High levels of vascular endothelial growth factor receptor-2 correlate with shortened survival in chronic lymphocytic leukemia

Vascular endothelial growth factor receptor-2 (VEGFR-2), also termed KDR, is a high-affinity vascular endothelial growth factor (VEGF) receptor. VEGFR-2 plays a role in de novo blood vessel formation and hematopoietic cell development. Recently, we found that chronic lymphocytic leukemia (CLL) cells express high levels of VEGF. Therefore, we sought to investigate the role of VEGFR-2 in CLL. Using Western blot analysis, we first determined that VEGFR-2 is present in peripheral blood CLL cells. We then quantified the cellular levels of VEGFR-2 protein using a solid-phase radioimmunoanalysis in peripheral blood cells from 216 patients with CLL. As control, we used peripheral blood mononuclear cells (PBMNCs) from 31 hematologically normal individuals. The median of VEGFR-2 levels detected in the control samples was assigned a value of 1.0, and VEGFR-2 protein levels were normalized to the control median value. The median level of VEGFR-2 in CLL cells was 1.57. Patients with VEGFR-2 levels higher than 1.57 had elevated lymphocyte counts, severe anemia, elevated beta(2)-microglobulin and advanced-stage disease. Elevated VEGFR-2 levels were also associated with statistically significantly shorter survival (35.4 versus 60.1 months; P < 0.01). Our data indicate that cellular VEGFR-2 levels may serve as a prognostic factor in CLL. Further studies should investigate the biological implications of these findings and the effect of the interaction between VEGF and VEGFR-2 on CLL cell proliferation.

Clinical relevance of Flt1 and Tie1 angiogenesis receptors expression in B-cell chronic lymphocytic leukemia (CLL)

Angiogenesis, a complex process tightly controlled by several molecules including vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) along with their receptors, plays a major role in the growth and metastasis of solid tumors. The expression and production of VEGF and bFGF have been documented in numerous solid tumors and hematopoietic neoplasms. Having recently shown increased expression of cellular VEGF in the leukemic cells of patients with chronic lymphocytic leukemia (CLL) we decided to investigate the expression of angiogenic receptors Flt1 and Tie1. Levels of Tie1 and Flt1 proteins were measured in leukemic cells from 231 patients with B-cell CLL using Western blot analysis and solid-phase radioimmunoassay (RIA). A strong correlation was found between Flt1 and Tie1 levels and white blood cell count (WBC) and absolute lymphocyte counts. Levels of Flt1 but not Tie1 correlated with levels of cellular VEGF. Interestingly, Tie1 correlated well with Rai stage (P=0.04). Flt1 and Tie1 did not correlate with survival, although when we evaluated the patients with early disease (Rai stage 0-II), higher levels of Tie1 but not of Flt1 correlated with worse survival. These data suggest that Tie1 plays a role in the early stages of B-cell CLL and as the disease progresses, the tumor cells become independent from the effects of Tie1. Further studies are now needed to dissect the mechanisms responsible for this phenomenon.

The antiangiogenic protein kinase inhibitors SU5416 and SU6668 inhibit the SCF receptor (c-kit) in a human myeloid leukemia cell line and in acute myeloid leukemia blasts

