Synergistic Interaction Of Pemetrexed With Gemcitabine Or Erlotinib In Different Combinations On Inducing The Apoptosis Of A549 Cell

Objective: Observe the effect of pemetrexed(P) with gemcitabine(G) or erlotinib(E) in different combinations, pemetrexed followed by gemcitabine(P→G), gemcitabine followed by pemetrexed (G→P), pemetrexed combined with erlotinib(P+E), pemetrexed followed by erlotinib (P→E) on inducing the apoptosis of A549 cell in vitro, in order to explore the better program of pemetrexed with gemcitabine or erlotinib.Methods: Human lung adenocarcinoma cell line A549 was chosen as target cells. MTT assay method was used to determine the proliferation inhibition of A549 cell which was respectively treated with P, G, E, P→G, G→P, P+E, P→E. The half inhibitory concentration (IC₅₀) and combination index(CI) were determined. Flow cytometry was used to detect cell cycle and apoptotic rate of A549 cell after different treatment. P-Akt expression in A549 cell was analyzed by western blot in each study group. Analysis the linear correlation between P-Akt expression and apoptotic rate of A549.Results: (1) P, G, E, P→G, G→P, P+E, P→E could inhibit A549 cell proliferation, while increasing drug concentration, the inhibition rate was increased (P <0.05 ). Synergistic effect was found in P→G, G→P, P+E, P→E groups, combination index(CI)<1, and synergy was more obvious in P→G group than G→P group, P+E group was more obvious than P→E group when inhibitory rate from 0.6 to 0.8(P<0.05). (2) Each group could affect cell cycle in A549 cell, P and G arrested cell cycle at S phase while erlotinib blocked cells at G₀/G₁ phase compared with the control group(P<0.05). P→G, G→P, P+E, P→E each group blocked more cells at S phase than the control and mono-drug treated groups(P<0.05). P→G group blocked more cells at S phase than G→P group(P<0.05), the difference between P+E and P→E groups was not significant(P>0.05). (3) All groups induced obvious apoptosis in A549 cell compared with the control(P<0.05), the four combined groups increased apoptotic rate than each mono-drug treated group(P<0.05), and the total is greater than separately. The apoptotic rate in P→G group is more than G→P group(P<0.05), the difference between P+E and P→E groups was not significant(P>0.05). (4) Compared with the control, P-Akt expression in A549 cell was decreased when treated with each group(P<0.05). P-Akt expression decreased significantly in the four combined group than the mono-drug treated groups(P<0.05), and the total is less than separately. P-Akt expression in P→G group is less than G→P group(P<0.05), the difference between P+E and P→E groups was not significant(P>0.05). Linear correlation analysis showed that in A549 cell, P-Akt expression and apoptotic rate was a negative correlation (P <0.05).Conclusion: The multitargeted antifolate pemetrexed combined with gemcitabine and erlotinib in different sequence P→G, G→P, P+E, P→E all can have synergistic effect on inducing the apoptosis of A549 cell, PI3k-Akt pathway maybe involved in this process. The synergy in P→G group is more obvious than G→P, the difference between P+E and P→E groups was not significant.