The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease

CONTEXT

Acute aortic dissection is a life-threatening medical emergency associated with high rates of morbidity and mortality. Data are limited regarding the effect of recent imaging and therapeutic advances on patient care and outcomes in this setting.

OBJECTIVE

To assess the presentation, management, and outcomes of acute aortic dissection.

DESIGN

Case series with patients enrolled between January 1996 and December 1998. Data were collected at presentation and by physician review of hospital records.

SETTING

The International Registry of Acute Aortic Dissection, consisting of 12 international referral centers.

PARTICIPANTS

A total of 464 patients (mean age, 63 years; 65.3% male), 62.3% of whom had type A dissection.

MAIN OUTCOME MEASURES

Presenting history, physical findings, management, and mortality, as assessed by history and physician review of hospital records.

RESULTS

While sudden onset of severe sharp pain was the single most common presenting complaint, the clinical presentation was diverse. Classic physical findings such as aortic regurgitation and pulse deficit were noted in only 31.6% and 15.1% of patients, respectively, and initial chest radiograph and electrocardiogram were frequently not helpful (no abnormalities were noted in 12.4% and 31.3% of patients, respectively). Computed tomography was the initial imaging modality used in 61.1%. Overall in-hospital mortality was 27.4%. Mortality of patients with type A dissection managed surgically was 26%; among those not receiving surgery (typically because of advanced age and comorbidity), mortality was 58%. Mortality of patients with type B dissection treated medically was 10.7%. Surgery was performed in 20% of patients with type B dissection; mortality in this group was 31.4%.

CONCLUSIONS

Acute aortic dissection presents with a wide range of manifestations, and classic findings are often absent. A high clinical index of suspicion is necessary. Despite recent advances, in-hospital mortality rates remain high. Our data support the need for continued improvement in prevention, diagnosis, and management of acute aortic dissection.

Familial Parkinson disease gene product, parkin, is a ubiquitin-protein ligase

Autosomal recessive juvenile parkinsonism (AR-JP), one of the most common familial forms of Parkinson disease, is characterized by selective dopaminergic neural cell death and the absence of the Lewy body, a cytoplasmic inclusion body consisting of aggregates of abnormally accumulated proteins. We previously cloned PARK2, mutations of which cause AR-JP (ref. 2), but the function of the gene product, parkin, remains unknown. We report here that parkin is involved in protein degradation as a ubiquitin-protein ligase collaborating with the ubiquitin-conjugating enzyme UbcH7, and that mutant parkins from AR-JP patients show loss of the ubiquitin-protein ligase activity. Our findings indicate that accumulation of proteins that have yet to be identified causes a selective neural cell death without formation of Lewy bodies. Our findings should enhance the exploration of the molecular mechanisms of neurodegeneration in Parkinson disease as well as in other neurodegenerative diseases that are characterized by involvement of abnormal protein ubiquitination, including Alzheimer disease, other tauopathies, CAG triplet repeat disorders and amyotrophic lateral sclerosis.

Cell-free translation reconstituted with purified components

We have developed a protein-synthesizing system reconstituted from recombinant tagged protein factors purified to homogeneity. The system was able to produce protein at a rate of about 160 microg/ml/h in a batch mode without the need for any supplementary apparatus. The protein products were easily purified within 1 h using affinity chromatography to remove the tagged protein factors. Moreover, omission of a release factor allowed efficient incorporation of an unnatural amino acid using suppressor transfer RNA (tRNA).

Arginine-rich peptides. An abundant source of membrane-permeable peptides having potential as carriers for intracellular protein delivery

A basic peptide derived from human immunodeficiency virus (HIV)-1 Tat protein (positions 48-60) has been reported to have the ability to translocate through the cell membranes and accumulate in the nucleus, the characteristics of which are utilized for the delivery of exogenous proteins into cells. Based on the fluorescence microscopic observations of mouse macrophage RAW264.7 cells, we found that various arginine-rich peptides have a translocation activity very similar to Tat-(48-60). These included such peptides as the d-amino acid- and arginine-substituted Tat-(48-60), the RNA-binding peptides derived from virus proteins, such as HIV-1 Rev, and flock house virus coat proteins, and the DNA binding segments of leucine zipper proteins, such as cancer-related proteins c-Fos and c-Jun, and the yeast transcription factor GCN4. These segments have no specific primary and secondary structures in common except that they have several arginine residues in the sequences. Moreover, these peptides were able to be internalized even at 4 degrees C. These results strongly suggested the possible existence of a common internalization mechanism ubiquitous to arginine-rich peptides, which is not explained by a typical endocytosis. Using (Arg)(n) (n = 4-16) peptides, we also demonstrated that there would be an optimal number of arginine residues (n approximately 8) for the efficient translocation.

