Ubenimex inhibits cell proliferation, migration and invasion by inhibiting the expression of APN and inducing autophagic cell death in prostate cancer cells

Design and synthesis of novel sulfanilamide derivatives as aminopeptidase N inhibitors

Guided by the structural architecture of the aminopeptidase N (APN) active site, we designed and synthesized a series of novel APN inhibitors featuring sulfanilamide scaffold coupled with hydroxamate zinc-binding motifs. Among the series, compound 2k exhibited the inhibitory activity (IC50 = 4.3 μM) as effectively as a positive control drug Bestatin. Notably, our compounds exhibited pronounced selectivity against zinc-dependent metallopeptidase MMP-2. The SAR research indicated that ortho-disubstitution in the phenyl group could lead to an order of magnitude improvement. A molecular docking study validated the novel binding mode of compound 2k. The predicted ADME properties highlighted the improved hydrophilicity, cell permeability, and human oral absorption of 2k than that of bestatin. These results validated simultaneously occupying S1' and S2' pockets as a viable design strategy for discovering APN inhibitors with a non-canonical binding modality. We anticipate that compound 2k with high selectivity will be harnessed as a structurally distinctive probe candidate to investigate the pathophysiological roles of APN in tumor angiogenesis and metastasis.

CD13 as a potential theranostic target for prostate-specific membrane antigen-negative prostate cancer and first-in-human study of [18F]AlF-CD13-L1 PET/CT imaging

PURPOSE

Approximately 10% of prostate cancer (PCa) are prostate-specific membrane antigen (PSMA)-negative, leading to blind spots in PSMA-based diagnosis. This study aimed to identify a potential target for PSMA-negative PCa and preliminarily evaluate the feasibility of using radionuclide probe targeting the identified target for PCa diagnosis.

METHODS

Quantitative protein analysis was performed on eight PSMA-negative PCa and eleven controls to identify a potential molecular target, followed by validation with an expanded cohort using immunohistochemistry. Sixteen participants underwent [18F]AlF-CD13-L1 PET/CT scanning, with the PCa pathological tissues used as references to interpret the imaging results.

RESULTS

Quantitative protein analysis revealed CD13 as the most significantly upregulated membrane protein in PSMA-negative PCa. Expanded validation results indicated that CD13 positivity rates were 92.9% (13/14), 82.7% (105/127), 91.7% (11/12), and 70% (14/20) in PSMA-negative PCa, PSMA-positive PCa, ductal adenocarcinoma of the prostate (DAC), and intraductal carcinoma of the prostate (IDC-P), respectively. In PCa participants, the median [18F]AlF-CD13-L1 PET/CT maximum standardized uptake value (SUVmax) of tumors and tumor-to-muscle ratio were 4.3 (1.5-5.8) and 4.6 (1.7-6.1), respectively. The SUVmax value of the PCa lesions and the tumor-to-muscle ratio showed a positive correlation with the immunohistochemical score of CD13 of the PCa lesions (rspearman = 0.6249, p = 0.025; rspearman = 0.6714, p = 0.015, respectively), with CD13-positive tumors showing significant radiotracer accumulation.

CONCLUSION

CD13 was a potential target for PSMA-negative PCa and also showed high positivity rates in PSMA-positive PCa, DAC, and IDC-P. [18F]AlF-CD13-L1 selectively accumulated in CD13-positive PCa, enabling visualization. (Trial registration: ChiCTR2300077817. Registered November 21, 2023).

CD13 expression affects glioma patient survival and influences key functions of human glioblastoma cell lines in vitro

CD13 (APN) is an Alanyl-Aminopeptidase with diverse functions. The role of CD13 for gliomas is still unknown. In this study, data of glioma patients obtained by TCGA and CGGA databases were used to evaluate the survival rate and prognostic value of CD13 expression level. Protein expression of CD13 was confirmed by immunofluorescence staining of fresh patient tissues. Eight human glioblastoma cell lines were studied by RT-PCR, Western Blot, immunofluorescence staining and flow cytometry to define CD13 expression. Cell lines with different CD13 expression status were treated with a CD13 inhibitor, bestatin, and examined by MTT, scratch and colony formation assaysas well as by apoptosis assay and Western Blots. Bioinformatics analysis indicated that patients with high expression of CD13 had poor survival and prognosis. Additionally, CD13 protein expression was positively associated with clinical malignant characteristics. Investigated glioblastoma cell lines showed distinct expression levels and subcellular localization of CD13 with intracellular enrichment. Bestatin treatment reduced proliferation, migration and colony formation of glioma cells in a CD13-dependent manner while apoptosis was increased. In summary, CD13 has an impact on glioma patient survival and is important for the main function of specific glioma cells.

Ubenimex combined with Albendazole for the treatment of Echinococcus multilocularis-induced alveolar echinococcosis in mice

Introduction

Alveolar echinococcosis (AE) is a parasitic disease caused by E. multilocularis metacestodes and it is highly prevalent in the northern hemisphere. We have previously found that vaccination with E. multilocularis-Leucine aminopeptidase (EM-LAP) could inhibit the growth and invasion of E. multilocularis in host liver, and Ubenimex, a broad-spectrum inhibitor of LAP, could also inhibit E. multilocularis invasion but had a limited effect on the growth and development of E. multilocularis.

