Kay, Neil E.

Abstract One of the major mechanisms by which the immune system combats unpredictable foreign pathogens is to produce highly specific and effective antibodies by B cells. Somatic hypermutation (SHM) and class switch recombination (CSR) are two key events required for the production of highly specific and effective antibodies. Both SHM and CSR occur in the germinal center (GC), and are mediated by a common enzyme, activation-induced cytidine deaminase (AID) that specifically mutates the variable regions (IgV) and switch regions (IgS) of immunoglobulin genes by converting cytidines to uridines. It has been shown that in addition to the central deaminase domain, an N-terminal domain is essential to target SHM to the IgV region whereas a C-terminal domain is necessary for Ig CSR. Given its mutagenic nature, it has been postulated that AID may play causative roles in B cell lymphomagenesis. Consistent with this notion, AID is expressed and alternatively spliced in B cell tumors such as B-cell chronic lymphocytic leukemia (B-CLL) and non-Hodgkin’s lymphoma (NHL). However, it remains unclear whether post-GC malignant B cell AID expression and alternative splicing is a consequence of B cell transformation and/or is required to maintain growth and/or malignant B-cell survival, or whether post-GC AID expression and alternative splicing may also occur in normal B cells. To discriminate between these two possibilities, we analyzed AID expression and splicing in normal human B cells. Our data demonstrate that human tonsillar B cells prominently express the full-length AID transcript, and of interest, also express all four alternative transcripts that have been previously described in B-CLL and NHL B cells. To determine if all normal B cells express all of the AID transcripts, we performed limiting dilution of tonsillar B cells and used RT-PCR to detect AID expression. We surprisingly discovered that AID splicing variants are singly expressed by individual B-cells. To address the functional significance of each splicing variant, we considered the possibility that B cells expressing the alternative transcripts may be by-products of the normal GC reaction and are eliminated prior to GC exit. Conversely those B cells may contribute to the memory B cell pool if those AID variants are functional. Therefore, we examined AID expression and splicing in memory B cells using a more sensitive nested PCR approach. Our data show that AID is indeed expressed in peripheral blood memory cells but not in naïve B cells. Moreover, at least one splicing variant was expressed at levels comparable to the full-length AID transcript. Using limiting dilution, we again found that the full-length and alternatively spliced AID transcripts are singly expressed by individual memory B cells. Our results suggest that AID expression beyond the GC stage may play a role in sustaining selection pressure. Since the AID domains specific for SHM and CSR are encoded by different exons, we hypothesize that those variants may function differentially in SHM and CSR and this concept is under current study. Since each B cell only expressed one AID transcript, our data strongly suggest that SHM and CSR are coordinated in a stepwise process by generation of alternative AID splice variants that exhibit selective activity thereby allowing fine-tuning of humoral immunity.

Abstract The prognostic power of immunoglobulin (Ig) somatic mutation status in B cell chronic lymphocytic leukemia (B-CLL) is widely appreciated and has served as the rationale to systematically determine this molecular feature in B-CLL patients. Consistent with other reports, our study of Ig mutation status in a large cohort of B-CLL patients (n=599) found the most commonly used Ig heavy chain variable (VH) region gene was VH 1–69. The VH1–69 gene is of particular interest as there are numerous reports demonstrating that VH1–69 expressing B-CLL cells predominantly express the 51p1-like allele in an unmutated (UM) form and it is frequently associated with use of the D gene segment, D3-3; the J gene segment, JH6; and a relatively long third, complementarity-determining region (CDR3). Despite molecular definition of a commonly used form of VH1–69 in B-CLL, the clinical significance of CLL B cell usage of this prototypic form of VH1–69 remains to be determined. The goal of this study, therefore, was to perform a molecular and clinical analysis on our cohort of B-CLL patients expressing the VH1–69 gene. Our cohort consisted of 19 females and 55 males, with 89.5% expressing UM Ig VH. The 51p1-like allele was present in 75.7% of patients and the predominant D region used was D3 (64.7%). Patients in our cohort were classified by Rai risk as follows: 20 low (28.2%), 40 intermediate (56.3%), and 11 high (15.5%). For those patients