Hepatocellular Carcinoma: Old and Emerging Therapeutic Targets

Liver cancer, predominantly hepatocellular carcinoma (HCC), globally ranks sixth in incidence and third in cancer-related deaths. HCC risk factors include non-viral hepatitis, alcohol abuse, environmental exposures, and genetic factors. No specific genetic alterations are unequivocally linked to HCC tumorigenesis. Current standard therapies include surgical options, systemic chemotherapy, and kinase inhibitors, like sorafenib and regorafenib. Immunotherapy, targeting immune checkpoints, represents a promising avenue. FDA-approved checkpoint inhibitors, such as atezolizumab and pembrolizumab, show efficacy, and combination therapies enhance clinical responses. Despite this, the treatment of hepatocellular carcinoma (HCC) remains a challenge, as the complex tumor ecosystem and the immunosuppressive microenvironment associated with it hamper the efficacy of the available therapeutic approaches. This review explores current and advanced approaches to treat HCC, considering both known and new potential targets, especially derived from proteomic analysis, which is today considered as the most promising approach. Exploring novel strategies, this review discusses antibody drug conjugates (ADCs), chimeric antigen receptor T-cell therapy (CAR-T), and engineered antibodies. It then reports a systematic analysis of the main ligand/receptor pairs and molecular pathways reported to be overexpressed in tumor cells, highlighting their potential and limitations. Finally, it discusses TGFβ, one of the most promising targets of the HCC microenvironment.

Identification and structural characterization of a pathogenic ARSA missense variant in two consanguineous families from Jammu and Kashmir (India) with late infantile metachromatic leukodystrophy

BACKGROUND

Metachromatic leukodystrophy (MLD) is a rare lysosomal storage disorder caused by a deficiency of Arylsulfatase A (ARSA) enzyme activity. Its clinical manifestations include progressive motor and cognitive decline. ARSA gene mutations are frequent in MLD.

METHODS AND RESULTS

In the present study, whole exome sequencing (WES) was employed to decipher the genetic cause of motor and cognitive decline in proband's of two consanguineous families from J&K (India). Clinical investigations using radiological and biochemical analysis revealed MLD-like features. WES confirmed a pathogenic variant in the ARSA gene. Molecular simulation dynamics was applied for structural characterization of the variant.

CONCLUSION

We report the identification of a pathogenic missense variant (c.1174 C > T; p.Arg390Trp) in the ARSA gene in two cases of late infantile MLD from consanguineous families in Jammu and Kashmir, India. Our study utilized genetic analysis and molecular dynamics simulations to identify and investigate the structural consequences of this mutation. The molecular dynamics simulations revealed significant alterations in the structural dynamics, residue interactions, and stability of the ARSA protein harbouring the p.Arg390Trp mutation. These findings provide valuable insights into the molecular mechanisms underlying the pathogenicity of this variant in MLD.

Polyacrylic-Coated Solid Nanoparticles Increase the Aquaporin Permeability to Hydrogen Peroxide

Aquaporins (AQPs) allow the diffusion of hydrogen peroxide (H2O2) and act as ROS scavenging systems, which are important for controlling the redox state of cells. Recently, cerium oxide nanoparticles were found to increase the water and H2O2 permeability by modulating AQPs. To further analyze the action of nanoparticles (NPs) on AQP, we examined the effect of the NPs presenting different core compositions (CeO2, Gd2O3, Fe3O4, and TiO2), hydrodynamic sizes, and surface functionalization. The NPs produced an increase in H2O and H2O2 permeability as a general trend. The hydrodynamic sizes of the NPs in the range of 22-100 nm did not produce any significant effect. The chemical nature of the NPs' core did not modify the effect and its intensity. On the other hand, the NPs' functionalized surface plays a major role in influencing both water and H2O2 permeability. The results suggest that NPs can play a significant role in controlling oxidative stress in cells and might represent an innovative approach in the treatment of a number of pathologies associated with an increased oxidative status.

