Biomedical subjects

T A Chan

Publications and source records attributed to T A Chan.

4 recordsLinked to original sources

PubMed1998

Mechanisms underlying nonsteroidal antiinflammatory drug-mediated apoptosis.

Nonsteroidal antiinflammatory drugs (NSAIDs) can inhibit colorectal tumorigenesis and are among the few agents known to be useful for the chemoprevention of neoplasia. Here, we show that the tumor suppressive effects of NSAIDs are not likely to be related to a reduction in prostaglandins but rather are due to the elevation of the prostaglandin precursor arachidonic acid (AA). NSAID treatment of colon tumor cells results in a dramatic increase in AA that in turn stimulates the conversion of sphingomyelin to ceramide, a known mediator of apoptosis. These results have significant implications for understanding and improving colon cancer chemoprevention.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1996

Converting cancer genes into killer genes.

Over the past decade, it has become clear that tumorigenesis is driven by alterations in genes that control cell growth or cell death. Theoretically, the proteins encoded by these genes provide excellent targets for new therapeutic agents. Here, we describe a gene therapy approach to specifically kill tumor cells expressing such oncoproteins. In outline, the target oncoprotein binds to exogenously introduced gene products, resulting in transcriptional activation of a toxic gene. As an example, we show that this approach can be used to specifically kill cells overexpressing a mutant p53 gene in cell culture. The strategy may be generally applicable to neoplastic diseases in which the underlying patterns of genetic alterations or abnormal gene expression are known.

Cell Line↗

PubMed1994

Identification of a gene encoding a novel protein-tyrosine kinase containing SH2 domains and ankyrin-like repeats.

Using the polymerase chain reaction with primers corresponding to conserved regions in the kinase domain of protein-tyrosine kinases, we amplified segments of several protein-tyrosine kinase genes from Hydra vulgaris, a member of the ancient metazoan phylum Cnidaria. Characterization of cDNA clones for one of these genes, HTK16, revealed that it encodes a non-receptor protein-tyrosine kinase with two SH2 domains but no SH3 domain. In this regard the predicted HTK16 protein resembles two mammalian non-receptor protein-tyrosine kinases, the products of the ZAP-70 and syk genes. However, the HTK16 protein contains five ankyrin-like repeats, a structural motif which has not previously been found in protein-tyrosine kinases. The HTK16 protein also contains a potential tyrosine phosphorylation site in its carboxyl-terminal tail which resembles the phosphorylation site in members of the src family. RNA hybridization analysis indicates that the HTK16 gene is expressed in epithelial cells, cells which also express the Hydra homologue of the src protein. Our finding of the HTK16 gene in Hydra indicates that diversification of genes encoding non-receptor protein-tyrosine kinases was a very early event in metazoan evolution.

Amino Acid Sequence↗

PubMedDate not supplied

IVE (Image Visualization Environment): a software platform for all three-dimensional microscopy applications.

IVE (Image Visualization Environment) is a software platform designed from the outset to handle all aspects of modern computerized multidimensional microscopy. This platform provides users with an execution environment in which 5D data (XYZ, wavelength, and time) can be easily manipulated for the purpose of data collection, processing, display, and analysis. During the entire process, powerful data display functions are readily available for extracting complicated three-dimensional information through data visualization. By employing both the shared memory and multitasking features of the UNIX operation system, individual functions can be implemented as separate programs, and multiple programs can access the same data pool simultaneously. This enables users to combine the functionalities of different programs to facilitate each unique data analysis task. Furthermore, by defining an appropriate program execution model, commonly shared functional components such as data display, data I/O and user interface, etc. can be implemented using simple IVE library calls. This dramatically reduces the program development time and ensures consistency throughout the entire software system. As a result, users can quickly master the microscopy software system and new functions can be easily integrated, as different functional requirements arise for different research projects.

Chromosomes↗