Cytotoxic T effector cells have been shown to be the main source of anti-tumor immune response.23,35 The aggregated transcript levels of genes (Teff signature) representing Granzyme A (GZMA), Granzyme B (GZMB), Perforin 1 (PRF1), Eomesodermin (EOMES), and CD8A can be closely associated with density of CD8+ T cells measured by IHC. The gene discussed is PRF1; the disease is neoplasm.