Asparagine and Glutamine Deprivation Alters Ionizing Radiation Response, Migration and Adhesion of a p53null Colorectal Cancer Cell Line

Colorectal cancer (CRC) is the most prominent form of colon cancer for both incidence (38.7 per 100,000 people) and mortality (13.9 per 100,000 people). CRC's poor response to standard therapies is linked to its high heterogeneity and complex genetic background. Dysregulation or depletion of the tumor suppressor p53 is involved in CRC transformation and its capability to escape therapy, with p53^null cancer subtypes known, in fact, to have a poor prognosis. In such a context, new therapeutic approaches aimed at reducing CRC proliferation must be investigated. In clinical practice, CRC chemotherapy is often combined with radiation therapy with the aim of blocking the expansion of the tumor mass or removing residual cancer cells, though contemporary targeting of amino acid metabolism has not yet been explored. In the present study, we used the p53^null Caco-2 model cell line to evaluate the effect of a possible combination of radiation and L-Asparaginase (L-ASNase), a protein drug that blocks cancer proliferation by impairing asparagine and glutamine extracellular supply. When L-ASNase was administered immediately after IR, we observed a reduced proliferative capability, a delay in DNA-damage response and a reduced capability to adhere and migrate. Our data suggest that a correctly timed combination of X-rays and L-ASNase treatment could represent an advantage in CRC therapy.

Side-by-Side Comparison of uPAR-Targeting Optical Imaging Antibodies and Antibody Fragments for Fluorescence-Guided Surgery of Solid Tumors

PURPOSE

Radical resection is paramount for curative oncological surgery. Fluorescence-guided surgery (FGS) aids in intraoperative identification of tumor-positive resection margins. This study aims to assess the feasibility of urokinase plasminogen activator receptor (uPAR) targeting antibody fragments for FGS in a direct comparison with their parent IgG in various relevant in vivo models.

PROCEDURES

Humanized anti-uPAR monoclonal antibody MNPR-101 (uIgG) was proteolytically digested into F(ab')2 and Fab fragments named uFab2 and uFab. Surface plasmon resonance (SPR) and cell assays were used to determine in vitro binding before and after fluorescent labeling with IRDye800CW. Mice bearing subcutaneous HT-29 human colonic cancer cells were imaged serially for up to 120 h after fluorescent tracer administration. Imaging characteristics and ex vivo organ biodistribution were further compared in orthotopic pancreatic ductal adenocarcinoma (BxPc-3-luc2), head-and-neck squamous cell carcinoma (OSC-19-luc2-GFP), and peritoneal carcinomatosis (HT29-luc2) models using the clinical Artemis fluorescence imaging system.

RESULTS

Unconjugated and conjugated uIgG, uFab2, and uFab specifically recognized uPAR in the nanomolar range as determined by SPR and cell assays. Subcutaneous tumors were clearly identifiable with tumor-to-background ratios (TBRs) > 2 after 72 h for uIgG-800F and 24 h for uFab2-800F and uFab-800F. For the latter two, mean fluorescence intensities (MFIs) dipped below predetermined threshold after 72 h and 36 h, respectively. Tumors were easily identified in the orthotopic models with uIgG-800F consistently having the highest MFIs and uFab2-800F and uFab-800F having similar values. In biodistribution studies, kidney and liver fluorescence approached tumor fluorescence after uIgG-800F administration and surpassed tumor fluorescence after uFab2-800F or uFab-800F administration, resulting in interference in the abdominal orthotopic mouse models.

CONCLUSIONS

In a side-by-side comparison, FGS with uPAR-targeting antibody fragments compared with the parent IgG resulted in earlier tumor visualization at the expense of peak fluorescence intensity.

Case Report: Heterozygous Germline Variant in EIF6 Additional to Biallelic SBDS Pathogenic Variants in a Patient With Ribosomopathy Shwachman–Diamond Syndrome

Background: Shwachman–Diamond syndrome (SDS) is a rare autosomal recessive ribosomopathy mainly characterized by exocrine pancreatic insufficiency, skeletal alterations, neutropenia, and a relevant risk of hematological transformation. At least 90% of SDS patients have pathogenic variants in SBDS, the first gene associated with the disease with very low allelic heterogeneity; three variants, derived from events of genetic conversion between SBDS and its pseudogene, SBDSP1, provided the alleles observed in about 62% of SDS patients.

