“…Co-carcinogen studies with chemical carcinogens or with oestrogen in these mice indicated that whereas E7 promotes immortalization, E6 promotes progression into full malignancy (Song et al, 2000;Riley et al, 2003;Brake and Lambert, 2005). In the reproductive tract, E6 has significantly weaker activity than E7 (Riley et al, 2003); however, after prolonged oestrogen treatment, cervical tumours did result, although this activity did not seem to require PDZ-binding capacity (Shai et al, 2007). Most importantly, however, the ability of E6 to cooperate with E7 in increasing tumour size and frequency, both in the cervix and at other tumour sites, was dependent upon the ability of E6 to bind to its PDZ domain-containing substrates (Nguyen et al, 2003;Shai et al, 2007Shai et al, , 2008.…”