RESUMEN
The family of hexokinases (HKs) catalyzes the first step of glycolysis, the ATP-dependent phosphorylation of glucose to glucose-6-phosphate. While HK1 and HK2 are ubiquitously expressed, the less well-studied HK3 is primarily expressed in hematopoietic cells and tissues and is highly upregulated during terminal differentiation of some acute myeloid leukemia (AML) cell line models. Here we show that expression of HK3 is predominantly originating from myeloid cells and that the upregulation of this glycolytic enzyme is not restricted to differentiation of leukemic cells but also occurs during ex vivo myeloid differentiation of healthy CD34+ hematopoietic stem and progenitor cells. Within the hematopoietic system, we show that HK3 is predominantly expressed in cells of myeloid origin. CRISPR/Cas9 mediated gene disruption revealed that loss of HK3 has no effect on glycolytic activity in AML cell lines while knocking out HK2 significantly reduced basal glycolysis and glycolytic capacity. Instead, loss of HK3 but not HK2 led to increased sensitivity to ATRA-induced cell death in AML cell lines. We found that HK3 knockout (HK3-null) AML cells showed an accumulation of reactive oxygen species (ROS) as well as DNA damage during ATRA-induced differentiation. RNA sequencing analysis confirmed pathway enrichment for programmed cell death, oxidative stress, and DNA damage response in HK3-null AML cells. These signatures were confirmed in ATAC sequencing, showing that loss of HK3 leads to changes in chromatin configuration and increases the accessibility of genes involved in apoptosis and stress response. Through isoform-specific pulldowns, we furthermore identified a direct interaction between HK3 and the proapoptotic BCL-2 family member BIM, which has previously been shown to shorten myeloid life span. Our findings provide evidence that HK3 is dispensable for glycolytic activity in AML cells while promoting cell survival, possibly through direct interaction with the BH3-only protein BIM during ATRA-induced neutrophil differentiation.
Asunto(s)
Hexoquinasa , Leucemia Mieloide Aguda , Supervivencia Celular/genética , Glucólisis/genética , Hexoquinasa/genética , Hexoquinasa/metabolismo , Humanos , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/metabolismo , Células Mieloides/metabolismoRESUMEN
[This corrects the article DOI: 10.1155/2020/8506572.].
RESUMEN
Macroautophagy (herein referred to as autophagy) is a complex catabolic process characterized by the formation of double-membrane vesicles called autophagosomes. During this process, autophagosomes engulf and deliver their intracellular content to lysosomes, where they are degraded by hydrolytic enzymes. Thereby, autophagy provides energy and building blocks to maintain cellular homeostasis and represents a dynamic recycling mechanism. Importantly, the clearance of damaged organelles and aggregated molecules by autophagy in normal cells contributes to cancer prevention. Therefore, the dysfunction of autophagy has a major impact on the cell fate and can contribute to tumorigenesis. Breast cancer is the most common cancer in women and has the highest mortality rate among all cancers in women worldwide. Breast cancer patients often have a good short-term prognosis, but long-term survivors often experience aggressive recurrence. This phenomenon might be explained by the high heterogeneity of breast cancer tumors rendering mammary tumors difficult to target. This review focuses on the mechanisms of autophagy during breast carcinogenesis and sheds light on the role of autophagy in the traits of aggressive breast cancer cells such as migration, invasion, and therapeutic resistance.
