Published online Jan 26, 2015. doi: 10.4252/wjsc.v7.i1.137
Peer-review started: July 28, 2014
First decision: September 16, 2014
Revised: October 14, 2014
Accepted: October 28, 2014
Article in press: December 16, 2014
Published online: January 26, 2015
Processing time: 170 Days and 3.2 Hours
Recent advances in stem cell biology have shed light on how normal stem and progenitor cells can evolve to acquire malignant characteristics during tumorigenesis. The cancer counterparts of normal stem and progenitor cells might be occurred through alterations of stem cell fates including an increase in self-renewal capability and a decrease in differentiation and/or apoptosis. This oncogenic evolution of cancer stem and progenitor cells, which often associates with aggressive phenotypes of the tumorigenic cells, is controlled in part by dysregulated epigenetic mechanisms including aberrant DNA methylation leading to abnormal epigenetic memory. Epigenetic therapy by targeting DNA methyltransferases (DNMT) 1, DNMT3A and DNMT3B via 5-Azacytidine (Aza) and 5-Aza-2’-deoxycytidine (Aza-dC) has proved to be successful toward treatment of hematologic neoplasms especially for patients with myelodysplastic syndrome. In this review, I summarize the current knowledge of mechanisms underlying the inhibition of DNA methylation by Aza and Aza-dC, and of their apoptotic- and differentiation-inducing effects on cancer stem and progenitor cells in leukemia, medulloblastoma, glioblastoma, neuroblastoma, prostate cancer, pancreatic cancer and testicular germ cell tumors. Since cancer stem and progenitor cells are implicated in cancer aggressiveness such as tumor formation, progression, metastasis and recurrence, I propose that effective therapeutic strategies might be achieved through eradication of cancer stem and progenitor cells by targeting the DNA methylation machineries to interfere their “malignant memory”.
Core tip: Several types of cancers can be developed from genetic and/or epigenetic instabilities of stem and progenitor cells. Epigenetic abnormality involving dysregulation of DNA methylation has been reported to implicate in cancer aggressiveness. Inhibition of DNA methyltransferase activity by DNA methylation inhibitors has shown promising results toward treatment of myelodysplastic syndrome, a disease associated with leukemic stem cells. This review summarizes evidences which are pertinent to the antitumorigenic potential of DNA methylation inhibitors 5-Azacytidine and 5-Aza-2’-deoxycytidine on cancer stem and progenitor cells including those of leukemia and other solid tumors.