Abstract

Breast cancer (BC) originates in either milk-producing luminal cells or the contractile basal cells of the mammary gland. Due to this difference in the cell of origin, BC has intrinsic subtypes (luminal A, luminal B, Basal Claudin low and HER2 subtypes). Treatment for each subtype differs depending upon the differential expression of the drug targets (estrogen, progesterone and HER2 receptors). New treatment strategies are required because of the subtype-specific drug response, metastasis, and therapeutic resistance. Translation of new treatment strategies from bench side to bedside requires pre-clinical testing performed on a relevant cellular model. Traditionally this testing has been performed on 2D cell culture that does not faithfully represent different intrinsic subtypes with their corresponding cellular and physical microenvironment. Next-generation cancer models (3D spheroids, patient-derived organoids (PDOs) and co-culture models) aim to address this limitation of poor representation of the original tumor heterogeneity. 3D spheroids develop a gradient of oxygen and nutrition that mimics the tumor architecture. Organoid technology provides a further advanced representation of clinical tumor by conserving the subtype lineages and intrinsic heterogeneity. We have established next-generation models of breast cancer, including cells exposed to chronic hypoxia, 3D spheroids, cancer and matched normal organoids. We aim to understand how hypoxia affects the drug response in breast cancer. We are currently using these models to develop a high-throughput drug screening platform. We subject the models to a panel of FDA approved drugs in a 384-well format. We are using a 12-point GI50 curve, in triplicate, with 3-fold dilutions reducing from 30uM to identify the GI50 and maximum reduction in cell viability after five days of incubation. As an end-point, we quantify cell proliferation with Celltiter-glo 3D and Celigo imaging-based assay using propidium iodide and hoechst stain. We are in plan to use this platform for hypoxia specific drug screen.