ERBB2 and infection: To investigate the drug sensitivity in relation to the PTEN expression status in HER2-GEA, both NCI-N87 and OE19 cells were used to establish two types of stable PTEN-knockdown clones and a scrambled control clone by lentiviral infection of short hairpin RNAs (shRNAs) (referred to as ‘‘shPTEN#1” and ‘‘shPTEN#2” for each cell line; Supplementary Fig. 1).