STIM1 and neoplasm: Indeed, using conditional double knockout mice for T cell-specific Stim1 and Stim2 gene deficiency, the authors showed that both STIM1 and STIM2 are required for tumor killing functions of CD8+ T cells mediated by degranulation, expression of Fas ligand, TNF-α, IFN-γ production and exocytosis of cytolytic granules containing perforin.