Increased proteasome degradation of cyclin-dependent kinase inhibitor p27 is associated with a decreased overall survival in mantle cell lymphoma

The role of proteasomes in tumorigenesis

Protein homeostasis is the basis of normal life activities, and the proteasome family plays an extremely important function in this process. The proteasome 20S is a concentric circle structure with two α rings and two β rings overlapped. The proteasome 20S can perform both ATP-dependent and non-ATP-dependent ubiquitination proteasome degradation by binding to various subunits (such as 19S, 11S, and 200 PA), which is performed by its active subunit β1, β2, and β5. The proteasome can degrade misfolded, excess proteins to maintain homeostasis. At the same time, it can be utilized by tumors to degrade over-proliferate and unwanted proteins to support their growth. Proteasomes can affect the development of tumors from several aspects including tumor signaling pathways such as NF-κB and p53, cell cycle, immune regulation, and drug resistance. Proteasome-encoding genes have been found to be overexpressed in a variety of tumors, providing a potential novel target for cancer therapy. In addition, proteasome inhibitors such as bortezomib, carfilzomib, and ixazomib have been put into clinical application as the first-line treatment of multiple myeloma. More and more studies have shown that it also has different therapeutic effects in other tumors such as hepatocellular carcinoma, non-small cell lung cancer, glioblastoma, and neuroblastoma. However, proteasome inhibitors are not much effective due to their tolerance and singleness in other tumors. Therefore, further studies on their mechanisms of action and drug interactions are needed to investigate their therapeutic potential.

HSP90 inhibition downregulates DNA replication and repair genes via E2F1 repression

Mantle cell lymphoma (MCL) is an especially aggressive and highly heterogeneous mature B-cell lymphoma. Heat shock protein 90 (HSP90) is considered an attractive therapeutic target in a variety of cancers, including MCL, but no HSP90 inhibitors have succeeded in the clinical trials to date. Exploring fine mechanisms of HSP90 inhibition in cancer cells may shed light on novel therapeutic strategies. Here, we found that HSP90 knockdown and continuous inhibition with ganetespib inhibited growth of MCL cells in vitro and in vivo. To our surprise, transient exposure over 12 h was almost as efficient as continuous exposure, and treatment with ganetespib for 12 h efficiently inhibited growth and induced G1 cell cycle arrest and apoptosis of MCL cells. Transcriptome analysis complemented by functional studies was performed to define critical MCL signaling pathways that are exceptionally sensitive to HSP90 inhibition and vital to cell fate. Six genes (cell division cycle 6, cell division cycle 45, minichromosome maintenance 4, minichromosome maintenance 7, RecQ-mediated genome instability 2, and DNA primase polypeptide 1) involved in DNA replication and repair were identified as consistently downregulated in three MCL cell lines after transient ganetespib treatment. E2F1, an important transcription factor essential for cell cycle progression, was identified as a ganetespib target mediating transcriptional downregulation of these six genes, and its stability was also demonstrated to be maintained by HSP90. This study identifies E2F1 as a novel client protein of HSP90 that is very sensitive and worthy of targeting and also finds that HSP90 inhibitors may be useful in combination therapies for MCL.

Pharmacology differences among proteasome inhibitors: Implications for their use in clinical practice

Preclinical and clinical investigation on proteasome as a druggable target in cancer has led to the development of proteasome inhibitors (PIs) with different pharmacodynamic and pharmacokinetic properties. For example, carfilzomib has a better safety profile and a lower risk of clinically relevant drug-drug interactions than bortezomib, whereas ixazomib can be orally administered on a weekly basis due to a very long elimination half-life and high systemic exposure. The purpose of this review article is to elucidate the quantitative and qualitative differences in potency, selectivity, pharmacokinetics, safety and drug-drug interactions of clinically validated PIs to provide useful information for their clinical use in real life setting.

The safety of available chemo-free treatments for mantle cell lymphoma

INTRODUCTION

Conventional treatment for mantle cell lymphoma (MCL) patients includes regimens combining rituximab with other cytotoxic drugs, followed or not by consolidation with autologous stem cell transplantation and rituximab maintenance. However, older, unfit, and relapsed/refractory patients are often ineligible for intense treatment. Currently, available new targeted treatment options seem to offer hope in this group of patients.

AREAS COVERED

This article reviews the safety profiles of new therapeutic chemotherapy-free options for MCL patients. Publications in English from 2010 through June 2020 were surveyed on the MEDLINE database for articles. Proceedings of the American Society of Hematology during the last 5 years were also included.

EXPERT OPINION

MCL is a clinically heterogenous disease predominantly affecting elderly patients. Its variable clinical course requires personalization and individualization of treatment to achieve optimal survival and acceptable safety profiles, especially in poor prognosis patients. Results of clinical trials performed in the past decade indicated that novel drugs used as a single agent or as part of a conventional chemotherapeutic treatment offer promise in minimalizing the relapse rate for MCL and may allow more effective and safer treatment options by reducing the risk of adverse events, especially cytopenias and infections.

Efficacy and safety of frontline rituximab, cyclophosphamide, doxorubicin and prednisone plus bortezomib (VR-CAP) or vincristine (R-CHOP) in a subset of newly diagnosed mantle cell lymphoma patients medically eligible for transplantation in the randomized, phase 3 LYM-3002 study

This post-hoc subanalysis of the LYM-3002 phase 3 study assessed the efficacy and safety of substituting vincristine in rituximab, cyclophosphamide, doxorubicin and prednisone (R-CHOP; n = 42) for bortezomib (VR-CAP; n = 38) in a subgroup of 80 mantle cell lymphoma (MCL) patients aged <60 years who did not receive stem cell transplantation (SCT) despite medical eligibility. Complete response (CR)/unconfirmed CR (CRu) rates were 67 vs. 39% (odds ratio 3.69 [95% CI(confidence interval): 1.31, 10.41]; p = .012). After 40 months median follow-up, median progression-free survival by independent radiology committee with VR-CAP vs. R-CHOP was 32.6 vs. 12.0 months (hazard ratio (HR) 0.59 [95% CI: 0.31, 1.13]; p = .108); median overall survival was not reached vs. 47.3 months (HR 0.81 [95% CI: 0.33, 1.96]; p = .634). Adverse events included neutropenia (92/76%), thrombocytopenia (70/10%) and leukopenia (65/50%). VR-CAP represents a potential alternative to R-CHOP in combined and/or alternating regimens for younger, SCT-eligible MCL patients.

