The Role of PTEN in Myeloid Malignancies

PTEN deletion in the mouse and in the zebrafish highlights the essential role of this tumor suppressor in the development of myeloid malignancies, in particular acute myeloid leukemia and myeloproliferative disorders. In humans, extensive genetic sequences of myeloid malignancies did not reveal recurrent PTEN mutations and deletions. However, PTEN was shown to be functionally inactivated in several acute myeloid leukemia and chronic myeloid leukemia samples, through both post-trasductional modifications, changes in protein levels and cellular compartmentalization. Notably, non genomic inactivation of PTEN in myeloid malignancies could represent a challenging therapeutic opportunity for these diseases. Targeting those mechanisms that affect PTEN function could indeed promote PTEN reactivation with consequent cancer selective apoptosis induction. In this review we will describe the role of PTEN in the development of myeloid malignancies.

When collateral vessels matter: asymptomatic Leriche syndrome

While acute arterial occlusion causes life-threatening ischemia and organ damage requiring urgent revascularization, the incidental identification of arterial occlusions in asymptomatic patients represents a therapeutic dilemma in clinicians. Does chronic asymptomatic artery occlusion require specific treatment?

Small bowel cancer diagnosis: role of nuclear magnetic resonance

The diagnosis of small intestine tumors is challenging. Even in the era of modern medicine, standard approaches including echography, computed tomography-scan and conventional endoscopy are unable to reveal small bowel lesions. Video-capsule has substantially improved the evaluation of small bowel; however this procedure cannot be proposed to all patients and in particular to those experiencing intestine sub-occlusion. Nuclear magnetic resonance (NRM) of the abdomen is an additional diagnostic approach that offers high sensitivity in the identification of small bowel lesions. Here, we describe a case of small bowel neoplasia indentified with NRM of the abdomen.

The challenging diagnosis of pancreatic masses: not all tumors are cancers

In the elderly patients, where biopsy-induced complications could outweigh the benefit, the identification of pancreatic masses is generally referred to as a synonymous of pancreatic cancer and patients are dismissed with no further options than palliative and supportive care. Notwithstanding, not all pancreatic tumors are cancers and therefore alternative diagnoses need to be investigated, especially when patients are unfit for invasive diagnostic procedures. Here, we report a case of an aged patient that was admitted to an internal medicine division for a previously diagnosed pancreatic cancer. The reassessment of the diagnosis has allowed identifying the pancreatic mass as a manifestation of focal pancreatitis in the context of an IgG4-related disease. Accordingly, patient was treated with steroids with rapid clinical improvement. This clinical case suggests that autoimmune diseases should always be considered in the differential diagnosis of pancreatic masses of the elderly.

BCR-ABL promotes PTEN downregulation in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a myeloproliferative disorder characterized by the t(9;22) translocation coding for the chimeric protein p210 BCR-ABL. The tumor suppressor PTEN plays a critical role in the pathogenesis of CML chronic phase, through non genomic loss of function mechanisms, such as protein down-regulation and impaired nuclear/cytoplasmic shuttling. Here we demonstrate that BCR-ABL promotes PTEN downregulation through a MEK dependent pathway. Furthermore, we describe a novel not recurrent N212D-PTEN point mutation found in the EM2 blast crisis cell line.

HAUSP compartmentalization in chronic myeloid leukemia

INTRODUCTION

PTEN plays an essential role in the pathogenesis of chronic myeloid leukemia. Recently, we have shown that BCR-ABL promotes PTEN nuclear exclusion, through the modulation of HAUSP activity.

OBJECTIVES

Here, we investigate HAUSP cellular compartmentalization in primary CML samples.

RESULTS

While in normal CD34 positive cells HAUSP is expressed mostly in the nucleus, in CML CD34 cells HAUSP is expressed both in the nuclear bodies and in the cytoplasm.

CONCLUSIONS

This observation suggests that HAUSP behaves as a shuttling protein in CML. It can bind to BCR-ABL in the cytosol, where it is phosphorylated on tyrosine residues, and it maintains the proper compartmentalization in the nuclear bodies, where it acts as part of a PML network to regulate PTEN de-ubiquitination.

Valproate enhances imatinib-induced growth arrest and apoptosis in chronic myeloid leukemia cells

BACKGROUND

The objective of this study was to evaluate the ability of the clinically available histone deacetylase (HDAC) inhibitor valproate to enhance the cytotoxicity of the Bcr-Abl inhibitor imatinib in imatinib-resistant cell lines.

METHODS

Interactions between imatinib, and valproate have been examined in imatinib-sensitive and -resistant chronic myeloid leukemia (CML)cell lines (K562, KCL-22, CML-T1) and in bone marrow mononuclear cells (MNCs) derived from imatinib-resistant CML patients.