Methods: We performed a reanalysis of the available WES files of a group of SDS patients with biallelic SBDS pathogenic variants, studying the results by next bioinformatic and protein structural analysis. Parallelly, careful clinical attention was given to the patient focused in this study.

Results: We found and confirmed in one SDS patient a germline heterozygous missense variant (c.100T>C; p.Phe34Leu) in the EIF6 gene. This variant, inherited from his mother, has a very low frequency, and it is predicted as pathogenic, according to several in silico prediction tools. The protein structural analysis also envisages the variant could reduce the binding to the nascent 60S ribosomal.

Conclusion: This study focused on the hypothesis that the EIF6 germline variant mimics the effect of somatic deletions of chromosome 20, always including the locus of this gene, and similarly may rescue the ribosomal stress and ribosomal dysfunction due to SBDS mutations. It is likely that this rescue may contribute to the stable and not severe hematological status of the proband, but a definite answer on the role of this EIF6 variant can be obtained only by adding a functional layer of evidence. In the future, these results are likely to be useful for selected cases in personalized medicine and therapy.

Hereditary hemorrhagic telangiectasia: First demonstration of a founder effect in Italy; the ACVRL1 c.289_294del variant originated in the country of Bergamo 200 years ago

Background

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular disorder, affecting 1:5000 individuals worldwide. All the genes associated to the disease (ENG, ACVRL1, SMAD4, GDF2) belong to the TGF‐β/BMPs signaling pathway.

We found 19 HHT unrelated families, coming from a Northern Italy region and sharing the ACVRL1 in‐frame deletion c.289_294del (p.H97_N98).

Methods

To test the hypothesis of a founder effect, we analyzed 88 subjects from 19 families (66 variant carriers, showing clinical signs of HHT, and 22 non‐carriers, unaffected) using eight microsatellite markers within 3.7 Mb around the ACVRL1 locus. After the haplotype reconstruction, age estimation of the variant was carried out.

Results

We observed a common disease haplotype in 16/19 families, while three families showed evidence of recombination around the ACVRL1 locus. The subsequent age estimation analyses suggested that the mutation occurred about 8 generations ago, corresponding to about 200 years ago. We also present novel in silico and modeling data supporting the variant pathogenicity: the deletion alters the protein stability and removes the unique extracellular glycosylation site.

Conclusion

We have demonstrated, for the first time, a “founder effect” for a HHT pathogenic variant in Italy.

Structural Aspects of E. coli Type II Asparaginase in Complex with Its Secondary Product L-Glutamate

Bacterial L-asparaginases are amidohydrolases (EC 3.5.1.1) capable of deaminating L-asparagine and, with reduced efficiency, L-glutamine. Interest in the study of L-asparaginases is driven by their use as biodrugs for the treatment of acute lymphoblastic leukemia. Here, we report for the first time the description of the molecular structure of type II asparaginase from Escherichia coli in complex with its secondary product, L-glutamate. To obtain high-quality crystals, we took advantage of the N24S variant, which has structural and functional features similar to the wild-type enzyme, but improved stability, and which yields more ordered crystals. Analysis of the structure of the N24S-L-glutamate complex (N24S-GLU) and comparison with its apo and L-aspartate-bound form confirmed that the enzyme-reduced catalytic efficiency in the presence of L-glutamine is due to L-glutamine misfitting into the enzyme-binding pocket, which causes a local change in the catalytic center geometry. Moreover, a tight interaction between the two protomers that form the enzyme active site limits the capability of L-glutamine to fit into (and to exit from) the binding pocket of E. coli L-asparaginase, explaining why the enzyme has lower glutaminolytic activity compared to other enzymes of the same family, in particular the Erwinia chrysanthemi one.

Interfacial Activity of Lipoprotein (a) Isoforms with a Variable Number of Kringle IV Type 2 Repeats: A New Indicator of Cardiovascular Risk?

OBJECTIVE

Lipoprotein (a) [Lp(a)] is an LDL-like particle constituted by lipids, apolipoprotein B100 and apolipoprotein (a) [apo(a)], a multidomain glycoprotein whose molecular mass is dependent on the genetically encoded number of Kringle IV type 2 (KIV-2) repeats. Because Lp(a) isoforms have been associated with cardiovascular risk (CVR), we have investigated if their interfacial properties can contribute to distinguish between low and high-risk groups and thus be used as a new CVR indicator.

