biostudies-literatureUnknown27(3)Oka KInducible costimulator (ICOS) is a costimulatory immune checkpoint receptor expressed on activated T-cells, while the ICOS ligand (ICOSL) is expressed on antigen-presenting cells. The ICOS-ICOSL axis promotes the survival of memory and effector T-cells and induces several immune responses. In addition, the ICOS-ICOSL interaction induces cell proliferation, cell survival, and cytokine production. The roles of ICOS and ICOSL in cutaneous T-cell lymphoma (CTCL) are unclear. In this study, we examined the roles of ICOS and ICOSL in CTCL. The tumor cells co-expressed ICOS and ICOSL, and the upregulated expression of ICOS and ICOSL reflected disease severity. Anti-ICOS and anti-ICOSL neutralizing antibodies inhibited both the in vitro and in vivo proliferation of CTCL cell lines. The anti-ICOSL International journal of molecular sciences1408https://www.ebi.ac.uk/biostudies/studies/S-EPMC12897944biostudies-literatureInducible Costimulator and Its Ligand Promote Proliferation and Migration of Tumor Cells in Cutaneous T-Cell Lymphoma.PMC12897944Suga HTakahashi-Shishido NMizuno YMiyagaki THisamoto TOmori IKamijo HOka TShibata SSato SMiyagawa TMorita HOka KSugaya MBoki HfalseInducible Costimulator and Its Ligand Promote Proliferation and Migration of Tumor Cells in Cutaneous T-Cell Lymphoma.Inducible costimulator (ICOS) is a costimulatory immune checkpoint receptor expressed on activated T-cells, while the ICOS ligand (ICOSL) is expressed on antigen-presenting cells. The ICOS-ICOSL axis promotes the survival of memory and effector T-cells and induces several immune responses. In addition, the ICOS-ICOSL interaction induces cell proliferation, cell survival, and cytokine production. The roles of ICOS and ICOSL in cutaneous T-cell lymphoma (CTCL) are unclear. In this study, we examined the roles of ICOS and ICOSL in CTCL. The tumor cells co-expressed ICOS and ICOSL, and the upregulated expression of ICOS and ICOSL reflected disease severity. Anti-ICOS and anti-ICOSL neutralizing antibodies inhibited both the in vitro and in vivo proliferation of CTCL cell lines. The anti-ICOSL 2026-01-01T00:00:00Z2026 Jan2026-07-09T10:25:14.501Z2026-07-09T10:19:57.952ZS-EPMC128979444168382910.3390/ijms27031408