Asparagine synthetase expression and its potential prognostic value in patients with NK/T cell lymphoma

Kinetics characterization of a low immunogenic recombinant l-asparaginase from Phaseolus vulgaris with cytotoxic activity against leukemia cells

l-asparaginases play a crucial role in the treatment of acute lymphoblastic leukemia (ALL), a type of cancer that mostly affects children and teenagers. However, it is common for these molecules to cause adverse reactions during treatment. These downsides ignite the search for novel asparaginases to mitigate these problems. Thus, this work aimed to produce and characterize a recombinant asparaginase from Phaseolus vulgaris (Asp-P). In this study, Asp-P was expressed in Escherichia coli with high yields and optimum activity at 40 °C, pH 9.0. The enzyme Km and Vmax values were 7.05 mM and 1027 U/mg, respectively. Asp-P is specific for l-asparagine, showing no activity against l-glutamine and other amino acids. The enzyme showed a higher cytotoxic effect against Raji than K562 cell lines, but only at high concentrations. In silico analysis indicated that Asp-P has lower immunogenicity than a commercial enzyme. Asp-P induced biofilm formation by Candida sp. due to sublethal dose, showing an underexplored potential of asparaginases. The absence of glutaminase activity, lower immunogenicity and optimal activity similar to physiological temperature conditions are characteristics that indicate Asp-P as a potential new commercial enzyme in the treatment of ALL and its underexplored application in the treatment of other diseases.

Mitochondrial metabolism as a dynamic regulatory hub to malignant transformation and anti-cancer drug resistance

Glycolysis is the fundamental cellular process that permits cancer cells to convert energy and grow anaerobically. Recent developments in molecular biology have made it evident that mitochondrial respiration is critical to tumor growth and treatment response. As the principal organelle of cellular energy conversion, mitochondria can rapidly alter cellular metabolic processes, thereby fueling malignancies and contributing to treatment resistance. This review emphasizes the significance of mitochondrial biogenesis, turnover, DNA copy number, and mutations in bioenergetic system regulation. Tumorigenesis requires an intricate cascade of metabolic pathways that includes rewiring of the tricarboxylic acid (TCA) cycle, electron transport chain and oxidative phosphorylation, supply of intermediate metabolites of the TCA cycle through amino acids, and the interaction between mitochondria and lipid metabolism. Cancer recurrence or resistance to therapy often results from the cooperation of several cellular defense mechanisms, most of which are connected to mitochondria. Many clinical trials are underway to assess the effectiveness of inhibiting mitochondrial respiration as a potential cancer therapeutic. We aim to summarize innovative strategies and therapeutic targets by conducting a comprehensive review of recent studies on the relationship between mitochondrial metabolism, tumor development and therapeutic resistance.

Treatment of extranodal NK/T-cell lymphoma: From past to future

Extranodal NK/T-cell lymphoma (ENKTCL) is the most common subtype of T/NK-cell lymphoma in Asia and Latin America, but very rare in North American and Europe. Patient survival has improved significantly over the past two decades. However, standard treatment has not yet been established, although dozens of prospective trials have been conducted. To help understand how the treatment of ENKTCL has evolved in the past and what trends lie ahead, we have comprehensively reviewed the treatment of this aggressive malignancy, with a particular focus on neglected or unanswered issues, such as the optimal staging method, the best partner of asparaginase (Asp), the individualized administration of Asp, the preferred sequence of CT and RT and so on. Overall, the 5-year overall survival (OS) of patients with Ann Arbor stage I/II disease increased from < 50% in the early 20th century to > 80% in recent years, and the median OS of patients with Ann Arbor stage III/IV disease increased from < 1 year to more than 3 years. The improvement in patient survival is largely attributable to advances in radiation technology and the introduction of Asp and anti-PD-1/PD-L1 immunotherapy into practice. Radiotherapy is essential for patients with early-stage disease, while Asp-based chemotherapy (CT) and PD-1/PD-L1 inhibitors significantly improved the prognosis of patients with advanced-stage disease. ENKTCL management is trending toward simpler regimens, less toxicity, and higher efficacy. Novel drugs, such as manufactured T cells, monoclonal antibodies, and small molecule inhibitors, are being intensively investigated. Based on the fact that ENKTCL is highly resistant to cytotoxic drugs except Asp, and aggressive CT leads to higher toxicity rather than better outcomes, we recommend it is unnecessary to expend additional resources to compare different combinations of Asp with cytotoxic agents. Instead, more efforts should be made to optimize the use of Asp and immunotherapy to maximize efficacy and minimize toxicity, explore ways to overcome resistance to Asp and immunotherapy, identify novel treatment targets, and define subpopulations who may benefit more from specific treatments.