Anchimerically Activated ProTides as Inhibitors of Cap-Dependent Translation and Inducers of Chemosensitization in Mantle Cell Lymphoma

The cellular delivery of nucleotides through various pronucleotide strategies has expanded the utility of nucleosides as a therapeutic class. Although highly successful, the highly popular ProTide system relies on a four-step enzymatic and chemical process to liberate the corresponding monophosphate. To broaden the scope and reduce the number of steps required for monophosphate release, we have developed a strategy that depends on initial chemical activation by a sulfur atom of a methylthioalkyl protecting group, followed by enzymatic hydrolysis of the resulting phosphoramidate monoester. We have employed this ProTide strategy for intracellular delivery of a nucleotide antagonist of eIF4E in mantle cell lymphoma (MCL) cells. Furthermore, we demonstrated that chemical inhibition of cap-dependent translation results in suppression of c-Myc expression, increased p27 expression, and enhanced chemosensitization to doxorubicin, dexamethasone, and ibrutinib. In addition, the new ProTide strategy was shown to enhance oral bioavailability of the corresponding monoester phosphoramidate.

LncRNA MALAT1 promotes development of mantle cell lymphoma by associating with EZH2

Background

Mantle cell lymphoma (MCL) is considered an aggressive subtype of non-Hodgkin’s lymphoma with variable treatment responses. There is an urgent need to identify novel markers with prognostic and therapeutic value for MCL. Long non-coding RNAs (lncRNAs) have emerged as key regulators in cancers, including MCL. Metastasis-associated lung adenocarcinoma transcript 1(MALAT1), a lncRNA located at pathognomonic translocation site of t (11; 14) of MCL. MALAT1 is known to be overexpressed in solid tumors and hematologic malignancies. However, the pathological role and clinical relevance of MALAT1 in MCL are not completely understood.

Methods

We quantified MALAT1 in MCL samples (40) and CD19+ B cells by quantitative real time polymerase chain reaction (qRT-PCR) and correlated levels with clinical outcome. We silenced MALAT1 in MCL cell lines and analyzed cells in tumorigenic assays and formation of transcription complexes.

Results

We found that the expression of MALAT1 was elevated in human MCL tumors and cell lines as compared to normal controls, and the elevated levels of MALAT1 correlated with higher MCL international prognostic index (MIPI) and reduced overall survival. MCL with knockdown of MALAT1 showed impaired cell proliferation, facilitated apoptosis and produced fewer clonogenic foci. The increased expression of p21 and p27 upon MALAT1 knockdown was regulated by enhancer of zeste homolog 2 (EZH2). Moreover, decreased phosphorylation of EZH2 at T350 attenuated the binding to MALAT1.

Conclusions

Our findings illuminate the oncogenic role of MALAT1, which may serve as a novel biomarker and as a therapeutic target in MCL.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1100-9) contains supplementary material, which is available to authorized users.

The preclinical discovery and development of bortezomib for the treatment of mantle cell lymphoma

INTRODUCTION

Mantle cell lymphoma (MCL) is an incurable, often aggressive B-cell malignancy. Bortezomib (BTZ), the 20S proteasome inhibitor was originally developed and approved for treatment of relapsed refractory multiple myeloma, and subsequently approved for treatment of MCL. BTZ's single-agent activity induces clinical responses in approximately one-third of relapsed MCL patients. BTZ-containing combination therapies have further improved the quality and duration of clinical responses compared to standard chemotherapies in previously untreated MCL patients. Areas covered: This review summarizes the discovery, mechanisms of -action and resistance, preclinical- clinical-developments, and FDA approval of BTZ for treatments of MCL. Expert opinion: Preclinical MCL models demonstrated the apoptotic effect of BTZ through multiple mechanisms, as well as synergistic anti-MCL activity between BTZ and other chemotherapeutics. Single-agent and combinational clinical trials have validated the therapeutic potential of targeting the ubiquitin proteasome system (UPS) in MCL. However, inherent and acquired drug resistance remains a significant clinical problem and multiple potential mechanisms have been identified. Next-generation proteasome inhibitors with different pharmacodynamic properties from BTZ may partially address the issue of inherent resistance, with increased response rates noted in some diseases. In addition, upstream UPS components, e.g., E3 ligases or deubiquitinating enzymes, may also be targetable in MCL.

Bortezomib for the treatment of mantle cell lymphoma: an update

Bortezomib is a first in class proteasome inhibitor, initially approved by the US Food and Drug Administration for the treatment of plasma cell myeloma. Bortezomib has been approved for the treatment of relapsed and refractory mantle cell lymphoma (MCL) and, more recently, in the upfront setting as well. Treatment algorithms for MCL have rapidly evolved over the past two decades, and the optimal regimen remains to be defined. The choice of treatment regimen is based on disease risk stratification models, the expected toxicity of antineoplastic agents, the perceived patient ability to tolerate the planned treatments and the availability of novel agents. As new drugs with novel mechanisms of action and variable toxicity profiles come into use, treatment decisions for a given patient have become increasingly complex. This article provides an overview of the evolving use of bortezomib in the rapidly changing management landscape of MCL.

p27 Is a Candidate Prognostic Biomarker and Metastatic Promoter in Osteosarcoma

Metastatic progression is the major cause of death in osteosarcoma, the most common bone malignancy in children and young adults. However, prognostic biomarkers and efficacious targeted treatments for metastatic disease remain lacking. Using an immunoproteomic approach, we discovered that autoantibodies against the cell-cycle kinase inhibitor p27 (KIP1, CDKN1B) were elevated in plasma of high-risk osteosarcoma patients. Using a large cohort of serum samples from osteosarcoma patients (n = 233), we validated that a higher level of the p27 autoantibody significantly correlated with poor overall and event-free survival (P < 0.05). Immunohistochemical analysis also showed that p27 was mislocalized to the cytoplasm in the majority of osteosarcoma cases and in highly metastatic osteosarcoma cell lines. We demonstrated that ectopic expression of cytoplasmic p27 promoted migration and invasion of osteosarcoma cells, whereas shRNA-mediated gene silencing suppressed these effects. In addition, mutations at the p27 phosphorylation sites S10 or T198, but not T157, abolished the migratory and invasive phenotypes. Furthermore, the development of pulmonary metastases increased in mice injected with cells expressing cytoplasmic p27 compared with an empty vector control. Collectively, our findings support further investigation of p27 as a potential prognostic biomarker and therapeutic target in osteosarcoma cases exhibiting aberrant p27 subcellular localization. Cancer Res; 76(13); 4002-11. ©2016 AACR.

