B-chronic lymphocytic leukemia: practical aspects

The Role of the Tumor Suppressor Gene Protein Tyrosine Phosphatase Gamma in Cancer

Members of the Protein Tyrosine Phosphatase (PTPs) family are associated with growth regulation and cancer development. Acting as natural counterpart of tyrosine kinases (TKs), mainly involved in crucial signaling pathways such as regulation of cell cycle, proliferation, invasion and angiogenesis, they represent key parts of complex physiological homeostatic mechanisms. Protein tyrosine phosphatase gamma (PTPRG) is classified as a R5 of the receptor type (RPTPs) subfamily and is broadly expressed in various isoforms in different tissues. PTPRG is considered a tumor-suppressor gene (TSG) mapped on chromosome 3p14-21, a region frequently subject to loss of heterozygosity in various tumors. However, reported mechanisms of PTPRG downregulation include missense mutations, ncRNA gene regulation and epigenetic silencing by hypermethylation of CpG sites on promoter region causing loss of function of the gene product. Inactive forms or total loss of PTPRG protein have been described in sporadic and Lynch syndrome colorectal cancer, nasopharyngeal carcinoma, ovarian, breast, and lung cancers, gastric cancer or diseases affecting the hematopoietic compartment as Lymphoma and Leukemia. Noteworthy, in Central Nervous System (CNS) PTPRZ/PTPRG appears to be crucial in maintaining glioblastoma cell-related neuronal stemness, carving out a pathological functional role also in this tissue. In this review, we will summarize the current knowledge on the role of PTPRG in various human cancers.

Activation of Protein Tyrosine Phosphatase Receptor Type γ Suppresses Mechanisms of Adhesion and Survival in Chronic Lymphocytic Leukemia Cells

The regulatory role of protein tyrosine kinases in β₁- and β₂-integrin activation and in the survival of chronic lymphocytic leukemia (CLL) cells is well established. In contrast, the involvement of protein tyrosine phosphatases in CLL biology was less investigated. We show that selective activation of the protein tyrosine phosphatase receptor type γ (PTPRG) strongly suppresses integrin activation and survival in leukemic B cells isolated from patients with CLL. Activation of PTPRG specifically inhibits CXCR4- as well as BCR-induced triggering of LFA-1 and VLA-4 integrins and mediated rapid adhesion. Triggering of LFA-1 affinity is also prevented by PTPRG activity. Analysis of signaling mechanisms shows that activation of PTPRG blocks chemokine-induced triggering of JAK2 and Bruton's tyrosine kinase protein tyrosine kinases and of the small GTP-binding protein RhoA. Furthermore, activated PTPRG triggers rapid and robust caspase-3/7-mediated apoptosis in CLL cells in a manner quantitatively comparable to the Bruton's tyrosine kinase inhibitor ibrutinib. However, in contrast to ibrutinib, PTPRG-triggered apoptosis is insensitive to prosurvival signals generated by CXCR4 and BCR signaling. Importantly, PTPRG activation does not trigger apoptosis in healthy B lymphocytes. The data show that activated PTPRG inhibits, at once, the signaling pathways controlling adhesion and survival of CLL cells, thus emerging as a negative regulator of CLL pathogenesis. These findings suggest that pharmacological potentiation of PTPRG tyrosine-phosphatase enzymatic activity could represent a novel approach to CLL treatment.

CXCR4- and BCR-triggered integrin activation in B-cell chronic lymphocytic leukemia cells depends on JAK2-activated Bruton's tyrosine kinase