Asunto(s)
Autofagia , Neoplasias de la Mama/patología , Carcinogénesis/patología , Transformación Celular Neoplásica , Animales , Línea Celular Tumoral , Femenino , Humanos , Recurrencia Local de NeoplasiaRESUMEN
Chaperone Mediated Autophagy (CMA) is a selective autophagy pathway deregulated in many cancers. In this study, we were aiming at understanding the importance of CMA in breast cancer. To this end, we examined the expression of the CMA markers HSP8 and LAMP2A in different breast cancer cell lines and found a wide range of LAMP2A expression levels across the cell lines analyzed. Next, we applied a specific immunohistochemical staining protocol to a tissue microarray derived from a cohort of 365 breast cancer patients. Therefore, we were able to find a correlation of high LAMP2A but not HSPA8 (HSC70) with worse disease free survival in patients with HER2 negative tumors (p = 0.026) which was independent prognostic parameter from pT category, pN category and grading in a multivariate model (HR = 1.889; 95% CI = 1.039-3.421; p = 0.037). In line, low LAMP2A levels decrease proliferation of the breast cancer cell lines T47D and MCF-7 in vitro. Our data suggest that LAMP2A supports a more severe breast cancer cell phenotype.
Asunto(s)
Neoplasias de la Mama/metabolismo , Técnicas de Cultivo de Célula/métodos , Proteína 2 de la Membrana Asociada a los Lisosomas/metabolismo , Receptor ErbB-2/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Western Blotting , Neoplasias de la Mama/genética , Neoplasias de la Mama/terapia , Línea Celular Tumoral , Proliferación Celular/genética , Supervivencia Celular/genética , Autofagia Mediada por Chaperones/genética , Supervivencia sin Enfermedad , Femenino , Humanos , Proteína 2 de la Membrana Asociada a los Lisosomas/genética , Células MCF-7 , Persona de Mediana Edad , Interferencia de ARNRESUMEN
ALK inhibitors effectively target EML4-ALK positive non-small cell lung cancer, but their effects are hampered by treatment resistance. In the present study, we asked whether ALK inhibition affects autophagy, and whether this may influence treatment response. Whereas the impact of targeted therapies on autophagic activity previously have been assessed by surrogate marker proteins such as LC3B, we here thoroughly examined effects on functional autophagic activity, i.e. on the sequestration and degradation of autophagic cargo, in addition to autophagic markers. Interestingly, the ALK inhibitor Ceritinib decreased mTOR activity and increased GFP-WIPI1 dot formation in H3122 and H2228 EML4-ALK+ lung cancer cells, suggesting autophagy activation. Moreover, an mCherry-EGFP-LC3B based assay indicated elevated LC3B carrier flux upon ALK inhibition. In accordance, autophagic cargo sequestration and long-lived protein degradation significantly increased upon ALK inhibition. Intriguingly, autophagic cargo flux was dependent on VPS34 and ULK1, but not LC3B. Co-treating H3122 cells with Ceritinib and a VPS34 inhibitor or Bafilomycin A1 resulted in reduced cell numbers. Moreover, VPS34 inhibition reduced clonogenic recovery of Ceritinib-treated cells. In summary, our results indicate that ALK inhibition triggers LC3B-independent macroautophagic flux in EML4-ALK+ cells to support cancer cell survival and clonogenic growth.
