RESUMEN
BACKGROUND: ZNF384-fusion (Z-fusion) genes were recently identified in B-cell acute lymphoblastic leukemia (B-ALL) and are frequent in Japanese adult patients. The frequency is about 20% in those with Philadelphia chromosome-negative B-ALL. ZNF384 is a transcription factor and Z-fusion proteins have increased transcriptional activity; however, the detailed mechanisms of leukemogenesis of Z-fusion proteins have yet to be clarified. METHODS: We established three transfectants of cell lines expressing different types of Z-fusion proteins, and analyzed their gene expression profile (GEP) by RNA-seq. We also analyzed the GEP of clinical ALL samples using our previous RNA-seq data of 323 Japanese ALL patients. We selected upregulated genes in both Z-fusion gene-expressing transfectants and Z-fusion gene-positive ALL samples, and investigated the binding of Z-fusion proteins to regulatory regions of the candidate genes by ChIP-qPCR. RESULTS: We selected six commonly upregulated genes. After the investigation by ChIP-qPCR, we finally identified CREB5 and RGS1 as direct and common target genes. RGS1 is an inhibitor of CXCL12-CXCR4 signaling that is required for the homing of hematopoietic progenitor cells to the bone marrow microenvironment and development of B cells. Consistent with this, Z-fusion gene transfectants showed impaired migration toward CXCL12. CONCLUSIONS: We identified CREB5 and RGS1 as direct and common transcriptional targets of Z-fusion proteins. The present results provide novel insight into the aberrant transcriptional regulation by Z-fusion proteins.
Asunto(s)
Proteína de Unión a Elemento de Respuesta al AMP Cíclico , Proteínas de Fusión Oncogénica , Proteínas RGS , Humanos , Línea Celular Tumoral , Quimiocina CXCL12/genética , Quimiocina CXCL12/metabolismo , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/genética , Regulación Leucémica de la Expresión Génica , Proteínas de Fusión Oncogénica/genética , Proteínas de Fusión Oncogénica/metabolismo , Receptores CXCR4/genética , Receptores CXCR4/metabolismo , Proteínas RGS/genética , Proteínas RGS/metabolismo , TransactivadoresRESUMEN
INTRODUCTION: Nucleoporin 98 (NUP98) fusion proteins are recurrently found in leukemia and are associated with unfavorable clinical outcomes. They are distributed to the nucleus and contribute to leukemogenesis via aberrant transcriptional regulation. We previously identified NUP98-BPTF (NB) fusion in patients with T-cell acute lymphoblastic leukemia (T-ALL) using next-generation sequencing. The FG-repeat of NUP98 and the PHD finger and bromodomain of bromodomain PHD finger transcription factor (BPTF) are retained in the fusion. Like other NUP98 fusion proteins, NB is considered to regulate genes that are essential for leukemogenesis. However, its target genes or pathways remain unknown. MATERIALS AND METHODS: To investigate the potential oncogenic properties of the NB fusion protein, we lentivirally transduced a doxycycline-inducible NB expression vector into mouse NIH3T3 fibroblasts and human Jurkat T-ALL cells. RESULTS: NB promoted the transformation of mouse NIH3T3 fibroblasts by upregulating the proto-oncogene Pim1, which encodes a serine/threonine kinase. NB transcriptionally regulated Pim1 expression by binding to its promoter and activated MYC and mTORC1 signaling. PIM1 knockdown or pharmacological inhibition of mTORC1 signaling suppressed NB-induced NIH3T3 cell transformation. Furthermore, NB enhanced the survival of human Jurkat T-ALL cells by inactivating the pro-apoptotic protein BCL2-associated agonist of cell death (BAD). CONCLUSION: We demonstrated the pivotal role of NB in cell transformation and survival and identified PIM1as a key downstream target of NB. These findings propose a promising therapeutic strategy for patients with NB fusion-positive leukemia.
Asunto(s)
Transformación Celular Neoplásica , Proteínas de Complejo Poro Nuclear , Proteínas de Fusión Oncogénica , Proteínas Proto-Oncogénicas c-pim-1 , Animales , Humanos , Ratones , Apoptosis , Proliferación Celular , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , Células Jurkat , Células 3T3 NIH , Proteínas de Complejo Poro Nuclear/genética , Proteínas de Complejo Poro Nuclear/metabolismo , Proteínas de Fusión Oncogénica/genética , Proteínas de Fusión Oncogénica/metabolismo , Proto-Oncogenes Mas , Proteínas Proto-Oncogénicas c-pim-1/genética , Proteínas Proto-Oncogénicas c-pim-1/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Regulación hacia ArribaRESUMEN
TAL1 is one of the most frequently dysregulated genes in T-ALL and is overexpressed in about 50% of T-ALL cases. One of the molecular mechanisms of TAL1 overexpression is abnormal mutations in the upstream region of the TAL1 promoter that introduce binding motifs for the MYB transcription factor. MYB binding at this location creates a 5' TAL1 super-enhancer (SE), which leads to aberrant expression of TAL1 and is associated with unfavorable clinical outcomes. Although targeting TAL1 is considered to be an attractive therapeutic strategy for patients with T-ALL, direct inhibition of transcription factors is challenging. Here, we show that KLF4, a known tumor suppressor in leukemic cells, suppresses SE-driven TAL1 expression in T-ALL cells. Mechanistically, KLF4 downregulates MYB expression by directly binding to its promoter and inhibits the formation of 5' TAL1 SE. In addition, we found that APTO-253, a small molecule inducer of KLF4, exerts an anti-leukemic effect by targeting SE-driven TAL1 expression in T-ALL cells. Taken together, our results suggest that the induction of KLF4 is a promising strategy to control TAL1 expression and could be a novel treatment for T-ALL patients with a poor prognosis.