Bruton's tyrosine kinase (BTK) regulates the B-cell receptor (BCR) signaling pathway, which, in turn, plays a critical role in B-cell chronic lymphocytic leukemia (B-CLL) pathogenesis. The BTK-specific inhibitor Ibrutinib blocks BCR signaling and is now approved as effective B-CLL therapy. Chemokines, such as the homeostatic chemokine CXCL12, play a central role in B-CLL pathogenesis and progression, by regulating CLL cell interaction with the stromal microenvironment, leading to cells survival and proliferation. In this study, we investigated, in normal versus CLL B-lymphocytes, the role of BTK in signal transduction activated by the CXCL12-CXCR4 signaling axis and its involvement in rapid integrin activation. We show that BTK is rapidly activated by CXCL12 in healthy as well as CLL B-lymphocytes, with a kinetic of tyr-phosphorylation coherent with rapid adhesion triggering. BTK inhibition prevents CXCL12-induced triggering of lymphocyte function-associated antigen-1 (LFA-1) and very late antigen-4 (VLA-4) integrins. Furthermore, BTK inhibition blocks the activation of the small GTP-binding protein RhoA, controlling integrin affinity. Very importantly, we show that BTK tyr-phosphorylation and activation by CXCL12 depends on upstream activation of JAK2 tyrosine kinase. A comparative analysis of 36 B-CLL patients demonstrates that JAK2-dependent BTK regulatory role on integrin activation by CXCL12 is fully conserved in CLL cells. Finally, we show that the JAK2-BTK axis also regulates signaling to integrin activation by BCR. Thus, BTK and JAK protein tyrosine kinases (PTKs) manifest a hierarchical activity both in chemokine- as well as BCR-mediated integrin activation and dependent adhesion, potentially suggesting the possibility of combined therapeutic approaches to B-CLL treatment.

JAK2 tyrosine kinase mediates integrin activation induced by CXCL12 in B-cell chronic lymphocytic leukemia

Chemokines participate to B-cell chronic lymphocytic leukemia (B-CLL) pathogenesis by promoting cell adhesion and survival in bone marrow stromal niches and mediating cell dissemination to secondary lymphoid organs. In this study we investigated the role of JAK protein tyrosine kinases (PTK) in adhesion triggering by the CXC chemokine CXCL12 in normal versus CLL B-lymphocytes. We demonstrate that CXCL12 activates JAK2 in normal as well as CLL B-lymphocytes, with kinetics consistent with rapid adhesion triggering. By using complementary methodologies of signal transduction interference, we found that JAK2 mediates CXCL12-triggered activation of lymphocyte function-associated antigen-1 (LFA-1) and very late antigen-4 (VLA-4) integrins. We also show that JAK2 mediates the activation of the small GTP-binding protein RhoA, in turn controlling LFA-1 affinity triggering by CXCL12. Importantly, comparative analysis of 41 B-CLL patients did not evidence JAK2 functional variability between subjects, thus suggesting that JAK2, differently from other signaling events involved in adhesion regulation in B-CLL, is a signaling molecule downstream to CXCR4 characterized by a conserved regulatory role. Our results reveal JAK2 as critical component of chemokine signaling in CLL B-lymphocytes and indicate JAK inhibition as a potentially useful new pharmacological approach to B-CLL treatment.

Apoptotic and proliferative characteristics of proliferation centers in lymph node sections of patients with chronic lymphocytic leukemia

We have analyzed the immunohistochemical expression of a wide range of molecules along with the proliferation rate separately in the proliferation centers (PCs) and in the rest of the tumor area, in lymph node or spleen sections of patients with chronic lymphocytic leukemia (CLL). Fas, FasL and c-FLIP were observed both within and outside the PCs in all cases. However, only the difference in FasL expression between the PCs and the non-PC areas attained statistical significance. Median survivin expression in the PCs was higher compared to the non-PC areas. Cleaved caspase 3 was expressed at very low levels both within and outside PCs, while BCL-2 protein was expressed at high levels in all cases in both tumor compartments. Multivariate analysis demonstrated that concurrent overexpression of Fas/FasL/c-FLIP in the PCs was correlated with worse outcome for progression-free survival as well as for overall survival.

Novel Bruton's tyrosine kinase inhibitors currently in development

Bruton’s tyrosine kinase (Btk) is intimately involved in multiple signal-transduction pathways regulating survival, activation, proliferation, and differentiation of B-lineage lymphoid cells. Btk is overexpressed and constitutively active in several B-lineage lymphoid malignancies. Btk has emerged as a new antiapoptotic molecular target for treatment of B-lineage leukemias and lymphomas. Preclinical and early clinical results indicate that Btk inhibitors may be useful in the treatment of leukemias and lymphomas.