Asunto(s)
Quinasa de Linfoma Anaplásico/antagonistas & inhibidores , Antineoplásicos/farmacología , Autofagia/efectos de los fármacos , Carcinoma de Pulmón de Células no Pequeñas/inmunología , Neoplasias Pulmonares/inmunología , Proteínas de Fusión Oncogénica/metabolismo , Pirimidinas/farmacología , Sulfonas/farmacología , Homólogo de la Proteína 1 Relacionada con la Autofagia/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/enzimología , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Fosfatidilinositol 3-Quinasas Clase III/antagonistas & inhibidores , Fosfatidilinositol 3-Quinasas Clase III/metabolismo , Humanos , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Neoplasias Pulmonares/enzimología , Neoplasias Pulmonares/metabolismo , Proteínas Asociadas a Microtúbulos/metabolismoRESUMEN
LAMP2A and HSC70 are crucial players in chaperone-mediated autophagy (CMA), a targeted, lysosome-dependent protein degradation pathway. Elevated LAMP2A levels, indicative of increased CMA activity, are observed in several malignancies, and CMA downregulation may be exploited therapeutically. We evaluated the impact of LAMP2A and HSC70 in pulmonary squamous cell carcinomas (pSQCC). Antibodies were validated by knockdown and overexpression experiments using three different cell lines. Expression levels in tissue were analyzed by immunohistochemistry in a cohort of 336 consecutive pSQCC using tissue microarrays. There was no significant correlation between the two markers among each other and no association with pathological parameters (TNM categories, grading). However, both high LAMP2A and HSC70 expression were associated with worse outcome, including overall survival (OS; p = 0.012 and p = 0.001) and disease free survival (DFS; p = 0.049 and p = 0.036). In multivariate analysis, both markers and a combination of them were independent adverse prognostic factors for OS (LAMP2Ahigh: HR = 2.059; p < 0.001; HSC70high: HR = 1.987; p < 0.001; LAMP2Ahigh/HSC70high: HR = 1.529; p < 0.001) and DFS (LAMP2Ahigh: HR = 1.709; p = 0.004; HSC70high: HR = 1.484; p = 0.027; LAMP2Ahigh/HSC70high: HR = 1.342, p < 0.001). The negative prognostic impact of high LAMP2A and HSC70 and their variable expression in pSQCC may justify the use of these proteins as potential biomarkers for future CMA-inhibiting therapies.
Asunto(s)
Carcinoma de Células Escamosas/diagnóstico , Autofagia Mediada por Chaperones/genética , Proteínas del Choque Térmico HSC70/metabolismo , Neoplasias Pulmonares/diagnóstico , Proteína 2 de la Membrana Asociada a los Lisosomas/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Biomarcadores/metabolismo , Carcinoma de Células Escamosas/mortalidad , Carcinoma de Células Escamosas/patología , Supervivencia sin Enfermedad , Femenino , Proteínas del Choque Térmico HSC70/genética , Humanos , Estimación de Kaplan-Meier , Neoplasias Pulmonares/mortalidad , Neoplasias Pulmonares/patología , Proteína 2 de la Membrana Asociada a los Lisosomas/genética , Masculino , Persona de Mediana Edad , Pronóstico , Modelos de Riesgos Proporcionales , Estudios RetrospectivosRESUMEN
Lysosomal sequestration of anti-cancer compounds reduces drug availability at intracellular target sites, thereby limiting drug-sensitivity and inducing chemoresistance. For hepatocellular carcinoma (HCC), sorafenib (SF) is the first line systemic treatment, as well as a simultaneous activator of autophagy-induced drug resistance. The purpose of this study is to elucidate how combination therapy with the FDA-approved photosensitizer verteporfin (VP) can potentiate the antitumor effect of SF, overcoming its acquired resistance mechanisms. HCC cell lines and patient-derived in vitro and in vivo preclinical models were used to identify the molecular mechanism of action of VP alone and in combination with SF. We demonstrate that SF is lysosomotropic and increases the total number of lysosomes in HCC cells and patient-derived xenograft model. Contrary to the effect on lysosomal stability by SF, VP is not only sequestered in lysosomes, but induces lysosomal pH alkalinization, lysosomal membrane permeabilization (LMP) and tumor-selective proteotoxicity. In combination, VP-induced LMP potentiates the antitumor effect of SF, further decreasing tumor proliferation and progression in HCC cell lines and patient-derived samples in vitro and in vivo. Our data suggest that combination of lysosome-targeting compounds, such as VP, in combination with already approved chemotherapeutic agents could open a new avenue to overcome chemo-insensitivity caused by passive lysosomal sequestration of anti-cancer drugs in the context of HCC.
