Fumiyuki Sato

Prevalence and characteristics of naturally occurring sofosbuvir resistance-associated variants in patients with hepatitis C virus genotype 1b infection.

Sofosbuvir (SOF), a nucleotide analog pro‐drug, targets hepatitis C virus (HCV) NS5B polymerase and shows potential for treating HCV infection, given its high efficacy and good barrier to resistance. However, in addition to the rare resistant‐associated variant (RAV) of non‐structural protein NS5B S282T, several new potential RAVs of SOF have been reported, especially related to HCV genotype 1b. However, the prevalence and characteristics of these RAVs have not been clarified.

EGFR inhibitors prevent induction of cancer stem-like cells in esophageal squamous cell carcinoma by suppressing epithelial-mesenchymal transition

There exists a highly tumorigenic subset of esophageal squamous cell carcinoma (ESCC) cells defined by high expression of CD44. A novel therapy targeting these cancer stem-like cells (CSCs) is needed to improve prognosis of ESCC. CSCs of ESCC have a mesenchymal phenotype and epithelial-mesenchymal transition (EMT) is critical to enrich and maintain CSCs. EGFR, frequently overexpressed in ESCC, has pivotal roles in EMT induced by TGF-β in invasive fronts. Thus, EMT in invasive fronts of ESCC might be important for CSCs and EGFR could be a target of a novel therapy eliminating CSCs. However, effects of EGFR inhibitors on CSCs in ESCC have not been fully examined. EGFR inhibitors, erlotinib and cetuximab, significantly suppressed enrichment of CSCs via TGF-β1-mediated EMT. Importantly, EGFR inhibitors sharply suppressed ZEB1 that is essential for EMT in ESCC. Further, EGFR inhibitors activated Notch1 and Notch3, leading to squamous cell differentiation. EGFR inhibition may suppress expression of ZEB1 and induce differentiation, thereby blocking EMT-mediated enrichment of CSCs. In organotypic 3D culture, a form of human tissue engineering, tumor cells in invasive nests showed high expression of CD44. Erlotinib significantly blocked invasion into the matrix and CD44 high expressing CSCs were markedly suppressed by erlotinib in organotypic 3D culture. In conclusion, EMT is a critical process for generation of CSCs and the invasive front of ESCC, where EMT occurs, might form a CSC niche in ESCC. EGFR inhibitors could suppress EMT in invasive fronts and be one therapeutic option targeting against generation of CSCs in ESCC.

Safety and efficacy of daclatasvir and asunaprevir in hepatitis C virus‐infected patients with renal impairment

Hepatitis C virus (HCV) infection is a risk factor for end‐stage renal disease, renal graft failure, and hemodialysis patient mortality. However, the efficacy of direct‐acting antiviral therapy for HCV‐infected patients with renal impairment is unclear. Additionally, the promising NS5B inhibitor sofosbuvir has not been recommended for patients with severe renal impairment. In this prospective, multicenter study, we evaluated the efficacy and safety of daclatasvir and asunaprevir combination therapy, with a focus on patients with renal impairment.

Serum granulysin levels as a predictor of serious telaprevir-induced dermatological reactions.

Telaprevir‐based therapy for chronic hepatitis C patients is effective; however, the high prevalence of dermatological reactions is an outstanding issue. The mechanism and characteristics of such adverse reactions are unclear; moreover, predictive factors remain unknown. Granulysin was recently reported to be upregulated in the blisters of patients with Stevens–Johnson syndrome (SJS). Therefore, we investigated the risk factors for severe telaprevir‐induced dermatological reactions as well as the association between serum granulysin levels and the severity of such reactions.

Hepatitis B virus X protein impairs α-interferon signaling via up-regulation of suppressor of cytokine signaling 3 and protein phosphatase 2A.

Hepatitis B Virus (HBV) causes liver cirrhosis and hepatocellular carcinoma. Standard therapy includes treatment with interferon (IFN); however, its efficacy is limited. HBV has been reported to impair IFN signaling; however, the mechanism is unclear. Here, the relationship between HBV X protein (HBx) and IFN signaling was investigated by establishing HepG2 cells, stably expressing HBx (HepG2/HBx) via retrovirus‐mediated gene transfer. Subsequently, IFN negative‐regulator expression and its mechanism were studied. HepG2/HBx cells showed reduced expression of IFN‐stimulated genes and expressed higher levels of suppressor of cytokine signaling 3 (SOCS3) and protein phosphatase 2A (PP2A) suppressor compared with control cells. Knockdown of SOCS3 and PP2A restored IFN sensitivity. Moreover, HepG2/HBx cells showed higher phosphorylation levels of signal transducers and activators of transcription 3 and endoplasmic reticulum stress, which are inducers of SOCS3 and PP2A, respectively. Additionally, HBx‐knockdown restored IFN sensitivity in HepG2.2.15.7 cells. It was also confirmed that SOCS3 and PP2A expression levels were up‐regulated in the liver of patients with HBV infection. The results of this study demonstrated that HBx impairs IFN signaling via increased expression of SOCS3 and PP2A, a novel mechanistic insight, providing a potential therapeutic target to enhance the efficiency of IFN therapy. J. Med. Virol. 89:267–275, 2017.