SU5416 and SU6668 are potent antiangiogenic small-molecule inhibitors of receptor tyrosine kinases, including those of the vascular endothelial growth factor and platelet-derived growth factor receptor families. The stem cell factor (SCF) receptor, c-kit, is structurally related to these receptors and, although not expressed on mature peripheral blood cells, is expressed in leukemic blasts derived from 60% to 80% of acute myeloid leukemia (AML) patients. The c-kit kinase inhibitory activity of SU5416 and SU6668 was evaluated in MO7E cells, a human myeloid leukemia cell line. Tyrosine autophosphorylation of the receptor, induced by SCF, was inhibited in these cells by SU5416 and SU6668 in a dose-dependent manner (inhibitory concentration of 50% [IC(50)] 0.1-1 microM). Inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, a signaling event downstream of c-kit activation, was also inhibited in a dose-dependent manner. Both compounds also inhibited SCF-induced proliferation of MO7E cells (IC(50) 0.1 microM for SU5416; 0.29 microM for SU6668). Furthermore, both SU5416 and SU6668 induced apoptosis in a dose- and time-dependent manner as measured by the increase in activated caspase-3 and the enhanced cleavage of its substrate poly(ADP-ribose) polymerase. These findings with MO7E cells were extended to leukemic blasts from c-kit(+) patients. In patient blasts, both SU5416 and SU6668 inhibited SCF-induced phosphorylation of c-kit and ERK1/2 and induced apoptosis. These studies indicate that SU5416 and SU6668 inhibit biologic functions of c-kit in addition to exhibiting antiangiogenic properties and suggest that the combination of these activities may provide a novel therapeutic approach for the treatment of AML.

Loss of heterozygosity on chromosome 5 in adults with acute lymphoblastic leukemia

Cytogenetic abnormalities are among the most important pretreatment predictors of outcome in patients with acute lymphoblastic leukemia (ALL). Deletions of genetic material can result in loss of tumor suppressor genes or other translation products that are crucial in maintaining an orderly cell cycle sequence or viability of the apoptotic cascade. Chromosome 5 contains many genes that are relevant in hematopoiesis. Deletions of chromosome 5 or parts thereof are found frequently in myelodysplastic syndromes (MDS) and acute myeloid leukemias (AML) where they are associated with a poor prognosis. Although abnormalities of chromosome 5 are not commonly detected by cytogenetic analysis in patients with acute lymphoblastic leukemias, we hypothesized that loss of heterozygosity (LOH) of microsatellite markers on chromosome 5 may occur more frequently and likewise influence outcome in these patients. Therefore, we analyzed peripheral blood and bone marrow samples of 41 adults with a diagnosis of ALL for LOH by polymerase chain reaction (PCR) and correlated our findings with overall survival of patients with and without LOH. LOH for at least one microsatellite marker was found in seven of 41 patients (17%). All patients demonstrated LOH on the long arm of chromosome 5. In three patients, LOH was extended to 5p. A region of minimal deletion which overlapped in all seven patients could be localized between markers D5S410 and D5S436 corresponding to chromosomal location 5q31-33 which is similar to the area of minimal deletion seen in AML. None of these patients showed involvement of chromosome 5 by cytogenetic analysis. We conclude that patients with ALL have LOH for gene segments on chromosome 5, especially 5q, more frequently than expected from cytogenetic studies. Although, unlike AML, no significant impact on prognosis could be found between patients with and without LOH on chromosome 5. The current data suggest that 5q abnormalities are not specific for AML and can also occur in patients with ALL.

Comparison of outcome in acute myelogenous leukemia patients with translocation (8;21) found by standard cytogenetic analysis and patients with AML1/ETO fusion transcript found only by PCR testing

Patients with normal-karyotype acute myelogenous leukemia (NKAML) may have undetected genetic abnormalities that could affect prognosis. Screening for known AML-specific genetic abnormalities using the reverse transcription polymerase chain reaction (RT-PCR) may help in arriving at a more definitive prognosis. To test this hypothesis, 104 patients without translocation (8;21) and inversion(16), as shown by standard cytogenetic (SC) analysis, were screened for these two genetic abnormalities using RT-PCR. Western blot analysis for the AML1/ETO fusion protein and fluorescent in situ hybridization (FISH) analysis for t(8;21) were performed in patients for whom we had samples. The characteristics and outcome after high-dose cytarabine containing treatments in five patients with t(8;21) shown by RT-PCR alone were then compared to 21 patients with t(8;21) detected using SC analysis. Eight of the 104 patients had masked t(8;21) and none had masked inv(16), as shown by RT-PCR. Five of 54 patients with NKAML had a detectable AML1/ETO fusion RNA transcript. Western blot analysis showed the AML1/ETO fusion protein in four of the seven patients for whom we had samples among the eight with masked t(8;21) shown by RT-PCR. All patients with t(8;21) shown by RT-PCR had negative FISH results. Ninety percent (n=19) of the patients with t(8;21) shown by SC analysis and 40% (n= 2) of the patients with t(8;21) shown by RT-PCR alone achieved a complete remission (P value 0.03). These data suggest that the outcome of NKAML patients with t(8;21) shown by RT-PCR is not equivalent to patients with t(8;21) by SC studies.