Asunto(s)
Carcinoma Hepatocelular/patología , Neoplasias Hepáticas/patología , Lisosomas/metabolismo , Sorafenib/farmacología , Verteporfina/farmacología , Álcalis/química , Animales , Autofagia/efectos de los fármacos , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Sinergismo Farmacológico , Hepatocitos/efectos de los fármacos , Hepatocitos/metabolismo , Humanos , Concentración de Iones de Hidrógeno , Membranas Intracelulares/efectos de los fármacos , Membranas Intracelulares/metabolismo , Lisosomas/efectos de los fármacos , Masculino , Ratones , Modelos Biológicos , Proteínas de Neoplasias/toxicidad , Permeabilidad , Proteínas ras/metabolismoRESUMEN
Retinoids are derived from vitamin A through a multi-step process. Within a target cell, retinoids regulate gene expression by activating the retinoid acid receptors (RAR) and retinoid x receptors (RXR), which are ligand-dependent transcription factors. Besides its therapeutic use in dermatological disorders, all-trans retinoic acid (ATRA) is successfully utilized to treat acute promyelocytic leukemia (APL) patients. The use of ATRA in APL patients is the first example of clinically useful differentiation therapy. Therapeutic strategies aiming at cancer cell differentiation have great potential for solid tumors, including breast cancer. The few clinical studies conducted with ATRA in breast cancer are rather disappointing. However, these studies did not take into account the heterogeneity of the disease and were conducted on unselected cohorts of patients.We recently showed that ATRA treatment of breast cancer cells induces autophagy, a highly conserved process aiming at degrading and recycling superfluous or harmful cellular components. In addition, autophagy inhibition significantly increases the therapeutic activity of ATRA. This finding is of fundamental importance, since autophagy has a dual role in cancer. Whereas autophagy may be a protective mechanism during the initial phases of cancer development, it may support cancer cell survival in already established tumors. Furthermore, autophagy can lower or enhance therapeutic efficiency, depending on the tumor type and the anticancer agent considered. Therefore, it is important to investigate the role of autophagy in the context of specific tumors and therapeutic approaches. Accurate autophagy studies are challenging given the dynamic nature of the process and the difficulty of measuring the rate of autophagosome degradation (autophagic flux). In this chapter, we provide protocols for a careful assessment of the autophagic flux in ATRA treated 2D and 3D breast cancer cultures.
Asunto(s)
Antineoplásicos/farmacología , Autofagia/efectos de los fármacos , Neoplasias de la Mama/metabolismo , Tretinoina/farmacología , Neoplasias de la Mama/tratamiento farmacológico , Técnicas de Cultivo de Célula , Línea Celular Tumoral , Separación Celular , Femenino , Citometría de Flujo , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , HumanosRESUMEN
Esophageal adenocarcinoma (EAC) is a highly lethal cancer type with an overall poor survival rate. Twenty to thirty percent of EAC overexpress the human epidermal growth factor receptor 2 (Her2), a transmembrane receptor tyrosine kinase promoting cell growth and proliferation. Patients with Her2 overexpressing breast and gastroesophageal cancer may benefit from Her2 inhibitors. Therapy resistance, however, is well documented. Since autophagy, a lysosome-dependent catabolic process, is implicated in cancer resistance mechanisms, we tested whether autophagy modulation influences Her2 inhibitor sensitivity in EAC. Her2-positive OE19 EAC cells showed an induction in autophagic flux upon treatment with the small molecule Her2 inhibitor Lapatinib. Newly generated Lapatinib-resistant OE19 (OE19 LR) cells showed increased basal autophagic flux compared to parental OE19 (OE19 P) cells. Based on these results, we tested if combining Lapatinib with autophagy inhibitors might be beneficial. OE19 P showed significantly reduced cell viability upon double treatment, while OE19 LR were already sensitive to autophagy inhibition alone. Additionally, Her2 status and autophagy marker expression (LC3B and p62) were investigated in a treatment-naïve EAC patient cohort (n = 112) using immunohistochemistry. Here, no significant correlation between Her2 status and expression of LC3B and p62 was found. Our data show that resistance to Her2-directed therapy is associated with a higher basal autophagy level, which is not per se associated with Her2 status. Therefore, we propose that autophagy may contribute to acquired resistance to Her2-targeted therapy in EAC, and that combining Her2 and autophagy inhibition might be beneficial for EAC patients.
