Cells attached to the flasks were treated with 100 nmol/L gefitinib, meanwhile, irradiated with graded doses of x-rays, rinsed after 48-hour incubation in drug-containing medium, and allowed to form colonies in drug-free medium. Surviving fractions for radiation + MK0683 gefitinib were normalized by dividing by the surviving fraction for gefitinib only. Each test was performed 3 times. The radiation-enhancing (t = 7.65, P < 0.01) effect of gefitinib was comparable with that of gefitinib alone in H-157 cells. (B) Effects of gefitinib on H-157 cell growth after irradiation. There was no significant difference (t = 1.13, P > 0.05) in the growth rates between H-157 cells and gefitinib-treated

cells as determined by cell counting, but the proliferative ability check details of the gefitinib and radiation treated cells was dramatically suppressed(t = 5.01, P < 0.05)in contrast with radiation-treated only. Gefitinib increased the radiation-induced apoptosis As shown in Figure 5. The early apoptosis rate among gefitinib-treated H-157 cells after 6 Gy irradiation was significantly higher than the cells with the same dosage of X-rays only. Whereas, no significant apoptotic changes were observed in unirradiated cells before and after gefitinib treated. Quantitative measurements of apoptotic cell

death by FCM in H-157 cells sufficiently indicated that the radiation-induced overexpression of PTEN significantly enhanced gefitinib-induced apoptosis in comparison GSK1904529A research buy with that of the control (no irradiation). Figure 5 Gefitinib-induced apoptosis in H-157 cells before and after irradiation. Attached cells were exposed to 6 Gy irradiation and then treated with 100 nmol/L gefitnib. After additional 48-hour incubation

in medium containing the drugs, the cells were harvested. The apoptotic index (AI) was measured using flow cytometry. (A) Control groups (AI: 1.36 ± 0.74%). (B) Apoptotic values after treatment with 100 nmol/L gefitinib alone (AI:3.58 ± 0.61%).(C) Radiation- induced apoptosis induction (14.26 ± 2.97%% of total cells) in H-157 cells.(D) Radiation combined with gefitinib induced apoptosis induction (23.58 ± 3.61% of total cells). Apoptotic values were normalized by subtracting control values; Urease the normalized apoptotic values were used for statistical analyses. Experiments were done in triplicate. Combined drug treatments were shown to enhance radiation-induced apoptosis in H-157 cells (t = 19.91, P < 0.01), but no synergistic manner when compared with drug alone without radiation (t = 2.569, P > 0.05). Discussion The PI3K pathway is a critical effector of growth, proliferation, and survival pathways. PTEN serves as negative regulator of the phosphatidylinositol 3-kinase (PI3K) pathway by removing the third phosphate from the inositol ring of the second messenger PIP3 [29]. PTEN inactivation results in accumulation of PIP3 levels and persistent signaling through the serine/threonine kinase Akt/protein kinase B.