Leandro F. Dalmazzo

Constitutional hypomorphic telomerase mutations in patients with acute myeloid leukemia

Loss-of-function mutations in telomerase complex genes can cause bone marrow failure, dyskeratosis congenita, and acquired aplastic anemia, both diseases that predispose to acute myeloid leukemia. Loss of telomerase function produces short telomeres, potentially resulting in chromosome recombination, end-to-end fusion, and recognition as damaged DNA. We investigated whether mutations in telomerase genes also occur in acute myeloid leukemia. We screened bone marrow samples from 133 consecutive patients with acute myeloid leukemia and 198 controls for variations in TERT and TERC genes. An additional 89 patients from a second cohort, selected based on cytogenetic status, and 528 controls were further examined for mutations. A third cohort of 372 patients and 384 controls were specifically tested for one TERT gene variant. In the first cohort, 11 patients carried missense TERT gene variants that were not present in controls (P < 0.0001); in the second cohort, TERT mutations were associated with trisomy 8 and inversion 16. Mutation germ-line origin was demonstrated in 5 patients from whom other tissues were available. Analysis of all 3 cohorts (n = 594) for the most common gene variant (A1062T) indicated a prevalence 3 times higher in patients than in controls (n = 1,110; P = 0.0009). Introduction of TERT mutants into telomerase-deficient cells resulted in loss of enzymatic activity by haploinsufficiency. Inherited mutations in TERT that reduce telomerase activity are risk factors for acute myeloid leukemia. We propose that short and dysfunctional telomeres limit normal stem cell proliferation and predispose for leukemia by selection of stem cells with defective DNA damage responses that are prone to genome instability.

Determination of P‐glycoprotein, MDR‐related protein 1, breast cancer resistance protein, and lung‐resistance protein expression in leukemic stem cells of acute myeloid leukemia

The most primitive leukemic precursor in acute myeloid leukemia (AML) is thought to be the leukemic stem cell (LSC), which retains the properties of self‐renewal and high proliferative capacity and quiescence of the hematopoietic stem cell. LSC seems to be immunophenotypically distinct and more resistant to chemotherapy than the more committed blasts. Considering that the multidrug resistance (MDR) constitutive expression may be a barrier to therapy in AML, we have investigated whether various MDR transporters were differentially expressed at the protein level by different leukemic subsets.

Increased expression of miR-221 is associated with shorter overall survival in T-cell acute lymphoid leukemia.

BackgroundCD56 expression has been associated with a poor prognosis in lymphoid neoplasms, including T-cell acute lymphoblastic leukemia (T-ALL). MicroRNAs (miRNAs) play an important role in lymphoid differentiation, and aberrant miRNA expression has been associated with treatment outcome in lymphoid malignancies. Here, we evaluated miRNA expression profiles in normal thymocytes, mature T-cells, and T-ALL samples with and without CD56 expression and correlated microRNA expression with treatment outcome.MethodsThe gene expression profile of 164 miRNAs were compared for T-ALL/CD56+ (n=12) and T-ALL/CD56- (n=36) patients by Real-Time Quantitative PCR. Based on this analysis, we decided to evaluate miR-221 and miR-374 expression in individual leukemic and normal samples.ResultsmiR-221 and miR-374 were expressed at significantly higher levels in T-ALL/CD56+ than in T-ALL/CD56- cells and in leukemic blasts compared with normal thymocytes and peripheral blood (PB) T-cells. Age at diagnosis (15 or less vs grater than 15 years; HR: 2.19, 95% CI: 0.98-4.85; P=0.05), miR-221 expression level (median value as cut off in leukemic samples; HR: 3.17, 95% CI: 1.45-6.92; P=0.004), and the expression of CD56 (CD56-vs CD56+; HR: 2.99, 95% CI: 1.37-6.51; P=0.006) were predictive factors for shorter overall survival; whereas, only CD56 expression (HR: 2.73, 95% CI: 1.03-7.18; P=0.041) was associated with a shorter disease-free survival rate.ConclusionsmiR-221 is highly expressed in T-ALL and its expression level may be associated with a poorer prognosis.

