Biomedical subjects

Shunsuke Kato

Publications and source records attributed to Shunsuke Kato.

16 recordsLinked to original sources

PubMed2006

Dose escalation study of docetaxel and nedaplatin in patients with relapsed or refractory squamous cell carcinoma of the esophagus pretreated using cisplatin, 5-fluorouracil, and radiation.

BACKGROUND: Definitive chemoradiation with cisplatin (CDDP) and 5-fluorouracil (5FU) has been playing an important role in the treatment of esophageal cancer, but some patients are not curable or have recurrent lesions. However, few chemotherapeutic regimens are available for such patients. Docetaxel and nedaplatin are active for esophageal cancer. We conducted a dose-escalation study of docetaxel and nedaplatin as second line-chemotherapy after definitive chemoradiation in patients with relapsed or refractory squamous cell carcinoma of the esophagus after chemoradiation. METHODS: Nedaplatin was administered on day 1 and docetaxel was administered on days 1 and 15, every 4 weeks. Dose escalation was based on the dose-limiting toxicity (DLT) observed during the first cycle. RESULTS: Twelve patients were enrolled. At a docetaxel dose of 30 mg/m(2) and a nedaplatin dose of 80 mg/m(2), one grade 4 neutropenia occurred and caused one treatment break longer than 2 weeks, but there were few DLTs. At doses of 35 and 80 mg/m(2), respectively, two grade 4 neutropenias and one grade 2 thrombopenia occurred and caused three treatment breaks longer than 2 weeks. Therefore, the maximum tolerated dose was established at this dose level. Two grade 3 anorexias and one grade 3 nausea occurred, but other non-hematological toxicities were generally mild. Responses were seen in one-fourth of the 12 patients, including one complete remission. CONCLUSION: The recommended doses of docetaxel and nedaplatin were 30 and 80 mg/m(2), respectively. This combination could be a potential second-line treatment for this target population.

Aged↗

PubMed2006

Computational approaches for predicting the biological effect of p53 missense mutations: a comparison of three sequence analysis based methods.

Prediction of the biological effect of missense substitutions has become important because they are often observed in known or candidate disease susceptibility genes. In this paper, we carried out a 3-step analysis of 1514 missense substitutions in the DNA-binding domain (DBD) of TP53, the most frequently mutated gene in human cancers. First, we calculated two types of conservation scores based on a TP53 multiple sequence alignment (MSA) for each substitution: (i) Grantham Variation (GV), which measures the degree of biochemical variation among amino acids found at a given position in the MSA; (ii) Grantham Deviation (GD), which reflects the 'biochemical distance' of the mutant amino acid from the observed amino acid at a particular position (given by GV). Second, we used a method that combines GV and GD scores, Align-GVGD, to predict the transactivation activity of each missense substitution. We compared our predictions against experimentally measured transactivation activity (yeast assays) to evaluate their accuracy. Finally, the prediction results were compared with those obtained by the program Sorting Intolerant from Tolerant (SIFT) and Dayhoff's classification. Our predictions yielded high prediction accuracy for mutants showing a loss of transactivation ( approximately 88% specificity) with lower prediction accuracy for mutants with transactivation similar to that of the wild-type (67.9 to 71.2% sensitivity). Align-GVGD results were comparable to SIFT (88.3 to 90.6% and 67.4 to 70.3% specificity and sensitivity, respectively) and outperformed Dayhoff's classification (80 and 40.9% specificity and sensitivity, respectively). These results further demonstrate the utility of the Align-GVGD method, which was previously applied to BRCA1. Align-GVGD is available online at http://agvgd.iarc.fr.

Amino Acid Sequence↗

PubMed2006

The clinical value of somatic TP53 gene mutations in 1,794 patients with breast cancer.

