Metastatic cancer stem cells: from the concept to therapeutics.

Metastatic cancer stem cells (MCSCs) refer to a subpopulation of cancer cells with both stem cell properties and invasion capabilities that contribute to cancer metastasis. MCSCs have capability of self-renewal, potentials of multiple differentiation and development and/or reconstruction of cancer tissues. As compared with stationary cancer stem cells, MCSCs are capable of invasion to normal tissues such as vasculatures, resistance to chemo- and/or radio-therapies, escape from immune surveillance, survival in circulation and formation of metastasis. MCSCs are derived from invasive cancer stem cells (iCSCs) due to the plasticity of cancer stem cells, which is one of the characteristics of cancer cell heterogeneity. Both stages of iCSCs and MSCSs are the potential therapeutic targets for cancer metastasis in the future strategies of personalized cancer therapy.