Scott J, Mendive Tapia L, Gordon D, Barth N, Thompson E, Cheng Z, Taggart D, Kitamura T, Blas A B, Roberts E W, Juarez Jimenez J, Michel J, Piet B, de Vries I J, Verdoes M, Dawson J C, Carragher N O, O’Connor R A, Akram A R, Serrels A. Frame M C, Vendrell M.
Immunotherapy promotes the attack of cancer cells by the immune system; however, it is difficult to detect early responses before changes in tumor size occur. Here, we report the rational design of a fluorogenic peptide able to detect picomolar concentrations of active granzyme B as a biomarker of immune-mediated anticancer action. Through a series of chemical iterations and molecular dynamics simulations, we synthesize a library of FRET peptides and identify probe H5 with an optimal fit into granzyme B. We demonstrate that probe H5 enables the real-time detection of T cell-mediated anticancer activity in mouse tumors and in tumors from lung cancer patients. Furthermore, we show image-based phenotypic screens, which reveal that the AKT kinase inhibitor AZD5363 shows immune-mediated anticancer activity. The reactivity of probe H5 may enable the monitoring of early responses to anticancer treatments using tissue biopsies.