Antigenic Potency of LY6E in Stimulating Dendritic Cells to Elicit Tumor-Specific Responses Against Human Colorectal and Gastric Cancer Cell Lines

Early-stage gastrointestinal (GI) carcinomas are amenable malignancies, however, due to late diagnosis or lack of proper medication, alternative treatment necessitates new approaches such as dendritic cell (DC) therapy. Our previous microarray study indicated Lymphocyte antigen-6 (LY6E) as a commonly overexpressed biomarker in three lethal GI cancers, colon, gastric, and pancreatic. Therefore, we examined the antigenic potency of LY6E in stimulating DCs to elicit tumor-specific responses against human colorectal cancer (CRC) and gastric cancer (GC) cell lines HT-29 and AGS, respectively. LY6E peptide-pulsed DCs stimulated lymphocytes up to 55.9% in comparison with mature DCs (48.3%). Also, flow cytometry analysis of lymphocyte proliferation illustrated that the populations CD4⁺ and CD8⁺ were increased after treating by peptide-pulsed DCs (62.9% and 48.7% respectively). Furthermore, the cytotoxicity assay demonstrated that the 40:1 ratio of stimulated lymphocytes on AGS and HT29 cell lines was 65.1% and 66.2%, respectively. The research exposed that LY6E loaded DCs had substantial impact stimulation, proliferation, and lineage differentiation of lymphocytes. Besides, co-cultured of primed lymphocytes with AGS and HT29 cell lines exhibited cytotoxic activity. These data suggest LY6E as a potential candidate in developing DC therapy against CRC and AGS.

     

Effect of mesenchymal stem cell-derived exosomes on the induction of mouse tolerogenic dendritic cells

Dendritic cells (DCs) orchestrate innate inflammatory responses and adaptive immunity through T-cell activation via direct cell–cell interactions and/or cytokine production. Tolerogenic DCs (tolDCs) help maintain immunological tolerance through the induction of T-cell unresponsiveness or apoptosis, and generation of regulatory T cells. Mesenchymal stromal cells (MSCs) are adult multipotent cells located within the stroma of bone marrow (BM), but they can be isolated from virtually all organs. Extracellular vesicles and exosomes are released from inflammatory cells and act as messengers enabling communication between cells. To investigate the effects of MSC-derived exosomes on the induction of mouse tolDCs, murine adipose-derived MSCs were isolated from C57BL/6 mice and exosomes isolated by ExoQuick-TC kits. BM-derived DCs (BMDCs) were prepared and cocultured with MSCs-derived exosomes (100 μg/ml) for 72 hr. Mature BMDCs were derived by adding lipopolysaccharide (LPS; 0.1μg/ml) at Day 8 for 24 hr. The study groups were divided into (a) immature DC (iDC, Ctrl), (b) iDC + exosome (Exo), (c) iDC + LPS (LPS), and (d) iDC + exosome + LPS (EXO + LPS). Expression of CD11c, CD83, CD86, CD40, and MHCII on DCs was analyzed at Day 9. DC proliferation was assessed by coculture with carboxyfluorescein succinimidyl ester-labeled BALB/C-derived splenocytes p. Interleukin-6 (IL-6), IL-10, and transforming growth factor-β (TGF-β) release were measured by enzyme-linked immunosorbent assay. MSC-derived exosomes decrease DC surface marker expression in cells treated with LPS, compared with control cells ( ≤ .05). MSC-derived exosomes decrease IL-6 release but augment IL-10 and TGF-β release (p ≤ .05). Lymphocyte proliferation was decreased (p ≤ .05) in the presence of DCs treated with MSC-derived exosomes. CMSC-derived exosomes suppress the maturation of BMDCs, suggesting that they may be important modulators of DC-induced immune responses.