Chronic lymphocytic leukemia (CLL) exhibits remarkable clinical heterogeneity likely reflecting the underlying biological heterogeneity. The genetic landscape of CLL has been recently enriched with mutations within a number of genes proposed as novel prognostic markers. Mounting evidence also supports the pivotal role of the clonotypic B-cell receptor immunoglobulin (BcR IG) in the natural history of CLL. Interestingly, almost 30% of all CLL patients can be assigned to different patient subsets, each defined by expression of a distinct stereotyped BcR IG. Whether stereotyped subsets exhibit distinct clinical behavior is still an issue of debate. The aim of this thesis was to evaluate the prognostic relevance of recurrent gene mutations and to assess the clinicobiological associations and clinical impact of BcR IG stereotypy in CLL. In a cohort of 3490 patients, NOTCH1, SF3B1 and TP53 mutations were enriched within clinically aggressive cases carrying unmutated IGHV genes (U-CLL), frequently co-occurring with trisomy 12, del(11q) and del(17p), respectively. Of note, SF3B1 mutations increased in parallel with increasing timespan between diagnosis and mutational screening. NOTCH1 mutations, SF3B1 mutations and TP53 abnormalities (TP53abs, deletions and/or mutations) correlated with shorter time-to-first-treatment among early stage cases, while in multivariate analysis, only SF3B1 mutations and TP53abs retained independent significance. In a series of 8593 CLL patients, stereotyped subsets showed marked differences in demographics, clinical presentation, cytogenetic aberrations and gene mutational spectrum. Patients within a specific subset generally followed similar clinical courses, whereas patients in different stereotyped subsets—even when displaying similar IG somatic hypermutation status— experienced significantly different clinical outcome. In particular, subset #2 (IGHV3-21/IGLV3-21), the largest overall, was found to exhibit (i) a remarkably high incidence of SF3B1 mutations (44%), alluding to subset-biased acquisition of genomic aberrations, in the context of particular antigenic stimulation; and, (ii) a dismal clinical outcome, distinct from the remaining IGHV3-21 CLL. Our findings strongly support the adverse clinical impact of SF3B1 mutations in CLL in addition to TP53abs. BcR IG stereotypy also emerges as prognostically relevant, further highlighting that an immunogenetic sub-classification of CLL based on BcR IG configuration could refine patient risk stratification.

No description available.

The ability of cancer cells to escape anti-tumor immune responses is acknowledged as one of the hallmarks of cancer. Overexpression of immunoregulatory molecules is one mechanism responsible for the immunsuppressive network that is characteristic of the tumor microenvironment. In this thesis, we investigated the role of CD200, a potent immunoregulatory molecule, in Chronic Lymphocytic Leukemia. We showed that functional blockade of CD200 on lymphoma cells or primary CLL cells, both of which express CD200 at high levels, augmented cytotoxic killing of these cells by effector CD8+ T cells in vitro. We also identified and characterized a previously unrecognized soluble form of CD200, sCD200, present in elevated levels in CLL plasma when compared to plasma from controls. The data reported show that patients with high sCD200 levels have more aggressive disease, inferring that sCD200 may be a novel prognostic marker for CLL. The in vivo function of sCD200 was investigated for its ability to support engraftment of CLL splenocytes in NOD.SCID mice. Infusion of sCD200hi CLL plasma, but not sCD200lo normal plasma, enhanced engraftment of CLL-splenocytes in vivo, an effect which was abrogated by depletion of sCD200 from CLL plasma. The prolonged engraftment of CLL cells seen in this model (>6 months) suggests these mice represent a useful pre-clinical model for drug screening. The effect of CD200 blockade was tested in this model, and was found to be as effective in eliminating engrafted CLL cells as rituximab. Investigation of the mechanisms leading to the release of sCD200 from CLL cells showed that sCD200 was produced following ectodomain shedding by ADAM proteases and MMPs. Results from studies reported in this thesis support the hypothesis that CD200 plays a major role in CLL biology, and suggests it may represent a novel therapeutic target for CLL.

