Biomedical subjects

Atsushi Nishikawa

Publications and source records attributed to Atsushi Nishikawa.

At least 19 recordsLinked to original sources

PubMed2007

Effect of nicking the C-terminal region of the Clostridium botulinum serotype D neurotoxin heavy chain on its toxicity and molecular properties.

A unique strain of Clostridium botulinum serotype D 4947 produces toxin complexes that are composed of un-nicked components, including a neurotoxin (BoNT) and auxiliary proteins. This BoNT showed aberrant elution upon Superdex gel filtration, indicating a much lower molecular weight, due to hydrophobic interaction with the column. Limited trypsin proteolysis of BoNT produces two nicks; first nick yielded a BoNT 50 kDa light chain disulfide linked to a 100 kDa heavy chain (Hc), and a second nick arose in Hc C-terminal 10 kDa. The second nick occurred in the putative binding domain of the BoNT molecule and induced alterations in its secondary structure, leading to a significant reduction of mouse toxicity in comparison with that of the fully-activated singly nicked BoNT. These results help to clarify the role of the C-terminal half of the Hc in the oral toxicity of single-chain and more complex forms of BoNT.

Animals↗

PubMed2006

Binding properties of Clostridium botulinum type C progenitor toxin to mucins.

It has been reported that Clostridium botulinum type C 16S progenitor toxin (C16S toxin) first binds to the sialic acid on the cell surface of mucin before invading cells [A. Nishikawa, N. Uotsu, H. Arimitsu, J.C. Lee, Y. Miura, Y. Fujinaga, H. Nakada, T. Watanabe, T. Ohyama, Y. Sakano, K. Oguma, The receptor and transporter for internalization of Clostridium botulinum type C progenitor toxin into HT-29 cells, Biochem. Biophys. Res. Commun. 319 (2004) 327-333]. In this study we investigated the binding properties of the C16S toxin to glycoproteins. Although the toxin bound to membrane blotted mucin derived from the bovine submaxillary gland (BSM), which contains a lot of sialyl oligosaccharides, it did not bind to neuraminidase-treated BSM. The binding of the toxin to BSM was inhibited by N-acetylneuraminic acid, N-glycolylneuraminic acid, and sialyl oligosaccharides strongly, but was not inhibited by neutral oligosaccharides. Both sialyl alpha2-3 lactose and sialyl alpha2-6 lactose prevented binding similarly. On the other hand, the toxin also bound well to porcine gastric mucin. In this case, neutral oligosaccharides might play an important role as ligand, since galactose and lactose inhibited binding. These results suggest that the toxin is capable of recognizing a wide variety of oligosaccharide structures.

Animals↗

PubMed2005

Cell internalization and traffic pathway of Clostridium botulinum type C neurotoxin in HT-29 cells.

The bacterium Clostridium botulinum type C produces a progenitor toxin (C16S toxin) that binds to O-linked sugar chains terminating with sialic acid on the surface of HT-29 cells prior to internalization [A. Nishikawa, N. Uotsu, H. Arimitsu, J.C. Lee, Y. Miura, Y. Fujinaga, H. Nakada, T. Watanabe, T. Ohyama, Y. Sakano, K. Oguma, Biochem. Biophys. Res. Commun. 319 (2004) 327-333] [21]. Based on this, it was hypothesized that the C16S toxin is internalized via clathrin-coated pits. To examine this possibility, the internalized toxin was observed with a fluorescent antibody using confocal laser-scanning microscopy. The confocal images clearly indicated that the C16S toxin was internalized mainly via clathrin-coated pits and localized in early endosomes. The toxin was colocalized with caveolin-1 which is one of the components of caveolae, however, implying the toxin was also internalized via caveolae. The confocal images also showed that the neurotoxin transported to the endosome was transferred to the Golgi apparatus. However, the non-toxic components were not merged with the Golgi marker protein, TGN38, implying the neurotoxin was dissociated from progenitor toxin in endosomes. These results suggested that the C16S toxin was separated to the neurotoxin and other proteins in endosome and the neurotoxin was further transferred to the Golgi apparatus which is the center for protein sorting.

Biological Transport↗

PubMed2005

Hydrophobic Man-1-P derivatives correct abnormal glycosylation in Type I congenital disorder of glycosylation fibroblasts.

