RESUMO
Chromatin is more than a simple staining structure inside the nucleus. It represents a level of organization that regulates transcriptional activation in eukaryotic genes; this may be through epigenetic modifications such as DNA methylation, histone acetylation, deacetylation and methylation, and chromatin remodeling complexes. Chromatin can have a direct impact on regulating gene expression. Several human diseases arise from alterations of epigenetic regulation, causing change in chromatin structure: cancer is not the exception. The expression of tumor suppressor genes can be epigenetically silenced by DNA methylation of their promotor regions. In other cases such as leukemias, imbalance of histone acetylation and deacetylation can be a determinant event to induce a leukemic phenotype. Finally, improper imprinting can also be associated with neoplastic transformation as in Wilms tumors and sporadic colon cancer. All this evidence supports our particular attention to the study of chromatin structure in cancer. The use of compounds that modify chromatin to improve effects of radio- and chemotherapy will open new horizons in what we call Chromatin Therapy in cancer.