Consistent with the test results in breast cancer cell lines, both EGF and NRG1b-driven HER2 signals from primary R54 cells were detected by CELx HSF tests and were dependent on PI3K activation (Fig. 9) but not by MAPK activation (Additional file 8: Figure S6 demonstrated with﻿ lack of activity of trametinib, inhibitor of MEK1/2 in MAPK pathway) for this primary pathway dysfunctional specimen. Here, EGF is linked to breast cancer.