Novel model to evaluate changes in gene expression profile of myeloma cells in vivo following interaction with human BM microenvironment

7613 Background: Interaction between multiple myeloma (MM) cells and the bone marrow (BM) microenvironment plays a critical role in promoting MM cell growth, survival, migration and development of drug resistance. This interaction within the bone marrow milieu is unique and its understanding is important in evaluating effects of novel agents in vitro and in vivo. We here describe a novel murine model that allows us to study the in vivo expression changes in MM cells within the human BM milieu. Methods: In our model, BM stromal and IL-6-dependent human MM cell line, INA-6, tranduced with green fluorescent protein (INA-6 GFP+ ) was injected in human fetal bone chip implanted into SCID mice. At different time points the bone chip was retrieved, cells flushed out and GFP+ MM cells were separated by flow cytometry or purified by CD138 MACS microbeads. Similar isolation process was used on INA-6 GFP+ cells cultured in vitro and used as control. Total RNA was isolated from these cells and gene expression profile analyzed using the HG-U133 array chip (Affymetrix). Results: We report that interaction between INA-6 cells and the BM microenvironment in vivo induced significant changes in expression profile; specifically, we observed up-regulation of genes implicated in cell growth; DNA transcription; chromosome structure; cell-cell signaling and adhesion. We also observed down-regulation of genes involved in apoptosis and cell death. To determine which biological pathways are modulated by interaction between MM cells and human stroma, all genes were subjected to Ingenuity Pathway Analysis. Our results indicate that the most relevant pathways modulated by the interaction between MM cells with BMSCs are involved in cell-cycle regulation, apoptosis and integrin signaling, as well as with IL-6, IGF1 and PI3K/AKT, p38-MAPK and ERK/MAPK-mediated pathways. These results are consistent with previously observed in vitro cell signaling studies. Conclusions: Taken together these results highlight the ability of BM microenvironment to modulate the gene expression profile of the MM cells in vivo. This model now provides us with an opportunity to study in vivo effects of novel agents on MM cells expression profile, to pre-clinically characterize their activity. No significant financial relationships to disclose.