A pivotal role of Krüppel-like factor 5 in regulation of cancer stem-like cells in hepatocellular carcinoma

In hepatocellular carcinoma (HCC), there exists a highly tumorigenic subset of cells defined by high expression of CD44 and CD133 that has been reported to contain cancer stem-like cells (CSCs). Krüppel-like factor 5 (KLF5) regulates many factors involved in cell cycle, migration, inflammation, angiogenesis and stemness and has cancer-promoting effects in some cancers. While some reports have indicated that KLF5 may have important roles in regulation of CSCs, what role, if any, KLF5 plays in regulation of CSCs in HCC remains to be elucidated. Flow cytometric analysis of CD44 and CD133 in HCC cell lines revealed subpopulations of CD44High/CD133High and CD44Low/CD133Low cells. We subsequently sorted these subpopulations and identified KLF5 as a gene that is significantly upregulated in CD44High/CD44High cells via RNA sequencing using next generation sequencing technology. Moreover, KLF5 overexpression enriched the CD44High/CD133High subpopulation and, consistent with the up-regulation of CD44High/CD133High cells, KLF5 overexpressing cells were more resistant to anti-cancer drugs and displayed enhanced colony-formation capacity. By contrast, knock-down of KLF5 by siRNA diminished the CD44High/CD133High subpopulation. When KLF5 was acetylated by TGF-β1, the KLF5-mediated CD44High/CD133High subpopulation enrichment was abrogated. Oppositely, ectopic expression of an acetylation-deficient KLF5 mutant further increased CD44High/CD133High subpopulations as compared to cell expressing wild-type KLF5. These findings provide novel mechanistic insight into a pivotal role for KLF5 in the regulation of CSCs in HCC.

Fibroblast growth factor-2–mediated FGFR/Erk signaling supports maintenance of cancer stem-like cells in esophageal squamous cell carcinoma

In esophageal squamous cell carcinoma (ESCC), a subset of cells defined by high expression of CD44 and low expression of CD24 has been reported to possess characteristics of cancer stem-like cells (CSCs). Novel therapies directly targeting CSCs have the potential to improve prognosis of ESCC patients. Although fibroblast growth factor-2 (FGF-2) expression correlates with recurrence and poor survival in ESCC patients, the role of FGF-2 in regulation of ESCC CSCs has yet to be elucidated. We report that FGF-2 is significantly upregulated in CSCs and significantly increases CSC content in ESCC cell lines by inducing epithelial-mesenchymal transition (EMT). Conversely, the FGFR inhibitor, AZD4547, sharply diminishes CSCs via induction of mesenchymal-epithelial transition. Further experiments revealed that MAPK/Erk kinase (Mek)/extracellular signal-regulated kinases (Erk) pathway is crucial for FGF-2-mediated CSC regulation. Pharmacological inhibition of FGF receptor (FGFR)-mediated signaling via AZD4547 did not affect CSCs in Ras mutated cells, implying that Mek/Erk pathway, downstream of FGFR signaling, might be an important regulator of CSCs. Indeed, the Mek inhibitor, trametinib, efficiently suppressed ESCC CSCs even in the context of Ras mutation. Consistent with these findings in vitro, xenotransplantation studies demonstrated that inhibition of FGF-2-mediated FGFR/Erk signaling significantly delayed tumor growth. Taken together, these findings indicate that FGF-2 is an essential factor regulating CSCs via Mek/Erk signaling in ESCC. Additionally, inhibition of FGFR and/or Mek signaling represents a potential novel therapeutic option for targeting CSCs in ESCC.

Anti-adipogenic and antiviral effects of l-carnitine on hepatitis C virus infection.

