The present invention relates to a method of testing whether a patient suffering of myeloma will respond or not to a histone deacetylase inhibitor (HDACi) comprising: determining the expression level (ELi) of several genes G1-Gn selected from table A in a biological sample obtained from said patient comparing the expression level (ELi) determined at step i) with a predetermined reference level (ELRi) iii) calculating the HAS score trough the following formula wherein &bgri represent the regression &bgr coefficient reference value for the gene Gi and Ci=1 if the expression of the gene Gi (ELi) is higher than the predetermined reference level (ELRi) or Ci=&minus1 if the expression of the gene (ELi) is lower than or equal to the predetermined reference level (ELRi) comparing the score HAS determined at step iii) with a predetermined reference value HASR v) and concluding that the patient will respond to the HDACi when the HAS score is higher than the predetermined reference value HASR or concluding that the patient will not respond to the HDACi when the HAS score is lower than the predeference value HASR HAS = &sum i = 1 n &bgr i × Ci ( I )
