Yohei Arihara

RNAi-mediated gene silencing of ST6GalNAc I suppresses the metastatic potential in gastric cancer cells

BackgroundST6GalNAc I is a sialyltransferase controlling the expression of sialyl-Tn antigen (STn), which is overexpressed in several epithelial cancers, including gastric cancer, and is highly correlated with cancer metastasis. However, the functional contribution of ST6GalNAc I to development or progression of gastric cancer remains unclear. In this study, we investigated the effects of suppression of ST6GalNAc I on gastric cancer in vitro and in vivo.MethodsGastric cancer cell lines were transfected with ST6GalNAc I siRNA and were examined by cell proliferation, migration, and invasion assays. We also evaluated the effect of ST6GalNAc I siRNA treatment in a peritoneal dissemination mouse model. The differences in mRNA levels of selected signaling molecules were analyzed by polymerase chain reaction (PCR) arrays associated with tumor metastasis in MKN45 cells. The signal transducer and activator of transcription 5b (STAT5b) signaling pathways that reportedly regulate the insulin-like growth factor-1 (IGF-1) were analyzed by Western blot.ResultsST6GalNAc I siRNA inhibited gastric cancer cell growth, migration, and invasion in vitro. Furthermore, intraperitoneal administration of ST6GalNAc I siRNA- liposome significantly inhibited peritoneal dissemination and prolonged the survival of xenograft model mice with peritoneal dissemination of gastric cancer. PCR array confirmed that suppression of ST6GalNAc I caused a significant reduction in expression of IGF-1 mRNA. Decreased IGF-1 expression in MKN45 cells treated with ST6GalNAc I siRNA was accompanied by reduced phosphorylation of STAT5b.ConclusionST6GalNAc I may regulate the gene expression of IGF-1 through STAT5b activation in gastric cancer cells and may be a potential target for treatment of metastasizing gastric cancer.

Activated p53 with Histone Deacetylase Inhibitor Enhances L-Fucose-Mediated Drug Delivery through Induction of Fucosyltransferase 8 Expression in Hepatocellular Carcinoma Cells.

Background The prognosis of advanced hepatocellular carcinoma (HCC) is dismal, underscoring the need for novel effective treatments. The α1,6-fucosyltransferase (fucosyltransferase 8, FUT8) has been reported to accelerate malignant potential in HCC. Our study aimed to investigate the regulation of FUT8 expression by p53 and develop a novel therapeutic strategy for targeting HCC cells using L-fucose-mediated drug delivery. Methods Binding sites for p53 were searched for within the FUT8 promoter region. FUT8 expression was assessed by immunoblotting. Chromatin immunoprecipitation (ChIP) assays were performed to analyze p53 binding to the FUT8 promoter. The delivery of Cy5.5-encapsulated L-fucose-liposomes (Fuc-Lip-Cy5.5) to a Lens Culinaris agglutinin-reactive fraction of α-fetoprotein (AFP-L3)-expressing HCC cells was analyzed by flow cytometry. The induction of FUT8 by histone deacetylase inhibitor (HDACi) -inducing acetylated -p53 was evaluated by immunoblotting. Flow cytometric analysis was performed to assess whether the activation of p53 by HDACi affected the uptake of Fuc-Lip-Cy5.5 by HCC cells. The cytotoxicity of an L-fucose-bound liposome carrying sorafenib (Fuc-Lip-sorafenib) with HDACi was assessed in vivo and in vitro. Results The knock down of p53 with siRNA led to decreased FUT8 expression. ChIP assays revealed p53 binds to the FUT8 promoter region. Flow cytometric analyses demonstrated the specific uptake of Fuc-Lip-Cy5.5 into AFP-L3-expressing HCC cells in a p53- and FUT8-dependent manner. HDACi upregulated the uptake of Fuc-Lip-Cy5.5 by HCC cells by increasing FUT8 via acetylated -p53. The addition of a HDACi increased apoptosis induced by Fuc-Lip-sorafenib in HCC cells. Conclusions Our findings reveal that FUT8 is a p53 target gene and suggest that p53 activated by HDACi induces Fuc-Lip-sorafenib uptake by HCC cells, highlighting this pathway as a promising therapeutic intervention for HCC.