A role for macrophage scavenger receptors in atherosclerosis and susceptibility to infection

Macrophage type-I and type-II class-A scavenger receptors (MSR-A) are implicated in the pathological deposition of cholesterol during atherogenesis as a result of receptor-mediated uptake of modified low-density lipoproteins (mLDL). MSR-A can bind an extraordinarily wide range of ligands, including bacterial pathogens, and also mediates cation-independent macrophage adhesion in vitro. Here we show that targeted disruption of the MSR-A gene in mice results in a reduction in the size of atherosclerotic lesions in an animal deficient in apolipoprotein E. Macrophages from MSR-A-deficient mice show a marked decrease in mLDL uptake in vitro, whereas mLDL clearance from plasma occurs at a normal rate, indicating that there may be alternative mechanisms for removing mLDL from the circulation. In addition, MSR-A-knockout mice show an increased susceptibility to infection with Listeria monocytogenes or herpes simplex virus type-1, indicating that MSR-A may play a part in host defence against pathogens.

Control selection for RNA quantitation

The study of mammalian gene expression is often carried out at the level of mRNA. In such analyses, one usually measures the amount of an mRNA of interest under different conditions such as stress, growth, development, cell and tissue localization or as part of an evaluation of the effects of gene transfection. A variety of techniques exist to measure gene expression and most commonly involve Northern hybridization analysis, ribonuclease protection or RT-PCR. Common to all of these assays is the inclusion of a so-called loading or internal control (i.e., analysis of an mRNA that does not change in relative abundance during the course of treatments). Here, we discuss the uses and pitfalls of the most popular of these controls, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and beta-actin, with special emphasis on precautions associated with the use of GAPDH.

A synthetic inhibitor of histone deacetylase, MS-27-275, with marked in vivo antitumor activity against human tumors

Synthetic benzamide derivatives were investigated for their ability to inhibit histone deacetylase (HDA). In this study, one of the most active benzamide derivatives, MS-27-275, was examined with regard to its biological properties and antitumor efficacy. MS-27-275 inhibited partially purified human HDA and caused hyperacetylation of nuclear histones in various tumor cell lines. It behaved in a manner similar to other HDA inhibitors, such as sodium butyrate and trichostatin A; MS-27-275 induced p21(WAF1/CIP1) and gelsolin and changed the cell cycle distribution, decrease of S-phase cells, and increase of G1-phase cells. The in vitro sensitivity spectrum of MS-27-275 against various human tumor cell lines showed a pattern different than that of a commonly used antitumor agent, 5-fluorouracil, and, of interest, the accumulation of p21(WAF1/CIP1) tended to be faster and greater in the cell lines sensitive to MS-27-275. MS-27-275 administered orally strongly inhibited the growth in seven of eight tumor lines implanted into nude mice, although most of these did not respond to 5-fluorouracil. A structurally analogous compound to MS-27-275 without HDA-inhibiting activity showed neither the biological effects in cell culture nor the in vivo therapeutic efficacy. These results suggest that MS-27-275 acts as an antitumor agent through HDA inhibition and may provide a novel chemotherapeutic strategy for cancers insensitive to traditional antitumor agents.

Cortical mapping of gait in humans: a near-infrared spectroscopic topography study

While we have a fair understanding of how and where forelimb-hand manipulative movements are controlled by the neocortex, due to functional imaging studies, we know little about the control of bipedal movements such as walking because of technical difficulties. We succeeded in visualizing cortical activation patterns of human gait by measuring relative changes in local hemoglobin oxygenation using a recently developed near-infrared spectroscopic (NIRS) topography technique. Walking activities were bilaterally associated with increased levels of oxygenated and total hemoglobin in the medial primary sensorimotor cortices and the supplementary motor areas. Alternating foot movements activated similar but less broad regions. Gait imagery increased activities caudally located in the supplementary motor areas. These findings provide new insight into cortical control of human locomotion. NIRS topography might be also useful for evaluating cerebral activation patterns during pathological gait and rehabilitative intervention.

