Determinants of Gemcitabine-Pemetrexed Synergism in Pancreatic Cancer Cell Lines

Transcription

1 Determinants of - Synergism in Pancreatic Cancer Cell Lines E. Giovannetti, V. Mey, R. Danesi, I. Mosca, M. Del Tacca Division of Pharmacology and Chemotherapy, Department of Oncology, Transplants and Advanced Technologies in Medicine, University of Pisa, Italy Pancreas Cancer 24 International Symposium Tirrenia, Pisa, April 24

2 Mechanism of action of gemcitabine and pemetrexed (MTA) FPGS ( Glu ) n 5-1 CH 2 - FH (-) 4 dump TS Thymidylate biosynthesis FH 2 1 CHO - FH 4 DHFR PRPP + Glutammine FH 4 AMP GAR Folate metabolism IMP GARFT GARF GMP dtmp damp dgmp purine de novo biosynthesis AICAR HX + PRPP purine salvage biosynthesis Orotate UMP Deoxycytidine pirimidine salvage biosynthesis dcmp dcdp dck /5 - NT RR CDP CDA dfdu (dfdc) dfdcmp dttp datp dgtp dctp (-) dfdcdp dfdctp Adjei et al., J Clin Oncol 2; 8:1748 Shih et al., Cancer Res 1997; 57:1116 DNA Tonkinson et al., Cancer Res 1999; 59:3671 Tesei et al., Clin Cancer Res 22; 8:233

3 Cytotoxicity and pharmacologic interaction between gemcitabine and pemetrexed % Cells surviving respect to control % Cells surviving respect to control % Cells surviving respect to control dfdc MTA dfdc-mta MTA-dFdC Log [ Drug ] µg/ml Log [ Drug ] µg/ml Log [ Drug ] µg/ml dfdc (IC 5 )= 2.9 µg/ml MTA (IC 5 )= 1.58 µg/ml dfdc-mta (IC 5 )=.12 µg/ml MTA-dFdC (IC 5 )=.4 µg/ml dfdc (IC 5 )= µg/ml MTA (IC 5 )= 2.42 µg/ml dfdc-mta (IC 5 )=.75 µg/ml MTA-dFdC (IC 5 )=.9 µg/ml dfdc (IC 5 )= 4.75 µg/ml MTA (IC 5 )= 7.33 µg/ml dfdc-mta (IC 5 )=.3 µg/ml MTA-dFdC (IC 5 )=.2 µg/ml Combination Index (CI) Fraction affected Combination Index (CI) Fraction affected Combination Index (CI) Fraction affected dfdc MTA MTA dfdc

4 Cell cycle modulation by gemcitabine and pemetrexed 12 1 G1 phase Counts S phase G2 phase Counts Counts FL2-A FL2-A FL2-A Treatment G1 (%) a S (%) G2 (%) a Mean percent values of total number of cells examined in three independent experiments

5 Induction of apoptosis by gemcitabine, pemetrexed and their combination %Apoptotic cells pemetrexed gemcitabine %Apoptotic cells pemetrexed gemcitabine %Apoptotic cells pemetrexed gemcitabine Treatment Treatment Treatment Columns, mean values obtained from three indipendent experiments; bars, SE Statistically significant different from controls (P<.5)

6 Modulation of dck expression by pemetrexed IC 5 (ng/ml) a +dcyd +DEPC +THU C T treatment GAPDH cells a Mean values ± SE of at least three independent experiments. Gene expression (C T ) dck RRM1 RRM2 GAPDH dck expression (2 -ΔΔC T ) Log [cdna] MIA Paca-2

7 Enhancement of dck/rrm1 RRM2 expression ratio after pemetrexed treatment 5 1. IC 5 (µg/ml) R 2 = dck/rrm1xrrm2 expression ratio dck/rrm1xrrm2.

8 Conclusions and pemetrexed were cytotoxic against, and cells and the combination index demonstrated that the drug sequence showing the maximum degree of synergism was pemetrexed gemcitabine in all cell lines Flow cytometric studies demonstrated that pemetrexed and gemcitabine enhanced cellular population in S phase in all cell lines -pemetrexed combinations increased the occurence of apoptosis Quantitative RT-PCR analysis showed that pemetrexed significantly enhanced dck expression in all cell lines, while there was only a minor increase of RR expression These data provide evidence that the combination of gemcitabine and pemetrexed displays schedule-dependent synergistic cytotoxic activity against various pancreatic cancer cells, associated with favorable modulation of cell cycle, induction of apoptosis and inducible dck gene expression.