Methods

In this study, the therapeutic effect of Ubenimex combined with Albendazole on AE was evaluated. Mice were intraperitoneally injected with protoscoleces and imaging examination was performed at week 8 and week 16 to detect cyst change. During this period, mice were intraperitoneally injected with Ubenimex and intragastrically administered with Albendazole suspension. At last, the therapeutic effect was evaluated by morphological and pathological examination and liver function.

Results

The results revealed that the combined treatment could inhibit the growth and infiltration of cysts in BALB/c mice infected with E. multilocularis protoscoleces. The weight, number, invasion and fibrosis of cysts were reduced in mice treated with Ubenimex in combination with Albendazole. The same effect was achieved by the single Ubenimex treatment because of its inhibitory effect on LAP activity, but it was less effective in inhibiting the growth of cysts. The levels of ALT, AST, TBIL, DBIL, ALP, and γ-GT were reduced after the combined treatment, indicating that treatment with both Ubenimex and Albendazole could alleviate liver damage.

Discussion

This study suggests that the combined treatment with Ubenimex and Albendazole could be a potential therapeutic strategy for E. multilocularis infections.

Radiolabeled NGR-Based Heterodimers for Angiogenesis Imaging: A Review of Preclinical Studies

Since angiogenesis/neoangiogenesis has a major role in tumor development, progression and metastatic spread, the establishment of angiogenesis-targeting imaging and therapeutic vectors is of utmost significance. Aminopeptidase N (APN/CD13) is a pivotal biomarker of angiogenic processes abundantly expressed on the cell surface of active vascular endothelial and various neoplastic cells, constituting a valuable target for cancer diagnostics and therapy. Since the asparagine-glycine-arginine (NGR) sequence has been shown to colocalize with APN/CD13, the research interest in NGR-peptide-mediated vascular targeting is steadily growing. Earlier preclinical experiments have already demonstrated the imaging and therapeutic feasibility of NGR-based probes labeled with different positron emission tomography (PET) and single-photon emission computed tomography (SPECT) radionuclides, including Gallium-68 (68Ga), Copper-64 (64Cu), Technetium-99m (99mTc), Lutetium-177 (177Lu), Rhenium-188 (188Re) or Bismuth-213 (213Bi). To improve the tumor binding affinity and the retention time of single-receptor targeting peptides, NGR motifs containing heterodimers have been introduced to identify multi-receptor overexpressing malignancies. Preclinical studies with various tumor-bearing experimental animals provide useful tools for the investigation of the in vivo imaging behavior of NGR-based heterobivalent ligands. Herein, we review the reported preclinical achievements on NGR heterodimers that could be highly relevant for the development of further target-specific multivalent compounds in diagnostic and therapeutic settings.

NGR-Based Radiopharmaceuticals for Angiogenesis Imaging: A Preclinical Review

Angiogenesis plays a crucial role in tumour progression and metastatic spread; therefore, the development of specific vectors targeting angiogenesis has attracted the attention of several researchers. Since angiogenesis-associated aminopeptidase N (APN/CD13) is highly expressed on the surface of activated endothelial cells of new blood vessels and a wide range of tumour cells, it holds great promise for imaging and therapy in the field of cancer medicine. The selective binding capability of asparagine-glycine-arginine (NGR) motif containing molecules to APN/CD13 makes radiolabelled NGR peptides promising radiopharmaceuticals for the non-invasive, real-time imaging of APN/CD13 overexpressing malignancies at the molecular level. Preclinical small animal model systems are major keystones for the evaluation of the in vivo imaging behaviour of radiolabelled NGR derivatives. Based on existing literature data, several positron emission tomography (PET) and single-photon emission computed tomography (SPECT) radioisotopes have been applied so far for the labelling of tumour vasculature homing NGR sequences such as Gallium-68 (68Ga), Copper-64 (64Cu), Technetium-99m (99mTc), Lutetium-177 (177Lu), Rhenium-188 (188Re), or Bismuth-213 (213Bi). Herein, a comprehensive overview is provided of the recent preclinical experiences with radiolabelled imaging probes targeting angiogenesis.

Scandium-44: Diagnostic Feasibility in Tumor-Related Angiogenesis

Angiogenesis-related cell-surface molecules, including integrins, aminopeptidase N, vascular endothelial growth factor, and gastrin-releasing peptide receptor (GRPR), play a crucial role in tumour formation. Radiolabelled imaging probes targeting angiogenic biomarkers serve as valuable vectors in tumour identification. Nowadays, there is a growing interest in novel radionuclides other than gallium-68 (⁶⁸Ga) or copper-64 (⁶⁴Cu) to establish selective radiotracers for the imaging of tumour-associated neo-angiogenesis. Given its ideal decay characteristics (E_β⁺_average: 632 KeV) and a half-life (T_1/2 = 3.97 h) that is well matched to the pharmacokinetic profile of small molecules targeting angiogenesis, scandium-44 (⁴⁴Sc) has gained meaningful attention as a promising radiometal for positron emission tomography (PET) imaging. More recently, intensive research has been centered around the investigation of ⁴⁴Sc-labelled angiogenesis-directed radiopharmaceuticals. Previous studies dealt with the evaluation of ⁴⁴Sc-appended a_vb₃ integrin-affine Arg-Gly-Asp (RGD) tripeptides, GRPR-selective aminobenzoyl-bombesin analogue (AMBA), and hypoxia-associated nitroimidazole derivatives in the identification of various cancers using experimental tumour models. Given the tumour-related hypoxia- and angiogenesis-targeting capability of these PET probes, ⁴⁴Sc seems to be a strong competitor of the currently used positron emitters in radiotracer development. In this review, we summarize the preliminary preclinical achievements with ⁴⁴Sc-labelled angiogenesis-specific molecular probes.

