The Effects Of Combined Administration Of Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors And Cytotoxic Drugs In Different Tumor Cell Lines

Partâ… :The effects of concurrent administration of different cytotoxic drugs with geftinib or erlotinib in different tumor cell lines[Purpose]This study was undertaken to observe the effects of concurrent administration of different cytotoxic drugs with gefitinib or erlotinib in A549, SPC-A1,LTEP-a-2,H292,A431 and PC-9 cells,and to evaluate the interaction between these two drugs.[Methods]EGFR expression was measured by immunohistochemical method.The two-step polymerase chain reaction was used to detect K-ras codon mutation.All the cell lines were exposed to different cytotoxic drugs combined with gefitinib or erlotinib in a certain concentration concurrently.The antitumor effect was measured by growth inhibition by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.The cell survival percentage of cells treated with combined traetment was compared with that of cells treated with single cytotoxic drugs.The cytotoxic drugs included docetaxel,pemetrexed,gemcitabine,vinorelbine,cisplatin and adriamycin.The cytotoxic interaction between erlotinib and gemcitabine(i.e., synergistic,additive,or antagonistic) was determined by median effect analysis.[Results]When cells were exposed to concurrent gefitinib or erlotinib and one of different cytotoxic drugs such as docetaxel,pemetrexed,gemcitabine,vinorelbine, adriamycin and cisplatin,the cell survival percentages of the combination drug treatment groups increased in all cell lines,which changed only 10-20%in SPC-A1, A549,LTEP-a-2 cell lines without any statistical differences,but up to nearly 50%in H292,A431,PC-9 cell lines with significantly statistical differences.The combination index(CI) of concurrent administration of erlotinib and gemcitabine identified different effects between these two drugs in these cell lines,which was additive effects in SPC-A1,A549 and LTEP-a-2 cell lines(CI at ED50 were 0.85,1.55 and 1.02, geometric mean of CI for experimental values were 0.9,1.02 and 0.98),moderate synergitic effect in H292 and synergitic effect in A431 and PC-9 cell lines(CI at ED50 were 0.60,0.52 and 0.93,geometric mean of CI for experimental values were 0.73,0.44 and 0.37).[Conclusion]This in vitro trial suggested when concurrently administered gefitinib or erlotinib with cytotoxic drugs,the interaction between them differs from cell lines. The sesitivitiy to EGFR-TKIs,maybe the potential biology background were due to this interaction.Partâ…¡:The effects of sequential administration of erlotinib and gemcitabine in A549,SPC-A1,H292 and PC-9 cell lines[Purpose]The study was undertaken to observe the interaction between gemcitabine and erlotinib when administered sequentially in A549,SPC-A1,H292 and PC-9 cell lines.In addition,we tried to find possible mechanisms of the interaction and to provide evidence for clinical treatment.[Methods]The cells were exposed to erlotinib and gemcitabine in different schedules (erlotinib followed by gemcitabine and gemcitabine followed by erlotinib).The antitumor effects were measured by growth inhibition by 3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide assay.The cytotoxic interaction between erlotinib and gemcitabine was determined by median effect analysis.Cell cycle distribution and induction of apoptosis were measured by flow cytometry.[Results]When cells were exposed to sequential gemcitabine followed by erlotinib, cytotoxic synergism was observed in all cell lines.CI at ED50 were 0.16,0.66,0.47 and 0.16,geometric mean of CI for experimental values were 0.28,0.81,0.53 and 0.19.In contrast,exposure of cells to erlotinib followed by gemcitabine was mostly antagonistic in PC-9 cell(CI at ED50 was 3.13,geometric mean of CI for experimental values was 2.02) and additive or slight synergism at best in other three cells(CI at ED50 were 1.21,0.96 and 1.15,geometric mean of CI for experimental values were 0.92,1.12 and 0.75).Antagonism was associated with erlotinib-induced G1-phase blockade which protects cells from gemcitabine cytotoxicity.[Conclusion]The combination of pemetrexed and erlotinib is synergistic in NSCLC in vitro if exposure to erlotinib before pemetrexed is avoided,particularly in tumors that are sensitive to erlotinib.