Johns Hopkins University

Utrecht University

Patrice J Morin

Bert Vogelstein

Kenneth W Kinzler

Andrew B Sparks

Hans Clevers

Nick Barker

Vladimer Korinek

Timothy A Chan

Nonsteroidal anti-inflammatory drugs cause a dramatic increase in intracellular ceramide, which induces apoptosis. The ceramide increase is likely mediated by cyclooxygenase inhibition, which elevates arachidonic acid, which stimulates sphingomyelinase, which produces ceramide. Contacting members of this pathway with test compounds and observing their effects provides a method of screening for potential cancer chemopreventative agents.

Screening assays for cancer chemopreventative agents

The APC tumor suppressor protein binds to .beta.-catenin, a protein recently shown to interact with Tcf/Lef transcription factors. Here, the gene encoding a Tcf family member that is expressed in colonic epithelium (hTcf-4) was cloned and characterized. hTcf-4 transactivates transcription only when associated with .beta.-catenin. Nuclei of APC.sup.-/- colon carcinoma cells were found to contain a stable .beta.-catenin-hTCF-4 complex that was constitutively active, as measured by transcription of a Tcf reporter gene. Reintroduction of APC removed .beta.-catenin from hTcf4 and abrogated the transcriptional transactivation. Constitutive transcription of TCF target genes, caused by loss of APC function, may be a crucial event in the early transformation of colonic epithelium. It is also shown here that the products of mutant APC genes found in colorectal tumors are defective in regulating .beta.-catenin/Tcf-4 transcrpitional activation. Furthermore, colorectal tumors with intact APC genes were shown to contain subtle activating mutations of .beta.-catenin that altered functionally significant phosphorylation sites. These results indicate that regulation of .beta.-catenin is critical to APC's tumor suppressive effect and that this regulation can be circumvented by mutations in either APC or .beta.-catenin.

.beta.-catenin, Tcf-4, and APC interact to prevent cancer

Growing community of inventors

Columbia, MD, United States of America

Patrice J Morin