The Curcumin Analogue PAC Induces Selective Apoptosis-Related Transcriptomic Reprogramming in Oral Squamous Carcinoma Cells

This study aimed to investigate the selective anticancer activity of the curcumin analog PAC (3,5-Bis-4-hydroxy-3-methoxybenzylidene)-N-methyl-4-piperidone). Normal gingival epithelial cells (GECs), cancerous gingival cells (Ca9-22) and tongue squamous carcinoma cells (CAL27) were exposed to increasing concentrations of PAC (0–10 µM) for 24 h. Cell viability and cytotoxicity were evaluated using MTT and LDH assays, while apoptosis and caspase activation were analyzed by Annexin V/PI staining and flow cytometry. Gene-expression profiling was performed using RT2 Profiler PCR arrays. PAC significantly inhibited Ca9-22 and CAL27 cell proliferation in a concentration-dependent manner, with an IC50 value of 5 µM, while exerting no noticeable cytotoxic effects on normal GEC. PAC treatment induced significant early and late apoptosis associated with increased caspase activity in both oral cancer cell lines. Transcriptomic analyses revealed extensive modulation of apoptosis-related genes. In Ca9-22 cells, PAC predominantly suppressed anti-apoptotic and survival-associated genes, including BCL2, BIRC3, BIRC5, XIAP, CFLAR, and NFKB1. In contrast, CAL27 cells exhibited a more pronounced pro-apoptotic transcriptional profile characterized by upregulation of TP53, APAF1, CASP1, BID, and TNF. Gene interaction network analyses further demonstrated that PAC targets highly interconnected apoptotic signaling pathways. Collectively, these findings demonstrate that PAC exerts potent selective anticancer activity against OSCC cells through modulation of intrinsic and extrinsic apoptotic pathways. These results further support the therapeutic potential of PAC as a promising multitarget candidate for oral cancer treatment.