The presence of CD56/CD16 in T-cell acute lymphoblastic leukaemia correlates with the expression of cytotoxic molecules and is associated with worse response to treatment.

Some cases of T‐cell acute lymphoblastic leukaemia (ALL) express markers found in natural‐killer (NK) cells, such as CD56 and CD16. Out of 84 T‐cell ALL cases diagnosed at our Institution, CD56 and/or CD16 was detected in 24 (28·5%), which we designated T/NK‐ALL group. Clinical features, laboratory characteristics, survival and expression of cytotoxic molecules were compared in T/NK‐ALL and T‐ALL patients. Significant differences were observed regarding age (24·9 vs. 16·4 years in T/NK‐ALL and T‐ALL, respectively, P = 0·006) and platelet counts (177 × 109/l vs. 75 × 109/l in T/NK‐ALL and T‐ALL, respectively, P = 0·03). Immunophenotypic analysis demonstrated that CD34, CD45RA and CD33 were more expressed in T/NK‐ALL patients, whereas CD8 and terminal deoxynucleotidyl transferase were more expressed in T‐ALL patients (P < 0·05). The mean overall survival (863 vs. 1869 d, P = 0·02) and disease‐free survival (855 vs. 2095 d, P = 0·002) were shorter in patients expressing CD56/CD16. However, multivariate analysis identified CD56/CD16 as an independent prognostic factor only for DFS. Cytotoxic molecules were highly expressed in T/NK‐ALL compared to T‐ALL. Perforin, granzyme B and TIA‐1 were detected in 12/17, 4/17 and 7/24 T/NK‐ALL patients and in 1/20, 0/20 and 1/20 T‐ALL respectively (P < 0·001, P = 0·036 and P = 0·054). Therefore, the presence of CD56/CD16 was associated with distinct clinical features and expression of cytotoxic molecules in the blasts.

Potential roles of microRNA-29a in the molecular pathophysiology of T-cell acute lymphoblastic leukemia

Recent evidence has shown that deregulated expression of members of the microRNA‐29 (miR‐29) family may play a critical role in human cancer, including hematological malignancies. However, the roles of miR‐29 in the molecular pathophysiology of T‐cell acute lymphoblastic leukemia (T‐ALL) has not been investigated. Here, we show that lower levels of miR‐29a were significantly associated with higher blast counts in the bone marrow and with increased disease‐free survival in T‐ALL patients. Furthermore, miR‐29a levels are extremely reduced in T‐ALL cells compared to normal T cells. Microarray analysis following introduction of synthetic miR‐29a mimics into Jurkat cells revealed the downregulation of several predicted targets (CDK6, PXDN, MCL1, PIK3R1, and CXXC6), including targets with roles in active and passive DNA demethylation (such as DNMT3a, DNMT3b, and members of the TET family and TDG). Restoring miR‐29a levels in Jurkat and Molt‐4 T‐ALL cells led to the demethylation of many genes commonly methylated in T‐ALL. Overall, our results suggest that reduced miR‐29a levels may contribute to the altered epigenetic status of T‐ALL, highlighting its relevance in the physiopathology of this disease.

The association of ICAM-1 Exon 6 (E469K) but not of ICAM-1 Exon 4 (G241R) and PECAM-1 Exon 3 (L125V) polymorphisms with the development of differentiation syndrome in acute promyelocytic leukemia.

