Abstract 550: Transcriptional regulation of the Fanconi Anemia/BRCA DNA repair pathway component FANCD2 following co-culture of bone marrow stroma with multiple myeloma cell lines

Abstract

Abstract MM is an incurable B cell malignancy characterized by the acquisition of drug resistance. To this end, we have recently demonstrated that selected resistance to the melphalan correlated with a RelB/p50 mediated transactivation of FANCD2 in the 8226 LR5 MM cell line.(Oliveira et al. Cancer Res 2009) These results demonstrated a causal relationship between RelB/p50 transactivation of FANCD2, increased DNA repair, and acquired resistance to melphalan. Although numerous genetic alterations have been implicated in acquired MDR in MM, the bone marrow (BM) microenvironment has also been demonstrated to contribute to drug resistance-or environment-mediated drug resistance (EM-DR). Therefore, utilizing the HS-5 bone marrow stromal (BMS) cell line as a model of the EM-DR, we wished determine if co-culture with RPMI 8226 or 8226/LR5 affected expression of FA/BRCA DNA repair pathway components. Examination of drug sensitive, drug resistant MM, and stromal cell lines demonstrated differential enhancement of FA/BRCA DNA repair pathway protein expression. These preliminary results demonstrate that expression of FA/BRCA pathway components is regulated by cellular interactions in both MM cells and BMSC suggesting that juxtaposed bone marrow stroma influences FA/BRCA-mediated DNA repair and drug resistance. We previously demonstrated RelB/p50 specific transcriptional regulation of FANCD2 in drug selected MM cells. Here, we demonstrate that co-culture of MM cell lines with BMSCs facilitates NF-kappaB DNA binding activity (0-6hr), suggesting a similar RelB/p50 mediated- transactivation of FANCD2. To further examine this we have stably transfected HS-5 cells with luciferase reporter constructs under the control of the FANCD2 promoter. Following co-culture with RPMI 8226 or 8226 LR5 increased FANCD2 promoter activity was noted at early time points (0.5-6hours), but was diminished by 24 hours. FANCD2 promoter activity correlates with protein expression in HS-5 cells incubated with either cell line (0-6hrs). However, in HS-5 cells co-cultured with RPMI 8226 cells FANCD2 protein levels were maintained even after promoter activity had subsided. These data illustrate a novel transcriptional control of FANCD2 in under co-culture conditions. Moreover, these findings suggest that the FA/BRCA mediated DNA damage repair may be an important component of EM-DR. However, continued investigation will be needed to determine the breadth of transcriptional (and/or alternate) regulation of FAND2 and other members of the FA family. Further, future studies will examine a causal relationship between increased FANC expression and melphalan (and other drug) resistance seen in co-culture conditions. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 550.