Compositions and methods are provided for treating diseases associated with aberrant silencing of gene expression such as cancer and hematological disorders by reestablishing the gene expression through inhibition of DNA hypomethylation and histone deacetylase. The method comprises: administering to a patient suffering from the disease a therapeutically effective amount of a DNA methylation inhibitor such as a cysteine analog such as decitabine, in combination with an effective amount of histone deacetylase inhibitor such as hydroxamic acid, cyclic peptide, benzamide, butyrate, and depudecin.