RESUMEN
BACKGROUND/AIM: Activation-induced cytidine deaminase (AID) is a DNA modifying enzyme which has an essential function in promoting antibody diversification. Its overexpression is strongly associated with B-cell derived malignancies including Burkitt lymphoma, where AID is required for the characteristic c-MYC/IGH translocation. This study aimed at defining AID's oncopathogenic role which is still poorly understood. MATERIALS AND METHODS: We created over-expressing and knock-down cell culture models of AID, and used cellular assays to provide insight into its contribution to lymphomagenesis. RESULTS: We showed that AID expression is highly specific to, and abundantly expressed in B-cell-derived cancers and that ectopic overexpression of AID leads to rapid cell death. Using a knock-down model, we revealed that AID expression significantly impacts genomic stability, proliferation, migration and drug resistance. CONCLUSION: AID is an important driver of lymphoma, impacting multiple cellular events, and is potentially a strong candidate for targeted therapy in lymphoma.
Asunto(s)
Citidina Desaminasa/metabolismo , Resistencia a Antineoplásicos , Linfoma de Células B/metabolismo , Animales , Antineoplásicos/farmacología , Linfoma de Burkitt/tratamiento farmacológico , Linfoma de Burkitt/genética , Linfoma de Burkitt/metabolismo , Linfoma de Burkitt/patología , Línea Celular Tumoral , Movimiento Celular/genética , Proliferación Celular , Citidina Desaminasa/genética , Daño del ADN , Doxorrubicina/farmacología , Expresión Génica Ectópica , Activación Enzimática , Expresión Génica , Técnicas de Silenciamiento del Gen , Humanos , Linfoma de Células B/tratamiento farmacológico , Linfoma de Células B/genética , Linfoma de Células B/patologíaRESUMEN
Although insulin-like growth factor 1 (IGF-1) signaling promotes tumor growth and cancer progression, therapies that target the IGF-1 receptor (IGF-1R) have shown poor clinical efficacy. To address IGF-1R activity in cancer cells and how it differs from that of the closely related insulin receptor (IR), we focused on two tyrosines in the IGF-1R C-terminal tail that are not present in the IR and are essential for IGF-1-mediated cancer cell survival, migration, and tumorigenic growth. We found that Tyr1250 and Tyr1251 (Tyr1250/1251) were autophosphorylated in a cell adhesion-dependent manner. To investigate the consequences of this phosphorylation, we generated phosphomimetic Y1250E/Y1251E (EE) and nonphosphorylatable Y1250F/Y1251F (FF) mutant forms of IGF-1R. Although fully competent in kinase activity and signaling, the EE mutant was more rapidly internalized and degraded than either the wild-type or FF receptor. IGF-1 promoted the accumulation of wild-type and EE IGF-1R within the Golgi apparatus, whereas the FF mutant remained at the plasma membrane. Golgi-associated IGF-1R signaling was a feature of migratory cancer cells, and Golgi disruption impaired IGF-1-induced signaling and cell migration. Upon the formation of new cell adhesions, IGF-1R transiently relocalized to the plasma membrane from the Golgi. Thus, phosphorylation at Tyr1250/1251 promoted IGF-1R translocation to and signaling from the Golgi to support an aggressive cancer phenotype. This process distinguishes IGF-1R from IR signaling and could contribute to the poor clinical efficacy of antibodies that target IGF-1R on the cell surface.