METHODS

Four Lp(a) variants, each carrying a different apo(a) isoform (K20, K24, K25, and K29), were purified from plasma of homozygous donors and their interfacial properties characterized using ellipsometry and surface pressure techniques.

RESULTS

Ellipsometry measurements revealed that these isoforms had a similar propensity to form adsorbed layers at hydrophobic-hydrophilic interfaces, but surface pressure enabled to clearly separate them into two groups: K20 and K24 on one side, and K25 and K29 on the other side.

CONCLUSION

Though K24 and K25 differ only by a single KIV-2 domain, their sharp difference in surface pressure suggests a critical threshold between the two Lp(a) forms, providing insights into the use of condensed matter approaches to monitor CVR. Our findings may represent a new laboratory window to assist medical decisions and to develop precision medicine treatments, practices, and products for CVR, which can be extended to other cardiovascular disease conditions.

LANCL1 binds abscisic acid and stimulates glucose transport and mitochondrial respiration in muscle cells via the AMPK/PGC-1α/Sirt1 pathway

OBJECTIVE

Abscisic acid (ABA) is a plant hormone also present and active in animals. In mammals, ABA regulates blood glucose levels by stimulating insulin-independent glucose uptake and metabolism in adipocytes and myocytes through its receptor LANCL2. The objective of this study was to investigate whether another member of the LANCL protein family, LANCL1, also behaves as an ABA receptor and, if so, which functional effects are mediated by LANCL1.

METHODS

ABA binding to human recombinant LANCL1 was explored by equilibrium-binding experiments with [3H]ABA, circular dichroism, and surface plasmon resonance. Rat L6 myoblasts overexpressing either LANCL1 or LANCL2, or silenced for the expression of both proteins, were used to investigate the basal and ABA-stimulated transport of a fluorescent glucose analog (NBDG) and the signaling pathway downstream of the LANCL proteins using Western blot and qPCR analysis. Finally, glucose tolerance and sensitivity to ABA were compared in LANCL2-/- and wild-type (WT) siblings.

RESULTS

Human recombinant LANCL1 binds ABA with a Kd between 1 and 10 μM, depending on the assay (i.e., in a concentration range that lies between the low and high-affinity ABA binding sites of LANCL2). In L6 myoblasts, LANCL1 and LANCL2 similarly, i) stimulate both basal and ABA-triggered NBDG uptake (4-fold), ii) activate the transcription and protein expression of the glucose transporters GLUT4 and GLUT1 (4-6-fold) and the signaling proteins AMPK/PGC-1α/Sirt1 (2-fold), iii) stimulate mitochondrial respiration (5-fold) and the expression of the skeletal muscle (SM) uncoupling proteins sarcolipin (3-fold) and UCP3 (12-fold). LANCL2-/- mice have a reduced glucose tolerance compared to WT. They spontaneously overexpress LANCL1 in the SM and respond to chronic ABA treatment (1 μg/kg body weight/day) with an improved glycemia response to glucose load and an increased SM transcription of GLUT4 and GLUT1 (20-fold) of the AMPK/PGC-1α/Sirt1 pathway and sarcolipin, UCP3, and NAMPT (4- to 6-fold).

CONCLUSIONS

LANCL1 behaves as an ABA receptor with a somewhat lower affinity for ABA than LANCL2 but with overlapping effector functions: stimulating glucose uptake and the expression of muscle glucose transporters and mitochondrial uncoupling and respiration via the AMPK/PGC-1α/Sirt1 pathway. Receptor redundancy may have been advantageous in animal evolution, given the role of the ABA/LANCL system in the insulin-independent stimulation of cell glucose uptake and energy metabolism.

POS0277 ANABOLIC EFFECT OF LNA043, A NOVEL DISEASE-MODIFYING OSTEOARTHRITIS DRUG CANDIDATE: RESULTS FROM AN IMAGING-BASED PROOF-OF-CONCEPT TRIAL IN PATIENTS WITH FOCAL ARTICULAR CARTILAGE LESIONS

Background:

LNA043 is a modified, recombinant version of the human angiopoietin-like 3 (ANGPTL3) protein acting directly on cartilage-resident cells to transmit its cartilage anabolic effect. A first-in-human study previously demonstrated the favourable safety profile and the modulation of several pathways involved in cartilage homeostasis and osteoarthritis (OA)1. A previous proof-of-mechanism imaging study used high field (7 Tesla) magnetic resonance imaging (MRI) to show formation of hyaline-like tissue after a single injection of 20 mg LNA043 (unpublished data).

