HS1 protein is differentially expressed in chronic lymphocytic leukemia patient subsets with good or poor prognoses

Proteomics and Drug Repurposing in CLL towards Precision Medicine

Simple Summary

Despite continued efforts, the current status of knowledge in CLL molecular pathobiology, diagnosis, prognosis and treatment remains elusive and imprecise. Proteomics approaches combined with advanced bioinformatics and drug repurposing promise to shed light on the complex proteome heterogeneity of CLL patients and mitigate, improve, or even eliminate the knowledge stagnation. In relation to this concept, this review presents a brief overview of all the available proteomics and drug repurposing studies in CLL and suggests the way such studies can be exploited to find effective therapeutic options combined with drug repurposing strategies to adopt and accost a more “precision medicine” spectrum.

Abstract

CLL is a hematological malignancy considered as the most frequent lymphoproliferative disease in the western world. It is characterized by high molecular heterogeneity and despite the available therapeutic options, there are many patient subgroups showing the insufficient effectiveness of disease treatment. The challenge is to investigate the individual molecular characteristics and heterogeneity of these patients. Proteomics analysis is a powerful approach that monitors the constant state of flux operators of genetic information and can unravel the proteome heterogeneity and rewiring into protein pathways in CLL patients. This review essences all the available proteomics studies in CLL and suggests the way these studies can be exploited to find effective therapeutic options combined with drug repurposing approaches. Drug repurposing utilizes all the existing knowledge of the safety and efficacy of FDA-approved or investigational drugs and anticipates drug alignment to crucial CLL therapeutic targets, leading to a better disease outcome. The drug repurposing studies in CLL are also discussed in this review. The next goal involves the integration of proteomics-based drug repurposing in precision medicine, as well as the application of this procedure into clinical practice to predict the most appropriate drugs combination that could ensure therapy and the long-term survival of each CLL patient.

3D-STED Super-Resolution Microscopy Reveals Distinct Nanoscale Organization of the Hematopoietic Cell-Specific Lyn Substrate-1 (HS1) in Normal and Leukemic B Cells

HS1, the hematopoietic homolog of cortactin, acts as a versatile actin-binding protein in leucocytes. After phosphorylation, it is involved in GTPase and integrin activation, and in BCR, TCR, and CXCR4 downstream signaling. In normal and leukemic B cells, HS1 is a central cytoskeletal interactor and its phosphorylation and expression are prognostic factors in chronic lymphocytic leukemia (CLL) patients. We here introduce for the first time a super-resolution imaging study based on single-cell 3D-STED microscopy optimized for revealing and comparing the nanoscale distribution of endogenous HS1 in healthy B and CLL primary cells. Our study reveals that the endogenous HS1 forms heterogeneous nanoclusters, similar to those of YFP-HS1 overexpressed in the leukemic MEC1 cell line. HS1 nanoclusters in healthy and leukemic B cells form bulky assemblies at the basal sides, suggesting the recruitment of HS1 for cell adhesion. This observation agrees with a phasor-FLIM-FRET and STED colocalization analyses of the endogenous MEC1-HS1, indicating an increased interaction with Vimentin at the cell adhesion sites. In CLL cells isolated from patients with poor prognosis, we observed a larger accumulation of HS1 at the basal region and a higher density of HS1 nanoclusters in the central regions of the cells if compared to good-prognosis CLL and healthy B cells, suggesting a different role for the protein in the cell types analyzed. Our 3D-STED approach lays the ground for revealing tiny differences of HS1 distribution, its functionally active forms, and colocalization with protein partners.

Transcriptome-Based Network Analysis Unveils Eight Immune-Related Genes as Molecular Signatures in the Immunomodulatory Subtype of Triple-Negative Breast Cancer

Objective: Triple-negative breast cancer (TNBC) is a high heterogeneity cancer. The identification of genomic aberrations that drive each of the TNBC subtypes may predict the prognosis of patients with TNBC and provide novel therapeutic strategies in clinical practice. This study focuses on the transcriptome-based gene expression of TNBC and aims to generate comprehensive gene co-expression networks correlated with the immune-related subtype of TNBC.

Methods: The transcriptome profiles of 107 female patients with TNBC were analyzed. Weighted gene co-expression network analysis (WGCNA) was applied to construct related networks and to sort hub-genes associated with the survival of TNBC patients. The data of the transcriptional expression, genomic alteration, survival status, and tumor immune microenvironment, which associated with hub-genes, were extracted, retrieved, and analyzed from Oncomine, UALCAN, TCGA, starBase, Kaplan–Meier Plotter, cBioPortal, and TIMER databases.

Results: Immune-related hub-genes, including BIRC3, BTN3A1, CSF2RB, GIMAP7, GZMB, HCLS1, LCP2, and SELL, were found to be associated with clinical features of TNBC evaluated by WGCNA. These hub-genes belonged to the immunomodulatory subtype of TNBC and were upregulated in the TNBC cells. The protein expression of eight immune-related hub-genes was further confirmed to be upregulated in TNBC/CD8+ tissues detected by immunohistochemical staining. Survival analysis revealed that overexpression of eight immune-related hub-genes was in favor of the survival of patients with TNBC. Moreover, a positive correlation between eight immune-related hub-genes and immune cell infiltration was observed in TNBC patients. Furthermore, checkpoint inhibitor genes such as PD-L1, PD-1, and CTLA4 were more enrichment in the immunomodulatory subtype of TNBC and the expression of PD-L1, PD-1, and CTLA4 was positively correlated with eight immune-related hub-genes in the breast cancer dataset of TCGA.

Conclusions: Eight immune-related hub-genes were identified to be molecular signatures in the immunomodulatory subtype of TNBC, which may provide therapeutic targets for the treatment of patients with breast cancer.

Actin regulators in cancer progression and metastases: From structure and function to cytoskeletal dynamics

The cytoskeleton is a central factor contributing to various hallmarks of cancer. In recent years, there has been increasing evidence demonstrating the involvement of actin regulatory proteins in malignancy, and their dysregulation was shown to predict poor clinical prognosis. Although enhanced cytoskeletal activity is often associated with cancer progression, the expression of several inducers of actin polymerization is remarkably reduced in certain malignancies, and it is not completely clear how these changes promote tumorigenesis and metastases. The complexities involved in cytoskeletal induction of cancer progression therefore pose considerable difficulties for therapeutic intervention; it is not always clear which cytoskeletal regulator should be targeted in order to impede cancer progression, and whether this targeting may inadvertently enhance alternative invasive pathways which can aggravate tumor growth. The entire constellation of cytoskeletal machineries in eukaryotic cells are numerous and complex; the system is comprised of and regulated by hundreds of proteins, which could not be covered in a single review. Therefore, we will focus here on the actin cytoskeleton, which encompasses the biological machinery behind most of the key cellular functions altered in cancer, with specific emphasis on actin nucleating factors and nucleation-promoting factors. Finally, we discuss current therapeutic strategies for cancer which aim to target the cytoskeleton.

