Successful Preservation of Native BCR::ABL1 in Chronic Myeloid Leukemia Primary Leukocytes Reveals a Reduced Kinase Activity

Chronic myeloid leukemia (CML) is a myeloproliferative disease caused by the acquisition of t(9;22) generating the fusion tyrosine kinase BCR::ABL1. However, despite the crucial role of this protein in the dysregulation of numerous signal transduction pathways, a direct measure of BCR::ABL1 kinase activity in chronic phase (CP) CML was never accomplished due to intense degradative activity present in mature leukocytes. Therefore, we developed a procedure suitable to preserve BCR::ABL1 protein under non-denaturing, neutral pH conditions in primary, chronic phase (CP)-CML samples. As a result, specific kinase activity was detected utilizing a biotinylated peptide substrate highly selective for c-ABL1. Furthermore, through this approach, BCR::ABL1 kinase activity was barely detectable in CP-CML compared to Ph⁺ acute lymphoblastic leukemia primary samples, where kinase activity is comparable to those measured in Ph⁺ cell lines. These in vitro findings provide the first direct measure of BCR::ABL1 kinase activity in primary CP-CML and reveal the presence of a still uncharacterized inhibitory mechanism that maintains BCR::ABL1 in a low activity state in CP-CML despite its overexpression.

Predictive value of tyrosine phosphatase receptor gamma for the response to treatment tyrosine kinase inhibitors in chronic myeloid leukemia patients

Protein tyrosine phosphatase receptor gamma (PTPRG) is a member of the receptor-like family protein tyrosine phosphatases and acts as a tumor suppressor gene in different neoplasms. Recent studies reported the down-regulation of PTPRG expression levels in Chronic Myeloid Leukemia disease (CML). In addition, the BCR-ABL1 transcript level is currently a key predictive biomarker of CML response to treatment with Tyrosine Kinase Inhibitors (TKIs). The aim of this study was to employ flow cytometry to monitor the changes in the expression level of PTPRG in the white blood cells (WBCs) of CML patients at the time of diagnosis and following treatment with TKIs. WBCs from peripheral blood of 21 CML patients were extracted at diagnosis and during follow up along with seven healthy individuals. The PTPRG expression level was determined at protein and mRNA levels by both flow cytometry with monoclonal antibody (TPγ B9-2) and RT-qPCR, and BCR-ABL1 transcript by RT-qPCR, respectively. PTPRG expression was found to be lower in the neutrophils and monocytes of CML patients at time of diagnosis compared to healthy individuals. Treatment with TKIs nilotinib and Imatinib Mesylate restored the expression of PTPRG in the WBCs of CML patients to levels observed in healthy controls. Moreover, restoration levels were greatest in optimal responders and occurred earlier with nilotinib compared to imatinib. Our results support the measurement of PTPRG expression level in the WBCs of CML patients by flow cytometry as a monitoring tool for the response to treatment with TKIs in CML patients.

Aberrant DNA methylation of PTPRG as one possible mechanism of its under-expression in CML patients in the State of Qatar

Background

Several studies showed that aberrant DNA methylation is involved in leukemia and cancer pathogenesis. Protein tyrosine phosphatase receptor gamma (PTPRG) expression is a natural inhibitory mechanism that is downregulated in chronic myeloid leukemia (CML) disease. The mechanism behind its downregulation has not been fully elucidated yet.

Aim

This study aimed to investigate the CpG methylation status at the PTPRG locus in CML patients.

Methods

Peripheral blood samples from CML patients at time of diagnosis [no tyrosine kinase inhibitors (TKIs)] (n = 13), failure to (TKIs) treatment (n = 13) and healthy controls (n = 6) were collected. DNA was extracted and treated with bisulfite treatment, followed by PCR, sequencing of 25 CpG sites in the promoter region and 26 CpG sites in intron‐1 region of PTPRG. The bisulfite sequencing technique was employed as a high‐resolution method.

Results

CML groups (new diagnosed and failed treatment) showed significantly higher methylation levels in the promoter and intron‐1 regions of PTPRG compared to the healthy group. There were also significant differences in methylation levels of CpG sites in the promoter and intron‐1 regions amongst the groups.

Conclusion

Aberrant methylation of PTPRG is potentially one of the possible mechanisms of PTPRG downregulation detected in CML.