Objectives:

To evaluate non-invasively the chondro-regenerative capacity of multiple intra-articular (i.a.) injections of LNA043 in patients with articular cartilage lesions in the knee (NCT03275064).

Methods:

This was a randomised, double-blind, placebo (PBO)-controlled, proof-of-concept study in patients with a partial thickness cartilage lesion. In total, 58 patients (43 [20 mg LNA043]; 15 [PBO]), stratified by lesion type (condylar or patellar) were treated with 4 weekly i.a. injections. The primary endpoint was T2 relaxation time measurement as a marker of collagen fiber network, and cartilage lesion-volume was a secondary endpoint, both using 3-Tesla MRI. Assessments were performed at baseline, weeks (wks) 8, 16, 28 and 52 (the latter in 23/58 patients). While lesion-volume for the secondary endpoint was determined from manually segmented images, the cartilage volume of 21 sub-regions spanning the entire knee was also measured from 3D isotropic MR images employing an automated segmentation prototype software (MR Chondral Health 2.1 [MRCH], Siemens Healthcare)2. An exploratory analysis evaluated the treatment effect for the additive volume of the 3 subregions in the weight-bearing area of the medial femur.

Results:

No change in T2 relaxation time was detected between treatment and PBO groups. Manual segmentation showed continuous filling of the cartilage lesions up to wk 28 in LNA043-treated patients with femoral lesions (p=0.08, vs PBO) while no effect was detected for patients with patellar lesions. Given the limitations of measuring small, irregularly shaped lesions with manual image-analysis, the MRCH approach was used (Figure 1). In the medial femoral weight-bearing region, refilling was detected over time (Δ=123 mm3 at wk 28, N= 37, p= 0.05). No overgrowth was detected in the lateral femoral condyles without cartilage damage. The overall safety profile was favourable; only mild/moderate local reactions were reported, including a higher incidence of joint swelling (9.3% vs 0%) and arthralgia (11.6% vs 6.7%) for LNA043 vs PBO resolving spontaneously or with paracetamol/NSAIDs. No anti-drug antibodies were detected.

Conclusion:

Treatment with 4 weekly i.a. injections of 20 mg LNA043 resulted in regeneration of damaged cartilage in patients with femoral articular cartilage lesions. Automated measurement of cartilage volume in the femoral index region was able to detect a relevant treatment effect and was found to be more sensitive than the manual segmentation method. No sign of cartilage overgrowth was observed in healthy femoral regions. A Phase 2b study in patients with mild to moderate knee OA is in preparation.

References:

[1]Scotti et al. ACR Convergence 2020; Abstract #1483

[2]Juras et al. Cartilage 2020; Sep 29:1-12

Disclosure of Interests:

Siegfried Trattnig: None declared, Celeste Scotti Shareholder of: Novartis, Employee of: Novartis, Didier Laurent Shareholder of: Novartis, Employee of: Novartis, Vladimir Juras: None declared, Scott Hacker Grant/research support from: Novartis, Brian Cole: None declared, Libor Pasa: None declared, Roman Lehovec: None declared, Pavol Szomolanyi: None declared, Esther Raithel Employee of: Siemens Healthcare GmbH, Franziska Saxer Shareholder of: Novartis, Employee of: Novartis, Jens Praestgaard Shareholder of: Novartis, Employee of: Novartis, Fabiola La Gamba Shareholder of: Novartis, Employee of: Novartis, José L. Jiménez Employee of: Novartis, David Sanchez Ramos Shareholder of: Novartis, Employee of: Novartis, Ronenn Roubenoff Shareholder of: Novartis, Employee of: Novartis, Matthias Schieker Shareholder of: Novartis, Employee of: Novartis