The ability of cancer cells to escape anti-tumor immune responses is acknowledged as one of the hallmarks of cancer. Overexpression of immunoregulatory molecules is one mechanism responsible for the immunsuppressive network that is characteristic of the tumor microenvironment. In this thesis, we investigated the role of CD200, a potent immunoregulatory molecule, in Chronic Lymphocytic Leukemia. We showed that functional blockade of CD200 on lymphoma cells or primary CLL cells, both of which express CD200 at high levels, augmented cytotoxic killing of these cells by effector CD8+ T cells in vitro. We also identified and characterized a previously unrecognized soluble form of CD200, sCD200, present in elevated levels in CLL plasma when compared to plasma from controls. The data reported show that patients with high sCD200 levels have more aggressive disease, inferring that sCD200 may be a novel prognostic marker for CLL. The in vivo function of sCD200 was investigated for its ability to support engraftment of CLL splenocytes in NOD.SCID mice. Infusion of sCD200hi CLL plasma, but not sCD200lo normal plasma, enhanced engraftment of CLL-splenocytes in vivo, an effect which was abrogated by depletion of sCD200 from CLL plasma. The prolonged engraftment of CLL cells seen in this model (>6 months) suggests these mice represent a useful pre-clinical model for drug screening. The effect of CD200 blockade was tested in this model, and was found to be as effective in eliminating engrafted CLL cells as rituximab. Investigation of the mechanisms leading to the release of sCD200 from CLL cells showed that sCD200 was produced following ectodomain shedding by ADAM proteases and MMPs. Results from studies reported in this thesis support the hypothesis that CD200 plays a major role in CLL biology, and suggests it may represent a novel therapeutic target for CLL.

In allogeneic stem cell mobilization, peripheral blood stem cell mobilization with filgrastim can be considered standard of care. Poor mobilizers may be at risk for inadequate stem cell collection during apheresis. He we present a successful case of salvage plerixafor use with filgrastim in a haploidentical identical transplant patient.

No description available.

Chronic Lymphocytic Leukemia (CLL) is a type of cancer that affects the B cells of the immune system causing problems in the process of producing antibodies. It can be sorted into mutated and unmutated CLL based on the percentage of somatic mutations in the Immunoglobulin Heavy chain Variable region (IgHV). The B cells of healthy individuals can be sorted into three groups; CD27dull memory B cells (MBCs), CD27bright MBCs and naïve B cells. The hypothesis for the project was that the unmutated CLL subset originates from CD27dull MBCs and the mutated CLL subset originates from CD27bright MBCs. RNA-sequencing data from healthy individuals were acquired from a collaboration partner in Rome and CLL-patients were collected from public datasets available online. Several bioinformatic tools were used to analyze the data. First, the quality of the data files was checked, then adapter sequence from the sequencing process and low-quality bases were removed (trimming). Good quality of the files was confirmed after the trimming. Secondly, these files were mapped against the human reference genome (GRCh38/hg38) for alignment, then the resulted data was used to check for genes that showed differential expression between the different groups. Results were analyzed and visualized using Venn diagrams, Principal Component Analysis (PCA) and heatmap plots and random forest. A list of 85 genes was generated based on the different comparisons and was used in one PCA plot that showed clear separation between the different groups. The SWAP70 gene was analyzed for single nucleotide polymorphisms (SNPs). The study concluded five genes that could be used as biomarkers for CLL and the diagnosis of its subtypes where some of them were discussed in previous studies. Also, the mutated CLL subset showed a similar behavior to the healthy individuals and this could validate the original hypothesis and justifies the better disease prognosis for this subtype.