Therapeutic Performance Evaluation of 213Bi-Labelled Aminopeptidase N (APN/CD13)-Affine NGR-Motif ([213Bi]Bi-DOTAGA-cKNGRE) in Experimental Tumour Model: A Treasured Tailor for Oncology

Since NGR-tripeptides (asparagine-glycine-arginine) selectively target neoangiogenesis-associated Aminopeptidase N (APN/CD13) on cancer cells, we aimed to evaluate the in vivo tumour targeting capability of radiolabelled, NGR-containing, ANP/CD13-selective [²¹³Bi]Bi-DOTAGA-cKNGRE in CD13pos. HT1080 fibrosarcoma-bearing severe combined immunodeficient CB17 mice. 10 ± 1 days after cancer cell inoculation, positron emission tomography (PET) was performed applying [⁶⁸Ga]Ga-DOTAGA-cKNGRE for tumour verification. On the 7th, 8th, 10th and 12th days the treated group of tumourous mice were intraperitoneally administered with 4.68 ± 0.10 MBq [²¹³Bi]Bi-DOTAGA-cKNGRE, while the untreated tumour-bearing animals received 150 μL saline solution. In addition to body weight (BW) and tumour volume measurements, ex vivo biodistribution studies were conducted 30 and 90 min postinjection (pi.). The following quantitative standardised uptake values (SUV) confirmed the detectability of the HT1080 tumours: SUV_mean and SUV_max: 0.37 ± 0.09 and 0.86 ± 0.14, respectively. Although no significant difference (p ≤ 0.05) was encountered between the BW of the treated and untreated mice, their tumour volumes measured on the 9th, 10th and 12th days differed significantly (p ≤ 0.01). Relatively higher [²¹³Bi]Bi-DOTAGA-cKNGRE accumulation of the HT1080 neoplasms (%ID/g: 0.80 ± 0.16) compared with the other organs at 90 min time point yields better tumour-to-background ratios. Therefore, the therapeutic application of APN/CD13-affine [²¹³Bi]Bi-DOTAGA- cKNGRE seems to be promising in receptor-positive fibrosarcoma treatment.

Therapeutic effect on Alveolar echinococcosis by targeting EM-Leucine aminopeptidase

Alveolar echinococcosis (AE) is a parasitic disease caused by E. multilocularis metacestodes and it is highly prevalent in the northern hemisphere. We have previously found that vaccination with E. multilocularis Leucine aminopeptidase (EM-LAP) induced specific immune response and had an inhibiting effect on the parasites. In this study, the therapeutic effect of recombinant EM-LAP (rEM-LAP) on AE was evaluated and verified using Ubenimex, a broad-spectrum inhibitor of LAP. The results reveal that rEM-LAP could inhibit cyst growth and invasion and induce specific immunity response in BALB/c mice infected with E. multilocularis protoscoleces. The ultrasonic, MRI, and morphological results show that treatment with rEM-LAP inhibits E. multilocularis infection and reduces cyst weight, number, fibrosis and invasion. The same effect is observed for the treatment with Ubenimex by inhibiting LAP activity. The indirect ELISA shows that rEM-LAP could induce specific immunity response and produce high levels of IgG, IgG1, IgG2a, IgM, and IgA, and the serum levels of IFN-γ and IL-4 are significantly increased compared to the control groups, indicating that treatment with rEM-LAP leads to a Th1 and Th2 mixed-type immune response. This study suggests that EM-LAP could be a potential therapeutic target of E. multilocularis infection.

Aminopeptidase N Inhibitors as Pointers for Overcoming Antitumor Treatment Resistance

Aminopeptidase N (APN), also known as CD13 antigen or membrane alanyl aminopeptidase, belongs to the M1 family of the MA clan of zinc metallopeptidases. In cancer cells, the inhibition of aminopeptidases including APN causes the phenomenon termed the amino acid deprivation response (AADR), a stress response characterized by the upregulation of amino acid transporters and synthetic enzymes and activation of stress-related pathways such as nuclear factor kB (NFkB) and other pro-apoptotic regulators, which leads to cancer cell death by apoptosis. Recently, APN inhibition has been shown to augment DR4-induced tumor cell death and thus overcome resistance to cancer treatment with DR4-ligand TRAIL, which is available as a recombinant soluble form dulanermin. This implies that APN inhibitors could serve as potential weapons for overcoming cancer treatment resistance. In this study, a series of basically substituted acetamidophenones and the semicarbazones and thiosemicarbazones derived from them were prepared, for which APN inhibitory activity was determined. In addition, a selective anti-proliferative activity against cancer cells expressing APN was demonstrated. Our semicarbazones and thiosemicarbazones are the first compounds of these structural types of Schiff bases that were reported to inhibit not only a zinc-dependent aminopeptidase of the M1 family but also a metalloenzyme.

