BACKGROUND: Multiple myeloma (MM) is still a fatal plasma cell cancer. Novel 
compounds are currently clinically tested as a single agent in relapsing 
patients, but in best cases with partial response of a fraction of patients, 
emphasising the need to design tools predicting drug efficacy. Histone 
deacetylase inhibitors (HDACi) are anticancer agents targeting epigenetic 
regulation of gene expression and are in clinical development in MM.
METHODS: To create a score predicting HDACi efficacy, five MM cell lines were 
treated with trichostatin A (TSA) and gene expression profiles were determined.
RESULTS: The expression of 95 genes was found to be upregulated by TSA, using 
paired supervised analysis with Significance Analysis of Microarrays software. 
Thirty-seven of these 95 genes had prognostic value for overall survival in a 
cohort of 206 newly diagnosed MM patients and their prognostic information was 
summed up in a histone acetylation score (HA Score); patients with the highest 
HA Score had the shorter overall survival. It is worth noting that MM cell lines 
or patients' primary MM cells with a high HA Score had a significant higher 
sensitivity to TSA, valproic acid, panobinostat or vorinostat.
CONCLUSION: In conclusion, the HA Score allows identification of MM patients 
with poor survival, who could benefit from HDACi treatment.