PCNA and hepatocellular carcinoma: Oestrogen has also been discovered to slow the progression of HCC by controlling tumour cell invasion, proliferation, and apoptosis by lowering the expression of matrix metallopeptidase 2 (MMP2), matrix metallopeptidase 9 (MMP9), proliferating cell nuclear antigen (PCNA), cyclin A, cyclin D1, and B-cell lymphoma-2 (Bcl-2) [10].