Design, Synthesis, and Biological Evaluation of APN and AKT Dual-Target Inhibitors

Herein a novel series of APN and AKT dual inhibitors were derived from the clinical AKT inhibitor AZD5363. It was demonstrated that most compounds exhibited remarkable APN inhibitory activities with the most potent compound 8b (IC50 = 0.05 ± 0.01 μM) being over 70-fold more potent than the approved APN inhibitor bestatin (IC50 = 3.64 ± 0.56 μM). The moderate AKT inhibitory potencies of target compounds were also confirmed, with 5f and 5h possessing AKT1 IC50 values of 0.12 and 0.27 μM, respectively. More importantly, the APN IC50 values of 5f and 5h were 0.96 and 0.21 μM, respectively, indicating their balanced APN and AKT dual inhibition. HUVEC tube formation assays confirmed the superior APN inhibitory activities of 5f and 5h relative to bestatin at the cellular level. Western blot analysis demonstrated that 5h could effectively inhibit the phosphorylation of GSK3β, the intracellular substrate of AKT.

Is tumour-expressed aminopeptidase N (APN/CD13) structurally and functionally unique?

Aminopeptidase N (APN/CD13) is a multifunctional glycoprotein that acts as a peptidase, receptor, and signalling molecule in a tissue-dependent manner. The activities of APN have been implicated in the progression of many cancers, pointing toward significant therapeutic potential for cancer treatment. However, despite the tumour-specific functions of this protein that have been uncovered, the ubiquitous nature of its expression in normal tissues as generally reported remains a limitation to the potential utility of APN as a target for cancer therapeutics and drug discovery. With this in mind, we have extensively explored the literature, and present a comprehensive review that for the first-time provides evidence to support the suggestion that tumour-expressed APN may in fact be unique in structure, function, substrate specificity and activity, contrary to its nature in normal tissues. The review also focuses on the biology of APN, and its "moonlighting" functional roles in both normal physiology and cancer development. Several APN-targeting approaches that have been explored over recent decades as therapeutic strategies in cancer treatment, including APN-targeting agents reported both in preclinical and clinical studies, are also extensively discussed. This review concludes by posing critical questions about APN that remain unanswered and unexplored, hence providing opportunities for further research.

A comparison of the monomeric [68Ga]NODAGA-NGR and dimeric [68Ga]NOTA-(NGR)2 as aminopeptidase N ligand for positron emission tomography imaging in tumor-bearing mice

The aminopeptidase N (APN/CD13) is a key protein specifically expressed on activated endothelial cells and by various tumors, representing a promising target for molecular imaging and therapy of malignant diseases. It is known that the tripeptide NGR is a specific ligand for CD13, therefore radiolabeled NGR peptides are auspicious radiotracers for non-invasive imaging of CD13-positive tumors. From previous studies, it is known that the target affinity could be improved by molecules with multiple ligand sequences. Therefore, the aim of this study was to compare two NGR radioligands [⁶⁸Ga]NODAGA-NGR (NGR monomer) and [⁶⁸Ga]NOTA-(NGR)₂ (NGR dimer), the latter with two NGR ligand motifs, in vitro and in vivo. CD13 expression was determined by FACS in the human tumor cells A549, SKHep-1, and MDA-MB-231, followed by the investigation of the cell uptake of [⁶⁸Ga]NODAGA-NGR and [⁶⁸Ga]NOTA-(NGR)₂. For in vivo evaluation of [⁶⁸Ga]NODAGA-NGR and [⁶⁸Ga]NOTA-(NGR)₂, microPET and biodistribution were carried out in A549- and SKHep-1-bearing mice. After the final examination, tumors were cryo-conserved, cut, and stained against CD13 and CD31. A549 and SKHep-1 cells were identified as CD13 positive, whereas no CD13 expression was detected in MDA-MB-231 cells. The cell uptake study showed relatively low accumulation of both the NGR monomer and dimer in all tumor cell lines examined, with consistently higher cell uptake observed for the dimer than for the monomer. In vivo, [⁶⁸Ga]NODAGA-NGR and [⁶⁸Ga]NOTA-(NGR)₂ accumulated in the tumors, with slightly higher tumor-to-muscle ratio for the NGR dimer in A549 and SKHep-1. The tumor-to-liver ratio of the NGR dimer was diminished in comparison to the NGR monomer. This finding was confirmed by biodistribution, which revealed higher accumulation in liver and spleen for the NGR dimer. Immunohistochemical staining confirmed the CD13 expression in the tumors and tumor-associated vessels. In conclusion, both the [⁶⁸Ga]NODAGA-NGR and the [⁶⁸Ga]NOTA-(NGR)₂ were found to be suitable for PET imaging of CD13-positive tumors. Despite slight differences in tumor-to-background ratio and organ accumulation, both radiotracers can be considered comparable.