The iron chelator deferasirox induces apoptosis by targeting oncogenic Pyk2/β-catenin signaling in human multiple myeloma

Deregulated iron metabolism underlies the pathogenesis of many human cancers. Recently, low expression of ferroportin, which is the only identified non-heme iron exporter, has been associated with significantly reduced overall survival in multiple myeloma (MM); however, the altered iron metabolism in MM biology remains unclear. In this study we demonstrated, by live cell imaging, that MM cells have increased intracellular iron levels as compared with normal cells. In experiments to test the effect of iron chelation on the growth of MM cells, we found that deferasirox (DFX), an oral iron chelator used to treat iron overload in clinical practice, inhibits MM cell growth both in vivo and in vitro. Mechanistically, DFX was found to induce apoptosis of MM cells via the inhibition of proline-rich tyrosine kinase 2 (Pyk2), which is known to promote tumor growth in MM. Inhibition of Pyk2 is caused by the suppression of reactive oxygen species, and leads to downregulation of the Wnt/β-catenin signaling pathway. Taken together, our findings indicate that high levels of intracellular iron, which might be due to low ferroportin expression, play a role in MM pathophysiology. Therefore, DFX may provide a therapeutic option for MM that is driven by deregulated iron homeostasis and/or Pyk2/Wnt signaling.

Relationship Between Increased Fucosylation and Metastatic Potential in Colorectal Cancer

BACKGROUND Fucose is utilized for the modification of different molecules involved in blood group determination, immunological reactions, and signal transduction pathways. We have recently reported that enhanced activity of the fucosyltransferase 3 and/or 6 promoted TGF-ß-mediated epithelial mesenchymal transition and was associated with increased metastatic potential of colorectal cancer (CRC), suggesting that fucose is required by CRC cells. With this in mind, we examined requirement of L-fucose in CRC cells and developed fucose-bound nanoparticles as vehicles for delivery of anticancer drugs specific to CRC. METHODS In this study, we first examined the expression of fucosylated proteins in 50 cases of CRC by immunochistochemical staining with biotinylated Aleuria aurantia lectin (AAL). Then we carried out an L-fucose uptake assay using three CRC cell lines. Finally, we developed fucose-bound nanoparticles as vehicles for the delivery of an anticancer drug, SN38, and examined tumor growth inhibition in mouse xenograft model (n = 6 mice per group). All statistical tests were two-sided. RESULTS We found a statistically significant relationship between vascular invasion, clinical stage, and intensity score of AAL staining (P≤ .02). L-fucose uptake assay revealed that L-fucose incorporation, as well as fucosylated protein release, was high in cells rich in fucosylated proteins. L-fucose-bound liposomes effectively delivered Cy5.5 into CRC cells. The excess of L-fucose decreased the efficiency of Cy5.5 uptake through L-fucose-bound liposomes, suggesting an L-fucose receptor dependency. Intravenously injected, L-fucose-bound liposomes carrying SN38 were successfully delivered to CRC cells, mediating efficient tumor growth inhibition (relative tumor growth ratio: no treatment group [NT], 8.29 ± 3.09; SN38-treated group [SN38], 3.53 ± 1.47; liposome-carrying, SN38-treated group [F0], 3.1 ± 1.39; L-fucose-bound, liposome-carrying, SN38-treated group [F50], 0.94 ± 0.89; F50 vs NT,P= .003; F50 vs SN38,P= .02, F50 vs F0,P= .04), as well as prolonging survival of mouse xenograft models (log-rank test,P< .001). CONCLUSIONS Thus, fucose-bound liposomes carrying anticancer drugs provide a new strategy for the treatment of CRC patients.

