H19 and cancer: Among these genes, 19 genes were upregulated by >4-fold in metastatic sites compared with their levels in orthotopic sites, and the most strongly overexpressed gene in the metastatic tumors was oncogenic long non-coding RNA H19, which was reported to promote cancer progression and metastasis in many cancers, including SCLC [27,28,29,30] (Table 1).