ROR1 Is Expressed in Diffuse Large B-Cell Lymphoma (DLBCL) and a Small Molecule Inhibitor of ROR1 (KAN0441571C) Induced Apoptosis of Lymphoma Cells

The receptor tyrosine kinase ROR1 is absent in most normal adult tissues, but overexpressed in several malignancies. In this study, we explored clinical and functional inhibitory aspects of ROR1 in diffuse large B-cell lymphoma (DLBCL). ROR1 expression in tumor cells was more often observed in primary refractory DLBCL, Richter’s syndrome and transformed follicular lymphoma than in relapsed and non-relapsed DLBCL patients (p < 0.001). A survival effect of ROR1 expression was preliminarily observed in relapsed/refractory patients independent of gender and stage but not of age, cell of origin and international prognostic index. A second generation small molecule ROR1 inhibitor (KAN0441571C) induced apoptosis of ROR1+ DLBCL cell lines, similar to venetoclax (BCL-2 inhibitor) but superior to ibrutinib (BTK inhibitor). The combination of KAN0441571C and venetoclax at EC₅₀ concentrations induced almost complete killing of DLBCL cell lines. Apoptosis was accompanied by the downregulation of BCL-2 and MCL-1 and confirmed by the cleavage of PARP and caspases 3, 8, 9. PI3Kδ/AKT/mTOR (non-canonical Wnt pathway) as well as β-catenin and CK1δ (canonical pathway) were inactivated. In zebra fishes transplanted with a ROR1+ DLBCL cell line, KAN0441571C induced a significant tumor reduction. New drugs with mechanisms of action other than those available for DLBCL are warranted. ROR1 inhibitors might represent a novel promising approach.

Phase I Trial: Cirmtuzumab Inhibits ROR1 Signaling and Stemness Signatures in Patients with Chronic Lymphocytic Leukemia

Cirmtuzumab is a humanized monoclonal antibody (mAb) that targets ROR1, an oncoembryonic orphan receptor for Wnt5a found on cancer stem cells (CSCs). Aberrant expression of ROR1 is seen in many malignancies and has been linked to Rho-GTPase activation and cancer stem cell self-renewal. For patients with chronic lymphocytic leukemia (CLL), self-renewing, neoplastic B cells express ROR1 in 95% of cases. High-level leukemia cell expression of ROR1 is associated with an unfavorable prognosis. We conducted a phase 1 study involving 26 patients with progressive, relapsed, or refractory CLL. Patients received four biweekly infusions, with doses ranging from 0.015 to 20 mg/kg. Cirmtuzumab had a long plasma half-life and did not have dose-limiting toxicity. Inhibition of ROR1 signaling was observed, including decreased activation of RhoA and HS1. Transcriptome analyses showed that therapy inhibited CLL stemness gene expression signatures in vivo. Cirmtuzumab is safe and effective at inhibiting tumor cell ROR1 signaling in patients with CLL.

High cortactin expression in B-cell acute lymphoblastic leukemia is associated with increased transendothelial migration and bone marrow relapse

Cancer is a major cause of death in children worldwide, with B-lineage cell acute lymphoblastic leukemia (B-ALL) being the most frequent childhood malignancy. Relapse, treatment failure and organ infiltration worsen the prognosis, warranting a better understanding of the implicated mechanisms. Cortactin is an actin-binding protein involved in cell adhesion and migration that is overexpressed in many solid tumors and in adult B-cell chronic lymphocytic leukemia. Here, we investigated cortactin expression and potential impact on infiltration and disease prognosis in childhood B-ALL. B-ALL cell lines and precursor cells from bone marrow (BM) and cerebrospinal fluid (CSF) of B-ALL patients indeed overexpressed cortactin. In CXCL12-induced transendothelial migration assays, transmigrated B-ALL cells had highest cortactin expression. In xenotransplantation models, only cortactinhigh-leukemic cells infiltrated lungs, brain, and testis; and they colonized more easily hypoxic BM organoids. Importantly, cortactin-depleted B-ALL cells were significantly less efficient in transendothelial migration, organ infiltration and BM colonization. Clinical data highlighted a significant correlation between high cortactin levels and BM relapse in drug-resistant high-risk B-ALL patients. Our results emphasize the importance of cortactin in B-ALL organ infiltration and BM relapse and its potential as diagnostic tool to identify high-risk patients and optimize their treatments.

Hematopoietic cell-specific lyn substrate (HCLS1 or HS1): A versatile actin-binding protein in leukocytes

Leukocytes are constantly produced in the bone marrow and released into the circulation. Many different leukocyte subpopulations exist that exert distinct functions. Leukocytes are recruited to sites of inflammation and combat the cause of inflammation via many different effector functions. Virtually all of these processes depend on dynamic actin remodeling allowing leukocytes to adhere, migrate, phagocytose, and release granules. However, actin dynamics are not possible without actin-binding proteins (ABP) that orchestrate the balance between actin polymerization, branching, and depolymerization. The homologue of the ubiquitous ABP cortactin in hematopoietic cells is hematopoietic cell-specific lyn substrate-1, often called hematopoietic cell-specific protein-1 (HCLS1 or HS1). HS1 has been reported in different leukocytes to regulate Arp2/3-dependent migration. However, more evidence is emerging that HS1 functions go far beyond just being a direct actin modulator. For example, HS1 is important for the activation of GTPases and integrins, and mediates signaling downstream of many receptors including BCR, TCR, and CXCR4. In this review, we summarize current knowledge on HS1 functions and discuss them in a pathophysiologic context.

Altered expression of metabolic pathways in CLL detected by unlabelled quantitative mass spectrometry analysis

Chronic lymphocytic leukaemia (CLL) remains the most common incurable malignancy of B cells in the western world. Patient outcomes are heterogeneous and can be difficult to predict with current prognostic markers. Here, we used a quantitative label-free proteomic technique to ascertain differences in the B-cell proteome from healthy donors and CLL patients with either mutated (M-CLL) or unmutated (UM-CLL) IGHV to identify new prognostic markers. In peripheral B-CLL cells, 349 (22%) proteins were differentially expressed between normal B cells and B-CLL cells and 189 (12%) were differentially expressed between M-CLL and UM-CLL. We also examined the proteome of proliferating CLL cells in the lymph nodes, and identified 76 (~8%) differentially expressed proteins between healthy and CLL lymph nodes. B-CLL cells show over-expression of proteins involved in lipid and cholesterol metabolism. A comprehensive lipidomic analysis highlighted large differences in glycolipids and sphingolipids. A shift was observed from the pro-apoptotic lipid ceramide towards the anti-apoptotic/chemoresistant lipid, glucosylceramide, which was more evident in patients with aggressive disease (UM-CLL). This study details a novel quantitative proteomic technique applied for the first time to primary patient samples in CLL and highlights that primary CLL lymphocytes display markers of a metabolic shift towards lipid synthesis and breakdown.

Hematopoietic lineage cell-specific protein 1 (HS1), a hidden player in migration, invasion, and tumor formation, is over-expressed in ovarian carcinoma cells

Hematopoietic lineage cell-specific protein 1 (HS1), which is the hematopoietic homolog of cortactin, is an actin-binding protein and Lyn substrate. It is upregulated in several cancers and its expression level is associated with increased cell migration, metastasis, and poor prognosis. Here we investigated the expression and roles of HS1 in ovarian carcinoma cells. We analyzed the expression of HS1 in 171 ovarian cancer specimens and determined the association between HS1 expression and clinicopathological characteristics, including patient outcomes. In patients with stage II-IV disease, positive HS1 expression was associated with significantly worse overall survival than negative expression (P < 0.05). HS1 was localized in invadopodia in some ovarian cancer cells and was required for invadopodia formation. Migration and invasion of ovarian cancer cells were suppressed by down-regulation of HS1, but increased in cells that over-expressed exogenous HS1. Furthermore, ovarian cancer cells that expressed HS1 shRNA exhibited reduced tumor formation in a mouse xenograft model. Finally, we found that tyrosine phosphorylation of HS1 was essential for cell migration and invasion. These findings show that HS1 is a useful biomarker for the prognosis of patients with ovarian carcinoma and is a critical regulator of cytoskeleton remodeling involved in cell migration and invasion.

