Dual targeting of glutamine and serine metabolism in acute myeloid leukemia.

Acute myeloid leukemia (AML) is a heterogeneous hematological malignancy characterized by disrupted blood cell production and function. Recent investigations have highlighted the potential of targeting glutamine metabolism as a promising therapeutic approach for AML. Asparaginases, enzymes that deplete circulating glutamine and asparagine, are approved for the treatment of acute lymphoblastic leukemia, but are also under investigation in AML, with promising results. We previously reported an elevation in plasma serine levels following treatment with Erwinia-derived asparaginase (also called crisantaspase). This led us to hypothesize that AML cells initiate the de novo serine biosynthesis pathway in response to crisantaspase treatment and that inhibiting this pathway in combination with crisantaspase would enhance AML cell death. Here we report that in AML cell lines, treatment with the clinically available crisantaspase, Rylaze, upregulates the serine biosynthesis enzymes phosphoglycerate dehydrogenase (PHGDH) and phosphoserine aminotransferase (PSAT1) through activation of the Amino Acid Response (AAR) pathway, a cellular stress response mechanism that regulates amino acid metabolism and protein synthesis under conditions of nutrient limitation. Inhibition of serine biosynthesis through CRISPR-Cas9-mediated knockout of PHGDH resulted in a ~250-fold reduction in the half-maximal inhibitory concentration (IC50) for Rylaze, indicating heightened sensitivity to crisantaspase therapy. Treatment of AML cells with a combination of Rylaze and a small molecule inhibitor of PHGDH (BI4916) revealed synergistic anti-proliferative effects in both cell lines and primary AML patient samples. Rylaze-BI4916 treatment in AML cell lines led to the inhibition of cap-dependent mRNA translation and protein synthesis, as well as a marked decrease in intracellular glutathione levels, a critical cellular antioxidant. Collectively, our results highlight the clinical potential of targeting serine biosynthesis in combination with crisantaspase as a novel therapeutic strategy for AML.

Community-engaged basic science in an NCI-designated comprehensive cancer center: antioxidants and chemotherapeutic efficacy.

PURPOSE: While community engagement has been a longstanding aspect of cancer-relevant research in social and behavioral sciences, it is far less common in basic/translational/clinical research. With the National Cancer Institute's incorporation of Community Outreach and Engagement into the Cancer Center Support Grant guidelines, successful models are desirable. We report on a pilot study supported by the University of Maryland Greenebaum Comprehensive Cancer Center (UMGCCC), that used a community-engaged, data-driven process to inform a pre-clinical study of the impact of antioxidants on the efficacy of platinum-based chemotherapeutics. METHODS: We conducted a survey of UMGCCC catchment area residents (n = 120) to identify commonly used antioxidants. We then evaluated the effect of individually combining commonly used antioxidants from the survey (vitamin C, green tea, and melatonin) with platinum agents in models of non-small cell lung cancer (A549), colon adenocarcinoma (SW620) and head and neck squamous cell carcinoma (FaDu). RESULTS: In vitro, the anti-neoplastic activity of each chemotherapy was not potentiated by any of the antioxidants. Instead, when combined at fixed ratios, most antioxidant-chemotherapy combinations were antagonistic. In vivo, addition of antioxidants did not improve chemotherapeutic efficacy and in a FaDu-tumor bearing model, cisplatin-mediated tumor growth inhibition was significantly impeded by the addition of epigallocatechin gallate, the main antioxidant in green tea. CONCLUSION: These initial findings do not support addition of antioxidant supplementation to improve platinum-based chemotherapeutic efficacy. This study's approach can serve as a model of how to bring together the two seemingly discordant areas of basic research and community engagement.

Erwinia asparaginase (crisantaspase) increases plasma levels of serine and glycine.