Insights into the biologic and molecular abnormalities in adult acute lymphocytic leukemia

The last 3 decades have seen much progress in the treatment and outcome of patients with ALL. Unfortunately, the success that has been achieved in children with ALL has not yet been translated into adult patients. Insight into the biologic and molecular abnormalities in ALL may, however, provide the necessary clues that allow a clearer understanding of the crucial differences in the behavior of ALL in different groups of patients. As the molecular basis of the disease is deciphered, new targets are discovered that may prove useful for therapeutic interventions in the future.

The prognostic significance of p16(INK4a)/p14(ARF) locus deletion and MDM-2 protein expression in adult acute myelogenous leukemia

BACKGROUND

The p16(INK4a) locus encodes two distinct proteins, p16(INK4a) and p14(ARF). Although p16(INK4a) and p15(INK4b) are involved in the phosphorylation of the retinoblastoma (Rb) protein, p14(ARF) interacts with the MDM-2 oncoprotein antagonizing its function as a suppressor of p53. The role of deletions of p16(INK4a)/p14(ARF) and p15(INK4b) and expressions of MDM-2 in myeloid leukemias and its influence on prognosis remain unclear.

METHODS

The authors analyzed deletions of p16(INK4)/p14(ARF) and p15(INK4b) in 74 adults with acute myeloid leukemia (AML) by Southern blotting. Western blotting was used to determine Rb protein phosphorylation in patients with deletions of p16(INK4)/p14(ARF) and p15(INK4b). Then, they analyzed the levels of MDM-2 protein expression and correlated it with prognosis in an expanded population of 79 adults with AML by immunoblot analysis and solid-phase radioimmunoassay.

RESULTS

Deletions of p16(INK4a)/p14(ARF) and/or p15(INK4b) occurred in 4 of 74 patients (5%) (hemizygous in 3, homozygous in 1 patient). Although the complete remission (CR) rate was similar (79% vs. 50%; P = 0.187), CR duration (10 vs. 46 weeks; P < 0.001), event free survival rate (EFS; 6 vs. 85 weeks; P < 0.004) and overall survival rate (11 vs. 86 weeks; P = 0.001) were significantly shorter in patients with deletions of p16(INK4a)/p14(ARF) and/or p15(INK4b). Thirty-seven (47%) of 79 patients studied for MDM-2 showed increased MDM-2 expression. These patients had a significantly shorter EFS rate (50 vs. 64 weeks; P = 0.023) and a trend for shorter CR duration (24 vs. 53 weeks; P = 0.07). Overall survival rate was not significantly different (50 vs. 84 weeks; P = 0.136).

CONCLUSIONS

The authors concluded that 1) deletions of p16(INK4a)/p14(ARF) and/or p15(INK4b) occur with low incidence in patients with AML; 2) patients with deletions of p16(INK4a)/p14(ARF) and/or p15(INK4b) have a significantly shorter CR duration, EFS rate, and overall survival rate than do patients without deletions; (3) overexpression of MDM-2 is common in AML and is associated with shorter CR duration and EFS rate. Mechanisms other than p14(ARF) deletion are responsible for MDM-2 overexpression, and this overexpression may play a role in the biology of the disease.

