Constitutive activation of the Wnt canonical pathway in mantle cell lymphoma

Metadherin contributes to the pathogenesis of diffuse large B-cell lymphoma

Background

Metadherin (MTDH) has been demonstrated as a potentially crucial mediator of various types of human malignancies. However, the expression and role of MTDH in diffuse large-B-cell lymphoma (DLBCL) have not been reported yet. This study aimed to illuminate the role of MTDH in the pathogenesis of DLBCL.

Methodology/Principal Findings

A remarkable elevation of MTDH on mRNA level was detected in DLBCL tissues by quantitative polymerase chain reaction (PCR). Using Western-blot analysis we found that the expression of MTDH protein was significantly upregulated in DLBCL cell lines and DLBCL tissues compared with peripheral blood mononuclear cells (PBMCs) from healthy samples and tissues from patients of reactive hyperplasia of lymph node. The results showed high expression of MTDH in 23 of 30 (76.67%) DLBCL tissues by using immunohistochemical analysis and the over expression of MTDH was strongly correlated to the clinical staging of patients with DLBCL (P<0.05). Furthermore, the finding suggested that the increase of MTDH in DLBCL cells could distinctly enhance cell proliferation and inhibit cell apoptosis; meanwhile, inhibition of MTDH expression by specific siRNA clearly enhanced LY8 cell apoptosis. Upregulation of MTDH elevated the protein level of total β-catenin and translocation of β-catenin to the nucleus directly or indirectly. Knockdown of MTDH decreased the level of total, cytoplasmic β-catenin and reduced nuclear accumulation of β-catenin protein. This indicated that the function of MTDH on the development of DLBCL was mediated through regulation of Wnt/β-catenin signaling pathway.

Conclusions/Significance

Our results suggest that MTDH contributes to the pathogenesis of DLBCL mediated by activation of Wnt/β-catenin pathway. This novel study may contribute to further investigation on the useful biomarkers and potential therapeutic target in the DLBCL patients.

Large-scale analysis of DNA methylation in chronic lymphocytic leukemia

AIMS

B-cell chronic lymphocytic leukemia (CLL) is a heterogeneous malignancy that clinically ranges from indolent to rapidly progressive. CLL, like other cancers, can be affected by epigenetic alterations.

MATERIALS & METHODS

A microarray discovery-based study was initiated to determine DNA methylation in CLL cases with a range of CD38 expression (1–92%).

RESULTS

Many loci were either methylated or unmethylated across all CD38 levels, but differential methylation was also observed for some genes. Genomic sequencing of DLEU7 confirmed extensive cytosine methylation preferentially in patient samples with low CD38 expression, whereas NRP2, SFRP2 and ADAM12 were more commonly methylated in those with high CD38 expression.

CONCLUSION

This study demonstrates that CLL is affected by CpG island methylation in some genes that segregate with CD38 expression levels, while most others show similar methylation patterns across all levels. The CpG island methylation in certain functional gene groups and pathway-associated genes that are known to be deregulated in CLL provides additional insights into the CLL methylome and epigenetic contribution to cellular dysfunction. It will now be useful to investigate the effectiveness of epigenetic therapeutic reversal of these alterations to develop effective treatments for the disease.

Genome-wide miRNA profiling of mantle cell lymphoma reveals a distinct subgroup with poor prognosis

miRNA deregulation has been implicated in the pathogenesis of mantle cell lymphoma (MCL). Using a high-throughput quantitative real-time PCR platform, we performed miRNA profiling on cyclin D1-positive MCL (n = 30) and cyclin D1-negative MCL (n = 7) and compared them with small lymphocytic leukemia/lymphoma (n = 12), aggressive B-cell lymphomas (n = 138), normal B-cell subsets, and stromal cells. We identified a 19-miRNA classifier that included 6 up-regulated miRNAs and 13 down regulated miRNA that was able to distinguish MCL from other aggressive lymphomas. Some of the up-regulated miRNAs are highly expressed in naive B cells. This miRNA classifier showed consistent results in formalin-fixed paraffin-embedded tissues and was able to distinguish cyclin D1-negative MCL from other lymphomas. A 26-miRNA classifier could distinguish MCL from small lymphocytic leukemia/lymphoma, dominated by 23 up-regulated miRNAs in MCL. Unsupervised hierarchical clustering of MCL patients demonstrated a cluster characterized by high expression of miRNAs from the polycistronic miR17-92 cluster and its paralogs, miR-106a-363 and miR-106b-25, and associated with high proliferation gene signature. The other clusters showed enrichment of stroma-associated miRNAs, and also had higher expression of stroma-associated genes. Our clinical outcome analysis in the present study suggested that miRNAs can serve as prognosticators.