Hepatitis C virus (HCV) has been reported to hijack fatty acid metabolism in infected hepatocytes, taking advantage of lipid droplets for virus assembly. In this study, we analyzed the anti‐HCV activity of l‐carnitine, a substance involved in the transport of fatty acids into mitochondria. JFH‐1 or HCV replicon‐transfected Huh7.5.1 cells were treated with or without l‐carnitine to examine its anti‐HCV effects. The effects of l‐carnitine on HCV entry, HCV‐induced adipogenesis and lipid droplet formation, and HCV‐induced oxidative stress were examined. Treatment of JFH‐1‐infected cells with l‐carnitine inhibited HCV propagation in a concentration‐dependent manner. In contrast, l‐carnitine had no anti‐HCV activity in the HCV replicon system, which is lacking viral assembly. In addition, l‐carnitine did not affect HCV entry. However, l‐carnitine treatment decreased intracellular lipid droplets, which are crucial for HCV assembly in JFH‐1‐infected cells. The expression level of CPT‐1 was decreased in JFH‐1‐infected cells, and l‐carnitine treatment restored this expression. HCV‐infected cells exhibited increased production of reactive oxygen species and glutathione oxidation. l‐carnitine decreased oxidative stress induced by JFH‐1‐infection, as shown by glutathione/glutathione disulfide assays and MitoSOX staining. l‐carnitine exhibited anti‐HCV activity, possibly by inhibiting HCV assembly and through its anti‐adipogenic activity in HCV‐infected cells. Moreover, l‐carnitine has antioxidant properties in HCV‐infected hepatocytes. Overall, these results indicated that l‐carnitine may be an effective adjunctive agent in antiviral therapies to treat chronic hepatitis C. J. Med. Virol. 89:857–866, 2017.

Combination of neutrophil-to-lymphocyte ratio and early des-γ-carboxyprothrombin change ratio as a useful predictor of treatment response for hepatic arterial infusion chemotherapy against advanced hepatocellular carcinoma.

Hepatic arterial infusion chemotherapy (HAIC) is a potent therapeutic option for advanced hepatocellular carcinoma (HCC). However, there are few known predictive factors of treatment response to HAIC. We clarified the most accurate predictive factors early on in treatment.

159 KLF5 Promotes Tumorigenicity of Hepatocellular Carcinoma by Upregulation of Cancer Stem-Like Cells

Introduction: There exists a highly tumorigenic subset of hepatocellular carcinoma (HCC) cells defined by high expression of CD44 and CD133, and that subset has been reported to contain cancer stem-like cells (CSCs) in HCC. Kruppel-like factor 5 (KLF5) is a transcription factor containing 3 zinc finger domains and one transactivation domain. KLF5 regulates many factors related to cell cycle, migration, inflammation, angiogenesis and stemness and has cancer promoting effects in some cancers. Furthermore, some reports have indicated that KLF5 might have important roles in regulation of CSCs. However, the function of KLF5 in HCC remains to be elucidated. Functional roles of KLF5 in regulation of CSCs in HCC were examined in the present study. Methods: HCC and hepatoblastoma cell lines, Huh7, Alexander and HepG2 cells were analyzed. Anti-CD44 and anti-CD133 antibodies were used to detect CSCs in HCC by fluorescence-activated cell sorting (FACS). Indicated cell population was sorted by FACS Aria III (Becton Dickinson). MTS assay was carried out to determine sensitivity to chemotherapeutic reagents, 5FU and CDDP. RNA sequencing was performed by next generation sequencer, IonTM PGM (Lifetechnologies). Retroviral-mediated gene transfer was used to make a stable cell line overexpressing KLF5. Two independent sequences of siRNA against KLF5 were used to knock-down KLF5. Tumorigenicity was determined by soft-agar colony formation assay and xenograft experiments using athymic nude mice. Results: FACS showed heterogeneous cell population in several HCC cell lines. Sorted CD44High/CD133High cells were significantly more resistant to anti-cancer drugs, 5FU and CDDP, and had more colony forming capacity than CD44Low/CD133Low cells as reported previously. RNA sequencing revealed completely different gene expression profiles between CD44High/CD133High and CD44Low/CD133Low cells, and identified over 500 mRNAs, including KLF5, significantly up-regulated in the sorted CD44High/CD133High cells. Overexpression of KLF5 increased the ratio of CD44High/CD133High cells, and consistent with the upregulation of CD44High/CD133High cells, the KLF5 overexpressing cells were more resistant to the anti-cancer drugs and had more colony forming capacity. By contrast, knock-down of KLF5 by siRNA diminished CD44High/CD133High cell population. Finally, KLF5 overexpressing cells formed tumors more frequently in nude mice. Conclusion: Those data provide a novel mechanistic insight that KLF5 might promote tumorigenicity of HCC by upregulation of CSCs and could be a therapeutic target against CSCs in HCC.