7-Chloro-6-piperidin-1-yl-quinoline-5,8-dione (PT-262), a novel synthetic compound induces lung carcinoma cell death associated with inhibiting ERK and CDC2 phosphorylation via a p53-independent pathway

Background: The derivatives of 5,8-quinolinedione have been shown to exert Anticancer activities. A new synthetic compound 7-chloro-6-piperidin-1-yl-quinoline-5,8-dione (designed as PT-262) derived from 6,7-dichloroquinoline-5,8-dione on its Anticancer activity was investigated in this study.

Materials and methods: PT-262 was synthesized as the following: triethylamine (0.56 ml, 5.1 mmol) was added dropwise to a solution of 6,7-dichloroquinoline-5,8-dione (1.00 g, 4.4 mmol) and piperidine (0.50 ml, 5.1 mmol) in 150 ml of benzene with stirring at room temperature for 5 min, and the solvent was removed using rotary evaporator to give a dark brown solid. PT-262 was purified by flash chromatography using 50% ethyl acetate/hexanes to elute that displayed as brown solids. To examine the induction of Apoptosis following PT-262 treatment, the lung Cancer cells were subjected to apoptotic cell observation, Caspase activation, and mitochondrial functional assays. The protein levels of phosphorylated ERK and CDC2 after treatment with PT-262 were analyzed by Western blot.

Results: Treatment with 1-20 microM PT-262 for 24 h induced cytotoxicity via a concentration-dependent manner in human lung Cancer cells. PT-262 induced the loss of mitochondrial membrane potential and elevated the Caspase-3 activation and Apoptosis. Interestingly, the phosphorylation of ERK was inhibited by PT-262. The IC50 value of ERK phosphorylation inhibition was approximate around 5 microM. Treatment with a specific MEK1/2 (the upstream of ERK) inhibitor, PD98059, increased the PT-262-induced cytotoxicity in lung Cancer cells. Moreover, PT-262 did not alter the protein expression of tumor suppressor p53. PT-262 elicited the cytotoxicity and accumulated the G2/M fractions in both the p53-wild type and p53-null lung Cancer cells. The mitosis-regulated protein levels of cyclin B1 and phospho-CDC2 at Thr14, Tyr15, and Thr161 were repressed by PT-262 in these cells.

Conclusion: PT-262 suppresses the phosphorylation of ERK and CDC2 associated with proliferation inhibition via a p53-independent pathway in human lung Cancer cells.