Design and Activity of Novel Oxadiazole Based Compounds That Target Poly(ADP-ribose) Polymerase.

Novel PARP inhibitors with selective mode-of-action have been approved for clinical use. Herein, oxadiazole based ligands that are predicted to target PARP-1 have been synthesized and screened for the loss of cell viability in mammary carcinoma cells, wherein seven compounds were observed to possess significant IC50 values in the range of 1.4 to 25 µM. Furthermore, compound 5u, inhibited the viability of MCF-7 cells with an IC50 value of 1.4µM, when compared to Olaparib (IC50 = 3.2 µM). Compound 5s also decreased cell viability in MCF-7 and MDA-MB-231 cells with IC50 values of 15.3 and 19.2 µM, respectively. Treatment of MCF-7 cells with compounds 5u and 5s produced PARP cleavage, H2AX phosphorylation and CASPASE-3 activation comparable to that observed with Olaparib. Compounds 5u and 5s also decreased foci-formation and 3D Matrigel growth of MCF-7 cells equivalent to or greater than that observed with Olaparib. Finally, in silico analysis demonstrated binding of compound 5s towardsthe catalytic site of PARP-1, indicating that these novel oxadiazoles synthesized herein may serve as exemplars for the development of new therapeutics in cancer.

Oxazine drug-seed induces paraptosis and apoptosis through reactive oxygen species/JNK pathway in human breast cancer cells.

Small molecule-driven JNK activation has been found to induce apoptosis and paraptosis in cancer cells. Herein pharmacological effects of synthetic oxazine (4aS, 7aS)-3-((4-(4­chloro-2-fluorophenyl)piperazin-1-yl)methyl)-4-phenyl-4, 4a, 5, 6, 7, 7a-hexahydrocyclopenta[e] [1,2]oxazine (FPPO; BSO-07) on JNK-driven apoptosis and paraptosis has been demonstrated in human breast cancer (BC) MDA-MB231 and MCF-7 cells respectively. BSO-07 imparted significant cytotoxicity in BC cells, induced activation of JNK, and increased intracellular reactive oxygen species (ROS) levels. It also enhanced the expression of apoptosis-associated proteins like PARP, Bax, and phosphorylated p53, while decreasing the levels of Bcl-2, Bcl-xL, and Survivin. Furthermore, the drug altered the expression of proteins linked to paraptosis, such as ATF4 and CHOP. Treatment with N-acetyl-cysteine (antioxidant) or SP600125 (JNK inhibitor) partly reversed the effects of BSO-07 on apoptosis and paraptosis. Advanced in silico bioinformatics, cheminformatics, density Fourier transform and molecular electrostatic potential analysis further demonstrated that BSO-07 induced apoptosis and paraptosis via the ROS/JNK pathway in human BC cells.

Novel 1,3,4-oxadiazole Targets STAT3 Signaling to Induce Antitumor Effect in Lung Cancer.

Lung cancer is the leading type of malignancy in terms of occurrence and mortality in the global context. STAT3 is an oncogenic transcription factor that is persistently activated in many types of human malignancies, including lung cancer. In the present report, new oxadiazole conjugated indazoles were synthesized and examined for their anticancer potential in a panel of cancer cell lines. Among the new compounds, 2-(3-(6-chloro-5-methylpyridin-3-yl)phenyl)-5-(1-methyl-1H-indazol-3-yl)-1,3,4-oxadiazole (CHK9) showed consistently good cytotoxicity towards lung cancer cells with IC50 values ranging between 4.8-5.1 µM. The proapoptotic effect of CHK9 was further demonstrated by Annexin-FITC staining and TUNEL assay. In addition, the effect of CHK9 on the activation of STAT3 in lung cancer cells was examined. CHK9 reduced the phosphorylation of STAT3Y705 in a dose-dependent manner. CHK9 had no effect on the activation and expression of JAK2 and STAT5. It also reduced the STAT3-dependent luciferase reporter gene expression. CHK9 increased the expression of proapoptotic (p53 and Bax) proteins and decreased the expression of the antiapoptotic (Bcl-2, Bcl-xL, BID, and ICAM-1) proteins. CHK9 displayed a significant reduction in the number of tumor nodules in the in vivo lung cancer model with suppression of STAT3 activation in tumor tissues. CHK9 did not show substantial toxicity in the normal murine model. Overall, CHK9 inhibits the growth of lung cancer cells and tumors by interfering with the STAT3 signaling pathway.