Asunto(s)
Adenocarcinoma/tratamiento farmacológico , Antineoplásicos/farmacología , Autofagia/efectos de los fármacos , Neoplasias Esofágicas/tratamiento farmacológico , Lapatinib/farmacología , Adenocarcinoma/metabolismo , Antineoplásicos/uso terapéutico , Línea Celular Tumoral , Resistencia a Antineoplásicos , Neoplasias Esofágicas/metabolismo , Células HEK293 , Humanos , Lapatinib/uso terapéutico , Receptor ErbB-2/antagonistas & inhibidoresRESUMEN
Autophagy is an intracellular degradation system that ensures a dynamic recycling of a variety of building blocks required for self-renewal, homeostasis, and cell survival under stress. We used primary acute myeloid leukemia (AML) samples and human AML cell lines to investigate the regulatory mechanisms of autophagy and its role in AML differentiation. We found a significantly lower expression of key autophagy- (ATG-) related genes in primary AML as compared to healthy granulocytes, an increased autophagic activity during all-trans retinoic acid- (ATRA-) induced neutrophil differentiation, and an impaired AML differentiation upon inhibition of ATG3, ATG4D, and ATG5. Supporting the notion of noncanonical autophagy, we found that ATRA-induced autophagy was Beclin1-independent compared to starvation- or arsenic trioxide- (ATO-) induced autophagy. Furthermore, we identified PU.1 as positive transcriptional regulator of ATG3, ATG4D, and ATG5. Low PU.1 expression in AML may account for low ATG gene expression in this disease. Low expression of the autophagy initiator ULK1 in AML can partially be attributed to high expression of the ULK1-targeting microRNA-106a. Our data clearly suggest that granulocytic AML differentiation relies on noncanonical autophagy pathways and that restoring autophagic activity might be beneficial in differentiation therapies.
Asunto(s)
Autofagia/genética , Diferenciación Celular/genética , Expresión Génica/genética , Leucemia Mieloide Aguda/genética , Línea Celular Tumoral , Humanos , Leucemia Mieloide Aguda/patología , Leucemia Mieloide Aguda/terapia , FenotipoRESUMEN
Acute myeloid leukemia (AML) is a malignancy of myeloid progenitor cells that are blocked in differentiation. Acute promyelocytic leukemia (APL) is a rare form of AML, which generally presents with a t(15;17) translocation causing expression of the fusion protein PML-RARA. Pharmacological doses of all-trans retinoic acid (ATRA) induce granulocytic differentiation of APL cells leading to cure rates of >80% if combined with conventional chemotherapy. Autophagy is a lysosomal degradation pathway for the removal of cytoplasmic content and recycling of macromolecules. ATRA induces autophagy in ATRA-sensitive AML and APL cells and autophagy inhibition attenuates ATRA-triggered differentiation. In this study, we aimed at identifying if the autophagy-linked FYVE-domain containing protein (ALFY/WDFY3) is involved in autophagic degradation of protein aggregates contributes to ATRA therapy-induced autophagy. We found that ALFY mRNA levels increase significantly during the course of ATRA-induced differentiation of APL and AML cell lines. Importantly ALFY depletion impairs ATRA-triggered granulocytic differentiation of these cells. In agreement with its function in aggrephagy, knockdown of ALFY results in reduced ATRA-induced proteolysis. Our data further suggest that PML-RARα is an autophagy substrate degraded with the help of ALFY. In summary, we present a crucial role for ALFY in retinoid triggered maturation of AML cells.