The impact of asparaginases on plasma asparagine and glutamine is well established. However, the effect of asparaginases, particularly those derived from Erwinia chrysanthemi (also called crisantaspase), on circulating levels of other amino acids is unknown. We examined comprehensive plasma amino acid panel measurements in healthy immunodeficient/immunocompetent mice as well as in preclinical mouse models of acute myeloid leukemia (AML) and pancreatic ductal adenocarcinoma (PDAC) using long-acting crisantaspase, and in an AML clinical study (NCT02283190) using short-acting crisantaspase. In addition to the expected decrease of plasma glutamine and asparagine, we observed a significant increase in plasma serine and glycine post-crisantaspase. In PDAC tumors, crisantaspase treatment significantly increased expression of serine biosynthesis enzymes. We then systematically reviewed clinical studies using asparaginase products to determine the extent of plasma amino acid reporting and found that only plasma levels of glutamine/glutamate and asparagine/aspartate were reported, without measuring other amino acid changes post-asparaginase. To the best of our knowledge, we are the first to report comprehensive plasma amino acid changes in mice and humans treated with asparaginase. As dysregulated serine metabolism has been implicated in tumor development, our findings offer insights into how leukemia/cancer cells may potentially overcome glutamine/asparagine restriction, which can be used to design future synergistic therapeutic approaches.

Translatome changes in acute myeloid leukemia cells post exposure to pegcrisantaspase and venetoclax.

The clinical outcomes of patients with acute myeloid leukemia (AML) treated with available therapy remain unsatisfactory. We recently reported that the BCL-2 inhibitor venetoclax synergizes with pegcrisantaspase (Ven-PegC) and exhibits remarkable in vivo efficacy in a preclinical model of AML with complex karyotype. The Ven-PegC combination blocks synthesis of proteins in AML cells by inhibiting cap-dependent translation of mRNA. To further explore the impact of Ven-PegC on protein translation, we used polysome profiling and high-throughput RNA sequencing to characterize Ven-PegC-dependent changes to the translatome. Here we report that the translation of five mRNAs, including two microRNAs, one rRNA, and two mitochondrial genes, was altered after exposure to all three treatments (Ven, PegC, and Ven-PegC). We focused our translatome validation studies on six additional genes related to translational efficiency that were modified by Ven-PegC. Notably, Ven-PegC treatment increased the RNA translation and protein levels of Tribbles homologue 3 (TRIB3), eukaryotic translation initiation factor 3 subunit C (eIF3C), doublesex and mab-3-related transcription factor 1 (DMRT1), and salt-inducible kinase 1 (SIK1). We validated the observed changes in gene/protein expression in vitro and confirmed our cell line-based studies in the bone marrow of an AML patient-derived xenograft model after Ven-PegC treatment. These results support examining alterations in the translatome post chemotherapy to offer insight into the drug's mechanism of action and to inform future therapeutic decisions.

Pre-Clinical Activity of Amino-Alcohol Dimeric Naphthoquinones as Potential Therapeutics for Acute Myeloid Leukemia.

BACKGROUND: The clinical outcomes of patients with Acute Myeloid Leukemia (AML) remain unsatisfactory. Therefore the development of more efficacious and better-tolerated therapy for AML is critical. We have previously reported anti-leukemic activity of synthetic halohydroxyl dimeric naphthoquinones (BiQ) and aziridinyl BiQ. OBJECTIVE: This study aimed to improve the potency and bioavailability of BiQ compounds and investigate antileukemic activity of the lead compound in vitro and a human AML xenograft mouse model. METHODS: We designed, synthesized, and performed structure-activity relationships of several rationally designed BiQ analogues with amino alcohol functional groups on the naphthoquinone core rings. The compounds were screened for anti-leukemic activity and the mechanism as well as in vivo tolerability and efficacy of our lead compound was investigated. RESULTS: We report that a dimeric naphthoquinone (designated BaltBiQ) demonstrated potent nanomolar anti-leukemic activity in AML cell lines. BaltBiQ treatment resulted in the generation of reactive oxygen species, induction of DNA damage, and inhibition of indoleamine dioxygenase 1. Although BaltBiQ was tolerated well in vivo, it did not significantly improve survival as a single agent, but in combination with the specific Bcl-2 inhibitor, Venetoclax, tumor growth was significantly inhibited compared to untreated mice. CONCLUSION: We synthesized a novel amino alcohol dimeric naphthoquinone, investigated its main mechanisms of action, reported its in vitro anti-AML cytotoxic activity, and showed its in vivo promising activity combined with a clinically available Bcl-2 inhibitor in a patient-derived xenograft model of AML.