Injectable polypeptide-engineered hydrogel depot for amplifying the anti-tumor immune effect induced by chemo-photothermal therapy

The immunosuppressive tumor microenvironment has caused great obstacles to tumor immunotherapy, especially where less tumor-associated antigens are released from tumor sites. Herein, a Ag2S QD/DOX/Bestatin@PC10ARGD genetically engineered polypeptide hydrogel PC10ARGD as a sustained-release material was developed for mammary carcinoma treatment. A near-infrared silver sulfide (Ag2S) QD as a photosensitizer was encapsulated into the hydrophobic cavity formed by the self-assembly of the polypeptide nanogel (PC10ARGD) for photothermal therapy. The water-soluble drug DOX and Bestatin were integrated into the PC10ARGD hydrogel. The photothermal effect could trigger the sustained release of the DOX, which could be applied to initiate in situ vaccination. Bestatin as an immune-adjuvant drug could amplify the body's immune function. The results of in vivo therapy tests exhibited that the Ag2S QD/DOX/Bestatin@PC10ARGD hydrogel with laser irradiation could activate anti-tumor immune effects that inhibit the growth of primary tumors and distal lung metastatic nodules. Meanwhile, a safer lower-temperature with multiple laser irradiation treatment strategy exhibited more effective tumor-killing performance (84.4% tumor inhibition rate) and promoted the penetration of immune cells into the tumor tissue. The CD8+ and CD4+ cytotoxic T cells ratio was increased by 5.3 and 10 times, respectively, thus exhibiting a good prognostic signal. The multifunctional polypeptide hydrogel as a green manufacturing and engineering material is promising to serve as a cancer vaccine for anticancer applications.

In Vivo Molecular Imaging of the Efficacy of Aminopeptidase N (APN/CD13) Receptor Inhibitor Treatment on Experimental Tumors Using 68Ga-NODAGA-c(NGR) Peptide

Introduction

The aminopeptidase N (APN/CD13) receptor plays an important role in the neoangiogenic process and metastatic tumor cell invasion. Clinical and preclinical studies reported that bestatin and actinonin are cytotoxic to APN/CD13-positive tumors and metastases due to their APN/CD13-specific inhibitor properties. Our previous studies have already shown that ⁶⁸Ga-labeled NGR peptides bind specifically to APN/CD13 expressing tumor cells. The APN/CD13 specificity of ⁶⁸Ga-NGR radiopharmaceuticals enables the following of the efficacy of antiangiogenic therapy with APN/CD13-specific inhibitors using positron emission tomography (PET). The aim of this in vivo study was to assess the antitumor effect of bestatin and actinonin treatment in subcutaneous transplanted HT1080 and B16-F10 tumor-bearing animal models using ⁶⁸Ga-NODAGA-c(NGR).

Materials and Methods

Three days after the inoculation of HT1080 and B16-F10 cells, mice were treated with intraperitoneal injection of bestatin (15 mg/kg) or actinonin (5 mg/kg) for 7 days. On the 5^th and 10^th day, in vivo PET scans and ex vivo biodistribution studies were performed 90 min after intravenous injection of 5.5 ± 0.2 MBq⁶⁸Ga-NODAGA-c(NGR).

Results

Control-untreated HT1080 and B16-F10 tumors were clearly visualized by the APN/CD13-specific ⁶⁸Ga-NODAGA-c(NGR) radiopharmaceutical. The western blot analysis also confirmed the strong APN/CD13 positivity in the investigated tumors. We found significantly (p ≤ 0.05) lower radiopharmaceutical uptake after bestatin treatment and higher radiotracer accumulation in the actinonin-treated HT1080 tumors. In contrast, significantly lower (p ≤ 0.01) ⁶⁸Ga-NODAGA-c(NGR) accumulation was observed in both bestatin- and actinonin-treated B16-F10 melanoma tumors compared to the untreated-control tumors. Bestatin inhibited tumor growth and ⁶⁸Ga-NODAGA-c(NGR) uptake in both tumor models.

Conclusion

The bestatin treatment is suitable for suppressing the neoangiogenic process and APN/CD13 expression of experimental HT1080 and B16-F10 tumors; furthermore, ⁶⁸Ga-NODAGA-c(NGR) is an applicable radiotracer for the in vivo monitoring of the efficacy of the APN/CD13 inhibition-based anticancer therapies.

Identification of adhesion-associated DNA methylation patterns in the peripheral nervous system

