Abstract: The theory of cancer stem cells (CSCs) provides a new perspective for the study of cancer. CSCs doctrine presumes that tumor cells are heterogeneity, there are cancer stem-like cells in tumors, whose proliferation is uncontrolled. The cancer stem-like cells could form tumors at the condition of only few cells, this kind of cells only account for a very small part of all the tumor cells. The cells with stem cells characteristics could form different degree of differentiation of tumor cells and they are the root of tumor growth, recurrence and metastasis. MiRNAs are widely-existed non-coding small RNAs, which regulate 1/3 human genes and participate in a series of essential processes of life. More and more evidences indicate that miRNAs contribute significantly to cancer generation and development. They may exhibit oncogenic activity, and act as tumor suppressors. As one of post-transcriptional controlling factors, they extensively regulate biological processes of tumor related genes, and show specific miRNAs expression profiles in different cancers. The research of miRNA about CSCs has become to be forefront. Some studies have confirmed that the miRNAs play a very important role in a variety of CSCs, showing a new target for tumor therapy. Researchers have found that some specific miRNAs express in plasma of cancer patients, these miRNAs can be used as tumor markers in the patient's diagnosis and prognosis prediction. This review is focused on the current research progress about the function of miRNAs in CSCs and as tumor markers.

Key words: Stem cells, Cancer stem cells(CSCs), Cancer stem cells theory, MiRNA