Abstract A33: Combined therapy of a novel anti-NOTCH2/3 antibody with paclitaxel inhibits tumor growth in a patient-derived breast tumor xenograft

Cancer stem cells (CSCs) have been identified as the small subpopulation of cells in many cancers and are thought to be responsible for cancer initiation, progression, metastasis, recurrence and drug resistance. The NOTCH pathway, comprised of ligands JAG1, JAG2, DLL1, DLL3 and DLL4 and receptors NOTCH1, NOTCH2, NOTCH3 and NOTCH4, plays a critical role in stem cell signaling, cell proliferation, survival, apoptosis, and differentiation. Because of the existing body of data that implicates aberrant NOTCH pathway activation in resistance to chemotherapeutic agents in epithelial and hematologic tumors, we hypothesized that NOTCH inhibition would enhance the anti-tumor activity of chemotherapeutic agents. We have identified a NOTCH3 activating mutation in a patient breast cancer and developed a xenograft tumor model from the primary patient sample, OMP-B37. The combination of paclitaxel and OncoMed9s anti-Notch2/3 antibody, OMP-59R5, inhibited the tumor growth of OMP-B37 xenograft tumors. In addition, we found that treatment with OMP-59R5 drove changes in tumor heterogeneity as indicated by the increased expression of markers associated with a mature cellular fate. The down-regulation of tumor growth promoting genes and NOTCH pathway markers was observed with OMP-59R5 treatment. The enhanced activity of combined OMP-59R5 and paclitaxel therapy in patient-derived tumor xenografts suggests that there is therapeutic potential in combining targeted NOTCH pathway inhibition with chemotherapeutic agents. Citation Format: Jie Wei, Jennifer Cain, Jalpa Shah, Breanna Wallace, Tracy Tang, Min Wang, Christopher Murriel, Cancilla Belinda, Austin Gurney, Aaron Sato, John Lewicki, Ann Kapoun, Tim Hoey. Combined therapy of a novel anti-NOTCH2/3 antibody with paclitaxel inhibits tumor growth in a patient-derived breast tumor xenograft. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Drug Sensitivity and Resistance: Improving Cancer Therapy; Jun 18-21, 2014; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(4 Suppl): Abstract nr A33.