Small molecule CP-31398 induces reactive oxygen species-dependent apoptosis in human multiple myeloma

Reactive oxygen species (ROS) are normal byproducts of a wide variety of cellular processes. ROS have dual functional roles in cancer cell pathophysiology. At low to moderate levels, ROS act as signaling transducers to activate cell proliferation, migration, invasion, and angiogenesis. In contrast, high levels of ROS induce cell death. In multiple myeloma (MM), ROS overproduction is the trigger for apoptosis induced by several anticancer compounds, including proteasome inhibitors. However, no drugs for which oxidative stress is the main mechanism of action are currently used for treatment of MM in clinical situations. In this study, we demonstrate that the p53-activating small molecule CP-31398 (CP) effectively inhibits the growth of MM cell lines and primary MM isolates from patients. CP also suppresses the growth of MM xenografts in mice. Mechanistically, CP was found to induce intrinsic apoptosis in MM cells via increasing ROS production. Interestingly, CP-induced apoptosis occurs regardless of the p53 status, suggesting that CP has additional mechanisms of action. Our findings thus indicate that CP could be an attractive candidate for treatment of MM patients harboring p53 abnormalities; this satisfies an unmet clinical need, as such individuals currently have a poor prognosis.Reactive oxygen species (ROS) are normal byproducts of a wide variety of cellular processes. ROS have dual functional roles in cancer cell pathophysiology. At low to moderate levels, ROS act as signaling transducers to activate cell proliferation, migration, invasion, and angiogenesis. In contrast, high levels of ROS induce cell death. In multiple myeloma (MM), ROS overproduction is the trigger for apoptosis induced by several anticancer compounds, including proteasome inhibitors. However, no drugs for which oxidative stress is the main mechanism of action are currently used for treatment of MM in clinical situations. In this study, we demonstrate that the p53-activating small molecule CP-31398 (CP) effectively inhibits the growth of MM cell lines and primary MM isolates from patients. CP also suppresses the growth of MM xenografts in mice. Mechanistically, CP was found to induce intrinsic apoptosis in MM cells via increasing ROS production. Interestingly, CP-induced apoptosis occurs regardless of the p53 status, suggesting that CP has additional mechanisms of action. Our findings thus indicate that CP could be an attractive candidate for treatment of MM patients harboring p53 abnormalities; this satisfies an unmet clinical need, as such individuals currently have a poor prognosis.

Targeting Notch-1 positive acute leukemia cells by novel fucose-bound liposomes carrying daunorubicin.

Complete remission by induction therapy in acute myelogenous leukemia (AML) can be achieved due to improvements in supportive and optimized therapy. However, more than 20% of patients will still need to undergo salvage therapy, and most will have a poor prognosis. Determining the specificity of drugs to leukemia cells is important since this will maximize the dose of chemotherapeutic agents that can be administered to AML patients. In turn, this would be expected to lead to reduced drug toxicity and its increased efficacy. We targeted Notch-1 positive AML cells utilizing fucose-bound liposomes, since activation of Notch-1 is required for O-fucosylation. Herein, we report that intravenously injected, L-fucose-bound liposomes containing daunorubicin can be successfully delivered to AML cells that express fucosylated antigens. This resulted in efficient tumor growth inhibition in tumor-bearing mice and decreased proliferation of AML patient-derived leukemia cells. Thus, biological targeting by fucose-bound liposomes that takes advantage of the intrinsic characteristics of AML cells could be a promising new strategy for Notch-1 positive-AML treatment.

Abstract 2112: FoxO3a activation by HDAC class IIa inhibition induces cell cycle arrest in pancreatic cancer cells

