Novel 2-substituted-quinoxaline analogs with potential antiproliferative activity against breast cancer: insights into cell cycle arrest, topoisomerase II, and EGFR activity.

Breast cancer is a global health concern, with increasing disease burden and disparities in access to healthcare. Late diagnosis and limited treatment options in underserved areas contribute to poor outcomes. In response to this challenge, we developed a novel family of 2-substituted-quinoxaline analogues, combining coumarin and quinoxaline scaffolds known for their anticancer properties. Through a versatile synthetic approach, we designed, synthesized, and characterized a set of 2-substituted quinoxaline derivatives. The antiproliferative activity of the synthesized compounds was assessed toward the MCF-7 breast cancer cells. Our investigations showed that the synthesized compounds exhibit considerable antiproliferative activity toward MCF-7 cells. Notably, compound 3b, among examined compounds, displayed a superior inhibitory effect (IC = 1.85 ± 0.11 μM) toward the growth of MCF-7 cells compared to the conventional anticancer drug staurosporine (IC = 6.77 ± 0.41 μM) and showed minimal impact on normal cells (MCF-10A cell lines, IC = 33.7 ± 2.04 μM). Mechanistic studies revealed that compound 3b induced cell cycle arrest at the G1 transition and triggered apoptosis in MCF-7 cells, as evidenced by increasing the percentage of cells arrested in the G2/M and pre-G1 phases utilizing flow cytometric analysis and Annexin V-FITC/PI analysis. Moreover, compound 3b was found to substantially suppress topoisomerase enzyme activity in MCF-7 cells. Molecular modeling studies further supported the potential of compound 3b as a therapeutic candidate by demonstrating significant binding affinity to the active sites of both topoisomerase II and EGFR proteins. Taken together, the presented 2-substituted-quinoxaline analogues, especially compound 3b, show promise as potential candidates for the development of effective anti-breast cancer drugs.