Hematopoietic lineage cell-specific protein 1 immunoreactivity indicates an increased risk of poor overall survival in patients with ovarian carcinoma

Hematopoietic lineage cell-specific protein 1 (HS1) is a 75-kDa intracellular protein that is expressed primarily in hematopoietic cells. Several previous studies have demonstrated the association between HS1 expression and a poor prognosis in hematopoietic malignancies; however, in solid tumors, no studies not been reported. The present study examined the distribution and expression of HS1 in human epithelial ovarian carcinoma (EOC) to determine its clinical significance. Paraffin sections were obtained from EOC tissues and immunostained with HS1 antibody, and then the staining intensities were evaluated. Overall survival (OS) was determined using the Kaplan-Meier estimator method, and multivariate analysis was performed using the Cox proportional hazards analysis. In total, 195 patients with EOC (median age, 56 years) were enrolled into the present study. HS1 immunoreactivity was categorized based on expression levels: Low (89/195; 45.6%) and high (106/195; 54.4%). Results demonstrated no association between expression level(s) and any clinicopathological parameter including age, International Federation of Gynecology and Obstetrics (FIGO) staging, type of chemotherapy or type of surgery received. The 5-year OS rates of patients who demonstrated low (n=89) and high (n=106) HS1 expression were 90.4 and 66.7%, respectively. The OS times for patients with high HS1 expression were significantly shorter compared with those for patients exhibiting low HS1 expression (P=0.0065). Results obtained from the multivariate analysis demonstrated that the FIGO stage and the amount of HS1 expressed were significant independent prognostic markers for poorer OS (hazard ratio, 3.539; 95% confidence interval, 1.221-12.811; P=0.0187). High HS1 expression levels may serve as a useful biomarker in patients with EOC who are likely to exhibit an unfavorable clinical outcome.

Genome-scale analysis to identify prognostic markers in patients with early-stage pancreatic ductal adenocarcinoma after pancreaticoduodenectomy

BACKGROUND

Molecular analysis is a promising source of clinically useful prognostic biomarkers. The aim of this investigation was to identify prognostic biomarkers for patients with early-stage pancreatic ductal adenocarcinoma (PDAC) after pancreaticoduodenectomy.

METHODS

An RNA sequencing dataset of PDAC was obtained from The Cancer Genome Atlas. Survival analysis and weighted gene co-expression network analysis were used to investigate the prognostic markers of early-stage PDAC after pancreaticoduodenectomy.

RESULTS

Using whole genome expression level screening, we identified 1,238 markers that were related to the prognosis of PDAC after pancreaticoduodenectomy, and identified 9 hub genes (ARHGAP30, HCLS1, CD96, FAM78A, ARHGAP15, SLA2, CD247, GVINP1, and IL16) using the weighted gene co-expression network analysis approach. We also constructed a signature comprising the 9 hub genes and weighted by the regression coefficient derived from a multivariate Cox proportional hazards regression model to divide patients into a high-risk group, with increased risk of death, and a low-risk group, with significantly improved overall survival (adjusted P=0.026, adjusted HR =0.513, 95% CI =0.285-0.924). The prognostic signature of the 9 genes demonstrated good performance for predicting 1-year overall survival (area under the respective receiver operating characteristic curves =0.641).

CONCLUSION

Our results have provided a new prospect for prognostic biomarkers of PDAC after pancreaticoduodenectomy, and may have a value in clinical application.

Wnt5a induces ROR1 to complex with HS1 to enhance migration of chronic lymphocytic leukemia cells

ROR1 (receptor tyrosine kinase-like orphan receptor 1) is a conserved, oncoembryonic surface antigen expressed in chronic lymphocytic leukemia (CLL). We found that ROR1 associates with hematopoietic-lineage-cell-specific protein 1 (HS1) in freshly isolated CLL cells or in CLL cells cultured with exogenous Wnt5a. Wnt5a also induced HS1 tyrosine phosphorylation, recruitment of ARHGEF1, activation of RhoA and enhanced chemokine-directed migration; such effects could be inhibited by cirmtuzumab, a humanized anti-ROR1 mAb. We generated truncated forms of ROR1 and found its extracellular cysteine-rich domain or kringle domain was necessary for Wnt5a-induced HS1 phosphorylation. Moreover, the cytoplamic, and more specifically the proline-rich domain (PRD), of ROR1 was required for it to associate with HS1 and allow for F-actin polymerization in response to Wnt5a. Accordingly, we introduced single amino acid substitutions of proline (P) to alanine (A) in the ROR1 PRD at positions 784, 808, 826, 841 or 850 in potential SH3-binding motifs. In contrast to wild-type ROR1, or other ROR1^P→A mutants, ROR1^P(841)A had impaired capacity to recruit HS1 and ARHGEF1 to ROR1 in response to Wnt5a. Moreover, Wnt5a could not induce cells expressing ROR1^P(841)A to phosphorylate HS1 or activate ARHGEF1, and was unable to enhance CLL-cell motility. Collectively, these studies indicate HS1 plays an important role in ROR1-dependent Wnt5a-enhanced chemokine-directed leukemia-cell migration.

Functional Differences between IgM and IgD Signaling in Chronic Lymphocytic Leukemia

BCR signaling is a central pathogenetic pathway in chronic lymphocytic leukemia (CLL). Most CLL cells express BCRs of IgM and IgD isotypes, but the contribution of these isotypes to functional responses remains incompletely defined. We therefore investigated differences between IgM and IgD signaling in freshly isolated peripheral blood CLL cells and in CLL cells cultured with nurselike cells, a model that mimics the lymph node microenvironment. IgM signaling induced prolonged activation of ERK kinases and promoted CLL cell survival, CCL3 and CCL4 chemokine secretion, and downregulation of BCL6, the transcriptional repressor of CCL3 In contrast, IgD signaling induced activation of the cytoskeletal protein HS1, along with F-actin polymerization, which resulted in rapid receptor internalization and failure to support downstream responses, including CLL cell survival and chemokine secretion. IgM and IgD receptor downmodulation, HS1 and ERK activation, chemokine secretion, and BCL6 downregulation were also observed when CLL cells were cocultured with nurselike cells. The Bruton's tyrosine kinase inhibitor ibrutinib effectively inhibited both IgM and IgD isotype signaling. In conclusion, through a variety of functional readouts, we demonstrate very distinct outcomes of IgM and IgD isotype activation in CLL cells, providing novel insight into the regulation of BCR signaling in CLL.

Microenvironment interactions and B-cell receptor signaling in Chronic Lymphocytic Leukemia: Implications for disease pathogenesis and treatment

Chronic Lymphocytic Leukemia (CLL) is a malignancy of mature B lymphocytes which are highly dependent on interactions with the tissue microenvironment for their survival and proliferation. Critical components of the microenvironment are monocyte-derived nurselike cells (NLCs), mesenchymal stromal cells, T cells and NK cells, which communicate with CLL cells through a complex network of adhesion molecules, chemokine receptors, tumor necrosis factor (TNF) family members, and soluble factors. (Auto-) antigens and/or autonomous mechanisms activate the B-cell receptor (BCR) and its downstream signaling cascade in secondary lymphatic tissues, playing a central pathogenetic role in CLL. Novel small molecule inhibitors, including the Bruton's tyrosine kinase (BTK) inhibitor ibrutinib and the phosphoinositide-3-kinase delta (PI3Kδ) inhibitor idelalisib, target BCR signaling and have become the most successful new therapeutics in this disease. We here review the cellular and molecular characteristics of CLL cells, and discuss the cellular components and key pathways involved in the cross-talk with their microenvironment. We also highlight the relevant novel treatment strategies, focusing on immunomodulatory agents and BCR signaling inhibitors and how these treatments disrupt CLL-microenvironment interactions. This article is part of a Special Issue entitled: Tumor Microenvironment Regulation of Cancer Cell Survival, Metastasis, Inflammation, and Immune Surveillance edited by Peter Ruvolo and Gregg L. Semenza.