Patients with Type I congenital disorders of glycosylation (CDG-I) make incomplete lipid-linked oligosaccharides (LLO). These glycans are poorly transferred to proteins resulting in unoccupied glycosylation sequons. Mutations in phosphomannomutase (PMM2) cause CDG-Ia by reducing the activity of PMM, which converts mannose (Man)-6-P to Man-1-P before formation of GDP-Man. These patients have reduced Man-1-P and GDP-Man. To replenish intracellular Man-1-P pools in CDG-Ia cells, we synthesized two hydrophobic, membrane permeable acylated versions of Man-1-P and determined their ability to normalize LLO size and N-glycosylation in CDG-Ia fibroblasts. Both compounds, compound I (diacetoxymethyl 2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl phosphate) (C-I) and compound II (diacetoxymethyl 2,3,4,6-tetra-O-ethyloxycarbonyl-alpha-D-mannopyranosyl phosphate) (C-II), contain two acetoxymethyl (CH2OAc) groups O-linked to phosphorous. C-I contains acetyl esters and C-II contains ethylcarbonate (CO2Et) esters on the Man residue. Both C-I and C-II normalized truncated LLO, but C-II was about 2-fold more efficient than C-I. C-II replenished the GDP-Man pool in CDG-Ia cells and was more efficiently incorporated into glycoproteins than exogenous Man at low concentrations (25-75 mM). In a glycosylation assay of DNaseI in CDG-Ia cells, C-II restored glycosylation to control cell levels. C-II also corrected impaired LLO biosynthesis in cells from a Dolichol (Dol)-P-Man deficient patient (CDG-Ie) and partially corrected LLO in cells from an ALG12 mannosyltransferase-deficient patient (CDG-Ig), whereas cells from an ALG3-deficient patient (CDG-Id) and from an MPDU1-deficient patient (CDG-If) were not corrected. These results validate the general concept of using pro-Man-1-P substrates as potential therapeutics for CDG-I patients.

Carbohydrate Conformation↗

PubMed2005

Cross-linking of CD45 on suppressive/regulatory T cells leads to the abrogation of their suppressive activity in vitro.

CD4(+)CD25(+) T cells have immunoregulatory and suppressive functions and are responsible for suppressing self-reactive cells and maintaining self-tolerance. In addition to CD4(+)CD25(+) T cells, there is some evidence that a fraction of CD4(+)CD25(-) T cells exhibit suppressive activity in vitro or in vivo. We have shown, using aged mice, that aging not only leads to a decline in the ability to mount CD4(+)CD25(-) T cell responses, but, at the same time, renders aged CD4(+)CD25(-) T cells suppressive. In this study we report two newly established mAbs that could abrogate the suppressive function of aged CD4(+)CD25(-) T cells. These mAbs recognized the same protein, the transmembrane phosphatase CD45. Cross-linking of CD45 on aged CD4(+)CD25(-) T cells was required for the disruption of their suppressive activity. Surprisingly, these mAbs also abrogated the suppressive action of CD4(+)CD25(+) T cells in vitro. Our results demonstrate an unexpected function of CD45 as a negative regulator neutralizing the suppressive activity of aged CD4(+)CD25(-) and young CD4(+)CD25(+) T cells.

Age Factors↗

PubMed2005

Crystallization and preliminary X-ray analysis of Thermoactinomyces vulgaris R-47 maltooligosaccharide-metabolizing enzyme homologous to glucoamylase.

A maltooligosaccharide-metabolizing enzyme from Thermoactinomyces vulgaris R-47 (TGA) homologous to glucoamylase degrades maltooligosaccharides more efficiently than starch, unlike fungal glucoamylases. TGA was crystallized and the state of the protein in solution was analyzed by gel-filtration chromatography. Diffraction data were collected to 3.31 A resolution. The TGA crystal belongs to the orthorhombic space group P2(1)2(1)2(1) or P2(1)2(1)2, with unit-cell parameters a = 110.2, b = 317.6, c = 144.9 A, and is expected to contain five to eight TGA molecules per asymmetric unit. Gel-filtration and native PAGE analyses indicated that TGA exists as a dimer in solution. This is the first report of the crystallization of an oligomeric glucoamylase.

Bacterial Proteins↗

PubMed2004

The receptor and transporter for internalization of Clostridium botulinum type C progenitor toxin into HT-29 cells.

