Loss of H3K27 methylation identifies poor outcomes in adult-onset acute leukemia

Background

Acute leukemia is an epigenetically heterogeneous disease. The intensity of treatment is currently guided by cytogenetic and molecular genetic risk classifications; however these incompletely predict outcomes, requiring additional information for more accurate outcome predictions. We aimed to identify potential prognostic implications of epigenetic modification of histone proteins, with a focus on H3K4 and H3K27 methylation marks in relation to mutations in chromatin, splicing and transcriptional regulators in adult-onset acute lymphoblastic and myeloid leukemia.

Results

Histone 3 lysine 4 di- and trimethylation (H3K4me2, H3K4me3) and lysine 27 trimethylation (H3K27me3) mark expression was evaluated in 241 acute myeloid leukemia (AML), 114 B-cell acute lymphoblastic leukemia (B-ALL) and 14T-cell ALL (T-ALL) patient samples at time of diagnosis using reverse phase protein array. Expression levels of the marks were significantly lower in AML than in B and T-ALL in both bone marrow and peripheral blood, as well as compared to normal CD34+ cells. In AML, greater loss of H3K27me3 was associated with increased proliferative potential and shorter overall survival in the whole patient population, as well as in subsets with DNA methylation mutations. To study the prognostic impact of H3K27me3 in the context of cytogenetic aberrations and mutations, multivariate analysis was performed and identified lower H3K27me3 level as an independent unfavorable prognostic factor in all, as well as in TP53 mutated patients. AML with decreased H3K27me3 demonstrated an upregulated anti-apoptotic phenotype. In ALL, the relative quantity of histone methylation expression correlated with response to tyrosine kinase inhibitor in patients who carried the Philadelphia cytogenetic aberration and prior smoking behavior.

Conclusion

This study shows that proteomic profiling of epigenetic modifications has clinical implications in acute leukemia and supports the idea that epigenetic patterns contribute to a more accurate picture of the leukemic state that complements cytogenetic and molecular genetic subgrouping. A combination of these variables may offer more accurate outcome prediction and we suggest that histone methylation mark measurement at time of diagnosis might be a suitable method to improve patient outcome prediction and subsequent treatment intensity stratification in selected subgroups.

A quantitative analysis of heterogeneities and hallmarks in acute myelogenous leukaemia

Acute myelogenous leukaemia (AML) is associated with risk factors that are largely unknown and with a heterogeneous response to treatment. Here, we provide a comprehensive quantitative understanding of AML proteomic heterogeneities and hallmarks by using the AML proteome atlas, a proteomics database that we have newly derived from MetaGalaxy analyses, for the proteomic profiling of 205 AML patients and 111 leukaemia cell lines. The analysis of the dataset revealed 154 functional patterns based on common molecular pathways, 11 constellations of correlated functional patterns, and 13 signatures that stratify the patients’ outcomes. We find limited overlap between proteomics data and both cytogenetics and genetic mutations, and also that leukaemia cell lines show limited proteomic similarities with cells from AML patients, suggesting that a deeper focus on patient-derived samples is needed to gain disease-relevant insights. The AML proteome atlas provides a knowledge base for proteomic patterns in AML, a guide to leukaemia cell-line selection, and a broadly applicable computational approach for quantifying the heterogeneities of protein expression and proteomic hallmarks in AML.

Comprehensive mutational analysis of primary and relapse acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a subtype of myeloid leukemia characterized by differentiation block at the promyelocyte stage. Besides the presence of chromosomal rearrangement t(15;17), leading to the formation of PML-RARA (promyelocytic leukemia-retinoic acid receptor alpha) fusion, other genetic alterations have also been implicated in APL. Here, we performed comprehensive mutational analysis of primary and relapse APL to identify somatic alterations, which cooperate with PML-RARA in the pathogenesis of APL. We explored the mutational landscape using whole-exome (n=12) and subsequent targeted sequencing of 398 genes in 153 primary and 69 relapse APL. Both primary and relapse APL harbored an average of eight non-silent somatic mutations per exome. We observed recurrent alterations of FLT3, WT1, NRAS and KRAS in the newly diagnosed APL, whereas mutations in other genes commonly mutated in myeloid leukemia were rarely detected. The molecular signature of APL relapse was characterized by emergence of frequent mutations in PML and RARA genes. Our sequencing data also demonstrates incidence of loss-of-function mutations in previously unidentified genes, ARID1B and ARID1A, both of which encode for key components of the SWI/SNF complex. We show that knockdown of ARID1B in APL cell line, NB4, results in large-scale activation of gene expression and reduced in vitro differentiation potential.

