Ken-ichi Ito

A naturally occurring mutation in MRP1 results in a selective decrease in organic anion transport and in increased doxorubicin resistance.

The human 190 kDa multidrug resistance protein, MRP1, is a polytopic membrane glycoprotein that confers resistance to a wide range of chemotherapeutic agents. It also transports structurally diverse conjugated organic anions, as well as certain unconjugated and conjugated compounds, in a reduced glutathione-stimulated manner. In this study, we characterized a low-frequency (<1%) naturally occurring mutation in MRP1 expected to cause the substitution of a conserved arginine with serine at position 433 in a predicted cytoplasmic loop of the protein. Transport experiments with membrane vesicles prepared from transfected human embryonic kidney cells and HeLa cells revealed a two-fold reduction in the ATP-dependent transport of the MRP1 substrates, leukotriene C4 (LTC4) and oestrone sulphate. Kinetic analysis showed that this reduction was due to a decrease in Vmax for both substrates but Km was unchanged. In contrast, 17beta-oestradiol-17beta-(D-glucuronide) transport by the Arg433Ser mutant MRP1 was similar to that by wild-type MRP1. Fluorescence confocal microscopy showed that the mutant MRP1 was routed correctly to the plasma membrane. In contrast to the reduced LTC4 and oestrone sulphate transport, stably transfected HeLa cells expressing Arg433Ser mutant MRP1 were 2.1-fold more resistant to doxorubicin than cells expressing wild-type MRP1, while resistance to VP-16 and vincristine was unchanged. These results provide the first example of a naturally occurring mutation predicted to result in an amino acid substitution in a cytoplasmic region of MRP1 that shows an altered phenotype with respect to both conjugated organic anion transport and drug resistance.

Identification of human multidrug resistance protein 1 (MRP1) mutations and characterization of a G671V substitution

AbstractThe multidrug resistance protein 1 (MRP1) belonging to the ATP-binding cassette (ABC) superfamily of transport proteins can confer resistance to multiple natural product drugs and methotrexate in human tumor cells. In addition, MRP1 is expressed in normal tissues acting as an efflux pump for glutathione, glucuronate, and sulfate conjugates and may thus influence the pharmacokinetic properties of many drugs. Using polymerase chain reaction-single-strand conformation polymorphism analysis, we screened 36 Caucasian volunteers for mutations in the coding exons of the MRP1 gene, including the adjacent intron sequences. Among several mutations found, two are expected to cause amino acid substitutions. One of these mutations (G671V) was of special interest because it is located near the first nucleotide binding domain. To determine whether this mutation caused a change in the MRP1 phenotype, a mutant MRP1 expression vector was constructed and transfected into SV40-transformed human embryonic kidney cells (HEKSV293T) and the transport properties of the mutant protein were examined. Transport of the MRP1 substrates leukotriene C4, 17β-estradiol 17β-(D)-glucuronide, and estrone sulfate by membrane vesicles prepared from transiently transfected HEKSV293T cells was comparable to that of wild-type MRP1.

Endoscopic measurement of papillary sphincter zone and pancreatic main ductal pressure in patients with chronic pancreatitis.

To determine the significance of manometric pressure of the pancreatic duct, we used a microtransducer inserted through a duodenoscope to measure pressures in the papillary sphincter zone and pancreatic main duct in 20 control subjects and 20 patients with chronic pancreatitis, and recorded the effect of exogenous glucagon or secretin. There was no significant difference between control subjects and patients with chronic pancreatitis without papillitis in the motility of the sphincter of Oddi. The pancreatic main ductal pressure was significantly higher in the patients with chronic pancreatitis (54.5 +/- 29.9 mmHg) than in the control subjects (16.2 +/- 8.7 mmHg). The viscosity of pure pancreatic juice of patients with chronic pancreatitis [5.8 centipoise (cp)] in the basal secretory state was significantly higher than that of the control subjects (1.61 cp). These data lead to the hypothesis that increased pancreatic ductal pressure in patients with chronic pancreatitis without papillitis is due not to papillary dysfunction, but to increased viscosity or other unknown factors.

Suppression of acute and chronic rejection by hepatocyte growth factor in a murine model of cardiac transplantation: Induction of tolerance and prevention of cardiac allograft vasculopathy