Blockade of fatty acid synthase triggers significant apoptosis in mantle cell lymphoma

Fatty acid synthase (FASN), a key player in the de novo synthetic pathway of long-chain fatty acids, has been shown to contribute to the tumorigenesis in various types of solid tumors. We here report that FASN is highly and consistently expressed in mantle cell lymphoma (MCL), an aggressive form of B-cell lymphoid malignancy. Specifically, the expression of FASN was detectable in all four MCL cell lines and 15 tumors examined. In contrast, benign lymphoid tissues and peripheral blood mononuclear cells from normal donors were negative. Treatment of MCL cell lines with orlistat, a FASN inhibitor, resulted in significant apoptosis. Knockdown of FASN expression using siRNA, which also significantly decreased the growth of MCL cells, led to a dramatic decrease in the cyclin D1 level. β-catenin, which has been previously reported to be upregulated in a subset of MCL tumors, contributed to the high level of FASN in MCL cells, Interesting, siRNA knock-down of FASN in turn down-regulated β-catenin. In conclusion, our data supports the concept that FASN contributes to the pathogenesis of MCL, by collaborating with β-catenin. In view of its high and consistent expression in MCL, FASN inhibitors may hold promises for treating MCL.

Overexpression of LEF1 predicts unfavorable outcome in adult patients with B-precursor acute lymphoblastic leukemia

Aberrant activation of the Wnt pathway plays a pathogenetic role in various tumors and has been associated with adverse outcome in acute lymphoblastic leukemia (ALL). LEF1, a key mediator of Wnt signaling, has been linked to leukemic transformation, and recurrent mutations of LEF1 have been identified in pediatric T-ALL. Here we evaluated the prognostic significance of LEF1 expression in B-precursor ALL patients. LEF1 expression was determined by quantitative real-time RT-PCR in 282 adult B-precursor ALL patients treated on 06/99 and 07/03 GMALL trials. Patients were grouped into quartiles (Q1-Q4) according to LEF1 expression levels (LEF1 high, Q4; n = 71; LEF1 low, Q1-Q3; n = 211). Patients with high LEF1 expression had a significantly shorter relapse-free survival (RFS) compared with low LEF1 expressers (5-year RFS: LEF1 high, 27%; LEF1 low, 47%; P = .05). Importantly, high LEF1 expression was also associated with inferior RFS in standard-risk patients and was independently predictive for RFS (P = .02) in multivariate analyses for this subgroup. Thus, high LEF1 expression identifies B-precursor ALL patients with inferior RFS, supporting a pathogenetic role of Wnt signaling in ALL. Standard-risk patients with high LEF1 expression might benefit from early treatment modifications and new molecular therapies, including agents targeting the Wnt pathway.

Influence of five potential anticancer drugs on wnt pathway and cell survival in human biliary tract cancer cells

BACKGROUND

The role of Wnt signalling in carcinogenesis suggests compounds targeting this pathway as potential anti-cancer drugs. Several studies report activation of Wnt signalling in biliary tract cancer (BTC) thus rendering Wnt inhibitory drugs as potential candidates for targeted therapy of this highly chemoresistant disease.

METHODS

In this study we analysed five compounds with suggested inhibitory effects on Wnt signalling (DMAT, FH535, myricetin, quercetin, and TBB) for their cytotoxic efficiency, mode of cell death, time- and cell line-dependent characteristics as well as their effects on Wnt pathway activity in nine different BTC cell lines.

RESULTS

Exposure of cancer cells to different concentrations of the compounds results in a clear dose-dependent reduction of viability for all drugs in the order FH535 > DMAT > TBB > myricetin > quercetin. The first three substances show high cytotoxicity in all tested cell lines, cause a direct cytotoxic effect by induction of apoptosis and inhibit pathway-specific signal transduction in a Wnt transcription factor reporter activity assay. Selected target genes such as growth-promoting cyclin D1 and the cell cycle progression inhibitor p27 are down- and up-regulated after treatment, respectively.

CONCLUSIONS

Taken together, these data demonstrate that the small molecular weight inhibitors DMAT, F535 and TBB have a considerable cytotoxic and possibly Wnt-specific effect on BTC cell lines in vitro. Further in vivo investigation of these drugs as well as of new Wnt inhibitors may provide a promising approach for targeted therapy of this difficult-to-treat tumour.

