Limited studies to date have shown that high ABCB3 mRNA/protein expression was associated with chemoresistance[7,19] but better clinical outcome in ovarian cancer[20,21]; (4) Several studies have found ABCC2 overexpression in ovarian cancer patients with poor clinical outcome and chemotherapy response[22,23], yet contrary studies exist[24,25]; and (5) ABCG2 is known as a stem cell marker that is associated with chemoresistance[26,27] but has been poorly studied in ovarian cancer. This evidence concerns the gene ABCG2 and ovarian cancer.