Schwann cells are unique glial cells in the peripheral nervous system. These cells provide a range of cytokines and nutritional factors to maintain axons and support axonal regeneration. However, little is known concerning adhesion-associated epigenetic changes that occur in Schwann cells after peripheral nerve injury (PNI). In the present study, adhesion-associated DNA methylation biomarkers were assessed between normal and injury peripheral nerve. Specifically, normal Schwann cells (NSCs) and activated Schwann cells (ASCs) were obtained from adult Wistar rats. After the Schwann cells were identified, proliferation and adhesion assays were used to assess differences between NSCs and ASCs. Methylated DNA immunoprecipitation-sequencing and bioinformatics analysis were used to identify and analyze the differentially methylated genes. Reverse transcription-quantitative PCR was performed to assess the expression levels of adhesion-associated genes. In the present study, the proliferation and adhesion assays demonstrated that ASCs had a more robust proliferative activity and adhesion compared with NSCs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed to identify methylation-associated biological processes and signaling pathways. Protein-protein interaction network analysis revealed that Fyn, Efna1, Jak2, Vav3, Flt4, Epha7, Crk, Kitlg, Ctnnb1 and Ptpn11 were potential markers for Schwann cell adhesion. The expression levels of several adhesion-associated genes, such as vinculin, BCAR1 scaffold protein, collagen type XVIII α1 chain and integrin subunit β6, in ASCs were altered compared with those in NSCs. The current study analyzed adhesion-associated DNA methylation patterns of Schwann cells and identified candidate genes that may potentially regulate Schwann cell adhesion in Wistar rats before and after PNI.

Downregulation of miR-140-5p affects the pathogenesis of HSCR by targeting EGR2

BACKGROUND/AIMS

Hirschsprung's disease (HSCR) is the most common digestive disease caused by disorders of neural crest development. Despite the known involvement of miR-140-5p in many human diseases, its biological role in Hirschsprung's disease (HSCR) remains undefined. In this study, we sought to reveal the roles of miR-140-5p in the pathogenesis of HSCR.

METHODS

Quantitative real-time PCR and western blotting were used to measure the relative expression levels of miRNAs, mRNAs, and proteins in stenotic and dilated sections of the colon of 32 HSCR patients. Targets and proteins were evaluated by western blotting, and Transwell, CCK-8, and flow cytometry assays were adopted to detect the functional effects of miR-140-5p on SH-SY5Y cells.

RESULTS

miR-140-5p was significantly downregulated in HSCR tissue samples with increased expression of EGR2, and knockdown of miR-140-5p inhibited cell migration and proliferation and promoted apoptosis in SH-SY5Y cell lines. EGR2 expression was inversely correlated with that of miR-140-5p in cell lines.

CONCLUSIONS

miR-140-5p may influence the pathogenesis of HSCR by targeting EGR2.

Exploring the structural aspects of ureido-amino acid-based APN inhibitors: a validated comparative multi-QSAR modelling study

The zinc-dependent enzyme aminopeptidase N (APN) is a member of the M1 metalloenzyme family. The multi-functionality of APN as a peptidase, a receptor and a signalling molecule has provided it the access to influence a number of disease conditions namely viral diseases, angiogenesis, cellular metastasis and invasion including different cancer conditions. Hence, the development of potent APN inhibitors is a possible route for the treatment of diseases related to the activity of APN. In this study, different QSAR approaches have been adopted to identify the structural features of a group of hydroxamate-based ureido-amino acid derivative APN inhibitors. This study was able to identify different constitutional aspects of these APN inhibitors which are important for their inhibitory potency. Additionally, some of these observations were also aligned with the observations of previously performed QSAR studies conducted on different APN inhibitors. Therefore, the results of this study may help to design potent and effective APN inhibitors in the future.

MicroRNA-125a attenuates the chemoresistance against ubenimex in non-small cell lung carcinoma via targeting the aminopeptidase N signaling pathway

BACKGROUND

Since several long noncoding RNAs (lncRNAs) have been implicated in the development of chemoresistance in non-small cell lung carcinoma (NSCLC), the aim of this study was to investigate whether antisense noncoding RNA in the INK4 locus (ANRIL) was associated with the chemoresistance of NSCLC.

METHOD

Real-time polymerase chain reaction was performed to identify potential lncRNAs involved in the chemoresistance of NSCLC, while in-silicon analyses and luciferase assays were carried out to explore the regulatory relationship among ANRIL, miR-125a, and aminopeptidase N (APN).

RESULTS

Ubenimex resistant cells were associated with a high expression of ANRIL, which directly binds to miR-125a. MiR-125a directly targeted APN expression. In addition, miR-125a and ANRIL small interfering RNA inhibited the expression of APN but promoted the expression of beclin-1 and LC3, whereas ANRIL, by competing with miR-125a, promoted cell proliferation and inhibited cell apoptosis.

CONCLUSION

The data of this study suggested that, by targeting ANRIL and the APN signaling pathway, miR-125a inhibited the proliferation of NSCLC cells and promoted their apoptosis, thus attenuating the chemoresistance of NSCLC against Ubenimex.

Inhibition of LTA4H by bestatin in human and mouse colorectal cancer

Background

Our preclinical data showed that the leukotriene A4 hydrolase (LTA4H) pathway plays a role in colorectal cancer (CRC). High expression of LTA4H and leukotriene B4 receptor type 1 (BLT1) were also associated with CRC survival probability. Clinical samples were evaluated to determine whether LTA4H could serve as a therapeutic target and whether leukotriene B4 (LTB4) could be used as a biomarker for evaluating the efficacy of bestatin in CRC.

Methods

Patients with Stage I-III CRC did or did not receive bestatin prior to surgery. Evaluable pairwise CRC patient blood samples were collected to evaluate LTB4 concentration. Tissues were processed by immunohistochemistry to detect the LTA4H pathway and Ki-67 expression. We also determined whether LTA4H or BLT1 was associated with CRC survival probability and explored the mechanism of bestatin action in CRC.

