BAK1 and head and neck squamous cell carcinoma: In addition, increased expressions of pro-apoptotic proteins Bax, Bak, and Bid, decreased expressions of anti-apoptotic proteins Bcl-2 and Bcl-xL, and increased activation of PARP and caspases 3, 8, and 9 were observed in 7-Epitaxol-treated HNSCC cells (Figure 5).