Abstract A150: Complex 3D cultures for combination compound screens reveal new insights

Abstract

Abstract 3D tumor cell cultures more closely mimic the tumor environment in drug screening assays. The tumor environment includes endothelial cells, infiltrating cells, and stromal cells and the extracellular matrix excreted by these cells. It is likely that the tumor microenvironment affects the response of tumor cells to therapeutic agents. We have used a complex spheroid model consisting of tumor cells, endothelial cells (HUVEC), and mesenchymal stem cells (MSCs) to explore response to selected therapeutic agents. Using 9-10 tumor lines of each of NSCLC, melanoma, and pancreatic cancer, we tested combinations of FDA-approved agents and investigational agents on viability. All agents were studied at multiple concentrations at their reported clinical Cmax values and below in a 6 by 5 concentration matrix. Bliss independence calculations identified drug combinations that were additive, synergistic, or antagonistic. Gemcitabine plus the Chk1/2 inhibitor AZD 7762 showed strong synergy in PANC-1 cells and weaker synergy in MiaPAca-2 complex spheroids. Under the same conditions, gemcitabine and AZD7762 were additive to antagonistic in cell killing and strong antagonism was observed in CFPAC-1 cells. A combination of gemcitabine with the BET inhibitor (GSK525762) was extremely cytotoxic even at low concentrations (Gem, 0.2uM; GSK525762, 10uM)–demonstrating synergy between the Bromodomain (BET) inhibitor GSK525762 and gemcitabine in PANC-1 cells. In one NSCLC cell line (NCI-H23) the combination of GSK525762 (concentrations >1uM) was synergistic with carboplatin; however, in 5 NSCLC PDX lines, the combination had no synergy. In the LOX-IMVI melanoma line, GSK525762 was synergistic with cobimetinib. Cobimetinib and rabusertib were synergistic in the MDA-MB-435 line with >99% cell killing at concentrations < clinical Cmax. The results demonstrate that complex multicellular spheroids can be utilized in prolonged compound exposure screens (7 days) with robust and statistically relevant results using cell viability as an initial measure of cytotoxicity and can inform selection of combinations for progression. The observed additivity, synergy, or antagonism was cell line and tumor type dependent. Citation Format: David M. Evans, Selby H. Michael, Lori Bowles, Rene M. Delosh, Laudeman Julie, Chad C. Ogle, Reinhart Russell, Silvers Thomas, Ralph Parchment, James Doroshow, Beverly Teicher. Complex 3D cultures for combination compound screens reveal new insights [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A150.