Consumption of meat containing ractopamine might enhance tumor growth through induction of asparagine synthetase

There is currently no evidence of the carcinogenic effect of the β-adrenergic agonist ractopamine added in finishing swine and cattle feed for promoting leanness. Nonetheless, it has the capability of stimulating expression of asparagine synthetase (ASNS) through activating transcription factor 5, and many other genes involved in the stress reaction in the skeletal muscle of pigs according to published scientific articles. Because overexpression of ASNS has been detected as a key player in amino acid response and unfolded protein response during the development of not a few malignant diseases, especially those with KRAS mutations, and found to be closely related to tumor proliferation, invasion and metastasis, it seems reasonable to hypothesize that intake of ractopamine residue in meat might bring negative effects to cancer patients.

Influence of genetic variants in asparaginase pathway on the susceptibility to asparaginase-related toxicity and patients' outcome in childhood acute lymphoblastic leukemia

BACKGROUND

Asparaginase (ASNase) is a key component in the treatment protocols of childhood acute lymphoblastic leukemia (ALL). Asparagine synthetase (ASNS) and the basic region leucine zipper activating transcription factor 5 (ATF5) mediate the anti-leukemic effect of ASNase. Only a few reports studied the association between polymorphisms in these genes and treatment-related toxicity and response. Therefore, the current study aimed to investigate the association of ASNS and ATF5 polymorphisms with the susceptibility to ASNase-related toxicity and disease outcome in a population of childhood ALL Egyptian patients.

METHODS

In this study, 88 children with ALL were enrolled and genotyped for ASNS T629A and ATF5 C362T polymorphisms using allelic discrimination assay.

RESULTS

The studied polymorphisms did not associate with hypersensitivity or thrombosis, while the ATF5 C362T polymorphism was associated significantly with decreased ASNase-associated pancreatitis (AAP) risk under the dominant model. Patients carrying TT/CT genotypes of ATF5 C362T polymorphism had a significantly better overall survival (OS) and longer event-free survival (EFS) compared to patients with CC genotype. Multivariate analysis confirmed the independent prognostic value of the ATF5 C362T dominant model.

CONCLUSION

ATF5 362TT and CT genotypes were associated with decreased risk to develop AAP and better disease outcome demonstrating a low risk for events and superior survival.

Investigating the gut microbial community and genes in children with differing levels of change in serum asparaginase activity during pegaspargase treatment for acute lymphoblastic leukemia

Asparaginase (ASNase) is an effective treatment of pediatric acute lymphoblastic leukemia (ALL). Changes in ASNase activity may lead to suboptimal treatment and poorer outcomes. The gut microbiome produces metabolites that could impact ASNase therapy, however, remains uninvestigated. We examined gut-microbial community and microbial-ASNase and asparagine synthetase (ASNS) genes using 16SrRNA and metagenomic sequence data from stool samples of pediatric ALL patients. Comparing ASNase activity between consecutive ASNase-doses, we found microbial communities differed between decreased- and increased-activity samples. Escherichia predominated in the decreased-activity community while Bacteroides and Streptococcus predominated in the increased-activity community. In addition microbial ASNS was significantly (p=.004) negatively correlated with change in serum ASNase activity. These preliminary findings suggest microbial communities prior to treatment could affect serum ASNase levels, although the mechanism is unknown. Replication in an independent cohort is needed, and future research on manipulation of these communities and genes could prove useful in optimizing ASNase therapy.

