Abstract POSTER-THER-1422: Development of proteomic biomarkers for the apoptosis pathway in ovarian cancer cell lines and determination of the appropriate sequence of the SMAC-mimetic birinapant (TL32711) and docetaxel for optimal therapeutic effect
Authors: Noonan Anne M. , Hernandez Lidia , Herrmann Michelle , Chen Jinqui , Annunziata Christina M. 
Published: August 2015

Background: The SMAC-mimetic birinapant (TL32711) induces apoptosis of ovarian cancer (OC) cell lines by eliminating the inhibitors of apoptosis (IAPs) and attenuating NFkB signaling. The increase in mitochondrial membrane permeability (MOMP) induced by docetaxel releases cytochrome c, unleashing the caspase cascade, which culminates in apoptosis. In addition, caspase-8 cleavage results in activation of the BH3-only protein BH3-interacting domain death agonist (BID), the product of which (truncated BID; tBID) is required for death receptor-induced apoptosis via BID activation and MOMP. Thus, caspase-8 is at the intersection between the extrinsic and intrinsic apoptosis pathways. We hypothesized that the combination of birinapant and docetaxel would be synergistic augmenting the apoptotic response in OC. Our aim was to determine the most appropriate sequence for optimal therapeutic effect in a cell line model and develop potential proteomic biomarkers.

Methods: Toxicity of the SMAC-mimetic birinapant and docetaxel was assessed in a panel of OC cell lines using XTT assay with specific attention to the order and timing of drug administration. The target protein changes were assessed using Western blot and Simple Western. Similar protein changes are being assessed in mouse model. Cytokine analysis was performed on the secretome of cells treated with drug.

Results: There was variable sensitivity to single-agent exposure to the small molecule SMAC mimetic in OC cell lines. Increased cell death was seen upon administration of both docetaxel and birinapant, with enhanced toxicity when birinapant was administered prior to docetaxel. Degradation of cIAP1, the main pharmacodynamic outcome of brianapant, was seen after one hour of birinapant exposure, and was maintained up to 12 hours. Interestingly, cIAP2 levels increased from 3 hours to 24 hours. Cleavage of caspase-3 began at 3 hours and was maximal at 24 hours. PARP cleavage occurred 24 hours after treatment. Docetaxel induced cleavage of BID. Enhanced caspase-3 and caspase-8 cleavage were seen when both birinapant and doctaxel were administered. Similar protein changes are being examined in ongoing mouse experiment and will be reported at the meeting.

Conclusions: The combination of birinapant and docetaxel results in enhanced cell death in an OC cell line model with evidence of target protein engagement.

Citation Format: Anne M. Noonan, Lidia Hernandez, Michelle Herrmann, Jinqui Chen, Christina M. Annunziata. Development of proteomic biomarkers for the apoptosis pathway in ovarian cancer cell lines and determination of the appropriate sequence of the SMAC-mimetic birinapant (TL32711) and docetaxel for optimal therapeutic effect [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-THER-1422.