Bortezomib for the treatment of non-Hodgkin's lymphoma

INTRODUCTION

Bortezomib , the first proteasome inhibitor (PI) to be evaluated in humans, is approved in the USA and Europe for the treatment of patients with multiple myeloma, and in the USA for patients with relapsed mantle cell lymphoma (MCL).

AREAS COVERED

This review examines the role of bortezomib in the therapy of non-Hodgkin's lymphoma (NHL). Bortezomib may be particularly effective against the NF-κB-dependent activated B-cell subtype of diffuse large B-cell lymphoma. The combination of bortezomib with rituximab and dexamethasone represents a standard approach for the treatment of Waldenström's macroglobulinemia, and that with bendamustine and rituximab has demonstrated excellent efficacy in follicular lymphoma. Combinations with other novel agents, such as inhibitors of cyclin-dependent kinases or histone deacetylases, also hold substantial promise in NHL. Unmet needs in NHL, competitor compounds, chemistry, pharmacokinetics, pharmacodynamics and safety and tolerability of bortezomib are also discussed.

EXPERT OPINION

The success of bortezomib in MCL has validated the proteasome as a therapeutic target in NHL. Rational combinations, for example, with Bruton's tyrosine kinase inhibitors or BH3-mimetics, may hold the key to optimizing the therapeutic potential of PIs in NHL. Future trials are likely to involve newer agents with improved pharmacodynamic (e.g., carfilzomib, marizomib) or pharmacokinetic (e.g., ixazomib, oprozomib) properties.

Development and characterization of a Mantle Cell Lymphoma Cell Bank in the American Type Culture Collection

Mantle cell lymphoma (MCL) is a rare B-cell malignancy that carries a relatively poor prognosis compared to other forms of non-Hodgkin lymphoma. Standardized preclinical tools are desperately required to hasten the discovery and translation of promising new treatments for MCL. Via an initiative organized through the Mantle Cell Lymphoma Consortium and the Lymphoma Research Foundation, we gathered MCL cell lines from laboratories around the world to create a characterized MCL Cell Bank at the American Type Culture Collection (ATCC). Initiated in 2006, this collection now contains eight cell lines, all of which have been rigorously characterized and are now stored and available for distribution to the general scientific community. We believe the awareness and use of these standardized cell lines will decrease variability between investigators, harmonize international research efforts, improve our understanding of the pathogenesis of the disease and hasten the development of novel treatment strategies.

Antitumoral activity of lenalidomide in in vitro and in vivo models of mantle cell lymphoma involves the destabilization of cyclin D1/p27KIP1 complexes

PURPOSE

Clinical responses to the immmunomodulatory drug lenalidomide have been observed in patients with relapsed/refractory mantle cell lymphoma (MCL), although its mechanism of action remains partially unknown. We investigated whether the expression and subcellular localization of cyclin D1, a major cell-cycle regulator overexpressed in MCL, and the cyclin-dependent kinase inhibitor p27(KIP1), could identify MCL cases sensitive to lenalidomide, and whether the compound could modulate cyclin D1/p27(KIP1) complexes in MCL cells.

EXPERIMENTAL DESIGN

MCL primary samples and cell lines were analyzed for subcellular levels of cyclin D1/p27(KIP1) complexes by Western blot, immunohistochemistry, immunoprecipitation, and flow cytometry. Activity of lenalidomide in vitro and its effect on cyclin D1/p27(KIP1) complexes were evaluated by real-time PCR, immunoprecipitation, immunofluorescence, and Western blot. In vivo validation was carried out in a mouse xenograft model of human MCL.

RESULTS

We found cyclin D1 and p27(KIP1) to be coordinately expressed in all the MCL samples tested. Immunoprecipitation analyses and siRNA assays suggested a direct role of cyclin D1 in the regulation of p27(KIP1) levels. The nuclear accumulation of both proteins correlated with MCL cell tumorigenicity in vivo, and sensitivity to lenalidomide activity in vitro and in vivo. Lenalidomide mechanism of action relied on cyclin D1 downregulation and disruption of cyclin D1/p27(KIP1) complexes, followed by cytosolic accumulation of p27(KIP1), cell proliferation arrest, apoptosis, and angiogenesis inhibition.

CONCLUSIONS

These results highlight a mechanism of action of lenalidomide in MCL cases with increased tumorigenicity in vivo, which is mediated by the dissociation of cyclin D1/p27(KIP1) complexes, and subsequent proliferation blockade and apoptosis induction.

Identification of small molecule inhibitors of p27(Kip1) ubiquitination by high-throughput screening

Dysregulation of p27(Kip1) due to proteolysis that involves the ubiquitin ligase (SCF) complex with S-phase kinase-associated protein 2 (Skp2) as the substrate-recognition component (SCF(Skp2)) frequently results in tumorigenesis. In this report, we developed a high-throughput screening system to identify small-molecule inhibitors of p27(Kip1) degradation. This system was established by tagging Skp2 with fluorescent monomeric Azami Green (mAG) and CDK subunit 1 (Cks1) (mAGSkp2-Cks1) to bind to p27(Kip1) phosphopeptides. We identified two compounds that inhibited the interaction between mAGSkp2-Cks1 and p27(Kip1): linichlorin A and gentian violet. Further studies have shown that the compounds inhibit the ubiquitination of p27(Kip1) in vitro as well as p27(Kip1) degradation in HeLa cells. Notably, both compounds exhibited preferential antiproliferative activity against HeLa and tsFT210 cells compared with NIH3T3 cells and delayed the G1 phase progression in tsFT210 cells. Our approach indicates a potential strategy for restoring p27(Kip1) levels in human cancers.

Clinical practice guidelines for diagnosis, treatment, and follow-up of patients with mantle cell lymphoma. Recommendations from the GEL/TAMO Spanish Cooperative Group

Mantle cell lymphoma (MCL) is considered a distinct type of B-cell lymphoma genetically characterized by the t(11;14) translocation and cyclin D1 overexpression. There is also a small subset of tumors negative for cyclin D1 expression that are morphologically and immunophenotypically indistinguishable from conventional MCL. Although in the last decades, the median overall survival of patients with MCL has improved significantly, it is still considered as one of the poorest prognoses diseases among B-cell lymphomas. Election of treatment for patients with MCL is complex due to the scarcity of solid evidence. Current available data shows that conventional chemotherapy does not yield satisfactory results as in other types of B-cell lymphomas. However, the role of other approaches such as autologous or allogenic stem cell transplantation, immunotherapy, the administration of consolidation or maintenance schedules, or the use of targeted therapies still lack clear indications. In view of this situation, the Spanish Group of Lymphomas/Autologous Bone Marrow Transplantation has conducted a series of reviews on different aspects of MCL, namely its diagnosis, prognosis, first-line and salvage treatment (both in young and elderly patients), new targeted therapies, and detection of minimal residual disease. On the basis of the available evidence, a series of recommendations have been issued with the intention of providing guidance to clinicians on the diagnosis, treatment, and monitoring of patients with MCL.