with Rai stage available, analysis of specific D and J regions resulted in 16 D3-3/JH6 (26.7%); 14 D3-3/non-JH6 (23.3%); 16 non-D3-3/JH6 (26.7%); and 14 non-D3-3/non-JH6 (23.3%). Despite observing an overwhelming majority of leukemic cells with UM Ig VH, and the known relationship between mutation status and disease progression, it is interesting that our cohort included almost 30% with a low Rai risk. Of note, Ig VH mutation status did not segregate with Rai risk group or VH1–69 allele use (although few patients overall were mutated). However, an UM Ig VH status was associated with a CDR3 length >20 (p = 0.001) and with use of the JH6 segment (p = 0.003). When mutation status was analyzed in concert with specific use of the D3-3 allele, no relationship emerged; however, when this D region allele was analyzed for JH6 vs non-JH6 usage, combination of the D3-3 allele with JH6 was significantly associated with an UM Ig VH status (p = 0.004). Moreover, when J and D segment usage was analyzed in concert with Rai stage group, a significant (p = 0.019) relationship emerged between paired use of D3-3 and a JH6 segment and advanced (intermediate/high) Rai stage. Strikingly, only 1 of 18 VH1–69 patients with low Rai risk for whom D and J data were available expressed the specific combination of D3-3 and JH6. Although analysis of a larger cohort is clearly required to more formally and fully evaluate these relationships, to our knowledge, this is the first suggestion that D and J usage in VH1-69 expressing B-CLL patients correlates with advanced stages of disease. Because Ig VH usage is not believed to change over the course of disease, it is tempting to speculate that VH1–69 B-CLL patients that do not express the prototypic VH1–69 receptor may have a more favorable disease course. In summary, these data add further support to the notion that there is selection for specific Ig receptors in B-CLL and that the antigenic specificity of certain receptors may be associated with risk of progression.

Abstract Background: Results of conventional cytogenetic studies on specimens processed without B-cell mitogens are usually normal in B-CLL: this observation is often attributed to lack of mitotic B-CLL cells. Using metaphase FISH with D13S319, we now have evidence that these apparently normal mitotic B-CLL cells often exhibit submicroscopic interstitial deletions in 13q14. This observation indicates B-CLL cells do divide in unstimulated cultures, but the abnormal metaphases are not detected because the abnormalities are submicroscopic and represent a low percentage of proliferating cells. Methods: We studied 12 patients with B-CLL who had normal metaphases by conventional cytogenetics, but abnormal interphase nuclei by FISH with D13S319. This cohort consisted of 7 females and 5 males who ranged in age from 50 to 87 years. Clinical information was available for 11 patients: Rai stages were 0, I, II, III, or IV for 6, 1, 1, 2, and 1 patients, respectively; 8 patients received treatment and 3 have died. Conventional cytogenetic studies and metaphase FISH were done on bone marrow specimens that were processed by standard 24 and 48-hour unstimulated cultures with Chang Medium BMC. Interphase FISH studies were done on blood or bone marrow (collected within 3 days of specimens for conventional cytogenetic studies) using probes to detect anomalies of chromosomes 6, 11, 12, 13, 14 and 17. For each patient, metaphase FISH was done with commercial probes from Vysis Inc., Downers Grove, IL for D13S319/13q34 using leftover fixed cells from conventional cytogenetics studies. Results: Metaphase FISH results were normal for 3 bone marrow specimens: the remaining 9 specimens had 1.9 to 13.8% metaphases with interstitial deletions of 13q14. One patient had a cytogenetically visible chromosome 13 deletion in 2.2% of metaphases. In the remaining 8 specimens, the size of the abnormal 13 was similar to the normal 13 homolog and other acrocentric chromosomes. By comparison, interphase FISH revealed 13 to 93% nuclei with 13q-x1 or 13q-x2. Seven patients had additonal anomalies in their interphase nuclei; 3 had 11q-, 2 had 17p-, 1 had +12 and 1 had +IGH. Conclusions: This investigation indicates that metaphase FISH detects submicroscopic deletions in chromosome 13 as well as infrequent mitotic B-CLL cells in patients who have normal conventional cytogenetic results. Therefore, metaphase FISH is a novel and useful technique to detect abnormal mitotic cells in B-CLL in cultures without special B-cell mitogens. The prognostic significance of abnormal metaphase FISH results is still under investigation. We speculate that this method will allow for identification of more aggressive proliferating disease even in so-called “favorable” prognostic groups based on interphase FISH results.

