Overexpression of Bcl-2 observed in HBP tumours in the present study can block mitochondrial mediated apoptosis by preventing the release of apoptogenic factors such as cytochrome C, thereby inhibiting activation of caspases–9 and -3, as well as cleavage of PARP, a nuclear enzyme involved in DNA repair and maintenance of genomic integrity. This evidence concerns the gene CYCS and neoplasm.