Orally ingested botulinum toxin enters the circulatory system and eventually reaches the peripheral nerves, where it elicits a response of neurological dysfunction. In this study, we report the important findings concerning the mechanism of Clostridium botulinum type C progenitor toxin (C16S) endocytic mechanism. C16S toxin bound to high molecular weight proteins on the surface of human colon carcinoma HT-29 cells and was internalized, but not if the cells were pretreated with neuraminidase. Benzyl-GalNAc which inhibited O-glycosylation of glycoproteins also interfered in the toxin's ability to bind the cell surface. On the other hand, the toxin was internalized in spite of pretreatment of the cells with PPMP, an inhibitor of ganglioside synthesis. These results suggest that the glycoproteins, like mucin, fulfill the important roles of receptor and transporter of C16S toxin.

Botulinum Toxins↗

PubMed2004

Crystallization and preliminary X-ray analysis of Escherichia coli K12 YgjK protein, a member of glycosyl hydrolase family 63.

Processing alpha-glucosidase I, which is classified into glycosyl hydrolase (GH) family 63, hydrolyzes an oligosaccharide precursor of eukaryotic N-linked glycoproteins. Recently, many bacteria have been reported to possess genes for proteins that are homologous to the GH family 63 glucosidases. In this paper, Escherichia coli K12 YgjK protein, a member of GH family 63, was overexpressed, purified and crystallized using the vapour-diffusion method. Diffraction data were collected to 1.8 A resolution and the crystal was found to belong to the monoclinic space group P2(1), with unit-cell parameters a = 88.5, b = 137.1, c = 60.9 A, beta = 98.1 degrees. The V(M) value was determined to be 2.1 A(3) Da(-1), which corresponds to the presence of two protein molecules in the asymmetric unit.

Crystallization↗

PubMed2004

Molecular characterization of binding subcomponents of Clostridium botulinum type C progenitor toxin for intestinal epithelial cells and erythrocytes.

Clostridium botulinum type C 16S progenitor toxin consists of a neurotoxin (NTX), a non-toxic non-HA (NTNH), and a haemagglutinin (HA). The HA acts as an adhesin, allowing the 16S toxin to bind to intestinal epithelial cells and erythrocytes. In type C, these bindings are dependent on sialic acid. The HA consists of four distinct subcomponents designated HA1, HA2, HA3a and HA3b. To identify the binding subcomponent(s) of HA of type C 16S toxin, all of the HA-subcomponents and some of their precursor forms were produced as recombinant proteins fused to glutathione S-transferase (GST). These proteins were evaluated for their capacity to adhere to intestinal epithelial cells of guinea pig and human erythrocytes. GST-HA1, GST-HA3b and GST-HA3 (a precursor form of HA3a and HA3b) bound intestinal epithelial cells and erythrocytes, whereas GST alone, GST-HA2 and GST-HA3a did not. GST-HA3b and GST-HA3 showed neuraminidase-sensitive binding to the intestinal epithelial cells and erythrocytes, whereas GST-HA1 showed neuraminidase-insensitive binding. TLC binding assay revealed that GST-HA3b and GST-HA3 recognized sialosylparagloboside (SPG) and GM3 in the ganglioside fraction of the erythrocytes, like native type C 16S toxin [Inoue, K. et al. (1999). Microbiology 145, 2533-2542]. On the other hand, GST-HA1 recognized paragloboside (PG; an asialo- derivative of SPG) in addition to SPG and GM3. Deletion mutant analyses of GST-HA3b showed that the C-terminal region of HA3b is important for its binding activity. Based on these data, it is concluded that the HA component contains two distinct carbohydrate-binding subcomponents, HA1 and HA3b, which recognize carbohydrates in different specificities.

Amino Acid Sequence↗

PubMed2004

The crystal structure of Thermoactinomyces vulgaris R-47 alpha-amylase II (TVA II) complexed with transglycosylated product.