Venetoclax and pegcrisantaspase for complex karyotype acute myeloid leukemia.

Complex karyotype acute myeloid leukemia (CK-AML) has a dismal outcome with current treatments, underscoring the need for new therapies. Here, we report synergistic anti-leukemic activity of the BCL-2 inhibitor venetoclax (Ven) and the asparaginase formulation Pegylated Crisantaspase (PegC) in CK-AML in vitro and in vivo. Ven-PegC combination inhibited growth of multiple AML cell lines and patient-derived primary CK-AML cells in vitro. In vivo, Ven-PegC showed potent reduction of leukemia burden and improved survival, compared with each agent alone, in a primary patient-derived CK-AML xenograft. Superiority of Ven-PegC, compared to single drugs, and, importantly, the clinically utilized Ven-azacitidine combination, was also demonstrated in vivo in CK-AML. We hypothesized that PegC-mediated plasma glutamine depletion inhibits 4EBP1 phosphorylation, decreases the expression of proteins such as MCL-1, whose translation is cap dependent, synergizing with the BCL-2 inhibitor Ven. Ven-PegC treatment decreased cellular MCL-1 protein levels in vitro by enhancing eIF4E-4EBP1 interaction on the cap-binding complex via glutamine depletion. In vivo, Ven-PegC treatment completely depleted plasma glutamine and asparagine and inhibited mRNA translation and cellular protein synthesis. Since this novel mechanistically-rationalized regimen combines two drugs already in use in acute leukemia treatment, we plan a clinical trial of the Ven-PegC combination in relapsed/refractory CK-AML.

Chimeric antigen receptor-engineered natural killer and natural killer T cells for cancer immunotherapy.

Natural killer (NK) cells of the innate immune system and natural killer T (NKT) cells, which have roles in both the innate and adaptive responses, are unique lymphocyte subsets that have similarities in their functions and phenotypes. Both cell types can rapidly respond to the presence of tumor cells and participate in immune surveillance and antitumor immune responses. This has incited interest in the development of novel cancer therapeutics based on NK and NKT cell manipulation. Chimeric antigen receptors (CARs), generated through the fusion of an antigen-binding region of a monoclonal antibody or other ligand to intracellular signaling domains, can enhance lymphocyte targeting and activation toward diverse malignancies. Most of the CAR studies have focused on their expression in T cells; however, the functional heterogeneity of CAR T cells limits their therapeutic potential and is associated with toxicity. CAR-modified NK and NKT cells are becoming more prevalent because they provide a method to direct these cells more specifically to target cancer cells, with less risk of adverse effects. This review will outline current NK and NKT cell CAR constructs and how they compare to conventional CAR T cells, and discuss future modifications that can be explored to advance adoptive cell transfer of NK and NKT cells.

Immunotherapeutic strategies targeting natural killer T cell responses in cancer.

