ABSTRACT
Aim To establish NCI-H446/EP for small cell lung cancer resistant cells resistant to cisplatin and etoposide, and to evaluate their biological characteristics and multidrug resistance. Methods Nude mice were subcutaneously inoculated with NCI-H446 cells of SCLC to construct an in vivo model of xenograft tumor, and were given first-line EP regimen treatment for SCLC, inducing drug resistance in vivo, and stripping tumor tissue in vitro culture to obtain drug-resistant cells. The resistance coefficient, cell doubling time, cell cycle distribution, expression of multidrug resistance gene (MDR1), and drug resistance-related protein were detected in vitro, and the drug resistance to cisplatin and etoposide in vivo were verified. Results Mice with NCI-H446 tumors acquired resistance after eight weeks' EP regimen treatment, and the drug-resistant cell line NCI-H446/EP was obtained by isolation and culture in vitro. The resistance factors of this cell line to cisplatin, etoposide, SN38 and doxorubicin were 12.01, 18.36, 65.4 and 10.12, respectively. Compared with parental cells, the proportion of NCIH446/EP cells in Q
ABSTRACT
<p><b>OBJECTIVE</b>To study the expressions of p35 and p25 and Cdk5 kinase activity in cultured rats hippocampal neurons following X-ray exposure to provide experimental evidence for prevention and treatment of radiation encephalopathy.</p><p><b>METHODS</b>The hippocampal neurons cultured for 12 days were subjected to a single-dose X-ray exposure of 30 Gy. Western blotting was used to detect the p35 and p25 protein levels, and the effect of pretreatment with roscovitine, a Cdk5 inhibitor, on the apoptosis of the hippocampal neurons following the exposure was examined with 4',6-diamidino-2-phenylindole (DAPI) staining.</p><p><b>RESULTS</b>The protein level of p35 increased significantly 3.5 and 4 h after the irradiation by 1.51-/+0.13 and 1.45-/+0.14 folds in comparison with the control level, respectively (P<0.01), and the p25 level increased significantly 6 h after irradiation by 1.62-/+0.28 folds (P<0.05). Nuclear condensation occurred in (24.8-/+3.97)% of the neurons 24 h after 30 Gy X-ray exposure, a rate significantly higher than that in the nonexposed cells [(1.82-/+1.08)%, P<0.01) and that in roscovitine-pretreated neurons [(7.74-/+2.27)%, P<0.01).</p><p><b>CONCLUSION</b>X-ray exposure activates Cdk5 by increasing the p35 and p25 expressions in rat hippocampal neurons, and inhibition of Cdk5 activity with roscovitine can significantly protect the neurons from apoptosis.</p>