RESULTS

In imatinib-sensitive cell lines, cotreatment with imatinib 0.5 muM and valproate 5 microM for 48 hours potently enhanced imatinib-induced growth arrest and apoptosis. In resistant cell lines and in primary MNCs derived from imatinib-rsistant patients, valproate restored sensitivity to the cytotoxic effects of imatinib. Coexposure of cells to valproate and imatinib was associated with repression of several genes involved in Bcr-Abl transformation. In particular, the combination valproate-imatinib downregulated the expression of Bcr-Abl and the antiapoptotic protein Bcl-2, which is particularly overexpressed in imatinib-resistant clones.

CONCLUSIONS

Data from this study suggested that administration of the clinically available HDAC inhibitor valproate may be a powerful strategy to enhance cytotoxic effects of imatinib in those patient resistant to imatinib or in which complete cytogenetic remission has been not reached.

Increase in platelet count in older, poor-risk patients with acute myeloid leukemia or myelodysplastic syndrome treated with valproic acid and all-trans retinoic acid

BACKGROUND

The authors investigated the efficacy and safety of the histone deacetylase inhibitors valproic acid (VPA) and all-trans retinoic acid (ATRA) as differentiation agents in a cohort of older, poor-risk patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS).

METHODS

Twenty older patients with recurrent or refractory AML or MDS were treated in a Phase II protocol with sequential VPA and ATRA therapy. VPA was started at a dose of 10 mg/kg per day and then escalated to achieve the serum concentration of 45-100 microg/mL. ATRA was added at 45 mg/square meters (sm) per day when VPA reached the target serum concentration. Only patients treated continuously for > or = 2 months were considered evaluable.

RESULTS

Hematologic improvement, according to World Health Organization criteria, was observed in 6 of 20 patients enrolled in the protocol but in 6 of 11 considered evaluable. In five patients, a major platelet response was observed, achieving platelet transfusion independence. Three of these five patients also exhibited a minor erythroid response. A sixth patient showed both a minor erythroid response and a platelet response. The median duration of response was 189 days (range, 63-550 days). No significant reduction in the blast count was observed. Grade 3 neurocortical toxicity was observed in four patients. Severe bone pain was experienced by 4 patients (2 Grade 4 and 2 Grade 3) and was associated with an increase in the peripheral blast cell count. Treatment with ATRA did not modify the response observed with VPA alone.

CONCLUSIONS

Differentiation therapy with VPA was of clinical benefit in approximately 30% of elderly patients with AML and MDS of the refractory anemia with excess of blast type with unfavorable prognostic features. A striking platelet transfusion independence lasting several months may be obtained in some patients, reducing the burden of palliative care and improving the quality of life.

Autologous HSCT for severe progressive multiple sclerosis in a multicenter trial: impact on disease activity and quality of life

Hematopoietic stem cell transplantation (HSCT) has been proposed for the treatment of severe multiple sclerosis (MS). In a phase 2 multicenter study we selected 19 non-primary progressive MS patients showing high disease activity on the basis of both brain magnetic resonance imaging (MRI) and sustained clinical deterioration despite conventional treatments. After stem cell mobilization with cyclophosphamide (CY) and filgrastim, patients were conditioned with BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea), cytosine arabinoside, etoposide, and melphalan (BEAM) followed by antithymocyte globulin (ATG). Unmanipulated peripheral blood stem cells (PBSCs) were then infused. No maintenance treatment was administered with a median follow-up of 36 months (range, 12 to 72 months). All patients showed clinical stabilization or improvement; 3 subsequently deteriorated, 1 beyond the baseline. No MRI active lesions were detected after the HSCT except in 1 patient who showed a new lesion at 4.5 years. Infections were limited and restricted to 3 months after HSCT. Health-related quality of life was assessed through the 54-item MS quality of life (MSQOL-54) questionnaire, showing a statistically significant improvement in both composite scores and in most of the individual domains. HSCT is able to induce a prolonged clinical stabilization in severe progressive MS patients, resulting in both sustained treatment-free periods and quality of life improvement.

Quantitative assessment of WT1 expression by real time quantitative PCR may be a useful tool for monitoring minimal residual disease in acute leukemia patients

In order to verify if quantitative assessment of the WT1 transcript amount by the real time quantitative PCR (RQ-PCR) can be used as a marker for minimal residual disease detection, the WT1 transcript amount was determined in BM and PB samples of patients with myeloid and lymphoid acute leukemia, in normal controls, in regenerating bone marrow samples and in purified CD34-positive cells from normal subjects. In 10 patients bearing a fusion gene transcript suitable for minimal residual disease quantitative assessment, we performed a simultaneous analysis of the WT1 and of the fusion-gene transcript at sequential time intervals during follow-up. Sequential WT1 analysis was also performed in five AML patients lacking additional molecular markers. The data obtained show that normal and regenerating BM samples and purified CD34-positive cells consistently express minimal amounts of WT1 transcript and that this is extremely low and frequently undetectable in normal PB. By contrast, high levels of WT1 expression are present in the BM and PB samples of all acute leukemia (AL) cases at diagnosis. The WT1 levels during follow-up were found to follow the pattern of the other molecular markers (fusion gene transcripts) used for MRD monitoring and increased WT1expression in the BM and/or PB during follow-up of AL patients was always found to be predictive of an impending hematological relapse.

