CYCS and head and neck squamous cell carcinoma: Furthermore, mitochondria can release cytochrome c, inducing apoptosis; however, BCL2 and BCL2 like 1 (BCL2L1), that are antiapoptotic proteins, are overexpressed in HNSCC, which avoids cytochrome c release [84], inducing radioresistance (Figure 2) [84,85,86,87].