Spontaneous remission of granulocyte colony-stimulating factor-associated leukemia in a child with severe congenital neutropenia

Leukemia is observed with increased frequency in patients with severe congenital neutropenia (SCN). In the past decade, recombinant human granulocyte colony-stimulating factor (rh G-CSF) has prolonged the survival of patients with SCN increasingly reported to have leukemias. In this communication acute myelogenous leukemia (AML) associated with a mutation of the G-CSF receptor (G-CSF-R) developed in a patient with SCN maintained on long-term G-CSF therapy. The blast count in the blood and bone marrow fell to undetectable levels twice on withholding G-CSF and without chemotherapy administration, but the mutant G-CSF-R was detectable during this period. The patient subsequently underwent successful allogeneic bone marrow transplantation. After transplantation, the patient's neutrophil elastase (ELA-2) mutation and G-CSF-R mutation became undetectable by polymerase chain reaction. This report provides novel insights on leukemia developing in congenital neutropenia.

11q23 abnormalities in patients with acute myelogenous leukemia and myelodysplastic syndrome as detected by molecular and cytogenetic analyses

11q23 chromosomal abnormalities and rearrangement of the mixed lineage leukemia (MLL) gene are important prognostic factors in acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS). However, the presence of 11q23 abnormalities does not always correlate with that of MLL gene rearrangement. We retrospectively compared the occurrence of 11q23 abnormalities (measured by karyotyping) and MLL gene rearrangement (measured by Southern blotting) in bone marrow from 311 consecutive adult patients with AML or MDS. 11q23 abnormalities were found in 18 patients (5.8%), of whom 7 (39%) did not have the MLL gene rearrangement. MLL gene rearrangement was detected in 35 patients (11.2%). Of these 35 patients, only 11 (31%) had cytogenetic evidence of 11q23 abnormalities. None of the 21 patients with chronic myelomonocytic leukemia had 11q23 abnormalities or MLL gene rearrangement. 11q23 abnormalities were associated with shorter survival than was a diploid karyotype. Both cytogenetic and molecular studies should be performed to detect 11q23 abnormalities in patients with AML or MDS.

The prognostic significance of p16(INK4a)/p14(ARF) locus deletion and MDM-2 protein expression in adult acute myelogenous leukemia

BACKGROUND

The p16(INK4a) locus encodes two distinct proteins, p16(INK4a) and p14(ARF). Although p16(INK4a) and p15(INK4b) are involved in the phosphorylation of the retinoblastoma (Rb) protein, p14(ARF) interacts with the MDM-2 oncoprotein antagonizing its function as a suppressor of p53. The role of deletions of p16(INK4a)/p14(ARF) and p15(INK4b) and expressions of MDM-2 in myeloid leukemias and its influence on prognosis remain unclear.

METHODS

The authors analyzed deletions of p16(INK4)/p14(ARF) and p15(INK4b) in 74 adults with acute myeloid leukemia (AML) by Southern blotting. Western blotting was used to determine Rb protein phosphorylation in patients with deletions of p16(INK4)/p14(ARF) and p15(INK4b). Then, they analyzed the levels of MDM-2 protein expression and correlated it with prognosis in an expanded population of 79 adults with AML by immunoblot analysis and solid-phase radioimmunoassay.

RESULTS

Deletions of p16(INK4a)/p14(ARF) and/or p15(INK4b) occurred in 4 of 74 patients (5%) (hemizygous in 3, homozygous in 1 patient). Although the complete remission (CR) rate was similar (79% vs. 50%; P = 0.187), CR duration (10 vs. 46 weeks; P < 0.001), event free survival rate (EFS; 6 vs. 85 weeks; P < 0.004) and overall survival rate (11 vs. 86 weeks; P = 0.001) were significantly shorter in patients with deletions of p16(INK4a)/p14(ARF) and/or p15(INK4b). Thirty-seven (47%) of 79 patients studied for MDM-2 showed increased MDM-2 expression. These patients had a significantly shorter EFS rate (50 vs. 64 weeks; P = 0.023) and a trend for shorter CR duration (24 vs. 53 weeks; P = 0.07). Overall survival rate was not significantly different (50 vs. 84 weeks; P = 0.136).