FISH Analysis for del6q21 and del17p13 in B-cell Chronic Lymphocytic Leukemia in Iranians

BACKGROUND

B-cell chronic lymphocytic leukemia (B-CLL) is the most common leukemia in the Western world. Major progress has been made in assessing typical chromosomal abnormalities and recognition of the correlation of these chromosomal abnormalities with laboratory features and clinical course of the disease. The most frequent genomic changes are deletions at 13q14, 11q22-23 and 17p13 and trisomy of chromosome 12.

OBJECTIVES

The aim of this study was to investigate the frequency of chromosomal aberrations in B-CLL patients' peripheral blood and/or bone marrow using a molecular cytogenetic method, interphase fluorescence in situ hybridization (I-FISH) and to evaluate the correlation between these genomic changes and clinical findings.

PATIENTS AND METHODS

I-FISH analyses were performed on bone marrow and blood samples of 66 B-CLL patients.

RESULTS

Deletion of 17p13 was found in 11 (16.6%) and deletion 6q21 was present in 5 (7.5%). Statistical analyses were performed to investigate the correlation of these molecular-cytogenetic findings with family history, Rai staging and CD38 marker. No clear differences in distribution was noted for del17p13 and del6q21 among patients with and without family history, and no direct correlation was noted between these genomic changes and CD38 marker, but the correlation of del17p13 and Rai stage was significant. There was a high frequency of Rai stage II within del17p13 patients.

CONCLUSIONS

It was demonstrated that the presence of del6q21 in B-CLL patients indicates poor prognosis and on the contrary, presence of del17p13 points at the good prognostic value of the disease.

Optimizations of the naïve-Bayes classifier for the prognosis of B-Chronic Lymphocytic Leukemia incorporating flow cytometry data

Prognosis of B-Chronic Lymphocytic Leukemia (B-CLL) remains a challenging problem in medical research and practice. While the parameters obtained by flow cytometry analysis form the basis of the diagnosis of the disease, the question whether these parameters offer additional prognostic information still remains open. In this work, we attempt to provide computer-assisted support to the clinical experts of the field, by deploying a classification system for B-CLL multiparametric prognosis that combines various heterogeneous (clinical, laboratory and flow cytometry) parameters associated with the disease. For this purpose, we employ the naïve-Bayes classifier and propose an algorithm that improves its performance. The algorithm discretizes the continuous classification attributes (candidate prognostic parameters) and selects the most useful subset of them to optimize the classification accuracy. Thus, in addition to the high classification accuracy achieved, the proposed approach also suggests the most informative parameters for the prognosis. The experimental results demonstrate that the inclusion of flow cytometry parameters in our system improves prognosis.

Comparative analysis of normal versus CLL B-lymphocytes reveals patient-specific variability in signaling mechanisms controlling LFA-1 activation by chemokines

Activation of lymphocyte function-associated antigen-1 (LFA-1) by chemokines is fine-tuned by inside-out signaling mechanisms responsible for integrin-mediated adhesion modulation. In the present study, we investigated the possibility of qualitative variability of signaling mechanisms controlling LFA-1 activation in chronic lymphocytic leukemia (CLL) cells. We pursued a multiplexed comparative analysis of the role of the recently described chemokine-triggered rho-signaling module in human normal versus CLL B-lymphocytes. We found that the rho-module of LFA-1 affinity triggering is functionally conserved in normal B-lymphocytes. In contrast, in malignant B-lymphocytes isolated from patients with B-CLL, the role of the rho-module was not maintained, showing remarkable differences and variability. Specifically, RhoA and phospholipase D1 were crucially involved in LFA-1 affinity triggering by CXCL12 in all analyzed patients. In contrast, Rac1 and CDC42 involvement displayed a consistent patient-by-patient variability, with a group of patients showing LFA-1 affinity modulation totally independent of Rac1 and CDC42 signaling activity. Finally, phosphatidylinositol-4-phosphate 5-kinase isoform 1gamma (PIP5KC) was found without any regulatory role in all patients. The data imply that the neoplastic progression may completely bypass the regulatory role of Rac1, CDC42, and PIP5KC, and show a profound divergence in the signaling mechanisms controlling integrin activation in normal versus neoplastic lymphocytes, suggesting that patients with CLL can be more accurately evaluated on the basis of the analysis of signaling mechanisms controlling integrin activation. Our findings could potentially affect the diagnosis, prognosis, and therapy of CLL disorders.

