In this study, we have used the multiplexed CEER platform to determine levels of activated RTKs (HER1, HER2, truncated variants of HER2, i.e., p95HER2, HER3, cMET, PI3K, and IGF1R) in 434 fresh frozen GC tissues and attempted to categorize GC patients into potential subgroups based on their protein pathway activation patterns. The gene discussed is ERBB3; the disease is gastric cancer.