EDITORIAL COMMENT

The etiopathogenesis of cancer has not been fully outlined yet. Genetic, epigenetic mechanisms and microenvironment play a major role in the etiopathogenesis of cancer. A new phrase is being used for cancer in the recent literature: ‘’stem-ness’’ accounts for the dormancy, regeneration, heterogeneity, immunity and metastasis of cancer. In 1855, R. Virchow proposed that cancers arise from the activation of dormant, embryonic-like cells present in mature tissue. After this theory, Lapidot provided the first evidence to support the cancer stem cell (CSC) hypothesis when they used cell-surface protein markers to identify a relatively rare population of stem-like cells. CSCs in solid tumors have since been identifed using cell-surface protein markers in tumors of the prostate. There are many hypotheses in the literature about the relationship between cancer and stem cell. These hypotheses are focused on cancer cells arising from stem cells or progenitor cells or differentiated cells. Cancer cells and stem cells are like mirror images of each other. There appears to be malignant potential in every stem cell and stem cell potential in malignant cell. Both of them have some features as drug resistance, evading apoptosis, proto-oncogene/oncogene, immunity, tissue invasion and metastasis/morphogenesis and migration, heterogeneity/multipotentiality, active telomerase, onco-niche/stem cell niche, asymmetric divisions/aneuploidy, sustained angiogenesis, limitless self-renewal potential, and hypoxia. Many researchers belive that in the near future the characterization of CSCs will likely play a role in the development of novel targeted therapies.