A model of Oct4A-mediated ovarian cancer evolution and progression in the ascites microenvironment. During the course of ovarian cancer progression a shedding of tumor cells into the peritoneum occurs. Here tumor cells survive as cellular aggregates/spheroids where CSC-enriched core cells of the spheroids serve as a niche for regenerating cells. During chemotherapy treatment the bulk of the differentiated tumor cells on the periphery of the spheroids are eradicated leaving behind CSC-enriched core tumor cells. These cells facilitate the self-renewal of chemotherapy surviving residual cells resulting in tumor recurrence.