The short hairpin RNA (shRNA) specifically against BRAF and the scramble control shRNA were cloned into the lentiviral vector pSicoR-PGK-puro (#12084, Addgene, Cambridge, MA)52. A pLKO.1-puro based lentiviral vector expressing shRNA against TERT (#TRCN0000240466), FOS (#TRCN0000016007) and MYC (#TRCN0000039642) were purchased from Sigma-Aldrich and the pLKO.1-puro vector with scramble shRNA was purchased from Addgene (plasmid #1864). To generate lentiviral particles, the lentiviral shRNA-expressing vector with the packaging plasmid PSPAX2 and the VSV-G envelope protein-coding plasmid pMD2.G were co-transfected to HEK293T cells using Lipofectamine 3000 (Invitrogen) and the supernatant was harvested 48 h after transfection. To generate cell lines with stable knockdown of BRAF, TERT, FOS or MYC, cancer cells were exposed to the above lentivirus-containing supernatant for 24 h in the presence of 8 μg ml−1 polybrene (Millipore, Billerica, MA) and selected by 2 μg ml−1 puromycin (Sigma-Aldrich) for 2 weeks. The stable transfection cell pools were confirmed by western blotting analysis of the proteins of interest.