Anti-Cancer Auto-Antibodies: Roles, Applications and Open Issues

Auto-antibodies are classically associated with autoimmune diseases, where they are an integral part of diagnostic panels. However, recent evidence is accumulating on the presence of auto-antibodies against single or selected panels of auto-antigens in many types of cancer. Auto-antibodies might initially represent an epiphenomenon derived from the inflammatory environment induced by the tumor. However, their effect on tumor evolution can be crucial, as is discussed in this paper. It has been demonstrated that some of these auto-antibodies can be used for early detection and cancer staging, as well as for monitoring of cancer regression during treatment and follow up. Interestingly, certain auto-antibodies were found to promote cancer progression and metastasis, while others contribute to the body's defense against it. Moreover, auto-antibodies are of a polyclonal nature, which means that often several antibodies are involved in the response to a single tumor antigen. Dissection of these antibody specificities is now possible, allowing their identification at the genetic, structural, and epitope levels. In this review, we report the evidence available on the presence of auto-antibodies in the main cancer types and discuss some of the open issues that still need to be addressed by the research community.

In Silico Identification of SOX1 Post-Translational Modifications Highlights a Shared Protein Motif

The transcription factor SOX1 is a key regulator of neural stem cell development, acting to keep neural stem cells (NSCs) in an undifferentiated state. Postnatal expression of Sox1 is typically confined to the central nervous system (CNS), however, its expression in non-neural tissues has recently been implicated in tumorigenesis. The mechanism through which SOX1 may exert its function is not fully understood, and studies have mainly focused on changes in SOX1 expression at a transcriptional level, while its post-translational regulation remains undetermined. To investigate this, data were extracted from different publicly available databases and analysed to search for putative SOX1 post-translational modifications (PTMs). Results were compared to PTMs associated with SOX2 in order to identify potentially key PTM motifs common to these SOXB1 proteins, and mapped on SOX1 domain structural models. This approach identified several putative acetylation, phosphorylation, glycosylation and sumoylation sites within known functional domains of SOX1. In particular, a novel SOXB1 motif (xKSExSxxP) was identified within the SOX1 protein, which was also found in other unrelated proteins, most of which were transcription factors. These results also highlighted potential phospho-sumoyl switches within this SOXB1 motif identified in SOX1, which could regulate its transcriptional activity. This analysis indicates different types of PTMs within SOX1, which may influence its regulatory role as a transcription factor, by bringing changes to its DNA binding capacities and its interactions with partner proteins. These results provide new research avenues for future investigations on the mechanisms regulating SOX1 activity, which could inform its roles in the contexts of neural stem cell development and cancer.

High resolution structure of human apolipoprotein (a) kringle IV type 2: beyond the lysine binding site

Lipoprotein (a) [Lp(a)] is characterized by an LDL-like composition in terms of lipids and apoB100, and by one copy of a unique glycoprotein, apo(a). The apo(a) structure is mainly based on the repetition of tandem kringle domains with high homology to plasminogen kringles 4 and 5. Among them, kringle IV type 2 (KIV-2) is present in a highly variable number of genetically encoded repeats, whose length is inversely related to Lp(a) plasma concentration and cardiovascular risk. Despite it being the major component of apo(a), the actual function of KIV-2 is still unclear. Here, we describe the first high-resolution crystallographic structure of this domain. It shows a general fold very similar to other KIV domains with high and intermediate affinity for the lysine analog, ε-aminocaproic acid. Interestingly, KIV-2 presents a lysine binding site (LBS) with a unique shape and charge distribution. KIV-2 affinity for predicted small molecule binders was found to be negligible in surface plasmon resonance experiments; and with the LBS being nonfunctional, we propose to rename it "pseudo-LBS". Further investigation of the protein by computational small-molecule docking allowed us to identify a possible heparin-binding site away from the LBS, which was confirmed by specific reverse charge mutations abolishing heparin binding. This study opens new possibilities to define the pathogenesis of Lp(a)-related diseases and to facilitate the design of specific therapeutic drugs.

