Abstract
BackgroundTNF-related apoptosis-inducing ligand (TRAIL) receptor agonists are attractive anti-tumor agents because of their capability to induce apoptosis in cancer cells by activating death receptors (DR) 4 and 5 with little toxicity against normal cells. Despite an attractive mechanism of action, previous clinical efforts to use TRAIL receptor agonists have been unsuccessful. In this study, we examined MEDI3039, a highly potent multivalent DR5 agonist, in breast cancer cell lines and in vivo models.MethodsAs in vitro model systems, we used 19 breast cancer cell lines that are categorized into four subtypes: ER+, HER2 amplified, basal A (triple-negative breast cancer) TNBC, and basal B TNBC. Cell viability was analyzed by MTS and RealTime live/dead assays. As in vivo model systems, MDA-MB231T orthotopic primary tumor growth in the mammary fat pad (MFP) and two experimental lung metastasis models were used. The effect of MEDI3039 on MFP tumors was assessed with immunohistochemical analysis. Lung metastases were analyzed with Bouin’s and H&E staining.ResultsMEDI3039 killed multiple breast cancer cell lines, but the sensitivity varied among different subtypes. Sensitivity was basal B TNBC >> basal A TNBC > HER2 amplified > ER+ (average IC50 = 1.4, 203, 314, 403 pM, respectively). While the pattern of relative sensitivity was similar to GST-TRAIL in most cell lines, MEDI3039 was at least two orders of magnitude more potent compared with GST-TRAIL. In the MFP model, weekly treatment with 0.1 or 0.3 mg/kg MEDI3039 for 5 weeks inhibited tumor growth by 99.05% or 100% (median), respectively, compared with the control group, and extended animal survival (p = 0.08 or p = 0.0032 at 0.1 or 0.3 mg/kg, respectively). MEDI3039-induced caspase activation was confirmed in tumors grown in MFP (p < 0.05). In an experimental pulmonary metastasis model, MEDI3039 significantly suppressed outgrowth of surface (p < 0.0001) and microscopic metastases (p < 0.05). In an established lung metastasis model, MEDI3039 significantly inhibited growth of metastases (p < 0.01 in surface [> 4 mm], p < 0.01 in tumor percentage) and extended animal survival (p < 0.0001).ConclusionMEDI3039 is a potent DR5 agonist in breast cancer cells in vitro and in vivo and has potential as a cancer drug in breast cancer patients, especially those with basal B TNBC.
Highlights
tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptor agonists are attractive anti-tumor agents because of their capability to induce apoptosis in cancer cells by activating death receptors (DR) 4 and 5 with little toxicity against normal cells
MEDI3039 inhibited growth of established experimental metastases and extended animal survival In our third in vivo model system, we examined if MEDI3039 improves outcomes in an established experimental lung metastasis model (Fig. 6)
Sensitivity was highest in basal B Triple-negative breast cancer (TNBC), similar to what we had previously observed with GST-TNF-related apoptosis-inducing ligand (TRAIL) [9]; MEDI3039 was at least two orders of magnitude more potent compared with GST-TRAIL
Summary
TNF-related apoptosis-inducing ligand (TRAIL) receptor agonists are attractive anti-tumor agents because of their capability to induce apoptosis in cancer cells by activating death receptors (DR) 4 and 5 with little toxicity against normal cells. We examined MEDI3039, a highly potent multivalent DR5 agonist, in breast cancer cell lines and in vivo models. 10–15% of breast cancers are called “triple negative” (TNBC) defined by the lack of ER and PR expression and HER2 amplification [2]. Unlike the molecularly targeted treatment strategies available for hormone receptor expressing or HER2 amplified subsets of breast cancer, effective targeted therapies for TNBC that improve survival have yet to be developed, and cytotoxic chemotherapy remains the main therapy for TNBC [4]. There is a clear need to develop effective, targeted therapies for TNBC
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