Abstract 4049: Stromal Wnt/β-catenin antagonism with DKK1 promotes clonal expansion of multiple myeloma is identified using hyaluronic acid based 3D hydrogel

Abstract

Abstract Multiple myeloma (MM), an incurable cancer with 3- to 5-year survival is characterized by monoclonal immunoglobulin (Ig), lytic bone lesions and monoclonal plasma cells (PCs) in the bone marrow (BM). Because clonal expansion of primary MM cells outside their BM microenvironment has been unsuccessful, most pre-clinical studies have used MM cell lines derived from leukemic-phase cells that have escaped BM dependence. Therefore it is likely that BM niches maintain MM cancer stem cells (MM-CSCs) in a quiescent, drug-resistant state. To date, pre-clinical models do not take into account adhesion-mediated drug resistance and none allows for testing of drug efficacy on MM-CSC populations. Mouse models of MM are inadequate for pre-clinical use because they cannot faithfully recapitulate human disease. Recently, a stromal spheroid co-culture model and various scaffolds have been developed to recreate the 3D environment of the BM. To adequately investigate underlying mechanisms of B-cell development and the stromal influence on MM pathogenesis, there is a great need for a 3D cell culture system. In the present study, we used hyaluronic acid based 3D hydrogel for surface seeding and encapsulation of human multiple myeloma (BMMCs) and the bone marrow stromal cells (BMSCs) to investigate MM clonal migration and the new phenotype exhibiting cellular changes associated with Wnt/βcatenin signaling. For the first time we report, (a) hyaluronic acid HA-based 3D hydrogels with difference in the matrix composition and stiffness provide a suitable substratum for migration and clonal expansion of human primary BMMCs; (b) Homogenous encapsulation of 5x105 BMMCs showed development of small colonies identified as multiple thin, flat cells emanating from a central cluster of rounded cells as colony forming units (CFUs). We observed an increase in CFUs in hydrogel with medium stiffness of Me-HA at 14 days (ranging from 16 to 17%, p<0.05) and at 21 days (ranging from 26 to 27%, p<0.01) in contrast to that in 2D or in a commercial matrigel; (c) immunofluorescence detection of cytoplasmic and nuclear expression of β-catenin showed a higher expression (>4 fold) in the 3D encapsulated differentiating cells compared to that in the non-differentiating single cells; (d) our findings using ELISA assays for sDKK1 showed a gradual increase in DKK1 with a maximum at 21 days (p<0.001), suggesting the possible influence of stromal BMSCs on DKK1 production in contrast to earlier reports of DKK1 inhibiting Wnt signaling. Our findings support the use of 3D (ex vivo system) hydrogel for MM to dissect the Wnt-β-catenin/DKK1 signaling activities and further to screening for drug targets in bone-related human multiple myeloma. Citation Format: Bhagavathi A. Narayanan, Bin Duan, Jonathan T. Butcher, Amitabha Mazumder, Narayanan K. Narayanan. Stromal Wnt/β-catenin antagonism with DKK1 promotes clonal expansion of multiple myeloma is identified using hyaluronic acid based 3D hydrogel. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4049. doi:10.1158/1538-7445.AM2014-4049