Detection of mycoplasma in contaminated mammalian cell culture using FTIR microspectroscopy

Mycoplasma contamination represents a significant problem to the culture of mammalian cells used for research as it can cause disastrous effects on eukaryotic cells by altering cellular parameters leading to unreliable experimental results. Mycoplasma cells are very small bacteria therefore they cannot be detected by visual inspection using a visible light microscope and, thus, can remain unnoticed in the cell cultures for long periods. The detection techniques used nowadays to reveal mycoplasma contamination are time consuming and expensive with each having significant drawbacks. The ideal detection should be simple to perform with minimal preparation time, rapid, inexpensive, and sensitive. To our knowledge, for the first time, we employed Fourier transform infrared (FTIR) microspectroscopy to investigate whether we can differentiate between control cells and the same cells which have been infected with mycoplasmas during the culturing process. Chemometric methods such as HCA and PCA were used for the data analysis in order to detect spectral differences between control and intentionally infected cells, and spectral markers were revealed even at low contamination level. The preliminary results showed that FTIR has the potential to be used in the future as a reliable complementary detection technique for mycoplasma-infected cells. Graphical abstract FTIR microspectroscopy is able to differentiate between mycoplasma infected cells (LC for low contamination and HC for high contamination) and control non-infected cells (CN).

Protein Tyrosine Phosphatase Gamma (PTPγ) is a Novel Leukocyte Marker Highly Expressed by CD34+ Precursors

Protein Tyrosine Phosphatase gamma (PTPγ) is a receptor-like transmembrane protein belonging to the family of classical protein tyrosine phosphatases. PTPγ is known to regulate haematopoietic differentiation in a murine embryonic stem cells model. We have recently demonstrated that PTPγ mRNA is expressed in monocytes, tissue-localized myeloid dendritic cells and in both myeloid and plasmacytoid dendritic cells in peripheral blood. We now developed a PTPγ specific antibody that recognizes the protein by flow cytometry. PTPγ expression was detected in monocytes and both myeloid and plasmacytoid dendritic cells, while PMN showed a low but consistent staining in contrast with previous mRNA data. B cells were found to express the phosphatase while T cells were negative. In keeping with RNA data, PTPγ was detected in monocyte-derived dendritic cells and its expression rose upon LPS stimulation. Finally, we discovered that CD34+ haematopoietic precursors express high PTPγ level that drops during in vitro expansion induced by IL-3 and SCF growth factors. We therefore propose PTPγ as a new functionally regulated leukocyte marker whose role in normal and pathological context deserve further investigation.

A new monoclonal antibody detects downregulation of protein tyrosine phosphatase receptor type γ in chronic myeloid leukemia patients

BACKGROUND

Protein tyrosine phosphatase receptor gamma (PTPRG) is a ubiquitously expressed member of the protein tyrosine phosphatase family known to act as a tumor suppressor gene in many different neoplasms with mechanisms of inactivation including mutations and methylation of CpG islands in the promoter region. Although a critical role in human hematopoiesis and an oncosuppressor role in chronic myeloid leukemia (CML) have been reported, only one polyclonal antibody (named chPTPRG) has been described as capable of recognizing the native antigen of this phosphatase by flow cytometry. Protein biomarkers of CML have not yet found applications in the clinic, and in this study, we have analyzed a group of newly diagnosed CML patients before and after treatment. The aim of this work was to characterize and exploit a newly developed murine monoclonal antibody specific for the PTPRG extracellular domain (named TPγ B9-2) to better define PTPRG protein downregulation in CML patients.

METHODS

TPγ B9-2 specifically recognizes PTPRG (both human and murine) by flow cytometry, western blotting, immunoprecipitation, and immunohistochemistry.

RESULTS

Co-localization experiments performed with both anti-PTPRG antibodies identified the presence of isoforms and confirmed protein downregulation at diagnosis in the Philadelphia-positive myeloid lineage (including CD34⁺/CD38^bright/dim cells). After effective tyrosine kinase inhibitor (TKI) treatment, its expression recovered in tandem with the return of Philadelphia-negative hematopoiesis. Of note, PTPRG mRNA levels remain unchanged in tyrosine kinase inhibitors (TKI) non-responder patients, confirming that downregulation selectively occurs in primary CML cells.