Findings

Samples from 13 CRC patients showed a significant decrease in LTB4, the LTA4H signaling pathway, and Ki-67 in the bestatin-treated group compared with the untreated group. LTA4H and BLT1 are overexpressed in CRC and associated with CRC survival probability. Bestatin effectively inhibited LTB4 and tumorigenesis in the Apc^Min/+ and CRC patient-derived xenograft mouse model.

Interpretation

These results demonstrate that LTB4 could serve as a biomarker for evaluating bestatin efficacy in CRC and the antitumor effects of bestatin through its targeting of LTA4H and support further studies focusing on LTA4H inhibition in CRC.

Ubenimex enhances Brd4 inhibition by suppressing HEXIM1 autophagic degradation and suppressing the Akt pathway in glioma cells

Inhibition of Brd4 by JQ1 treatment showed potential in the treatment of glioma, however, some cases showed low sensitivity of JQ1. In addition, the pre-clinical analysis showed its limitation by demonstrating that transient treatment with JQ1 leads to aggressive tumor development. Thus, an improved understanding of the mechanisms underlying JQ1 is urgently required to design strategies to improve its efficiency, as well as overcome its limitation. HEXIM1 has been confirmed to have an important role in regulating JQ1 sensitivity. In our study, ubenimex, a classical anti-cancer drug showed potential in regulating the JQ1 sensitivity of glioma cells using the WST-1 proliferation assay. Further studies demonstrated that ubenimex inhibited autophagy and downregulated the autophagic degradation of HEXIM1. The role of HEXIM1 in regulating JQ1 sensitivity was verified by the HEXIM1 knockdown. Since ubenimex was verified as an Akt inhibitor, we further studied the role of Akt inhibition in regulating JQ1 sensitivity and migration of glioma cells. Data showed that ubenimex improved the efficiency of JQ1 treatment and suppressed migration both in the in vitro and in vivo xenografts models. The Akt agonist attenuated these effects, pointing to the role of Akt inhibition in JQ1 sensitivity and suppressed migration. Our findings suggest the potential of ubenimex adjuvant treatment to enhance JQ1 efficiency and attenuate parts of its side effect (enhancing tumor aggressive) by regulating the autophagic degradation of HEXIM1 and Akt inhibition.

Role of ubenimex as an anticancer drug and its synergistic effect with Akt inhibitor in human A375 and A2058 cells

Background

Malignant melanoma (MM) is a malignant tumor produced by changes in melanocytes in the skin or other organs. In the classification of skin tumor mortality, skin melanoma ranks the highest. Ubenimex, an Aminopeptidase N (APN) inhibitor, is now widely used for cancer as an adjunct therapy, conferring antitumor effects. Apoptosis and the induction of autophagy have both been found to be closely associated with tumor cell death.

Methods

In this study, the A375 and A2058 cell lines were treated with ubenimex. Cell viability was measured using the Cell Counting Kit 8 assay. Apoptosis and autophagic cell death were assessed using flow cytometry and acridine orange/ethidium bromide staining. Protein expression was assessed by Western blot analyses and immunofluorescence. Matrigel invasion and migration assays were used to examine the metastatic ability of melanoma cells.

Results

The results revealed that ubenimex inhibited the expression of APN in melanoma cells, which may be connected with the inhibition of metastasis. In addition, it increased melanoma cell death by inducing apoptosis and autophagic cell death. This effect was accompanied by increased levels of p-JNK. Moreover, treatment with ubenimex induced protective Akt activation, and combined use of an Akt inhibitor with ubenimex provided a better effect for inducing tumor cell death.

Conclusion

As an effective anti-tumor drug in vitro, ubenimex might be an excellent adjunctive therapy for the treatment of melanoma, with greater effects when combined with the use of an Akt inhibitor.

Ubenimex, an APN inhibitor, could serve as an anti‑tumor drug in RT112 and 5637 cells by operating in an Akt‑associated manner

Bladder cancer, a common urinary tract tumor, has high mortality and recurrence rates associated with metastasis. Aminopeptidase N (APN) expression and metastasis have been indicated to be associated with one another. Ubenimex may function as an APN inhibitor to inhibit the degradation of the extracellular matrix during tumorigenesis. Furthermore, APN has been widely used as an adjuvant therapy for the treatment of tumors; however, little information is available regarding the impact of ubenimex on patients. Autophagy is suggested to be important in the transformation and progression of cancer. Additionally, apoptosis, which leads to the rapid demolition of cellular organelles and structures, has also been suggested as an important factor. Thus, the present study investigated the role of ubenimex in inhibiting migration and invasion by downregulating APN expression levels to induce autophagic cell death and apoptosis in bladder cancer cells. RT112 and 5637 cell lines were treated with varying doses of ubenimex. Cell viability was measured by CCK8 colorimetry and flow cytometry. Using fluorescence microscopy, autophagic cell death was assessed using acridine orange/ethidium bromide staining. Furthermore, apoptotic cell death was assessed using flow cytometry and Trypan blue staining was used to evaluate the cell death rate. Protein expression was determined by western blot analysis. Matrigel invasion assays were exploited to assess the invasion capabilities of 5637 cells. Wound-healing migration assays and Matrigel migration assays were exploited to assess the migratory abilities of 5637 cells. Treatment with ubenimex was accompanied by decreased Akt expression, indicating that ubenimex may have similar functions to Akt inhibitors. Results also indicated that ubenimex inhibited cell migration and invasion in bladder cancer cells. Furthermore, ubenimex also induced autophagic cell death and apoptosis, which suggested that mixed programmed cell death occurred in ubenimex-treated bladder cancer cells. The results from the present study suggest that ubenimex may be a potential adjuvant therapy for the treatment of bladder cancer.