Abstract Background: Non-Hodgkin lymphoma (NHL) is a malignancy of lymphocytes, and may develop in the setting of inflammation and immune dysfunction. Small scale evaluations have suggested that common genetic variation in candidate genes related to immune function may predispose to the development of NHL. Here we report a comprehensive analysis of variants within genes associated with immunity and inflammation and risk of NHL. Methods: We used ParAllele’s Immune and Inflammation panel of 9,412 single nucleotide polymorphisms (SNPs) from 1,450 immune/inflammation genes as a discovery tool in a clinic-based study of 458 NHL cases and 484 frequency matched controls seen at the Mayo Clinic from 2002–2005. The panel included 537 coding non-synonymous SNPs (nsSNPs), with the remainder of the SNPs selected as tags from HapMap (tagSNPs) to provide coverage of the candidate genes (r2 = 0.8 and minor allele frequency >0.05). To assess the association of individual SNPs with risk of NHL, we calculated Odds Ratios (ORs) and 95% confidence intervals, adjusted for age and gender. The most prevalent homozygous genotype was used as the reference group, and each polymorphism was modeled individually as having a log-additive effect in the regression model. Associations between haplotypes from each gene and the risk of NHL were calculated using a score test implemented in HAPLO.SCORE. We also modeled the main effects for all independent (r2 <0.25) SNPs from a gene in a multivariate logistic regression model. Results: The mean age at diagnosis was 60 years for cases and 58% were male; in controls the mean age at enrollment was 61.6 years and 55% were male. In the gene analyses, the strongest findings (p≤0.001 from multiple SNP logistic regression or haplotype analysis) were for cAMP responsive element binding protein 1 (CREB1; p=0.0004), fibrinogen alpha chain (FGA; p=0.0006), TNF receptor-associated factor 1 (TRAF1; p=0.001), dual specificity phosphatase 2 (DUSP2; p=0.001), and fibrinogen gamma chain (FGG; p=0.001). In the nsSNP analyses, the strongest findings (p≤0.01) were for integrin β3 (ITGB3) L59P (OR=0.64, 0.50–0.83), Beta-1,3-N-acetylglucosaminyltransferase 3 (B3GNT3) H328R (OR=0.72, 0.57–0.91), transporter 2, ATP-binding cassette (TAP2) T665A (OR=1.32, 1.07–1.63), HLA-B associated transcript 2 (BAT2) V1895L (OR=0.60, 0.42–0.85), and complement component 7 (C7) T587P (OR=1.39, 1.07–1.80). Conclusions. Our results suggest that genetic variability in genes associated with antigen processing (CREB1 and TAP2), lymphocyte trafficking (B3GNT3), immune activation (TRAF1, BAT2), complement and coagulation pathways (FGA, FGG, ITGB3, C7), and MAPK signaling (DUSP2) may be important in the etiology of NHL, and should be pursued in replication studies.

Abstract The monoclonal antibodies (MoAb) alemtuzumab and rituximab have proven efficacy in the treatment of CLL. In addition, alemtuzumab is effective in patients with defective p53 function responding poorly to purine analogue therapy. The action of both MoAb is not completely understood. Proposed mechanisms include complement dependent cytotoxicity (CDC), antibody dependent cellular cytotoxicity (ADCC), and direct induction of apoptosis of CLL B cells. We have done correlative studies on CLL B cells from patients enrolled in a trial of alemtuzumab and rituximab in “high risk” early stage previously untreated CLL to determine: 1. Role of apoptosis induction and CDC in each MoAb and 2. If the addition of rituximab to alemtuzumab increases their in vitro cytotoxicity. Patients and Methods: Patients with early stage, previously untreated, high risk CLL are treated with subcutaneous alemtuzumab (dose escalation over 3 days then 30 mg Mon-Wed-Fri for 4 weeks) and rituximab (375 mg/m2/dose weekly from day 8 x 4 doses). High risk disease was defined as one or more of the following features of the CLL B cell clone: (1) 17p13−; (2) 11q22−; (3) unmutated IgVH (< 2%) and either CD38+ or ZAP-70+. Blood B lymphocytes collected prior to the start of therapy were tested for response to MoAb in vitro. Cells were cultured at 2 x 106/ml in AIM-V medium using standard conditions. Alemtuzumab and rituximab were used at 20 μg/ml and complement as 10% of 40 CH50 units/ml human serum. The impact of the MoAb was measured by counting viable cells (trypan blue negative) and measuring early apoptosis (annexin V) and cell death (cell membrane permeability to propidium iodide) using flow cytometry at 1 hour, and then daily for 3 days. Results: Treatment caused rapid resolution of lymphocytosis in all 7 patients and 3 patients were negative for circulating CLL cells using a highly sensitive 3 color flow cytometry (CD5+/CD19+/CD79b-) after therapy. All