Fluorescencein situHybridization Detection of Cytogenetic Abnormalities in B-cell Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma

Routine cytogenetic analysis of B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma (B-CLL/SLL) frequently fails to identify an abnormal clone due to the low rate of spontaneous mitoses and poor response to mitogen stimulation. Recent studies utilizing interphase fluorescence in situ hybridization (FISH) suggest that prognostically significant chromosomal abnormalities occur more frequently in B-CLL/SLL than has been previously recognized. The purpose of this study was to compare the chromosomal abnormalities detected by karyotyping and FISH in cases of B-CLL/SLL, and to correlate these with clinical features and survival. Seventy-two cases were studied for chromosome 3, 12 or 18 aneuploidy, and for rearrangements involving 11q13, 11q23, 13q14, 14q32 and 17p13. The median age of the patients was 54 years (range, 30-87 years). Clinical staging of B-CLL patients showed that 70% of the patients were Rai stage 0, 1, or 2, and 30% stage 3 or 4. Karyotyping identified chromosomal abnormalities in 31% of the cases, whereas FISH studies were abnormal in 72% of cases including 64% of the cases with normal karyotypes. The most common abnormalities were deletion 13q14 (46%), trisomy 12 (21%), and 14q32 rearrangements (21%). At diagnosis, patients with trisomy 12 were more likely to have a high LDH (P = 0.04), but no other significant differences in the clinical or laboratory features, Rai stage, or survival were found among patients with normal cytogenetics vs. those with chromosomal abnormalities. Univariate analysis showed that B-symptoms (P = 0.044), anemia (P = 0.0006), absolute lymphocytosis > or = 30,000/mm3 (P = 0.029), and Rai stage 3 or 4 (P = 0.0038) at initial presentation were associated with an increased risk of death, but only Rai stage 3 or 4 (P = 0.0038) was significant in multivariate analysis. Interphase FISH studies improve the cytogenetic diagnosis when performed in conjunction with karyotyping in B-CLL/SLL, but the prognostic relevance of various abnormalities could not be confirmed in this study.

Analysis of the immunoglobulin heavy chain variable region gene expression in Iranian patients with chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (B-CLL) results from clonal expansion of phenotypically mature but functionally immature B-lymphocytes. The incidence of this type of leukemia is low in Asian countries, whereas it is the most frequent type of leukemia in the West. Previous investigations mainly conducted in Western populations have demonstrated non-random rearrangement of certain immunoglobulin variable region heavy (VH) and/or light (VL) chain genes in different groups of B-CLL patients. Little is known about the profile of VH gene expression in Asian patients. In the present study, we determined the frequency of VH gene family usage in 59 Iranian patients with B-CLL. VH gene family of patients was determined by reverse transcriptase-polymerase chain reaction using VH1-VH7 family specific primers. The most frequently expressed VH gene family was found to be VH3 (45.8%) followed by VH4 (32.2%), VH1 (18.6%), VH5 (1.7%) and VH6 (1.7%), with no expression of VH2 and VH7 gene families. The results indicate a lower representation of the VH1 and VH2 gene families and a higher representation of the VH4 gene family in Iranian B-CLL patients compared to Western patients, suggesting involvement of ethnic and/or environmental factors in B-CLL disease initiation.

