Biomedical subjects

S Adachi

Publications and source records attributed to S Adachi.

At least 37 records · Page 2Linked to original sources

PubMed2001

Phosphorylation of retinoid X receptor alpha at serine 260 impairs its metabolism and function in human hepatocellular carcinoma.

Retinoids induce apoptosis and differentiation of hepatocellular carcinoma (HCC) cells and are used clinically in the chemoprevention of HCC. We have shown previously that hepatocarcinogenesis is accompanied by accumulation of full-length retinoid X receptor alpha (RXRalpha), although the underlying mechanisms and biological implications have remained unclear. The present studies were based on the finding that the accumulated full-length RXRalpha was phosphorylated at serine/threonine residues both in all human HCC tissues examined and in human HCC-derived HuH7 cells. Phosphorylation at serine 260 of RXRalpha, a consensus site of mitogen-activated protein kinase, was closely linked to its retarded degradation, low transactivating activity, and the promotion of cancer cell growth. There was no genomic mutation in the RXRalpha gene, and abrogation of phosphorylation by mitogen-activated protein kinase-specific inhibitors restored the degradation of RXRalpha in an RXR ligand-dependent manner. These results suggest that phosphorylation of RXRalpha may interfere with its metabolism and signaling in human HCC, which could lead to growth promotion of these tumors.

Carcinoma, Hepatocellular↗

PubMed2001

Calcineurin pathway is required for endothelin-1-mediated protection against oxidant stress-induced apoptosis in cardiac myocytes.

Endothelin-1 (ET-1) acts not only as a growth-promoting peptide but also as a potent survival factor against myocardial cell apoptosis. However, the signaling pathways leading to myocardial cell protection by ET-1 are poorly understood. Using a culture system of primary cardiac myocytes derived from neonatal rats, we show in the present study that ET-1 almost completely blocked the hydrogen peroxide-induced increase in the percentage of TdT-mediated dUTP-biotin nick-end labeling-positive myocytes. Apoptosis inhibition by ET-1 was confirmed by cytofluorometric analysis as well as by examination of the ladder formation, morphological features, and caspase-3 cleavage. We have found that ET-1 converts the nuclear factor of activated T lymphocytes (NFATc) in cardiac myocytes into high-mobility forms and translocates cytoplasmic NFATc to the nuclei. In addition, ET-1 stimulates the interaction between NFATc and the cardiac-restricted zinc-finger protein GATA4 in these cells. The immunosuppressants cyclosporin A and FK506, which antagonize calcineurin, negated the inhibitory effect of ET-1 on apoptosis. Calcineurin activation de novo was sufficient to inhibit hydrogen peroxide-induced apoptosis. ET-1 induced the expression of an antiapoptotic protein bcl-2 in cardiac myocytes in a cyclosporin A-dependent manner, but it did not alter the expression of bax. Cyclosporin A also attenuated the ET-1-stimulated transcription of the bcl-2 gene in these cells. These findings demonstrate that the calcineurin pathway is required for the inhibitory effect of ET-1 on oxidant stress-induced apoptosis in cardiac myocytes.

Active Transport, Cell Nucleus↗

PubMed2001

Crystallization and preliminary X-ray analysis of the C/EBPbeta C-terminal region in complex with DNA.

The C-terminal fragment (residues 259-345) of human C/EBPbeta, a basic region leucine zipper transcriptional regulatory factor which includes the minimal DNA-binding domain, was crystallized in complex with a 16 bp DNA fragment from the tom-1 promoter. The crystals were in the form of a parallelepiped belonging to space group C222(1), had unit-cell parameters a = 100.7 (2), b = 113.5 (1), c = 74.4 (1) A and diffracted to a resolution of 2.1 A. Moreover, truncation of nine residues from the C-terminus not conserved among C/EBP family members yielded isomorphous crystals that diffracted to a resolution of 1.8 A or better. Truncation of 14 residues from the N-terminus of the C-terminal fragment produced well shaped crystals in the form of hexagonal bipyramids, however; unfortunately, they were unstable and diffracted poorly.

CCAAT-Enhancer-Binding Protein-beta↗

PubMed2001

Transverse josephson plasma mode in T* cuprate superconductors.

