Expression of Aromatase in Escherichia coli

Abstract

Human aromatase is an enzyme necessary for estrogen biosynthesis from androgen precursors, and is often the target for chemotherapy drugs that fight against breast cancers with estrogen receptor-positive breast cancer cells. Tamoxifen, a drug that acts as an estrogen receptor antagonist, was the primary method of treatment for women with hormone receptor-positive breast cancer cells in the twentieth century and is still widely used today. More recent forms of chemotherapy drugs for breast cancer include aromatase inhibitors, which directly act on aromatase to inhibit the enzyme. Aromatase inhibitors are effective and highly selective for aromatase, but are limited by resistance issues, and therefore motivate researchers to produce drugs that will overcome those resistance mechanisms. Recent studies have shown that tamoxifen metabolites may be working to block estrogen synthesis through a second pathway; tamoxifen metabolites inhibit aromatase through noncompetitive inhibition. Although aromatase has been crystallized, there are no crystal structures that have elucidated the presence of these allosteric sites. The objective of this project is to express enough functional aromatase in E. coli cells to be able to perform ligand-binding studies on aromatase and identify allosteric sites with protein crystallography. Structural studies of aromatase and its allosteric sites will provide information on the obscure interactions of aromatase with other compounds and possibly shed light for a new generation of chemotherapy drugs.