| Popis: |
Objectives. Toll-like receptor 3 (TLR3) is a member of Toll-like receptor family that belongs to pattern recognition receptors which recognize motifs derived from pathogens. It is located on the endosome and is stimulated by viral dsRNA or its synthetic analogs poly(I:C) and poly(A:U). It can also be stimulated by endogenous ligands, called damage associated molecular patterns (DAMPs). TLR3 participates in innate immunity but also plays a role in tumor cells. TLR3 stimulation induces apoptosis but may also stimulate tumor progression through increased cell proliferation, migration and metabolic re-programming. Here, we have tried to determine whether TLR3 plays a role in cancer stem cells (CSC). Methods. Pharyngeal cancer cell line Detroit 562 was used as the experimental model. The cells were treated with poly(I:C) or poly(A:U). Cells were grown in normal conditions to obtain adherent cells cultures or specific conditions to enrich cancer stem cells (CSC) (tumorospheres). Proteins were isolated from both, adherent cells and tumorospheres, and detected by western blot. Results. We observed a significantly higher expression of endogenous ligands in tumorospheres and adherent cells treated with synthetic analogues of dsRNA compared with untreated controls. Among the endogenous ligands observed, S100A9 had the highest upregulation after both treatments with poly(I:C) and poly(A:U) in CSC and in adherent cells compared to control. S100A9 is overexpressed in many cancers, associated with poor prognosis, and may promote immune evasion. HMGB1 was induced through poly(A:U) treatment in CSC and with poly(I:C) in adherent cells, whereas RAGE as receptor for HMGB1 had equally robustly expressed bands for both treatments in CSC and adherent cells compared with the control. HSP70 can suppress apoptosis, interfere with tumor immunity, promote angiogenesis and support metastasis. In our experiments, it has shown highest upregulation with poly(I:C) treatment in CSC compared to the control. TLR4 was not significantly changed in all of the samples. Conclusion. We have determined that the TLR3 stimulation induces the expression of DAMPs. This demonstrates that no external signal is necessary, but only endogenous ligands, to induce TLR3 and cancer progression. Moreover, we have shown that endogenous ligands released from cancer stem cells can also contribute to head and neck cancer progression. |
