Furthermore, differences in PPL, TGM1, and KRT8 levels were observed in relation to smoking and alcohol use, distinguishing regular or occasional users from abstinent patients.<h4>Conclusions</h4>Our results suggest that impaired TGM1, PPL, and KRT8 signaling pathways might play a role in HNSCC, indicating their potential relevance for future diagnostic and therapeutic investigations. This evidence concerns the gene PPL and head and neck squamous cell carcinoma.