A two-step mechanism for the interaction of estradiol with rat uterus

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Stent-based delivery of sirolimus reduces neointimal formation in a porcine coronary model

BACKGROUND

The purpose of this study was to determine the efficacy of stent-based delivery of sirolimus (SRL) alone or in combination with dexamethasone (DEX) to reduce in-stent neointimal hyperplasia. SRL is a potent immunosuppressive agent that inhibits SMC proliferation by blocking cell cycle progression.

METHODS AND RESULTS

Stents were coated with a nonerodable polymer containing 185 microgram SRL, 350 microgram DEX, or 185 microgram SRL and 350 microgram DEX. Polymer biocompatibility studies in the porcine and canine models showed acceptable tissue response at 60 days. Forty-seven stents (metal, n=13; SRL, n=13; DEX, n=13; SRL and DEX, n=8) were implanted in the coronary arteries of 16 pigs. The tissue level of SRL was 97+/-13 ng/artery, with a stent content of 71+/-10 microgram at 3 days. At 7 days, proliferating cell nuclear antigen and retinoblastoma protein expression were reduced 60% and 50%, respectively, by the SRL stents. After 28 days, the mean neointimal area was 2.47+/-1.04 mm(2) for the SRL alone and 2.42+/-1.04 mm(2) for the combination of SRL and DEX compared with the metal (5.06+/-1.88 mm(2), P<0.0001) or DEX-coated stents (4.31+/-3.21 mm(2), P<0.001), resulting in a 50% reduction of percent in-stent stenosis.

CONCLUSIONS

Stent-based delivery of SRL via a nonerodable polymer matrix is feasible and effectively reduces in-stent neointimal hyperplasia by inhibiting cellular proliferation.

Revised classification/nomenclature of vitiligo and related issues: the Vitiligo Global Issues Consensus Conference

During the 2011 International Pigment Cell Conference (IPCC), the Vitiligo European Taskforce (VETF) convened a consensus conference on issues of global importance for vitiligo clinical research. As suggested by an international panel of experts, the conference focused on four topics: classification and nomenclature; definition of stable disease; definition of Koebner's phenomenon (KP); and 'autoimmune vitiligo'. These topics were discussed in seven working groups representing different geographical regions. A consensus emerged that segmental vitiligo be classified separately from all other forms of vitiligo and that the term 'vitiligo' be used as an umbrella term for all non-segmental forms of vitiligo, including 'mixed vitiligo' in which segmental and non-segmental vitiligo are combined and which is considered a subgroup of vitiligo. Further, the conference recommends that disease stability be best assessed based on the stability of individual lesions rather than the overall stability of the disease as the latter is difficult to define precisely and reliably. The conference also endorsed the classification of KP for vitiligo as proposed by the VETF (history based, clinical observation based, or experimentally induced). Lastly, the conference agreed that 'autoimmune vitiligo' should not be used as a separate classification as published evidence indicates that the pathophysiology of all forms of vitiligo likely involves autoimmune or inflammatory mechanisms.

Sialic acid species as a determinant of the host range of influenza A viruses

The distribution of sialic acid (SA) species varies among animal species, but the biological role of this variation is largely unknown. Influenza viruses differ in their ability to recognize SA-galactose (Gal) linkages, depending on the animal hosts from which they are isolated. For example, human viruses preferentially recognize SA linked to Gal by the alpha2,6(SAalpha2,6Gal) linkage, while equine viruses favor SAalpha2,3Gal. However, whether a difference in relative abundance of specific SA species (N-acetylneuraminic acid [NeuAc] and N-glycolylneuraminic acid [NeuGc]) among different animals affects the replicative potential of influenza viruses is uncertain. We therefore examined the requirement for the hemagglutinin (HA) for support of viral replication in horses, using viruses whose HAs differ in receptor specificity. A virus with an HA recognizing NeuAcalpha2,6Gal but not NeuAcalpha2,3Gal or NeuGcalpha2,3Gal failed to replicate in horses, while one with an HA recognizing the NeuGcalpha2,3Gal moiety replicated in horses. Furthermore, biochemical and immunohistochemical analyses and a lectin-binding assay demonstrated the abundance of the NeuGcalpha2,3Gal moiety in epithelial cells of horse trachea, indicating that recognition of this moiety is critical for viral replication in horses. Thus, these results provide evidence of a biological effect of different SA species in different animals.