The role of the ubiquitin proteasome system in lymphoma

The ubiquitin-proteasome system (UPS) maintains the integrity of cellular processes by controlling protein degradation pathways. The role of the UPS in proliferation, cell cycle, differentiation, DNA repair, protein folding, and apoptosis is well documented, and a wide range of protein activities in these signaling pathways can be manipulated by UPS inhibitors, which include many anti-cancer agents. Naturally occurring and synthetic drugs designed to target the UPS are currently used for hematological cancers, including lymphoma. These drugs largely interfere with the E1 and E2 regions of the 26S proteasome, blocking proteasomal activity and promoting apoptosis by enhancing activities of the extrinsic (death receptors, Trail, Fas) and intrinsic (caspases, Bax, Bcl2, p53, nuclear factor-kappa B, p27) cell death programs. This review focuses on recent clinical developments concerning UPS inhibitors, signaling pathways that are affected by down-regulation of UPS activities, and apoptotic mechanisms promoted by drugs in this class that are used to treat lymphoma.

Gene methylation and silencing of SOCS3 in mantle cell lymphoma

The significance of loss of SOCS3, a negative regulator of signalling pathways including those of STAT3 and NF-κB, was examined in mantle cell lymphoma (MCL). The protein expression and gene methylation status of SOCS3 were detected using immunohistochemistry/Western blots and methylation-specific polymerase chain reaction, respectively. To evaluate its functional importance, SOCS3 was restored in two SOCS3-negative MCL cell lines using a lentiviral vector. Loss of SOCS3 protein expression was found in 3/4 MCL cell lines and 18/33 (54.5%) tumours. SOCS3 was found consistently methylated in cell lines (3/4) and tumours (7/7) negative for SOCS3, and was unmethylated in all SOCS3-positive cell line (1/1) and tumours (5/5) examined. Treatment of all three SOCS3-negative cell lines with 2'-deoxy-5-azacytidine restored SOCS3 expression. SOCS3 is biologically important in MCL, as lentiviral transfer of SOCS3 in SOCS3-negative cell lines increased their apoptotic activity, downregulated nuclear factor (NF)-κB-p65, cyclin D1 (CCND1), BCL2 and BCL-XL (BCL2L1), and substantially dampened interleukin 10-induced STAT3 activation. In 19 patients aged ≤ 69 years at time of diagnosis, we found that those that carried SOCS3-negative tumours showed a trend toward a worse outcome (P = 0.1, log-rank).

Retinoic acid/alpha-interferon combination inhibits growth and promotes apoptosis in mantle cell lymphoma through Akt-dependent modulation of critical targets

Mantle cell lymphoma (MCL) is characterized by a profound deregulation of the mechanisms controlling cell-cycle progression and survival. We herein show that the combination of 9-cis-retinoic acid (RA) and IFN-α induces marked antiproliferative and proapoptotic effects in MCL cells through the modulation of critical targets. Particularly, IFN-α enhances RA-mediated G(0)-G(1) cell accumulation by downregulating cyclin D1 and increasing p27(Kip1) and p21(WAF1/Cip1) protein levels. Furthermore, RA/IFN-α combination also induces apoptosis by triggering both caspases-8 and -9 resulting in Bax and Bak activation. In particular, RA/IFN-α treatment downregulates the antiapoptotic Bcl-xL and Bfl-1 proteins and upregulates the proapoptotic BH3-only Noxa protein. Sequestration of Mcl-1 and Bfl-1 by upregulated Noxa results in the activation of Bid, and the consequent induction of apoptosis is inhibited by Noxa silencing. Noxa upregulation is associated with nuclear translocation of the FOXO3a transcription factor as consequence of RA/IFN-α-induced Akt inhibition. Pharmacologic suppression of Akt, but not of TORC1, increases Noxa protein levels and downregulates Bfl-1 protein supporting the conclusion that the inhibition of the Akt pathway, the resulting FOXO3a activation and Noxa upregulation are critical molecular mechanisms underlying RA/IFN-α-dependent MCL cell apoptosis. These results support the potential therapeutic value of RA/IFN-α combination in MCL management.

Overexpression of phosphorylated p27 Kip1 at threonine 187 may predict outcome in aggressive B-cell lymphomas

Phosphorylation of p27(Kip1) at threonine 187 (pThr187-p27(Kip1)) occurs frequently in the development of human tumors, directing protein polyubiquitination and subsequent proteasomal degradation. We investigated the immunoexpression of p27(Kip1) and pThr187-p27(Kip1) in 126 B-cell lymphomas and their relation to proliferative activity and clinical parameters. Increased levels of p27(Kip1) and pThr187-p27(Kip1) were significantly correlated with indolent and aggressive lymphomas, respectively (p < 0.001). pThr187-p27(Kip1) expression showed a strong positive correlation with proliferation index in aggressive (p = 0.01) and indolent (p < 0.001) subgroups. Survival analysis revealed that pThr187-p27(Kip1) was an unfavorable prognostic factor for disease-free (p = 0.019) and overall survival (p = 0.003) in aggressive lymphomas. Cox regression analysis demonstrated that the prognostic value of pThr187-p27(Kip1) was independent of the international prognostic index (IPI) score, tumor stage, patient age, and serum lactate dehydrogenase (LDH) level. Overall, our results suggest that high levels of pThr187-p27(Kip1) may predict a worse clinical outcome in patients with aggressive lymphomas.

RNAi-mediated downregulation of NOB1 suppresses the growth and colony-formation ability of human ovarian cancer cells

Nin one binding protein (NOB1p), encoded by the NOB1 gene, is a crucial molecule in the maturation of the 20S proteasome and protein degradation. The present study evaluates whether NOB1 is an appropriate molecular target for cancer gene therapy. In two ovarian cancer cell lines, SKOV3 and HEY, NOB1 expression was knocked down by a lentiviral short hairpin RNA (shRNA) delivery system. The RNA interference (RNAi)-mediated the downregulation of NOB1 expression markedly reduced the proliferative and colony-formation ability of ovarian cancer cells. Additionally, NOB1 shRNA-expressing lentivirus-treated ovarian cancer cells tended to arrest in the G0/G1 phase. These results suggested that NOB1 may act as an oncogenic factor in ovarian cancer and could be a potential molecular target for ovarian cancer gene therapy.

