HSPA8 Chaperone Complex Drives Chaperone-Mediated Autophagy Regulation in Acute Promyelocytic Leukemia Cell Differentiation.

INTRODUCTION: Acute myeloid leukemia (AML) is a cancer of the hematopoietic system characterized by hyperproliferation of undifferentiated cells of the myeloid lineage. While most of AML therapies are focused toward tumor debulking, all-trans retinoic acid (ATRA) induces neutrophil differentiation in the AML subtype acute promyelocytic leukemia (APL). Macroautophagy has been extensively investigated in the context of various cancers and is often dysregulated in AML where it can have context-dependent pro- or anti-leukemogenic effects. On the contrary, the implications of chaperone-mediated autophagy (CMA) on the pathophysiology of diseases are still being explored and its role in AML remains elusive. METHODS: We took advantage of human AML primary samples and databases to analyze CMA gene expression and activity. Furthermore, we used ATRA-sensitive (NB4) and -resistant (NB4-R1) APL cells to further dissect a potential function for CMA in ATRA-mediated neutrophil differentiation. NB4-R1 cells are unique in that they do respond to retinoic acid transcriptionally but do not mature in response to retinoid signaling alone unless maturation is triggered by adding cyclic adenosine monophosphate. RESULTS: Here, we report that CMA-related mRNA transcripts are significantly higher expressed in immature hematopoietic cells as compared to neutrophils, contrasting the macroautophagy gene expression patterns. Accordingly, lysosomal degradation of an mCherry-KFERQ CMA reporter decreases during ATRA-induced differentiation of APL cells. On the other hand, using NB4-R1 cells we found that macroautophagy flux primed ATRA-resistant NB4-R1 cells to differentiate upon ATRA treatment but reduced the association of lysosome-associated membrane protein type 2A (LAMP-2A) and heat shock protein family A (Hsp70) member 8 (HSPA8), necessary for complete neutrophil maturation. Accordingly, depletion of HSPA8 attenuated CMA activity and facilitated APL cell differentiation. In contrast, maintaining high CMA activity by ectopic expression of LAMP-2A impeded APL differentiation. CONCLUSION: Overall, our findings suggest that APL neutrophil differentiation requires CMA inactivation and that this pathway predominantly depends on HSPA8 and is possibly assisted by other co-chaperones.

MarrowCellDLD: a microfluidic method for label-free retrieval of fragile bone marrow-derived cells.

Functional bone marrow studies have focused primarily on hematopoietic progenitors, leaving limited knowledge about other fragile populations, such as bone marrow adipocytes (BMAds) and megakaryocytes. The isolation of these cells is challenging due to rupture susceptibility and large size. We introduce here a label-free cytometry microsystem, MarrowCellDLD, based on deterministic lateral displacement. MarrowCellDLD enables the isolation of large, fragile BM-derived cells based on intrinsic size properties while preserving their viability and functionality. Bone marrow adipocytes, obtained from mouse and human stromal line differentiation, as well as megakaryocytes, from primary human CD34+ hematopoietic stem and progenitor cells, were used for validation. Precise micrometer-range separation cutoffs were adapted for each cell type. Cells were sorted directly in culture media, without pre-labeling steps, and with real-time imaging for quality control. At least 106 cells were retrieved intact per sorting round. Our method outperformed two FACS instruments in purity and yield, particularly for large cell size fractions. MarrowCellDLD represents a non-destructive sorting tool for large, fragile BM-derived cells, facilitating the separation of pure populations of BMAds and megakaryocytes to further investigate their physiological and pathological roles.

Hexokinase 3 enhances myeloid cell survival via non-glycolytic functions.

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.

Corrigendum to "Chaperone-Mediated Autophagy Markers LAMP2A and HSC70 Are Independent Adverse Prognostic Markers in Primary Resected Squamous Cell Carcinomas of the Lung".

[This corrects the article DOI: 10.1155/2020/8506572.].

Lysosomes in acute myeloid leukemia: potential therapeutic targets?

