PCNA and cancer: Furthermore, we evaluated the impact of selenium alone and in combination with Gemcitabine in BxPC-3 cells on relevant biological markers such as cleaved-poly ADP ribose polymerase (PARP) for apoptosis and proliferating cell nuclear antigen (PCNA) for proliferation as well as equilibrative nucleoside transporter 1 (ENT1) protein for examining the facilitation of Gemcitabine uptake by the cancer cells.