Abstract
Background Gastrosphere, an enriched cellular population with stem-like properties believed to be responsible for an escape from immune-mediated destruction. Th17 and Treg cells play a major role in gastric cancer; however, their interaction with gastrospheres remained elusive. Method Peripheral blood mononuclear cells were isolated from healthy donors and were cultured with conditioned media of MKN-45 (parental) cells as well as gastrospheres' conditioned media in the context of mixed lymphocyte reaction and in the presence of anti-CD3/CD28 beads. The proliferation was evaluated using CFSE staining; the percentages of CD4+CD25+FoxP3+ Treg and CD4+IL-17+ Th17 cells and IFN-γ+cells and the production of IL-17, TGF-β, and IL-10 were assessed by flow cytometry and ELISA, respectively. Finally, the cytotoxic potential of induced immune cells was measured by examining the secretion of lactate dehydrogenase from target cells. Results The results revealed a decreased expansion of PBMCs postexposure to gastrospheres' conditioned medium which was concomitant with an increased percentage of Th17 and an enhanced Th17 to Treg ratio. The conditioned media of gastrospheres enhanced the secretion of IL-10 and IL-17 and decreased TGF-β. Interestingly, immune cells induced by gastrospheres showed significant cytotoxicity in terms of producing IFN-γ and death induction in target cells. All these changes were related to the upregulation of IL-6, IL-10, and IL-22 in gastrospheres compared to parental cells. Conclusion Our study showed that the condition media of gastrospheres can potentially induce Th17 with increasing in their cytotoxic effect. Based on our knowledge, the present study is the first study that emphasizes the role of gastrospheres in the induction of antitumor Th17 cells. However, it should be confirmed with complementary studies in vivo.
Highlights
Gastric cancer stem cells (CSCs) are considered as the key player for the initiation and development of tumors which give rise to nontumorigenic and invasive tumor cells
We investigated the frequency and the balance of Th17 and Treg cells in peripheral blood mononuclear cells postexposure to conditioned media derived from human gastric cancer cells and their enriched gastrospheres as a model for gastric CSCs
To further understand that how gastric CSCs could affect Th17/Treg balance, we evaluated the expression of IL-17, IL-6, IL-8, IL-10, IL-22, IL-23, TNF-α, TGF-β, IFN-γ, and STAT3 that believed to be important in changing the Th17/Treg balance using qRT-PCR in parental and gastrospheres
Summary
Gastric cancer stem cells (CSCs) are considered as the key player for the initiation and development of tumors which give rise to nontumorigenic and invasive tumor cells They are responsible for metastasis and immune escape [1] and can be isolated and enriched by different mechanisms including stem cell surface markers, intracellular enzyme activity, the concentration of reactive oxygen species, the identification of side population cells, resistance to cytotoxic compounds or hypoxia, invasiveness/adhesion, immunoselection, and sphere formation in nonadherent conditions [2]. Immune cells induced by gastrospheres showed significant cytotoxicity in terms of producing IFN-γ and death induction in target cells. All these changes were related to the upregulation of IL-6, IL-10, and IL-22 in gastrospheres compared to parental cells. It should be confirmed with complementary studies in vivo
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