ERBB2 and neoplasm: Hernandez-Lopez and colleagues further harnessed the SynNotch system to increase specificity for HER2+ tumors devising a low-affinity HER2-SynNotch that gated expression of a high-affinity HER2 CAR, showing effective in vivo induction by tumor cells expressing HER2 in the range of 107 molecules per cell but not 60,000 molecules per cell (100).