Abstract 1684: Inflammatory signaling genes as predictive markers of vorinostat sensitivity in multiple myeloma

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Purpose: The objective of this preclinical study is to identify a gene signature that can predict therapeutic responses to vorinostat (SAHA, SuberoylAnilide Hydroxamic Acid), an inhibitor of histone deacetylases (HDACi), which is currently under investigation in multiple myeloma. This is essential for identifying responding patients from nonresponders (intrinsic resistant) to vorinostat who may benefit from alternative treatment. Experimental Design: To determine the antimyeloma effects of vorinostat, bone marrow aspirates from 24 myeloma patients were treated with increasing concentrations of vorinostat (0 − 1 μM) for 72 hrs. The percentage reduction and loss of myeloma cell (CD138+) viability was assessed by Flow Cytometry after staining with FITC conjugated anti-CD138 antibody and 7AAD. CD138+ cells from sensitive (IC50 ≤1 μM) and resistant (IC50 >1 μM groups were enriched to >80% by magnetic separation. Basal gene expression profiles of sensitive and resistant groups were determined using a 48 k Illumina expression array. TM4-MeV software was used to analyze the gene array data to identify genes that were differentially expressed in sensitive and resistant groups, which was confirmed by qRT-PCR and western blotting. Results: Among 24 fresh myeloma samples analyzed, vorinostat achieved IC50 in 10 (41.7%) and IC75 in 5 (20.8%) samples. Nine samples (37.5%) were vorinostat resistant. Non-parametric analysis of gene expression array results identified differential expression of 118 genes (>2x increase in median expression with a P ≤0.05) between sensitive (70 genes) and resistant (48 genes) groups. Interestingly, Ingenuity Pathway Analysis suggested a correlation between differential activation of inflammatory signals and vorinostat sensitivity of myeloma. 17 genes for interferon (IFN) signaling were constitutively expressed in the sensitive group whereas 13 genes related to TNF/IL-6 signaling were predominant in the resistant group. Based upon these results, we hypothesized that IFN-α2b pretreatment would sensitize myeloma cells to vorinostat. As predicted, IFN-α2b and sub-IC50 concentrations of vorinostat combinations synergistically (combination indices of <1) reduced the viability of myeloma cell lines. Conclusions: This study identified 118 genes as potential predictors of patient derived fresh myeloma cell sensitivity to vorinostat. After gene data reduction, a signature of IFN stimulated genes was generated for vorinostat sensitivity and genes related to TNF/IL-6 inflammatory signals for vorinostat resistance. In myeloma cell lines, pretreatment of IFN-α2b augmented antimyeloma effects of vorinostat. Further demonstration of thissynergy on fresh myeloma cells and in mouse xenograft models will provide a rationale for combining these two agents for myeloma therapy. 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 1684.