EphB1 Suppression in Acute Myelogenous Leukemia: Regulating the DNA Damage Control System

Loss of ephrin receptor (EphB1) expression may associate with aggressive cancer phenotypes; however, the mechanism of action remains unclear. To gain detailed insight into EphB1 function in acute myelogenous leukemia (AML), comprehensive analysis of EphB1 transcriptional regulation was conducted. In AML cells, EphB1 transcript was inversely correlated with EphB1 promoter methylation. The presence of EphB1 allowed EfnB1 ligand-mediated p53 DNA binding, leading to restoration of the DNA damage response (DDR) cascade by the activation of ATR, Chk1, p53, p21, p38, CDK1(tyr15), and Bax, and downregulation of HSP27 and Bcl2. Comparatively, reintroduction of EphB1 expression in EphB1-methylated AML cells enhanced the same cascade of ATR, Chk1, p21, and CDK1(tyr15), which consequently enforced programmed cell death. Interestingly, in pediatric AML samples, EphB1 peptide phosphorylation and mRNA expression were actively suppressed as compared with normal bone marrow, and a significant percentage of the primary AML specimens had EphB1 promoter hypermethylation. Finally, EphB1 repression associated with a poor overall survival in pediatric AML. Combined, the contribution of EphB1 to the DDR system reveals a tumor-suppressor function for EphB1 in pediatric AML.

IMPLICATIONS

The tumor-suppressor function of EphB1 is clinically relevant across many malignancies, suggesting that EphB1 is an important regulator of common cancer cell transforming pathways.

Apoptosis repressor with caspase recruitment domain is regulated by MAPK/PI3K and confers drug resistance and survival advantage to AML

The apoptosis repressor with caspase recruitment domain (ARC) protein is known to suppress both intrinsic and extrinsic apoptosis. We previously reported that ARC expression is a strong, independent adverse prognostic factor in acute myeloid leukemia (AML). Here, we investigated the regulation and role of ARC in AML. ARC expression is upregulated in AML cells co-cultured with bone marrow-derived mesenchymal stromal cells (MSCs) and suppressed by inhibition of MAPK and PI3K signaling. AML patient samples with RAS mutations (N = 64) expressed significantly higher levels of ARC than samples without RAS mutations (N = 371) (P = 0.016). ARC overexpression protected and ARC knockdown sensitized AML cells to cytarabine and to agents that selectively induce intrinsic (ABT-737) or extrinsic (TNF-related apoptosis inducing ligand) apoptosis. NOD-SCID mice harboring ARC-overexpressing KG-1 cells had significantly shorter survival than mice injected with control cells (median 84 vs 111 days) and significantly fewer leukemia cells were present when NOD/SCID IL2Rγ null mice were injected with ARC knockdown as compared to control Molm13 cells (P = 0.005 and 0.03 at 2 and 3 weeks, respectively). Together, these findings demonstrate that MSCs regulate ARC in AML through activation of MAPK and PI3K signaling pathways. ARC confers drug resistance and survival advantage to AML in vitro and in vivo, suggesting ARC as a novel target in AML therapy.

Accurate detection of uniparental disomy and microdeletions by SNP array analysis in myelodysplastic syndromes with normal cytogenetics

Progress in the management of patients with myelodysplastic syndromes (MDS) has been hampered by the inability to detect cytogenetic abnormalities in 40-60% of cases. We prospectively analyzed matched pairs of bone marrow and buccal cell (normal) DNA samples from 51 MDS patients by single nucleotide polymorphism (SNP) arrays, and identified somatically acquired clonal genomic abnormalities in 21 patients (41%). Among the 33 patients with normal bone marrow cell karyotypes, five (15%) had clonal, somatically acquired aberrations by SNP array analysis, including four with segmental uniparental disomies (UPD) and one with three separate microdeletions. Each abnormality was detected more readily in CD34+ cells then in unselected bone marrow cells. Paired analysis of bone marrow and buccal cell DNA from each patient was necessary to distinguish true clonal genomic abnormalities from inherited copy number variations and regions with apparent LOH. UPDs affecting chromosome 7q were identified in two patients who had a rapidly deteriorating clinical course despite a low-risk International Prognostic Scoring System score (IPSS). Further studies of larger numbers of patients will be needed to determine whether 7q UPD detected by SNP array analysis will identify higher-risk MDS patients at diagnosis, analogous to those with 7q cytogenetic abnormalities.

