By Rooney and Hacohen, Cell, 2015. Cytolytic activity (CYT) Measuring cytolytic activity (CYT): using granzyme and perforin levels. CYT activity varies across tumor types: in some tumors, e.g. kidney and cervical cancer, strong induction; but in others, e.g. breast cancer, no. Correlated genes with CYT: other genes that are markers of CYT activity; also positive correlation with genes usually not expressed in CTLs and NK cells, some are immunosuppresive molecules.