Abstract P5-03-06: 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 YE , Tice D , Lipkowitz S 
Published: May 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., Adv. Cancer Res. 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 from this TRAIL super-agonist, is a potential new therapeutic agent to be used in human breast cancer treatment.
As model systems, we used 19 breast cancer cell lines that can be categorized into 4 different 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 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 the receptor for MEDI3039, 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 and GST-TRAIL 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. TNBC basal B group was the most sensitive (avg IC50= 1.4 pM), TNBC basal A group was next most sensitive (avg IC50 = 203 pM, HER2 amplified group was less sensitive (avg IC50 = 314 pM), and ER+ group was the least sensitive to MEDI3039 (avg IC50= 403 pM). This 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, MK1775. Animal breast cancer xenograft experiments are planned to test the efficacy of MEDI3039 in vivo. Further work to identify biomarker(s) that correlate with MEDI3039 sensitivity, and effective combinations that enhance the toxicity of MEDI3039 especially in the resistant breast cancer subtypes are ongoing. 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: Greer YE, Tice D, Lipkowitz S. 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 Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-03-06.