Profiling gene expression with DNA microarray technology has elucidated novel therapeutic targets and led the approval of a number of targeted therapeutic agents for the treatment of cancer. Vorinostat (suberoylanilide hydroxamic acid, SAHA) is a pan-histone deacetylase (HDAC) inhibitor that has demonstrated an overall response rate of approximately 24–30% in two phase II studies of cutaneous T cell lymphoma (CTCL) patients. There are currently no known specific biomarkers to indicate resistance to vorinostat. To identify genes resistant to vorinostat we compared profiles using the Aligent whole human genome oligo microarrays containing ∼41,000 genes/transcripts in vitro in vorinostat-resistant MJ and -sensitive HH CTCL cell lines treated with 1 μM of vorinostat for 24 hours and compared them to patients’ peripheral blood mononuclear cells (PBMCs) before and during oral therapy. There were 3151 (7.7%) genes/transcripts differentially expressed in vitro in treated resistant MJ cells compared to untreated vehicle control (p < 0.001). We also studied differential gene expression in two clinically resistant Sézary patients’ PBMCs taken at baseline and four weeks after oral vorinostat (400 mg daily or 300 mg bid 3 days/wk). In patients’ PBMCs, 585 (1.4%) and 2744 (6.7%) differentially expressed genes/transcripts (p < 0.001) were identified, respectively. Genes that were up-regulated both in vitro and in vivo included a tumor necrosis factor receptor super-family member 11a (TNFRSF11a or RANK), matrix metallopeptidase 9 (MMP9), suppressor of cytokine signaling 3 (SOCS3), vinculin (VCL) and KIAA1840. Genes that were down-regulated in both included adenylate kinase 3-like 1 (AK3L1), leucine rich repeat and fibronectin type III domain containing 4 (LRFN4), and AL359650. Increased RANK, MMP9 and SOCS3 mRNA expression in MJ compared to HH cells and in three resistant versus three vorinostat responding Sézary patients’ PBMCs was confirmed using quantitative real-time PCR. In conclusion, our results suggest that oligonucleotide microarray analysis may identify biomarkers of resistance to vorinostat which would be helpful to select patients who may not benefit from treatment. These findings provide the rationale for future functional studies and development of more effective use of HDAC inhibitors for CTCL patients.
Disclosure:Research Funding: Vorinostat IISP grant from the Merck & Co.