Chronic lymphocytic leukemia: diagnosis and treatment

Traditionally, the goal of therapy in chronic lymphocytic leukemia (CLL) has been palliative, with first-line therapy using alkylating agents and/or involved field radiotherapy (depending on the stage of disease and sites of involvement) because of the older age of affected patients and the low rate of complete remissions (CRs) with no improvement in overall survival despite treatment. With increasing knowledge about the biology, molecular genetics, and prognostic factors of the disease, the philosophy of care for patients with CLL has evolved from palliation to aiming for a potential cure, especially in younger patients. Furthermore, multiple treatment options have emerged, including purine analogues, monoclonal antibodies, and potentially stem cell transplantation. These have been associated with higher frequencies of CRs and longer durations of responses compared to conventional chemotherapy. In addition, a subset of patients treated with chemoimmunotherapy can achieve durable CRs and molecular remissions. This may translate into improved disease-free survival and potentially a "cure." Because of the heterogeneous nature of CLL, new prognostic markers are currently being incorporated into clinical trials to determine their role in routine clinical practice. This review summarizes current therapeutic regimens that are being evaluated in patients with CLL and management of disease-related complications.

MMP-9 in B-cell chronic lymphocytic leukemia is up-regulated by alpha4beta1 integrin or CXCR4 engagement via distinct signaling pathways, localizes to podosomes, and is involved in cell invasion and migration

B-cell chronic lymphocytic leukemia (B-CLL) progression is determined by malignant cell extravasation and lymphoid tissue infiltration. We have studied the role and regulation of matrix metalloproteinase-9 (MMP-9) in B-CLL cell migration and invasion. Adhesion of B-CLL cells to the fibronectin fragment FN-H89, VCAM-1, or TNF-alpha-activated human umbilical vein endothelial cells (HUVECs) up-regulated MMP-9 production, measured by gelatin zymography. This effect was mediated by alpha4beta1 integrin and required PI3-K/Akt signaling. The chemokine CXCL12 also up-regulated MMP-9, independently of alpha4beta1 and involving ERK1/2 but not Akt activity. Accordingly, alpha4beta1 engagement activated the PI3-K/Akt/NF-kappaB pathway, while CXCL12/CXCR4 interaction activated ERK1/2/c-Fos signaling. Anti-MMP-9 antibodies, the MMP-9 inhibitor TIMP-1, or transfection with 3 different MMP-9 siRNAs significantly blocked migration through Matrigel or HUVECs. Cell-associated MMP-9 was mainly at the membrane and contained the proactive and mature forms. Moreover, B-CLL cells formed podosomes upon adhesion to FN-H89, VCAM-1, or fibronectin; MMP-9 localized to podosomes in a PI3-K-dependent manner and degraded a fibronectin/gelatin matrix. Our results are the first to show that MMP-9 is physiologically regulated by alpha4beta1 integrin and CXCL12 and plays a key role in cell invasion and transendothelial migration, thus contributing to B-CLL progression. MMP-9 could therefore constitute a target for treatment of this malignancy.

Rap1 signal controls B cell receptor repertoire and generation of self-reactive B1a cells

We previously reported that the mice deficient for SPA-1, a Rap1 GTPase-activating protein, developed hematopoietic stem cell disorders. Here, we demonstrate that SPA-1(-/-) mice show an age-dependent increase in B220(high) B1a cells producing anti-dsDNA antibody and lupus-like nephritis. SPA-1(-/-) peritoneal B1 cells revealed the altered Vkappa gene repertoire, including skewed Vkappa4 usage and the significant Igkappa/Iglambda isotype inclusion indicative of extensive receptor editing. Rap1GTP induced OcaB gene activation via p38MAPK-dependent Creb phosphorylation, and consistently, SPA-1(-/-) immature BM B cells showing high Rap1GTP exhibited the augmented expression of OcaB and Vkappa4 genes. SPA-1(-/-) BM cells could transfer the autoimmunity in association with the generation of peritoneal B220(high) B1a cells in Rag-2(-/-) recipients. Finally, a portion of SPA-1(-/-) mice developed B1 cell leukemia with hemolytic autoantibody. Present results suggest that the regulated Rap1 signal in the immature B cells plays a role in modifying the B cell receptor repertoire and in maintaining the self-tolerance.

Minimal change glomerulonephritis in chronic lymphocytic leukemia: pathophysiological and therapeutic aspects

BACKGROUND

So far, only 9 cases of minimal change glomerulonephritis (MCGN) related to chronic lymphocytic leukemia (CLL) have been described.

