FIGURE 7.

Effect of receptor expression levels on phenotype. Computations were performed for cells coexpressing 200,000 EGFR molecules and varying levels of HER2 and HER3 molecules. In both plots the receptor expression levels have units of thousands of molecules. (A) Critical HER2 required to match the phenotype P* of the reference cell line as a function of HER3 expression at three different β-values (EGFR-HER3 potencies). For all cases, HER2-HER3 potency is set at γ = 1. (B) Critical HER2-HER3 potency γ required to match P* for cell lines expressing varying levels of HER2 and HER3. For all cases, EGFR-HER3 potency is set at β = 0. Results indicate that coexpression of all three receptor subtypes at low-to-moderate levels may enable a cell to match the phenotype of a high HER2 expresser.