New 1,2,3-Triazole and Dipyridothiazine Hybrids-Synthesis, Analysis, Cytotoxicity and Molecular Docking

Epigenetic and stress-response pathways play central roles in cancer progression and represent attractive therapeutic targets. In this study, a series of dipyridothiazine-1,2,3-triazole hybrids bearing p-fluorophenyl and p-trifluoromethylphenyl substituents was synthesized via efficient dipolar cycloaddition reactions. Structural characterization was performed using ¹H, ¹³C, and ¹⁹F NMR spectroscopy and high-resolution mass spectrometry. Anticancer activity was evaluated using WST-1 and MTT assays against human cancer cell lines SNB-19 (glioblastoma), C32 (amelanotic melanoma), A549 (lung carcinoma), and MDA-MB-231 and MCF-7 (breast cancer), as well as normal HFF-1 fibroblasts and HaCaT keratinocytes, with doxorubicin and cisplatin as reference drugs. The hybrids TDT2b and TDT3b containing a p-trifluoromethylphenyl moiety showed the highest cytotoxicity and cancer cell selectivity. RT-qPCR analysis of H3, TP53, CDKN1A, BCL-2, and BAX expression for the lead compound TDT2b revealed modulation of chromatin organization, p53-dependent stress responses, apoptosis, and cell cycle regulation. Molecular docking studies with human histone deacetylase 6 (HDAC6) demonstrated favorable binding of TDT2b and TDT3b, supporting their role as potential epigenetic anticancer agents.