ERBB2 and cancer: Next, to investigate the gene dosage effect for other cancer-related genes (genes included on the UCSF500 panel other than ERBB2) on HER2 expression, we evaluated a logistic regression model to predict HER2 IHC 3+ (vs IHC 0/1+/2+) status while adjusting ERBB2 amplification status as a covariate (Supplementary Methods).