ERBB4 and ovarian cancer: EGFR, ERBB2, ERBB4, and MET immunoprecipitations in SKOV3, EGFR, MET, and AXL immunoprecipitations in OVCA429, and EGFR immunoprecipitation in ES2, from DMSO vs. 17-AAG treated ovarian cancer cells confirmed 17-AAG mediated inhibition of multi-RTK tyrosine phosphorylation, as demonstrated by phosphotyrosine (PY99) immunostaining (Figure 4A).