Clarence Dunn

Interdisciplinary Training

Clarence Dunn

"Cell Migration and Communication Pathways and Their Role in Carcinogenesis"

Laminin-5 is the major adhesive ligand present in quiescent epidermal basement membrane. It has shown, using wound repair as a model, that increased expression and deposition of laminin-5 promotes cell migration and subsequent epidermal proliferation. The pathway whereby laminin-5 influences these cellular processes is not well characterized. However, it is understood that laminin-5 promotes the assembly of gap junctions and enhances gap junction intercellular communication (GJIC). Gap junctions are specialized membrane domains composed of collections of channels that directly connect neighboring cells. These channels provide for cell to cell diffusion of small molecules (<1000 Da) including ions, metabolites and second messengers. These proteins have been identified as having a putative "tumor suppressor" function. Loss of expression of these proteins is an early event in the carcinogenesis pathway, making them potentially useful markers for use in screening.

The overall goal of this interdisciplinary project is to further characterize the mechanism and biologic importance of the pathway described above. The proposal is comprised of two distinct, yet complementary research components. First, we will examine biopsy samples of normal and diseased colon that are being collected as part of an ongoing epidemiologic study. The study is designed to develop new screening strategies for colorectal cancer based on the detection of abnormalities in several different cellular pathways. Using immunohistochemistry (IHC), we will determine the localization and expression levels of several proteins: laminin-5, integrins and others proteins involved in cell adhesion, migration and communication. We hope to generate data that can be used in the future to develop new screening modalities that would improve early detection of the neoplastic process in the colon. Additionally, preliminary studies indicate that the positional data generated by IHC may provide clues regarding a potentially important part of the mechanism of colorectal carcinogenesis.

We plan to supplement the information gained from the IHC data by carrying out mechanistic studies utilizing a more easily manipulated disease model. This second component of the project entails employing a variety of molecular techniques to elucidate the intermediate steps of the lam5-->?-->GJ-->?-->GJIC pathway. We plan to approach the task of characterizing the pathway by using epidermal wound repair as a model and generating gene expression data using DNA arrays on subpopulations of epidermal cells. Analysis of this data will be followed by mutational analysis of genes thought to play a significant role in the signaling required for adhesion, gap junction assembly and GJIC.