Pancreatic cancer is highly chemo-resistant associated with oncogenic mutations such as KRAS and/or p53. The effect of conventional chemotherapy is not sufficient and new target and strategy is urgently needed. The forkhead box (Fox) proteins are multidirectional transcriptional factors strongly implicated in malignancies. Although Fox O (FoxO) protein, and particularly FoxO3a, works as negative regulator of cell proliferation by repressing cyclin proteins and inducing cell cycle inhibitors such as p21Waf1/Cip1, its expression is consistently suppressed by several oncogenic pathways including phosphatidylinositol-3 kinase (PI3K) / AKT pathway, constitutively activated in pancreatic cancer. Thus, upregulating FoxO3a activity could be a promising target of pancreatic cancer treatment without impact of underlying oncogenic mutations. Class IIa Histone deacetylase (HDAC) is a subgroup of HDAC. Though HDAC inhibitors (HDACi) have been extensively investigated as a cancer target, its action mechanism is considered due to histone modification by class I. Biological significance of class IIa HDACs which have minimal histone deacetylation activity have not been elucidated yet. Recent studies show class IIa HDACs act as a transcriptional regulator including FoxO3a. In this study, we investigate the biologic impact of HDAC class IIa inhibition on FoxO3a and anti-tumor effect against pancreatic cancer cell line using selective class IIa HDACi TMP269. TMP269 treatment showed increased FoxO3a expression in a dose dependent manner with immunoblotting and modest cell growth inhibition effect at 57.5 μM of IC50 dose for 48-hour treatment against AsPC-1 in MTT. G1/S arrest was observed with cell cycle assay. Upregulated p21Waf1/Cip1 and downregulated CDK2 and 4/6 and cyclin D1 and D2 expressions were further observed, consistent with inducing G1/S arrest and transcriptionally activated FoxO3a. Importantly, upregulated p21Waf1/Cip1 was observed in AsPC-1 p53 null cell line, suggesting independent with p53 pathway. These findings suggest upregulated FoxO3a induced by HDAC class IIa inhibition activated its transcription and resulted in cell growth inhibition. Because PI3K/AKT leads FoxO3a to the ubiquitylation-mediated proteasome degradation, we examined irreversible proteasome inhibitor carfilzomib (CFZ) combined with TMP269, aiming synergistic FoxO3a upregulating. As expected, FoxO3a expression was further increased in TMP269 combined with CFZ compared with TMP269 or CFZ alone. Following the activated FoxO3a, p21Waf1/Cip1 expression was upregulated and cell growth inhibition was dramatically enhanced. In conclusion, HDAC class IIa inhibition modified FoxO3a transcriptional activation and upregulating FoxO3 by dual inhibition of HDAC class IIa and proteasome is promising target against pancreas cancer. Citation Format: Makoto Usami, Shohei Kikuchi, Kohichi Takada, Yusuke Sugama, Yohei Arihara, Naotaka Hayasaka, Hajime Nakamura, Yuki Ikeda, Yusuke Kamihara, Masahiro Hirakawa, Makoto Yoshida, Masayoshi Kobune, Koji Miyanishi, Junji Kato. FoxO3a activation by HDAC class IIa inhibition induces cell cycle arrest in pancreatic cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2112. doi:10.1158/1538-7445.AM2017-2112

Tu1967 Accumulation of L-Fucose Is a Functional Target for Colorectal Cancer Therapy

Background MK-2206, a novel Akt inhibitor, has shown anticancer effect in many types of cancers, but its effect in gastric cancer was unclear. We aimed to investigate the anticancer effect of MK-2206 in gastric cancer cells. Method Gastric cancer cell lines (SGC7901 and MKN45) were used in this study. The effect of MK-2206 on cell proliferation was determined by cell viability assays and colony formation assays. Apoptosis in SGC-7901 cells treated with MK-2206 was analyzed by flow cytometry. The interactions between MK2206 and other chemotherapeutics were determined by calculating the combination index (CI) based on the Talalay-Chou equation. The expression levels of Akt/pAkt, caspase-3/ caspase-7/caspase-9, PARP, cleaved caspase-3/caspase-7/caspase-9, and cleaved PARP were determined by western blot analysis in circumstances with treatment of chemotherapeutics alone or combined with MK-2206. Results Cell viability assays and colony formation assays showed that MK-2206 could effectively inhibit the proliferation of SGC-7901 and MKN45 cells. The cytotoxicity of MK-2206 increased when gastric cancer cells were treated with