CASE REPORT

Our patient presented with severe nephrotic syndrome. Diagnostic biopsies confirmed MCGN and early-stage BCLL (Binet A). In contrast to previously described cases, kappa monoclonal IgM and cryoglobulins were also detected. The patient was treated with chlorambucil and prednisone. 3 weeks later, renal function and white blood cell (WBC) count were completely normal.

DISCUSSION

Although, in most cases, renal disease and CLL present separately, there is evidence for a causal relationship between the two disorders. Although it is widely approved that early-stage CLL should not be treated by medication, the severe nephrotic syndrome in our patient required immediate intervention. So far, there is no standard therapy for MCGN associated with CLL. Our combination therapy resulted in normalization of the nephrotic syndrome and the WBC count. Hence, we emphasize the importance of early recognition of renal symptoms in CLL and propose a successful therapy for nephrotic syndrome in MCGN associated with early-stage B-CLL. Additionally, the pathophysiological and therapeutic aspects of MCGN associated with CLL are retrospectively discussed.

Constitutive and activation-inducible cyclooxygenase-2 expression enhances survival of chronic lymphocytic leukemia B cells

We recently reported that activated normal human B lymphocytes express Cox-2. These findings prompted us to evaluate whether human B-CLL cells express Cox-2 and synthesize prostaglandins. In contrast to naive human B cells, B-CLL cells constitutively expressed Cox-2 protein and produced PGE2, PGF2alpha, and TXA2. Elevated Cox-2 expression was seen in a subgroup of B-CLL cells that exhibit poor prognostic factors, including unmutated variable heavy chain status and increased CD38 expression. Furthermore, stimulation of B-CLL cells with CD40 ligand plus TNFalpha increased Cox-2 levels. The role of Cox-2 in promoting B-CLL survival was investigated using nonselective and selective Cox-2 inhibitors. Significant reductions in B-CLL survival occurred following Cox-2 inhibition. These new findings support that constitutive Cox-2 expression in B-CLL cells promotes their survival and possibly their expansion in vivo. It will therefore be important to evaluate drugs that inhibit Cox-2 as potential therapeutic agents in B-CLL in vivo.

Aberrant expression of TRAIL in B chronic lymphocytic leukemia (B-CLL) cells

Analysis of peripheral blood (>85% CD19+/CD5+ B) lymphocytes, obtained from 44 patients affected by B chronic lymphoid leukemia (B-CLL), showed that surface TNF-related apoptosis inducing ligand (TRAIL) was expressed in all samples and at higher levels with respect to unfractionated lymphocytes and purified CD19+ B cells, obtained from 15 normal blood donors. Of note, in a subset of B-CLL samples, the addition to B-CLL cultures of a TRAIL-R1-Fc chimera, which binds at high affinity to surface TRAIL, significantly decreased the percentage of viable cells with respect to untreated control B-CLL cells, suggesting that surface TRAIL may play an unexpected role in promoting B-CLL cell survival. In spite of the majority of B-CLL lymphocytes expressed variable surface levels of "death receptors" TRAIL-R1 and TRAIL-R2, the addition in culture of recombinant TRAIL increased (>20% vs. controls) the degree of spontaneous apoptosis in only 11/44 of the B-CLL samples, had no effect in 19/44, while it significantly increased leukemic cell survival in 14/44. Taken together, these findings suggest that an aberrant expression of TRAIL might contribute to the pathogenesis of B-CLL by promoting the survival in a subset of B-CLL cells.