A transverse optical plasma mode is observed at far-infrared frequencies within the superconducting gap region by measuring the c-axis optical reflectivity for single crystals of T* cuprate superconductors SmLa0.85Sr0.15CuO4-delta and Nd1.4Sr0.4Ce0.2CuO4-delta. These T* cuprates have two different insulating layers sandwiching the superconducting CuO2 planes, leading to two longitudinal plasmons. Also, the transverse mode is directly observed due to the coupling of the infrared radiation with the current perpendicular to the superconducting layers which are regarded as an alternating array of two inequivalent Josephson junctions.

Journal Article↗

PubMed2001

Dandy-Walker variant in Coffin-Siris syndrome.

We describe a five-month-old male infant with Coffin-Siris syndrome, the so-called Dandy-Walker variant (hypoplasia of the cerebellar vermis with cystic dilatation of the fourth ventricle, but without enlargement of the posterior fossa), and partial agenesis of the corpus callosum. Dandy-Walker malformation and mega cisterna magna, but not Dandy-Walker variant, have been reported in Coffin-Siris syndrome. The presence of Dandy-Walker variant in the infant we described confirms that the full continuum of the Dandy-Walker complex can occur in Coffin-Siris syndrome. The yet unidentified gene(s) for the syndrome may be related to the development of the hindbrain.

Cisterna Magna↗

PubMed2001

The functional similarity and structural diversity of human and cartilaginous fish hemoglobins.

Although many descriptions of adaptive molecular evolution of vertebrate hemoglobins (Hb) can be found in physiological text books, they are based mainly on changes of the primary structure and place more emphasis on conservation than alterations at the functional site. Sequence analysis alone, however, does not reveal much about the evolution of new functions in proteins. It was found recently that there are many functionally important structural differences between human and a ray (Dasyatis akajei) Hb even where sequence is conserved between the two. We have solved the structures of the deoxy and CO forms of a second cartilaginous fish (a shark, Mustelus griseus) Hb, and compared it with structures of human Hb, two bony fish Hbs and the ray Hb in order to understand more about how vertebrate Hbs have functionally evolved by the selection of random amino acid substitutions. The sequence identity of cartilaginous fish Hb and human Hb is a little less than 40 %, with many functionally important amino acid replacements. Wider substitutions than usually considered as neutral have been accepted in the course of molecular evolution of Hb. As with the ray Hb, the shark Hb shows functionally important structural differences from human Hb that involve amino acid substitutions and shifts of preserved amino acid residues induced by substitutions in other parts of the molecule. Most importantly, beta E11Val in deoxy human Hb, which overlaps the ligand binding site and is considered to play a key role in controlling the oxygen affinity, moves away about 1 A in both the shark and ray Hbs. Thus adaptive molecular evolution is feasible as a result of both functionally significant mutations and deviations of preserved amino acid residues induced by other amino acid substitutions.

Amino Acid Sequence↗

PubMed2001

Large-scale domain movements and hydration structure changes in the active-site cleft of unligated glutamate dehydrogenase from Thermococcus profundus studied by cryogenic X-ray crystal structure analysis and small-angle X-ray scattering.

Here we describe the large-scale domain movements and hydration structure changes in the active-site cleft of unligated glutamate dehydrogenase. Glutamate dehydrogenase from Thermococcus profundus is composed of six identical subunits of M(r) 46K, each with two distinct domains of roughly equal size separated by a large active-site cleft. The enzyme in the unligated state was crystallized so that one hexamer occupied a crystallographic asymmetric unit, and the crystal structure of the hexamer was solved and refined at a resolution of 2.25 A with a crystallographic R-factor of 0.190. In that structure, the six subunits displayed significant conformational variations with respect to the orientations of the two domains. The variation was most likely explained as a hinge-bending motion caused by small changes in the main chain torsion angle of the residue composing a loop connecting the two domains. Small-angle X-ray scattering profiles both at 293 and 338 K suggested that the apparent molecular size of the hexamer was slightly larger in solution than in the crystalline state. These results led us to the conclusion that (i) the spontaneous domain motion was the property of the enzyme in solution, (ii) the domain motion was trapped in the crystallization process through different modes of crystal contacts, and (iii) the magnitude of the motion in solution was greater than that observed in the crystal structure. The present cryogenic diffraction experiment enabled us to identify 1931 hydration water molecules around the hexamer. The hydration structures around the subunits exhibited significant changes in accord with the degree of the domain movement. In particular, the hydration water molecules in the active-site cleft were rearranged markedly through migrations between specific hydration sites in coupling strongly with the domain movement. We discussed the cooperative dynamics between the domain motion and the hydration structure changes in the active site of the enzyme. The present study provides the first example of a visualized hydration structure varying transiently with the dynamic movements of enzymes and may form a new concept of the dynamics of multidomain enzymes in solution.