CONCLUSIONS

The availability of this unique antibody permits its evaluation for clinical application including the support for diagnosis and follow-up of these disorders. Evaluation of PTPRG as a potential therapeutic target is also facilitated by the availability of a specific reagent capable to specifically detect its target in various experimental conditions.

An ROR1 bi-specific T-cell engager provides effective targeting and cytotoxicity against a range of solid tumors

We have developed a humanized bi-specific T-cell engager (BiTE) targeting receptor tyrosine kinase-like orphan receptor 1 (ROR1), a cell surface antigen present on a range of malignancies and cancer-initiating cells. Focusing initially on pancreatic cancer, we demonstrated that our ROR1 BiTE results in T cell mediated and antigen-specific cytotoxicity against ROR1-expressing pancreatic cancer cell lines in vitro at exceedingly low concentrations (0.1 ng/mL) and low effector to target ratios. Our BiTE prevented engraftment of pancreatic tumor xenografts in murine models and reduced the size of established subcutaneous tumors by at least 3-fold. To validate its wider therapeutic potential, we next demonstrated significant cytotoxicity against ovarian cancer in an in vitro and in vivo setting and T-cell-mediated killing of a range of histologically distinct solid tumor cell lines. Overall, our ROR1 BiTE represents a promising immunotherapy approach, because of its ability to target a broad range of malignancies, many with significant unmet therapeutic needs.

Mutations of Cystic Fibrosis Transmembrane Conductance Regulator Gene Cause a Monocyte-Selective Adhesion Deficiency

RATIONALE

Cystic fibrosis (CF) is a common genetic disease caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Persistent lung inflammation, characterized by increasing polymorphonuclear leukocyte recruitment, is a major cause of the decline in respiratory function in patients with CF and is a leading cause of morbidity and mortality. CFTR is expressed in various cell types, including leukocytes, but its involvement in the regulation of leukocyte recruitment is unknown.

OBJECTIVES

We evaluated whether CF leukocytes might present with alterations in cell adhesion and migration, a key process governing innate and acquired immune responses.

METHODS

We used ex vivo adhesion and chemotaxis assays, flow cytometry, immunofluorescence, and GTPase activity assays in this study.

MEASUREMENTS AND MAIN RESULTS

We found that chemoattractant-induced activation of β1 and β2 integrins and of chemotaxis is defective in mononuclear cells isolated from patients with CF. In contrast, polymorphonuclear leukocyte adhesion and chemotaxis were normal. The functionality of β1 and β2 integrins was restored by treatment of CF monocytes with the CFTR-correcting drugs VRT325 and VX809. Moreover, treatment of healthy monocytes with the CFTR inhibitor CFTR(inh)-172 blocked integrin activation by chemoattractants. In a murine model of lung inflammation, we found that integrin-independent migration of CF monocytes into the lung parenchyma was normal, whereas, in contrast, integrin-dependent transmigration into the alveolar space was impaired. Finally, signal transduction analysis showed that, in CF monocytes, chemoattractant-triggered activation of RhoA and CDC42 Rho small GTPases (controlling integrin activation and chemotaxis, respectively) was strongly deficient.

CONCLUSIONS

Altogether, these data highlight the critical regulatory role of CFTR in integrin activation by chemoattractants in monocytes and identify CF as a new, cell type-selective leukocyte adhesion deficiency disease, providing new insights into CF pathogenesis.

Unsupervised explorative data analysis of normal human leukocytes and BCR/ABL positive leukemic cells mid-infrared spectra