Lysosomes, since their discovery, have been primarily known for degrading cellular macromolecules. However, in recent studies, they have begun to emerge as crucial regulators of cell homeostasis. They are at the crossroads of catabolic and anabolic pathways and are intricately involved in cellular trafficking, nutrient signaling, energy metabolism, and immune regulation. Their involvement in such essential cellular functions has renewed clinical interest in targeting the lysosome as a novel way to treat disease, particularly cancer. Acute myeloid leukemia (AML) is an aggressive blood cancer with a low survival probability, particularly in older patients. The genomic landscape of AML has been extensively characterized but few targeted therapies (with the exception of differentiation therapy) can achieve a long-term cure. Therefore, there is an unmet need for less intensive and more tolerable therapeutic interventions. In this review, we will give an overview on the myriad of functions performed by lysosomes and their importance in malignant disease. Furthermore, we will discuss their relevance in hematopoietic cells and different ways to potentially target them in AML.

Increased LAMP2A levels correlate with a shorter disease-free survival of HER2 negative breast cancer patients and increased breast cancer cell viability.

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.

Reducing FASN expression sensitizes acute myeloid leukemia cells to differentiation therapy.

Fatty acid synthase (FASN) is the only human lipogenic enzyme available for de novo fatty acid synthesis and is often highly expressed in cancer cells. We found that FASN mRNA levels were significantly higher in acute myeloid leukemia (AML) patients than in healthy granulocytes or CD34+ hematopoietic progenitors. Accordingly, FASN levels decreased during all-trans retinoic acid (ATRA)-mediated granulocytic differentiation of acute promyelocytic leukemia (APL) cells, partially via autophagic degradation. Furthermore, our data suggest that inhibition of FASN expression levels using RNAi or (-)-epigallocatechin-3-gallate (EGCG) accelerated the differentiation of APL cell lines and significantly re-sensitized ATRA refractory non-APL AML cells. FASN reduction promoted translocation of transcription factor EB (TFEB) to the nucleus, paralleled by activation of CLEAR network genes and lysosomal biogenesis. Together, our data demonstrate that inhibition of FASN expression in combination with ATRA treatment facilitates granulocytic differentiation of APL cells and may extend differentiation therapy to non-APL AML cells.

Chaperone-Mediated Autophagy Markers LAMP2A and HSC70 Are Independent Adverse Prognostic Markers in Primary Resected Squamous Cell Carcinomas of the Lung.

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.

The LIM Protein Ajuba Augments Tumor Metastasis in Colon Cancer.

Colorectal cancer, along with its high potential for recurrence and metastasis, is a major health burden. Uncovering proteins and pathways required for tumor cell growth is necessary for the development of novel targeted therapies. Ajuba is a member of the LIM domain family of proteins whose expression is positively associated with numerous cancers. Our data shows that Ajuba is highly expressed in human colon cancer tissue and cell lines. Publicly available data from The Cancer Genome Atlas shows a negative correlation between survival and Ajuba expression in patients with colon cancer. To investigate its function, we transduced SW480 human colon cancer cells, with lentiviral constructs to knockdown or overexpress Ajuba protein. The transcriptome of the modified cell lines was analyzed by RNA sequencing. Among the pathways enriched in the differentially expressed genes, were cell proliferation, migration and differentiation. We confirmed our sequencing data with biological assays; cells depleted of Ajuba were less proliferative, more sensitive to irradiation, migrated less and were less efficient in colony formation. In addition, loss of Ajuba expression decreased the tumor burden in a murine model of colorectal metastasis to the liver. Taken together, our data supports that Ajuba promotes colon cancer growth, migration and metastasis and therefore is a potential candidate for targeted therapy.

Assessing Autophagy in Archived Tissue or How to Capture Autophagic Flux from a Tissue Snapshot.

Autophagy is a highly conserved degradation mechanism that is essential for maintaining cellular homeostasis. In human disease, autophagy pathways are frequently deregulated and there is immense interest in targeting autophagy for therapeutic approaches. Accordingly, there is a need to determine autophagic activity in human tissues, an endeavor that is hampered by the fact that autophagy is characterized by the flux of substrates whereas histology informs only about amounts and localization of substrates and regulators at a single timepoint. Despite this challenging task, considerable progress in establishing markers of autophagy has been made in recent years. The importance of establishing clear-cut autophagy markers that can be used for tissue analysis cannot be underestimated. In this review, we attempt to summarize known techniques to quantify autophagy in human tissue and their drawbacks. Furthermore, we provide some recommendations that should be taken into consideration to improve the reliability and the interpretation of autophagy biomarkers in human tissue samples.

