Abstract 320: Perfused 3D tri-culture breast cancer microtumors for accurate prediction of drug response

Background: Breast cancer (BC) occurs in 1 of 8 women, often requiring debilitating surgery, chemotherapy or radiation for long term survival. Histologic and molecular biomarkers are used to classify BC according to defined subtypes which dictate the choice of targeted therapy or of non-targeted cytotoxic therapy. Despite high initial response rates, relapses are common for more aggressive tumors, and choosing the right therapy for each patient remains challenging. In vitro 3D BC models maintain biologic features that more closely resemble clinical disease than 2D models. However, many 3D models do not contain multiple cell types, are maintained in static culture conditions and rely on immortalized cell lines previously propagated in 2D culture conditions. To address these issues, we developed long term, 3D heterotypic BC microtumors, which recapitulate the dynamic interaction between stromal and epithelial components, retain subtype-specific biomarkers and demonstrate clinically-relevant drug response. We further demonstrated the value of developing non-lytic, label-free in situ analysis to monitor morphology and function of complex 3D microtumors over time. Materials & Methods: Er+, Her2+ or triple negative (TNBC) cell lines (MCF7, SKBR3, MDA-MB-231) or patient derived xenograft (PDX) cells were embedded with human mammary fibroblasts and adipose cells within a hydrogel encapsulated by a silk fibroin scaffold. Microtumors were maintained at least 4 weeks under perfusion flow utilizing the 3DKUBE™ and were characterized for cell morphology and phenotype (IHC), proliferation (PrestoBlue and PicoGreen), gene expression (qRT-PCR), redox ratio (multiphoton microscopy), and biomarker secretion (xMAP® multiplex immunoassay). Drug response profiling (DRP) was performed with tamoxifen, lapatinib and cisplatin. Results: 3D microtumors successfully recapitulated the morphology of primary BC predicted by molecular subtype and gene expression. Perfusion promoted cell proliferation and impacted redox ratio, gene expression, and biomarker secretion in comparison to static culture. Relative redox ratios of 3D microtumors were significantly different from those of cell lines in 2D (p