Helicobacter pylori CagA protein can be tyrosine phosphorylated in gastric epithelial cells

Attachment of Helicobacter pylori to gastric epithelial cells induces various cellular responses, including the tyrosine phosphorylation of an unknown 145-kD protein and interleukin 8 production. Here we show that this 145-kD protein is the cagA product of H. pylori, an immunodominant, cytotoxin-associated antigen. Epithelial cells infected with various H. pylori clinical isolates resulted in generation of tyrosine-phosphorylated proteins ranging from 130 to 145 kD in size that were also induced in vitro by mixing host cell lysate with bacterial lysate. When epithelial cells were infected with [(35)S]methionine-labeled H. pylori, a radioactive 145-kD protein was detected in the immunoprecipitates with antiphosphotyrosine antibody or anti-CagA (cytotoxin-associated gene A) antibody. Consistently, the 145-kD protein recognized by the anti-CagA and antiphosphotyrosine antibodies was induced in epithelial cells after infection of wild-type H. pylori but not the cagA::Km mutant. Furthermore, the amino acid sequence of the phosphorylated 145-kD protein induced by H. pylori infection was identical to the H. pylori CagA sequence. These results reveal that the tyrosine-phosphorylated 145-kD protein is H. pylori CagA protein, which may be delivered from attached bacteria into the host cytoplasm. The identification of the tyrosine-phosphorylated protein will thus provide further insights into understanding the precise roles of CagA protein in H. pylori pathogenesis.

Stearylated arginine-rich peptides: a new class of transfection systems

Membrane-permeable arginine-rich peptides, such as HIV-1 Tat-(48-60), HIV-1 Rev-(34-50), and flock house virus (FHV) coat-(35-49), have been shown to possess the ability to transfect COS-7 cells with luciferase-coding plasmid as efficiently as polyarginine (MW 5000-15 000) and polylysine (MW 9800). Not only these virus-derived cationic peptides but also oligoarginines of 4-16 residues were found to be able to transfect cells. In the case of the Tat, FHV, and octaarginine peptides, N-terminal stearylation of the peptides increases the transfection efficiency by approximately 100 times to reach the same order of magnitude as that of LipofectAMINE, one of the most efficient commercially available transfection agents. Also, a certain correlation was observed between the transfection efficiency of stearyl-(Arg)n peptides (stearyl-Rn: n = 4, 8, 12, 16) and the membrane permeability of the corresponding (Arg)n peptides (Rn).

Walking speed as a good predictor for the onset of functional dependence in a Japanese rural community population

OBJECTIVE

to investigate and compare the predictive values of four physical performance measures for the onset of functional dependence in older Japanese people living at home.

DESIGN

a population-based prospective cohort study.

SETTING

Nangai village, Akita Prefecture, Japan.

METHODS

out of the population aged 65 years and older living in Nangai (n = 940) in 1992, we measured hand grip-strength, one-leg standing, and usual and maximum walking speeds in 736 subjects who were independent in the five basic activities of daily living. Their functional status was assessed each year for the subsequent 6 years. The outcome event was the onset of functional dependence, defined as a new disability in one or more of the five basic activities of daily living, or death of a subject who had shown no disability at the previous follow-up.

RESULTS

even after controlling for age, sex and a number of chronic conditions, lower scores on each baseline performance measure showed increased risk for the onset of functional dependence. Maximum walking speed was most sensitive in predicting future dependence for those aged 65-74 years, while usual walking speed was most sensitive for people aged > or = 75 years.

CONCLUSION

walking speed was the best physical performance measure for predicting the onset of functional dependence in a Japanese rural older population.

Cardiovascular anomaly, impaired actin bundling and resistance to Src-induced transformation in mice lacking p130Cas

p130Cas (Cas), the protein encoded by the Crkas gene (also known as Cas), is an adaptor molecule with a unique structure that contains a Src homology (SH)-3 domain followed by multiple YXXP motifs and a proline-rich region. Cas was originally cloned as a highly tyrosine-phosphorylated protein in cells transformed by v-Src (refs 2,3) or v-Crk (ref. 4) and has subsequently been implicated in a variety of biological processes including cell adhesion, cell migration, growth factor stimulation, cytokine receptor engagement and bacterial infection. To determine its role in vivo, we generated mice lacking Cas. Cas-deficient embryos died in utero showing marked systemic congestion and growth retardation. Histologically, the heart was poorly developed and blood vessels were prominently dilated. Electron microscopic analysis of the heart revealed disorganization of myofibrils and disruption of Z-disks. In addition, actin stress fiber formation was severely impaired in Cas-deficient primary fibroblasts. Moreover, expression of activated Src in Cas-deficient primary fibroblasts did not induce a fully transformed phenotype, possibly owing to insufficient accumulation of actin cytoskeleton in podosomes. These findings have defined Cas function in cardiovascular development, actin filament assembly and Src-induced transformation.