We proved the ability of Fourier Transform Infrared microspectroscopy (microFTIR) complemented by Principal Component Analysis (PCA) to detect protein phosphorylation/de-phosphorylation in mammalian cells. We analyzed by microFTIR human polymorphonuclear neutrophil (PMNs) leukocytes, mouse-derived parental Ba/F3 cells (Ba/F3#PAR), Ba/F3 cells transfected with p210(BCR/ABL) (Ba/F3#WT) and expressing high levels of protein tyrosine kinase (PTK), and human-derived BCR/ABL positive K562 leukemic cell sub-clones engineered to differently express receptor-type tyrosine-protein phosphatase gamma (PTPRG). Synchrotron radiation (SR) and conventional (globar) IR sources were used to perform microFTIR respectively, on single cells and over several cells within the same sample. Ex vivo time-course experiments were run, inducing maximal protein phosphorylation in PMNs by 100 nM N-formylated tripeptide fMLP. Within the specific IR fingerprint 1800-850 cm(-1) frequency domain, PCA identified two regions with maximal signal variance. These were used to model and test the robustness of PCA in representing the dynamics of protein phosphorylation/de-phosphorylation processes. An IR signal ratio marker reflecting the homeostatic control by protein kinases and phosphatases was identified in normal leukocytes. The models identified by microFTIR and PCA in normal leukocytes also distinguished BCR/ABL positive Ba/F3#WT from BCR/ABL negative Ba/F3#PAR cells as well as K562 cells exposed to functionally active protein tyrosine phosphatase recombinant protein ICD-Tat transduced in cells by HIV-1 Tat technology or cells treated with the PTK inhibitor imatinib mesylate (IMA) from cells exposed to phosphatase inactive (D1028A)ICD-Tat recombinant protein and untreated control cells, respectively. The IR signal marker correctly reflected the degrees of protein phosphorylation associated with abnormal PTK activity in BCR/ABL positive leukemic cells and in general was inversely related to the expression/activity of PTPRG in leukemic sub-clones. In conclusion, we have described a new, reliable and simple spectroscopic method to study the ex vivo protein phosphorylation/de-phosphorylation balance in cell models: it is suitable for biomedical and pharmacological research labs but it also needs further optimization and its evaluation on large cohorts of patients to be proposed in the clinical setting of leukemia.

Germline polymorphisms and survival of lung adenocarcinoma patients: a genome-wide study in two European patient series

In lung cancer, the survival of patients with the same clinical stage varies widely for unknown reasons. In this two-phase study, we examined the hypothesis that germline variations influence the survival of patients with lung adenocarcinoma. First, we analyzed existing genotype and clinical data from 289 UK-resident patients with lung adenocarcinoma, identifying 86 single nucleotide polymorphisms (SNPs) that associated with survival (p < 0.01). We then genotyped these candidate SNPs in a validation series of 748 patients from Italy that resulted genetically compatible with the UK series based on principal component analysis. In a Cox proportional hazard model adjusted for age, sex and clinical stage, four SNPs were confirmed on the basis of their having a hazard ratio (HR) indicating the same direction of effect in the two series and p < 0.05. The strongest association was provided by rs2107561, an intronic SNP of PTPRG, protein tyrosine phosphatase, receptor type, G; the C allele was associated with poorer survival in both patient series (pooled analysis loge HR = 0.31; 95% CI: 0.15-0.46, p = 8.5 × 10(-5) ). PTPRG mRNA levels in 43 samples of lung adenocarcinoma were 40% of those observed in noninvolved lung tissue from the same patients. PTPRG overexpression significantly inhibited the clonogenicity of A549 lung carcinoma cells and the anchorage-independent growth of the NCI-H460 large cell lung cancer line. These four germline variants represent promising candidates that, with further study, may help predict clinical outcome. In addition, the PTPRG locus may have a role in tumor progression.

Immunohistochemical detection of arginine methylated proteins (MeRP) in archival tissues

AIMS

To (i) determine whether methylarginine-specific antibodies can be employed for standard immunohistochemical analysis of paraffin-embedded tissues, (ii) analyse methylarginine expression in normal and neoplastic tissues and (iii) correlate methylarginine expression with that of protein arginine methyltransferase (PRMT1), the predominant cellular arginine methyltransferase.

METHODS AND RESULTS

Immunohistochemistry of normal and cancer tissues was performed utilizing three commercial polyclonal antibodies: anti-methylarginine-specific antibody (anti-mRG) raised against a methylarginine peptide, Control antibody (anti-RG), a control antiserum raised against a corresponding arginine peptide without any methylated residues and anti-PRMT1. Nuclear and/or cytoplasmic methylarginine expression was detected in all keratinized and non-keratinized epithelia. A preliminary survey of a series of thyroid, pancreatic, colonic and gastric cancers identified a different pattern of methylarginine expression in comparison with normal tissue. A correlation between methylarginine staining and PRMT1 expression was found in all normal and cancer tissues analysed.

CONCLUSION

Methylarginine-specific antibodies are capable of recognizing methylarginine proteins (MeRP) in paraffin-embedded tissues. Methylarginine proteins are expressed widely and show differences in subcellular localization in various organs and neoplastic conditions. The efficient detection of methylproteins by standard immunohistochemistry provides a new tool to investigate the role of methylarginine proteins (MeRP) in biological processes including carcinogenesis.

