The long-term goal is to develop calpain inhibitors as a new class of chemoprevention agents. Early precancerous cells are known to be more susceptible to apoptosis than late stage precancerous cells. The mechanism involved in this altered susceptibility to apoptosis could have important implications for carcinogenesis and the development of chemoprevention agents. Calpain is over expressed in several tumors and a number of apoptosis regulating proteins are calpain substrates suggesting an important regulatory role of calpain in cancer. Recent studies also suggest that the role of calpain in promoting cell transformation and cell migration may have important in vivo consequences in the context of cancer pathobiology. Therefore, the immediate goal of this application is to validate calpain as a pharmacological target for the discovery of novel chemoprevention agents. Our central hypothesis is """"""""inhibition of calpain activity will prevent or retard progression of precancerous lesions as well as cancer cell invasion"""""""". We will investigate this hypothesis by addressing the following specific aims: 1) synthesize alpha-ketoamides selective as metabolically stable calpain inhibitors and use them to validate calpain as a chemoprevention target; 2) determine the expression levels of calpain and apoptosis regulating proteins (p53, Bcl-2, and Bax) in early and late stage precancerous cells; and 3) determine the ability of the calpain inhibitors to prevent or retard progression of precancerous cells and to limit cancer cell invasion in vitro. The data that will be generated will be analyzed to determine if there is a link between (a) intracellular calpain inhibition and the percentage of apoptotic cells following treatment of the precancerous cells with the calpain inhibitors; (b) intracellular calpain inhibition and cytotoxicity induced in the precancerous cells by the calpain inhibitors; (c) intracellular calpain inhibition and retardation of cancer cell invasion by the calpain inhibitors. Strong correlations will associate the intrinsic potency of the calpain inhibitors with each of these parameters and confirm the activity of the compounds through a biological target, namely calpain. The proposal is significant and innovative because it seeks to investigate calpain as a pharmacological target for the discovery of a new class of chemoprevention agents. ? ? ?
| Donkor, Isaac O; Assefa, Haregewein; Liu, Jiuyu (2008) Structural basis for the potent calpain inhibitory activity of peptidyl alpha-ketoacids. J Med Chem 51:4346-50 |
