Extracellular Heat Shock Protein 27 Is Released by Plasma-Treated Ovarian Cancer Cells and Affects THP-1 Monocyte Activity

Heat shock protein 27 (Hsp27) is a cytoprotective molecule and is inducible via oxidative stress. Anti-cancer therapies, such as the recently investigated gas plasma, subject tumor cells to a plethora of reactive oxygen species (ROS). In ovarian tumor microenvironments (TME), immune cells such as monocytes and macrophages can be found in large numbers and are often associated with cancer progression. Therefore, we quantified extracellular Hsp27 of OVCAR-3 and SK-OV-3 cells after gas plasma exposure in vitro. We found Hsp27 to be significantly increased. Following this, we investigated the effects of Hsp27 on THP-1 monocytes. Live cell imaging of Hsp27-treated THP-1 cells showed decelerated cell numbers and a reduction in cell cluster sizes. In addition, reduced metabolic activity and proliferation were identified using flow cytometry. Mitochondrial ROS production decreased. Using multicolor flow cytometry, the expression profile of eight out of twelve investigated cell surface markers was significantly modulated in Hsp27-treated THP-1 cells. A significantly decreased release of IL18 accommodated this. Taken together, our results suggest an immunomodulatory effect of Hsp27 on THP-1 monocytes. These data call for further investigations on Hsp27’s impact on the interplay of ovarian cancer cells and monocytes/macrophages under oxidative stress conditions