The Natural Product Borrelidin Induces UPR and Apoptosis in AML Cell Lines

Abstract 4260

Acute Myelogenous Leukemia (AML) is the most common form of leukemia. Current therapies are intense and even those fortunate enough to achieve remission often relapse extending extremely poor prognoses to these patient. The most commonly used therapeutics, namely cytarabine aribinoside, the anthracyclines and etoposide, are decades old and target ubiquitous cellular processes. We have previously reported that small molecules and natural products that activate and exacerbate the unfolded protein response (UPR) can effectively and selectively induce cell death in a wide variety of solid tumor cells. We hypothesized that the UPR might be a viable new therapeutic target in AML and sought to determine whether or not the novel UPR-inducing natural product borrelidin might be used as such an agent. A luminescent proliferation assay performed with panel of four AML cell lines treated with the ER stress-inducing antibiotic tunicamycin (Tm) revealed that three of the cell lines displayed IC50 values between 0.47–2.5μ M, doses of Tm which are known to induce a low to moderate level of ER stress. We then repeated the experiment with the more general UPR-inducing natural product borrelidin, which has been shown to have potent anti-inflammatory properties in several murine assays in vivo. All four cell lines were sensitive to borrelidin, displaying IC50 values between 0.032–0.29 μ M. Time course assays performed with borrelidin revealed 4–20 fold increases in active caspase 3 and 7 indicating borrelidin-induced AML decreases in cell proliferation might be the result of apoptosis. Quantitative reverse-transcription real time PCR performed with mRNA isolated from two AML cell lines revealed an increase in the UPR-related transcripts CHOP, ATF4, and GADD34 and the cell death genes Noxa, Puma, DR5 and Bim confirming that borrelidin could induce the UPR and apoptosis in AML cells. Studies currently underway in our laboratory will determine the ability of borrelidin and other UPR-inducing agents to reduce leukemic burden in an in vivo xenograft model.