Ki Cheong Park

Gastric cancer is a heterogeneous cancer, making treatment responses difficult to predict. Here we show that we identify two distinct molecular subtypes, mesenchymal phenotype (MP) and epithelial phenotype (EP), by analyzing genomic and proteomic data. Molecularly, MP subtype tumors show high genomic integrity characterized by low mutation rates and microsatellite stability, whereas EP subtype tumors show low genomic integrity. Clinically, the MP subtype is associated with markedly poor survival and resistance to standard chemotherapy, whereas the EP subtype is associated with better survival rates and sensitivity to chemotherapy. Integrative analysis shows that signaling pathways driving epithelial-to-mesenchymal transition and insulin-like growth factor 1 (IGF1)/IGF1 receptor (IGF1R) pathway are highly activated in MP subtype tumors. Importantly, MP subtype cancer cells are more sensitive to inhibition of IGF1/IGF1R pathway than EP subtype. Detailed characterization of these two subtypes could identify novel therapeutic targets and useful biomarkers for prognosis and therapy response.

Cellular oxygen sensing is required for hypoxia-inducible factor-1α stabilization, which is important for tumor cell survival, proliferation, and angiogenesis. Here we find that terpestacin, a small molecule previously identified in a screen of microbial extracts, binds to the 13.4-kDa subunit (UQCRB) of mitochondrial Complex III, resulting in inhibition of hypoxia-induced reactive oxygen species generation. Consequently, such inhibition blocks hypoxia-inducible factor activation and tumor angiogenesis in vivo, without inhibiting mitochondrial respiration. Overexpression of UQCRB or its suppression using RNA interference demonstrates that it plays a crucial role in the oxygen sensing mechanism that regulates responses to hypoxia. These findings provide a novel molecular basis of terpestacin targeting UQCRB of Complex III in selective suppression of tumor progression. Cellular oxygen sensing is required for hypoxia-inducible factor-1α stabilization, which is important for tumor cell survival, proliferation, and angiogenesis. Here we find that terpestacin, a small molecule previously identified in a screen of microbial extracts, binds to the 13.4-kDa subunit (UQCRB) of mitochondrial Complex III, resulting in inhibition of hypoxia-induced reactive oxygen species generation. Consequently, such inhibition blocks hypoxia-inducible factor activation and tumor angiogenesis in vivo, without inhibiting mitochondrial respiration. Overexpression of UQCRB or its suppression using RNA interference demonstrates that it plays a crucial role in the oxygen sensing mechanism that regulates responses to hypoxia. These findings provide a novel molecular basis of terpestacin targeting UQCRB of Complex III in selective suppression of tumor progression.

BACKGROUND AND PURPOSE: Activation of hepatic stellate cells (HSCs) is a crucial step in the pathogenesis of hepatic fibrosis. Histone deacetylase (HDAC) is an attractive target in liver fibrosis because it plays a key role in gene expression and cell differentiation. We have developed a HDAC inhibitor, N-hydroxy-7-(2-naphthylthio)heptanomide (HNHA), and investigated the anti-fibrotic activity of HNHA in vitro and in vivo. EXPERIMENTAL APPROACH: We investigated the anti-fibrotic effect of HNHA on mouse and human HSC activation in vitro and in the liver of bile duct-ligated (BDL) rats in vivo using cell proliferation assays, cell cycle analysis, biochemical assay, immunohistochemistry and Western blots. Liver pathology was assessed with histochemical techniques. KEY RESULTS: HNHA inhibited proliferation and arrested the cell cycle via p21 induction in HSCs. In addition, HNHA induced apoptosis of HSCs, which was correlated with reduced COX-2 expression, NF-κB activation and cell death signals. HNHA restored liver function and decreased the accumulation of extracellular matrix in the liver via suppression of HSC activation in BDL rats in vivo. HNHA administration also increased survival in BDL rats. CONCLUSIONS AND IMPLICATIONS: HNHA improved liver function, suppressed liver fibrosis and increased survival of BDL rats, accompanied by reduction of cell growth, activation and survival of HSCs. These findings show that HNHA may be a potent anti-fibrosis agent against hepatic fibrosis because of its multi-targeted inhibition of HSC activity in vivo and in vitro.

Abstract Purpose: Cancer cells grow in an unfavorable metabolic milieu in the tumor microenvironment and are constantly exposed to metabolic stress such as chronic nutrient depletion. Cancer stem-like cells (CSC) are intrinsically resistant to metabolic stress, thereby surviving nutrient insufficiency and driving more malignant tumor progression. In this study, we aimed to demonstrate the potential mechanisms by which CSCs avoid Ca2+-dependent apoptosis during glucose deprivation. Experimental Design: We investigated cell viability and apoptosis under glucose deprivation, performed genome-wide transcriptional profiling of paired CSCs and parental cells, studied the effect of calcium/calmodulin-dependent protein kinase 2 alpha (CaMK2α) gene knockdown, and investigated the role of nuclear factor kappa B (NFκB) in CSCs during time-dependent Ca2+-mediated and glucose deprivation–induced apoptosis. We also observed the effect of combined treatment with 2-deoxy-d-glucose, a metabolic inhibitor that mimics glucose deprivation conditions in mouse xenograft models, and thapsigargin, a specific inhibitor of sarco/endoplasmic reticulum Ca2+-ATPase (SERCA). Results: We demonstrated the coordinated upregulation of SERCA in CSCs. SERCA, in turn, is transcriptionally regulated by CaMK2α via NFκB activation. Combined treatment with 2-deoxy-d-glucose and thapsigargin, a specific inhibitor of SERCA, significantly reduced tumor growth compared with that in untreated control animals or those treated with the metabolic inhibitor alone. Conclusions: The current study provides compelling evidence that CaMK2α acts as a key antiapoptosis regulator in metabolic stress-resistant CSCs by activating NFκB. The latter induces expression of SERCA, allowing survival in glucose-deprived conditions. Importantly, our combination therapeutic strategy provides a novel approach for the clinical application of CSC treatment. Clin Cancer Res; 24(7); 1677–90. ©2017 AACR.