Biomedical subjects

Kazunori Otsuka

Publications and source records attributed to Kazunori Otsuka.

9 recordsLinked to original sources

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↗

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

[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↗

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↗

PubMed2003

Analysis of the human APC mutation spectrum in a saccharomyces cerevisiae strain with a mismatch repair defect.

Somatic APC mutations in colorectal tumors with an RER phenotype reflect excessive frameshift mutations, especially in simple repetition tracts within the coding sequence. Because this type of mutation is characteristic of cells with a deficient DNA MMR system, the APC mutation signature of RER tumors may be attributable to a defect in the MMR system. However, there is little experimental evidence to prove that the spectrum of mutations and the APC gene distribution are directly influenced by MMR system defects. We therefore examined the mutation spectrum of the MCR of the APC gene after transfection into both MMR-proficient and MMR-deficient yeast strains and compared it with a previously reported human APC mutation database. Small insertions or deletions in mono- or dinucleotide repeats were more common in the MMR-deficient than in the MMR-proficient strain (91.2% vs. 38.1%, Fisher's exact test p < 0.0001). Furthermore, the 2 mutation hot spots, 4385-4394(AG)(5) and 4661-4666(A)(6), found in the yeast system corresponded with those in human tumors. Combining our data with those from human tumors, there appears to be hypermutable mutations in specific simple repetitive sequences within the MCR, which are more prevalent in MMR-deficient cells and RER tumors than in MMR-proficient cells and non-RER tumors. We therefore consider that the differences in the spectra of RER and non-RER tumors are attributable at least in part to the MMR system of the host cells.

Adenomatous Polyposis Coli Protein↗

PubMed2003

[Reading span as an individual difference and cognitive problem solving performance].

This study investigated the performance on a computer game called Mastermind, playing of which consumes a large amount of working memory resource. First, 143 college students took a Japanese version of reading span test (RST). They then played Mastermine under two conditions: with or without display of past game records. There were 105 participants who relied under both conditions on a tactical strategy that caused high memory load, and their performance data were analyzed. Results indicated that low-span readers (87 students) were more constrained than high- and medium-span readers (18 students) under the condition without display, and performance of the low was affected by the content of display. It was argued that working memory resource that RST measured was involved in the process of cognitive problem solving.

Adult↗

PubMedDate not supplied

AFP-producing hepatoid adenocarcinoma in association with Barrett's esophagus with multiple liver metastasis responding to paclitaxel/CDDP: a case report.

A case of alpha-fetoprotein (AFP)-producing hepatoid adenocarcinoma in association with Barrett's esophagus with multiple liver metastases, responding to chemotherapy, is reported. A 47-year-old man was admitted to our hospital with abdominal pain after subtotal esophagectomy for an esophageal adenocarcinoma in association with Barrett's esophagus, and was diagnosed as having multiple liver tumors. Most tumor markers were normal, but the serum AFP level was markedly elevated. Dynamic computed tomography and ferumoxide enhanced magnetic resonance imaging did not provide evidence of any primary hepatocellular carcinoma. Since microscopic examination of the resected tumor showed a poorly-differentiated adenocarcinoma with hepatoid features displaying AFP-immunoreactivity, the liver tumors were thus considered to be metastatic deposits. Surgery was not feasible so chemotherapeutic agents were tried, and the combination of paclitaxel (TXL) and cisplatin (CDDP) gave a partial response and good control for a period. This is the first report, to our knowledge, of effective chemotherapy for liver metastases from an AFP-producing hepatoid adenocarcinoma of the esophagus.

Adenocarcinoma↗