Study of L-Asparaginase, Vincristine, and Dexamethasone Combined With Intensity-modulated Radiation Therapy in Early-Stage Nasal NK/T-Cell Lymphoma

OBJECTIVES

Natural killer/T-cell lymphoma (NKTCL) is aggressive, and carries a poor prognosis worldwide. This retrospective study aimed to evaluate the clinical efficacy and safety of the LVD regimen (L-asparaginase, vincristine, and dexamethasone) combined with intensity-modulated radiation therapy (IMRT) for the treatment of early-stage nasal NKTCL in a Chinese population.

METHODS

The clinical data were collected from patients treated between March 2010 and January 2017. Patients received LVD chemotherapy combined with IMRT, and were followed for 30 to 90 months. All received radiotherapy at the end of the first/second cycle of chemotherapy. The survival curves were generated by the Kaplan-Meier method.

RESULTS

Among 94 patients who received 2 to 6 cycles (mean, 4 cycles) of treatments, 56 and 25 achieved complete and partial remission, respectively; 2 and 11 experienced stable disease and progressive disease. The overall objective response was 86.2%. Patients with elevated lactate dehydrogenase and skin invasion had a lower objective response rate. The progression-free survival rates at 1, 3, and 5 years were 90.3%, 73.5%, and 71.3%; the corresponding overall survival rates were 91.4%, 74.3%, and 74.3%. The main adverse events were myelosuppression (63.8% grades I to II, 12.8% grade III), gastrointestinal symptoms (63.8% grades I to II), hepatic lesion (55.3% grades I to II), hypoproteinemia (46.8% grades I to II), skin allergies (77.7% grades I to II, 3.2% grade III), and oral mucosal lesions (44.7% grades I to II, 33% grade III). No severe pancreatitis, anaphylaxis, or toxicity-related death was observed.

CONCLUSION

In patients with early-stage nasal NKTCL, our LVD-IMRT regimen produced excellent, durable therapeutic benefit in most patients, with acceptable toxicity and no acute mortality.

The landscape of new drugs in extranodal NK/T-cell lymphoma

To date, much progress has been made in early-stage extranodal NK/T-cell lymphoma (ENKTCL), and risk-adapted therapy with radiotherapy (RT) alone for the low-risk group and RT combined with asparaginase-based chemotherapy (CT) for the high-risk group yields favorable outcomes. However, optimal treatment strategies have not been defined yet for advanced-stage ENKTCL. Historically, ENKTCL responded poorly to conventional anthracycline-based chemotherapy probably because of inherent multidrug resistance (MDR). The fact that ENKTCL cells lack asparagine synthetase (ASNS) activity warranted the use of L-asparaginase or pegaspargase as frontline chemotherapies. Even though, due to high mortality of the disease, approximately 50% patients failing the frontline therapy arrived at dismal clinical outcomes with a median progression-free survival (PFS) less than 8 months. As distinctive molecular and biological subgroups are increasingly discovered within the disease entity of ENKTCL, novel targeted therapies and immunotherapy are of the urgent need for those heterogeneous subgroups. In this review, we sought to summarize the preclinical and clinical results of 6 categories of promising targeted therapy and immunotherapy for the treatment of ENKTCL, including monoclonal antibodies, immune checkpoint inhibitors, small-molecular inhibitors, epigenetic therapy, immunomodulatory drugs, and adoptive T-cell therapy, and these might change the landscape of treatment for ENKTCL in the near future.

