PGR and breast cancer: Johal et al. [157] extended these observations: starting from the evidence that HMTV-associated BC was correlated with the expression of a number of carcinogenic cellular factors [137,138], they investigated a putative association between hepatic diseases showing MMTV-like sequences and expression of PgR, estrogen receptor-α (ER-α), and nuclear accumulation of the p53 protein, already known to be implicated in hepatic carcinogenesis [160,161].