ERBB2 and pituitary tumor: In GH3 rat lactosomatotroph pituitary tumor cells transfected with EGFR2, lapatanib, a dual EGFR/ErbB1 and HER2/ErbB2 TKI, has been shown to suppress prolactin mRNA expression and secretion, and reduce tumor volume to a greater effect than gefitinib in both in vivo rat models and in vitro human prolactinoma cell lines [56].