Enzymes in Metabolic Anticancer Therapy

Cancer treatment has greatly improved over the last 50 years, but it remains challenging in several cases. Useful therapeutic targets are normally unique peculiarities of cancer cells that distinguish them from normal cells and that can be tackled with appropriate drugs. It is now known that cell metabolism is rewired during tumorigenesis and metastasis as a consequence of oncogene activation and oncosuppressors inactivation, leading to a new cellular homeostasis typically directed towards anabolism. Because of these modifications, cells can become strongly or absolutely dependent on specific substrates, like sugars, lipids or amino acids. Cancer addictions are a relevant target for therapy, as removal of an essential substrate can lead to their selective cell-cycle arrest or even to cell death, leaving normal cells untouched. Enzymes can act as powerful agents in this respect, as demonstrated by asparaginase, which has been included in the treatment of Acute Lymphoblastic Leukemia for half a century. In this review, a short outline of cancer addictions will be provided, focusing on the main cancer amino acid dependencies described so far. Therapeutic enzymes which have been already experimented at the clinical level will be discussed, along with novel potential candidates that we propose as new promising molecules. The intrinsic limitations of their present molecular forms, along with molecular engineering solutions to explore, will also be presented.

Helicobacter pylori L-asparaginase: A Novel Bacterial Antigen that May Contribute to Infection Detection

Helicobacter pylori is responsible for gastric inflammation and for an increased risk of cancer development in humans. Several bacterial antigens contribute to stimulate the immune system, but their relative role has not yet been defined. H. pylori (strain CCUG) type II L-asparaginase (L-ASNase) induces an immune response in mice. To verify if an immune response could also be detected in humans, sera positive (n=11) or negative (n=11), respectively, to H. pylori according to a commercial test were assayed for their reactivity towards purified H. pylori L-ASNase. Among positive samples, 8/11 (72%) were positive to L-ASNase. We conclude that H. pylori L-ASNase is immunogenic in humans and contributes to the generation of the antibody response induced by the bacterium.

A protease-resistant Escherichia coli asparaginase with outstanding stability and enhanced anti-leukaemic activity in vitro

L-Asparaginases (ASNases) have been used as first line drugs for paediatric Acute Lymphoblastic Leukaemia (ALL) treatment for more than 40 years. Both the Escherichia coli (EcAII) and Erwinia chrysanthemi (ErAII) type II ASNases currently used in the clinics are characterized by high in vivo instability, short half-life and the requirement of several administrations to obtain a pharmacologically active concentration. Moreover, they are sensitive to proteases (cathepsin B and asparagine endopeptidase) that are over-expressed by resistant leukaemia lymphoblasts, thereby impairing drug activity and pharmacokinetics. Herein, we present the biochemical, structural and in vitro antiproliferative characterization of a new EcAII variant, N24S. The mutant shows completely preserved asparaginase and glutaminase activities, long-term storage stability, improved thermal parameters, and outstanding resistance to proteases derived from leukaemia cells. Structural analysis demonstrates a modification in the hydrogen bond network related to residue 24, while Normal Mode-based geometric Simulation and Molecular Dynamics predict a general rigidification of the monomer as compared to wild-type. These improved features render N24S a potential alternative treatment to reduce the number of drug administrations in vivo and to successfully address one of the major current challenges of ALL treatment: spontaneous, protease-dependent and immunological inactivation of ASNase.

Data on enhanced expression and purification of camelid single domain antibodies from Escherichia coli classical inclusion bodies

Heterologous expression of high amounts of recombinant proteins is a milestone for research and industrial purposes. Single domain antibodies (sdAbs) are heavy-chain only antibody fragments with applications in the biotechnological, medical and industrial fields. The simple nature and small size of sdAbs allows for efficient expression of the soluble molecule in different hosts. However, in some cases, it results in low functional protein yield. To overcome this limitation, expression of a 6xHistag sdAb was attempted in different conditions in Escherichia coli BL21(DE3) cells. Data showed that high amount of sdAb can be expressed in E. coli classical inclusion bodies, efficiently extracted by urea in a short-time, and properly purified by metal ion affinity chromatography. These data originate from the research article "Enhanced expression and purification of camelid single domain VHH antibodies from classical inclusion bodies" Maggi and Scotti (2017) [1] (DOI: http://dx.doi.org/10.1016/j.pep.2017.02.007).