Background—Although treatment with immunosuppressive agents has contributed to overcoming acute rejection and improving the midterm survival of transplanted hearts, cardiac allograft vasculopathy (CAV) has remained the main cause of primary graft failure. Recent approaches have shown that hepatocyte growth factor (HGF) exhibits cardiotrophic functions. We therefore addressed whether HGF would regulate acute and chronic rejection in cardiac transplantation. Methods and Results—We used a murine heterotopic cardiac transplantation model between fully incompatible strains and administered 500 &mgr;g · kg−1 · d−1 HGF during the initial 14 days after transplantation. The HGF-treated allografts showed significantly prolonged survival (42.3±4.1 days, P<0.001) compared with the controls (11.1±0.6 days), with tolerance induction in 47.4%. Histopathologically, the number of infiltrating cells was significantly decreased and myocardial necrosis was less prominent with a reduction of apoptosis in the allografts by HGF treatment during acute rejection. In the long-term surviving allografts, HGF significantly inhibited the development of CAV and interstitial fibrosis. With respect to intragraft cytokine mRNA expression, HGF treatment reduced the early expression of interferon-&ggr; and enhanced the expression of transforming growth factor-&bgr;1 during the acute phase and of interleukin-10 continuously through the acute phase to the chronic phase. Conclusions—Our findings demonstrate that HGF can prolong the survival of allografts by its cardioprotective and immunomodulative potencies. Thus, HGF administration may constitute a new therapeutic approach to preventing cardiac graft failure that has not been overcome by conventional immunosuppressive agents.

Increased nuclear localization of transcription factor Y-box binding protein 1 accompanied by up-regulation of P-glycoprotein in breast cancer pretreated with paclitaxel.

Purpose: The Y-box binding protein 1 (YB-1) regulates expression of P-glycoprotein encoded by the MDR1 gene. There have been no previous studies regarding the involvement of YB-1 in the development of resistance to paclitaxel. The present study was done to examine how paclitaxel affects the localization and expression of YB-1 in breast cancer. Experimental Design: We evaluated the expression and localization of YB-1 and P-glycoprotein in breast cancer tissues obtained from 27 patients before and after treatment with paclitaxel. The effect of paclitaxel on localization of cellular YB-1 was examined by using GFP-YB-1. Interaction of YB-1 with the Y-box motif of the MDR1 promoters was studied by electrophoretic mobility shift assay. The effects of paclitaxel on MDR1 promoter activity were examined by luciferase assay. Results: Of 27 breast cancer tissues treated with paclitaxel, nine (33%) showed translocation of YB-1 from the cytoplasm to the nucleus together with increased expression of P-glycoprotein during the course of treatment. Twelve breast cancer tissues (44%) showed neither translocation of YB-1 nor increased expression of P-glycoprotein. Nuclear translocation of YB-1 was correlated significantly with increased expression of P-glycoprotein (P = 0.0037). Confocal analysis indicated that paclitaxel induced nuclear translocation of green fluorescent fused YB-1 in MCF7 cells. Furthermore, binding of YB-1 to the Y-box of MDR1 promoter was increased in response to treatment with paclitaxel. In addition, MDR1 promoter activity was significantly up-regulated by paclitaxel in MCF7 cells (P < 0.001). Conclusions: The results of the present study suggested that YB-1 may be involved in the development of resistance to paclitaxel in breast cancer.

Involvement of vascular endothelial growth factor and urokinase-type plasminogen activator receptor in microvessel invasion in human colorectal cancers.

To evaluate the association among known angiogenic growth factors or factors related to the plasminogen activation system and clinicopathological factors in patients with colorectal cancer, we examined the expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), transforming growth factor‐α (TGF‐α), urokinase‐type plasminogen activator (u‐PA), u‐PA receptor (u‐PA‐R) and plasminogen activator inhibitor‐1 (PAI‐1) in clinical specimens of colorectal cancers by Northern blot analysis. In comparison with the expression of these angiogenesis‐related genes in 7 paired samples of colorectal cancers and the adjacent normal mucosa, VEGF mRNA level was significantly higher in the cancer tissues than in the adjacent normal mucosa (p < 0.05). We analyzed expression of these genes in 44 cases of primary colorectal cancers. Among the 3 angiogenic growth factors we examined, VEGF mRNA expression was significantly higher in the cancer tissues with blood vessel invasion or with lymphatic vessel invasion than in those without, respectively (p < 0.05). On the other hand, u‐PA‐R mRNA expression was significantly higher in the cancers with blood vessel invasion than in those without (p < 0.05). In addition, there was a correlation between the expression levels of VEGF and u‐PA‐R mRNA in the cancer tissues we have examined. Using immunohistochemistry, strong staining of VEGF or u‐PA‐R was observed in the cancer cells invading the microvessels. Our findings suggest that malignant transformation might accompany the upregulation of VEGF expression in colorectal cancers and that VEGF and u‐PA‐R might contribute cooperatively to increase angiogenesis around the tumor as well as the metastasis via microvessels. Int. J. Cancer (Pred. Oncol.) 79:179–186, 1998.© 1998 Wiley‐Liss, Inc.

