KRAS and large cell neuroendocrine carcinoma: We next examined if TWIST1 expression was higher in a variety NSCLC patient derived xenografts derived from both primary tumors (MSK-LX29) [29] and brain metastases from KRAS mutant [30] or EGFR mutant adenocarcinomas, squamous cell carcinoma, large cell neuroendocrine carcinoma, and undifferentiated NSCLC tumors.