CONCLUSIONS

The authors concluded that 1) deletions of p16(INK4a)/p14(ARF) and/or p15(INK4b) occur with low incidence in patients with AML; 2) patients with deletions of p16(INK4a)/p14(ARF) and/or p15(INK4b) have a significantly shorter CR duration, EFS rate, and overall survival rate than do patients without deletions; (3) overexpression of MDM-2 is common in AML and is associated with shorter CR duration and EFS rate. Mechanisms other than p14(ARF) deletion are responsible for MDM-2 overexpression, and this overexpression may play a role in the biology of the disease.

Angiogenesis in acute and chronic leukemias and myelodysplastic syndromes

Angiogenesis has been associated with the growth, dissemination, and metastasis of solid tumors. The aims of this study were to evaluate the vascularity and the levels of angiogenic factors in patients with acute and chronic leukemias and myelodysplastic syndromes (MDS). The numbers of blood vessels were measured in 145 bone marrow biopsies and the levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), tumor necrosis growth factor-alpha (TNF-alpha), tumor growth factor-alpha (TGF-alpha), and hepatocyte growth factor (HGF) were determined in 417 plasma samples. Except for chronic lymphocytic leukemia (CLL), vascularity was significantly higher in all leukemias and MDS compared with control bone marrows. The highest number of blood vessels and largest vascular area were found in chronic myeloid leukemia (CML). VEGF, bFGF, and HGF plasma levels were significantly increased in acute myeloid leukemia (AML), CML, CLL, chronic myelomonocytic leukemia (CMML), and MDS. HGF, TNF-alpha, and bFGF but not VEGF were significantly increased in acute lymphoblastic leukemia (ALL). TNF-alpha levels were significantly increased in all diseases except for AML and MDS. No significant increase was found in TGF-alpha in any leukemia or MDS. The highest plasma levels of VEGF were in CML, and the highest plasma levels of bFGF were in CLL. The levels of HGF were highest in CMML. These data suggest that vascularity and angiogenic factors are increased in leukemias and MDS and may play a role in the leukemogenic process.

Acute myeloid leukemia, inversion 16, occurring in a patient with chronic lymphocytic leukemia

The occurrence of acute myeloid leukemia (AML) in patients previously diagnosed with chronic lymphocytic leukemia (CLL) is rare. In most cases, AML develops after treatment of CLL and is thought to be therapy related; unfavorable karyotypes are often evident. Herein, we report a patient with a long-standing history of CLL who developed AML with cytogenetic analysis revealing inversion 16. In keeping with the favorable prognosis of this abnormality, the patient has achieved a complete remission, which has been maintained for 13 months.

Clinical relevance of intracellular vascular endothelial growth factor levels in B-cell chronic lymphocytic leukemia

Strong evidence exists for an association between high vascular endothelial growth factor (VEGF) levels and poor prognoses in patients with solid tumors and acute leukemia. Using Western blot analysis and solid-phase radioimmunoassay, we measured cellular VEGF levels in B-cell chronic lymphocytic leukemia (CLL) samples from 225 patients and correlated these levels with disease characteristics and prognoses. The median VEGF level in CLL samples was 7.26 times the median level detected in normal peripheral blood mononuclear cells. Patients with lower levels of VEGF protein showed a trend toward shorter survival (P =.07). However, in a subgroup of CLL patients with good prognoses or early-stage disease (Rai stages 0-II, Binet stages A,B; beta2-M </= 2.8 mg/dL), lower levels of VEGF were associated with shorter survival times. For the entire group of patients, no correlation was found between VEGF levels and beta2-M levels or Rai and Binet stage. Most samples from patients with CLL expressed the 43-kd VEGF isoform in addition to the commonly expressed 45-kd isoform. It remains to be seen whether the expression of the 43-kd isoform is responsible for this reversed correlation with outcome. (Blood. 2000;96:768-770)

Immunohistochemistry can be used to subtype acute myeloid leukemia in routinely processed bone marrow biopsy specimens. Comparison with flow cytometry