TCL1 transgenic mouse model as a tool for the study of therapeutic targets and microenvironment in human B-cell chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy with a mature phenotype. In spite of its relatively indolent nature, no radical cure is as yet available. CLL is not associated with either a unique cytogenetic or a molecular defect, which might have been a potential therapeutic target. Instead, several factors are involved in disease development, such as environmental signals which interact with genetic abnormalities to promote survival, proliferation and an immune surveillance escape. Among these, PI3-Kinase signal pathway alterations are nowadays considered to be clearly important. The TCL1 gene, an AKT co-activator, is the cause of a mature T-cell leukemia, as well as being highly expressed in all B-CLL. A TCL1 transgenic mouse which reproduces leukemia with a distinct immunophenotype and similar to the course of the human B-CLL was developed several years ago and is widely used by many groups. This is a review of the CLL biology arising from work of many independent investigators who have used TCL1 transgenic mouse model focusing on pathogenetic, microenviroment and therapeutic targets.

Mesenchymal stromal cells of osteosarcoma patients do not show evidence of neoplastic changes during long-term culture

Background

In vitro expanded mesenchymal stromal cells (MSCs) are increasingly used as experimental cellular therapy. However, there have been concerns regarding the safety of their use, particularly with regard to possible oncogenic transformation. MSCs are the hypothesized precursor cells of high-grade osteosarcoma, a tumor with often complex karyotypes occurring mainly in adolescents and young adults.

Methods

To determine if MSCs from osteosarcoma patients could be predisposed to malignant transformation we cultured MSCs of nine osteosarcoma patients and five healthy donors for an average of 649 days (range 601–679 days). Also, we compared MSCs derived from osteosarcoma patients at diagnosis and from healthy donors using genome wide gene expression profiling.

Results

Upon increasing passage, increasing frequencies of binucleate cells were detected, but no increase in proliferation suggestive of malignant transformation occurred in MSCs from either patients or donors. Hematopoietic cell specific Lyn substrate 1 (HLCS1) was differentially expressed (fold change 0.25, P value 0.0005) between MSCs of osteosarcoma patients (n = 14) and healthy donors (n = 9).

Conclusions

This study shows that although HCLS1 expression was downregulated in MSCs of osteosarcoma patients and binucleate cells were present in both patient and donor derived MSCs, there was no evidence of neoplastic changes to occur during long-term culture.

Electronic supplementary material

The online version of this article (doi:10.1186/s13569-015-0031-1) contains supplementary material, which is available to authorized users.

Excessive antigen reactivity may underlie the clinical aggressiveness of chronic lymphocytic leukemia stereotyped subset #8

Subset #8 is a distinctive subset of patients with chronic lymphocytic leukemia (CLL) defined by the expression of stereotyped IGHV4-39/IGKV1(D)-39 B-cell receptors. Subset #8 patients experience aggressive disease and exhibit the highest risk for Richter transformation among all CLL. In order to obtain biological insight into this behavior, we profiled the antigen reactivity and signaling capacity of subset #8 vs other clinically aggressive stereotyped subsets, namely subsets #1 and #2. Twenty-seven monoclonal antibodies (mAbs) from subsets #1, #2, and #8 CLL clones were prepared as recombinant human immunoglobulin G1 and used as primary antibodies in enzyme-linked immunosorbent assays against representatives of the major classes of established antigenic targets for CLL. Subset #8 CLL mAbs exhibited broad polyreactivity as they bound to all antigens tested, in clear contrast with the mAbs from the other subsets. Antigen challenge of primary CLL cells indicated that the promiscuous antigen-binding activity of subset #8 mAbs could lead to significant cell activation, again in contrast to the less responsive CLL cells from subsets #1 and #2. These features constitute a distinctive profile for CLL subset #8, supporting the existence of distinct mechanisms of aggressiveness in different immunogenetic subsets of CLL.

Total proteome analysis identifies migration defects as a major pathogenetic factor in immunoglobulin heavy chain variable region (IGHV)-unmutated chronic lymphocytic leukemia

The mutational status of the immunoglobulin heavy chain variable region defines two clinically distinct forms of chronic lymphocytic leukemia (CLL) known as mutated (M-CLL) and unmutated (UM-CLL). To elucidate the molecular mechanisms underlying the adverse clinical outcome associated with UM-CLL, total proteomes from nine UM-CLL and nine M-CLL samples were analyzed by isobaric tags for relative and absolute quantification (iTRAQ)-based mass spectrometry. Based on the expression of 3521 identified proteins, principal component analysis separated CLL samples into two groups corresponding to immunoglobulin heavy chain variable region mutational status. Computational analysis showed that 43 cell migration/adhesion pathways were significantly enriched by 39 differentially expressed proteins, 35 of which were expressed at significantly lower levels in UM-CLL samples. Furthermore, UM-CLL cells underexpressed proteins associated with cytoskeletal remodeling and overexpressed proteins associated with transcriptional and translational activity. Taken together, our findings indicate that UM-CLL cells are less migratory and more adhesive than M-CLL cells, resulting in their retention in lymph nodes, where they are exposed to proliferative stimuli. In keeping with this hypothesis, analysis of an extended cohort of 120 CLL patients revealed a strong and specific association between UM-CLL and lymphadenopathy. Our study illustrates the potential of total proteome analysis to elucidate pathogenetic mechanisms in cancer.

Microenvironment dependency in Chronic Lymphocytic Leukemia: The basis for new targeted therapies

Chronic Lymphocytic Leukemia (CLL) is a prototype microenvironment-dependent B-cell malignancy, in which the neoplastic B cells co-evolve together with a supportive tissue microenvironment, which promotes leukemia cell survival, growth, and drug-resistance. Chemo-immunotherapy is an established treatment modality for CLL patients, resulting in high rates of responses and improved survival, especially in low-risk CLL. New, alternative treatments target B-cell receptor (BCR) signaling and the Chemokine (C-X-C motif) Receptor 4 (CXCR4)-Chemokine (C-X-C motif) Ligand 12 (CXCL12) axis, which are key pathways of CLL-microenvironment cross talk. The remarkable clinical efficacy of inhibitors targeting the BCR-associated kinases Bruton's tyrosine kinase (BTK) and phosphoinositide 3-kinase delta (PI3Kδ) challenges established therapeutic paradigms and corroborates the central role of BCR signaling in CLL pathogenesis. In this review, we discuss the cellular and molecular components of the CLL microenvironment. We also describe the emerging therapeutic options for CLL patients, with a focus on inhibitors of CXCR4-CXCL12 and BCR signaling.

From a 2DE-gel spot to protein function: lesson learned from HS1 in chronic lymphocytic leukemia

The identification of molecules involved in tumor initiation and progression is fundamental for understanding disease's biology and, as a consequence, for the clinical management of patients. In the present work we will describe an optimized proteomic approach for the identification of molecules involved in the progression of Chronic Lymphocytic Leukemia (CLL). In detail, leukemic cell lysates are resolved by 2-dimensional Electrophoresis (2DE) and visualized as "spots" on the 2DE gels. Comparative analysis of proteomic maps allows the identification of differentially expressed proteins (in terms of abundance and post-translational modifications) that are picked, isolated and identified by Mass Spectrometry (MS). The biological function of the identified candidates can be tested by different assays (i.e. migration, adhesion and F-actin polymerization), that we have optimized for primary leukemic cells.