Binding Sites↗

PubMed2001

Cyclin A/cdk2 activation is involved in hypoxia-induced apoptosis in cardiomyocytes.

Cardiomyocytes are terminally differentiated cells characterized as withdrawal cell-cycle machinery, but nonetheless they are known to express cell-cycle regulators. Because many proteins related to the cell cycle induce apoptosis in proliferating cells, we examined the involvement of these proteins in the apoptosis pathway in cardiomyocytes. Primary rat cardiomyocytes were exposed to a severe hypoxic condition to induce apoptosis. The apoptosis rate of cardiomyocytes increased to approximately 40% under 24 hours of hypoxia as evaluated by the TUNEL method. The cyclin A protein level assessed by immunoblot analysis accumulated in a time-dependent manner in cardiomyocytes, but there was no increase in nonmyocytes. Hypoxia increased the activity of cyclin A-associated kinase but not the activity of cyclin E-associated kinase, and the apoptosis was inhibited by infection of dominant-negative cdk2 adenovirus, suggesting that cyclin A and its associated kinase play significant roles in the apoptosis of cardiomyocytes. To investigate the cyclin A-mediated apoptosis, we infected cultured cells with cyclin A adenovirus. Apoptosis was induced in 63+/-12% of the infected cardiomyocytes in contrast to only 12+/-3% of the LacZ-infected control cells. In addition, the cells in the hypoxic condition showed an increase in caspase-3 activity and a subsequent decrease in p21(cip1/waf1) protein, which is partly cleaved by caspase-3. These findings confirm that cyclin A-associated kinase mediates hypoxia-induced apoptosis in cardiomyocytes, and they also suggest that additional elements of the cell-cycle-dependent machinery participate in this mechanism.

Animals↗

PubMed2001

A modest reduction in c-myc expression has minimal effects on cell growth and apoptosis but dramatically reduces susceptibility to Ras and Raf transformation.

Dergulation of c-myc and mutation of ras genes is commonly found in many human tumors. Several lines of evidence indicate that c-Myc and oncogenic Ras cooperate in causing malignant transformation, but the mechanism of this cooperation is not understood. We set out to investigate the effect on transformation of a modest reduction in endogenous c-Myc expression, which was achieved using a c-myc heterozygous cell line constructed by targeted homologous recombination. In contrast to previous reports where c-Myc expression or activity was ablated using antisense or dominant-defective methods, use of c-myc +/- cells provides a stable and homogeneous cell culture system with a precisely defined c-Myc expression level. In addition, this approach does not suffer from nonspecific artifacts such as antisense oligonucleotide toxicity or interference of dominant-defective proteins with multiple (and often undefined) target proteins. The striking and unexpected finding communicated here is that the relatively modest 50% reduction in c-Myc expression resulted in a greater than 10-fold reduction in susceptibility to transformation by oncogenic Ras or Raf proteins. This very significant defect in transformation potential cannot be explained on the basis of a generalized cell-cycle defect, because c-myc +/- cells exhibit only a minimal (20%) reduction in proliferation. Genetic epistasis analysis indicated that c-Myc and Ras acted by independent pathways that converged to regulate the abundance of the cyclin-dependent kinase inhibitor protein p27Kip1. Anchorage deprivation elicited a strong up-regulation of p27, and a 50% reduction in c-Myc expression significantly compromised the ability of Ras to down-regulate p27. We propose that Ras and c-Myc signals cooperate to regulate the activity of cyclin D-Cdk4/6 complexes: the former by up-regulating the expression of cyclin D1 and the latter by affecting the activity of the complexes. Ectopic expression of cyclin A restored the transformation potential of c-myc +/- cells, implicating it as a downstream genetic component in the pathway. From a therapeutic standpoint, it is of interest that, although transformation appears to be very sensitive to c-Myc expression levels, much larger reductions can be tolerated without causing any significant cell cycle defects.

Animals↗

PubMed2001

Phase I/II study of intravenous nedaplatin and intraarterial cisplatin with transcatheter arterial embolization for patients with locally advanced uterine cervical carcinoma.