Asunto(s)
Autofagia , Diferenciación Celular , Leucemia Mieloide Aguda/patología , Proteínas de la Membrana/metabolismo , Factores de Transcripción/metabolismo , Proteínas Adaptadoras Transductoras de Señales , Autofagia/efectos de los fármacos , Proteínas Relacionadas con la Autofagia , Diferenciación Celular/efectos de los fármacos , Línea Celular Tumoral , Regulación hacia Abajo/efectos de los fármacos , Regulación hacia Abajo/genética , Regulación Leucémica de la Expresión Génica , Células HEK293 , Humanos , Leucemia Mieloide Aguda/genética , Lisosomas/efectos de los fármacos , Lisosomas/metabolismo , Proteínas de la Membrana/genética , MicroARNs/genética , MicroARNs/metabolismo , Neutrófilos/efectos de los fármacos , Neutrófilos/patología , Proteolisis/efectos de los fármacos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Factores de Transcripción/genética , Tretinoina/farmacología , Regulación hacia Arriba/efectos de los fármacos , Regulación hacia Arriba/genéticaRESUMEN
Autophagy is a cellular degrading process that promotes tumor cell survival or cell death in cancer, depending on the progress of oncogenesis. Protein light chain 3 (LC3) and p62/SQSTM1 (p62) are associated with autophagosomal membranes that engulf cytoplasmic content for subsequent degradation. We studied LC3 and p62 expression using immunohistochemistry in a large cohort of 466 stage I/II non-small cell lung cancer (NSCLC) using a tissue microarray. We evaluated dot-like cytoplasmic expression of LC3 and dot-like, cytoplasmic and nuclear staining for p62 in relation to clinico-pathological parameters.LC3 expression correlated with all p62 patterns, as those correlated among each other (p < 0.001 each). There was no correlation with stage, age or gender. A combination of high LC3/high p62 dot-like staining (suggesting impaired autophagy) showed a trend for better outcome (p = 0.11). Interestingly, a combined low cytoplasmic/low nuclear p62 expression regardless of dot-like staining was an independent prognostic factor for longer survival (p = 0.006; HR=1.96), in addition to tumor stage (p = 0.004; HR=1.4).The autophagy markers LC3 and p62 are differentially expressed in NSCLC, pointing towards a biologically significant role. High LC3 levels seem to be linked to lower tumor aggressiveness, while high general p62 expression was significantly associated with aggressive tumor behavior.
Asunto(s)
Autofagia , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Neoplasias Pulmonares/metabolismo , Proteínas Asociadas a Microtúbulos/metabolismo , Proteínas de Unión al ARN/metabolismo , Anciano , Carcinoma de Pulmón de Células no Pequeñas/diagnóstico , Núcleo Celular/metabolismo , Citoplasma/metabolismo , Femenino , Regulación Neoplásica de la Expresión Génica , Humanos , Inmunohistoquímica , Neoplasias Pulmonares/diagnóstico , Masculino , Persona de Mediana Edad , Análisis Multivariante , Pronóstico , Estudios Retrospectivos , Análisis de Matrices Tisulares , Resultado del TratamientoRESUMEN
Esophageal adenocarcinomas (EAC) are aggressive tumors with considerable rates of chemoresistance. Autophagy is a lysosome-dependent degradation process, characterized by the formation of vesicles called autophagosomes, and has been implicated in cancer. Protein light chain 3 B (LC3B) and p62 are associated with autophagosomal membranes and degraded. We aimed to assess the impact of basal autophagy on EAC. In EAC cell lines, an increase in LC3B and p62 was observed with increasing concentrations of the autophagy inhibitor chloroquine, which indicates functional basal autophagy. LC3B and p62 immunohistochemistry was performed on primary resected EAC. High LC3B and p62 expression was associated with earlier tumor stages (p < 0.05). High nuclear and cytoplasmic p62 staining were associated with a better prognosis (p = 0.006; p = 0.028). Various combinations of p62 expression with or without LC3B expression identified different prognostic groups. Tumors with low total p62 (p = 0.007) or low LC3B/low p62 expression had the worst outcome (p = 0.007; p = 0.005). A combination score of dot-like/cytoplasmic p62 and nuclear p62 staining was an independent prognostic parameter (p = 0.033; HR = 0.6). This study highlights the potential significance of basal autophagy in EAC biology. Tumors with low LC3B and p62 expression show the most aggressive behavior and may be candidates for autophagy regulating therapeutics.