Potential pathogenetic implications of cyclooxygenase-2 overexpression in B chronic lymphoid leukemia cells

Evidence suggests that cyclooxygenase-2 (COX-2) increases tumorigenic potential by promoting resistance to apoptosis. Because B chronic lymphoid leukemia (B-CLL) cells exhibit a defective apoptotic response, we analyzed CD19(+) B lymphocytes purified from the peripheral blood of B-CLL patients. Microarray analysis showed a variable (up to 38-fold) increase in the steady-state mRNA levels of COX-2 in B-CLL lymphocytes compared with normal CD19(+) B lymphocytes. The up-regulation of COX-2 in B-CLL cells was confirmed by reverse transcriptase-polymerase chain reaction and Western blot analyses. Moreover, immunohistochemical analysis of B-CLL bone marrow infiltrates confirmed clear expression of COX-2 in leukemic cells. Ex vivo treatment with the COX-2 inhibitor NS-398 significantly decreased the survival of leukemic cells by increasing the rate of spontaneous apoptosis in 13 of 16 B-CLL samples examined, but it did not affect the survival of normal lymphocytes. Pretreatment with NS-398 significantly potentiated the cytotoxicity induced by chlorambucil in 8 of 16 B-CLL samples examined. Moreover, although recombinant tumor necrosis factor-related apoptosis inducing ligand (TRAIL)/Apo2L showed little cytotoxic effect in most B-CLL samples examined, pretreatment with NS-398 sensitized 8 of 16 B-CLL samples to TRAIL-induced apoptosis. Taken together, our data indicate that COX-2 overexpression likely represents an additional mechanism of resistance to apoptosis in B-CLL and that pharmacological suppression of COX-2 might enhance chemotherapy-mediated apoptosis.

Incidence of chromosomal anomalies detected with FISH and their clinical correlations in B-chronic lymphocytic leukemia

B-chronic lymphocytic leukemia (B-CLL) is the most common adult leukemia. Molecular genetic characterization of B-CLL has made significant progress and typical chromosomal anomalies have been assessed. The most frequent chromosomal abnormalities are deletions at 13q14, 17p13, and 11q22 approximately q23 and trisomy 12. The aim of this study was to establish incidence of chromosomal changes in bone marrow or peripheral blood cells (or both) of B-CLL patients using a molecular cytogenetic method, interphase fluorescence in situ hybridization (I-FISH), and to evaluate the prognostic implications. We performed I-FISH on bone marrow and blood smears from 217 B-CLL patients (124 male, 93 female). Trisomy 12 was found in 35 of the 217 (16%); deletion 13q14 was analyzed in 207 patients and found in 112 (54%). Deletion 17p13 was found in 34 (16%) out of 206 examined. Deletion of 11q23 was analyzed in 56 patients and was present in 7 (12%). Statistical analyses were performed to correlate the molecular-cytogenetic findings with disease status (stable versus progressive), Rai stage, CD38/CD19 antigen coexpression, immunoglobulin variable heavy chain (IgV(H)) mutational pattern, and other clinical and laboratory parameters. No apparent differences in distribution were noted for anomalies +12, del(13)(q14), or del(17)(p13) among patients with stable and progressive disease, and no consistent pattern in the distribution of type of genomic changes were found among various Rai stages and in CD38/CD19-positive or -negative patients. Patients without IgV(H) mutation had a worse prognosis; however, distribution of chromosomal abnormalities identified with FISH was the same for patients with and without IgV(H) mutations.

A novel CDK inhibitor, CYC202 (R-roscovitine), overcomes the defect in p53-dependent apoptosis in B-CLL by down-regulation of genes involved in transcription regulation and survival

B-cell chronic lymphocytic leukemia (B-CLL) is a clinically variable disease where mutations in DNA damage response genes ATM or TP53 affect the response to standard therapeutic agents. The in vitro cytotoxicity of a novel cyclin-dependent kinase inhibitor, CYC202, was evaluated in 26 B-CLLs, 11 with mutations in either the ATM or TP53 genes, and compared with that induced by ionizing radiation and fludarabine. CYC202 induced apoptosis within 24 hours of treatment in all 26 analyzed tumor samples independently of ATM and TP53 gene status, whereas 6 of 26 B-CLLs, mostly ATM mutant, showed marked in vitro resistance to fludarabine-induced apoptosis. Compared with B-CLLs, normal T and B lymphocytes treated with CYC202 displayed reduced and delayed apoptosis. Using global gene expression profiling, we found that CYC202 caused a significant down-regulation of genes involved in regulation of transcription, translation, survival, and DNA repair. Furthermore, induction of apoptosis by CYC202 was preceded by inhibition of RNA polymerase II phosphorylation, leading to down-regulation of several prosurvival proteins. We conclude that CYC202 is a potent inducer of apoptosis in B-CLL regardless of the functional status of the p53 pathway, and may be considered as a therapeutic agent to improve the outcome of resistant B-CLL tumors.

