Design, Synthesis, and Mechanistic Study of Novel Ciprofloxacin/Thiazole Chalcone Hybrids as Potential Anticancer Agents

A novel series of thiazole chalcone/ciprofloxacin hybrids were synthesized and screened for their anticancer activity against NCI-60 cancer cell lines, USA. Interestingly, compounds 4b and 4d exhibited potent antiproliferative activities, particularly against leukemia HL-60, RPMI-8226, and colon HCT-116 cells, with IC50 values of 0.3–3.70 µM. Importantly, compounds 4b and 4d exhibited enhanced selectivity for cancer cells relative to doxorubicin with IC50 values of 26.80, 41.20, and 19.80 µM, respectively. Mechanistic investigations revealed that compounds 4b and 4d inhibited topoisomerases (Topo) I/IIβ activity, being fourfold and twofold more effective than untreated controls, respectively. Furthermore, these compounds induced G1 phase cell cycle arrest and promoted apoptosis, which likely explain their potent anticancer properties. In depth, compound 4d increased the relative gene expression of pro-apoptotic Bax (5.58-fold) and caspase-3 (10.86-fold) as well as the initiator caspase-9 (4.2-fold), and reduced the relative gene expression of Bcl-2. Therefore, ciprofloxacin/thiazole chalcone derivatives, particularly 4b and 4d, may serve as promising candidates for the development of antitumor agents.