Glutaminase activity determines cytotoxicity of L-asparaginases on most leukemia cell lines

L-Asparaginase (ASNase) is a front-line chemotherapy for acute lymphoblastic leukemia (ALL), which acts by deaminating asparagine and glutamine. To evaluate the importance of glutaminase activity, we exploited a recently developed mutant of Helicobacter pylori ASNase (dm HpA), with amino acid substitutions M121C/T169M. The mutant form has the same asparaginase activity as wild-type but lacks glutaminase activity. Wild-type and dm HpA were compared with the clinically used ASNases from Escherichia coli (l-ASP) and Erwinia chrysanthemi (ERWase). Asparaginase activity was similar for all isoforms, while glutaminase activity followed the rank order: ERWase>l-ASP>wild-type HpA>dm HpA. Cytotoxic efficacy of ASNases was tested on 11 human leukemia cell lines and two patient-derived ALL samples. Two cell lines which we had previously shown to be asparagine-dependent were equally sensitive to the asparaginase isoforms. The other nine lines and the two patient-derived samples were more sensitive to isoforms with higher glutaminase activities. ERWase was overall the most effective ASNase on all cell lines tested whereas dm HpA, having the lowest glutaminase activity, was the least effective. These data demonstrate that asparaginase activity alone may not be sufficient for ASNase cytotoxicity, and that glutaminase activity may be required for full anti-leukemic efficacy.

Engineering of Helicobacter pylori L-asparaginase: characterization of two functionally distinct groups of mutants

Bacterial L-asparaginases have been used as anti-cancer drugs for over 4 decades though presenting, along with their therapeutic efficacy, several side effects due to their bacterial origin and, seemingly, to their secondary glutaminase activity. Helicobacter pylori type II L-asparaginase possesses interesting features, among which a reduced catalytic efficiency for L-GLN, compared to the drugs presently used in therapy. In the present study, we describe some enzyme variants with catalytic and in vitro cytotoxic activities different from the wild type enzyme. Particularly, replacements on catalytic threonines (T16D and T95E) deplete the enzyme of both its catalytic activities, once more underlining the essential role of such residues. One serendipitous mutant, M121C/T169M, had a preserved efficiency vs L-asparagine but was completely unable to carry out L-glutamine hydrolysis. Interestingly, this variant did not exert any cytotoxic effect on HL-60 cells. The M121C and T169M single mutants had reduced catalytic activities (nearly 2.5- to 4-fold vs wild type enzyme, respectively). Mutant Q63E, endowed with a similar catalytic efficiency versus asparagine and halved glutaminase efficiency with respect to the wild type enzyme, was able to exert a cytotoxic effect comparable to, or higher than, the one of the wild type enzyme when similar asparaginase units were used. These findings may be relevant to determine the role of glutaminase activity of L-asparaginase in the anti-proliferative effect of the drug and to shed light on how to engineer the best asparaginase/glutaminase combination for an ever improved, patients-tailored therapy.

Activin Receptor-like kinase 1: a novel anti-angiogenesis target from TGF-β family

Anti-angiogenic therapy represents a very promising approach in cancer treatment, as most tumors needs to be supplied by a functional vascular network in order to grow beyond the local boundaries and metastatize. The accessibility of vessels to drug delivery and the broad spectrum of cancers treatable with the same compound have arisen interest in research of suitable molecules, with several, especially targeting the VEGF pathway, entered in clinical trials and approved by the Food and Drug Administration. Despite good results, the major hurdle resides in the limited duration of an effective clinical response before tumors start to grow again. Thus, researchers are looking for different alternative targets for a combined and parallel multi-targeting of angiogenic signaling circuits. Activin Receptor-like kinase 1 (ALK1) is a TGF-β type I receptor with high affinity for the BMP9 member of Bone Morphogenic Proteins superfamily: it is expressed mainly, even if not exclusively, on endothelial cells and seems to be involved in the regulatory phase of angiogenesis. Despite a non-completely elucidated mechanism, the targeting of this pathway, both by a soluble ALK1-Fc receptor developed by Acceleron Pharma and by a fully human monoclonal antibody developed by Pfizer, has achieved encouraging results. After having briefly summarized the state of the art of anti-angiogenic therapy, we will first review existing evidence about the molecular mechanisms of ALK1 signaling and we will then analyse in detail the pre-clinical and clinical data available about these two drugs.