ERBB3 and neoplasm: To evaluate whether Erbb3 upregulation in MMTV-NeuNT tumors was selective or whether these tumors displayed elevated expression of other ERBB family members, we also examined the expression of Erbb4. Expression of Erbb4 in both normal cohorts was similar and was significantly reduced in tumors (Figure 4I) (normal versus tumor in Control p = 0.0310 and MARKO p = 0.0272).