Epigenetic aberrations in natural killer/T-cell lymphoma: diagnostic, prognostic and therapeutic implications

Natural killer/T-cell lymphoma (NKTCL) is an aggressive malignancy that usually presents in the upper aerodigestive tract. This malignancy shows substantial geographic variability in incidence, and is characterized by Epstein-Barr virus (EBV) infections. Epigenetic aberrations may dysregulate the expression of genes involved in different hallmarks of cancer. A growing body of evidence underscores the importance of epigenetic aberrations in the pathogenesis of NKTCL. Promoter hypermethylation is a common epigenetic mechanism for the inactivation of tumour suppressor genes. Several epigenetically silenced tumour suppressor candidates (e.g. PRDM1, BIM) were identified in this aggressive cancer using locus-specific and genome-wide promoter methylation analyses. Importantly, genes involved in epigenetic modifications were identified to be mutated (e.g. KMT2D) or methylated (e.g. TET2) in NKTCL patients, which may contribute to pathogenesis through global alterations in chromatin states. Cancer-associated microRNAs, some of which are expressed by EBV, and long noncoding RNAs have been observed to be dysregulated in NKTCL. This review focuses on studies investigating epigenetic aberrations in NKTCL to bolster our overall understanding of the role of these abnormalities in disease pathobiology. We also discuss the potential of these epigenetic aberrations to improve diagnosis and prognosis as well as reveal novel targets of therapy for NKTCL.

Asparagine Synthetase in Cancer: Beyond Acute Lymphoblastic Leukemia

Asparagine Synthetase (ASNS) catalyzes the synthesis of the non-essential amino acid asparagine (Asn) from aspartate (Asp) and glutamine (Gln). ASNS expression is highly regulated at the transcriptional level, being induced by both the Amino Acid Response (AAR) and the Unfolded Protein Response (UPR) pathways. Lack of ASNS protein expression is a hallmark of Acute Lymphoblastic Leukemia (ALL) blasts, which, therefore, are auxotrophic for Asn. This peculiarity is the rationale for the use of bacterial L-Asparaginase (ASNase) for ALL therapy, the first example of anti-cancer treatment targeting a tumor-specific metabolic feature. Other hematological and solid cancers express low levels of ASNS and, therefore, should also be Asn auxotrophs and ASNase sensitive. Conversely, in the last few years, several reports indicate that in some cancer types ASNS is overexpressed, promoting cell proliferation, chemoresistance, and a metastatic behavior. However, enhanced ASNS activity may constitute a metabolic vulnerability in selected cancer models, suggesting a variable and tumor-specific role of the enzyme in cancer. Recent evidence indicates that, beyond its canonical role in protein synthesis, Asn may have additional regulatory functions. These observations prompt a re-appreciation of ASNS activity in the biology of normal and cancer tissues, with particular attention to the fueling of Asn exchange between cancer cells and the tumor microenvironment.

Asparagine synthetase expression is associated with the sensitivity to asparaginase in extranodal natural killer/T-cell lymphoma in vivo and in vitro

Background

Although asparagine synthetase (AsnS) is associated with drug resistance in leukemia, its function in extranodal natural killer (NK)/T-cell lymphoma (ENKTL) remains unclear.

Methods

The present study investigated the relationship between baseline AsnS mRNA levels and response to asparaginase in ENKTL cell lines. It also determined whether upregulating or downregulating the AsnS mRNA level induces or reverses asparaginase-resistant phenotype.

Results

Interestingly, considerable differences were observed in the sensitivity to asparaginase of the five ENKTL cell lines. The AsnS expression levels were positively correlated with the IC₅₀ values. In addition, the asparaginase resistance was induced or reversed by upregulating or downregulating the AsnS mRNA level in vivo and in vitro. Functional analyses indicated that AsnS did not affect the proliferation and apoptosis of ENKTL cells in the absence of asparaginase.

Conclusion

Together, the data stress the importance of AsnS in the sensitivity to asparaginase in ENKTL and suggest a different therapeutic strategy for patients with a different level of AsnS expression.

PEG-L-CHOP treatment is safe and effective in adult extranodal NK/T-cell lymphoma with a low rate of clinical hypersensitivity

Background

The combination of chemotherapy and L-asparaginase (L-ASP) treatment significantly increased survival rate in an adult patient with extranodal natural killer (NK)/T-cell lymphoma (NKTCL). However, hypersensitivity reactions of L-ASP in some patients limited its application. Polyethylene glycol-conjugated asparaginase (PEG-ASP) has a lower immunogenicity and longer circulating half-life than unconjugated L-ASP, and has been reported to be effective and well-tolerated in children with acute lymphoblastic leukemia. Cyclophosphamide, hydroxydaunorubicin (doxorubicin), oncovin (vincristine), and prednisolone (CHOP) is the most common chemotherapy for non-Hodgkin lymphoma. In this report, we sought to study the efficacy and safety of PEG-L- CHOP in NKTCL in adult Chinese patients.

