Integrins emerge nowadays as crucial actors of tumor aggressiveness and resistance to therapies. Integrin α5β1, the fibronectin receptor, determines malignant properties of colon carcinoma which is one of the most important causes of cancer-related deaths in the world. Here we show that inhibition of α5 integrin subunit expression by siRNA or α5β1 integrin function by specific antagonist affects the survival of HCT116 colon cancer cells. We also evidence that pharmacological reactivation of the tumor suppressor p53 by Nutlin-3a inhibits specifically the expression of the α5 integrin subunit both at the transcriptional and protein level. Inversely repression of α5 integrin modulates p53 activity. A clear relationship between p53 activation by Nutlin-3a, α5 repression and cell survival is shown. No such effects are obtained in cells lacking p53 or when another non-genotoxic activator of p53, RITA, is used. Our results emphasize the crucial role of α5β1 integrin in colon tumors. Data also suggest that interfering with the integrin α5β1 through the reactivation of p53 by Nutlin-3a may be of valuable interest as a new therapeutic option for colon tumors expressing high level of the integrin and a wild type p53.