Histone deacetylase is a metallo-enzyme with zinc at the active site. Compounds having a zinc-binding moiety, for example, a trihalomethylcarbonyl group, such as a trifluoromethylcarbonyl group, can inhibit histone deacetylase. Histone deacetylase inhibition can repress gene expression, including expression of genes related to tumor suppression. Accordingly, inhibition of histone deacetylase can provide an alternate route for treating cancer, hematological disorders, e.g., hemoglobinopathies, autosomal dominant disorders, e.g. spinal muscular atrophy and Huntington's disease, genetic related metabolic disorders, e.g., cystic fibrosis and adrenoleukodystrophy, or for stimulating hematopoietic cells ex vivo.