Summary of expression of PTEN and phosphorylation of Akt in 23 lung cancer cell lines grown under serum-containing (cross bars) and serum-free (black bars) conditions. (A) The ratio of phosphorylated Akt signal/total Akt signal (pAkt/Akt); (B) the ratio of PTEN signal/β-actin signal; The density of expression of each of the molecules was measured by NIH Image. Point: mean of three independent experiment; bars, ± standard deviation (SD). The expression ratio of the molecules in serum-free conditions was compared between gefitinib-resistant and gefitinib-sensitive cell lines using the Mann-Whitney test; point, mean, bars, ± standard error (SE). *P < 0.05 was considered to be statistically significant.