Initiation of cancer may be the result of mutations occurring in stem cells, which causes blocking the differentiation of these cells. Many common properties of the stem cells and some tumor cells suggests that cancer stem cells may be responsible for the initiation and progression of cancer. The special properties of CSC is the ability to self-renewal and cell proliferation, which are the major cause of cancer recurrence and metastasis. Signaling pathways (Wnt, Notch, Shh) and pluripotency- connected transcription factors (Oct-4, Nanog) are primarily responsible for cell proliferation. Understanding the causes of initiation and progression of cancer is crucial for improving treatment of these life-threatening diseases.