Alphan alpha-amylase (TVA II) from Thermoactinomyces vulgaris R-47 efficiently hydrolyzes alpha-1,4-glucosidic linkages of pullulan to produce panose in addition to hydrolyzing starch. TVA II also hydrolyzes alpha-1,4-glucosidic linkages of cyclodextrins and alpha-1,6-glucosidic linkages of isopanose. To clarify the basis for this wide substrate specificity of TVA II, we soaked 4(3)-alpha-panosylpanose (4(3)-P2) (a pullulan hydrolysate composed of two panosyl units) into crystals of D325N inactive mutated TVA II. We then determined the crystal structure of TVA II complexed with 4(2)-alpha-panosylpanose (4(2)-P2), which was produced by transglycosylation from 4(3)-P2, at 2.2-A resolution. The shape of the active cleft of TVA II is unique among those of alpha-amylase family enzymes due to a loop (residues 193-218) that is located at the end of the cleft around the nonreducing region and forms a 'dam'-like bank. Because this loop is short in TVA II, the active cleft is wide and shallow around the nonreducing region. It is assumed that this short loop is one of the reasons for the wide substrate specificity of TVA II. While Trp356 is involved in the binding of Glc +2 of the substrate, it appears that Tyr374 in proximity to Trp356 plays two roles: one is fixing the orientation of Trp356 in the substrate-liganded state and the other is supplying the water that is necessary for substrate hydrolysis.

Bacterial Proteins↗

PubMed2004

Insights into the reaction mechanism of glycosyl hydrolase family 49. Site-directed mutagenesis and substrate preference of isopullulanase.

Aspergillus niger isopullulanase (IPU) is the only pullulan-hydrolase in glycosyl hydrolase (GH) family 49 and does not hydrolyse dextran at all, while all other GH family 49 enzymes are dextran-hydrolysing enzymes. To investigate the common catalytic mechanism of GH family 49 enzymes, nine mutants were prepared to replace residues conserved among GH family 49 (four Trp, three Asp and two Glu). Homology modelling of IPU was also carried out based on the structure of Penicillium minioluteum dextranase, and the result showed that Asp353, Glu356, Asp372, Asp373 and Trp402, whose substitutions resulted in the reduction of activity for both pullulan and panose, were predicted to be located in the negatively numbered subsites. Three Asp-mutated enzymes, D353N, D372N and D373N, lost their activities, indicating that these residues are candidates for the catalytic residues of IPU. The W402F enzyme significantly reduced IPU activity, and the Km value was sixfold higher and the k0 value was 500-fold lower than those for the wild-type enzyme, suggesting that Trp402 is a residue participating in subsite -1. Trp31 and Glu273, whose substitutions caused a decrease in the activity for pullulan but not for panose, were predicted to be located in the interface between N-terminal and beta-helical domains. The substrate preference of the negatively numbered subsites of IPU resembles that of GH family 49 dextranases. These findings suggest that IPU and the GH family 49 dextranases have a similar catalytic mechanism in their negatively numbered subsites in spite of the difference of their substrate specificities.

Amino Acid Sequence↗

PubMed2004

Purification, characterization, and subsite affinities of Thermoactinomyces vulgaris R-47 maltooligosaccharide-metabolizing enzyme homologous to glucoamylases.

A maltooligosaccharide-metabolizing enzyme from Thermoactinomyces vulgaris R-47 (TGA) homologous to glucoamylases does not degrade starch efficiently unlike most glucoamylases such as fungal glucoamylases (Uotsu-Tomita et al., Appl. Microbiol. Biotechnol., 56, 465-473 (2001)). In this study, we purified and characterized TGA, and determined the subsite affinities of the enzyme. The optimal pH and temperature of the enzyme are 6.8 and 60 degrees C, respectively. Activity assays with 0.4% substrate showed that TGA was most active against maltotriose, but did not prefer soluble starch. Kinetic analysis using maltooligosaccharides ranging from maltose to maltoheptaose revealed that TGA has high catalytic efficiency for maltotriose and maltose. Based on the kinetics, subsite affinities were determined. The A1+A2 value of this enzyme was highly positive whereas A4-A6 values were negative and little affinity was detected at subsites 3 and 7. Thus, the subsite structure of TGA is different from that of any other GA. The results indicate that TGA is a metabolizing enzyme specific for small maltooligosaccharides.

Algorithms↗

PubMed2003

Structural insights into substrate specificity and function of glucodextranase.

