The inhibition of the pemetrexed-activated MAPK pathway via sorafenib is involved in the synergistic mechanism of sorafenib subsequent potentiation of pemetrexed cytotoxicity in EGFR TKI-resistant cell lines.
BACKGROUND
The effect of combined administration of the multi-targeted receptor tyrosine kinase (RTK) inhibitor (Sorafenib) and chemotherapy (Pemetrexed) is still unknown. The cytotoxicity, the optimal combined modality, and the mechanisms underlying the cytotoxic synergism between sorafenib and pemetrexed for EGFR TKI-resistant NSCLC cell lines were then investigated.


METHODS
A549 (EGFR wild-type and KRAS mutation) and H1975 (EGFR mutation and KRAS wild-type) cell lines were treated with pemetrexed and/or sorafenib in vitro. IC50 values, CI (combination index), cell cycle distribution, and phospho-p44/42MAPK were assessed for both cell lines.


RESULTS
The cytotoxic interactions between sorafenib and pemetrexed were dose dependent in EGFR TKI-resistant NSCLC cell lines. The administration of the pemetrexed-sorafenib sequence had a synergistic effect and an advantage over the sorafenib-pemetrexed sequence and concomitant administration in both cell lines. Cell cycle analysis showed that sorafenib arrested cells mainly in G1 phase while pemetrexed arrested cell mainly in S phase. Exposure to sorafenib first induced G1 arrest and subsequently prevented the cytotoxicity of S phase specific drug pemetrexed. Exposure to pemetrexed resulted in an increased phospho-p44/42MAPK level which was inhibited by subsequent exposure to sorafenib. U0126, an inhibitor of the MAPK kinase, also enhanced cytotoxicity of pemetrexed in a sequence dependent manner in TKI-resistant cell lines. Likewise, the pemetrexed-activated MAPK signaling pathway was subsequently inhibited by U0126.


CONCLUSIONS
The sequence of pemetrexed followed by sorafenib had a synergistic effect and an advantage over other sequences in EGFR TKI-resistant NSCLC cell lines. The synergistic mechanism was due to sorafenib subsequently inhibiting the pemetrexed-activated MAPK signaling pathway. The results may provide molecular evidence to support clinical treatment strategies for patients with EGFR TKI-resistant lung cancer.
Department of Respiratory Medicine, General Hospital of the Chinese People's Liberation Army, Beijing 100853, PR China.
Yanwen
Y
Jiang
Chunsun
C
Li
Yingmin
Y
Ma
Jie
J
Chen
Yanqin
Y
Li
Liangan
L
Chen
D000970:Antineoplastic Agents / Q000494:pharmacology*; D001557:Benzenesulfonates / Q000494:pharmacology*; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000502:physiology; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D005971:Glutamates / Q000494:pharmacology*; D006147:Guanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D009536:Niacinamide / Q000031:analogs & derivatives; D000068437:Pemetrexed; D010671:Phenylurea Compounds; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology*; D000077157:Sorafenib
D000970:Antineoplastic Agents; D001557:Benzenesulfonates; D004791:Enzyme Inhibitors; D005971:Glutamates; D010671:Phenylurea Compounds; D011725:Pyridines; D000068437:Pemetrexed; D009536:Niacinamide; D006147:Guanine; D000077157:Sorafenib; C512478:EGFR protein, human; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases