Described herein are methods and compositions for determining whether a particular cancer is resistant to or susceptible to a histone deacetylase inhibitor or to histone deacetylase inhibitors. The methods include analysis of the expression levels of at least four biomarker genes associated with response to a histone deacetylase inhibitor. Also described herein are methods and compositions for increasing the likelihood of a therapeutically effective treatment in a patient, comprising an analysis of the expression levels of at least four biomarker genes associated with response to a histone deacetylase inhibitor. Also described herein are isolated populations of nucleic acids derived from a cancer sensitive to or resistant to a histone deacetylase inhibitor. Further described are kits and indications that are optionally used in conjunction with the aforementioned methods and compositions.