Together, these observations indicate that HER3 activation retains the viability of ALK-TKI-treated cells in vivo and that initial HER3 inhibition improves the response of ALK-rearranged NSCLC tumors to ALK-TKI treatment by promoting apoptosis and preventing recurrence, leading to the potential eradication of tumor activity in ALK-rearranged lung cancer. This evidence concerns the gene ERBB3 and lung cancer.