Asunto(s)
Adenocarcinoma/diagnóstico , Autofagia , Neoplasias Esofágicas/diagnóstico , Proteínas Asociadas a Microtúbulos/metabolismo , Proteínas de Unión al ARN/metabolismo , Adenocarcinoma/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Biomarcadores de Tumor/metabolismo , Neoplasias Esofágicas/metabolismo , Femenino , Humanos , Lisosomas/química , Masculino , Persona de Mediana Edad , Pronóstico , Resultado del TratamientoRESUMEN
DAPK2 is a proapoptotic protein that is mostly expressed in the hematopoietic tissue. A detailed DAPK2 expression analysis in two large AML patient cohorts revealed particularly low DAPK2 mRNA levels in APL. DAPK2 levels were restored in APL patients undergoing ATRA therapy. PML-RARA is the predominant lesion in APL causing transcriptional repression of genes important for neutrophil differentiation. We found binding of PML-RARA and PU.1, a myeloid master regulator, to RARA and PU.1 binding sites in the DAPK2 promoter. Ectopic expression of PML-RARA in non-APL, as well as knocking down PU.1 in APL cells, resulted in a significant reduction of DAPK2 expression. Restoring DAPK2 expression in PU.1 knockdown APL cells partially rescued neutrophil differentiation, thereby identifying DAPK2 as a relevant PU.1 downstream effector. Moreover, low DAPK2 expression is also associated with C/EBPα-mutated AML patients, and we found C/EBPα-dependent regulation of DAPK2 during APL differentiation. In conclusion, we identified first inhibitory mechanisms responsible for the low DAPK2 expression in particular AML subtypes, and the regulation of DAPK2 by two myeloid transcription factors underlines its importance in neutrophil development.
Asunto(s)
Proteína alfa Potenciadora de Unión a CCAAT/metabolismo , Diferenciación Celular/genética , Proteínas Quinasas Asociadas a Muerte Celular/genética , Regulación de la Expresión Génica , Granulocitos/citología , Granulocitos/metabolismo , Proteínas de Fusión Oncogénica/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Transactivadores/metabolismo , Línea Celular Tumoral , Proteínas Quinasas Asociadas a Muerte Celular/metabolismo , Humanos , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/metabolismo , Leucemia Promielocítica Aguda/genética , Leucemia Promielocítica Aguda/metabolismo , Neutrófilos/citología , Neutrófilos/metabolismo , Transcripción GenéticaRESUMEN
BACKGROUND: Inhibitors of apoptosis (IAPs) were intensively investigated in the context of cancer where they promote tumor growth and chemoresistence. Overexpression of the IAP BIRC6 is associated with unfavorable clinical features and negatively impacts relapse-free survival in childhood acute myeloid leukemia (AML). Currently, BIRC6 levels in adult primary AML have not been compared to the expression in normal myeloid cells. Thus, we compared for the first time BIRC6 levels in adult primary AML patient samples to normal myeloid cells and studied its regulation and function during neutrophil differentiation. FINDINGS: We found significantly lower BIRC6 levels in particular AML subtypes as compared to granulocytes from healthy donors. The lowest BIRC6 expression was found in CD34+ progenitor cells. Moreover, BIRC6 expression significantly increased during neutrophil differentiation of AML cell lines and knocking down BIRC6 in NB4 acute promyelocytic leukemia (APL) cells significantly impaired neutrophil differentiation, but not cell viability. CONCLUSION: Together, we found an association of low BIRC6 levels with an immature myeloid phenotype and describe a function for BIRC6 in neutrophil differentiation of APL cells.