To investigate the clinical value of somatic TP53 mutations in breast cancer, we assembled clinical and molecular data on 1,794 women with primary breast cancer with long-term follow-up and whose tumor has been screened for mutation in exons 5 to 8 of TP53 by gene sequencing. TP53 mutations were more frequent in tumors of ductal and medullar types, aggressive phenotype (high grade, large size, node positive cases, and low hormone receptor content) and in women <60 years old. TP53 mutations within exons 5 to 8 conferred an elevated risk of breast cancer-specific death of 2.27 (relative risk >10 years; P < 0.0001) compared with patients with no such mutation. The prognostic value of TP53 mutation was independent of tumor size, node status, and hormone receptor content, confirming and reconciling previous findings in smaller series. Moreover, an interaction between TP53 mutation and progesterone receptor (PR) status was revealed, TP53 mutation combined with the absence of progesterone receptor being associated with the worst prognosis. Whereas previous studies have emphasized the fact that missense mutations in the DNA-binding motifs have a worse prognosis than missense mutations outside these motifs, we show that non-missense mutations have prognostic value similar to missense mutations in DNA-binding motifs. Nonetheless, specific missense mutants (codon 179 and R248W) seem to be associated with an even worse prognosis. These results, obtained on the largest series analyzed thus far, show that TP53 mutations identified by gene sequencing have an independent prognostic value in breast cancer and could have potential uses in clinical practice.

Aged↗

PubMed2006

Meta-analysis of the p53 mutation database for mutant p53 biological activity reveals a methodologic bias in mutation detection.

PURPOSE: Analyses of the pattern of p53 mutations have been essential for epidemiologic studies linking carcinogen exposure and cancer. We were concerned by the inclusion of dubious reports in the p53 databases that could lead to controversial analysis prejudicial to the scientific community. EXPERIMENTAL DESIGN: We used the universal mutation database p53 database (21,717 mutations) combined with a new p53 mutant activity database (2,300 mutants) to perform functional analysis of 1,992 publications reporting p53 alterations. This analysis was done using a statistical approach similar to that of clinical meta-analyses. RESULTS: This analysis reveals that some reports of infrequent mutations are associated with almost normal activities of p53 proteins. These particular mutations are frequently found in studies reporting multiple mutations in one tumor, silent mutations, or lacking mutation hotspots. These reports are often associated with particular methodologies, such as nested PCR, for which key controls are not satisfactory. CONCLUSIONS: We show the importance of accurate functional analysis before inferring any genetic variation. The quality of the p53 databases is essential in order to prevent erroneous analysis and/or conclusions. The availability of functional data from our new p53 web site (http://p53.free.fr and http://www.umd.be:2072/) will allow functional prescreening to identify potential artifactual data.

Databases, Factual↗

PubMed2006

The UMD TP53 database and website: update and revisions.

Mutation of the p53 gene is the most frequent genetic alteration found in human cancer, but it is also the most frequently reported with more than 22,000 mutations published in 2,000 papers. In 1991, we developed a database and software to handle and analyze all this information. The database has been widely used for clinical analysis and molecular epidemiology. We have expanded the scope of the database by integrating structural, phylogenetic and biological information on wild-type (wt) and mutant TP53. Integration of the TP53 mutant activity database provides unique information that will be useful to both clinicians and scientists. All of this information is available from a new website (www.umd.be:2072/) that will generate a detailed informative page for every TP53 mutant in the database. New tools to check TP53 mutations and minimize errors found in the literature are also available.

DNA Mutational Analysis↗

PubMed2006

Predicting the transactivation activity of p53 missense mutants using a four-body potential score derived from Delaunay tessellations.

We describe a novel statistical scoring method based on a computational geometry approach to predict the functional impact (transactivation activity) of missense mutations in the DNA-binding domain (DBD) of the tumor suppressor TP53, which is the most frequently mutated gene in human cancer. Residual scores (RS) for each residue were calculated to reflect differences in the compositional preferences of four nearest-neighbor residues between mutant and wild-type proteins. The RS were then combined into a residual score profile (RSP) representing the RS values for all 194 residues in the DBD. Mutants were grouped into functional categories based on their transactivation activities experimentally measured in yeast functional assays using p53-response elements from eight different promoters. While these functional categories showed significant differences in average RS, the latter lacked resolution power to predict the transactivation activities of individual mutants. In contrast, using decision tree models, we found that the RSP predicted transactivation with an accuracy varying between 64.2% and 78.5% depending on the promoter. Lastly, we used the best model to predict the functional outcome of all missense mutants in the DBD of p53 and compared the predictions with their frequency of occurrence in human cancers. We found that mutants predicted as functional (F) accounted for approximately 14% of all missense mutants found in cancers, while mutants predicted as nonfunctional (NF) represented approximately 86% of the mutants. These results show that this computational approach provides a fast and reliable method for predicting the functional impact of p53 mutants associated with cancer.