Natural killer T (NKT) cells are a unique subset of lymphocytes that bridge the innate and adaptive immune system. NKT cells possess a classic αß T cell receptor (TCR) that is able to recognize self and foreign glycolipid antigens presented by the nonclassical class I major histocompatibility complex (MHC) molecule, CD1d. Type I NKT cells (referred to as invariant NKT cells) express a semi-invariant Vα14Jα18 TCR in mice and Vα24Jα18 TCR in humans. Type II NKT cells are CD1d-restricted T cells that express a more diverse set of TCR α chains. The two types of NKT cells often exert opposing effects especially in tumor immunity, where type II cells generally suppress tumor immunity while type I NKT cells can enhance anti-tumor immune responses. In this review, we focus on the role of NKT cells in cancer. We discuss their effector and suppressive functions, as well as describe preclinical and clinical studies utilizing therapeutic strategies focused on harnessing their potent anti-tumor effector functions, and conclude with a discussion on potential next steps for the utilization of NKT cell-targeted therapies for the treatment of cancer.

Alterations in cellular metabolism modulate CD1d-mediated NKT-cell responses.

Natural killer T (NKT) cells play a critical role in the host's innate immune response. CD1d-mediated presentation of glycolipid antigens to NKT cells has been established; however, the mechanisms by which NKT cells recognize infected or cancerous cells remain unclear. 5(')-AMP activated protein kinase (AMPK) is a master regulator of lipogenic pathways. We hypothesized that activation of AMPK during infection and malignancy could alter the repertoire of antigens presented by CD1d and serve as a danger signal to NKT cells. In this study, we examined the effect of alterations in metabolism on CD1d-mediated antigen presentation to NKT cells and found that an infection with lymphocytic choriomeningitis virus rapidly increased CD1d-mediated antigen presentation. Hypoxia inducible factors (HIF) enhance T-cell effector functions during infection, therefore antigen presenting cells pretreated with pharmacological agents that inhibit glycolysis, induce HIF and activate AMPK were assessed for their ability to induce NKT-cell responses. Pretreatment with 2-deoxyglucose, cobalt chloride, AICAR and metformin significantly enhanced CD1d-mediated NKT-cell activation. In addition, NKT cells preferentially respond to malignant B cells and B-cell lymphomas express HIF-1α. These data suggest that targeting cellular metabolism may serve as a novel means of inducing innate immune responses.

The oncolytic virus ΔPK has multimodal anti-tumor activity.

Oncolytic viruses (OVs) are an emerging cancer therapeutic, with a near complete absence of serious adverse effects. However, clinical efficacy is relatively modest, related to poor tumor penetration, failure to lyse cancer stem cells (CSCs) and blockade of immunogenic cell death by the immunosuppressive tumor microenvironment. To overcome such limitations, we developed an OV (known as ΔPK) with multimodal anti-tumor activity. ΔPK has potent anti-tumor activity both in melanoma cell lines and xenograft animal models, associated with virus replication and the induction of multiple independent programmed cell death pathways. It lyses CSCs through autophagy modulation and it reverses the immunosuppressive tumor microenvironment by altering the balance of cytokines secreted by the tumor cells. This includes decreased tumor cell secretion of the immunosuppressive and procancerous cytokines IL-10 and IL-18 and concomitant increased secretion of the proinflammatory cytokines TNF-α, GM-CSF, IL-6 and IL-1ß. ΔPK also upregulates the NKG2D ligand, MICA expressed by cytotoxic NK and T cells, and downregulates the negative immune checkpoint regulator cytotoxic T-lymphocyte antigen-4 (CTLA-4). ΔPK is well tolerated in human patients in whom it also alters the Th1/Th2 balance. Further studies are designed to elucidate the role of these contributions in different tumor types.

ΔPK oncolytic activity includes modulation of the tumour cell milieu.

