PLK1 and head and neck squamous cell carcinoma: By inhibiting apoptosis, PLK1 over-expression was associated with poor survival in patients with HNSCC, being an independent prognostic factor.43 Its targeting with a multi-kinase inhibitor led to encouraging anti-tumor activity in patients with SCC.44 These data suggest that PLK1 might be a potential therapeutic target for HNSCC patients undergoing radiotherapy.