Increased incidence of endometrioid tumors caused by aberrations in E-cadherin promoter of mismatch repair-deficient mice

Loss of E-cadherin expression is a critical step in the development and progression of gynecological tumors. Study of the precise role of E-cadherin has been hampered by the lack of satisfactory mouse model for E-cadherin deficiency. Likewise, DNA mismatch repair (MMR) is implicated in gynecological tumorigenesis, but knockout of MMR in mice predominantly causes hematologic neoplasms. Here, we show that combined disruption of E-cadherin and DNA MMR pathways increases incidence of endometrioid tumors in mice. Twenty percent of mice knockout for Msh2 enzyme and hemizygous for E-cadherin [Msh2(-/-)/Cdh1(+/-)] developed endometrioid-like tumors in the ovary, uterus and genital area. Characteristic of these tumors was a complete loss of E-cadherin expression. Sequence analysis of E-cadherin promoter region demonstrated that the loss of E-cadherin expression is caused by inactivating mutations, implying that E-cadherin is a mutational target in Msh2-deficient mice. In addition, Msh2(-/-)/Cdh1(+/-) mice showed a reduction in overall survival as compared with their Msh2(-/-) counterparts due to the development of more aggressive lymphomas, suggesting a specific role of E-cadherin in lymphomagenesis. In conclusion, Msh2(-/-)/Cdh1(+/-) mice provide a good model of gynecological tumorigenesis and may be useful for testing molecular target-specific therapies.

Mantle cell lymphoma

MCL is a well-characterized clinically aggressive lymphoma with a poor prognosis. Recent research findings have slightly improved the outcome of this neoplasm. The addition of rituximab to conventional chemotherapy has increased overall response rates, but it does not improve overall survival with respect to chemotherapy alone. The use of intensive frontline therapies including rituximab and consolidated by ASCT ameliorates response rate and prolongs progression-free survival, but any impact on survival remains to be proven. Furthermore, the optimal timing, cytoreductive regimen and conditioning regimen, and the clinical implications of achieving a disease remission even at molecular level remain to be elucidated. The development of targeted therapies as the consequence of better dissection of pathogenetic pathways in MCL might improve the outcome of conventional chemotherapy in most patients and spare the toxicity of intense therapy in a minority of MCL patients characterized by a relatively indolent disease. Patients not eligible for intensive regimens, such as hyperC-VAD, may be considered for less demanding therapies, such as the combination of rituximab either with CHOP or with purine analogues, or bendamustine. Allogeneic SCT can be an effective option for relapsed disease in patients who are fit enough and have a compatible donor. Maintenance rituximab may be considered after response to immunochemotherapy for relapsed disease, although there are currently no data to recommend this approach as the first-line strategy. As the optimal approach to the management of MCL is still evolving, it is critical that these patients be enrolled in clinical trials to identify better treatment options.

Flavonoids: potential Wnt/beta-catenin signaling modulators in cancer

Flavonoids are polyphenolic compounds found throughout the plant kingdom. They occur in every organ but are usually concentrated in leaves and flowers. During the last two decades, in vitro and in vivo studies demonstrated that flavonoids have inhibitory effects on human diseases through targeting of multiple cellular signaling components. Wnt/β-catenin signaling regulates proliferation, differentiation and fate specification in developmental stages and controls tissue homeostasis in adult life. For these reasons, this pathway has received great attention in the last years as potential pathway involved in distinct Human pathologies. In this review we discuss the emerging potential mechanisms for flavonoids on Wnt/β-catenin signaling in cancer and possible investigation strategies to understand flavonoids mode of action on this signaling pathway.

Canonical Wnt signaling promotes the proliferation and neurogenesis of peripheral olfactory stem cells during postnatal development and adult regeneration

The mammalian olfactory epithelium (OE) has a unique stem cell or progenitor niche, which is responsible for the constant peripheral neurogenesis throughout the lifespan of the animal. However, neither the signals that regulate the behavior of these cells nor the lineage properties of the OE stem cells are well understood. Multiple Wnt signaling components exhibit dynamic expression patterns in the developing OE. We generated Wnt signaling reporter TOPeGFP transgenic mice and found TOPeGFP activation predominantly in proliferating Sox2(+) OE basal cells during early postnatal development. FACS-isolated TOPeGFP(+) OE basal cells are required, but are not sufficient, for formation of spheres. Wnt3a significantly promotes the proliferation of the Sox2(+) OE sphere cells. Wnt-stimulated OE sphere cells maintain their multipotency and can differentiate into most types of neuronal and non-neuronal epithelial cells. Also, Wnt activators shift the production of differentiated cells toward olfactory sensory neurons. Moreover, TOPeGFP(+) cells are robustly increased in the adult OE after injury. In vivo administration of Wnt modulators significantly alters the regeneration potential. This study demonstrates the role of the canonical Wnt signaling pathway in the regulation of OE stem cells or progenitors during development and regeneration.

