Minsoo Koh

The p38 MAPK inhibitors for the treatment of inflammatory diseases and cancer.

Background: The p38 mitogen-activated protein kinase (MAPK) is activated by various pro-inflammatory and stressful stimuli. Mounting evidence suggests that the p38 MAPK signaling cascade is involved in various biological responses other than inflammation such as cell proliferation, differentiation, apoptosis and invasion, suggesting that the p38 MAPK can serve as a potential therapeutic target for the treatment of not only inflammatory diseases but also cancer. Methods: The unique characteristics of p38 MAPK are summarized with regard to activation and function of p38 MAPK signaling cascades. We then discuss the involvement of p38 MAPK in diseases and the implications of the possible therapeutic use of p38 MAPK inhibitors. The p38 MAPK inhibitors that have been used in the in vitro/in vivo systems as well as in the clinical trials are summarized. Results/conclusion: The p38 MAPK plays an important role in key cellular processes related to inflammation and cancer. Understanding the signal transduction mechanisms and gene regulation by p38 MAPK provides useful information in the development of p38 MAPK inhibitors with therapeutic benefits with reduced side effects. In this review, we summarize and present the list of p38 MAPK inhibitors in in vitro/in vivo studies as well as in clinical trials.

Discoidin domain receptor 1 is a novel transcriptional target of ZEB1 in breast epithelial cells undergoing H-Ras-induced epithelial to mesenchymal transition

The epithelial‐to‐mesenchymal transition (EMT) process allows carcinoma cells to dissociate from the primary tumor thereby facilitating tumor cell invasion and metastasis. Ras‐dependent hyperactive signaling is commonly associated with tumorigenesis, invasion, EMT, and metastasis. However, the downstream effectors by which Ras regulates EMT remain ill defined. In this study, we show that the H‐Ras pathway leads to mesenchymal‐like phenotypic changes in human breast epithelial cells by controlling the ZEB1/microRNA−200c axis. Moreover, H‐Ras suppresses the expression of the discoidin domain receptor 1 (DDR1), a collagen receptor tyrosine kinase, via ZEB1, thus identifying ZEB1 as a novel transcriptional repressor of DDR1. Mutation studies on the putative promoter of the DDR1 gene revealed that bipartite Z‐ and E‐box elements play a key role in transcriptional repression of DDR1 in Hs578T and MDA‐MB‐231 breast carcinoma cell lines by ZEB1. Furthermore, we found an inverse correlation between ZEB1 and DDR1 expression in various cancer cell lines and in human breast carcinoma tissues. Consistently, overexpression of DDR1 reduced the invasive phenotype of mesenchymal‐like triple‐negative breast cancer cells in 3D cultures and in vivo. Thus, ZEB1s role in maintenance of EMT in breast carcinoma cells is mediated in part by its ability to suppress DDR1 expression and consequently contribute to the activation of the invasive phenotype. Taken together, our results unveil a novel H‐Ras/ZEB1/DDR1 network that contributes to breast cancer progression in triple‐negative breast cancers.

A novel metformin derivative, HL010183, inhibits proliferation and invasion of triple-negative breast cancer cells.

Mounting evidence suggests that metformin (N,N-dimethylbiguanide), a widely prescribed drug for the treatment of type II diabetes, exerts an anti-tumor effect on several cancers including breast cancer. Breast cancer has been estimated as one of the most commonly diagnosed types of cancer among women. In particular, triple-negative breast cancers are associated with poor prognosis and metastatic growth. In the present study, we synthesized a novel metformin derivative 5 (HL010183) and metformin salts, 9a, 9b, and 9c (metformin gamma-aminobutyric acid (GABA) salt, metformin pregabalin salt and metformin gabapentin salt), which exerted more potent inhibitory effects on the proliferation and invasiveness of Hs578T triple-negative breast carcinoma cells than metformin. Importantly, 5 showed approximately 100-fold more potent effects compared to metformin. In a triple-negative breast cancer xenograft model, 5 showed a comparable degree of inhibitory effect on in vivo tumor growth at the 100mg/kg dose to that of metformin at 500 mg/kg. Our results clearly demonstrate that 5 exerts a potent anti-tumor effect both in vitro and in vivo, paving the way for a strategy for treatment of triple-negative breast cancer.

