Biomedical subjects

M D Lai

Publications and source records attributed to M D Lai.

42 records · Page 3Linked to original sources

PubMedDate not supplied

Exogenous mutant p53 DNA enhanced cisplatin-induced apoptosis in TSGH-8301 human bladder cancer cells.

BACKGROUND: The influence of tumor suppressor gene p53 on the apoptosis of bladder cancer cells is not completely understood. In this study, the requirement for p53 in the cisplatin-induced apoptosis of human bladder cancer cells TSGH-8301 was investigated. MATERIALS AND METHODS: TSGH-8301 cells, which contain endogenous wild type p53 genes, were transfected with expression vectors containing p53 cDNA mutated at codon 173. Stable mutant p53 transfectant clones were confirmed by Southern blotting and Western blotting. The cellular response to cisplatin was determined on the basis of (a) cells viability, (b) apoptotic DNA fragmentation, and (c) nuclear condensation. RESULTS: Cells containing an exogenous mutant p53 sequence had increased sensitivity to cisplatin by undergoing apoptosis compared with parental TSGH8301 cells. In contrast, no difference was observed in those clones with rearranged or undetectable exogenous mutant p53 cDNA. However, analysis of p53 mRNA with RT-PCR sequencing indicated that none of the transfectant clones expressed exogenous mutant p53 mRNA. CONCLUSION: The transfectants had lost the expression of mutant p53 during selection; however, they could still enhance the expression of wild-type p53, which conferred sensitivity to cisplatin. IMPLICATION: Transient expression of mutant p53 protein in TSGH8301 cells may induce an irreversibly stabilization of p53 and increase the steady state of p53 expression.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMedDate not supplied

The relationship between p53 status and anticancer drugs-induced apoptosis in nine human bladder cancer cell lines.

To study the relationship between the p53 status and chemotherapeutic drug-induced apoptosis, we have assessed the extent of apoptosis in nine bladder cancer cell lines during the treatment of adriamycin, cisplatin and methotrexate. Apoptosis was measured by the DNA fragmentation and merocyanine 540 (MC540) staining methods. Among the nine human bladder cancer cell lines, both wt-p53- and mut-p53-expressing cell lines (p53+/-) underwent apoptosis in response to anticancer drugs treatment. While the J82 (p53-/-) and TCCSUP (p53+/+) cell lines showed little or no apoptosis to these agents. Similar results were obtained when subjected to low doses of anticancer drug treatment. Interestingly, our results suggested that bladder cancer cells heterozygous for mutant p53 (+/-) seem to be most susceptible to chemotherapeutic drug. We therefore postulate that p53 mutations do not always provide a selective advantage in the development of chemoresistance, at least in bladderer tumor cell lines.

Antineoplastic Agents↗

PubMedDate not supplied

Complex of simian virus large T antigen and p53 can bind DNA specifically.

The DNA-binding activity of p53 was suggested to be abrogated by binding of large T antigen. However we demonstrate that a fraction of p53 can form a complex with large T antigen and still bind DNA specifically. In EMSA analysis, both PAb 416 and 419 anti-large-T antibodies could induce supershift on p53-DNA complex using extracts derived from two T-antigen-transformed cell lines. In EMSA-Western analysis, one of the p53-complexes was shown to contain large T antigen.

Animals↗

PubMedDate not supplied

Expression pattern of nuclear p53 is unique in COS-1 cells.

As p53 is transcriptionally inactive in COS-1 cells, we felt it would be interesting to study the relative time course of expression of nuclear p53 and the onset of S phase. Our results indicated that the expression of nuclear p53 lagged behind the onset of S phase in COS-1 cells. In addition, rapid nuclear expression of p53, probably resulting from nuclear translocation, occurred immediately after the addition of serum into COS1 cells. No such phenomena were found in B104-1 and BHK cells.

Animals↗

PubMedDate not supplied

K-ras gene mutation is a useful predictor of the survival of early stage colorectal cancers.

Mutations in the K-ras gene were found to be of predictive value in the clinical outcome of non-small cell lung cancers, but its role in predicting the survival of colorectal cancer patients is still inconclusive. Point mutations in codon 12 or 13 of K-ras gene were analyzed in 64 colorectal cancers composing 4 Dukes' stage. A, 34 stage B, 21 stage C and 5 stage D. DNA extracted from the paraffin-embedded tissues of the 64 patients was amplified with the polymerase chain reaction and subsequently analyzed by direct cycle sequencing. Thirteen of sixty-four (20%) resected colorectal cancer specimens were found to have K-ras gene mutation at either codon 12 or 13. Log rank tests found that K-ras gene mutation and Dukes' stage were associated with patients' survival. When stratified by Dukes' stage, the patients with mutated K-ras genes in the stratum of stage A or B were found to have shorter survival times than those without mutated K-ras genes (P = 0.003), but this was not the case in the stratum of stages C and D. The relative risk of mortality in the stratum of stage A or B was 7.74 (95% confidence interval: 1.72-34.89) by Cox regression analysis. We thereby conclude that K-ras gene mutation is a usefull predictor of the survival of early stage colorectal cancers.

Adult↗

PubMedDate not supplied

Tyrosine kinase expression profile in bladder cancer.

The expression pattern of tyrosine kinase in bladder cancer cells was evaluated by PCR amplification with degenerate primers derived from conserved catalytic domain in tyrosine kinase. The results indicated that TRK-E and Arg kinases were more abundantly expressed than several other kinases in bladder cancer. In addition, we identified a novel clone whose sequence could not be matched in GeneBank. This clone may represent a serine/threonine kinase based on sequence similarity.

Amino Acid Sequence↗