Flow cytometry (FC) is the preferred method of immunophenotyping acute myeloid leukemia (AML). However, there are situations in which FC is unavailable and in which immunohistologic staining of bone marrow biopsy specimens can be used to provide immunophenotypic information. To evaluate immunohistologic staining and to confirm its value, we selected 80 newly diagnosed cases of AML that were classified according to French-American-British (FAB) criteria and confirmed by flow cytometric analysis for this study. Paraffin-embedded bone marrow specimens were stained using a panel of antibodies that included CD34 (QBEND10), antimyeloperoxidase (anti-MPO), antihemoglobin, factor VIII-related antigen, and 3 epitopes of CD68 (HAM56, KP1, and PG-M1). Our findings suggest that with the use of the paraffin-reactive antibodies CD34 (QBEND10), MPO, CD68 (PG-M1), antihemoglobin, and factor VIII-related antigen, immunohistochemistry can be used to subclassify AML. Comparison of immunohistochemical results with FC immunophenotyping suggests that there is significant concordance in the results for markers that can be used with both techniques, indicating that the sensitivity and specificity of both methods is comparable (P > .53 in all cases).

Progressive multifocal leukoencephalopathy with concurrent Richter's syndrome

Progressive multifocal leukoencephalopathy (PML) is a demyelinating infectious disease caused by the JC virus. It was originally described in patients with chronic lymphocytic leukemia (CLL). Richter's syndrome, or transformation to large cell Lymphoma, occurs in approximately 3% of patients with CLL, and carries a poor prognosis. We report a patient with documented PML and concurrent Richter's transformation outside the central nervous system. Before establishing a definitive diagnosis of PML, radiation therapy to the presumed lymphomatous brain lesion had been considered, raising the issue of whether stereotactic brain biopsy should be considered in every patient in a similar situation. Although this is likely a rare occurrence, patients with Richter's transformation documented at an extra-neural site and a brain lesion may benefit from the establishment of an infectious diagnosis which would influence therapy.

Variations in the low levels of cyclin D1/BCL1 have prognostic value in chronic lymphocytic leukemia

Cyclin D1 (CyD1)/BCL1 (PRAD1) is expressed at high levels in almost all cases of mantle cell leukemia/lymphoma (MCL) and in rare cases of chronic lymphocytic leukemia (CLL). The CyD1/BCL1 protein plays an important role in the progression of cells through the G1 phase of cell cycle. Most of the CyD1/BCL1 protein expression studies are performed using immunohistochemistry. We used a sensitive solid-phase radioimmunoassay (RIA) to quantify CyD1 protein expression in 199 patients with CLL. Of these 137 patients were previously untreated with the rest having had standard chemotherapeutic regimens including alkylating agents and fludarabine before being referred to our center. Median white cell count in these patients was 49x10(3) /microl (range 3.0-438.5x10(3)/microl), hemoglobin level 13.1 g/dl (range 5.2-17.3 g/dl), platelet count 157x10(3) /microl (range 10-377x10(3) /microl), age 58 (range 26-89), and beta2-microglobulin 2.75 mg/dl (range 1.1-14.3). The median radioactivity (CPM) of mononuclear cells obtained from 56 normal individuals was assigned a value of 1. There was no significant variation in CyD1 levels among normal individuals (SD=0. 12). While most CyD1 levels in MCL varied from 6.5 to 15.6, the median CyD1/BCL1 in CLL was 1.4 with 75th percentile under 2.12. Rare CLL cases (3.5%) showed levels between 4 and 8.83. When divided into two groups at the median level, patients with higher CyD1/BCL1 expression had shorter survival (P = 0.03). This remained true when applied only to the previously untreated patients (P=0.05). Despite the relatively low expression, the CyD1/BCL1 levels in univariate analysis were as good or better predictors of survival than Binet (P = 0.03) or Rai (P = 0.05) staging. Furthermore, CyD1/BCL1 levels correlated with serum beta2-microglobulin (P = 0.001), white blood cell count (P = 0.004) and hemoglobin levels at the time of collection (P = 0.0003) but not with lymphocyte count, platelet count or age. The data demonstrate that CyD1/BCL1 is likely to play a significant role in the biology of CLL and can be used as a prognostic indicator. Further studies to clarify the role of CyD1 in the biology of CLL and its value as a prognostic indicator at the time of diagnosis are encouraged.