Assessment of minimal residual disease (MRD) in CBFbeta/MYH11-positive acute myeloid leukemias by qualitative and quantitative RT-PCR amplification of fusion transcripts

The inv(16)(p13q22) chromosomal rearrangement associated with FAB M4Eo acute myeloid leukemia (AML) subtype is characterized by the presence of the CBFbeta/MYH11 fusion transcript that can be used to detect minimal residual disease (MRD). However, qualitative RT-PCR studies of MRD have so far produced conflicting results and seem of limited prognostic value. We have evaluated retrospectively MRD in a large series of CBFbeta/MYH11-positive patients employing both qualitative and quantitative (real-time PCR) approaches. 186 bone marrow samples from 36 patients were examined with a median follow-up of 27.5 months; 15 patients relapsed during follow-up. In qualitative studies, carried out by 'nested' RT-PCR assay, all patients in complete remission (CR) immediately after induction/consolidation therapy were found to be PCR positive. However, follow-up samples at later time points were persistently negative (except one case) in patients remaining in continuous CR (CCR) for more than 12 months. 16 patients were evaluated by quantitative real-time PCR assay: CBFbeta/MYH11 transcript copy number was normalized for expression of the housekeeping gene ABL, expressed as fusion gene copy number per 10(4) copies of ABL. A 2-3 log decline in leukemic transcript copy number was observed after induction/consolidation therapy. After achieving CR, the mean copy number was significantly higher in patients destined to relapse compared to patients remaining in CCR (151 vs 9, P < 0.0001 by Mann-Whitney test). Moreover, in CCR patients, the copy number dropped below the detection threshold after the treatment protocol was completed and remained undetectable in subsequent MRD analysis in accordance with results obtained by qualitative RT-PCR. On the contrary, in the seven patients who relapsed, the copy number in CR never declined below the detection threshold; thus a cut-off value discriminating these two groups of patients could be established. The findings of our study, if confirmed, might confer an important predictive value to quantitative real-time PCR determinations of MRD in patients with inv(16) leukemia.

BCR/ABL transcripts and leukemia phenotype: an unsolved puzzle

The Philadelphia chromosome, arising as a consequence of the t(9;22) translocation, is one of the most frequent and certainly the most known cytogenetic abnormality present in human hematological malignancies. Unlike the vast majority of the other translocations, its presence is not restricted to a specific leukemia phenotype, but is found associated with chronic myelogenous leukemia as well as with a large percentage of acute lymphoblastic leukemias, particularly in elderly patients. Although its molecular counterpart is always represented by a rearrangement between the BCR and the ABL genes, this shows a certain degree of molecular variability. The pathogenetic relationship with the different leukemia phenotypes which have been found to be associated still awaits to be fully elucidated. However, a number of old and more recent observations seem to suggest that not only qualitative differences in the type of BCR/ABL proteins expressed, but also quantitative variations in their total level within the cells may have an important role in determining the leukemia phenotype.

The common TEL/AML1 rearrangement does not represent a frequent event in acute lymphoblastic leukaemia occuring in children with Down syndrome

Individuals with constitutional trisomy 21 (Down syndrome) are at increased risk of developing acute leukaemias, both of myeloid and lymphoid lineage. Although the cause of leukaemia in Down syndrome (DS) remains unknown, potential candidate genes include the ones on chromosome 21, and in particular AML1, the rearrangement of which in the t(8,21) is associated with the French-American-British (FAB) classification M2 subtype of acute myeloid leukaemia (AML) in the general population and has been described in Down patients with AML-M2. Recently, a new rearrangement involving AML1, the t(12;21), producing the TEL/AML1 hybrid transcript, has been described by molecular analysis as the most recurrent genetic lesion in childhood acute lymphoblastic leukemia (ALL). In order to investigate whether the t(12;21) could give a molecular clue as to the precise basis of the etiologic association between DS and acute lymphoblastic leukemia, we tested a series of 11 consecutive cases of ALL in DS children for the presence of the TEL/AML1 transcript, by RT-PCR analysis. We report absence of the TEL/AML1 rearrangement among the 11 cases tested. This data may be suggestive of alternative pathways involved in the pathogenesis of ALL in children with constitutional trisomy 21.

