Mesenchymal stem cell-derived exosomes do not promote the proliferation of cancer cells

Nowadays, the use of Mesenchymal stem cells (MSCs) in clinical therapies have an increased acceleration, while it constitutes two sides of yin-yang with its ameliorating effects in regenerative medicine and promoting effects in carcinogenesis. It has been shown that the treatment activities of MSCs are mediated by paracrine factors secreted. These paracrine factors are transmitting via exosomes secreted from MSCs. With the understanding of this mechanism, cell-free therapies have begun to create a new path in MSC based therapies. At this point, two sides of the yin-yang have once again become controversial. In addition, there are conflicting study results in the literature. Due to this contradiction, we have designed this study to demonstrate the role of MSCs in the carcinogenesis process and we investigated the proliferation effect of MSC-derived exosomes on cancer cell lines. Two parallel experimental setups were established, as an experimental group, the four-different epithelial cancer cell lines and Wharton's Jelly (WJ)-MSC derived exosomes were directly co-cultured with in 6 different concentrations and simultaneously in the control group cells were cultured respectively. PKH-26 labelling was performed for detection of exosome locations in co-cultures. Each group were evaluated by WST-1 and xCelligence assays for proliferation and confirmed with PCNA staining. The results were analysed with paired t-test and Newman-Keuls comparison. The relative comparison demonstrated a significant increase in the rate of proliferation only in exosome co-cultures with WJ-MSCs and it was supported by PCNA staining. Cancer cell lines in co-cultures have not shown any significant increase neither in proliferation assays nor in PCNA staining. MSCs regulate their secretions according to the microenvironment, they have more dominant regenerative feature rather than triggering cancer proliferation.