Our previous study has shown that depolymerized holothurian glycosaminoglycan (DHG) has two different inhibitory activities in the blood coagulation cascade: heparin cofactor II-dependent thrombin inhibition; and antithrombin III- and heparin cofactor II-indepen-dent inhibition of the intrinsic factor Xase complex [Nagase et al. (1995) Blood 85,15271534]. In the present study, the effect of DHG on the activation of factor VIII and factor V by thrombin was examined with purified human components. DHG inhibited the activation of factor VIII by thrombin at concentrations exceeding 80 nM, but not the activation of factor V by thrombin at concentrations of up to 8 μM. On Western blot analysis, DHG inhibited the cleavage of factor VIII light chain at concentrations exceeding 0.8 μM. The interaction between DHG and factors VIII and V and thrombin was examined with a DHG-cellulofine column. DHG had strong affinity for factor V and thrombin, but slight affinity for factor VIII. The interaction of DHG with thrombin was analyzed, using fluorescein isothiocyan-ate-labeled DHG. One mole of DHG bound 2 mol of thrombin, with a dissociation constant (Kd) of 3.04 ×10−6 M. These results suggest that DHG interferes with the interaction between thrombin and factor VTII, probably by making a binary complex through the anionic binding exosite II of thrombin.
1384 Purpose: 5-Fluorouracil (5-FU) is one of the most effective an anticancer drugs used in chemotherapy against a variety of solid tumors. It exerts its anticancer effects through the inhibition of thymidylate synthase (TS) and the incorporation of its metabolites into RNA. 5-FU is phosphorylated and activated by three pathways involving orotate phosphoribosyltransferase (OPRT), uridine phosphorylase (UP), or thymidine phosphorylase (TP); however, the OPRT pathway is considered as the major phosphorylation pathway of 5-FU. In this study, to verify the role of OPRT in metabolism and cytotoxic function of 5-FU, we inhibited OPRT mRNA by using RNAi technology, and examined the effect of OPRT knockdown on the chemosensitivity of 5-FU in MIAPaCa-2 human pancreatic cancer cells and WiDr human colon cancer cells. Method: MIAPaCa-2 and WiDr cells were transfected with siRNA (final 33nM) using Lipofectamine 2000. At 24h following siRNA treatment, cells were re-seeded into 96-well plates. Then after overnight incubation, cells were treated with 5-FU or gemcitabine for 4 days and cell growth was determined by MTT assay. OPRT mRNA and protein were detected using one-step real time RT-PCR method and ELISA kit. TS inhibition rate was quantified by detection of ternary complex using Western blotting. The amount of 5-FU incorporated into RNA was detected using [6-14C] 5-FU. Result: Four siRNA sequences were designed for OPRT and the one with the highest efficiency was selected. In MIAPaCa-2 cells, the siRNA for OPRT showed a 90% and 70% inhibitory effect on the OPRT mRNA and protein, respectively. Furthermore, OPRT knockdown had no effect on cell proliferation and resulted in a 15-fold decrease in the sensitivity of the cells to 5-FU. In WiDr cells, the siRNA for OPRT showed an 80% inhibitory effect on OPRT mRNA, and OPRT knockdown resulted in a 4.5-fold decrease in the sensitivity of the cells to 5-FU. In both cell lines, OPRT inhibition did not affect the sensitivity of the cells to other antimetabolite such as gemcitabine which does not require phosphorylation by OPRT. Moreover, OPRT knockdown by using siRNA did not influence TS, dihydropyrimidine dehydrogenase (DPD), TP, and UP mRNA levels, indicating that these factors were not responsible for the decrease in 5-FU sensitivity. We also found that TS inhibition rate by 5-FU and the amount of 5-FU incorporated into RNA were markedly decreased by the RNAi-medicated downregulation of OPRT in MIAPaCa-2. Conclusion: These results suggest that 5-FU is mainly phosphorylated by OPRT pathway in these cell lines and OPRT is an important predictive factor of 5-FU sensitivity.