Mouse models in the study of chronic lymphocytic leukemia pathogenesis and therapy

Mouse models that recapitulate human malignancy are valuable tools for the elucidation of the underlying pathogenetic mechanisms and for preclinical studies. Several genetically engineered mouse models have been generated, either mimicking genetic aberrations or deregulated gene expression in chronic lymphocytic leukemia (CLL). The usefulness of such models in the study of the human disease may potentially be hampered by species-specific biological differences in the target cell of the oncogenic transformation. Specifically, do the genetic lesions or the deregulated expression of leukemia-associated genes faithfully recapitulate the spectrum of lymphoproliferations in humans? Do the CLL-like lymphoproliferations in the mouse have the phenotypic, histological, genetic, and clinical features of the human disease? Here we compare the various CLL mouse models with regard to disease phenotype, penetrance, and severity. We discuss similarities and differences of the murine lymphoproliferations compared with human CLL. We propose that the Eμ-TCL1 transgenic and 13q14-deletion models that have been comprehensively studied at the levels of leukemia phenotype, antigen-receptor repertoire, and disease course show close resemblance to the human disease. We conclude that modeling CLL-associated genetic dysregulations in mice can provide important insights into the molecular mechanisms of disease pathogenesis and generate valuable tools for the development of novel therapies.

Does B cell receptor signaling in chronic lymphocytic leukaemia cells differ from that in other B cell types?

Chronic lymphocytic leukaemia (CLL) is an incurable malignancy of mature B cells. CLL is important clinically in Western countries because of its commonality and because of the significant morbidity and mortality associated with the progressive form of this incurable disease. The B cell receptor (BCR) expressed on the malignant cells in CLL contributes to disease pathogenesis by providing signals for survival and proliferation, and the signal transduction pathway initiated by engagement of this receptor is now the target of several therapeutic strategies. The purpose of this review is to outline current understanding of the BCR signal cascade in normal B cells and then question whether this understanding applies to CLL cells. In particular, this review studies the phenomenon of anergy in CLL cells, and whether certain adaptations allow the cells to overcome anergy and allow full BCR signaling to take place. Finally, this review analyzes how BCR signals can be therapeutically targeted for the treatment of CLL.

Molecular pathways: targeting the microenvironment in chronic lymphocytic leukemia--focus on the B-cell receptor

Interactions between malignant B lymphocytes and the tissue microenvironment play a major role in the pathogenesis of chronic lymphocytic leukemia (CLL) and other B-cell malignancies. The coexistence and coevolution of CLL cells with their tissue neighbors provided the basis for discovery of critical cellular and molecular drivers of the disease and identification of new therapeutic targets. Bone marrow stromal cells (BMSC), monocyte-derived nurselike cells (NLC), and T cells are key players in the CLL microenvironment, which activate and protect CLL cells within the tissues. CLL surface molecules, such as the B-cell antigen receptor (BCR), chemokine receptors, adhesion molecules, and TNF receptor superfamily members (e.g., CD40, BCMA, and BAFF-R) engage in cross-talk with respective tissue ligands. This cross-talk results in survival and expansion of the CLL clone, and protects CLL cells from conventional cytotoxic drugs. Inhibiting these pathways represents an alternative therapeutic strategy to more conventional chemoimmunotherapy. Here, we review central components of the CLL microenvironment, with a particular emphasis on BCR signaling, and we summarize the most relevant clinical advances with inhibitors that target the BCR-associated spleen tyrosine kinase/SYK (fostamatinib), Bruton's tyrosine kinase/BTK (ibrutinib), and PI3Kδ (idelalisib).

CIP4 controls CCL19-driven cell steering and chemotaxis in chronic lymphocytic leukemia

Solid tumor dissemination relies on the reprogramming of molecular pathways controlling chemotaxis. Whether the motility of nonsolid tumors such as leukemia depends on the deregulated expression of molecules decoding chemotactic signals remains an open question. We identify here the membrane remodeling F-BAR adapter protein Cdc42-interacting protein 4 (CIP4) as a key regulator of chemotaxis in chronic lymphocytic leukemia (CLL). CIP4 is expressed at abnormally high levels in CLL cells, where it is required for CCL19-induced chemotaxis. Upon CCL19 stimulation of CLL cells, CIP4 associates with GTP-bound Cdc42 and is recruited to the rear of the lamellipodium and along microspikes radiating through the lamellipodium. Consistent with its cellular distribution, CIP4 removal impairs both the assembly of the polarized lamellipodium and directional migration along a diffusible CCL19 gradient. Furthermore, CIP4 depletion results in decreased activation of WASP, but increased activation of PAK1 and p38 mitogen-activated protein kinase (MAPK). Notably, p38 MAPK inhibition results in impaired lamellipodium assembly and loss of directional migration. This suggests that CIP4 modulates both the WASP and p38 MAPK pathways to promote lamellipodium assembly and chemotaxis. Overall, our study reveals a critical role of CIP4 in mediating chemotaxis of CLL cells by controlling the dynamics of microspike-containing protrusions and cell steering.

Targeting the LYN/HS1 signaling axis in chronic lymphocytic leukemia

HS1 protein activation is differentially regulated by LYN kinase in CLL subsets. Dasatinib targets cytoskeletal activity, BCR signaling and survival of a sizable portion of patients with activated LYN/HS1.

Interactions among HCLS1, HAX1 and LEF-1 proteins are essential for G-CSF-triggered granulopoiesis

We found that hematopoietic cell-specific Lyn substrate 1 (HCLS1 or HS1) is highly expressed in human myeloid cells and that stimulation with granulocyte colony-stimulating factor (G-CSF) leads to HCLS1 phosphorylation. HCLS1 binds the transcription factor lymphoid-enhancer binding factor 1 (LEF-1), transporting LEF-1 into the nucleus upon G-CSF stimulation and inducing LEF-1 autoregulation. In patients with severe congenital neutropenia, inherited mutations in the gene encoding HCLS1-associated protein X-1 (HAX1) lead to profound defects in G-CSF-triggered phosphorylation of HCLS1 and subsequently to reduced autoregulation and expression of LEF-1. Consistent with these results, HCLS1-deficient mice are neutropenic. In bone marrow biopsies of the majority of tested patients with acute myeloid leukemia, HCLS1 protein expression is substantially elevated, associated with high levels of G-CSF synthesis and, in some individuals, a four-residue insertion in a proline-rich region of HCLS1 protein known to accelerate intracellular signaling. These data demonstrate the importance of HCLS1 in myelopoiesis in vitro and in vivo.

Targeting the microenvironment in chronic lymphocytic leukemia offers novel therapeutic options

Chronic lymphocytic leukemia (CLL) cells display features consistent with a defect in apoptosis and exhibit prolonged survival in vivo. Survival of these malignant cells is influenced by interactions with non-leukemic cells located in permissive niches in lymphoid organs. Leukemic cells subvert the normal architecture of the lymphoid organs, recruiting stromal cells, dendritic cells and T lymphocytes, all reported as playing active roles in the survival and proliferation of CLL. The same survival-promoting environment also rescues/protects leukemic cells from cytotoxic therapies, giving way to disease relapse. This review summarizes and discusses current knowledge about the intricate network of soluble and cell-bound signals regulating the life and death of CLL cells in different districts. At the same time, it seeks to hone in on which discrete molecular elements are best suited as targets for treating this still incurable disease.