Algorithms↗

PubMed2006

Diffuse bone marrow uptake on F-18 FDG PET in patients with myelodysplastic syndromes.

It is well known that hematopoietic cytokine stimulation can cause diffuse increase of FDG accumulation in bone marrow on PET imaging, which simulates that seen in patients with bone marrow metastases. However, diffuse bone marrow FDG uptake can be caused by other etiologies. We report 2 patients who did not have a history of hematopoietic cytokine stimulation. The FDG PET images showed diffuse bone marrow FDG uptake, and the patients were diagnosed as having myelodysplastic syndromes. These cases demonstrate that diffuse FDG uptake by bone marrow can suggest neoplastic disease of the hematopoietic tissues.

Aged↗

PubMed2006

[A case of malignant melanoma from the esophagus responding to weekly paclitaxel therapy].

A 44-year-old man had a tumor in the lower thoracic esophagus at a health check, and was initially diagnosed as an undifferentiated carcinoma of the esophagus by the esophago-gastric endoscope. Although curative chemoradiotherapy was scheduled after the diagnosis, the interim evaluation revealed that the tumor was malignant melanoma of the esophagus with right renal metastasis. Since then, CVD (cisplatin, vindesine and dacarbazine) therapy, palliative radiotherapy and DAC-Tam (dacarbazine, nimustine, cisplatin and tamoxifen) therapy were carried out, but all of them proved ineffective, and multiple newly metastatic lesions appeared in liver and lymph nodes. Oral intake was impossible because of progressing stricture of the esophagus. As a fourth-line therapy, weekly paclitaxel therapy was started, and his oral intake was improved after the second course. He received the therapy as an outpatient for four months. After the third course, tumor lesions were evaluated as a partial response by CT. Consequently, five courses of the therapy were performed with modest adverse effects. Weekly paclitaxel therapy was reasonably safe as reported in other reports and considered to be a promising regimen for malignant melanoma of the esophagus.

Adult↗

PubMed2006

[Two cases of multiple liver metastases from colorectal cancer which responded well to hepatic arterial infusion (HAI) using 5-fluorouracil and l-leucovorin].

We present two cases of multiple liver metastases from colorectal cancer, which did not respond to hepatic arterial infusion (HAI) using 5-fluorouracil (5-FU 1250 mg/body weekly) alone, but responded to HAI using 5-fluorouracil (5-FU 750 mg/body weekly) and l-leucovorin (l-LV 50 mg/body weekly) achieving a complete response (CR). The first case: A 71-year-old man with Stage II rectal cancer who underwent lower anterior resection developed multiple liver metastases 5 months after the surgery. As the weekly HAl using 5-FU for nine courses showed no response, l-LV was combined, and the liver metastases disappeared after 10 courses to achieve CR. The second case: A 65-year-old man with rectal cancer, sigmoid colon cancer and multiple liver metastases underwent lower anterior resection. The weekly HAl using 5-FU for seven courses showed no response. By combining 5-FU to l-LV, the liver metastases disappeared after fifteen courses. No toxic event was observed. In these two cases, it was suspected that a reduced foliate may be responsible for the failure by the 5-FU treatment alone.

Aged↗

PubMed2005

The relationship among p53 oligomer formation, structure and transcriptional activity using a comprehensive missense mutation library.

