Investigating the mechanism of anticancer activity of brefeldin A

Brefeldin A (BFA) is a naturally occurring macrolide with anticancer, antifungal, and antiviral effects. The mechanism(s) of action by which BFA elicits its many biological activities is not clearly understood, and this limits its development as a chemotherapeutic agent. The drug therefore is an exceptional research subject for many reasons. First, the BFA scaffold was used to develop drugs based on a pharmacophore model to afford controlled biological activity and increased drug specificity. Ester derivatives of BFA were synthesized and the compounds were tested for antiproliferative activity against the National Cancer Institute\u27s 60 cancer cell lines. Mono-derivatization at the C4 and C7 alcohols was tolerated, yielding biologically active compounds. The BFA ester conjugates synthesized in this study were cytotoxic to cancer cells, and our results prove that the disruption of the Golgi complex is not necessary for cytotoxicity. These analogues demonstrate differential biological effects and could be selecting different mechanisms of action than BFA itself. Second, the study presented an opportunity to investigate the variety of biological pathways targeted by BFA which gave further insight into the mechanism of action, particularly for eliciting the drug\u27s anticancer properties. The role of BFA as an interfacial inhibitor that interrupts the activation cycle of small GTPases was investigated. These proteins regulate several signaling pathways and are crucial for cell survival. We found that BFA treatment resulted in decreased levels of activated GTPases. This may be the means by which BFA disrupts cellular signaling and induces apoptosis. Finally, the use of BFA as an exploratory tool afforded access to present biological targets for the development of more selective chemotherapeutic agents. BFA was immobilized on a solid support and used in affinity chromatography experiments to isolate proteins which interacted with the drug. Small GTPase protein complexes and apoptosic signaling proteins were identified as BFA targets. The proteome of drug-treated cells was analyzed to determine which proteins were affected by BFA. Proteins identified in this manner included some of the proteins captured on the affinity beads, and thus confirmed their relationship with the drug