HS1, a Lyn kinase substrate, is abnormally expressed in B-chronic lymphocytic leukemia and correlates with response to fludarabine-based regimen

In B-Chronic Lymphocytic Leukemia (B-CLL) kinase Lyn is overexpressed, active, abnormally distributed, and part of a cytosolic complex involving hematopoietic lineage cell-specific protein 1 (HS1). These aberrant properties of Lyn could partially explain leukemic cells' defective apoptosis, directly or through its substrates, for example, HS1 that has been associated to apoptosis in different cell types. To verify the hypothesis of HS1 involvement in Lyn-mediated leukemic cell survival, we investigated HS1 protein in 71 untreated B-CLL patients and 26 healthy controls. We found HS1 overexpressed in leukemic as compared to normal B lymphocytes (1.38±0.54 vs 0.86±0.29, p<0.01), and when HS1 levels were correlated to clinical parameters we found a higher expression of HS1 in poor-prognosis patients. Moreover, HS1 levels significantly decreased in ex vivo leukemic cells of patients responding to a fludarabine-containing regimen. We also observed that HS1 is partially localized in the nucleus of neoplastic B cells. All these data add new information on HS1 study, hypothesizing a pivotal role of HS1 in Lyn-mediated modulation of leukemic cells' survival and focusing, one more time, the attention on the BCR-Lyn axis as a putative target for new therapeutic strategies in this disorder.

Lymph node-induced immune tolerance in chronic lymphocytic leukaemia: a role for caveolin-1

Emerging evidence indicates that the tumour microenvironment (TME) regulates the behaviour of chronic lymphocytic leukaemia (CLL). However, the precise mechanism and molecules involved in this process remain unknown. Gene expression profiles of CLL cells from lymph node (LN), bone marrow (BM) and peripheral blood (PB) indicate overexpression of a tolerogenic signature in CLL cells in lymph nodes (LN-CLL). Based on their role in B cell biology, the progression of CLL, or immune regulation, a few genes of this 83-gene signature were selected for further analyses. We observed a significant correlation between the clinical outcomes and the expression of CAV1 (P = 0·041), FGFR1 isoform 8 (P = 0·032), PTPN6 (P = 0·031) and ZWINT (P < 0·001). CAV1, a molecule involved in the regulation of tumour progression in other cancers, was seven-fold higher in LN-CLL cells compared to BM- and PB-CLL cells. Knockdown of CAV1 expression in CLL cells resulted in significantly decreased migration (P = 0·016) and proliferation (P = 0·04). When CAV1 was knocked down in B and T cell lines, we observed an inability to form immune synapses. Furthermore, CAV1 knockdown in CLL cells impaired their ability to form immune synapses with autologous T lymphocytes and allogeneic, healthy T cells. Subsequent analyses of microarray data showed differential expression of cytoskeletal genes, specifically those involved in actin polymerization. Therefore, we report a novel role for CAV1 in tumour-induced immunosuppression during the progression of CLL.

Proteomic identification of aldolase A as an autoantibody target in patients with atypical movement disorders

We tried to identify the target/s of autoantibodies to basal ganglia neurons found in a patient with hyperkinetic movement disorders (HMD) characterized by rapid, rhythmic involuntary movements or spasms in both face and neck. Patient and control sera were used in Western blot to probe mouse brain homogenates. Two-dimensional gel electrophoresis (2-DE) SDS-PAGE protein spots recognized by the patient's antibodies were excised and sequenced by mass spectrometry analysis, and the glycolytic enzyme aldolase A was identified as the antigen recognized by the patient's autoantibodies. To assess relevance and specificity of these antibodies to the identified targets as biomarkers of autoimmunity in movement disorders, autoantibody responses to the identified target were then measured by ELISA in various diseases of the central nervous system. Anti-aldolase A autoantibodies were associated mainly with HMD (7/17, 41%) and Parkinson's disease (4/30, 13%) patients, and undetectable in subjects with other inflammatory and non-inflammatory central nervous system diseases. We, thus, identified aldolase A as an autoantigen in a sub-group of patients with HMD, a clinically ill-defined syndrome. Anti-aldolase A antibodies may represent a useful biomarker of autoimmunity in HMD patients.

High expression of hematopoietic cell specific Lyn substrate-1 (HS1) predicts poor survival of B-cell chronic lymphocytic leukemia patients

B-cell chronic lymphocytic leukemia (B-CLL) is the most common leukemia in adults in western countries. HS1 protein regulates leukemic cell migration and homing, and can indirectly promote disease progression and influence patient survival. The aim of this study was to evaluate HS1 expression in CLL patients in connection with other known prognostic factors and patients' survival.

METHODS

90 untreated CLL patients were included into the study. The control group consisted of 28 healthy matched people. HS1 detection was performed by western-blotting. Mutational status of IgVH, as well as CD38 and ZAP70 expression was also analyzed.

RESULTS

HS1 expression was significantly higher in CLL patients comparing to controls. Positive correlation was shown between HS1 and: age (p=0.0454), Rai stage (p=0.0412), leukocytosis (p=0.0129) and beta-2-microglobulin (p=0.0342). Patients with lymphocyte doubling time shorter or equal to 6 months had higher expression of HS1. Patients with higher HS1 expression had shorter survival than those with lower HS1 expression (p=0.0329).

CONCLUSIONS

We showed, that high HS1 expression predicts poor survival of chronic lymphocytic leukemia patients.

The actin regulatory protein HS1 is required for antigen uptake and presentation by dendritic cells

The hematopoietic actin regulatory protein hematopoietic lineage cell-specific protein 1 (HS1) is required for cell spreading and signaling in lymphocytes, but the scope of HS1 function in Ag presentation has not been addressed. We show that dendritic cells (DCs) from HS1(-/-) mice differentiate normally and display normal LPS-induced upregulation of surface markers and cytokines. Consistent with their normal expression of MHC and costimulatory molecules, HS1(-/-) DCs present OVA peptide efficiently to CD4(+) T cells. However, presentation of OVA protein is defective. Similarly, MHC class I-dependent presentation of VSV8 peptide to CD8(+) T cells occurs normally, but cross-presentation of GRP94/VSV8 complexes is defective. Analysis of Ag uptake pathways shows that HS1 is required for receptor-mediated endocytosis, but not for phagocytosis or macropinocytosis. HS1 interacts with dynamin 2, a protein involved in scission of endocytic vesicles. However, HS1(-/-) DCs showed decreased numbers of endocytic invaginations, whereas dynamin-inhibited cells showed accumulation of these endocytic intermediates. Taken together, these studies show that HS1 promotes an early step in the endocytic pathway that is required for efficient Ag presentation of exogenous Ag by DCs.

A unique proteomic profile on surface IgM ligation in unmutated chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by a highly variable clinical course with 2 extreme subsets: indolent, ZAP70(-) and mutated immunoglobulin heavy chain gene (M-CLL); and aggressive, ZAP70(+) and unmutated immunoglobulin heavy chain (UM-CLL). Given the long-term suspicion of antigenic stimulation as a primum movens in the disease, the role of the B-cell receptor has been extensively studied in various experimental settings; albeit scarcely in a comparative dynamic proteomic approach. Here we use a quantitative 2-dimensional fluorescence difference gel electrophoresis technology to compare 48 proteomic profiles of the 2 CLL subsets before and after anti-IgM ligation. Differentially expressed proteins were subsequently identified by mass spectrometry. We show that unstimulated M- and UM-CLL cells display distinct proteomic profiles. Furthermore, anti-IgM stimulation induces a specific proteomic response, more pronounced in the more aggressive CLL. Statistical analyses demonstrate several significant protein variations according to stimulation conditions. Finally, we identify an intermediate form of M-CLL cells, with an indolent profile (ZAP70(-)) but sharing aggressive proteomic profiles alike UM-CLL cells. Collectively, this first quantitative and dynamic proteome analysis of CLL further dissects the complex molecular pathway after B-cell receptor stimulation and depicts distinct proteomic profiles, which could lead to novel molecular stratification of the disease.

