Synthesis and Evaluation of Fluorescent Tools for Studies of Cancer Biology

Abstract

A key enabling technology in biological sciences involves fluorescent probes. These probes are typically small molecules, proteins, or nucleic acids that either possess intrinsic fluorescence or are linked to a fluorophore that emits photons and can be detected by techniques such as fluorescence spectroscopy, imaging, or flow cytometry. In early-stage drug discovery projects, fluorescent probes can be used to sort and differentiate particular types of cells, conduct high-throughput screening campaigns, and image subcellular compartments. In this dissertation, I describe the use of fluorescent probes to study microtubules and mitochondria in living cells. These structures and organelles are of substantial interest in fundamental cellular biology and as targets of anticancer agents. One of these projects is focused on the anticancer agent Paclitaxel (Taxol). This small molecule that binds microtubules and is one of the most effective treatment for patients with breast, ovarian, and lung cancers. Remarkably, although Taxol can shrink slow-growing tumors in some patients, this drug spares rapidly proliferating cells such as bone marrow cells. This inconsistency has been termed the proliferation rate paradox and is not well understood. To probe the mechanism of action of Taxol, we designed and synthesized a drug-like fluorescent probe termed PB-Gly-Taxol. This compound recapitulates many aspects of the biological properties of Taxol in cells, and provides a new tool to study proliferation rate paradox. In a second project, I describe the discovery of a small molecule termed 2,7-difluoropyronin B that accumulates in hyperpolarized mitochondria of cancer cells. When irradiated with visible blue light, this probe depolarizes mitochondrial membranes, offering a new chemical tool for photochemical control over mitochondrial biology.