patients had a clinical response (2 CR, 5 PR). Alemtuzumab and complement were rapidly cytotoxic to most CLL cells. Mean cell viability was 39% (sd: 8%) after 1 hour of incubation. Cytotoxicity was similar in all samples irrespective of FISH defects, IgVH mutation status, and in vitro resistance to F-ara-A (n = 3). Alemtuzumab was inactive in the absence of complement for all samples. Rituximab alone and together with complement did not induce cytotoxicity or apoptosis. However, the addition of rituximab to alemtuzumab and complement did increase CDC where the number of viable cells was significantly lower at 1, 24, 48, and 72 hours incubation (p = 0.075, 0.047, 0.031, 0.027, respectively, for pairwise comparisons). CLL cells surviving alemtuzumab CDC subsequently had a lower level of apoptosis than control cells, implying a selection for resistant cells. Alemtuzumab CDC on this residual population was not increased at higher concentrations of alemtuzumab or complement. This mechanism of CDC resistance is currently under investigation. Conclusion: These data suggest that alemtuzumab CDC is an important mechanism of action in patients with CLL. However, alemtuzumab CDC kills only about 61% of CLL cells in vitro, and the surviving cells are more resistant to spontaneous apoptosis. This suggests that cells that survive alemtuzimab CDC contribute to disease progression or relapse. We intend to elucidate the mechanism of this resistance using our in vitro model with the hope that treatment strategies can be deployed to remove this residual CLL B cell clone.

Abstract The IgVH mutation status is an independent predictor of time to treatment and survival in CLL. However, the biological basis of this difference is unknown. Clinical use of the IgVH mutation status as a prognostic marker is limited due to the technical difficulties of assessing this feature. As such, we probed for differences in protein expression by CLL cells with unmutated (UM) vs mutated (M) IgVH using phage peptide display libraries (PDPL). Methods: PDPL consists of phages engineered to express random peptides (7-mer) on the coat protein. From approximately 2x1011 phages displaying all possible permutations of 7-mer peptide, we selected phages binding to UM cells by incubation with 106 UM cells and elution of bound phages. Then, from numerous phages initially binding to UM cells, we subtracted phages binding to M cells by multiple incubations with M cells (106). Thus, the phages that bound only to UM cells were selected. The procedure was repeated multiple times to increase selection specificity. The peptide sequences displayed by selected phages were evaluated. We identified phage targets on UM cells by immunoprecipitation (IP) of CLL protein with specific phage and by sequencing of precipitated protein. The expression of target protein in CLL cells was confirmed by immunobloting and flow cytometry. Results: Sequencing of phages from the 3rd round of selection (UM v. M) revealed several peptides, with the most predominant being FPSAHFL. IP identified the cellular target for FPSAHFL as vimentin, an intermediate filament protein involved in cell motility and activation. The level of vimentin expressed by CLL cells varied between patient samples (n=15). UM CLL cases were found to express higher levels of vimentin (the mean MFI was 1002; SD 381), than cases of M CLL (mean MFI 547; SD 109), p=0.0128. To evaluate the prognostic significance of vimentin, we assessed vimentin expression by flow cytometry in a separate subgroup of 40 CLL patients. Archived cell samples collected between 6/2000 – 6/2001 were used. The median follow up was 81 months (40–233). Vimentin expression (MFI) as a continuous variable was a risk factor for a shortened time to treatment (TTT) with a proportional hazard ratio of 4.152 (95% CI 1.33–15.220, p=0.0317). Using MFI closest to the median (and rounded to 2 decimal places) as a cutoff, we stratified patients in high (n=21) and low (n=19) vimentin expression groups. The median times to treatment (TTT) in patients with high vs low level expression of vimentin were 2.8 and 12.9 years respectively, p=0.0025 (Fig.). Conclusion: Using novel proteomic technology, we found that CLL cells with unmutated IgVH expressed higher levels of vimentin than CLL cells with mutated IgVH. A high-level of vimentin expression defined by flow cytometry appears to be associated with high-risk disease. Validation of these findings could allow for the vimentin level to be used as a surrogate marker for expression of unmutated IgVH in CLL. Figure Figure