The use of all trans‐retinoic acid (ATRA) is the basis of treatment of acute promyelocytic leukemia (APL) and represents the paradigm of differentiation therapy. In general, ATRA is well‐tolerated but may be associated with a potentially lethal side‐effect, referred to as retinoic acid or differentiation syndrome (DS). The cellular and molecular mechanisms of DS are poorly understood and involve changes in the adhesive qualities and cytokine secretion of leukemic cells during ATRA‐induced differentiation. As leukocyte extravasation is a key event in DS pathogenesis, we analyzed the association between the polymorphisms at Exon 4 (G241R) and Exon 6 (E469K) of ICAM‐1 and Exon 3 (L125V) of PECAM‐1 genes with DS development in APL patients treated with ATRA and anthracyclines. DS was diagnosed in 23/127 (18.1%) APL patients at an average of 11.5 days after the start of ATRA. All patients presented respiratory distress associated with increased ground‐glass opacity in chest radiographies. Other accompanying symptoms were: fever not attributable to infection (65.2%), generalized edema (37.5%), weight gain (37.5%), and impairment of renal function (8.6%). We detected an association between development of DS and the AA genotype at Codon 469 of ICAM‐1 (odds ratio of 3.5; 95% confidence interval: 1.2–10.2). Conversely, no significant association was detected between G241R or L125V polymorphisms at Exon 4 of ICAM‐1 and Exon 3 of PECAM‐1, respectively. Our results suggest that susceptibility to DS in APL patients may be influenced by genetic variation in adhesion molecule loci.

Antibody-targeted horseradish peroxidase associated with indole-3-acetic acid induces apoptosis in vitro in hematological malignancies

Indole-3-acetic acid (IAA), when oxidized by horseradish peroxidase (HRP), is transformed into cytotoxic molecules capable of inducing cell injury. The aim of this study was to test if, by targeting hematopoietic tumors with HRP-conjugated antibodies in association with IAA treatment, there is induction of apoptosis. We used two lineages of hematologic tumors: NB4, derived from acute promyelocytic leukemia (APL) and Granta-519 from mantle cell lymphoma (MCL). We also tested cells from 12 patients with acute myeloid leukemia (AML) and from 10 patients with chronic lymphocytic leukemia (CLL). HRP targeting was performed with anti-CD33 or anti-CD19 antibodies (depending on the origin of the cell), followed by incubation with goat anti-mouse antibody conjugated with HRP. Eight experimental groups were analyzed: control, HRP targeted, HRP targeted and incubated with 1, 5 and 10mM IAA, and cells not HRP targeted but incubated with 1, 5 and 10mM IAA. Apoptosis was analyzed by flow cytometry using annexin V-FITC and propidium iodide labeling. Results showed that apoptosis was dependent on the dose of IAA utilized, the duration of exposure to the prodrug and the origin of the neoplasia. Targeting HRP with antibodies was efficient in activating IAA and inducing apoptosis.

O valor da imunofenotipagem para o diagnóstico do Mieloma Múltiplo e na avaliação da doença residual mínima

Os plasmocitos normais podem ser diferenciados dos presentes no mieloma multiplo por imunofenotipagem. Os normais sao CD45+, CD19+, CD20+, CD38++, CD56-/fraco, CD138+, mIg-, cIg policlonal. Por outro lado, os plasmocitos do mieloma multiplo sao monoclonais (cIg) e aproximadamente 80% sao CD19-CD56+ e 20% CD19-CD56-. O perfil na leucemia plasmocitaria primaria e semelhante ao do mieloma, embora a positividade para o CD56 ocorra em 45% dos casos. Na gamopatia monoclonal de causa indeterminada existe uma mistura de plasmocitos normais e neoplasicos, que tem perfil semelhante ao do mieloma multiplo. A doenca residual na medula e importante para estimar a resposta terapeutica e pode ser avaliada por citometria de fluxo e pela reacao da polimerase em cadeia para o rearranjo da cadeia pesada da Ig. A citometria apresenta sensibilidade de 10-4 a 10-5, e realizada em aproximadamente duas horas e a sua aplicabilidade chega a 90%. O PCR qualitativo tem sensibilidade de 10-6 enquanto o quantitativo, 10-5. Em ambos, o tempo para a realizacao e maior (2-3 dias), com aplicabilidade de 75%.