Introduction: Peripheral blood mononuclear cells (PBMCs) sensitized with mesenchymal stem cells (MSCs) secretome and/or colony stimulating factor-2 (CSF-2) as an immunotherapy candidate may escalate osteosarcoma stem cells (OS-SCs) apoptosis. This study aimed to investigate the escalation of osteosarcoma stem cells' apoptosis after the co-cultivation with PBMCs sensitized by MSCs secretome with/or CSF-2 and it was completed by analyzing the level of serum tumor necrosis factor-related apoptosis-inducing ligand (sTRAIL) and tumor necrosis factor-α (TNF-α) level, annexin V binding, caspase-3 and caspase-8 expression in vitro. Methods: OS-SCs were derived from a single human osteosarcoma sample with its high grade and osteoblastic essential clinical characteristics obtained from a biopsy before the chemotherapy treatment. They were then isolated and cultured confirmed by the cluster of differentiation-133 (FITC) by applying immunofluorescence analysis with fluorescein isothiocyanate (FITC) labeled. MSCs secretome was obtained with cells extracted from the bone marrow of a healthy patient. Furthermore, enzyme linked immunosorbent assay (ELISA) was utilized to analyze sTRAIL and TNF-α level in each group. The expression of caspase-3, caspase-8, and annexin V assay in each group was examined by applying the immunofluorescence labeled with FITC. The comparison analysis between treatment groups and the control group was performed by utilizing the analysis of variance (ANOVA) and continued with Tukey Honest Significant Difference (HSD) (p<0.05). Results: There was a significant difference in the upregulation of sTRAIL and TNF-α level indicated by the increased annexin V, caspase-3, and caspase-8 expression binding between groups (p<0.05). Conclusion:MSCs Secretome and CSF-2 could significantly increase the activity of PBMCs through the improvement of sTRAIL and TNF-α levels which could lead to the escalation of OS-SCs apoptosis through an enhanced expression of caspase 3, caspase 8 and annexin V binding in vitro.

Context: Microvesicle is a cell micro molecule that may play a role in the process of osteosarcoma stem cell apoptosis. Aims: To investigate the activity of peripheral blood mononuclear cells (PBMCs) through the secretion of interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-10 (IL-10), C-X-C Motif Chemokine Ligand 13 (CXCL13) and tissue inhibitor of metalloproteinases-3 (TIMP-3) on co-cultivation of peripheral blood mononuclear cells (PBMCs) sensitized by mesenchymal stem cell secretome (MSCS) co-cultivated with osteosarcoma stem cells (OS-SCs). Methods: This study was true experimental with a post-test only control group design. This was in vitro study PBMSCs sensitized by MSCS as then samples were divided into 4 treatment groups, respectively: Zero-day treatment (P0) PBMCs were co-cultivated with OS-SCs for 0 hours; First treatment (P1) PBMCs were co-cultivated with OS-SCs for 1 hour; Second treatment (P2) PBMCs were co-cultivated with OS-SCs for 2 days; Third treatment (P3) PBMCs were co-cultivated with OS-SCs for 4 days. The examination method used in this study was flow cytometry and indirect enzyme-linked immunosorbent assay (ELISA). The data were statistically analyzed with analysis of variance (ANOVA) with a p≤0.05 considered a significant difference. Results: There was a tendency for a significant increase in extravesicular secretion in the secretion of IL-2, IL-6, IL-10, CXCL13, TIMP3, in the microvesicle PBMCs when sensitized by MSCs secretome co-cultivated with OS-SCs environment co-cultivated after the fourth day with significantly different between groups (p≤0.05). Conclusions: PBMSCs’ microvesicle such as IL-2, IL-6, IL-10, CXCL13, TIMP3 was significantly sensitized by MSCS and co-cultivated with OS-SCs after the fourth day of in vitro.