Next-generation sequencing (NGS) techniques have led to major breakthroughs in the characterization of the chronic lymphocytic leukemia (CLL) genome with discovery of recurrent mutations of potential prognostic and/or predictive relevance. However, before NGS can be introduced into clinical practice, the precision of the techniques needs to be studied in better detail. Furthermore, much remains unknown about the genetic mechanisms leading to aggressive disease and resistance to treatment. Hence, in Paper I, the technical performance of a targeted deep sequencing panel including 9 genes was evaluated in 188 CLL patients. We were able to validate 143/155 (92%) selected mutations through Sanger sequencing and 77/82 mutations were concordant in a second targeted sequencing run, indicating that the technique can be introduced in clinical practice. In Paper II we screened 18 NF-κB pathway genes in 315 CLL patients through targeted deep sequencing which revealed a recurrent 4 base-pair deletion in the NFKBIE gene. Screening of NFKBIE in 377 additional cases identified the mutation in ~6% of all CLL patients. We demonstrate that the lesion lead to aberrant NF-κB signaling through impaired interaction with p65 and is associated with unfavorable clinical outcome. In Paper III we sought to delineate the genetic lesions that leads to relapse after fludarabine, cyclophosphamide, and rituximab treatment. Through whole-exome sequencing of pre-treatment and relapse samples from 41 cases we found evidence of frequent selection of subclones harboring driver mutations and subsequent clonal evolution following treatment. We also detected mutations in the ribosomal protein RPS15 in 8 cases (19.5%) and characterization of the mutations through functional assays point to impaired p53 regulation in cells with mutated RPS15. Paper IV aimed at characterizing 70 patients assigned to three major subsets (#1, #2, and #4) through whole-genome sequencing. Besides recurrent exonic driver mutations, we report non-coding regions significantly enriched for mutations in subset #1 and #2 that may facilitate future molecular studies. Collectively, this thesis supports the potential of targeted sequencing for mutational screening of CLL in clinical practice, provides novel insight into the pathobiology of aggressive CLL, and demonstrates the clinical outcome and cellular effects of NFKBIE and RPS15 mutations.

Lymphocytes from patients with B-chronic lymphocytic leukemia (B-CLL) express large numbers of P2X7 receptors for extracellular adenosine triphosphate (ATP). Activation of P2X7 receptors induces multiple downstream effects, of which the best documented is the opening of an ionic channel that is selective for divalent cations. Another effect of ATP is to induce the shedding of L-selectin (CD62L), a molecule which is involved in the adhesive interactions of lymphocytes on endothelial cells. High levels of soluble L-selectin and CD23 are found in the serum of patients with B-CLL, although the mechanisms involved in their production are poorly characterized. Because extracellular ATP causes shedding of L-selectin, we studied the effect of ATP on shedding of CD23, an adhesion molecule expressed on the surface of B-CLL lymphocytes. ATP induced the shedding of CD23 at an initial rate of 12% of that for L-selectin, while the EC50 of ATP (35 uM) and BzATP (10 uM) was identical for shedding of both molecules. Inactivation of the P2X7 receptor by pre-incubation with OxATP, an irreversible inhibitor of P2X7 purinoceptor, abolished ATP-induced shedding of both molecules. Moreover, KN-62, the most potent inhibitor for the P2X7 receptor inhibited ATP-induced shedding of both CD23 and L-selectin with the same IC50 (12 nM). Ro 31-9790, a membrane permeant zinc chelator which inhibits the phorbol-ester stimulated shedding of L-selectin also inhibited shedding of CD23 from B-CLL lymphocytes, but the IC50 was different for the two shed molecules (25 versus 1 ug/ml respectively). Although L-selectin was completely shed by incubation of cells with phorbol-ester no CD23 was lost under these conditions. Also, Ca2+ inhibits ATP-induced CD23 shedding but not L-selectin shedding. Since soluble CD23 and L-selectin are found in the serum of normal subjects and B-CLL patients, the expression of these two adhesion molecules on lymphocytes before and after transendothelial migration was studied in an in vitro model of this process. In normal and B-CLL subjects, 71�b5% of L-selectin from both T and B cells and 90% of CD23 from B cells was lost following transmigration, while the expression of a range of other adhesion molecules such as VLA-4, ICAM-1, LFA-1 and CD44 was unchanged. Lymphocytes incubated with OxATP retained their capacity for transendothelial migration and showed the same loss of L-selectin as control leukaemic lymphocytes. Ro 31-9790, which can protect ATP-induced both L-selectin and CD23 shedding, had no effect on inhibiting L-selectin and CD23 lost during transmigration. These data show the presence of a second pathway for the downregulation of L-selectin and CD23 from the lymphocyte surface. Data in vivo from 'knock-out' mice show that L-selectin is essential for the emigration of lymphocytes through high endothelial venules into lymph nodes. The migration of normal and B-CLL lymphocytes across confluent human umbilical vein endothelial monolayers was studied in an in vitro model of this process. Lymphocytes treated with ATP or BzATP showed 56�b25% or 67�b16% loss of L-selectin on the surface and 36�b24% or 64�b19% decrease of transmigration, respectively, while OxATP, which does not alter the L-selectin level, had no effect on lymphocyte transmigration. Further experiments examined this correlation between L-selectin expression and lymphocyte transendothelial migration in this model system. A quantitative assay for cell surface L-selectin showed that expression of L-selectin was lower on B-CLL lymphocytes (8,880�b5,700 molecules/cell) than on normal lymphocytes (29,500�b7,500 molecules/cell, p less than 0.001). Also the rate of transmigration of B-CLL lymphocytes (1.5�b0.9 migrated cells/HUVEC) was lower than normal peripheral lymphocytes (2.4�b0.9 migrated cells/HUVEC, p=0.04). Incubation of lymphocytes in complete medium for 24 hrs increased the expression of L-selectin on B-CLL lymphocytes by 1.5 to 2 fold while the normal lymphocyte L-selectin remained at the initial level. This upregulation of B-CLL L-selectin correlated with a 2 fold increased rate of transendothelial migration. A correlation was found between L-selectin expression on lymphocytes and their ability for transendothelial migration (r^2=0.6). This study shows that the adhesion molecules L-selectin and CD23 can be lost from lymphocytes by two different physiological pathways. One is by P2X7 receptor activation by extracellular ATP while the second is activated by transendothelial migration of these cells. A second finding is that B-CLL lymphocytes have lower level of L-selectin expression and an impaired ability for transendothelial migration compared with normal peripheral blood lymphocytes. Do these results explain the high serum levels of soluble L-selectin and CD23 observed in B-CLL? Although B-CLL lymphocytes do not recirculate as rapidly as normal peripheral blood lymphocytes, the greatly increased number of leukaemic cells in B-CLL ensures that much more soluble L-selectin and CD23 is generated during the recirculation of these cells through the body.