Abstract Background: Loss of p53 is detected by fluorescence in situ hybridization (FISH) in interphase nuclei in 8–10% of patients with B-CLL and has been associated with aggressive disease and poor response to therapy. Results of chromosome studies suggest loss of p53 is often due to structural anomalies of chromosome 17 rather than monosomy 17. To characterize chromosome 17 anomalies in B-CLL, we used interphase and metaphase FISH to study a series of patients with this disorder. Methods: We studied 16 patients with B-CLL who had chromosome 17 anomalies detected by conventional chromosome studies or interphase FISH. The study cohort consisted of 8 females and 8 males (age 54 – 73 years). Clinical data was available for 15 patients: Rai stages were I, II, III and IV for 1, 2, 6 and 6 patients, respectively; 14 patients received treatment and 10 have died. Metaphase and interphase FISH studies were performed using left-over fixed bone marrow or peripheral blood cell pellets from conventional cytogenetic studies. To identify recurrent chromosome 17 breakpoint cluster regions, patients were first studied with p53(17p13.1) and D17Z1(centromere17), and then with FISH probes for SMS(17p11.2) and RARA(17q21). For patients retaining the SMS probe site, we did FISH for HNPP(17p11.2–12) and D17Z1(centromere17). A total of 200 interphase nuclei and up to 20 metaphases were analyzed by each probe set. Results: The karyotype was normal for 3 patients and complex involving various abnormalities of chromosome 17 for the remaining 13. All patients showed loss of one p53 probe site with retention of both chromosome 17 centromeres. The SMS locus was absent in 13 patients indicating a breakpoint cluster region between the centromere and SMS probe site. In the remaining 3 patients, HNPP was absent, but the SMS probe site was retained indicating chromosome breakage between the SMS and HNPP probe sites. Metaphase FISH results indicate loss of p53 was due to an isochromosome 17p11.2 in 4 patients and an unbalanced translocation involving 17p11.2 in 12 patients. Conclusions: This study shows that loss of p53 in B-CLL cells is due to isochromosome formation or unbalanced translocations that involve a ~6,400 kb breakpoint cluster region adjacent to the centromere on the short arm of chromosome 17. Importantly, our findings indicate that loss of p53 is not due to loss of chromosome 17, simple deletions of p53, or chromosome breakage near the p53 locus. The region between the centromere and HNPP on chromosome 17 is known to be rich in low copy repeats and homologous DNA sequences are dispersed throughout the genome. In somatic cells, these repeats can result in pairing of the same or different chromosomes; crossing over within these homologous regions can result in translocations or isochromosomes. Undoubtedly, this genetic mechanism plays an important role in the origin of structural anomalies of chromosome 17 in B-CLL.

Abstract Background: Angiogenesis has been found to be an important regulator in the disease progression of both solid tumors and hematologic malignancies. In solid tumors, the balance of pro and anti-angiogenic factors appears to be a critical factor in tumorigenesis, with disturbance in favor of angiogenesis promoting tumor growth and metastasis. This observation led to the concept of an “angiogenic switch” where pro-angiogenic influences outweigh anti-angiogenic factors. Patients with CLL have detectable levels of plasma and cellular pro and anti-angiogenic cytokines as well as abnormal neovascularization in the marrow and lymph nodes. Limited studies of pro-angiogenic cytokines have suggested that inter-patient variation in serum/plasma and cellular levels of these markers may have prognostic implications. We evaluated pro- and anti-angiogenic cytokines in a large sample of patients with CLL to evaluate the presence of angiogenic switching and its implications for disease progression. Methods: In a prospective, longitudinal study, we analyzed the serum/plasma, intracellular(determined by flow cytometry), and CLL B cell secreted (24 hour medium values) levels of pro-angiogenic cytokines (VEGF, bFGF) and an anti-angiogenic cytokine (Thrombospondin [TSP]) in 311 patients with previously untreated CLL. VEGF:TSP and bFGF:TSP ratios were calculated to evaluate for evidence of angiogenic switching (higher ratio suggests a pro-angiogenic phenotype). The relationship of angiogenic cytokines to Rai stage, IgVH gene mutation status, % CD38 protein expression, and time to treatment (TTT) from the date of sample were evaluated (median follow-up=11 months). Sequential samples were available on >90% of patients and were evaluated to assess if changes in levels of angiogenic cytokines occurred in patients requiring treatment. Results: Serum, cellular, and secreted levels of VEGF, bFGF, and TSP showed