Molecular events in chronic myeloid leukemia progression

Chronic myelogenous leukemia presents two distinct clinical phases: the chronic phase is characterised by a marked expansion of the myeloid compartment which still retains a normal differentiative capacity, whereas a differentiation block is the clinical hallmark of the acute transformation. The molecular mechanism underlying the CML progression are still poorly understood. The occurrence of additional molecular lesions, involving the p53, the RAS and the p16 genes may complement and fulfil the BCR/ABL transforming potential, finally leading to an acute leukemic phenotype. However, several lines of evidence suggest that also quantitative changes of the BCR/ABL transcript amounts could explain the progression of the leukemic phenotype in the BCR/ABL-positive hematologic malignancies.

Consistent amounts of acute leukemia-associated P190BCR/ABL transcripts are expressed by chronic myelogenous leukemia patients at diagnosis

In chronic myelogenous leukemia (CML), the Philadelphia (Ph) chromosome translocation results in the formation of BCR/ABL genes, normally transcribed in two types of hybrid transcripts with a b2a2 or b3a2 BCR/ABL junction, which give origin to 210-kD fusion proteins (P210). A third type of BCR/ABL (with e1a2 type of junction) has been identified in approximately 50% of the Ph-positive acute lymphoblastic leukemia (Ph+ALL) cases and results in the production of a BCR/ABL protein of 190 kD (P190). The presence of this transcript has been associated almost exclusively with the presence of an acute leukemia phenotype. By contrast, here we describe that in addition to transcripts with the b2a2 and b3a2 types of junction corresponding to the P210 proteins, virtually all CMLs at diagnosis bear also BCR/ABL transcripts showing the e1a2 type of junction, which correspond to the acute leukemia-associated P190 protein. With a quantitative polymerase chain reaction assay we found that the amount of the e1a2 mRNA present in CMLs in chronic phase, although in absolute amount much lower than that present in Ph+ ALLs, represents in most cases approximately 20% to 30% of the total BCR/ABL transcripts. Moreover, using a novel and very sensitive Western blot technique, we detected relevant amounts of P190 protein in addition to P210 from peripheral cells of two of the patients.

Genetic analysis of chromosome 13 deletions in BCR/ABL negative chronic myeloproliferative disorders

Chromosomal deletions of band 13q14 occur recurrently in BCR/ABL negative chronic myeloproliferative disorders (CMPD), including myelosclerosis with myeloid metaplasia (MMM), polycythemia vera (PV), essential thrombocythemia (ET), juvenile chronic myeloid leukemia (JCML), and the so-called BCR/ABL- chronic myeloid leukemia (CML). The RBI tumor suppressor locus, mapping to 13q14, has long since been hypothesized as the important gene. In this report, we have determined the frequency of 13q14 deletions at the molecular level in a large panel of BCR/ABL- CMPD at different disease stages and performed a detailed genetic analysis of gross rearrangements/deletions and point mutations of the RBI gene in these disorders. Our data show that molecular deletions of 13q14 are detected in a relatively large fraction of BCR/ABL- CMPD (38%), that they appear to be more frequent in MMM than in other BCR/ABL- CMPD, and that they may be present at diagnosis or occur during blastic evolution of the neoplasia. The RBI gene displayed a germline configuration in all BCR/ABL- CMPD tested, suggesting that 13q14 deletions in these disorders affect a tumor suppressor locus distinct from RBI.

Polyclonal haemopoieses associated with long-term persistence of the AML1-ETO transcript in patients with FAB M2 acute myeloid leukaemia in continous clinical remission

The t(8;21) (q22;q22) translocation is a recurring chromosomal abnormality observed in about 20-40% of AML patients with subtype FAB M2 (AML-M2). The molecular facet of this translocation is represented by the formation of a new hybrid gene, the AML1-ETO, which is regularly transcribed in a chimaeric mRNA and translated into a new fusion protein believed to have a key role in the pathogenesis of this type of leukaemia. We looked for the presence of AML1-ETO transcripts, by RT-PCR, in 49 unselected patients affected by AML-M2 diagnosed at various Italian Institutions. A hybrid transcript was detected in 11 cases (23%). Minimal residual disease status was investigated in three patients in continuous complete remission (CCR) after a median follow-up of 44 months; at least one sample from each subject was found positive for the AML1-ETO transcript suggesting a long-term persistence of t(8;21) leukaemic cells. In two female patients in CCR a 'clonality' analysis was performed on peripheral blood DNA by exploiting the X chromosome inactivation pattern of the human androgen-receptor gene (HUMARA); in both cases the results were consistent with the presence of a polyclonal haemopoiesis. Our data confirm that the persistence of residual cells expressing the AML1-ETO transcripts is a frequent occurrence even in patients with long-term remission; on the other hand, clonality assays indicate that in t(8;21) leukaemias long-term remission haemopoiesis is sustained by a polyclonal bone marrow reconstitution.