RESUMO
Acute myeloid leukemia (AML) is an age-related disease that is highly dependent on the bone marrow (BM) microenvironment. With increasing age, tissues accumulate senescent cells, characterized by an irreversible arrest of cell proliferation and the secretion of a set of proinflammatory cytokines, chemokines, and growth factors, collectively known as the senescence-associated secretory phenotype (SASP). Here, we report that AML blasts induce a senescent phenotype in the stromal cells within the BM microenvironment and that the BM stromal cell senescence is driven by p16INK4a expression. The p16INK4a-expressing senescent stromal cells then feed back to promote AML blast survival and proliferation via the SASP. Importantly, selective elimination of p16INK4a+ senescent BM stromal cells in vivo improved the survival of mice with leukemia. Next, we find that the leukemia-driven senescent tumor microenvironment is caused by AML-induced NOX2-derived superoxide. Finally, using the p16-3MR mouse model, we show that by targeting NOX2 we reduced BM stromal cell senescence and consequently reduced AML proliferation. Together, these data identify leukemia-generated NOX2-derived superoxide as a driver of protumoral p16INK4a-dependent senescence in BM stromal cells. Our findings reveal the importance of a senescent microenvironment for the pathophysiology of leukemia. These data now open the door to investigate drugs that specifically target the "benign" senescent cells that surround and support AML.
Assuntos
Medula Óssea/patologia , Senescência Celular , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Leucemia Mieloide Aguda/patologia , Microambiente Tumoral , Animais , Medula Óssea/metabolismo , Proliferação de Células , Técnicas de Cocultura , Feminino , Humanos , Leucemia Mieloide Aguda/metabolismo , Células-Tronco Mesenquimais/metabolismo , Células-Tronco Mesenquimais/patologia , Camundongos Endogâmicos C57BL , NADPH Oxidase 2/metabolismo , Superóxidos/metabolismo , Células Tumorais CultivadasRESUMO
Approximately 80% of patients diagnosed with acute myeloid leukemia (AML) die as a consequence of failure to eradicate the tumor from the bone marrow microenvironment. We have recently shown that stroma-derived interleukin-8 (IL-8) promotes AML growth and survival in the bone marrow in response to AML-derived macrophage migration inhibitory factor (MIF). In the present study we show that high constitutive expression of MIF in AML blasts in the bone marrow is hypoxia-driven and, through knockdown of MIF, HIF1α and HIF2α, establish that hypoxia supports AML tumor proliferation through HIF1α signaling. In vivo targeting of leukemic cell HIF1α inhibits AML proliferation in the tumor microenvironment through transcriptional regulation of MIF, but inhibition of HIF2α had no measurable effect on AML blast survival. Functionally, targeted inhibition of MIF in vivo improves survival in models of AML. Here we present a mechanism linking HIF1α to a pro-tumoral chemokine factor signaling pathway and in doing so, we establish a potential strategy to target AML.
Assuntos
Medula Óssea/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Oxirredutases Intramoleculares/genética , Leucemia Mieloide Aguda/genética , Fatores Inibidores da Migração de Macrófagos/genética , Regulação para Cima , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Hipóxia Celular , Linhagem Celular Tumoral , Proliferação de Células , Sobrevivência Celular , Feminino , Técnicas de Silenciamento de Genes , Humanos , Oxirredutases Intramoleculares/metabolismo , Leucemia Mieloide Aguda/metabolismo , Leucemia Mieloide Aguda/patologia , Fatores Inibidores da Migração de Macrófagos/metabolismo , Camundongos , Transplante de Neoplasias , Transdução de Sinais , Microambiente TumoralRESUMO
Acute myeloid leukemia (AML) cells exhibit a high level of spontaneous apoptosis when cultured in vitro but have a prolonged survival time in vivo, indicating that tissue microenvironment plays a critical role in promoting AML cell survival. In vitro studies have shown that bone marrow mesenchymal stromal cells (BM-MSC) protect AML blasts from spontaneous and chemotherapy-induced apoptosis. Here, we report a novel interaction between AML blasts and BM-MSCs, which benefits AML proliferation and survival. We initially examined the cytokine profile in cultured human AML compared with AML cultured with BM-MSCs and found that macrophage migration inhibitory factor (MIF) was highly expressed by primary AML, and that IL8 was increased in AML/BM-MSC cocultures. Recombinant MIF increased IL8 expression in BM-MSCs via its receptor CD74. Moreover, the MIF inhibitor ISO-1 inhibited AML-induced IL8 expression by BM-MSCs as well as BM-MSC-induced AML survival. Protein kinase C ß (PKCß) regulated MIF-induced IL8 in BM-MSCs. Finally, targeted IL8 shRNA inhibited BM-MSC-induced AML survival. These results describe a novel, bidirectional, prosurvival mechanism between AML blasts and BM-MSCs. Furthermore, they provide biologic rationale for therapeutic strategies in AML targeting the microenvironment, specifically MIF and IL8. Cancer Res; 77(2); 303-11. ©2016 AACR.
