Using a ratiometric ACPP probe co-labeled with Cy5 and Cy7 (Fig. 1j, Supplementary Fig. 6a), whole animal imaging established that i.v. injected ACPP is selectively cleaved and accumulates within routinely used pre-clinical LL/2 and MC38 murine syngeneic cancer models in situ (Fig. 1k, Supplementary Fig. 3e)49,50. This evidence concerns the gene ACP3 and cancer.