SOX2 and lung cancer: Recent study showed down-regulation of SOX2 gene inhibits proliferation and induces apoptosis in tumor cells [15], [45], [46], we observed the same phenomenon in human lung cancer cell lines (data not shown), those may also be important factors that finally lead to the suppressed tumor growth in A549 cells; however, this study focused on the transcriptional changes of oncogenes and did not address other mechanisms.