Inactivation of FOXO1 induces T follicular cell polarization and involves angioimmunoblastic T cell lymphoma

Objective:Angioimmunoblastic T cell lymphoma(AITL)is an aggressive form of non-Hodgkin lymphoma derived from mature T cells.However,the underlying pathogenesis of AITL remains unresolved.We aimed to explore the role of FOXO1-mediated signaling in the tumorigenesis and progression of AITL.Methods:FOXO1 expression was assessed using immunohistochemistry on a total of 46 AITL tissue samples.Retroviruses encoding FOXO1 shRNA were used to knockdown FOXO1 expression in CD4^+T cells.Flow cytometric assays analyzed the proliferation and survival of FOXO1 knockdown CD4^+T cells.Furthermore,we performed adoptive T-cell transfer experiments to identify whether inactivation of FOXO1 induced neoplastic follicular-helper T(Tfh)cell polarization and function.Results:Patients with low FOXO1 protein levels were prone to have an advanced tumor stage(P=0.049),higher ECOG ps(P=0.024),the presence of bone marrow invasion(P=0.000),and higher IPI(P=0.035).Additionally,the survival rates of patients in the FOXO1 high-expression group were significantly better than those in the FOXO1 low-expression group(χ^2=5.346,P=0.021).We also observed that inactivation of FOXO1 increased CD4^+T cell proliferation and altered the survival and cell-cycle progression of CD4^+T cells.Finally,we confirmed that inactivation of FOXO1 induces Tfh cell programing and function.Conclusions:Inactivation of FOXO1 in AITL plays a key role in the tumorigenesis and progression of AITL.We propose that FOXO1 expression could be a useful prognostic marker in AITL patients to predict poor survival,and to design appropriate therapeutic strategies.