase A (Nat A) was first characterized in yeast, it composed of Naa10p, also known as hARD1 (human Arrest defective 1), and Naa15p, also known as NATH (N-acetyl transferase human), are responsible for the N-α-acetylation of majority proteins in mammalian cells. Naa10p is known to be involved in cell cycle control and apoptosis. However, the role of Naa10p in human cancers is elusive. In this study, we found that elevated Naa10p levels are associated with less metastasis to lymph nodes and better prognosis of cancer patients. Naa10p significantly suppressed migration, tumor growth, and metastasis independent of its enzymatic activity. Instead, Naa10p binds to the GIT-binding domain of PIX, thereby preventing the formation of the GIT-PIX-Paxillin complex, resulting in reduced intrinsic Cdc42/Rac1 activity and decreased cell migration. Forced expression of PIX in Naa10-transfected tumor cells restored the migration and metastasis ability. We suggest that Naa10p functions as a tumor metastasis suppressor by disrupting the migratory complex, PIX-GIT- Paxillin, in cancer cells. Our study not only highlights the potential of Naa10p as a therapeutic target for tumor metastasis, but also identifies Naa10p as a regulatory component of the migration complex PIX-GIT-Paxillin. 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 3422. doi:1538-7445.AM2012-3422

Human arrest defective 1 protein, ARD1, is an N-acetyltransferase known to be involved in cell cycle control. We found that ARD1 is highly expressed in the early stage of the cell cycle and less highly expressed in a variety of human malignancies that metastasize to lymph nodes. ARD1 expression favors survival in patients. ARD1 significantly suppressed migration, tumor growth, and metastasis independent of its enzymatic activity. Instead, ARD1 binds to the GIT-binding domain of PIX, thereby preventing the formation of the GIT-PIX-Paxillin complex, resulting in reduced intrinsic Cdc42/Rac1 activities and decreased cell migration. Forced expression of PIX in ARD1-transfected tumor cells restored the migration and metastasis ability. We suggest that ARD1 functions as a novel tumor metastasis suppressor by disrupting the migratory complex, GIT-PIX-Paxillin, in cancer cells. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3376.