A glucodextranase (iGDase) from Arthrobacter globiformis I42 hydrolyzes alpha-1,6-glucosidic linkages of dextran from the non-reducing end to produce beta-D-glucose via an inverting reaction mechanism and classified into the glycoside hydrolase family 15 (GH15). Here we cloned the iGDase gene and determined the crystal structures of iGDase of the unliganded form and the complex with acarbose at 2.42-A resolution. The structure of iGDase is composed of four domains N, A, B, and C. Domain A forms an (alpha/alpha)(6)-barrel structure and domain N consists of 17 antiparallel beta-strands, and both domains are conserved in bacterial glucoamylases (GAs) and appear to be mainly concerned with catalytic activity. The structure of iGDase complexed with acarbose revealed that the positions and orientations of the residues at subsites -1 and +1 are nearly identical between iGDase and GA; however, the residues corresponding to subsite 3, which form the entrance of the substrate binding pocket, and the position of the open space and constriction of iGDase are different from those of GAs. On the other hand, domains B and C are not found in the bacterial GAs. The primary structure of domain C is homologous with a surface layer homology domain of pullulanases, and the three-dimensional structure of domain C resembles the carbohydrate-binding domain of some glycohydrolases.

Amino Acid Sequence↗

PubMed2003

Radiotherapy for extranodal, marginal zone, B-cell lymphoma of mucosa-associated lymphoid tissue originating in the ocular adnexa: a multiinstitutional, retrospective review of 50 patients.

BACKGROUND: Due to the small number of patients and differences in the pathologic classification in most radiotherapy series, information regarding the adequacy of tumor control in patients with ocular-adnexal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) is limited. METHODS: A multiinstitutional, retrospective study was performed on 50 patients with Stage IE ocular-adnexal MALT lymphoma who were treated with radiotherapy between 1989 and 1999. The impact of patient characteristics and other variables on tumor control was analyzed. RESULTS: Responses to radiotherapy include a complete response (CR) in 26 patients, a partial response (PR) in 20 patients, and no change in 4 patients. Forty-nine of 50 patients obtained tumor control in the ocular adnexa at 24 months. Overall, 6 patients exhibited disease recurrence at 4-97 months. Three patients developed recurrence in the ocular adnexa. Two patients had isolated extranodal failure involving the oral floor and the submandibular gland, and one patient experienced failure in the neck lymph node. The initial tumor response had a marginal impact on the development of recurrence. None of the 26 patients who achieved a CR experienced ocular-adnexal recurrence. All three patients who experienced local treatment failure belonged to the initial PR group. In total, five of six patients who developed recurrent disease had obtained a PR after initial radiotherapy. Age, gender, tumor location, and dose of radiotherapy did not influence the development of recurrence. There was only one death due to lymphoma. The 5-year overall survival rate was 91% with a median follow-up of 46 months. CONCLUSIONS: Radiotherapy offers excellent local control with a prolonged clinical course for patients with MALT lymphoma in the ocular adnexa. The initial response to radiotherapy marginally influenced the probability of recurrence.

Adult↗

PubMed2003

Mechanisms mediating metabolic abnormalities in the livers of Ehrlich ascites tumor-bearing mice.

Previously we reported that intermittent intraperitoneal administration of ornithine decarboxylase-inducing factor (ODC factor), interleukin 1alpha (IL-1alpha), and tumor-necrosis factor-alpha (TNF-alpha) to normal mice induced biological changes in the hosts which included changes in the pattern of expression of pyruvate kinase (PK) isozymes in the liver and hypertrophy of the spleen. In the study reported here, we investigated the chronic and combined effects of these factors on hepatic enzymes using alzet microosmotic pumps implanted in the subcutis of the backs or abdominal cavities of mice. Continuous administration of ODC factor and recombinant human IL-1alpha (rhIL-1alpha) reduced the activity of L-type PK, which is a glycolysis-related enzyme in the liver, and induced the activity of M2-type PK, a known marker of liver dedifferentiation. Serine dehydratase (SDH) and tyrosine aminotransferase (TAT), enzymes associated with amino acid metabolism, were not significantly influenced at the examined concentration. The simultaneous continuous infusion of ODC factor and rhIL-1alpha or rhTNF-alpha caused alterations in the patterns of expression of PK isozyme activity profiles and reduced overall PK activity. SDH and TAT activities were also significantly induced. Moreover, mice treated with these combined factors displayed many other metabolic changes normally associated with cancer cachexia. These findings suggest that the tumor-derived ODC factor and cytokines such as IL-1alpha and TNF-alpha might function synergistically in the metabolic perturbations observed in Ehrlich ascites tumor bearers.

Animals↗

PubMed2003

Molecular cloning and expression of pyruvate kinase from globefish (Fugu rubripes) skeletal muscle.