Synthesis and biological characterization of ubenimex-fluorouracil conjugates for anti-cancer therapy

Previously a novel ubenimex-fluorouracil (5-FU) conjugate, BC-01 was identified and validated as a potent CD13 inhibitor with marked in vitro and in vivo antitumor potency. Herein, further structural modifications of the linker part of BC-01 was carried out to get more potent and stable ubenimex-fluorouracil conjugates. It was striking that most of these conjugates showed even more potent CD13 inhibitory activities than BC-01 and the approved CD13 inhibitor ubenimex. One representative compound 12a displayed significant in vitro anti-proliferation, pro-apoptosis, anti-metastasis, anti-angiogenesis and CD13+ cell elimination effects. In vitro stability and in vivo pharmacokinetic study revealed that compound 12a could release ubenimex and 5-FU slowly, which could act as a mutual prodrug of ubenimex and 5-FU. Compared with 5-FU or 5-FU plus ubenimex, 12a exhibited superior in vivo antitumor growth efficiency, even in our mice model of 5-FU-resistant liver cancer. Moreover, 12a exhibited more potent in vivo anti-metastasis and lifespan extension effects compared to the approved 5-FU prodrug capecitabine. Collectively, these results suggest that further optimization and evaluation of 12a as a promising anticancer candidate are warranted to develop effective therapeutic agents for human liver cancer.

Autophagy flux inhibition, G2/M cell cycle arrest and apoptosis induction by ubenimex in glioma cell lines

This study aimed to investigate whether ubenimex could work as an anti-tumor drug alone in glioma cells and figure out the underlying potential mechanisms. Ubenimex is widely used as an adjunct therapy in multiple solid cancers. However, it is rarely used to treat glioblastoma. The function of ubenimex in enhancing JQ1 treatment sensitivity of glioma cells by blocking autophagic degradation of HEXIM1 was previously studied. However, the detailed mechanism of autophagy regulation by ubenimex remains unclear. The U87 and U251 cell lines were treated with different doses of ubenimex. Cell viability was measured by using the WST-8 assay. Cell death was assessed using trypan blue staining and flow cytometry. The migration and invasive ability of glioma cells were examined by transwell migration/invasion assay. LC3-GFP-RFP was used to measure autophagic flux. Protein expression was assessed by Western blot analysis. Autophagosomes were evaluated using the transmission electron microscopy. Moreover, cell cycle arrest (PI Staining) was measured by flow cytometry. Results revealed that ubenimex inhibited cell proliferation as well as migration/invasion in glioma cells. Besides, ubenimex increased glioma cell death via autophagic flux inhibition. Meanwhile, ubenimex induced G2/M phase arrest and apoptosis, and this effect was accompanied by the decreased levels of p-Akt, indicating the role of ubenimex in the regulation of glioma cell proliferation and metastasis. To sum up, this study concluded that ubenimex could work as an anti-tumor drug alone in the glioma cells via inhibiting autophagic flux and inducing G2/M arrest as well as apoptosis.

Silencing Livin induces apoptotic and autophagic cell death, increasing chemotherapeutic sensitivity to cisplatin of renal carcinoma cells

Renal cell carcinoma (RCC) accounts for 3 % of all adult malignancies and is the most lethal urological cancer. Livin is a member of the inhibitor of apoptosis protein (IAP) family, which is associated with tumor resistance to radiotherapy and chemotherapy. Clinical data also showed that patients with high tumor grades and stages have higher expression levels of Livin in RCC cells. Autophagy is a survival mechanism activated in response to nutrient deprivation. A possible role of Livin in the autophagy of RCC cells has not been investigated; therefore, this pioneer study was carried out. Livin was silenced in RCC cells (slow virus infection [SVI]-shLivin cells) by lentiviral transfection. Then, mRNA and protein expression levels in the transfected cells were assessed by quantitative fluorescence PCR and Western blotting, respectively. In addition, acridine orange staining and electron microscopy were used to assess autophagy in SVI-shLivin cells. The cisplatin IC50 values for RCC cells were measured by the CCK8 assay. Potent antitumor activities were observed in xenograft mouse models generated with Livin-silenced RCC cells in terms of delayed tumor onset and suppressed tumor growth. These results suggested that Livin silencing could increase the chemotherapeutic sensitivity of RCC cells to cisplatin and induce autophagic cell death. A possible mechanism of Bcl-2 and Akt pathway involvement was discussed specifically in this study. Overall, Livin silencing induces apoptotic and autophagic cell death and increases chemotherapeutic sensitivity of RCC cells to cisplatin.