Correction: A specific expression profile of LC3B and p62 is associated with nonresponse to neoadjuvant chemotherapy in esophageal adenocarcinomas.

[This corrects the article DOI: 10.1371/journal.pone.0197610.].

Therapeutic Modulation of Autophagy in Leukaemia and Lymphoma.

Haematopoiesis is a tightly orchestrated process where a pool of hematopoietic stem and progenitor cells (HSPCs) with high self-renewal potential can give rise to both lymphoid and myeloid lineages. The HSPCs pool is reduced with ageing resulting in few HSPC clones maintaining haematopoiesis thereby reducing blood cell diversity, a phenomenon called clonal haematopoiesis. Clonal expansion of HSPCs carrying specific genetic mutations leads to increased risk for haematological malignancies. Therefore, it comes as no surprise that hematopoietic tumours develop in higher frequency in elderly people. Unfortunately, elderly patients with leukaemia or lymphoma still have an unsatisfactory prognosis compared to younger ones highlighting the need to develop more efficient therapies for this group of patients. Growing evidence indicates that macroautophagy (hereafter referred to as autophagy) is essential for health and longevity. This review is focusing on the role of autophagy in normal haematopoiesis as well as in leukaemia and lymphoma development. Attenuated autophagy may support early hematopoietic neoplasia whereas activation of autophagy in later stages of tumour development and in response to a variety of therapies rather triggers a pro-tumoral response. Novel insights into the role of autophagy in haematopoiesis will be discussed in light of designing new autophagy modulating therapies in hematopoietic cancers.

Cisplatin sensitivity in breast cancer cells is associated with particular DMTF1 splice variant expression.

The cyclin D binding myb-like transcription factor 1 (DMTF1) is a tumor suppressor gene that activates p14ARF transcription and thereby stabilizing the p53 tumor suppressor. The DMTF1 gene locus encodes for three different alternatively spliced isoforms, namely DMTF1α, ß and γ. The oncogenic DMTF1ß isoform negatively interferes with the transcriptional activity of DMTF1α. Increased DMTF1ß is associated with increased cell proliferation in a variety of cancer cell types. In this study, we aimed at identifying the role of DMTF1 isoforms in response to cisplatin treatment in breast cancer cells. First, we used SKBR3 (cisplatin sensitive) and MCF7 (cisplatin resistant) breast cancer cell lines to quantify DMTF1 expression in response to cisplatin treatment. Total DMTF1 mRNA levels increased in a dose dependent manner in both cell lines upon cisplatin treatment. However, the mRNA levels of the isoforms revealed that the sensitive cell line, SKBR3, showed increased levels of both isoforms, whereas the resistant cell, MCF7, only showed increased levels of the oncogenic DMTF1ß isoform. Silencing all DMTF1 isoforms led to increased cell survival upon cisplatin treatment. Furthermore, we found a significant increase in the percentage of quiescent cells in SKBR3 shDMTF1. Together, our data suggest that DMTF1 expression levels are associated with increased cisplatin resistance.

A specific expression profile of LC3B and p62 is associated with nonresponse to neoadjuvant chemotherapy in esophageal adenocarcinomas.

Paclitaxel is a powerful chemotherapeutic drug, used for the treatment of many cancer types, including esophageal adenocarcinomas (EAC). Autophagy is a lysosome-dependent degradation process maintaining cellular homeostasis. Defective autophagy has been implicated in cancer biology and therapy resistance. We aimed to assess the impact of autophagy on chemotherapy response in EAC, with a special focus on paclitaxel. Responsiveness of EAC cell lines, OE19, FLO-1, OE33 and SK-GT-4, to paclitaxel was assessed using Alamar Blue assays. Autophagic flux upon paclitaxel treatment in vitro was assessed by immunoblotting of LC3B-II and quantitative assessment of WIP1 mRNA. Immunohistochemistry for the autophagy markers LC3B and p62 was applied on tumor tissue from 149 EAC patients treated with neoadjuvant chemotherapy, including pre- and post-therapeutic samples (62 matched pairs). Tumor response was assessed by histology. For comparison, previously published data on 114 primary resected EAC cases were used. EAC cell lines displayed differing responsiveness to paclitaxel treatment; however this was not associated with differential autophagy regulation. High p62 cytoplasmic expression on its own (p ≤ 0.001), or in combination with low LC3B (p = 0.034), was associated with nonresponse to chemotherapy, regardless of whether or not the regiments contained paclitaxel, but there was no independent prognostic value of LC3B or p62 expression patterns for EAC after neoadjuvant treatment. p62 and related pathways, most likely other than autophagy, play a role in chemotherapeutic response in EAC in a clinical setting. Therefore p62 could be a novel therapeutic target to overcome chemoresistance in EAC.