Cyclin-dependent kinase inhibitor p27 as a prognostic biomarker and potential cancer therapeutic target

The prognosis and clinical management of patients with cancer is commonly determined by traditional clinical and pathological factors. Nevertheless, patients may present with significantly different clinical outcomes despite similar clinicopathological features. This has prompted intense research to find biological markers that may closely reflect tumor biology and thereby clinical outcome. This article presents the current knowledge on the prognostic significance of p27 expression in cancer and its potential role as a target for future therapy.

Ig gene diversification and selection in follicular lymphoma, diffuse large B cell lymphoma and primary central nervous system lymphoma revealed by lineage tree and mutation analyses

Follicular lymphoma (FL), diffuse large B cell lymphoma (DLBCL) and primary central nervous system lymphoma are B cell malignancies. FL and DLBCL have a germinal center origin. We have applied mutational analyses and a novel algorithm for quantifying shape properties of mutational lineage trees to investigate the nature of the diversification, somatic hypermutation and selection processes that affect B cell clones in these malignancies and reveal whether they differ from normal responses. Lineage tree analysis demonstrated higher diversification and mutations per cell in the lymphoma clones. This was caused solely by the longer diversification times of the malignant clones, as their recent diversification processes were similar to those of normal responses, implying similar mutation frequencies. Since previous analyses of antigen-driven selection were shown to yield false positives, we performed a corrected analysis of replacement and silent mutation patterns, which revealed selection against replacement mutations in the framework regions, responsible for the structural integrity of the B cell receptor, but not for positive selection for replacements in the complementary determining regions. Most replacements, however, were neutral or conservative, suggesting that if at all selection operates in these malignancies it is for structural B cell receptor integrity but not for antigen binding.

Differential expression of CKS-1B in typical and blastoid variants of mantle cell lymphoma

Mantle cell lymphoma is a distinct type of B-cell lymphoma characterized by the t(11;14)(q13;q32). Mantle cell lymphomas exhibit a spectrum of morphologic findings, of which a subset of tumors is clinically aggressive with a high proliferation rate. These neoplasms are known as aggressive variants of which there are blastoid and pleomorphic subsets. CKS-1B (CDC28 protein kinase regulatory subunit 1B) is essential for the ubiquitination and degradation of p27 and cell cycle progression. We analyzed CKS-1B expression in mantle cell lymphoma cell lines and tumors by Western blot and immunohistochemical analysis. In 4 mantle cell lymphoma cell lines, CKS-1B was expressed at variable levels and correlated inversely with p27 expression. In mantle cell lymphoma tumors, CKS-1B was positive in 10 (28.6%) of 35 typical versus 14 (87.5%) of 16 blastoid/pleomorphic cases (Fisher exact test, P = .0002). Analyzed as a continuous variable, the percentage of CKS-1B-positive cells significantly correlated with blastoid/pleomorphic morphology (Mann-Whitney U test, P = .001). Twelve (23.5%) of 51 mantle cell lymphoma tumors expressed p27. Proliferation rate (Ki-67) was higher in blastoid/pleomorphic variants than in typical mantle cell lymphoma tumors and was inversely associated with p27 levels in typical mantle cell lymphoma. However, CKS-1B expression did not correlate with p27 expression, proliferation rate, or prognosis in the entire study group. Fluorescence in situ hybridization analysis of 10 CKS-1B-positive mantle cell lymphoma tumors showed no evidence of CKS-1B gene amplification. We conclude that CKS-1B is commonly expressed in mantle cell lymphoma, particularly in aggressive histologic variants, and may be involved in pathogenesis.

Rapid fatal pulmonary complications in a Chinese patient after bortezomib treatment for ALK-negative anaplastic large-cell lymphoma

Bortezomib, a reversible proteasome inhibitor, is used for the treatment of hematologic malignancies. Common adverse events with bortezomib include gastrointestinal symptoms, thrombocytopenia, and neuropathy, whereas severe pulmonary complications have been rarely described. Herein, we present a case of rapid fatal pulmonary complications in a patient with ALK-negative anaplastic large-cell lymphoma after receiving a treatment with bortezomib.

[Mantle cell lymphoma: an overview from diagnosis to future therapies]

Mantle cell lymphoma (MCL) is a rare non-Hodgkin lymphoma (NHL) entity. The translocation between chromosomes 11 and 14 is the cytogenetics hallmark of MCL. This translocation leads to the dysregulation of the CCDN1 gene, and overexpression of cyclin D1 which promotes cell cycling. Despite a classical phenotype (CD19+, CD20+, CD5+, CCND1+, CD10-, CD23-, Bcl-2+, Ig at the membrane, mainly IgM), MCL is not a homogeneous disease and several cytological, phenotypic, cytogenetic and clinical variants have been described. MCL represents 5 % of NHLs with its incidence constantly increasing over the last years. Median age at diagnosis is 68 years. Stage III-IV disease is observed in more than 80 % of patients at presentation, with intestinal and bone marrow being the most frequently involved organs, while the spleen is enlarged in half of cases. Intensive strategies including high-dose chemotherapy, followed by autologous stem cell transplantation have significantly improved the outcome of MCL patients. Median overall survival rate increased from 3 to 5 years during the last decade. At present, induction chemotherapy followed by high-dose chemotherapy and autologous stem cell transplantation is the standard regimen in younger patients. However, most of MCL patients will experience relapse. Thus, close monitoring of minimal residual disease (currently under evaluation) may represent a valuable tool for assessment of disease response during follow-up. Future innovative therapies that are being presently investigated in prospective trials include transduction pathways inhibitors, proteasome inhibitors, pro-apoptotic molecules, immunotherapy and/or radiolabeled immunotherapy, and will likely open a new era for targeted therapies in MCL.