Trifluridine/tipiracil (FTD/TPI) (a.k.a. TAS-102) is a combination drug for metastatic colorectal cancer (CRC) and severely pretreated metastatic gastric/gastroesophageal junction (GEJ) cancers, comprising FTD, a thymidine-based antineoplastic nucleoside analog, and TPI, which enhances FTD bioavailability. Herein, in KRAS mutant murine colorectal cancer CT26 syngeneic models, we investigate whether combination therapy with DC101 (a surrogate ramucirumab antibody, rat antimouse vascular endothelial growth factor receptor (VEGFR)-2 monoclonal antibody (mAb)) improves FTD/TPI efficacy. Tumor growth inhibition (TGI) on day 15 was 38.0% and 30.6% upon DC101 monotherapy and FTD/TPI monotherapy respectively, and 60.3% upon combination therapy. Tumor volume was significantly lower (p < 0.001) upon combination treatment than upon FTD/TPI or DC101 monotherapy, indicating the additive effects of FTD/TPI and DC101. DNA-incorporated FTD levels on Day 8 were significantly higher in combination therapy with FTD/TPI (for 5 consecutive days) and DC101 (on alternate days for 7days) than in FTD/TPI monotherapy. Furthermore, vascular endothelial cell-specific marker CD31 was downregulated in DC101-treated tumors on day 8. These results indicate that combination therapy with FTD/TPI and DC101 is a promising treatment alternative regardless of KRAS mutations.
We studied the use of depolymerized holothurian glycosaminoglycan (DHG) as an anticoagulant in experimental beagle-dog hemodialysis using a hollow-fiber dialyzer compared to that using unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), and nafamostat mesilate (FUT). Effectiveness was based on 5 h hemodialysis and no marked clot deposition in the extracorporeal circuit. At effective doses, UFH and LMWH significantly prolonged template bleeding time, in sharp contrast to FUT and DHG, which scarcely prolonged bleeding time during hemodialysis. DHG prolonged activated partial thromboplastin time (APTT) about 6 times that of normal plasma and prolonged thrombin clotting time (TCT) markedly; FUT showed marked APTT prolongation but hardly prolonged TCT in the hemodialysis circuit at the effective dose. The anticoagulant profile of DHG thus differs completely from that of FUT. These results suggest that DHG may be useful as anticoagulant for hemodialysis with low hemorrhagic risk.
Summary A previous study in this laboratory showed that depolymerized holothurian glycosaminoglycan (DHG) has two different antithrombin III (ATIII)-independent inhibitory effects on the in vitro blood coagulation system: heparin cofactor II (HCII)-dependent inhibition of thrombin, and ATIII- and HCII-independent inhibition of factor X activation by factor IXa-factor Villa complex (Nagase et al. Blood 85, 1527-1534, 1995). In the present study, we compared the antithrombotic effects of DHG in normal and in ATIII-deficient mice with those of unfractionated heparin (UFH) and low molecular weight heparin (LMWH). DHG, unlike UFH and LMWH, exerted an in vivo antithrombotic effect even in mice with decreased plasma ATIII activity (about 30% of normal). We then compared the anticoagulant and antithrombotic effects of DHG in mice with those of high molecular weight (HMW)-DHG, low molecular weight (LMW)-DHG, and dermatan sulfate (DS). In terms of in vitro anticoagulant activity assessed by use of purified human components, DHGs (DHG, HMW-DHG, and LMW-DHG) had different anti-thrombin activity in the presence of HCII and anti-factor Xase activities, which differences were dependent on the molecular weight. With respect to in vivo antithrombotic activity, DHG, HMW-DHG, and LMW-DHG showed almost the same inhibitory effect on acute thromboembolism in mice (minimum effective dose [MED]: >0.3 mg/kg). Since the antithrombotic activities of DHGs were not correlated with the anticoagulant-specific activities, the contribution of the two anticoagulant activities to the in vivo antithrombotic effect of DHGs remains unknown. However, DHG was more effective against acute thromboembolism in mice than DS (MED >1 or >3 mg/kg), which showed no inhibitory activity toward factor Xase. Therefore, it seems that factor Xase inhibition contributes greatly to the antithrombotic effect of DHG and that DHG exerts this effect in mice mainly by inhibiting factor Xase.