Risk factors associated with late cytomegalovirus reactivation after allogeneic stem cell transplantation for hematological malignancies

We analyzed the clinical factors associated with late cytomegalovirus (CMV) reactivation in a group of 269 consecutive recipients of allogeneic stem cell transplant (SCT) for hematological malignancies. Eighty-four subjects (31%) experienced late CMV reactivation, including 64 with prior early reactivation and 20 with isolated late reactivation. Multivariate analyses were conducted in patients with early CMV reactivation to identify factors associated with late recurrence. Important risk factors included lymphoid diagnosis, occurrence of graft-versus-host disease (GVHD), greater number of episodes of early reactivation, persistent day 100 lymphopenia and the use of a CMV-seronegative donor graft. We combined these risk factors in a predictive model to identify those at relatively low, intermediate and high risk. The low-risk group (15% cumulative incidence, CI) encompassed patients without early CMV reactivation, and subjects transplanted for a myeloid malignancy from a matched-related (MR) donor without subsequent acute GVHD. The high-risk patients (73% CI) met all of the following criteria: (1) received an MR graft but developed GVHD, or received a non-MR graft irrespective of GVHD; (2) had more than two episodes of early reactivation; and (3) received a CMV-seronegative graft and/or remained persistently lymphopenic at day 100 after SCT. The remaining patients had an intermediate incidence of 32%.

A phase 1 trial of a novel organic arsenic S-dimethylarsino-glutathione (ZIO-101) in hematological malignancies

16503

Background: Inorganic Arsenicals (IA, e.g. AS2O3) kill many human leukemia cell lines and have efficacy in APL. Evaluation of efficacy against other types of leukemia is limited by the substantial toxicity of IA. Organic Arsenicals (OA) are less toxic than IA. ZIO-101 (S-dimethylarsino-glutathione) is an OA with activity against diverse cancers in in vitro tests and animals mediated through mitochondrial damage and apoptosis induction. ZIO-101 may induce apoptosis by different mechanisms than As2O3 and can kill As2O3-resistant cancer cells. Compared to As2O3, the LD50 of ZIO-101 in mice is 50X higher and at equimolar extracellular arsenic concentrations ZIO-101 produces 15× higher intracellular arsenic concentration. These features make ZIO-101 attractive for evaluation in leukemia. Methods: A phase-1 study evaluating the safety and pharmacokinetic (PK) profile of ZIO-101 in subjects with advanced hematological malignancies is underway. 8 patients (PATS) with acute myelogenous leukemia (AML) (median 3 prior treatments) received ZIO-101 at doses of 78, 109 or 153 (n = 4, 3, 1) mg/m2/d IV for 5 d every mo. Results: Therapy with ZIO-101 has been safe and well-tolerated. Toxicities ≥ grade-2 included hyperglycemia (N = 3) and decreased albumin (N = 3) and Ca (N = 3) and 1 subject each had ≥ grade 2 elevations in LFT, or decreases in K, or PO4, febrile neutropenia and rash. Preexisting anemia and thrombocytopenia increased by 1 grade in 4 and 3 PATS each. Grade ≥3 neutropenia occurred in 2 PATS. No significant renal, liver or heart toxicity occurred, 1 patient with prior 10AV block had transient prolongation of QT interval non-recurring on rechallenge. PK studies at 109 mg/m2/d showed a tmax = 1.5 h (SD ± 0.7 h), Cmax = 402 ng/mL (±33 ng/mL), t1/2 = 14.4 h (±2.9 h) and AUC0-∞ = 8.93 μg · min/mL (±1.82 μgzmdmin/mL). 4 PATS progressed after 1 cycle, 3 had stable disease and received a 2nd cycle: 1 progressed and 2 remain on study. 1 patient is too early to evaluate. Blood myeloblasts decreased (9 to 1.1 × 10e9/L at day 13) in 1 subject and completely resolved in 2 (pre-therapy: 100 and 336 × 10e9/L). Bone marrow myeloblasts were unchanged. Conclusions: Administration of ZIO-101 to PATS with advanced AML was safe and dose-escalation continues and a modest antileukemic effect has been observed.