BACKGROUND: Nedaplatin, a platinum analog with less renal toxicity and similar efficacy for cervical carcinoma, recently has been shown to have a synergistic effect on cervical carcinoma lines in combination with cisplatin. To determine the clinical efficacy of this combination in patients with cervical carcinoma, the authors conducted a Phase I/II study of intravenous nedaplatin and intraarterial cisplatin combined with transcatheter arterial embolization (TAE). METHODS: Eligibility criteria were as follows: cervical carcinoma (Stages IB2-IV; International Federation of Gynecology and Obstetrics), 16-70 years of age, performance status between 0 and 2, and adequate bone marrow, renal, and hepatic function. Nedaplatin (40-70 mg/m2) was administered intravenously on Day 1 followed by intraarterial administration of cisplatin (70 mg/m2) on Day 3 via both uterine arteries by using the Seldinger method. This then was followed by TAE. This course of treatment was repeated every 3 weeks for 3 cycles. RESULTS: Patient data were as follows: age 37-68 (median, 55 years) and Stages IB2:4, IIA:3, IIB:2, IIIA:1, IIIB:3, IVA:2 carcinoma. The response to therapy was defined by magnetic resonance imaging as follows: partial response in 60% (9 of 15) of patients, complete response in 40% (6 of 15) of patients, and an overall response rate of 100% (95% confidence interval, 78-100%). Myelosuppression was manageable. Grade 3/4 renal toxicity was observed in 2 patients who received 70 mg/m2 of nedaplatin. Thirteen patients received radical hysterectomy, 1 patient received lymph node sampling, and 11 patients received adjuvant radiotherapy or chemotherapy. CONCLUSIONS: The maximum tolerable dose was 70 mg/m2 nedaplatin, and the dose-limiting toxicity was renal toxicity. The recommended dose was 60 mg/m2 nedaplatin intravenously followed by 70 mg/m2 cisplatin intraarterially. Intravenous nedaplatin followed by intraarterial cisplatin with TAE appears to be very effective for locally advanced cervical carcinoma.

Adult↗

PubMed2001

Multiphase ECG-triggered 3D contrast-enhanced MR angiography: utility for evaluation of hilar and mediastinal invasion of bronchogenic carcinoma.

The purpose of this study was to evaluate the usefulness of cardiac synchronized magnetic resonance angiography [electrocardiographically (ECG)-triggered MRA] for improving image quality and detection of hilar and mediastinal invasion of bronchogenic carcinoma. Fifty patients, suspected of having hilar or mediastinal invasion of bronchogenic carcinoma, underwent contrast-enhanced computed tomography and MR imaging including conventional and ECG-triggered MRA. Twenty patients subsequently also underwent surgical resection. Vascular enhancement-to-background ratio (VBR), vascular enhancement-to-tumor ratio (VTR), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and image quality scores of thoracic vessels obtained with both MRA techniques were determined and compared. In addition, the diagnostic accuracy of tumor invasion of pulmonary vessels was compared. VBRs and VTRs of both MRA techniques were not significantly different. ECG-triggered MRA significantly improved SNRs and CNRs (P < 0.05). Two readers judged that overall image quality of ECG-triggered MRA was better than that of conventional MRA (kappa > or = 0.41). In conclusion, ECG-triggered MRA improves the image quality and the detection of hilar and mediastinal invasion of bronchogenic carcinoma.

Adult↗

PubMed2001

Electroosmosis injection of blood serum into biocompatible microcapillary chip fabricated on quartz plate.

A chip which allows the detection of various human health markers from a trace amount of blood has been studied. As a goal, a microcapillary with a 30 x 30 microm cross-section was fabricated using all-dry etching technologies on a 2 x 2 cm SiO2 chip. The coating of the biocompatible 2-methacryloyloxyethylphosphorylcholine (MPC) polymer on the inner quartz wall of the microcapillary demonstrated a sufficiently long adsorption suppression of proteins in the serum on the quartz surface, while rapid stopping occurred for serum injected into the microcapillary with a bare quartz surface. The latter rapid stopping corresponded well to fast electroosmosis flow due to the negatively increasing zeta-potential by the adsorption of proteins on the quartz surface. The electroosmosis pump arranged a downstream of the microcapillary was also developed to inject serum into it. As a preliminary application, a given concentration-standard solution was injected into the ion-sensitive field-effect transistor (ISFET) embedded in the chip, employing the electroosmosis pump arranged downstream of the sensor position. Hence, the pH and Na+ and K+ cation concentrations were measured.

