I am working on MCF10a cells. I started my culture by thawing a fresh vial of cells purchase in the month of February, 2024. I am culturing them in DMEM/F12 media supplemented with horse serum, EGF, insulin, hydrocortisone, cholera toxin and PenStrep. I am now at the 6th passage but the cells are still taking more time than anticipated to be 70% - 80% confluent. Does anybody work with these cells? They are epithelial cells, so, is it normal for these cells to have a slow division rate?