Activation of H-Ras and Rac1 correlates with epidermal growth factor-induced invasion in Hs578T and MDA-MB-231 breast carcinoma cells

There is considerable experimental evidence that hyperactive Ras proteins promote breast cancer growth and development including invasiveness, despite the low frequency of mutated forms of Ras in breast cancer. We have previously shown that H-Ras, but not N-Ras, induces an invasive phenotype mediated by small GTPase Rac1 in MCF10A human breast epithelial cells. Epidermal growth factor (EGF) plays an important role in aberrant growth and metastasis formation of many tumor types including breast cancer. The present study aims to investigate the correlation between EGF-induced invasiveness and Ras activation in four widely used breast cancer cell lines. Upon EGF stimulation, invasive abilities and H-Ras activation were significantly increased in Hs578T and MDA-MB-231 cell lines, but not in MDA-MB-453 and T47D cell lines. Using small interfering RNA (siRNA) to target H-Ras, we showed a crucial role of H-Ras in the invasive phenotype induced by EGF in Hs578T and MDA-MB-231 cells. Moreover, siRNA-knockdown of Rac1 significantly inhibited the EGF-induced invasiveness in these cells. Taken together, this study characterized human breast cancer cell lines with regard to the relationship between H-Ras activation and the invasive phenotype induced by EGF. Our data demonstrate that the activation of H-Ras and the downstream molecule Rac1 correlates with EGF-induced breast cancer cell invasion, providing important information on the regulation of malignant progression in mammary carcinoma cells.

A novel role for flotillin-1 in H-Ras-regulated breast cancer aggressiveness.

Elevated expression and aberrant activation of Ras have been implicated in breast cancer aggressiveness. H‐Ras, but not N‐Ras, induces breast cell invasion. A crucial link between lipid rafts and H‐Ras function has been suggested. This study sought to identify the lipid raft protein(s) responsible for H‐Ras‐induced tumorigenicity and invasiveness of breast cancer. We conducted a comparative proteomic analysis of lipid raft proteins from invasive MCF10A human breast epithelial cells engineered to express active H‐Ras and non‐invasive cells expressing active N‐Ras. Here, we identified a lipid raft protein flotillin‐1 as an important regulator of H‐Ras activation and breast cell invasion. Flotillin‐1 was required for epidermal growth factor‐induced activation of H‐Ras, but not that of N‐Ras, in MDA‐MB‐231 triple‐negative breast cancer (TNBC) cells. Flotillin‐1 knockdown inhibited the invasiveness of MDA‐MB‐231 and Hs578T TNBC cells in vitro and in vivo. In xenograft mouse tumor models of these TNBC cell lines, we showed that flotillin‐1 played a critical role in tumor growth. Using human breast cancer samples, we provided clinical evidence for the metastatic potential of flotillin‐1. Membrane staining of flotillin‐1 was positively correlated with metastatic spread (p = 0.013) and inversely correlated with patient disease‐free survival rates (p = 0.005). Expression of flotillin‐1 was associated with H‐Ras in breast cancer, especially in TNBC (p < 0.001). Our findings provide insight into the molecular basis of Ras isoform‐specific interplay with flotillin‐1, leading to tumorigenicity and aggressiveness of breast cancer.

Tumor-associated macrophages secrete CCL2 and induce the invasive phenotype of human breast epithelial cells through upregulation of ERO1-α and MMP-9

Tumor-associated macrophages (TAMs) are major components of tumor microenvironment that promote invasion and metastasis of cancer cells. In this study, we investigated the effect of TAMs on phenotypic conversion of non-neoplastic MCF10A human breast epithelial cells using an indirect co-culture system. Co-culture with TAMs induced epithelial-to-mesenchymal transition, invasive phenotype, and MMP-9 upregulation in MCF10A cells. Comparative proteomic analysis revealed that endoplasmic reticulum oxidoreductase (ERO)1-α was increased in MCF10A cells co-cultured with TAMs compared to that in mono-cultured cells. ERO1-α was crucial for TAMs-induced invasive phenotype and MMP-9 upregulation involving transcription factors c-fos and c-Jun. Cytokine array analysis showed that levels of interleukin (IL)-6, C-X-C motif ligand (CXCL)1, C-C motif ligand (CCL)2, growth-regulated protein (GRO), IL-8, and granulocyte-macrophage colony-stimulating factor (GM-CSF) were increased in conditioned media of co-cultured cells. Among these cytokines increased in conditioned media of co-cultured cells, CCL2 was secreted from TAMs, leading to induction of ERO1-α, MMP-9 upregulation, and invasiveness in MCF10A cells. Our findings elucidated a molecular mechanism underlying the aggressive phenotypic change of non-neoplastic breast cells by co-culture with TAMs, providing useful information for prevention or treatment of recurrent breast cancer.

