HIF1A and neoplasm: However, earlier studies found that TKIs such as erlotinib do not sufficiently reduce the nuclear HIF-1α and c-Myc protein levels in PC-9 (EGFR exon 19 deletion) xenograft mouse model when used alone, but a combination of erlotinib + cisplatin produced significant nuclear HIF-1α and c-Myc downregulation and tumor size inhibition (Lee and Wu, 2015).