Densely functionalized cinnolines: Controlled microwave-assisted facile one-pot multi-component synthesis and in vitro anticancer activity via apoptosis induction

Abstract There is an urging continuous need for novel anti-cancer agents due to persistent chemoresistance. Herein, newly synthesized cinnolines are evaluated fortheir possible anticancer activities and suggested mechanisms. In the current study, a simple and efficient synthesis of densely functionalized cinnolines has been developed that relied on multi-component reaction of ethyl 5-cyano-4-methyl-1-aryl-6-oxo-1,6-dihydropyridazine-3-carboxylates with aromatic aldehydes and nitromethane in dioxane/pipridineunder controlled microwave heating.Selected cinnolines (4a-c, e,h,j-n, q-v) were tested for possible anticancer activity using in vitro one dose assay at National Cancer institute, USA. Only cinnoline4b stood out as the most potent cinnoline derivative (mean GI%=26.33) with broad-spectrum antitumor activity against the most tested cancer cell lines from all subpanels. The target cinnoline4bemerged as the most active derivative againstboth leukemia RPMI-8226 and melanoma LOX IMVI cell lines(GI%=106.06 and 82.1) respectively, with IC50 values equal to 17.12±1.31 and 12.32±0.75 μg/mL, which are comparable to those of staurosporin; 24.97±1.47 and 8.45±0.42μg/mL, respectively. Cinnoline4b influenced cell cycle distribution causing pre-G1 apoptosis and cell growth arrest at G2/M phase. It alsoinduced apoptosis in both cell lines as manifested by significant increase in the percent of annexinV-FITC positive apoptotic cells in leukemia RPMI-8226 cells (from 1.09% to 12.47%) and melanoma LOX IMVI (from 1.32% to 19.05%).In addition, it showed lower expression levels of anti-apoptotic Bcl-2 protein, and higher expression levels of pro-apoptotic proteins; Bax, p53, cytochrome c, caspases3 and 9. Conclusion:induction of mitochondrial intrinsic pathway of apoptosis is a possible mechanism by which cinnoline4b may confer its anticancer activity.