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. 2018 Feb 12;8(7):1808–1823. doi: 10.7150/thno.23177

Figure 1.

Figure 1

Acquired resistance to erlotinib requires higher PHGDH level to de novo synthesize glucose-derived serine in NSCLC cells. (A and B) Inhibition rate of cell viability in the indicated cells treated with various concentrations of erlotinib for 72h detected by CCK8 assays. (C) List of the top 13 genes up-regulated in PC9ER4 cells compared to PC9 cells. PC9ER4-s is a stable clone passaged in 5 μM erlotinib containing medium continuously. The mRNA (D) and protein (E) levels of PHGDH were determined by qRT-PCR and immunoblotting respectively. (F) Profiling of 20 amino acids consumption in the medium obtained from 72h cultured cells by LC-MS/MS. Serine is the top one amino acid expended by the erlotinib resistant cells. (G) The histogram of the serine consumed described above. (H) Intracellular serine concentration was quantified by LC-MS/MS in the cell extracts after 72h culture. (I) Concentration of serine secreted to Kreb's buffer from cells at various time-point was also detected by LC-MS/MS. (J) Intracellular serine (M+3) concentration was quantified by LC-MS/MS in the cell extracts after 6h culture. Results were shown as mean ± SEM of triplicates. *, p < 0.05; **, p < 0.01; ***, p < 0.001; ****, p < 0.0001.