RESUMO
Acute lymphoblastic leukemia (ALL) is a leading cause of cancer-related death in children and adolescents, and cure rates for relapsed/refractory ALL remain dismal, highlighting the need for novel targeted therapies. To identify genome-wide metabolic-stress regulated genes, we used RNA-sequencing in ALL cells treated with AICAR, an AMPK activator. RNA-sequencing identified the immediate early genes (IEGs) as a subset of genes downregulated by AICAR. We show that AICAR-induced IEGs downregulation was blocked by an adenosine uptake inhibitor indicating AICAR was responsible for IEGs reprogramming. Using pharmacologic and genetic models we established this mechanism was AMPK-independent. Further investigations using kinase assays, PKD/PKC inhibitors and rescue experiments, demonstrated that AICAR directly inhibited PKD kinase activity and identified PKD as responsible for IEGs downregulation. Mechanistically, PKD inhibition suppressed phosphorylation and nuclear export of class IIa HDACs, which lowered histone H3 acetylation and decreased NFκB(p65) recruitment to IEGs promoters. Finally, PKD inhibition induced apoptosis via DUSP1/DUSP6 downregulation eliciting a DNA damage response. More importantly, ALL patient cells exhibited the same PKD-HDACs-IEGs-mediated mechanism. As proof of principle of the therapeutic potential of targeting PKD, we established the in vivo relevance of our findings using an NSG ALL mouse model. In conclusion, we identified a previously unreported PKD-dependent survival mechanism in response to AICAR-induced cellular stress in ALL through regulation of DUSPs and IEGs' expression. IMPLICATIONS: PKD mediates early transcriptional responses in ALL cells as an adaptive survival mechanism to overcome cellular stress.
Assuntos
Regulação para Baixo/genética , Histona Desacetilases/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Proteína Quinase C/genética , Aminoimidazol Carboxamida/análogos & derivados , Animais , Apoptose/genética , Linhagem Celular Tumoral , Dano ao DNA/genética , Ativação Enzimática/genética , Células HEK293 , Células HeLa , Humanos , Células Jurkat , Camundongos , Regiões Promotoras Genéticas/genética , Proteínas Serina-Treonina Quinases/genética , Ribonucleotídeos/genética , Transdução de Sinais/genéticaRESUMO
The transmembrane neural cell adhesion receptor L1 is a Wnt/ß-catenin target gene expressed in many tumor types. In human colorectal cancer, L1 localizes preferentially to the invasive front of tumors and when overexpressed in colorectal cancer cells, it facilitates their metastasis to the liver. In this study, we investigated genes that are regulated in human colorectal cancer and by the L1-NF-κB pathway that has been implicated in liver metastasis. c-Kit was the most highly suppressed gene in both colorectal cancer tissue and the L1-NF-κB pathway. c-Kit suppression that resulted from L1-mediated signaling relied upon NF-κB, which directly inhibited the transcription of SP1, a major activator of the c-Kit gene promoter. Reconstituting c-Kit expression in L1-transfected cells blocked the biological effects conferred by L1 overexpression in driving motility and liver metastasis. We found that c-Kit expression in colorectal cancer cells is associated with a more pronounced epithelial morphology, along with increased expression of E-cadherin and decreased expression of Slug. Although c-Kit overexpression inhibited the motility and metastasis of L1-expressing colorectal cancer cells, it enhanced colorectal cancer cell proliferation and tumorigenesis, arguing that separate pathways mediate tumorigenicity and metastasis by c-Kit. Our findings provide insights into how colorectal cancer metastasizes to the liver, the most common site of dissemination in this cancer.