Augmentation of vessel squeezing at coronary-myocardial bridge by nitroglycerin: Study by quantitative coronary angiography and intravascular ultrasound☆☆☆★★★

BACKGROUND Nitroglycerin is known to augment vessel wall squeezing at the site with coronary-myocardial bridging (CMB). This study was designed to define the mechanism of nitroglycerin-induced augmentation of CMB in clinical settings. METHODS We analyzed nitroglycerin reactivity at the site with CMB in 39 patients. Maximal and minimal diameters of CMB during a cardiac cycle were measured by quantitative angiography before and after intracoronary administration of 250 microgram nitroglycerin. In 15 patients, CMB sites were observed by intravascular ultrasound to determine the intimal thickness and the time-serial change in vessel area. RESULTS Before nitroglycerin, CMB was demonstrated with angiography in 25 patients, and the remaining 14 patients showed CMB after nitroglycerin. The maximal diameter during diastole increased from 1. 4 +/- 0.4 mm to 1.9 +/- 0.4 mm after nitroglycerin, whereas the minimal diameter during systole decreased from 1.0 +/- 0.4 mm to 0.7 +/- 0.4 mm (P <.01). Thus nitroglycerin augmented the percent vessel narrowing during systole from 24% +/- 21% to 65% +/- 16% (P <.01). Under these conditions, intravascular ultrasound showed the reduction of the cross-sectional area of the sites with CMB by -38% +/- 16% (P <.01) during systole, and this phenomenon continued to early diastole (-30% +/- 16%). The intimal thickness was 0.32 +/- 0. 10 mm, which suggests the absence of atherosclerotic disease at CMB sites. CONCLUSIONS These results indicate that nitroglycerin-induced augmentation of the percent narrowing of CMB can be derived from further systolic compression of the vessel lumen as well as diastolic expansion, probably because of the increase in vessel compliance after nitroglycerin. We suggest that the delayed dilation of coronary lumen during the early diastole may contribute to the occurrence of myocardial ischemia.

Mast cell tryptase and photoaging: possible involvement in the degradation of extra cellular matrix and basement membrane proteins

Mast cells are widely distributed in the connective tissue of the body, but are particularly prominent in tissues such as skin. An increased number of mast cells can be found in the dermis under inflammatory conditions and ultraviolet (UV) exposed skin. Previous investigations have identified matrix metalloproteinases (MMPs) as key enzymes in the degradation of extra cellular matrix (ECM). This study reports about the potential contribution of human mast cell tryptase as a new triggering enzyme in matrix degradation process. Recent studies suggest that mast cell-derived proteases can activate MMPs. We investigated both the degradation of cellular matrix components and activation of MMPs by human tryptase. Mast cells are increased in photoaged skin and the increase of mast cell tryptase in UV irradiated skin was confirmed. Human mast cell tryptase was purified from human tonsils by a series of standard chromatographic procedures. Degradation of collagen type I was achieved by incubation of human type I collagen with tryptase and the fragments were quantified by SDS-PAGE and staining with Coomassie Brilliant Blue 250-R (CBB). Treatment with tryptase resulted in the activation of proMMP-9 as revealed by gelatinolytic activity in type IV collagen zymography. When tryptase was incubated with human type IV collagen, gradual degradation of intact collagen was detected by Western blotting. Furthermore, type IV collagen degradation was observed in the basement membrane (BM) of a three-dimensional (3D) skin model. Degranulation of mast cells, which release tryptase, can activate MMPs and causes direct damage to ECM proteins. These findings strongly implicate that tryptase either alone or in conjunction with activation of MMPs, can participate in ECM damage and the possible destruction of BM leading to photoaging.

Genetically engineered Bifidobacterium longum for tumor‐targeting enzyme‐prodrug therapy of autochthonous mammary tumors in rats

A fundamental obstacle in systemic therapy for cancer patients is the specific targeting of therapy directly to solid tumors. A strain of the domestic bacterium Bifidobacterium longum, which is non‐pathogenic and anaerobic, showed selective localization to and proliferation within solid tumors after systemic application. Here, we propose a novel approach to cancer gene therapy in which anaerobic and non‐pathogenic bacteria of the genus B. longum are used to achieve tumor‐specific gene delivery and enzyme‐prodrug therapy. We constructed a plasmid, pBLES100‐S‐eCD, which included eCD. Transfected B. longum produced CD in hypoxic tumors and achieved tumor site‐specific conversion of 5‐FC to 5‐FU. Furthermore, we demonstrated antitumor efficacy in rat bearing autochthonous mammary tumors injected with the transfected B. longum directly or intravenously. This method was confirmed to be effective for enzyme‐prodrug therapy not only by intratumoral injection but also by systemic administration. To estimate the toxicity of this bacterial vector, the systemic immunogenicity was evaluated by ASA reaction and the anaphylactic activity of IgG was evaluated by PCA reaction in guinea pigs. In the ASA reaction, no anaphylaxis symptoms were observed in any immunized guinea pigs injected with transfected B. longum. In the PCA reaction, B. longum/S‐eCD specific‐PCA‐induced antibody was not detected. Thus, we proposed that anaerobic bacteria of the genus B. longum were an attractive and safe tumor‐targeting vector and transfected B. longum was a potential anticancer agent that could effectively and specifically treat solid tumors. (Cancer Sci 2006; 97: 649–657)

Multimodality therapeutic outcomes In anaplastic thyroid carcinoma: Improved survival in subgroups of patients with localized primary tumors

The aim of the present study was to investigate the role of a multimodality treatment for anaplastic thyroid carcinoma (ATC).