[Table: see text]

Comparative analysis of the effects of sample source and test methodology on the assessment of protein expression in acute myelogenous leukemia

Numerous studies have analyzed the expression and prognostic importance of various proteins in acute myelogenous leukemia (AML). We sought to determine whether the sample source and methodology used to measure protein expression affect the results obtained. To determine the importance of sample source, we used Western blotting to compare the expression of eight proteins and phosphoproteins in the leukemia blast-enriched fraction of 118 blood- and 108 marrow-derived samples, including 37 paired samples. To determine the importance of methodology, the expression of five proteins was measured in 20 paired samples by Western blotting, laser scanning cytometry (LSC), and flow cytometry. The mean expression and range of expression in blood- and marrow-derived samples were statistically identical for all eight proteins. Expression measurements for the 37 paired blood and marrow samples also had very high statistical correlation. The LSC and flow cytometry data had the highest concordance when compared using Kolmogorov-Smirnoff D-stats (range of R values, 0.8-1.0). High concordance was also observed between the LSC and flow cytometry results when the percentage of cells positive for expression was dichotomized into positive or negative expression. However, there was less correlation between LSC and flow cytometry when the actual percentages of positive cells were compared. The majority of discordant situations involved samples that were positive by flow cytometry but negative by LSC. The correlation between Western blotting signal intensity and the percentage of expression-positive cells measured by LSC or flow cytometry varied by protein but was limited when there was little heterogeneity in expression by either method. In conclusion, provided that leukemia blast-enriched fractions were analyzed, the blood- and marrow-derived samples had identical protein expression. There was good concordance of results between flow cytometry and LSC, which share similar technology, but more limited correlation between these methods and Western blotting.

Beyond single pathway inhibition: MEK inhibitors as a platform for the development of pharmacological combinations with synergistic anti-leukemic effects

The MEK/MAPK signaling module is a key integration point along signal transduction cascades that regulate cell growth, survival, and differentiation, and is aberrantly activated in many human tumors. In tumor cells, constitutive MAPK activation affords increased proliferation and resistance to apoptotic stimuli, including classical cytotoxic drugs. In most instances, however, MAPK inhibition has cytostatic rather than cytotoxic effects, which may explain the lack of objective responses observed in early clinical trials of MEK inhibitors. Nevertheless, amenability of the MAPK pathway to pharmacodynamic evaluation and negligible clinical toxicity make MEK inhibitors an ideal platform to build pharmacological combinations with synergistic antitumor activity. In AML, the MEK/MAPK pathway is constitutively activated in the majority of cases (75%), conferring a uniformly poor prognosis; in preclinical models of AML, MEK blockade profoundly inhibits cell growth and proliferation and downregulates the expression of several anti-apoptotic players, thereby lowering the apoptotic threshold. Apoptosis induction, however, requires concentrations of MEK inhibitors much higher than those required to inhibit proliferation. Nevertheless, MEK blockade efficiently and selectively sensitizes leukemic cells to sub-optimal doses of other apoptotic stimuli, including classical cytotoxics (nucleoside analogs, microtubule-targeted drugs, gamma-irradiation), biologicals (retinoids, interferons, arsenic trioxide), and, most interestingly, other signal transduction/apoptosis modulators (UCN-01, STI571, Bcl-2 antagonists). In most instances, these MEK inhibition-based combinations result in a striking pro-apoptotic synergism in preclinical models. Here we briefly discuss evidence suggesting that MAPK pathway inhibition could play a prominent role in the development of integrated therapeutic strategies aimed at synergistic anti-leukemic effects.

