Introduction: Polycystic ovarian syndrome (PCOS) is a proinflammatory state that underpins the development of metabolic aberration and ovarian dysfunction in the disorder. Chronic inflammation and increased levels of androgens in these patients and their impact on the immune system, may be able to disrupt antitumor activity and thus increase the risk of developing malignancies including ovarian cancer. Materials and Methods: Peripheral blood mononuclear cells of 50 patients with PCOS and healthy controls were purified by Ficoll density gradient centrifugation. We then measured cell proliferation and concentrations of cytokines TNF-α at different time intervals (48 and 72 hours) after co-culture of ovarian (SKOV3, A2780) and breast (MCF-7, MDA-468) tumor cell lines with PBMC in indirect contact of transwell system. Results: Proliferative response of executive cells during stimulation with tumor cell lines after 48 hours was not statistically significant between patients and healthy controls. Between the 2 groups,  proliferation rates at the end of 72h were significantly higher than after 48h (P<0.01). The production of TNF-α in co-culture of A2780 cell lines significantly increased in the patient group in time compared to the controls (P<0.05). Conclusion: Our findings confirmed that, compared to healthy individuals low levels of chronic inflammation in patients with PCOS exhibit increased proliferative response of immune cells and TNF-α levels. An increased risk of cancers in patients with PCOS however requires investigation of other aspects of anti-tumor responses in vitro, with larger sample sizes.