AbstractThe interleukin‐1 receptor‐related kinase 4 (IRAK4), downstream of myd88, plays an essential role in hyperactive TLR signalling seen in some B‐cell lymphomas. In particular, efficient IRAK4 inhibitors of activated B‐cell subtype of human diffuse large B‐Cell lymphoma (DLBCL) are being developed. However, the anticancer effect of IRAK‐4 inhibitors in veterinary medicine has not been elucidated. It is therefore explored in this study involving the GL‐1 and CL‐1 canine lymphoma cell lines in vitro. MyD88 expression was analysed using polymerase chain reaction. GL‐1 and CL‐1 cells were subjected to concentration‐ and time‐dependent treatment with an IRAK‐4 inhibitor and assessed for viability, TLR signalling association and apoptosis using a cell counting Kit‐8 assay, Western blotting and flow cytometry. The GL‐1 and CL‐1 cells exhibited enhanced MyD88 expression, however, canine peripheral blood mononuclear cells (cPBMCs) did not. The IRAK‐4 inhibitor reduced cell viability in a dose‐ and time‐dependent manner, significantly reduced the phosphorylation of molecules associated with TLR signalling at IC50 such as IRAK1, IRAK4, NF‐κB and STAT3, and induced apoptosis in GL‐1 and CL‐1 cells. The anticancer effect of the IRAK‐4 inhibitor on canine lymphoma cells is mediated by apoptosis via downregulation of TLR signalling.