Tumor suppressor p53 forms a homo-tetramer through its COOH-terminal oligomerization domain and acts as a sequence-specific transcription factor. We have analysed the interrelation among the transcriptional activities, the structure and the cancer-related mutations in the oligomerization domain by using a comprehensive missense mutation library. Here, we examined the ability of 184 mutant p53s in the domain to form an oligomer by expressing these mutant p53s in yeast, and compared the data with the previous information. We showed that specific residues in the alpha-helix and the beta-strand of the oligomerization domain were critical for both oligomer formation and sequence-specific transactivation, and the activities were closely related. In particular, the alpha-helix was more sensitive to amino-acid substitutions than the beta-strand. We found identity in the interrelation between the two activities, that is, monomer mutants were transcriptionally inactive whereas dimer and tetramer mutants retained their transcriptional activities. In TP53 mutation databases, a small number of mutations have been reported in this domain. Surprisingly, most do not encode p53s defective in functional properties. These results indicate that, although oligomer formation is essential for p53 transactivation function, the inactivation of oligomer formation and therefore the inactivation of transactivation may not be essential for tumor suppression by p53 because they do not lead to oncogenic proteins.

Biopolymers↗

PubMed2005

Lack of correlation between p53-dependent transcriptional activity and the ability to induce apoptosis among 179 mutant p53s.

Tumor suppressor p53-dependent apoptosis is thought to be one of the most important tumor-suppressive functions in human tumorigenesis. However, whether the major mechanism underlying the p53-dependent apoptosis is transactivation dependent or independent remains unclear. Using 179 mutant p53s with diverse transcriptional activities for distinct p53-binding sequences in yeast, we evaluated both their sequence-specific transcriptional activities on six p53 target genes and their ability to induce apoptosis in Saos-2 cells. These mutant p53s also represented diversity in their ability to both transactivate target genes and induce apoptosis. We identified 17 mutant p53s with superior ability to induce apoptosis than wild-type p53 that tend to cluster at residues 121 or 290 to 292. There was no significant correlation between the two functional properties on any single target gene examined. Furthermore, the 17 mutant p53s were not classified in a specific cluster by hierarchical cluster analysis on their diverse transcriptional activities, indicating that these mutant p53s were not similar in the transcriptional activity of downstream genes. These results suggested that transactivation-dependent apoptosis does not always play a major role in p53-dependent apoptosis, indirectly supporting the importance role of the transactivation-independent mechanism.

Apoptosis↗

PubMed2005

Reassessment of the TP53 mutation database in human disease by data mining with a library of TP53 missense mutations.

TP53 alteration is the most frequent genetic alteration found in human cancers. To date, more than 15,000 tumors with TP53 mutations have been published, leading to the description of more than 1,500 different TP53 mutants (http://p53.curie.fr). The frequency of these mutants is highly heterogeneous, with 11 hotspot mutants found more than 100 times, whereas 306 mutants have been reported only once. So far, little is known concerning the biological significance of these rare mutants, as the majority of biological studies have focused on classic hotspot mutants. In order to gain a deeper knowledge about the significance of all of these mutants, we have cross-checked each mutant of the TP53 mutation database for its activity, derived from a library of 2,314 TP53 mutants representing all possible amino acid substitutions caused by a point mutation. The transactivation activity of all of these mutant was analyzed with respect to eight transcription promoters [Kato S, et al., Proc Natl Acad Sci USA (2003)100:8424-8429]. Although the most frequent TP53 mutants sustain a clear loss of transactivation activity, more than 50% of the rare TP53 mutants display significant activity. Analysis in specific types of cancer or in normal skin patches demonstrates a similar distribution of TP53 loss of activity, with the exception of melanoma, in which the majority of TP53 mutants display significant activity. Our data indicate that TP53 mutants represent a highly heterogeneous population with a large diversity in terms of loss of transactivation activity that could account for the heterogeneous tumor phenotypes and the difficulty of clinical studies.

Arthritis, Rheumatoid↗

PubMed2005

[Retrospective analysis on efficacy and toxicity of 5-fluorouracil (5-FU) and l-leucovorin (l-LV) in advanced or recurrent colorectal cancer].