All trans retinoic acid nanodisks enhance retinoic acid receptor mediated apoptosis and cell cycle arrest in mantle cell lymphoma

Mantle cell lymphoma (MCL) is characterized by translocation t(11;14)(q13;q32), aggressive clinical behaviour, and poor patient outcomes following conventional chemotherapy. New treatment approaches are needed that target novel biological pathways. All trans retinoic acid (ATRA) is a key retinoid that acts through nuclear receptors that function as ligand-inducible transcription factors. The present study evaluated cell killing effects of ATRA-enriched nanoscale delivery particles, termed nanodisks (ND), on MCL cell lines. Results show that ATRA-ND induced cell death more effectively than naked ATRA (dimethyl sulphoxide) or empty ND. ATRA-ND induced reactive oxygen species (ROS) generation to a greater extent than naked ATRA. The antioxidant, N-acetylcysteine, inhibited ATRA-ND induced apoptosis. Compared to naked ATRA, ATRA-ND enhanced G1 growth arrest, up-regulated p21and p27, and down regulated cyclin D1. At ATRA concentrations that induced apoptosis, expression levels of retinoic acid receptor-alpha (RARalpha) and retinoid X receptor-gamma (RXRgamma) were increased. Compared to naked ATRA, ATRA-ND significantly stimulated transcriptional activity of RARA in a model carcinoma cell line. Furthermore, the RAR antagonist, Ro 41-5253, inhibited ATRA-ND induced ROS generation and prevented ATRA-ND induced cell growth arrest and apoptosis. In summary, incorporation of ATRA into ND enhanced the biological activity of this retinoid in cell culture models of MCL.

Combination bortezomib and rituximab treatment affects multiple survival and death pathways to promote apoptosis in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a distinct histologic subtype of B cell non-Hodgkins lymphoma (NHL) associated with an aggressive clinical course. Inhibition of the ubiquitin-proteasome pathway modulates survival and proliferation signals in MCL and has shown clinical benefit in this disease. This has provided rationale for exploring combination regimens with B-cell selective immunotherapies such as rituximab. In this study, we examined the effects of combined treatment with bortezomib and rituximab on patient-derived MCL cell lines (Jeko, Mino, SP53) and tumor samples from patients with MCL where we validate reversible proteasome inhibition concurrent with cell cycle arrest and additive induction of apoptosis. When MCL cells were exposed to single agent bortezomib or combination bortezomib/rituximab, caspase dependent and independent apoptosis was observed. Single agent bortezomib or rituximab treatment of Mino and Jeko cell lines and patient samples resulted in decreased levels of nuclear NFkappaB complex(es) capable of binding p65 consensus oligonucleotides, and this decrease was enhanced by the combination. Constitutive activation of the Akt pathway was also diminished with bortezomib alone or in combination with rituximab. On the basis of in vitro data demonstrating additive apoptosis and enhanced NFkappaB and phosphorylated Akt depletion in MCL with combination bortezomib plus rituximab, a phase II trial of bortezomib-rituximab in patients with relapsed/refractory MCL is underway.

Mantle cell lymphoma shows three morphological evolutions of classical, intermediate, and aggressive forms, which occur in parallel with increased labeling index of cyclin D1 and Ki-67

Although the 2008 World Health Organization classification defines two subtypes of mantle cell lymphoma (MCL), classical and aggressive, we often encounter MCL with both features in the same site. We named this feature "MCL with focal aggressive form (intermediate MCL)". In the present study, we reclassified 237 patients with cyclin D1 (CCND1)-positive MCL on the basis of the concept of intermediate MCL, and analyzed the correlation of this reclassification with immunohistochemical detection of CCND1, Ki-67, p53, p27(Kip1), and p21(WAF/Cip1). The median overall survival was 77, 31, and 18 months for classical, intermediate, and aggressive MCL, respectively, showing a statistically significant difference (P < 0.0001). The expression levels of CCND1, Ki-67, p53, and p21(WAF/Cip1) in aggressive MCL (mean 80.1 +/- 27.8%, 73.7 +/- 28.9%, 31.0 +/- 69.0%, and 10.4 +/- 24.8%, respectively) were higher than those in classical MCL (mean 58.1 +/- 36.7%, 25.2 +/- 25.5%, 6.5 +/- 24.3%, and 2.5 +/- 13.0%, respectively) and intermediate MCL (mean 75.7 +/- 31.4%, 30.8 +/- 33.3%, 21.0 +/- 57.4%, and 4.8 +/- 16.5%, respectively). Significantly different levels of Ki-67 and p21(WAF/Cip1) were only recognized between intermediate and aggressive (P < 0.05 and P < 0.0001, respectively), whereas those of CCND1 and p53 were only between classical and intermediate (P < 0.0001 and P < 0.05, respectively). There were no significant differences in p27(Kip1) among the three groups. The subsequent discriminant analysis with independent prognostic factors clearly demonstrated that the morphological evolution of MCL occurs in parallel with increased labeling index of CCND1 and Ki-67. The diagnosis of intermediate MCL thus proved to be of major significance and should enable the design of more tailored therapies.

Expression of eukaryotic initiation factor 4E predicts clinical outcome in patients with mantle cell lymphoma treated with hyper-CVAD and rituximab, alternating with rituximab, high-dose methotrexate, and cytarabine

BACKGROUND

Oncogenic AKT/mammalian target of rapamycin (mTOR) signaling has recently been shown to contribute to tumor survival and proliferation in mantle cell lymphoma (MCL) through its downstream effector eukaryotic initiation factor 4E (eIF4E), which may control cyclin D1 protein levels. However, the clinical significance of eIF4E expression in MCL is unknown.

METHODS

The authors investigated the prognostic significance of eIF4E expression in 70 MCL patients uniformly treated with hyper-CVAD and rituximab, alternating with the rituximab, high-dose methotrexate, and cytarabine regimen (R-hyper-CVAD). eIF4E expression was assessed using tissue biopsy specimens obtained before treatment, immunohistochemical methods, and a highly specific monoclonal antibody. Failure-free (FFS) and overall (OS) survival were used as endpoints in univariate and multivariate survival analysis.

RESULTS

High eIF4E expression was found in 28 (40%) MCL tumors. After a median follow-up of 51 months for survivors, the 5-year FFS was 20.6% for patients with high eIF4E expression, compared with 63.5% for patients with low or no eIF4E expression (P=.01, log-rank). Similarly, the 5-year OS was 40.1% for patients with high eIF4E expression, compared with 73.8% for patients with low or no eIF4E expression (P=.018, log-rank). In multivariate analysis, eIF4E expression was associated with poorer FFS and OS, along with age>60 years and high beta2-microglobulin in the final prognostic model.

CONCLUSIONS

In summary, eIF4E, which seems to recapitulate most of the biologic effects of mTOR signaling in MCL, is an independent predictor of clinical outcome in MCL patients uniformly treated with the R-hyper-CVAD regimen.