Constitutive activation of metalloproteinase ADAM10 in mantle cell lymphoma promotes cell growth and activates the TNFα/NFκB pathway

One of the main functions of A Disintegrin and Metalloproteinase 10 (ADAM10) is to regulate the bioavailability of adhesion molecules and ligands to various cellular-signaling receptors. Constitutive activation of ADAM10 has been implicated in the pathogenesis of several types of solid tumors. In this study, we found that mantle cell lymphoma (MCL) cell lines and all 12 patient samples examined expressed the active/mature form of ADAM10. In contrast, PBMCs from healthy donors (n = 5) were negative. Using immunohistochemistry, ADAM10 was readily detectable in 20 of 23 (87%) MCL tumors, but absent in 5 reactive tonsils. Knockdown of ADAM10 using short interfering RNA (siRNA) in MCL cells significantly induced growth inhibition and cell-cycle arrest, and these changes were correlated with down-regulation of cyclin D1, up-regulation of p21(waf1), and significant reductions in the TNFα production/transcriptional activity of NFκBp65. The addition of recombinant ADAM10 to MCL cells led to the opposite biologic effects. Lastly, down-regulation of ADAM10 using siRNA enhanced the growth-suppressing effects mediated by the proteasome inhibitors MG132 and bortezomib. We conclude that constitutive activation of ADAM10 contributes to the growth of MCL and therefore inhibition of ADAM10 may be a useful strategy to enhance the response of MCL to other therapeutic agents.

Interleukin 22 signaling promotes cell growth in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a specific type of aggressive B-cell non-Hodgkin lymphoma. We recently found that IL-22RA1, one of the two subunits of the interleukin 22 (IL-22) receptor, is expressed in MCL cell lines but not benign lymphocytes. In view of normal functions of IL-22 signaling, we hypothesized that the aberrant expression of IL-22RA1 may contribute to the deregulation of various cell signaling pathways, thereby promoting cell growth in MCL. In this study, we first demonstrated the expression of IL-22RA1 in all three MCL cell lines and eight frozen tumors examined using reverse transcription-polymerase chain reaction and Western blot analysis. In support of the concept that IL-22 signaling is biologically important in MCL, we found that MCL cells treated with recombinant IL-22 had a significant increase in cell growth that was associated with STAT3 activation. To investigate the mechanism underlying the aberrant expression of IL-22RA1, we analyzed the gene promoter of IL-22RA1, and we found multiple binding sites for NF-κB, a transcriptional factor strongly implicated in the pathogenesis of MCL. Pharmacologic inhibition of NF-κB resulted in a substantial reduction in the level of IL-22RA1 protein expression in MCL cells. To conclude, IL-22RA is aberrantly expressed in MCL, and we have provided evidence that IL-22 signaling contributes to the pathogenesis of MCL.

β-catenin is constitutively active and increases STAT3 expression/activation in anaplastic lymphoma kinase-positive anaplastic large cell lymphoma

BACKGROUND

The role of β-catenin in cancer has been most studied in tumors of epithelial cell origin. The functional status and biological significance of this protein in anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma is unknown.

DESIGN AND METHODS

ALK-positive anaplastic large cell lymphoma cell lines and patients' tumor samples were examined for status of β-catenin expression and signaling. The subcellular localization of β-catenin was assessed using immunohistochemistry, sub-cellular fractionation and confocal microscopy, while its transcriptional activity was studied using the TOPFlash/FOPFlash luciferase reporter assay. To examine the biological significance of β-catenin, short interfering RNA was used to knock-down its expression; the resulting biological effects were studied using trypan-blue exclusion and MTS assay, and the impact on its various downstream targets was assessed using quantitative real-time polymerase chain reaction and western blots.