Blood Chemical Analysis↗

PubMed2001

20beta-Hydroxysteroid dehydrogenase of the Japanese eel ovary: its cellular localization and changes in the enzymatic activity during sexual maturation.

In many species of teleost, 20beta-hydroxysteroid dehydrogenase (20beta-HSD) is a key steroidogenic enzyme in the production of the oocyte maturation-inducing steroid (MIS), 17alpha, 20beta-dihydroxy-4-pregnen-3-one. In this study, 20beta-HSD in the ovary of the Japanese eel was biochemically characterized using a cell-free system. 20beta-HSD activity was located mainly in the membrane-bound fractions of the mitochondria and microsome, with lower levels detected in the cytosolic fraction. The enzymatic activity of membrane-bound 20beta-HSD was strikingly enhanced by treatment of eels with gonadotropin-rich salmon pituitary homogenate. The activity of eel ovarian mitochondrial 20beta-HSD in the presence of different solubilizing detergents was then assessed. Mitochondrial fractions solubilized by sodium deoxycholate and octhylthioglucoside retained approximately 30% of 20beta-HSD activity when compared to those of nontreated mitochondria. These results suggest that Japanese eel ovarian 20beta-HSD is composed of membrane-bound and soluble activities, and that the membrane-bound component is stimulated by gonadotropin.

Animals↗

PubMed2001

Overexpression of cdk Inhibitor p16INK4a by adenovirus vector inhibits cardiac hypertrophy in vitro and in vivo: a novel strategy for the gene therapy of cardiac hypertrophy.

Cardiac hypertrophy is one of the serious complications which increase mortality due to cardiovascular diseases. However, only a partial reduction of cardiac hypertrophy has been successful using current drug therapy. We demonstrate here reduction of cardiac hypertrophy in vitro and in vivo using an adenovirus vector encoding cyclin-dependent kinase (cdk) inhibitor p16INK4a. Adenovirus-mediated overexpression of cdk inhibitor p16INK4a completely inhibited cardiac myocyte hypertrophy induced by endothelin (ET)-1, as evaluated by [3H]leucine incorporation into the cells and mRNA levels of skeletal alpha -actin (SK-A) or atrial natriuretic peptide (ANP) as well as by morphometric analyses. We then evaluated whether p16INK4a can suppress left-ventricular (LV) hypertrophy induced by aortic banding (AOB) in rats. Catheter-mediated gene transfer of AxCAp16 was performed according to the method reported by Hajjar et al. LV overload was produced by coarctation of the ascending aorta immediately after inoculation of the heart with adenovirus. Two weeks after the procedure, the left ventricular weight/body weight ratio (LVW/BW) increased in the AOB+LacZ group in comparison to that in controls. However, LVW/BW was identical in the AOB+p16 group and controls. Histologic analysis revealed that p16INK4a inhibited hypertrophy of cardiac myocytes. These results suggest that G1 cell cycle regulators may restrict cardiac hypertrophy, and offer a novel strategy for the gene therapy of cardiac hypertrophy.

Actins↗

PubMed2001

Repetitious appearance and disappearance of different kinds of clonal cytogenetic abnormalities after allogeneic bone marrow transplantation.

We report a childhood case that showed the repeated appearance and disappearance of various kinds of cytogenetic abnormalities (CA) for 5.5 years after allogeneic bone marrow transplantation (BMT). The patient underwent allogeneic BMT from an HLA-matched unrelated donor during the second complete remission of acute lymphoblastic leukemia. The conditioning regimen for BMT consisted of etoposide, cyclophosphamide, anti-human thymocyte immunoglobulin, and total body irradiation. There were no leukemic relapses or secondary acute myeloid leukemia/myelodysplastic syndrome (AML/MDS) since the BMT. The CA occurred from residual recipient cells, which were damaged by chemotherapy or radiation prior to BMT. Although previous studies about post-BMT CA had reported the continuous emergence of identical clones, the present case showed the appearance of one different type of clone after another. Although the appearance of different types of CA may mean that these clones did not obtain any growth advantages, it may be a sign of genomic instability, which is probably a risk factor for the development of secondary AML/MDS.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2001

Fas receptor counterattack against tumor-infiltrating lymphocytes in vivo as a mechanism of immune escape in gastric carcinoma.