no correlation with Rai stage, IgVH gene mutation (continuous variable), or % expression of CD38 (continuous variable). However, among patients with Rai stage 0-II disease, individuals with lower TSP levels (<75 percentile, p=0.007) or higher bFGF:TSP ratios (continuous variable; p=0.003) had shorter TTT (Figure 1). Similar relationships for a shorter TTT were also observed for secreted TSP levels (p=0.007) and the cellular bFGF:TSP ratio (p=0.009). On analysis of sequential samples, no clear difference in serum, cellular, or secreted levels of VEGF, bFGF, TSP, VEGF:TSP, or bFGF:TSP occurred among those who required treatment. Conclusions: Angiogenic cytokines appear to have prognostic significance in patients with previously untreated early stage CLL. Importantly, we report the original observation that the ratio of bFGF (pro-angiogenic) to TSP (anti-angiogenic) correlates with time to treatment as a continuous variable. This result provides further evidence that angiogenic switching relates to clinical progression in CLL. Longer follow-up of this cohort is needed to fully define the prognostic implications of angiogenic cytokines in CLL and determine if integration of these markers with other prognostic parameters improves risk stratification for early stage patients. Survival According to Serum Thrombospondin Level Survival According to Serum Thrombospondin Level

Abstract Background: Chronic lymphocytic leukemia (CLL) can have a profound effect on the quality of life (QOL) of patients living with the illness. To our knowledge, no studies to date have evaluated the influence of the doctor-patient relationship on patient’s emotional distress or QOL. Methods: We conducted an international, web-based survey of patients with CLL using standardized instruments to evaluate QOL. Additional questions on the survey explored how often patients thought about their disease and evaluated their satisfaction with specific aspects of their relationship with the physician caring for them. Patients were also asked to indicate what phrases their physicians had used to describe/characterize CLL. Results: Between June and October 2006, 1482 patients responded to the survey. The diagnosis of CLL was validated in a randomly selected subset of patients. Over half (55.9%; n=822) of patients reported they thought about their CLL diagnosis daily. Although the proportion of patients who thought about CLL daily decreased with time, two or more years after diagnosis over 50% of patients still thought about their disease every day. When asked to indicate their satisfaction with various aspects of the physician caring for their CLL, more than 90% (n=1340) of patients felt their doctor had a good understanding of how their disease was progressing (i.e., the stage, blood counts, lymph nodes) but only 69% (n=1024) felt their physician had a good understanding of how CLL affected their QOL (anxiety, worry, fatigue, etc.). Similarly, while 90% (n=1324) of patients felt comfortable talking to their doctor about treatment and management of CLL, only 77% (n=1134) felt comfortable talking to their doctor about how CLL affected QOL. Reported satisfaction with their physician in these areas strongly related to patients’ measured emotional and overall QOL on standardized instruments (all p<0.001). This effect on QOL remained (p<0.002) after adjustment for age, extent of co-morbid health conditions, measured fatigue, and treatment status in a regression analysis. Finally, patients were asked to indicate whether the physician caring for them had used specific phrases to describe CLL. Thirty-three percent of patients had been told “CLL is the ‘good’ leukemia,” 24% had been told “don’t worry about your CLL,” and 35% had been told “if you could pick what cancer to have, this is what you would choose.” Overall, 52% of patients had received one or more of these characterizations of CLL by their physician. The emotional and overall QOL were worse among patients who reported their physician had used these phrases to describe CLL (all p≤0.001). This effect on QOL remained after regression analysis (p<0.002). Patients whose physician had used one of these phrases to describe CLL were also less likely to feel their physician understood how CLL was effecting their QOL and to feel comfortable discussing the effects of CLL on their QOL with their physician (all p<0.001). Conclusions: Physicians play an important role helping patients adjust to the physical, intellectual, and emotional challenges of CLL. The effectiveness with which physicians accomplish these tasks appears to impact the QOL of patients with CLL. Additional studies exploring how physicians can best support patients with CLL are needed.