RESULTS

β-catenin was transcriptionally active in three of three ALK-positive anaplastic large cell lymphoma cell lines, and this finding correlates with the nuclear localization of β-catenin in these cells and the neoplastic cells identified in most of the patients' tumor samples. β-catenin is biologically significant in ALK-positive anaplastic large cell lymphoma, since down-regulation of β-catenin resulted in a significant reduction in their cell growth. Down-regulation of β-catenin led to a marked reduction in both the total protein level and the activated/phosphorylated form of STAT3, another signaling protein previously shown to be important in the pathogenesis of ALK-positive anaplastic large cell lymphoma. In contrast to some of the oncogenic tyrosine kinases, modulation of nucleophosmin-anaplastic lymphoma kinase expression did not result in any detectable change in the protein level, nuclear localization or tyrosine phosphorylation of β-catenin; however, inhibition of nucleophosmin-anaplastic lymphoma kinase expression significantly down-regulated the transcriptional activity of β-catenin.

CONCLUSIONS

β-catenin signaling is constitutively active in ALK-positive anaplastic large cell lymphoma and represents a previously unknown mechanism by which the high levels of STAT3 expression and activation in these tumors are sustained. Our results suggest that the interaction between oncogenic tyrosine kinases and various cell signaling proteins may be more complex than previously believed.

Mantle cell lymphoma: biology, pathogenesis, and the molecular basis of treatment in the genomic era

Mantle cell lymphoma (MCL) is a B-cell non-Hodgkin lymphoma of which at least a subset arises from antigen-experienced B cells. However, what role antigen stimulation plays in its pathogenesis remains ill defined. The genetic hallmark is the chromosomal translocation t(11;14) resulting in aberrant expression of cyclin D1. Secondary genetic events increase the oncogenic potential of cyclin D1 and frequently inactivate DNA damage response pathways. In combination these changes drive cell-cycle progression and give rise to pronounced genetic instability. Several signaling pathways contribute to MCL pathogenesis, including the often constitutively activated PI3K/AKT/mTOR pathway, which promotes tumor proliferation and survival. WNT, Hedgehog, and NF-κB pathways also appear to be important. Although MCL typically responds to frontline chemotherapy, it remains incurable with standard approaches. Proteasome inhibitors (bortezomib), mTOR inhibitors (temsirolimus), and immunomodulatory drugs (lenalidomide) have recently been added to the treatment options in MCL. The molecular basis for the antitumor activity of these agents is an area of intense study that hopefully will lead to further improvements in the near future. Given its unique biology, relative rarity, and the difficulty in achieving long-lasting remissions with conventional approaches, patients with MCL should be encouraged to participate in clinical trials.

Role of Wnt canonical pathway in hematological malignancies

Wnt canonical signaling pathway plays a diverse role in embryonic development and maintenance of organs and tissues in adults. It has been observed that Wnt/β-catenin signaling pathway is involved in the pathogenesis of many carcinomas. Moreover, Wnt/β-catenin pathway has been revealed to be associated with angiogenesis. Wnt canonical pathway signaling has great potential as a therapeutic target. It has been disclosed that some hematological malignancies, such as chronic lymphocytic leukemia, mantle cell lymphoma, may occur partly due to the constitutive activation of Wnt canonical signaling pathway. This review will summarize the latest development in Wnt canonical signaling pathway and its roles in tumorigenesis and angiogenesis.

Clinical and biological significance of GSK-3β inactivation in breast cancer-an immunohistochemical study

Glycogen synthase kinase 3β, recently found to be functionally abnormal in various types of human disease, is negatively regulated by the PI3K/Akt signaling pathway. As Akt is constitutively activated in a subset of breast cancer, we hypothesized that glycogen synthase kinase 3β is inappropriately inactivated in these cases. In this study, we aimed to assess (1) the overall frequency of glycogen synthase kinase 3β inactivation in breast cancer; (2) whether there is an association between Akt activation and glycogen synthase kinase 3β inactivation; and (3) whether there is a correlation between glycogen synthase kinase 3β inactivation and various pathologic and clinical parameters. The phosphorylated form of glycogen synthase kinase 3β (pGSK-3β) and Akt (pAkt) were used as surrogate markers for glycogen synthase kinase 3β inactivation and Akt activation, respectively. Immunohistochemistry applied to paraffin-embedded tissues was used to assess 72 consecutive invasive mammary carcinomas, of which 50 were estrogen receptor positive. Overall, pGSK-3β and pAkt were positive in 34 (47.2%) and 35 (48.6%) cases, respectively. These 2 markers were significantly correlated with each other in the overall group and in the estrogen receptor-positive subgroup (P = .01 and .003, Spearman, respectively). Importantly, pGSK-3β, but not pAkt, significantly correlated a worse clinical outcome in this cohort (P = .004, log rank). In summary, evidence of glycogen synthase kinase 3β inactivation was found in approximately half of the invasive mammary carcinomas. Our data suggest that this abnormality is likely attributed to Akt activation and that glycogen synthase kinase 3β inactivation confers a worse clinical outcome.