We investigated the presence and functional status of surface expression of the Fas receptor (FasR) and its ligand (FasL) in tumor and tumor-infiltrating lymphocytes (TIL) in gastric carcinoma (n = 36) from the primary locus, metastatic gastric carcinoma (n = 30) from malignant ascites, and benign gastric mucosa (n = 30) for the control. The quantitative analysis was based on the percentage of positive cells by a flow cytometry. The results showed that the membrane-bound FasL molecule was constitutively expressed in primary and metastatic gastric carcinomas as well as normal gastric epithelium in nearly all the patients. In particular, metastatic carcinoma proved to aberrantly express the FasL molecule. On the other hand, FasR expression ranged from minimal or absent in primary and metastatic gastric carcinomas, suggesting that the carcinoma might be rendered less sensitive toward FasR-induced killing. Apoptotic tumor cells detected by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick and labeling (TUNEL) were barely identified in primary and metastatic carcinomas. In the analysis of TIL, the expression of FasR and FasL, and apoptotic TIL could not usually be observed in primary gastric carcinoma. In metastatic carcinoma, however, there was significant overexpression of FasR and FasL in immune TIL associated with a higher frequency of apoptotic cell death detected by TUNEL. The results suggest that metastatic carcinoma expressing FasL, but not FasL+ primary carcinoma, might evade the immune attack by apoptotic depletion of activated TIL through the FasR/FasL systems. These results provide the direct and quantitative evidence of FasR counterattacks and/or paracrine fratricides as a mechanism of tumor-immune escape in vivo in human cancer.

Adult↗

PubMed2001

Microscopic polyangiitis complicated with massive intestinal bleeding.

Microscopic polyangiitis (MPA) is associated with renal dysfunction, in most cases, and occasionally with pulmonary hemorrhage. However, massive intestinal bleeding is a rare manifestation. We report a case of MPA in a man who developed arterial bleeding in the small intestine. A 74-year-old man was admitted after enduring a fever for 4 weeks. Laboratory examination revealed leucocytosis with neutrophil predominance, and renal dysfunction was noted. He did not respond to treatment with antibiotics, and the worsened renal function soon required hemodialysis. On the seventh hospital day, he suddenly developed massive melena. A colonoscopic examination suggested bleeding in the small intestine, and abdominal angiography demonstrated that the bleeding originated in a branch of the ileal artery. Hemostasis was achieved by transarterial embolization (TAE), but the patient suffered a massive pulmonary hemorrhage 2 days after the TAE. Although he responded well to a combination treatment with corticosteroid and cyclophosphamide, recurrence of pulmonary hemorrhage led to death, on the 87th hospital day. MPA in this patient was associated with three serious complications; deteriorating renal function, massive melena, and pulmonary hemorrhage. Of the various manifestations associated with MPA, arterial bleeding in the gastrointestinal tract, although rare, should be considered as one of the serious complications in MPA.

Aged↗

PubMed2001

Solitary schwannoma of the colon: report of two cases.

Some patients with gastrointestinal schwannoma (GIS) have been previously reported in the literature. However, GIS of the colon is quite rare. In addition, it is sometimes difficult to differentiate neurogenic tumors from other soft tissue tumors. We herein describe two cases of schwannoma of the colon, while also reviewing the relevant Japanese literature. The first case, a 73-year-old woman underwent a sigmoidectomy with lymph node dissection following the diagnosis of submucosal tumor. In the second case, a submucosal tumor was located in the cecum of a 44-year-old man. An endoscopic tumor resection was performed in the second case. The resected tumors measured 3.6 and 1.0 cm in maximal diameter, respectively. Microscopically, the tumors consisted predominantly of spindle-shaped cells that proliferated in an interlaced fashion. Mitosis was rarely seen in these tumors. Immunohistochemically, the tumor cells were strongly positive for S-100 protein, weakly positive for glial fibrillary acidic protein, and negative for CD34, alpha-smooth-muscle actin, and cytokeratin (CAM 5.2) in both cases. The tumors in the two cases were both diagnosed to be benign schwannoma of the colon. In general, schwannoma of the gastrointestinal tract is considered to be benign and should therefore be distinguished from other spindle-cell tumors or malignancies. Once diagnosed as schwannoma, extensive surgery should be avoided. Actually, such patients tend to show a good postoperative course with no evidence of recurrence.

Adult↗