Cultivated corneal epithelial stem cell transplantation in ocular surface disorders

PURPOSE

To investigate the outcome of cultivated corneal epithelial transplantation for severe stem cell deficiencies using denuded amniotic membrane (AM) as a carrier.

DESIGN

Retrospective, noncomparative case series.

PARTICIPANTS

Thirteen eyes of 11 patients were studied. These consisted of five eyes with acute Stevens-Johnson syndrome (SJS), two with chronic SJS, one with an acute chemical injury, two with chronic chemical injuries, two with ocular cicatricial pemphigoid, and one with drug-induced pseudopemphigoid. All of these eyes had total stem cell deficiencies.

MAIN OUTCOME MEASURES

Adaptation of the cultivated corneal epithelium onto the host corneal surface was confirmed 48 hours after surgery. The reconstruction of the ocular surface and visual acuity were measured.

METHODS

Corneal limbal epithelium from donor corneas was cultivated for 4 weeks on a denuded AM carrier, with 3T3 fibroblast coculture and air lifting. The cultivated corneal epithelium showed four to five layers of stratification and was well differentiated. After conjunctival tissue removal from the cornea up to 3 mm outside the limbus and subconjunctival tissue treatment with 0.04% mitomycin C, cultivated allocorneal epithelium, including the AM carrier, was transplanted onto the corneal surface up to the limbus. Lamellar keratoplasty, using preserved donor graft without epithelium, was performed simultaneously for five chronic-phase patients showing corneal stromal scarring. Systemic immunosuppression was used to prevent allograft rejection.

RESULTS

In all 13 eyes, the entire corneal surface, on which cultivated allocorneal epithelium had been placed, was free from epithelial defects 48 hours after surgery, indicating complete survival of the transplanted corneal epithelium. Visual acuity improved in all eyes after surgery, and 10 of the 13 eyes were restored to good vision (postoperative visual acuity improved two or more lines) 6 months after the operation. During the follow-up period (mean +/- standard deviation, 11.2 +/- 1.3 months), the corneal surfaces were clear, although three eyes experienced epithelial rejection.

CONCLUSIONS

Cultivated corneal epithelial transplantation using denuded AM as a carrier can be used for severe stem cell deficiencies.

The Arabidopsis AHK4 histidine kinase is a cytokinin-binding receptor that transduces cytokinin signals across the membrane

Common histidine-to-aspartate (His-->Asp) phosphorelay is a paradigm of signal transduction in both prokaryotes and eukaryotes for the propagation of certain environmental stimuli, in which histidine (His)-kinases play central roles as sensors for environmental signals. For the higher plant, Arabidopsis thaliana, it was recently suggested that the His-kinase (AHK4 / CRE1 / WOL) is a sensor for cytokinins, which are a class of plant hormones important for the regulation of cell division and differentiation. Interestingly, AHK4 is capable of functioning as a cytokinin sensor in the eubacterium, Escherichia coli (Suzuki et al. 2001, Plant Cell Physiol. 42: 107). Here we further show that AHK4 is a primary receptor that directly binds a variety of natural and synthetic cytokinins (e.g. not only N(6)-substituted aminopurines such as isopentenyl-adenine, trans-zeatin, benzyl-adenine, but also diphenylurea derivatives such as thidiazuron), in a highly specific manner (K(d) = 4.55+/-0.48x10(-9) M). AHK4 has a presumed extracellular domain, within which a single amino acid substitution (Thr-301 to Ile) was shown to result in loss of its ability to bind cytokinins. This particular mutation corresponds to the previously reported wol allele (wooden leg) that causes a striking phenotype defective in vascular morphogenesis. Collectively, evidence is presented that AHK4 and its homologues (AHK3 and possibly AHK2) are receptor kinases that can transduce cytokinin signals across the plasma membrane of A. thaliana.

Unaltered secretion of beta-amyloid precursor protein in gelatinase A (matrix metalloproteinase 2)-deficient mice

The beta-amyloid peptide, which forms extracellular cerebral deposits in Alzheimer's disease, is derived from a large membrane-spanning glycoprotein referred to as the beta-amyloid precursor protein (APP). The APP is normally cleaved within the beta-amyloid region by a putative proteinase (alpha-secretase) to generate large soluble amino-terminal derivatives of APP, and this event prevents the beta-amyloid peptide formation. It has been suggested that the gelatinase A (matrix metalloproteinase 2, a 72-kDa type IV collagenase) may act either as alpha-secretase or as beta-secretase. Mice devoid of gelatinase A generated by gene targeting develop normally, except for a subtle delay in their growth, thus providing a useful system to examine the role of gelatinase A in the cleavage and secretion of APP in vivo. We show here that APP is cleaved within the beta-amyloid region and secreted into the extracellular milieu of brain and cultured fibroblasts without gelatinase A activity. The data suggest that gelatinase A does not play an essential role in the generation and release of soluble derivatives of APP at physiological conditions.

