NRG1 and neoplasm: Based onthese observations; on histopathological data showing EGFR expression by myoepithelial cells, keratinocytes and squamoustumors [22],[23]; and on the fact that EGF promotes expansionof the myoepithelial layer in short term organoid cultures [3], we reasoned that it might be possible toreduce squamous metaplasia in engineered tumor models by decreasing the activationof EGFR and increasing that of ERBB3 and ERBB4. Totest this, we grew normal reduction mammoplasty cells in WIT medium containingeither EGF (“pWIT medium”) or amphiregulin (AREG) plus neuregulin (NRG1) (“svWITmedium”).