Temsirolimus in the treatment of relapsed and/or refractory mantle cell lymphoma

Patients with mantle cell lymphoma (MCL) have a poor prognosis; consequently, new therapeutic approaches, such as rapamycin and its derivates, mammalian target of rapamycin (mTOR) inhibitors, are warranted. Temsirolimus (also known as CCI-779), a dihydroester of rapamycin, in MCL cell lines inhibited mTOR, downregulated p21 and v-Raf, and induced autophagy. The first clinical trial in MCL patients was performed using 250 mg of temsirolimus weekly for 6-12 cycles. The overall response rate was 38%; the median time to progression was 6.5 months, median overall survival was 12 months, and the median duration of response was 6.9 months. At lower dose (25 mg/week), the overall response rate was 41%, median overall survival was 14 months, and time to progression was 6 months. In another trial, 162 patients were randomly assigned to receive temsirolimus at 2 different doses (175 mg/week for 3 weeks, then 75 mg or 25 mg/week) or a treatment chosen by the investigator among the most frequently adopted single agents for treatment of relapsed MCL. Patients treated with 175/75 mg of temsirolimus had significantly higher response rates and longer progression-free survival than those treated with investigator's choice therapy. These data support the use of mTOR inhibitors for the treatment of MCL, probably in combination with other agents, such as antiangiogenic drugs or histone acetylase inhibitors.

Biological and clinical significance of GSK-3beta in mantle cell lymphoma--an immunohistochemical study

GSK-3beta, a biologically important signalling protein, is regulated by the Wnt canonical and the PI3K/Akt pathways. We recently reported that mantle cell lymphoma (MCL) frequently shows evidence of GSK-3beta inactivation, since GSK-3beta is phoshorylated at its functionally critical serine 9 residue in all MCL cell lines and the majority of MCL tumors examined. To further assess the clinical and biological significance of GSK-3beta inactivation in MCL, we employed immunohistochemistry to assess the expression of the phosphorylated/inactive form of GSK-3beta (pGSK-3beta) in 83 paraffin-embedded tumors, and correlated its expression with various biological and clinical parameters. Dichotomizing pGSK-3beta into 2 groups produced twenty-seven (32.5%) tumors assessed as negative and fifty-six (67.5%) as positive. Positive pGSK-3beta expression correlated significantly with positive nuclear expression of beta-catenin and high expression of cyclin D1 (p = 0.0025, 0.0032 Fisher's exact, respectively), both of which have been previously shown to be regulated by GSK-3beta regarding their expression levels and/or sub cellular localization in-vitro. However, no significant correlation was found between pGSK-3beta and Ki67. Of the clinical parameters, continuous pGSK-3beta status had a significant correlation with absolute lymphocyte count in blood (p = 0.0011, Spearman) and negative pGSK-3beta expression was significantly correlated with a longer overall survival (p= 0.045, HR = 1.89), but not with age at diagnosis, clinical stage or the international prognostic index. To conclude, our results support the concept that GSK-3beta inactivation, found in approximately two-thirds of MCL tumors, is biologically and clinically important in MCL.

Epigenetic dysregulation of secreted Frizzled-related proteins in multiple myeloma

We analysed the clinical impact of epigenetic dysregulation of the Wnt pathway in malignant plasma cell disorders. In multiple myeloma (MM) cell lines, aberrant promoter hypermethylation of the secreted Frizzled-related protein (SFRP) genes was a common event, and hypermethylation of SFRP1,-2 and -5 was associated with transcriptional silencing. Among 76 primary patient samples, the frequency of aberrant methylation was 35.5% for SFRP1, 52.6% for SFRP2, 1.3% for SFRP4 and 6.9% for SFRP5. Hypermethylation of SFRP1 and -2 genes was detected in monoclonal gammopathy of undetermined significance and all MM stages including plasma cell leukaemia (PCL), while SFRP5 methylation was restricted to advanced MM stages and PCL. Our data indicate that epigenetic silencing of Wnt antagonists is an early event in MM pathogenesis and that SFRP5 hypermethylation may play a role in disease progression.