An overview of chronic lymphocytic leukaemia biology

Chronic lymphocytic leukaemia (CLL) is characterised by accumulation of CD5(+) monoclonal B cells in primary and secondary lymphoid tissues. Genetic defects and stimuli originating from the microenvironment concur to the selection and expansion of the malignant clone. Several lines of evidence, including molecular and functional analysis of the monoclonal immunoglobulin, support the hypothesis that stimulation through the B-cell receptor affects life and death of leukaemic cells. The microenvironment also has a critical role in the survival and accumulation of leukaemic cells within lymphoid organs where signals delivered from the surrounding cells are likely crucial in inducing proliferation. Nevertheless, several major biological issues still remain to be solved including regulation of the balance between proliferation and survival of leukaemic cells and the links between emerging gene abnormalities and microenvironment. In this context, mouse models are helpful tools in understanding disease mechanisms and in evaluating the efficacy of novel therapeutic agents.

How the microenvironment shapes chronic lymphocytic leukemia: the cytoskeleton connection

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation in primary and secondary lymphoid tissues of CD5+ B cells that have the same B cell receptor (BCR) rearrangement. Genetic alterations and different stimuli originating from the microenvironment cooperate in the selection and expansion of the malignant clone. Molecular and functional analyses suggest that stimulation through the BCR affects the destiny of leukemic cells in terms of life or death. Microenvironmental signals are crucial for this process, inducing proliferation and leading to the survival and accumulation of leukemic cells within lymphoid organs. Nevertheless, a number of major biological issues still remain to be solved, including the relationships between cell proliferation and cell accumulation within lymphoid organs as well as the mechanisms that regulate CLL cell migration and recirculation between peripheral blood and lymphoid tissues. We focused on the role played by the cytoskeleton, given its relevance in controlling cellular shape, mobility, and homing. We hypothesize that hematopoietic cell-specific Lyn substrate 1 (HS1), a putative prognostic marker in CLL that interacts with distinct cytoskeleton adapters in leukemic B-lymphocytes, could regulate the CLL cell cytoskeleton.

Picoplatin overcomes resistance to cell toxicity in small-cell lung cancer cells previously treated with cisplatin and carboplatin

Purpose

Picoplatin is a new generation platinum designed to overcome platinum resistance. The goal of this study was to assess picoplatin anti-tumor activity and measure various cellular parameters in small-cell lung cancer (SCLC) cells resistant to cell killing by cisplatin and carboplatin.

Methods

We developed several platinum-resistant SCLC cell lines to evaluate picoplatin activity and drug resistance mechanisms in vitro. Drug cytotoxicity was measured by MTS assay. Total cellular platinum accumulation was measured by inductively coupled plasma mass spectrometry (ICP-MS). Whole genome gene expression profiling was carried out by microarray analysis.

Results

Picoplatin retained significant cytotoxic activity in platinum-resistant SCLC lines compared to cisplatin and carboplatin. Cellular picoplatin accumulation in platinum-resistant and parental cells was high relative to levels of cellular platinum found in the same cell lines after cisplatin or carboplatin treatment. Gene expression analyses revealed substantial differences in gene expression and highlighted specific annotation clusters in carboplatin-resistant cells. In addition, a similar gene expression pattern was observed in picoplatin-treated carboplatin-resistant and parental cells.

Conclusions

Our study demonstrates that picoplatin can overcome carboplatin and cisplatin resistance. The results suggest decreased platinum accumulation as a potential mechanism of platinum resistance in SCLC cells, provide candidate markers (e.g. several genes in the Hox, glutathione biosynthetic process, and MAGE families) that may serve as signatures for platinum resistance, support distinct effects of picoplatin on SCLC cells compared to other platinums, and provide a rationale to develop picoplatin for the treatment of recurrent SCLC following initial therapy with cisplatin or carboplatin.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-010-1435-5) contains supplementary material, which is available to authorized users.

Elucidating the CXCL12/CXCR4 signaling network in chronic lymphocytic leukemia through phosphoproteomics analysis

Background

Chronic Lymphocytic Leukemia (CLL) pathogenesis has been linked to the prolonged survival and/or apoptotic resistance of leukemic B cells in vivo, and is thought to be due to enhanced survival signaling responses to environmental factors that protect CLL cells from spontaneous and chemotherapy-induced death. Although normally associated with cell migration, the chemokine, CXCL12, is one of the factors known to support the survival of CLL cells. Thus, the signaling pathways activated by CXCL12 and its receptor, CXCR4, were investigated as components of these pathways and may represent targets that if inhibited, could render resistant CLL cells more susceptible to chemotherapy.

Methodology/Principal Findings

To determine the downstream signaling targets that contribute to the survival effects of CXCL12 in CLL, we took a phosphoproteomics approach to identify and compare phosphopeptides in unstimulated and CXCL12-stimulated primary CLL cells. While some of the survival pathways activated by CXCL12 in CLL are known, including Akt and ERK1/2, this approach enabled the identification of additional signaling targets and novel phosphoproteins that could have implications in CLL disease and therapy. In addition to the phosphoproteomics results, we provide evidence from western blot validation that the tumor suppressor, programmed cell death factor 4 (PDCD4), is a previously unidentified phosphorylation target of CXCL12 signaling in all CLL cells probed. Additionally, heat shock protein 27 (HSP27), which mediates anti-apoptotic signaling and has previously been linked to chemotherapeutic resistance, was detected in a subset (∼25%) of CLL patients cells examined.

Conclusions/Significance

Since PDCD4 and HSP27 have previously been associated with cancer and regulation of cell growth and apoptosis, these proteins may have novel implications in CLL cell survival and represent potential therapeutic targets. PDCD4 also represents a previously unknown signaling target of chemokine receptors; therefore, these observations increase our understanding of alternative pathways to migration that may be activated or inhibited by chemokines in the context of cancer cell survival.

HS1 has a central role in the trafficking and homing of leukemic B cells

The function of the intracellular protein hematopoietic cell-specific Lyn substrate-1 (HS1) in B lymphocytes is poorly defined. To investigate its role in migration, trafficking, and homing of leukemic B lymphocytes we have used B cells from HS1(-/-) mice, the HS1-silenced human chronic lymphocytic leukemia (CLL) MEC1 cell line and primary leukemic B cells from patients with CLL. We have used both in vitro and in vivo models and found that the lack of expression of HS1 causes several important functional effects. In vitro, we observed an impaired cytoskeletal remodeling that resulted in diminished cell migration, abnormal cell adhesion, and increased homotypic aggregation. In vivo, immunodeficient Rag2(-/-)γ(c)(-/-) mice injected with HS1-silenced CLL B cells showed a decreased organ infiltration with the notable exception of the bone marrow (BM). The leukemic-prone Eμ-TCL1 transgenic mice crossed with HS1-deficient mice were compared with Eμ-TCL1 mice and showed an earlier disease onset and a reduced survival. These findings show that HS1 is a central regulator of cytoskeleton remodeling that controls lymphocyte trafficking and homing and significantly influences the tissue invasion and infiltration in CLL.

Gene expression factors as predictors of genetic risk and survival in chronic lymphocytic leukemia

BACKGROUND

A variety of surrogate markers for genetic features and outcome have been described in chronic lymphocytic leukemia based on gene expression analyses. Previous studies mostly focused on individual markers and selected disease characteristics, which makes it difficult to estimate the relative value of the novel markers. Therefore, in the present study a comprehensive approach was chosen investigating 18 promising, partly novel expression markers in a well characterized cohort of patients with long clinical follow-up and full genetic information (IGHV status, genomic abnormalities).