Terminal deoxynucleotidyl transferase expression in acute myelogenous leukemia and myelodysplasia as determined by flow cytometry

The significance of terminal deoxynucleotidyl transferase (TdT) expression in acute myelogenous leukemia (AML) remains controversial. Therefore, we studied TdT expression by flow cytometry in 120 previously untreated patients with AML or myelodysplastic syndrome (MDS) to determine the distribution of TdT-positive blasts and the intensity of TdT expression and to seek clinically significant associations. TdT expression measured by flow cytometry (flow TdT%) was heterogeneous, ranging from 0.1% to 87% (median, 8.5%), and 74 patients (62%) had at least 5% TdT-positive blasts. TdT positivity was associated with the M0 or M1 subtype and with expression of CD34 and CD7. No significant correlation was found between TdT expression and type of cytogenetic abnormality or rearrangement of immunoglobulin or T-cell receptor genes. Remission lasted longer in patients with a flow TdT% < 5 than in patients with a flow TdT% > 5 (median, 95 weeks vs 55 weeks, p = 0.02); however, complete remission rates did not differ when patients were classified by initial flow TdT%. Survival was slightly better for patients with flow TdT% less than 5%. Among patients with a flow TdT% > 5%, those with a higher TdT intensity survived longer than those with a lower intensity. These data suggest that quantitative TdT measurement may contribute to prognostic estimate in AML patients.

Deletions in the 13q14 locus in adult lymphoblastic leukemia: rate of incidence and relevance

BACKGROUND

A putative tumor suppressor gene involved in chronic lymphocytic leukemia (CLL) has been localized to the 13q14 locus. Microsatellite analysis was used to test whether this locus also is involved in acute lymphoblastic leukemia (ALL) and its prognostic relevance determined.

METHODS

The authors analyzed 49 patients with adult ALL for deletions at the 13q14 locus using a battery of 6 microsatellite markers corresponding to this region (D13S260, STR257, D13S263, D13S153, D13S319, and AFMa301wb5).

RESULTS

Five of the 49 adult ALL patients analyzed (10%) showed loss of heterozygosity (LOH) or deletions at 13q14. Similar to CLL, the significant minimal deletions appeared to be localized between D13S260 and AFMa301wb5 and did not involve the retinoblastoma or BRCA2 genes. Among newly diagnosed patients, LOH was associated with shorter survival (P = 0.007).

CONCLUSIONS

These data suggest that the 13q14 gene, commonly deleted in CLL patients, also is deleted in some patients with adult ALL. Although the number of the cases in the current study is small, 13q deletions in ALL patients may play a role in the clinical behavior of this disease.

ATM gene deletion in patients with adult acute lymphoblastic leukemia

BACKGROUND

Loss of heterozygosity (LOH) at the ATM gene (mutated in ataxia telangiectasia [AT] patients) and ATM protein deficiency occur in 14% and 34%, respectively, of patients with chronic lymphocytic leukemia (CLL). ATM protein deficiency also is associated with aggressive disease and worse patient survival. Considering the aberrations in the ATM gene in CLL and the high rate of incidence of lymphoid neoplasias in AT patients, the authors investigated its incidence rate and significance in patients with adult acute lymphoblastic leukemia (ALL).

METHODS

Samples from 36 adults with ALL were analyzed for LOH and homozygous deletion (HD) using a panel of three microsatellite markers located at the ATM gene (D11S2179), the MLL gene (D11S1356), and the BCL1 gene (D11S987) loci. These markers are located within the 11q13-q23 locus.