Depolymerized holothurian glycosaminoglycan (DHG) is a glycosaminoglycan extracted from the sea cucumber Stichopus japonicus Selenka. In previous studies, we demonstrated that DHG has antithrombotic and anticoagulant activities that are distinguishable from those of heparin and dermatan sulfate. In the present study, we examined the effect of DHG on the tissue factor pathway inhibitor (TFPI), which inhibits the initial reaction of the tissue factor (TF)-mediated coagulation pathway. We first examined the effect of DHG on factor Xa inhibition by TFPI and the inhibition of TF-factor VIIa by TFPI-factor Xa in in vitro experiments using human purified proteins. DHG increased the rate of factor Xa inhibition by TFPI, which was abolished either with a synthetic C-terminal peptide or with a synthetic K3 domain peptide of TFPI. In contrast, DHG reduced the rate of TF-factor VIIa inhibition by TFPI-factor Xa. Therefore, the effect of DHG on in vitro activity of TFPI appears to be contradictory. We then examined the effect of DHG on TFPI in cynomolgus monkeys and compared it with that of unfractionated heparin. DHG induced an increase in the circulating level of free-form TFPI in plasma about 20-fold when administered i.v. at 1 mg/kg. The prothrombin time (PT) in monkey plasma after DHG administration was longer than that estimated from the plasma concentrations of DHG. Therefore, free-form TFPI released by DHG seems to play an additive role in the anticoagulant mechanisms of DHG through the extrinsic pathway in vivo. From the results shown in the present work and in previous studies, we conclude that DHG shows anticoagulant activity at various stages of coagulation reactions, i.e., by inhibiting the initial reaction of the extrinsic pathway, by inhibiting the intrinsic Xase, and by inhibiting thrombin.
Aromatase inhibitor (AI) is widely used as an endocrine treatment in postmenopausal patients with hormone receptor-positive breast cancer. To identify useful prognostic factors for patients with metastatic breast cancer treated with AI therapy, we investigated the association between several hormone receptor-related factors and prognosis. The expressions of estrogen receptor-α (ERα), ERβ, progesterone receptor, the phosphorylation of ERα serine 118 (Ser118) and ERα Ser167 were examined using immunohistochemical techniques for the primary tumors of 41 patients with metastatic breast cancer who received first-line AI therapy after relapse. To assess the associations of protein expression and phosphorylation levels with progression-free survival (PFS), the levels of each factor were categorized into low and high values at optimal cutoff points. In univariate analysis, high ERα expression and high ERα Ser167 phosphorylation correlated with longer PFS (p = 0.016 and 0.013, respectively). In multivariate analysis, low ERβ expression and high ERα Ser167 phosphorylation correlated with longer PFS (p = 0.031 and 0.004, respectively). Patients with both low ERβ expression and high ERα Ser167 phosphorylation had longer PFS than the others (p = 0.0107). These data suggest that the expression of ERβ and phosphorylation of ERα Ser167 may be useful prognostic factors in patients with metastatic breast cancer who received first-line AI therapy.
To identify the genes and clinical parameters associated with efficacy of uracil and tegafur/leucovorin (UFT/LV) chemotherapy in colorectal cancer (CRC), we compared the levels of reduced folate in tumors between patients receiving LV and those not receiving LV (study I), and explored the changes in the expression levels of 14 genes after two weeks of UFT/LV chemotherapy in 73 patients with CRC (study II). In study I, the reduced folate levels after LV administration were approximately 3-fold higher than those without LV administration in patients with right-sided tumors or aged >75 years old (p=0.019). In study II, the reduction in γ-glutamyl hydrolase (GGH) expression in responders and in patients with right-sided tumors or aged >75 years old was significantly greater than that in non-responders (p<0.001) and in other patients, respectively (p=0.003). Increase of reduced folate and reduction in GGH expression were associated with response to UFT/LV chemotherapy in patients with right-sided tumors or aged >75 years old.
The aim of the study was to identify biomarkers capable of predicting response to preoperative chemoradiotherapy (CRT) including S-1 or UFT for rectal cancer using biopsy specimens obtained before CRT (Pre-samples) and 7 days after the start of CRT (Day-7 samples).Preoperative CRT including S-1 or UFT was performed in 82 patients with locally advanced rectal cancer. The expression levels of 18 genes related to 5-fluorouracil, folate, and radiation in the Pre-samples and the Day-7 samples were evaluated using reverse transcription polymerase chain reaction (RT-PCR) assay.The gene expression levels of hypoxia inducible factor 1 alpha subunit (HIF1A), dihydropyrimidine dehydrogenase (DPYD) and thymidine phosphorylase (TYMP) were found significantly increased in Day-7 samples compared to Pre-samples in responders, but not in non-responders.Increases in gene expression levels of TYMP, DPYD, and HIF1A in tumor tissues at 7 days after the start of CRT may be useful for predicting the efficacy of CRT including S-1 or UFT.