Regulation of Bcl2 phosphorylation and potential significance for leukemic cell chemoresistance

Although considered tightly linked, the linkage effectors for proliferation and antiapoptotic signaling pathways are not clear. Phosphorylation of Bcl2 at serine 70 is required for suppression of apoptosis in interleukin 3 (IL-3)-dependent myeloid cells deprived of IL-3 or treated with antileukemic drugs and can result from agonist activation of mitochondrial protein kinase C alpha (PKCalpha). However, we have recently found that high concentrations of staurosporine up to 1 microM: can only partially inhibit IL-3-stimulated Bcl2 phosphorylation but completely block PKCalpha-mediated Bcl2 phosphorylation in vitro, indicating the existence of a non-PKC, staurosporine-resistant Bcl2 kinase (SRK). Although the RAF-1MEK-1-mitogen-activated protein kinase (MAPK) cascade is required for factor-dependent mitogenic signaling, a direct role in antiapoptosis signaling is not clear. In particular, the role of phosphorylation in the regulation of death substrates is not yet clear. Our findings indicate a potential role for the MEK/MAPK pathway in addition to PKC in antiapoptosis signaling, involving Bcl2 phosphorylation that features a role for extracellular signal-regulated kinase (ERK)1 and 2 as SRKs. These findings indicate a novel role for ERK1 and 2 as molecular links between proliferative and survival signaling and may, at least in part, explain the apparent paradox by which Bcl2 may suppress staurosporine-induced apoptosis. Although the effect of phosphorylation on Bcl2 function is not clear, effector molecules that regulate Bcl2 phosphorylation may have clinical significance in patients with acute myelogenous leukemia (AML) who express detectable levels of Bcl2. Preliminary findings suggest that expression of PKCalpha, ERK2, and Bax in leukemic blast cells from patients with AML, although individually not prognostic, appears to have potential clinical value in predicting chemoresistance and survival outcomes.

Therapeutic targeting of the MEK/MAPK signal transduction module in acute myeloid leukemia

The mitogen-activated protein kinase (MAPK) pathway regulates growth and survival of many cell types, and its constitutive activation has been implicated in the pathogenesis of a variety of malignancies. In this study we demonstrate that small-molecule MEK inhibitors (PD98059 and PD184352) profoundly impair cell growth and survival of acute myeloid leukemia (AML) cell lines and primary samples with constitutive MAPK activation. These agents abrogate the clonogenicity of leukemic cells but have minimal effects on normal hematopoietic progenitors. MEK blockade also results in sensitization to spontaneous and drug-induced apoptosis. At a molecular level, these effects correlate with modulation of the expression of cyclin-dependent kinase inhibitors (p27(Kip1) and p21(Waf1/CIP1)) and antiapoptotic proteins of the inhibitor of apoptosis proteins (IAP) and Bcl-2 families. Interruption of constitutive MEK/MAPK signaling therefore represents a promising therapeutic strategy in AML.

Mylotarg (gemtuzumab ozogamicin) therapy is associated with hepatic venoocclusive disease in patients who have not received stem cell transplantation

BACKGROUND

Mylotarg (Wyeth-Ayerst Laboratories, St. Davids, PA) is the brand name for a calicheamicin-conjugated humanized anti-CD33 monoclonal antibody (gemtuzumab ozogamicin, CMA-676) and has been approved recently for the treatment of a subset of elderly patients who have relapsed acute myeloid leukemia (AML). Mylotarg is associated with an incidence of approximately 20% Grade 3 or 4 hyperbilirubinemia and liver transaminitis in this patient population. Hepatic venoocclusive disease (VOD) has been reported in patients who have undergone stem cell transplantation (SCT) after Mylotarg therapy. Outside of the SCT setting, VOD has been associated very rarely with cytotoxic therapy.

METHODS

The authors assessed the incidence of VOD in 119 patients who were receiving Mylotarg-containing non-SCT regimens. VOD was diagnosed through the use of standard Seattle and Baltimore criteria.

RESULTS

A cohort of 119 (61 previously untreated, 58 with relapsed disease) patients with AML (92 patients), advanced myelodysplastic syndrome (25 patients), or chronic myeloid leukemia in blast phase (2 patients), received Mylotarg-based regimens. Fourteen (12%) developed VOD. The diagnosis of VOD was supported by histology in 2 patients and radiologic studies in a further 10 patients. Five (36%) of 14 patients with VOD had received no prior antileukemic cytotoxic therapy, including 2 patients who received single-agent Mylotarg therapy.