Calcium-dependent plasma membrane repair requires m- or mu-calpain, but not calpain-3, the proteasome, or caspases

Mechanically damaged plasma membrane undergoes rapid calcium-dependent resealing that appears to depend, at least in part, on calpain-mediated cortical cytoskeletal remodeling. Cells null for Capns1, the non-catalytic small subunit present in both m- and mu-calpains, do not undergo calcium-mediated resealing. However, it is not known which of these calpains is needed for repair, or whether other major cytosolic proteinases may participate. Utilizing isozyme-selective siRNAs to decrease expression of Capn1 or Capn2, catalytic subunits of mu- and m-calpains, respectively, in a mouse embryonic fibroblast cell line, we now show that substantial loss of both activities is required to compromise calcium-mediated survival after cell scrape-damage. Using skeletal myotubes derived from Capn3-null mice, we were unable to demonstrate loss of sarcolemma resealing after needle scratch or laser damage. Isolated muscle fibers from Capn3 knockout mice also efficiently repaired laser damage. Employing either a cell line expressing a temperature sensitive E1 ubiquitin ligase, or lactacystin, a specific proteasome inhibitor, it was not possible to demonstrate an effect of the proteasome on calcium-mediated survival after injury. Moreover, several cell-permeant caspase inhibitors were incapable of significantly decreasing survival or inhibiting membrane repair. Taken together with previous studies, the results show that m- or mu-calpain can facilitate repair of damaged plasma membrane. While there was no evidence for the involvement of calpain-3, the proteasome or caspases in early events of plasma membrane repair, our studies do not rule out their participation in downstream events that may link plasma membrane repair to adaptive remodeling after injury.

Targeting the proteasome in mantle cell lymphoma: A promising therapeutic approach

Mantle cell lymphoma (MCL) is a distinctive non-Hodgkin's lymphoma sub-type, characterized by over-expression of cyclin D1 as a consequence of chromosomal translocation t(11;14)(q13;q32). MCL remains an incurable disease, combining the unfavorable clinical features of aggressive and indolent lymphomas. The blastic variant of MCL, which is often associated with additional cytogenetic alterations, has an even worse prognosis and new treatment options are clearly needed. The 26S proteasome is a large multi-catalytic multi-protein complex, present in all eukaryotic cells. It is responsible for the degradation of a variety of short-lived proteins and exhibits a key position in cellular processes including apoptosis and cell cycle progression. Targeting the ubiquitin - proteasome pathway has only recently been identified as a promising new therapeutic option for cancer patients. Interestingly, an increased activity of the proteasome pathway has been described in MCL cells and the inhibition of the proteasome seems to be a promising therapeutic approach for this incurable disease.

Molecular outcome prediction in mantle cell lymphoma

Mantle cell lymphoma (MCL), a subtype of B-cell non-Hodgkin lymphoma, is usually incurable with current therapeutic approaches and the clinical course displays considerable variability. Objective assessment of the efficacy of new and more tailored treatment strategies requires deeper molecular insights into the disease and more individual risk assessment. The molecular feature of tumor cell proliferation as measured by Ki-67 immunohistochemistry or, more precisely, by microarray-based gene-expression profiling, has been shown to be of strong predictive value in MCL. The recently proposed quantitative reverse transcription-PCR based five-gene model survival predictor is applicable to fresh-frozen and routinely obtained formalin-fixed and paraffin-embedded tumor tissues, and provides the potential to investigate its prognostic value in prospective clinical trials of MCL patients.

Diffuse large B-cell lymphoma with TEL/ETV6 translocation

Cytogenetic abnormalities of chromosome 12p involving the TEL/ETV6 gene are observed in a variety of hematopoietic neoplasms including acute leukemias, myelodysplastic syndromes, and myeloproliferative disorders. Karyotypic aberrations, including rearrangements, deletions, and amplifications of chromosome 12p, have been documented in B-cell non-Hodgkin lymphoma; however, rearrangements targeting TEL have rarely been reported. Here we describe a diffuse large B-cell lymphoma that had a complex karyotype including t(9;12)(q22;p13), which was confirmed by fluorescence in situ hybridization to represent rearrangement of TEL. Additional cytogenetic abnormalities included t(3;14)(q27;q32) involving the variant, alternative breakpoint region of the BCL6 gene and del(6)(q13q23), resulting in the loss of 1 allele of BLIMP1. This case reiterates the importance of correlating morphologic and phenotypic findings with the results of cytogenetic analysis to avoid errors in diagnosing hematologic neoplasms and highlights the rare association of B-cell non-Hodgkin lymphoma with aberrations of TEL.

Molecular biology and genetics of lymphomas

This article summarizes molecular and genetic features of B-cell non-Hodgkin lymphoma and focuses on diffuse large B-cell lymphoma, Burkitt lymphoma, follicular lymphoma, and mantle cell lymphoma. In each of these entities, hallmark genetic aberrations, cytogenetic characteristics, and alterations of single genes that might be involved in the pathogenesis and molecular evolution of the tumor are described. Recent results from gene-expression profiling studies are incorporated that are relevant for the classification of lymphoma entities, the prediction of their clinical behavior, and the identification of deregulated signal-transduction pathways that might represent potential targets in future therapeutic approaches.

Ki67 and PIM1 expression predict outcome in mantle cell lymphoma treated with high dose therapy, stem cell transplantation and rituximab: a Cancer and Leukemia Group B 59909 correlative science study

The proliferation index in mantle cell lymphoma (MCL) has not been validated in the context of aggressive therapy regimens in the rituximab era. We assessed Ki67 and PIM1 (a cell cycle-related gene upregulated in blastoid MCL) expression by immunohistochemistry in a phase II study Cancer and Leukemia Group B 59909 of aggressive chemotherapy and rituximab followed by autologous stem cell transplantation plus rituximab in untreated MCL patients <70 years of age. As a continuous variable or using a cutoff of 35%, higher image analysis (IA Ki67, n = 52) was associated with shorter progression free survival (PFS) (P < or = 0.030) and event free survival (EFS) (P < or = 0.017). PIM1 expression (n = 50) was associated with PFS (P = 0.033) and EFS (P = 0.043). Bivariate Cox models showed IA Ki67 and PIM1 were independent of clinical factors. High Ki67 (>35%) is an important independent prognostic marker in aggressively treated MCL in the rituximab era. PIM1 expression predicts poor outcome and, given its potential role as a therapeutic target, deserves further study.