Protein Tyrosine Phosphatase Gamma (PTPgamma) is a Novel Leukocyte Marker Highly Expressed by CD34 Precursors

Protein Tyrosine Phosphatase gamma (PTPgamma) is a receptor-like transmembrane protein belonging to the family of classical protein tyrosine phosphatases. PTPgamma is known to regulate haematopoietic differentiation in a murine embryonic stem cells model. We have recently demonstrated that PTPgamma mRNA is expressed in monocytes, tissue-localized myeloid dendritic cells and in both myeloid and plasmacytoid dendritic cells in peripheral blood. We now developed a PTPgamma specific antibody that recognizes the protein by flow cytometry. PTPgamma expression was detected in monocytes and both myeloid and plasmacytoid dendritic cells, while PMN showed a low but consistent staining in contrast with previous mRNA data. B cells were found to express the phosphatase while T cells were negative. In keeping with RNA data, PTPgamma was detected in monocyte-derived dendritic cells and its expression rose upon LPS stimulation. Finally, we discovered that CD34(+) haematopoietic precursors express high PTPgamma level that drops during in vitro expansion induced by IL-3 and SCF growth factors. We therefore propose PTPgamma as a new functionally regulated leukocyte marker whose role in normal and pathological context deserve further investigation.

Expression of transmembrane protein tyrosine phosphatase gamma (PTPgamma) in normal and neoplastic human tissues

AIMS

To establish the conditions for protein tyrosine phosphatase gamma (PTPgamma) detection in paraffin tissues using two antibodies raised against its NH(2)- (anti-P4) and COOH-termini (gammaTL1); to analyse its expression in normal tissues and to perform an initial screening of neoplastic tissues.

METHODS AND RESULTS

Membranous and/or cytoplasmic PTPgamma expression was detected in the majority of epithelial cell types and in endocrine cells, with the highest expression in adrenal medulla, endocrine cells of the gastrointestinal tract and pancreatic islets. Both antibodies stained the thyroid follicular epithelium, but only anti-P4 antibody stained the colloid matrix, suggesting shedding/secretion of the PTPgamma extracellular domain. Marked loss of PTPgamma immunoreactivity was detected in subsets of ovarian (21%), breast (56%) and lung (80%) neoplasms. Conversely, cytoplasmic positivity was found in 37% of lymphomas, mainly of high-grade histotypes, while normal lymphocytes were negative. Brain tissue showed PTPgamma expression in a few neuronal and glial elements and PTPgamma was overexpressed in the majority of high-grade astrocytomas.

CONCLUSIONS

We have analysed PTPgamma expression in archival paraffin-embedded tissues for the first time, demonstrating particularly high expression in endocrine cells and both down- and up-regulation in neoplasia, the latter possibly reflecting the undifferentiated state of the neoplastic cells, suggesting a complex role for this phosphatase.

Receptor-type protein tyrosine phosphatase gamma (PTPgamma), a new identifier for myeloid dendritic cells and specialized macrophages

Protein tyrosine phosphatase (PTPgamma) is a receptor-like molecule with a known role in murine hematopoiesis. We analyzed the regulation of PTPgamma expression in the human hematopoietic system, where it was detected in human peripheral blood monocytes and dendritic cells (DCs) of myeloid and plasmacytoid phenotypes. Its expression was maintained during in vitro monocyte differentiation to dendritic cells (moDC) and was further increased after maturation with bacterial lipopolysaccharide (LPS), CD40L, and TNFalpha. But PTPgamma was absent when monocytes from the same donor were induced to differentiate in macrophages. B and T lymphocytes did not express PTPgamma. Rather, PTPgamma mRNA was expressed in primary and secondary lymphoid tissues, and the highest expression was in the spleen. PTPgamma was detected by immunohistochemistry in subsets of myeloid-derived DCs and specialized macrophages (tingible bodies, sinus and alveolar macrophages). Classic macrophages in infective or reactive granulomatous reactions did not express PTPgamma. Increased PTPgamma expression was associated with a decreased ability to induce proliferation and interferon-gamma secretion in T cells by moDCs from patients with advanced pancreatic cancer. Taken together, these results indicate that PTPgamma is a finely regulated protein in DC and macrophage subsets in vitro and in vivo.