<p>Chronic lymphocytic leukemia (CLL) cells are considered to be derived from antigen-exposed B cells. To further explore the antigen-driven selection behind the leukemogenesis of CLL, we performed immunoglobulin (Ig) specificity screening of 7 CLL cell lines and 23 primary CLL clones from patient peripheral blood. We also included a recombinant monovalent monoclonal antibody (mAb) belonging to a subset of CLL cases with identical or semiidentical heavy chain complementarity determining region 3 (HCDR3) of the IGHV3-21 gene rearrangement. We found CLL mAb specificities against vimentin, filamin B, cofilin-1, proline-rich acidic protein 1, cardiolipin, oxidized low density lipoprotein and Streptococcus pneumoniae polysaccarides. These molecules are functionally associated with microbial infection and/or apoptotic cell removal. An antigen-driven selection would therefore imply that CLL B cell precursors are involved in the elimination and scavenging of pathogens and apoptotic cells, which could trigger the development of the disease.</p><p>The limited in vitro survival of CLL cells makes Epstein-Barr virus (EBV) immortalization of CLL cells a useful experimental model for studies on antibody-specificity screening. Considering the intricate procedure of EBV transformation of CLL cells and the many false cell lines used worldwide, we also wanted to characterize and evaluate the authentic origin of several previously established CLL cell lines and their normal lymphoblastoid counterparts. Three of the CLL cell lines tested were truly authentic (I83-E95, CLL-HG3 and CII), two had features of a biclonal Ig expression (232B4 and WaC3CD5+), one was only tentatively verified (PGA-1), whereas one cell line could not be verified (EHEB) due to lack of original patient cells for comparison. Two of the presumed normal lymphoblastoid cell lines tested were shown to be a neoplastic CLL clone. This study emphasizes the importance of proper cell line authentication and we will continue to verify additional cell lines not yet proven authentic.</p><p>In conclusion, we provide evidence for natural Ab production by CLL cells and suggest that these cells might be derived from B cell precursors involved in the innate immunity and, thus, providing a first-line-defence against pathogens and in elimination of apoptotic cells.</p>