Cyclo(Arg-Gly-Asp-D-Phe-Cys) (Cyclo RGDfC), a cyclic RGD peptide which has high affinity to αvβ3, can disrupt cell integrin interactions. Cyclo(Arg-Gly-Asp-D-Phe-Cys) inhibits pluripotent marker expression in embryonic stem cells (ESCs) and the tumorigenic potential of mESCs in vivo. Cyclo(Arg-Gly-Asp-D-Phe-Cys) can be used in the research of tumors.