Firstly, to test the specificity of tumor targeting by the PPA1-DOX conjugate, we synthesized RhB-PPA1-DOX (fluorescence of PPA1-DOX) and RhB-RAN-DOX (fluorescence of a random polypeptides-DOX) and evaluated the biodistribution of the compound in the CT26-bearing mice after 24h intravenous injection by collecting major organs for ex vivo fluorescence imaging. This evidence concerns the gene PPA1 and neoplasm.