Oncolytic virotherapy is a unique cancer therapeutic that encompasses tumour cell lysis through both virus replication and programmed cell death (PCD) pathways. Nonetheless, clinical efficacy is relatively modest, likely related to the immunosuppressive tumour milieu. Our studies use the herpes simplex virus type 2 (HSV-2)-based oncolytic virus ΔPK that has documented anti-tumour activity associated with virus replication, PCD and cancer stem cell lysis. They are designed to examine whether ΔPK-mediated oncolysis includes the ability to reverse the immunosuppressive tumour microenvironment by altering the balance of cytokines directly secreted by the melanoma cells and to define its mechanism. Here, we show that melanoma cells secreted the immunosuppressive cytokine IL-10, and that secretion was inhibited by ΔPK through virus replication and c-Jun N-terminal kinase/c-Jun activation. ΔPK-induced IL-10 inhibition upregulated surface expression of MHC class I chain-related protein A, the ligand for the activating NKG2D receptor expressed on NK- and cytotoxic T-cells. Concomitantly, ΔPK also upregulated the secretion of inflammatory cytokines TNF-α, granulocyte macrophage colony-stimulating factor and IL-1ß through autophagy-mediated activation of Toll-like receptor 2 pathways and pyroptosis, and it inhibited the expression of the negative immune checkpoint regulator cytotoxic T-lymphocyte antigen 4. Pharmacologic inhibition of these processes significantly reduces the oncolytic activity of ΔPK.

Valproic acid induces neuronal cell death through a novel calpain-dependent necroptosis pathway.

A growing body of evidence indicates that valproic acid (VPA), a histone deacetylase inhibitor used to treat epilepsy and mood disorders, has histone deacetylase-related and -unrelated neurotoxic activity, the mechanism of which is still poorly understood. We report that VPA induces neuronal cell death through an atypical calpain-dependent necroptosis pathway that initiates with downstream activation of c-Jun N-terminal kinase 1 (JNK1) and increased expression of receptor-interacting protein 1 (RIP-1) and is accompanied by cleavage and mitochondrial release/nuclear translocation of apoptosis-inducing factor, mitochondrial release of Smac/DIABLO, and inhibition of the anti-apoptotic protein X-linked inhibitor of apoptosis (XIAP). Coinciding with apoptosis-inducing factor nuclear translocation, VPA induces phosphorylation of the necroptosis-associated histone H2A family member H2AX, which is known to contribute to lethal DNA degradation. These signals are inhibited in neuronal cells that express constitutively activated MEK/ERK and/or PI3-K/Akt survival pathways, allowing them to resist VPA-induced cell death. The data indicate that VPA has neurotoxic activity and identify a novel calpain-dependent necroptosis pathway that includes JNK1 activation and RIP-1 expression. A growing body of evidence indicates that valproic acid (VPA) has neurotoxic activity, the mechanism of which is still poorly understood. We report, for the first time, that VPA activates a previously unrecognized calpain-dependent necroptosis cascade that initiates with JNK1 activation and involves AIF cleavage/nuclear translocation and H2AX phosphorylation as well as an altered Smac/DIABLO to XIAP balance.

CRF-amplified neuronal TLR4/MCP-1 signaling regulates alcohol self-administration.

Alcohol dependence is a complex disorder that initiates with episodes of excessive alcohol drinking known as binge drinking. It has a 50-60% risk contribution from inherited susceptibility genes; however, their exact identity and function are still poorly understood. We report that alcohol-preferring P rats have innately elevated levels of Toll-like receptor 4 (TLR4) and monocyte chemotactic protein-1 (MCP-1) that colocalize in neurons from the central nucleus of the amygdala (CeA) and ventral tegmental area (VTA). To examine the potential role of a TLR4/MCP-1 signal, we used Herpes Simplex Virus (HSV) vectors (amplicons) that retain in vivo neurotropism. Infusion of amplicons for TLR4 or MCP-1 siRNA into the CeA or VTA from the P rats inhibited target gene expression and blunted binge drinking. A similarly delivered amplicon for scrambled siRNA did not inhibit TLR4 or MCP-1 expression nor reduce binge drinking, identifying a neuronal TLR4/MCP-1 signal that regulates the initiation of voluntary alcohol self-administration. The signal was sustained during alcohol drinking by increased expression of corticotropin-releasing factor and its feedback regulation of TLR4 expression, likely contributing to the transition to alcohol dependence.