Methods

Our study is a prospective, multi-center, open-label clinical trial. Patients with newly diagnosed adult NKTCL and an ECOG performance status of 0 to 2 were eligible for enrollment. Treatment included six cycles of PEG-L-CHOP regimen. Radiotherapy was scheduled after 2–4 cycles of PEG-L-CHOP regimen, depending on the stage and primary anatomic site.

Results

We enrolled a total of 33 eligible patients. All 33 patients completed 170 cycles of chemotherapy combined with radical radiotherapy. The overall response rate was 96.9% (32/33) with 75.8% (25/33) achieving complete responses and 21.2% (7/33) achieving partial responses. The overall survival (OS) at 1, 2, 3-year were 100, 90.61 and 80.54%, respectively. The major adverse effects were bone marrow suppression, reduction of fibrinogen level, liver dysfunction, and digestive tract toxicities. No allergic reaction and no treatment-related mortality or severe complications were recorded.

Conclusions

PEG-L-CHOP chemotherapy in combination radiotherapy is safe and durably effective treatment for adult extranodal NK/T-cell lymphoma with fewer allergic reactions.

This study was approved by the Peking University Beijing Cancer Hospital Ethics Review Committee (reference number: 2011101104). The clinical trial registration number ChiCTR1800016940 was registered on July 07, 2018 at the Chinese Clinical Trial Registry (http://www.chictr.org.cn/index.aspx). The clinical trial was registered retrospectively.

Novel Immunotherapy Options for Extranodal NK/T-Cell Lymphoma

Extranodal NK/T-cell lymphoma (ENKTCL) is a highly aggressive mature NK/T-cell neoplasm marked by NK-cell phenotypic expression of CD3ε and CD56. While the disease is reported worldwide, there is a significant geographic variation with its highest incidence in East Asian countries possibly related to the frequent early childhood exposure of Epstein-Barr virus (EBV) and specific ethnic-genetical background, which contributes to the tumorigenesis. Historically, anthracycline-based chemotherapy such as CHOP (cyclophosphamide, adriamycin, vincristine, and prednisone) was used, but resulted in poor outcomes. This is due in part to intrinsic ENKTCL resistance to anthracycline caused by high expression levels of P-glycoprotein. The recent application of combined modality therapy with concurrent or sequential radiation therapy for early stage disease, along with non-anthracycline-based chemotherapy regimens consisting of drugs independent of P-glycoprotein have significantly improved clinical outcomes. Particularly, this neoplasm shows high sensitivity to l-asparaginase as NK-cells lack asparagine synthase activity. Even still, outcomes of patients with advanced stage disease or those with relapsed/recurrent disease are dismal with overall survival of generally a few months. Thus, novel therapies are needed for this population. Clinical activity of targeted antibodies along with antibody-drug conjugates, such as daratumumab (naked anti-CD38 antibody) and brentuximab vedotin (anti-CD30 antibody conjugated with auristatin E), have been reported. Further promising data have been shown with checkpoint inhibitors as high levels of programmed death-ligand 1 expression are observed in ENKTCL due to EBV-driven overexpression of the latent membrane proteins [latent membrane protein 1 (LMP1) and LMP2] with activation of the NF-κB/MAPK pathways. Initial case series with programmed death 1 inhibitors showed an overall response rate of 100% in seven relapsed patients including five with a complete response (CR). Furthermore, cellular immunotherapy with engineered cytotoxic T lymphocytes targeted against LMP1 and LMP2 have shown encouraging results with durable CRs as either maintenance therapy after initial induction chemotherapy or in the relapsed/refractory setting. In this paper, we review this exciting field of novel immunotherapy options against ENKTCL that hopefully will change the treatment paradigm in this deadly disease.