Review of the clinical experience with 5-azacytidine and 5-aza-2'-deoxycytidine in solid tumors.

In recent years the importance of epigenetic changes in carcinogenesis has been unfolding. It is now clear that the fifth base of the genome, methylcytosine, plays a critical role in the control of gene expression during normal development and carcinogenesis. Efforts to decrease methylation in neoplasias as a therapeutic strategy have been productive in hematologic malignancies but disappointing in solid tumors. The following is a review of the clinical experience with the agents 5-azacytidine and 5-aza-2'-deoxycytidine in solid malignancies and a discussion of the difficulties encountered.