Abstract 5263: Identification of a lipid raft protein that is required for H-Ras activation and breast cancer aggressiveness

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA In an attempt to identify biomarkers and/or therapeutic targets for malignant breast cancer, the present study showed a comparative proteome profiling of invasive MCF10A human breast epithelial cells engineered to express active H-Ras and non-invasive cells expressing active N-Ras. Here, we identified a lipid raft protein DS-20, a crucial regulator of H-Ras activation, as a potential marker for invasive breast cancer. DS-20 (amino acid residues 1-38) interacted with H-Ras (residues 166-189) in lipid rafts and their interaction was important for H-Ras activation. DS-20 knockdown inhibited H-Ras activation and invasion in Hs578T triple-negative breast cancer cells (TNBC) and T24 bladder carcinoma cells in which H-Ras is endogenously activated, suggesting a crucial role of DS-20 in the invasive program which relies on the activation of H-Ras. We further showed that DS-20 was required for epidermal growth factor-induced H-Ras activation, but not that of N-Ras, in MDA-MB-231 TNBC cells. Intravasation of MDA-MB-231 cells treated with shRNA DS-20 in the chick chorioallantoic membrane model was markedly reduced, indicating that DS-20 is required for an invasive capacity in vivo. In a xenograft mice tumor model, DS-20 was essential for in vivo tumor aggressiveness of Hs578T cells, suggesting DS-20 as a potential target for the treatment of breast cancer. Using human breast cancer samples, we provide clinical evidence for the tumorigenic potential of DS-20 and its association with H-Ras. Taken together, our findings provide a new insight into the molecular basis of Ras isoform-specific interplay with plasma membrane leading to cell invasion. Citation Format: Hae-Young Yong, Eun-Sook Kim, Minsoo Koh, Hwajin Son, You Rim Jeon, Jin-Sun Hwang, Myeong-Ok Kim, Yujin Cha, Wahn Soo Choi, Dong-Young Noh, Kyung-Min Lee, Ki-Bum Kim, Jae-Seon Lee, Hyung Joon Kim, Hong-Hee Kim, Eun Joo Kim, So Yeon Park, Hyeong-Reh Choi Kim, Aree Moon. Identification of a lipid raft protein that is required for H-Ras activation and breast cancer aggressiveness. [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 5263. doi:10.1158/1538-7445.AM2014-5263

Abstract 1076: Activation of H-Ras and Rac1 correlates with epidermal growth factor-induced breast cell invasion

There are considerable experimental evidences that hyperactive Ras proteins promote breast cancer growth and development including invasiveness despite of low frequency of mutated forms of Ras in breast cancer. We have previously shown that H-Ras, but not N-Ras, induces an invasive phenotype mediated by small GTPase Rac1 in MCF10A human breast epithelial cells. Epidermal growth factor (EGF) plays important roles in aberrant growth and metastasis formation of many tumor types including breast cancer. Here, we investigated the involvement of H-Ras in the EGF-induced invasive ability of four different breast cancer cell lines. Upon EGF stimulation, H-Ras activation was increased in the invasive breast cancer cells, MDA-MB-231 and Hs578T cells, but not in non-invasive breast cancer cells, MDA-MB-453 and T47D cells. Using small interfering RNA (siRNA) targeting H-Ras, we showed a crucial role of H-Ras in invasive phenotype induced by EGF in MDA-MB-231 and Hs578T cells. Moreover, knockdown of Rac1significantly inhibited the EGF-induced invasiveness in these cells. Taken together, our data demonstrate that the activation of H-Ras and its downstream molecule Rac1 correlates with breast cancer cell invasion induced by EGF, providing useful information on the regulation of malignant progression in mammary carcinoma. [This work was supported by the Korea government (Nos.ROA-2008-000-20070-0)] 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 1076. doi:10.1158/1538-7445.AM2011-1076