To investigate this question, we examined the effects of monensin on the expression of the proliferative marker PCNA in 4T1-Luc2 cells, comparing them with those observed in murine HCC cells (Hepa-C1C7), human ovarian carcinoma cells (SKOV-3), and murine melanoma cells (B16), with or without 10% FBS during incubation. The gene discussed is PCNA; the disease is ovarian carcinoma.