Abstract 1518: Multiple myeloma cells cross talk with bone marrow stroma lead to induction of DKK1 expression and produce bortezomib resistance

Abstract

Abstract The importance of the micro-environment in tumor progression is now well established. Dynamic interaction between multiple myeloma (MM) cells and bone marrow stromal cells (BMSCs) plays critical role in the progression of MM including drug response and bone erosion. Firstly, we found that DKK1 expression was statistically increased in MM cells (MOLP8, KMS12BM, KMS12PE, NCIH929, LP1, MOLP2, EJM, U266, RPMI8226, and 536MM, respectively) co-cultured with BMSCs obtained from MM patients when compared to MM cells alone (p<0.05). Also, MM cells co-cultured with BMSCs were significantly more resistant against 25 nM bortezomib than MM cells alone (p<0.05). We, therefore, established a bortezomib-resistant cell line using U266 cells (U266/velR), and explored the characteristics of U266/velR cells. Cytotoxic effect of bortezomib in U266/velR was 1.5 folds lower than U266 cells, and the cross-resistance against thalidomide was observed. DKK1 expression in U266/velR was higher than that in parental cells. We found that elevated levels of p-p65 were detected in U266/velR, and the degree of p65 and I-κB expression levels reduced by bortezomib was different between U266/velR and U266. Elevated levels of p-p65/p65 were effectively suppressed by treating with NF-κB activator inhibitor (6-aminoquinazoline). Also, combined treatment of bortezomib and 6-aminoquinazoline reduced the expression of DKK1 in co-culture of U266 cells and BMSCs. The expression of HGF in CD138− fractions of MM bone marrow cells was higher than that in its CD138+ fractions. Whereas, IL-6 and OPN in CD138+ fraction of MM bone marrow cells was higher compared to its CD138− fractions. In co-culture of U266 and BMSCs, IL-6, OPN and HGF was dramatically increased compared to U266 alone and BMSC alone (p<0.01; p<0.05). Taken together, cytokines and growth factor regulated by dynamic interplay between MM cells and BMSCs contributes the bortezomib response and bone erosion. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1518. doi:1538-7445.AM2012-1518