Abstract Background: B-chronic lymphocytic leukemia (B-CLL) is the most common leukemia in the Western world but its pathogenesis remains largely unknown. Our strategy was to employ gene expression profiling (GEP) to discover genetic differences between CLL B cells and blood B cells from healthy adults. Previously, we and others identified the transcription factor (TF) lymphocyte enhancer factor-1 (LEF-1) as one of several genes significantly over expressed in CLL B cells suggesting a role for the oncogenic Wnt signaling pathway. LEF-1 acts as a central mediator of Wnt signaling and is crucial for the proliferation and survival of pro-B cells during development. Recently, deregulated LEF-1 activation has been directly linked with leukemogenesis. Methodology: The goals of our study were to: validate LEF-1 over expression in CLL B cells in a new cohort of B-CLL patients and normal controls; study CLL B cell LEF-1 protein expression; and investigate CLL B cell expression levels of other genes linked to Wnt signaling. To accomplish these goals, Affymetrix U133 GEP was performed on B cells from 41 B-CLL patients who were enrolled on a trial of combined pentostatin, cyclophosphamide, and rituximab and 11 healthy adults over age 60. Only the perfect match data were utilized for all analyses; the non-background corrected perfect match data were normalized using an intensity-dependent procedure and analyses were done using the base-2 logarithm transformed normalized values. Results: GEP analysis confirmed CLL B cells expressed the LEF-1 gene at ~28-fold higher levels than normal B cells (p<.0001). These results were validated by quantitative PCR and all CLL B cells studied expressed LEF-1 mRNA. By contrast, LEF-1 mRNA expression was undetectable in blood B cells from healthy adults both before and after in vitro mitogenic stimulation suggesting aberrant LEF-1 expression in B-CLL. Moreover, LEF-1 protein was readily detected by flow cytometry in CLL B cell samples and all clonal B cells expressed a uniform level of LEF-1. Full length LEF-1 is more oncogenic and predominates in certain cancers, while a dominant negative short isoform is found at greater levels in normal lymphocytes. Of interest, western blot analysis revealed that CLL B cells predominantly expressed full length oncogenic LEF-1. Ongoing studies are focused on silencing LEF-1 expression to determine LEF-1 target genes. In this regard, IGFBP4 (IGF binding protein 4) mRNA expression levels are 19-fold higher in CLL vs control B cells (p<0.0001) and the IGFBP4 protein was recently shown to antagonize Wnt signaling. A scan of the IGFBP4 promoter element identified 3 possible LEF/TCF consensus sites. Thus, there is a possible negative feedback loop in CLL, with activation of the Wnt pathway leading to expression of a negative Wnt regulator. Finally, we queried the GEP data for evidence of differential expression of 63 other Wnt-related genes. Surprisingly, in addition to LEF1, only five genes met our selection threshold of ≥1.5 fold change in expression between CLL and control B cells and p value <.001. These genes were CSNK1D (casein kinase, delta 1; 1.9-fold higher in control vs CLL; p<0.0001); CCND2 (cyclin D2; 2.4-fold higher in CLL vs control; p<0.0001); JUN (3.2-fold higher in control vs CLL); WNT3 (6.4-fold higher in CLL vs control; p<0.0001); and TCF4 (transcription factor 4, alias ITF-2; 4-fold higher in CLL vs control; p<0.0001). To our knowledge, we are the first to report that the TCF4 (ITF-2) gene is over expressed in B-CLL. This TF is of great interest because it is a known downstream target of the Wnt/TCF pathway, is activated in human cancers with b-catenin defects, and it promotes neoplastic transformation. Using Spearman correlation analysis to explore the relationship between LEF1, TCF4, and WNT3 expression levels, we observed a marginal correlation between WNT3 expression and LEF1 (ρ=0.31; p value=0.05) and TCF4 (ρ=0.29; p value=0.07). Summary: These studies add new support for a critical role of the Wnt pathway in CLL. The WNT3 results are consistent with the literature; however, it is notable that we failed to corroborate other reports demonstrating that other Wnts and Fzd genes are differentially expressed in CLL B cells vs normal B cells. It is striking that CLL B cells over express two TFs in this pathway that have been linked with neoplastic transformation. Ongoing studies are aimed at further elucidating the roles of these genes in B-CLL.