The estimated Hill function parameters (nH ≈ 4, KH ≈ 2 × 105 molecules/cell) imply that CAR expressions are induced sharply as HER2 abundances increase past 2 × 105 molecules/cell giving rise to the almost binary cytotoxic response (off/on) against healthy cells (∼104.5 HER2 molecules/cell) or tumor cells (>106.5 HER2 molecules/cell). This evidence concerns the gene ERBB2 and neoplasm.