Rap1 and SPA-1 in hematologic malignancy

Rap1 is a member of the Ras family of GTPases and, depending on the cellular context, has an important role in the regulation of proliferation or cell adhesion. In lymphohematopoietic tissues, SPA-1 is a principal Rap1 GTPase-activating protein. Mice that are deficient for the SPA-1 gene develop age-dependent progression of T-cell immunodeficiency followed by a spectrum of late onset myeloproliferative disorders, mimicking human chronic myeloid leukemia. Recent studies reveal that deregulated Rap1 activation in SPA-1-deficient mice causes enhanced expansion of the bone marrow hematopoietic progenitors, but induces progressive unresponsiveness or anergy in T cells. Rap1 and its regulator, SPA-1, could, therefore, provide unique molecular targets for the control of human hematologic malignancy.

Lysophosphatidic acid (LPA) protects primary chronic lymphocytic leukemia cells from apoptosis through LPA receptor activation of the anti-apoptotic protein AKT/PKB

Lysophosphatidic acid (LPA) protects epithelial and fibroblast cell lines from apoptosis. In B-cells, LPA acts as a growth factor promoting cell proliferation. Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of CD19+/CD5+ B-lymphocytes primarily through a block in apoptosis. The mechanisms underlying this defect are not fully understood. We investigated whether LPA could be a survival factor in CLL cells. Herein, we demonstrate that LPA protects B-cell lines BJAB and I-83 and primary CLL cells but not normal B-cells from fludarabine- and etoposide-induced apoptosis. Furthermore, LPA prevented spontaneous apoptosis in primary CLL cells. The LPA1 expression was found to be increased in primary CLL cells compared with normal B-cells correlating with LPA prevention of apoptosis. Treatment of primary CLL cells with the LPA receptor antagonist, diacylglycerol pyrophosphate, reverses the protective effect of LPA against apoptosis, and down-regulation of the LPA1 by siRNA blocked LPA-mediated protection against spontaneous apoptosis in primary CLL cells. The protective effect of LPA was inhibited by blocking activation of the phosphatidylinositol 3-kinase/AKT signaling pathway. These results indicate that LPA is a survival factor in B-cell lines and primary CLL cells but not normal B-cells. Thus, drugs targeting the LPA receptors might be an effective therapy against B-cell-derived malignancies such as CLL.

Amifostine stimulates the formation of hematopoietic bone marrow progenitors from B-cell chronic lymphocytic leukemia

Amifostine is a phosphorylated aminothiol that not only protects hematopoietic progenitor cells from chemotherapy and radiotherapy, but also stimulates normal hematopoiesis. The effect of amifostine on the in vitro growth of hematopoietic progenitors derived from B-cell chronic lymphocytic leukemia(B-CLL) was investigated. The colony-forming units (CFU)-granulocyte macrophage (CFU-GM), the burst-forming units-erythroid (BFU-E) and the CFU-granulocyte erythroid macrophage megakaryocytes (CFU-GEMM) increased 38, 20 and 100%, respectively, after the incubation with amifostine. There was no statistical difference in the in vitro progenitor growth of patients grouped according to their disease stage, bone marrow lymphocytic infiltration or therapy. Our data indicate that apart from cytoprotection the parallel use of amifostine and chemotherapy in patients with B-CLL could enhance bone marrow recovery.

Membranous glomerulonephritis in chronic lymphocytic leukemia

We present a case of chronic lymphocytic leukemia associated with nephrotic syndrome. Renal biopsy revealed membranous glomerulonephritis accompanied by interstitial monoclonal lymphocytic infiltration. Combination therapy with cyclophosphamide, vincristine, and prednisone (COP) was successful in inducing an effective response in chronic lymphocytic leukemia. Improvement of renal function and proteinuria was also observed.