Low Autophagy (ATG) Gene Expression Is Associated with an Immature AML Blast Cell Phenotype and Can Be Restored during AML Differentiation Therapy.

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.

Distinct TP73-DAPK2-ATG5 pathway involvement in ATO-mediated cell death versus ATRA-mediated autophagy responses in APL.

We have previously demonstrated that the death-associated protein kinase 2 (DAPK2) expression is significantly reduced in acute myeloid leukemia (AML), particularly in acute promyelocytic leukemia (APL) blast cells. In this study, we aimed at further understanding DAPK2 function and regulation during arsenic trioxide (ATO) cytotoxic or all-trans retinoic acid (ATRA) differentiation therapy in APL cells. We found that the p53 family member transactivation domain-p73 isoform (TAp73) binds to and activates the DAPK2 promoter, whereas the dominant-negative ΔNp73 isoform inhibits DAPK2 transcription. Furthermore, the knocking down of tumor protein p73 (TP73) in NB4 cells resulted in reduced DAPK2 expression associated with decreased cell death and autophagy upon ATO and ATRA treatment, respectively. Moreover, the silencing of DAPK2 revealed that DAPK2 is an important downstream effector of p73 in ATO-induced apoptosis but not autophagy responses of APL cells. In contrast, the p73-DAPK2 pathway is essential for ATRA-induced autophagy that is mediated by an interaction of DAPK2 with the key autophagy-related protein (ATG)5. Lastly, we show that DAPK2 binds and stabilizes the p73 protein; thus, we propose a novel mechanism by which ATO- or ATRA-induced therapy responses initiate a positive p73-DAPK2 feedback loop.

PU.1 supports TRAIL-induced cell death by inhibiting NF-κB-mediated cell survival and inducing DR5 expression.

The hematopoietic Ets-domain transcription factor PU.1/SPI1 orchestrates myeloid, B- and T-cell development, and also supports hematopoietic stem cell maintenance. Although PU.1 is a renowned tumor suppressor in acute myeloid leukemia (AML), a disease characterized by an accumulation of immature blast cells, comprehensive studies analyzing the role of PU.1 during cell death responses in AML treatment are missing. Modulating PU.1 expression in AML cells, we found that PU.1 supports tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis via two mechanisms: (a) by repressing NF-κB activity via a novel direct PU.1-RelA/p65 protein-protein interaction, and (b) by directly inducing TRAIL receptor DR5 expression. Thus, expression of NF-κB-regulated antiapoptotic genes was sustained in PU.1-depleted AML cells upon TRAIL treatment and DR5 levels were decreased. Last, PU.1 deficiency significantly increased AML cell resistance to anthracycline treatment. Altogether, these results reveal a new facet of PU.1's tumor suppressor function during antileukemic therapies.

The LMO2 oncogene regulates DNA replication in hematopoietic cells.

Oncogenic transcription factors are commonly activated in acute leukemias and subvert normal gene expression networks to reprogram hematopoietic progenitors into preleukemic stem cells, as exemplified by LIM-only 2 (LMO2) in T-cell acute lymphoblastic leukemia (T-ALL). Whether or not these oncoproteins interfere with other DNA-dependent processes is largely unexplored. Here, we show that LMO2 is recruited to DNA replication origins by interaction with three essential replication enzymes: DNA polymerase delta (POLD1), DNA primase (PRIM1), and minichromosome 6 (MCM6). Furthermore, tethering LMO2 to synthetic DNA sequences is sufficient to transform these sequences into origins of replication. We next addressed the importance of LMO2 in erythroid and thymocyte development, two lineages in which cell cycle and differentiation are tightly coordinated. Lowering LMO2 levels in erythroid progenitors delays G1-S progression and arrests erythropoietin-dependent cell growth while favoring terminal differentiation. Conversely, ectopic expression in thymocytes induces DNA replication and drives these cells into cell cycle, causing differentiation blockade. Our results define a novel role for LMO2 in directly promoting DNA synthesis and G1-S progression.