In the present study, it was demonstrated that combined treatment with Adv and a selective histone deacetylase 6 (HDAC6) inhibitor, ricolinostat (RCS), synergistically enhanced cell death induction in four out of five HNSCC cell lines with TP53 mutation (CAL27, SAS, HSC‑3, and OSC‑19), one HNSCC cell line with impaired TP53 function by HPV‑infection (UPCI‑SCC154), and TP53‑knockout human lung cancer cell line (A549 TP53‑KO), but not in TP53 wild‑type A549 cells.