Kowsar Jentashapir J Cell Mol Biol 2717-2724 11 3 2020 11 14 10.5812/jjcmb.110320 Hamed Shoghi Department of Medical Physics, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Niloofar Neisi Alimentary Tract Research Center, Imam khomeini Hospital Clinical Research Development Unit, Infectious and Tropical Diseases Research Center, Department of Virology, the School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Ghasem Saki Cellular and Molecular Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Mohamad Javad Tahmasebi Birgani Department of Medical Physics, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Amir Danyaei Department of Medical Physics, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Research Article 2020 10 22 2020 10 14 2020 11 14 2020 09 30 Background : While radiotherapy is the important modality in the treatment of breast cancer cells, radioresistance of some tumor cell lines such as MDA-MB-231 is still a limitation that must be considered. Objectives : The present study was done to examine the effect of the conditioned medium of the human umbilical cord Wharton's jelly stem cells (hWJSCs + CM) on the radiosensitivity of MDA-MB-231 cells in combination with megavoltage-radiations. Methods : Groups are Control, CM, GY, and GY + CM. In irradiation groups, breast cancer cells were exposured with 4, 6, and 8 Gy radiation. Each group includes different doses of the conditioned medium of hWJSCs (25%, 50%, and 75%). Results : The MTT assay showed that the proliferative activity of Gy + CM groups at all doses of condition medium decreased significantly compared with the control, rather than Gy groups. Trypan blue viability test showed that the survival rate of MDA-MB-231 cells significantly reduced in the CM and 8 Gy + CM groups compared with the control group, rather than Gy groups. MDA-MB-231 cells lost their normal spindle shape and became thinner and longer after 48h of treatment and the number of cells sharply reduced in Gy + CM groups compared with the control group, rather than Gy groups. These changes were accompanied by inducing significant up-regulation of Interleukin-6 (IL-6) in the 4 Gy + CM and 8 Gy + CM groups compared with the control group, rather than Gy groups and as a consequence, a decrease in the amount of transmembrane tumor necrosis factor-α (tmTNF-α) as a pro-inflammatory cytokine in the Gy + CM groups compared with the control group, rather than Gy groups. Also, we indicated that the radiosensitivity of breast cancer cells was probably enhanced by an increase in different doses of the conditioned medium of stem cells. Conclusions : Treatment of the MDA-MB-231 cells with hWJSCs + CM plus radiotherapy inhibited the growth and proliferation of cancer cells and this method is a novel strategy for breast cancer therapy by overcoming radioresistance. https://sites.kowsarpub.com/jjcmb/articles/110320.html https://jjcmb.kowsarpub.com/cdn/dl/b07edefc-56a2-11eb-863c-63f1d6d118fa Breast Cancer MDA-MB-231 Human Wharton's Jelly of the Umbilical Cord Stem Cells (hWJSCs + CM) Radioresistance IL-6 TNF-α