A cDNA clone encoding pyruvate kinase (PK) was isolated from a skeletal muscle cDNA library of globefish (Fugu rubripes), which is a kind of lower vertebrate. The full-length cDNA of globefish skeletal muscle pyruvate kinase (FM-PK) is approximately 2 kb and encodes a protein comprising 530 amino acids. The FM-PK gene is spanning approximately 4.8 kb and consists of 11 exons. FM-PK mRNA was detected in muscle and heart using Northern blots. The recombinant FM-PK (rFM-PK) was expressed in a baculovirus-insect cell system and purified using ion-exchange chromatography. The purified rFM-PK was shown to exist a 230 kDa homotetramer composed of 57 kDa subunits. Gel filtration showed 230000 as the tetramer of the subunit. The apparent K(m) (or S(0.5)) and the Hill coefficient for phosphoenolpyruvate (PEP) and ADP are 0.14 mM, 1.3 and 0.30 mM 0.98 at pH 7.4, respectively, when the enzyme is saturated with the second substrate. The rFM-PK is strongly activated by fructose-1,6-bisphosphate, the apparent K(m) for PEP changes to 0.059 mM and the Hill coefficient to 1.1. ATP, which is the product of the enzyme reaction, inhibits activity. This is the first report to show the full-length cDNA and amino acid sequence of PK for a species of fish.

Amino Acid Sequence↗

PubMed2003

Patterns of care study: comparison of process of post-mastectomy radiotherapy (PMRT) in Japan and the USA.

BACKGROUND: The Patterns of Care Study (USPCS) by the American College of Radiology (ACR) has made significant contributions to improvements in the procedures of care for patients with breast cancer in the USA. The purpose of this study was to identify problems associated with the process of care for patients undergoing post-mastectomy radiotherapy (PMRT) in Japan compared with those in the USA. METHODS: The Japanese Patterns of Care Study Subgroup (JPCS) conducted a national survey in 1998-2000, involving 79 institutions and using two-stage cluster sampling of institutions and patients, which showed that between 1995 and 1997 PMRT was performed on 258 patients. The survey of the USPCS, involving 55 institutions, found that 407 patients received PMRT between 1998 and 1999. RESULTS: More than three axillary positive nodes were detected in 54% of the patients covered by the JPCS and in 46% of those covered by the USPCS. The clinical set-up of radiation treatment was planned without the aid of computed tomography or X-ray simulation for 25% of the JPCS patients and for 6% of the USPCS patients. The chest wall of 31% of the JPCS patients and of 98% of the USPCS patients was irradiated. The JPCS showed that inappropriate radiation techniques such as parallel opposed fields for chest wall irradiation were used for 3% of the patients in academic facilities, but for 25% of those in non-academic facilities (P = 0.0002). CONCLUSION: There is ample room for improvement in radiation treatment planning and chest wall irradiation techniques in Japan.

Breast Neoplasms↗

PubMed2003

Risk factors for local-regional recurrence following preoperative radiation therapy and surgery for head and neck cancer (stage II-IVB).

PURPOSE: To discover possible risk factors for local-regional recurrence (LRR) following preoperative radiation therapy and curative surgery for head and neck squamous cell carcinoma (SCC) (stage II-IVB). MATERIALS AND METHODS: Clinical records from 1987 to 1999 of 161 patients with head and neck SCC (oral cavity, 80 patients; larynx, 50; hypopharynx, 19; oropharynx, 12) who underwent preoperative radiation therapy and surgery were retrospectively reviewed. One hundred thirty-two (82%) of the patients had stage III or IV cancer. The median radiation dose was 38 Gy. RESULTS: The 5-year overall survival rate and LRR rate were 58% and 35%, respectively. At multivariate analysis, oral cavity cancer (P =.020), clinical T stage (P =.016), clinical N stage (P =.017), and status of surgical margins (P =.008) emerged as variables that were significantly associated with LRR. The analysis of only those patients with lymph node involvement showed that oral cavity cancer (P =.008), advanced N-stage cancer (P =.045), and long interval between the start of preoperative radiation therapy and surgery (> or =7 weeks) (P =.019) emerged as variables that were significantly associated with LRR. CONCLUSION: Oral cavity cancer, advanced T or N stage of disease, and unsatisfactory margins were risk factors for LRR. A long interval (> or =7 weeks) was a risk factor for LRR in patients with lymph node involvement.

Aged↗