Mantle cell lymphoma: advances in biology and therapy

PURPOSE OF REVIEW

Mantle cell lymphoma is characterized by dysregulation of cyclin D1, but this is not sufficient for lymphoma development. It is a difficult disease to treat, being incurable with standard chemotherapy and having a median survival of approximately 5 years. The purpose of this review is to update recent advances in mantle cell lymphoma biology with prognostic and potentially therapeutic implications, and mantle cell lymphoma treatment approaches and new agents.

RECENT FINDINGS

Genetic alterations that cooperate with cyclin D1 have been described that alter proliferation, in particular p27Kip and p16INK4, or apoptosis. Biological factors such as high-proliferation signature defined by gene expression profiles, loss of p27 and presence of mutant p53 confer poor prognosis. Proliferative rate also predicts patient outcome. Clinical criteria such as the international prognostic index, follicular lymphoma international prognostic index or a formula using age, performance status, white blood cell count and lactate dehydrogenase, separate prognostic groups. Not all patients require therapy at diagnosis. Although the best reported results have been with rituximab-hyperfractionated cyclophosphamide-vincristine-doxorubicin-dexamethasone-methotrexate/cytarabine, a cooperative group study of this regimen appears not quite as successful. Consolidation of remission after rituximab-cyclophosphamide-doxorubicin-vincristine-prednisone with high-dose therapy/stem-cell support prolongs remission and consolidation with radioimmunotherapy shows promise. Intensifying induction by alternating intensified rituximab-cyclophosphamide-doxorubicin-vincristine-prednisone with rituximab and high-dose cytarabine, followed by high-dose therapy appears quite promising. Novel agents active in relapsed disease include bortezomib, mammalian target of rapamycin inhibitors, immunomodulatory agents, antibodies and cyclin pathway-directed agents such as flavopiridol and cyclin-dependent kinase inhibitors.

SUMMARY

New insights into mantle cell lymphoma biology may lead to targeted therapy. Meanwhile, combinations of existing therapeutic approaches seem to have improved outcomes.

Epidermal growth factor receptor vIII expression in U87 glioblastoma cells alters their proteasome composition, function, and response to irradiation

Little is known about the factors that influence the proteasome structures in cells and their activity, although this could be highly relevant to cancer therapy. We have previously shown that, within minutes, irradiation inhibits substrate degradation by the 26S proteasome in most cell types. Here, we report an exception in U87 glioblastoma cells transduced to express the epidermal growth factor receptor vIII (EGFRvIII) mutant (U87EGFRvIII), which does not respond to irradiation with 26S proteasome inhibition. This was assessed using either a fluorogenic substrate or a reporter gene, the ornithine decarboxylase degron fused to ZsGreen (cODCZsGreen), which targets the protein to the 26S proteasome. To elucidate whether this was due to alterations in proteasome composition, we used quantitative reverse transcription-PCR to quantify the constitutive (X, Y, Z) and inducible 20S subunits (Lmp7, Lmp2, Mecl1), and 11S (PA28alpha and beta) and 19S components (PSMC1 and PSMD4). U87 and U87EGFRvIII significantly differed in expression of proteasome subunits, and in particular immunosubunits. Interestingly, 2 Gy irradiation of U87 increased subunit expression levels by 16% to 324% at 6 hours, with a coincident 30% decrease in levels of the proteasome substrate c-myc, whereas they changed little in U87EGFRvIII. Responses similar to 2 Gy were seen in U87 treated with a proteasome inhibitor, NPI0052, suggesting that proteasome inhibition induced replacement of subunits independent of the means of inhibition. Our data clearly indicate that the composition and function of the 26S proteasome can be changed by expression of the EGFRvIII. How this relates to the increased radioresistance associated with this cell line remains to be established.

Advances in the understanding of mantle cell lymphoma

Mantle cell lymphoma (MCL) is a well-defined lymphoid neoplasm characterized by a proliferation of mature B lymphocytes expressing CD5 that may show a spectrum of morphological and phenotypic features broader than initially described. Although some patients may follow an indolent clinical evolution, in most of them the tumour has an aggressive behaviour with poor response to conventional chemotherapy. The genetic hallmark is the t(11;14)(q13;q32) translocation leading to the overexpression of cyclin D1, which is considered the initial oncogenic event. In addition to this translocation, MCL may carry a high number of secondary chromosomal and molecular alterations that target regulatory elements of the cell cycle machinery and senescence (BMI1/INK4/ARF/CDK4/RB1), DNA damage response pathways (ATM/CHK2/p53), and cell survival signals. The knowledge of these mechanisms and their influence on the behaviour of the tumour are facilitating the development of prognostic models with a more precise prediction of the clinical evolution of the patients. This information coupled with the availability of a new generation of innovative drugs targeting basic molecular process of the tumour cells, should facilitate the design of new therapeutic protocols able to overcome the resistance of this aggressive lymphoma to conventional treatments and improve the life expectancy of the patients.

KIS induces proliferation and the cell cycle progression through the phosphorylation of p27Kip1 in leukemia cells

CEM, MOLT4 and SUP-B15 cells were transduced with lentivirus-mediated siRNA KIS gene. The mRNA expressions of KIS were successfully reduced in all cell lines. On the other hand, the mRNA expressions of p27(Kip1) in CEM, MOLT4 and SUP-B15 cells were not affected by the transduction with siRNA KIS gene. We showed that KIS protein directly interacted with p27(Kip1) protein, and reduction of KIS inhibited the S10 phosphorylation of p27(Kip1) in leukemia cells. On these cells transfected with siRNA KIS, the inhibition of S10 phosphorylation of p27(Kip1) was strongly suppressed cell proliferation in a time-dependent manner. Moreover, the inhibition of S10 phosphorylation of p27(Kip1) increased a significant population in G0/G1 fraction. These data demonstrated that the KIS activity was induced during G0/G1, and it promotes cell cycle progression by phosphorylation of S10 on p27(Kip1). We showed that KIS mRNA expression was increased in primary leukemia specimens (acute myelogenous leukemia (AML); 37, myelodysplastic syndrome (MDS); 72, acute lymphoblastic leukemia (ALL); 23), and the mean ratios of KIS to G3PDH in AML, MDS and ALL specimens were 3.62+/-0.68, 3.27+/-0.73 and 3.17+/-0.58, respectively. Moreover, we found that KIS protein was overexpressed in all 132 adults cases of various leukemias, including 37 AML (8 M1, 12 M2, 2 M3, 7 M4, 8 M5), 72 MDS (42 RAEB-I, 30 REAB-II) and 23 ALL (23 L2). This study demonstrates that the elevated levels of KIS protein in leukemia cells promote the cell cycle progression in leukemia cells.