Systematic Inflation of Buckminsterfillerene C60: Synthesis of Diphenyl Fulleroids C61 to C66

The synthesis of a new family of spheroidal carbon molecules derived from the fullerenes is described. The fulleroids are produced by incremental addition of a divalent carbon equivalent that has two phenyl (Ph) rings to fullerene C(60). The fulleroids Ph(2)C(61), Ph(4)C(62), Ph(6)C(63), Ph(8)C(64), Ph(10)C(65), and Ph(12)C(66) have been prepared and characterized.

Circulating oxidized low density lipoprotein levels. A biochemical risk marker for coronary heart disease

Recent studies have established oxidative modification of low density lipoprotein (LDL) as an important atherogenic factor. We examined the clinical relevance of circulating oxidized LDL (OxLDL) levels in atherosclerotic disease by an enzyme immunoassay with use of specific antibodies against OxLDL (FOH1a/DLH3) and apolipoprotein B. Plasma OxLDL levels were significantly higher in patients with coronary heart disease (n=65) than in control subjects (n=181; 201. 3+/-11.2 versus 112.4+/-3.3 U/dL, respectively; P<0.01). OxLDL levels were not associated with age, sex, total cholesterol, or apolipoprotein B levels in normal control subjects. Our results suggest that circulating OxLDL may be a possible biochemical risk marker for coronary heart disease.

NEDD8 recruits E2-ubiquitin to SCF E3 ligase

NEDD8/Rub1 is a ubiquitin (Ub)-like post-translational modifier that is covalently linked to cullin (Cul)-family proteins in a manner analogous to ubiquitylation. NEDD8 is known to enhance the ubiquitylating activity of the SCF complex (composed of Skp1, Cul-1, ROC1 and F-box protein), but the mechanistic role is largely unknown. Using an in vitro reconstituted system, we report here that NEDD8 modification of Cul-1 enhances recruitment of Ub-conjugating enzyme Ubc4 (E2) to the SCF complex (E3). This recruitment requires thioester linkage of Ub to Ubc4. Our findings indicate that the NEDD8-modifying system accelerates the formation of the E2-E3 complex, which stimulates protein polyubiquitylation.

LST-2, a human liver-specific organic anion transporter, determines methotrexate sensitivity in gastrointestinal cancers

BACKGROUND & AIMS

One approach to the development of targeted cancer chemotherapy exploits increased uptake of the agent into neoplastic cells. In this scenario, higher concentrations of the agent in cancer cells are responsible for differential killing, whereas the low concentration in normal human cells decreases side effects. The aim of this study was to isolate an organic anion transporter that is weak in normal cells, but abundantly expressed in cancer cells, to deliver the anticancer drugs to the cells.

METHODS

A human liver complementary DNA (cDNA) library was screened with liver-specific transporter (LST)-1 cDNA as a probe. Northern blot analyses were performed using the isolated cDNA (termed LST-2). An LST-2-specific antibody was raised, and immunohistochemical analyses including immunoelectron microscopy were performed. Xenopus oocyte expression system was used for functional analysis. We also established a permanent cell line that consistently expresses LST-2 to examine the relationship between methotrexate uptake and sensitivity.

RESULTS

The isolated cDNA, LST-2, has 79.7% of overall homology with human LST-1. LST-2 exclusively expressed in the liver under normal conditions and its immunoreactivity was highest at the basolateral membrane of the hepatocytes around the central vein. Although its weak expression in the liver, LST-2 is abundantly expressed in the gastric, colon, and pancreatic cancers. On the other hand, the LST-1 was only detected in a hepatic cell line. LST-2 transports methotrexate in a saturable and dose-dependent manner. Furthermore, introduction of the LST-2 gene into mammalian cells potentiates sensitivity to methotrexate.

CONCLUSIONS

LST-2 is one of the prime candidate molecules for determining methotrexate sensitivity and may be a good target to deliver anticancer drugs to the gastrointestinal cancers.