DESIGN AND METHODS

Expression markers were evaluated using real-time quantitative reverse transcriptase polymerase chain reaction in CD19(+)-purified samples from 151 patients. Multivariate analyses were performed to test the markers' ability to identify patients at genetic risk and as prognostic markers in the context of established prognostic factors.

RESULTS

For individual markers, ZAP70 expression provided the highest rate (81%) of correct assignment of patients at genetic risk (IGHV unmutated, V3-21 usage, 11q- or 17p-), followed by LPL and TCF7 (76% both). The assignment rate was improved to 88% by information from a four-gene combination (ZAP70, TCF7, DMD, ATM). In multivariate analysis of treatment-free survival, IGHV mutation status and expression of ADAM29 were of independent prognostic value besides disease stage. With regards to overall survival, expression of ATM, ADAM29, TCL1, and SEPT10 provided prognostic information in addition to that derived from clinical and genetic factors.

CONCLUSIONS

Gene expression markers are suitable for screening but not as surrogates for the information from genetic risk factors. While many individual markers may be associated with outcome, only a few are of independent prognostic significance. With regard to prognosis estimation, the genetic prognostic factors cannot be replaced by the expression markers.

Intrinsic and extrinsic factors influencing the clinical course of B-cell chronic lymphocytic leukemia: prognostic markers with pathogenetic relevance

B-cell chronic lymphocytic leukemia (CLL), the most frequent leukemia in the Western world, is characterized by extremely variable clinical courses with survivals ranging from 1 to more than 15 years. The pathogenetic factors playing a key role in defining the biological features of CLL cells, hence eventually influencing the clinical aggressiveness of the disease, are here divided into "intrinsic factors", mainly genomic alterations of CLL cells, and "extrinsic factors", responsible for direct microenvironmental interactions of CLL cells; the latter group includes interactions of CLL cells occurring via the surface B cell receptor (BCR) and dependent to specific molecular features of the BCR itself and/or to the presence of the BCR-associated molecule ZAP-70, or via other non-BCR-dependent interactions, e.g. specific receptor/ligand interactions, such as CD38/CD31 or CD49d/VCAM-1. A putative final model, discussing the pathogenesis and the clinicobiological features of CLL in relationship of these factors, is also provided.

New molecular markers in resistant B-CLL

B-chronic lymphocytic leukemia (B-CLL) is characterized by a highly variable clinical course which has long remained a stumbling block for clinicians. This variability appears to arise from complex molecular alterations identified in malignant cells from patient subsets. Recent studies have focused in particular on identifying new molecular markers to help predict the most effective and adapted treatments. In addition to the mutation status of immunoglobulin variable heavy-chain region (IgVH) genes, which is a well-established predictive factor in B-CLL, these new markers include defects of cell factors involved in the maintenance of genome stability, such as telomere function, DNA repair, ATM and p53. Other predictive factors, such as tyrosine kinase Zap-70 and soluble factors found in patient sera, may be associated with B-cell receptor signal transduction. Interestingly, an alteration of these factors fits closely, though not strikingly, with the absence of somatic mutations in IgVH genes, suggesting that the latter may be due either to epigenetic events leading to an unstable genome or to an inherited defect in the immune response of malignant B-cells. Recent lessons from Zap-70 expression/phosphorylation suggest that some of these markers may reflect the defective pathways in B-CLL cells rather than being markers of cell malignancy per se. Furthermore, specific subsets of markers are found in patient cells resistant to treatment. Current studies on gene expression profiling and proteomic analyses should soon lead to a better understanding of how these pathways are affected, especially in multi-drug resistant B-CLL.

Geldanamycin-induced Lyn dissociation from aberrant Hsp90-stabilized cytosolic complex is an early event in apoptotic mechanisms in B-chronic lymphocytic leukemia

Lyn, a tyrosine kinase belonging to the Src family, plays a key role as a switch molecule that couples the B-cell receptor to downstream signaling. In B-CLL cells, Lyn is overexpressed, anomalously present in the cytosol, and displays a high constitutive activity, compared with normal B lymphocytes. The aim of this work was to gain insights into the molecular mechanisms underlying these aberrant properties of Lyn, which have already been demonstrated to be related to defective apoptosis in B-cell chronic lymphocytic leukemia (B-CLL) cells. Herein, Lyn is described to be in an active conformation as integral component of an aberrant cytosolic 600-kDa multiprotein complex in B-CLL cells, associated with several proteins, such as Hsp90 through its catalytic domain, and HS1 and SHP-1L through its SH3 domain. In particular, Hsp90 appears tightly bound to cytosolic Lyn (CL), thus stabilizing the aberrant complex and converting individual transient interactions into stable ones. We also demonstrate that treatment of B-CLL cells with geldanamycin, an Hsp90 inhibitor already reported to induce cell death, is capable of dissociating the CL complex in the early phases of apoptosis and thus inactivating CL itself. These data identify the CL complex as a potential target for therapy in B-CLL.

Novel insights in chronic lymphocytic leukemia: are we getting closer to understanding the pathogenesis of the disease?

Chronic lymphocytic leukemia (CLL) has unique epidemiologic, biologic, and clinical features. The progressively emerging picture leads us to consider that the critical genes for malignant CLL cells are those regulated by a number of microRNAs revealed by refined cytogenetic and molecular studies, and that the key molecule is the B-cell receptor (BCR). The hypothesis that CLL cells might be selected by some sort of antigenic pressure is strengthened by numerous findings indicating that a BCR-mediated stimulation plays a relevant role in the natural history of the disease and that autoantigens, as well as molecular structures instrumental in eliminating and scavenging apoptotic cells and pathogenic bacteria, may be relevant in triggering and/or facilitating the evolution of CLL. An important question is whether the tiny monoclonal B-cell populations phenotypically similar to CLL (that occur in the peripheral blood of about 3.5% of healthy individuals and are termed monoclonal B lymphocytosis) might be a critical step in the development of CLL. All relevant events of CLL occur in tissues in which a number of cellular and molecular interactions shape a microenvironment conducive to the accumulation of malignant cells and favor the organization of proliferating cells in focal aggregates of variable size that form the pseudofollicular proliferation centers. Given the impact that understanding the pathogenesis of CLL might have on the development of new treatments, the purposes of this review are to discuss whether the novel insights in CLL are leading us closer to understanding the tenet of the disease; to define the emerging new, stimulating questions; and to unfold the major challenges that still need to be addressed.

An Integrated Strategy in Two-Dimensional Electrophoresis Analysis Able to Identify Discriminants Between Different Clinical Conditions

Two-dimensional gel electrophoresis (2DE) is an indispensable tool in proteomics for the analysis of protein expression in complex biological systems such as cells and tissues. However, the automatic extraction of information from gel images is still a challenging task. In this paper we propose a strategy that represents a computational procedure of support to the discrimination of different clinical conditions associated with the samples. The analyzed gel images were acquired within the framework of a study of peripheral neuropathies: twenty-four 2DE maps generated from cerebrospinal fluid (16 pathologic and 8 control subjects) were processed. Quantitative features were defined to describe each image and treated with a method of dimensionality reduction. The informativeness of the descriptors allowed us to see the gel of the data set as items in a three-dimensional space, segregating according to the clinical conditions. Moreover, information with prognostic value was obtained for a single outsider gel of a patient who was included in a clinical subgroup at the first diagnosis but whose disease progressed with clinical features belonging to a different clinical subgroup. The method developed may represent an effective tool of classification that can be used repeatedly to capture the essential impression from separation images.