RESULTS

Of the 36 informative cases, 10 (28%) showed deletions (7 LOH and 3 HDs) at the D11S2179 marker. In two patients, the deletions were extended to the MLL gene locus. These deletions were submicroscopic because only 3% (1 of 36) of patients showed abnormalities involving 11q23 using cytogenetic studies. The authors also estimated the levels of ATM protein in 15 ALL patients and 12 healthy volunteers by radioimmunoassay. The ATM protein levels in cases with LOH at the ATM gene were between 15-50% of those from normal bone marrow. In contrast to CLL patients, patients with LOH or HD at the ATM gene locus showed better survival compared with patients without ATM gene deletions (P = 0.003).

CONCLUSIONS

LOH of the ATM gene and protein deficiency are common in adult ALL, are not demonstrated at the cytogenetic level, and are associated with a favorable prognosis. The authors speculate that ATM deficiency may increase the sensitivity of leukemic blasts to the chemotherapy used during induction and after disease remission in patients with adult ALL. The relatively high frequency of deletion of the D11S2179 marker compared with the D11S1356 marker suggests that ATM is the target gene of the deletion at the 11q23 locus, and that such deletions may play a role in the pathogenesis of ALL.

Downregulation of the p53 tumor suppressor gene and upregulation of the bcl-2 gene in retinoic acid receptor alpha-deficient transgenic mice

We recently demonstrated lymphoma development in transgenic mice deficient in retinoic acid receptor alpha (RARalpha). High incidence of lymphoma development in this transgenic mouse model system was similar to lymphoma development in p53 knockout mice. In an effort to understand the molecular basis of lymphomagenesis in RARalpha-deficient transgenic mice, we compared the levels of RARalpha to the levels of p53 mRNA, and Bcl-2, and Bax proteins in lymphoid and non-lymphoid tissues and in lymphomas derived from the RARalpha-deficient transgenic mice. The p53 mRNA levels were depleted in various tissues including spleen ( approximately 96%), thymus ( approximately 29%) and bone marrow ( approximately 62%) of RARalpha-deficient transgenic mice when compared with the normal littermates, and the reduction in p53 mRNA expression in the various tissues examined was proportional to the reduction in RARalpha expression. Bcl-2 to Bax ratios were highly increased in the lymphoid compartments (spleen >bone marrow >thymus) because of selective overexpression of Bcl-2 protein. In summary, RARalpha downmodulation in this transgenic mouse model system was accompanied by p53 downmodulation and deregulation of Bcl-2 to Bax ratios in the lymphoid compartments.

Expression of thrombopoietin and its receptor (c-mpl) in chronic myelogenous leukemia: correlation with disease progression and response to therapy

BACKGROUND

Chronic myelogenous leukemia (CML) represents a paradigm of the stepwise increment in disease aggressiveness, resistance to therapy, and transformation. Thrombopoietin (TPO) and its receptor, c-mpl, support the proliferation of multiple types of immature hematopoietic progenitor cells, and induce clonal growth of leukemic cells. The authors investigated whether TPO or c-mpl overexpression might correlate with progression of CML, disease aggressiveness, or response to therapy.

METHODS

Expression of c-mpl and TPO was measured in bone marrow samples from 208 patients with CML by Western blot analysis and solid-phase plate radioimmunoassay (used for quantification). Samples obtained from individuals without evidence of hematologic abnormalities were used as controls.

RESULTS

There were no significant differences in TPO or c-mpl expression among patients in different phases of CML or between patients with Philadelphia chromosome positive and negative CML. When TPO and c-mpl levels were analyzed in relation to prognostically important host and disease characteristics in early chronic phase CML, platelet and white blood cell counts demonstrated significant differences in both TPO and c-mpl expression, but age and spleen size demonstrated significant differences in TPO expression only. Responses to interferon (INF)-alpha-based therapy and survival were not influenced by TPO or c-mpl levels.

CONCLUSIONS

TPO or c-mpl overexpression did not correlate with different CML phases, suggesting that they were not involved in CML progression from early to advanced phase. Neither TPO nor c-mpl overexpression was particularly evident in any risk group, suggesting lack of correlation between their expression and disease aggressiveness. This was supported by the finding of similar response to IFN-alpha-based therapy and survival regardless of the level of TPO or c-mpl expression.