The aim of this study was to evaluate the efficacy and toxicity of 5-fluorouracil (5-FU) and l-leucovorin (I-LV) in 50 patients with advanced or recurrent colorectal cancer in our institute. The dose of 5-FU was 600 mg/m2 and the dose of l-LV was 250 mg/m2. Objective response were 36.8% of patients who had administration of full-dose and 14.8% of patients who had the administration of reduced dose or prolonged interval. No significant difference was observed in clinical benefit rates between patients administrated in full-dose and patients in reduced dose or prolonged interval. Median survival time (MST) of patients in reduced dose or prolonged interval is longer than patients in full-dose. These data suggest that 5-FU/l-LV can be given in the outpatient and yields improved prognosis and minimal adverse reactions even in patients in reduced dose or prolonged interval.

Adult↗

PubMed2004

A novel germline mutation of the LKB1 gene in a patient with Peutz-Jeghers syndrome with early-onset gastric cancer.

The gene responsible for Peutz-Jeghers syndrome (PJS), LKB1 (also called STK11) was mapped to chromosome 19p13.3 and was found to encode a putative serine/threonine protein kinase, LKB1. As only a limited number (approximately 100) of germline mutations of the gene have been reported, and because the protein function is still unclear, information about LKB1 mutations and their expression should be accumulated to understand the phenotype-genotype correlation of this disease. Here we report a patient with sporadic PJS with early-onset gastric cancer. We found a novel germline frameshift mutation (757-758insT) in the LKB1 gene and a marked reduction in LKB1 protein expression in the carcinoma cells, suggesting that the loss of LKB1 function may have led to the carcinogenesis of the gastric cancer.

AMP-Activated Protein Kinase Kinases↗

PubMed2003

Isolation of temperature-sensitive p53 mutations from a comprehensive missense mutation library.

Temperature-sensitive (ts) mutations have been used as a genetic and molecular tool to study the functions of many gene products. Each ts mutant protein may contain a temperature-dependent intramolecular mechanism such as ts conformational change. To identify key ts structural elements controlling the protein function, we screened ts p53 mutants from a comprehensive mutation library consisting of 2,314 p53 missense mutations for their sequence-specific transactivity through p53-binding sequences in Saccharomyces cerevisiae. We isolated 142 ts p53 mutants, including 131 unreported ts mutants. These mutants clustered in beta-strands in the DNA-binding domain, particularly in one of the two beta-sheets of the protein, and 15 residues (Thr155, Arg158, Met160, Ala161, Val172, His214, Ser215, Pro223, Thr231, Thr253, Ile254, Thr256, Ser269, Glu271, and Glu285) were ts hot spots. Among the 142 mutants, 54 were examined further in human osteosarcoma Saos-2 cells, and it was confirmed that 89% of the mutants were also ts in mammalian cells. The ts mutants represented distinct ts transactivities for the p53 binding sequences and a distinct epitope expression pattern for conformation-specific anti-p53 antibodies. These results indicated that the intramolecular beta-sheet in the core DNA-binding domain of p53 was a key structural element controlling the protein function and provided a clue for finding a molecular mechanism that enables the rescue of the mutant p53 function.

Amino Acid Sequence↗

PubMed2003

Understanding the function-structure and function-mutation relationships of p53 tumor suppressor protein by high-resolution missense mutation analysis.

Inactivation of the tumor suppressor p53 by missense mutations is the most frequent genetic alteration in human cancers. The common missense mutations in the TP53 gene disrupt the ability of p53 to bind to DNA and consequently to transactivate downstream genes. However, it is still not fully understood how a large number of the remaining mutations affect p53 structure and function. Here, we used a comprehensive site-directed mutagenesis technique and a yeast-based functional assay to construct, express, and evaluate 2,314 p53 mutants representing all possible amino acid substitutions caused by a point mutation throughout the protein (5.9 substitutions per residue), and correlated p53 function with structure- and tumor-derived mutations. This high-resolution mutation analysis allows evaluation of previous predictions and hypotheses through interrelation of function, structure and mutation.

Amino Acid Substitution↗