Abstract 3494: MEDI3039, a novel highly potent tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptor agonist, induces apoptotic cell death in breast cancer cells
Authors: Greer Yoshimi , Gilbert Sam , Tice David , Lipkowitz Stanley 
Published: July 2016

Abstract
TRAIL receptor agonists are attractive anti-tumor agents because of their capability to induce apoptosis in cancer cells by activating death receptors 4 and 5 (DR4 and DR5) with little toxicity against normal cells. We previously reported that GST-TRAIL efficiently induced cell death in breast cancer cells, particularly mesenchymal triple negative breast cancer (TNBC) - so called basal B breast cancer cells (Rahman et al., Breast Cancer Res Treat. 2009). Recently, a newly developed multivalent TRAIL receptor agonist designed to activate DR5, has been shown to be a TRAIL super-agonist with significantly enhanced potency in multiple cancer cell lines (Swers et al., Mol Cancer Ther. 2013). We hypothesized that MEDI3039, developed by modification of this TRAIL super-agonist, is a potential new therapeutic agent to be used in human breast cancer treatment.
We used 19 human breast cancer cell lines that can be categorized into 4 groups: ER+, HER2 amplified, TNBC basal A and TNBC basal B. MEDI3039- or GST-TRAIL-induced cell death was analyzed by an MTS assay in a 96 well format after 72h of treatment. MEDI3039- or GST-TRAIL-induced caspase activation was measured by Caspase-glo 3/7 assay. Z-VAD-FMK was used as a pan-caspase inhibitor. To verify that MEDI3039 induced apoptosis via DR5, siRNA against DR4 and DR5 were transfected to cells and tested in MTS assay and Western blotting.
MEDI3039 induced cell death in MDA-MB231 (TNBC basal B), and the IC50 was 4.71pM. By contrast, GST-TRAIL induced cell death in this cell line with an IC50 of 624 pM (a 132 fold difference). MEDI3039-induced cell death was completely inhibited by Z-VAD-FMK, indicating that cell death was the result of caspase-mediated apoptotic pathway. Knockdown of DR5, but not DR4, inhibited MEDI3039-induced cell death, demonstrating that MEDI3039-mediated apoptosis requires DR5. MEDI3039 induced cell death in multiple breast cancer cell lines, but the sensitivity varied between cell lines from the four different subtypes. The TNBC basal B group was the most sensitive (avg IC50 = 1.4 pM), the TNBC basal A group was next most sensitive (avg IC50 = 203 pM), the HER2 amplified group was less sensitive (avg IC50 = 314 pM), and the ER+ group was the least sensitive to MEDI3039 (avg IC50 = 403 pM). This relative sensitivity of the different subtypes of breast cancer was similar to what was observed with GST-TRAIL. Importantly, MEDI3039 was at least 2 orders of magnitude more potent compared with GST-TRAIL in most cell lines tested. Drug combination experiments indicated that MEDI3039 has synergistic effect with multiple drugs, including cisplatin and the Wee1 inhibitor MK1775. Data from ongoing animal experiments will be presented. In conclusion, MEDI3039 is a potent TRAIL receptor agonist in breast cancer cells and has potential as a cancer drug in breast cancer patients, especially those with TNBC basal B.
Citation Format: Yoshimi Greer, Sam Gilbert, David Tice, Stanley Lipkowitz. MEDI3039, a novel highly potent tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptor agonist, induces apoptotic cell death in breast cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3494.