CONCLUSIONS

Mylotarg was shown to be associated with the development of potentially fatal VOD in patients with leukemia who had not received SCT. VOD occurred when Mylotarg was used either as a single agent or when it was given with other cytotoxic agents. VOD occurred in Mylotarg-treated patients who had received no prior cytotoxic therapy. The current study concluded that risk factors for VOD should be assessed when considering Mylotarg therapy, and that attempts to avoid and treat VOD are warranted in patients who receive Mylotarg therapy.

Preemptive control of graft-versus-host disease in a murine allogeneic transplant model using retrovirally transduced murine suicidal lymphocytes

Suicidal lymphocytes could greatly expand the role of allogeneic transplantation by reducing graft-versus-host disease (GVHD) as a barrier to transplantation, but optimization of their use is hindered by the lack of adequate animal models. To develop an animal model that used retrovirally transduced suicidal lymphocytes in a GVHD setting, a well-characterized MHC-matched murine transplant model (B10.BR-->AKR/J) was adapted. B10.BR splenic lymphocytes stimulated with concanavalin A and interleukin 2 were infected with a retrovirus containing the low-affinity nerve growth factor receptor (LNGFR) and the HSV-TK gene and immunomagnetically selected; these LNGFR+/TK+ allogeneic lymphocytes were then cotransplanted with 1 x 10(7) bone marrow cells into lethally irradiated AKR/J recipients. The LNGFR+/TK+ donor lymphocytes persisted in the peripheral circulation for 6 months in both syngeneic and allogeneic settings. Doses of 2 x 10(6) TK+ allogeneic lymphocytes produced GVHD with a severity and time course similar to that induced by naive lymphocytes. Survival of TK+ allogeneic lymphocyte-bearing mice was significantly improved (P = 0.01) when ganciclovir (GCV; 2 mg/day) was administered on days 7-13 post transplant by i.p. injection, demonstrating that GVHD could be prevented. Fluorescence-activated cell sorting analysis demonstrated 4-fold reduction but persistent circulation of LNGFR+ lymphocytes in mice treated with GCV at various time points 1-3 months after transplantation, demonstrating selective killing of GVHD-reactive cells. We conclude that retrovirally transduced LNGFR+/TK+ murine lymphocytes can be produced, persist after transplant, remain alloreactive, and can be killed by GCV administration, resulting in reduced GVHD.

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.

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.

Expression and prognostic significance of IAP-family genes in human cancers and myeloid leukemias

Expression of several inhibitor of apoptosis proteins (IAPs) was investigated in the National Cancer Institute panel of 60 human tumor cell lines, and the expression and prognostic significance of one of these, XIAP, was evaluated in 78 previously untreated patients with acute myelogenous leukemia (AML). XIAP and cIAP1 were expressed in most cancer lines analyzed, with substantial variability in their relative levels. In contrast, NAIP mRNA was not detectable, and cIAP2 was found at the mRNA and protein levels in only 34 (56%) and 5 (8%) of the 60 tumor cell lines analyzed, respectively. Interestingly, XIAP, cIAP1, and cIAP2 mRNA levels did not correlate with protein levels in the tumor lines, indicating posttranscriptional regulation of expression. High levels of XIAP protein in tumor cell lines were unexpectedly correlated with sensitivity to some anticancer drugs, particularly cytarabine and other nucleosides, whereas higher levels of cIAP1 protein levels were associated with resistance to several anticancer drugs. The relevance of XIAP to in vivo responses to cytarabine was explored in AML, making correlations with patient outcome (n = 78). Patients with lower levels of XIAP protein had significantly longer survival (median, 133 versus 52.5 weeks; P = 0.05) and a tendency toward longer remission duration (median, 87 versus 52.5 weeks; P = 0.13) than those with higher levels of XIAP. Altogether, these findings show that IAPs are widely but differentially expressed in human cancers and leukemias and suggest that higher XIAP protein levels may have adverse prognostic significance for patients with AML.

BAX and PKCalpha modulate the prognostic impact of BCL2 expression in acute myelogenous leukemia

Previously, we demonstrated that the level of BCL2 expression is prognostic in acute myelogenous leukemia (AML). High levels of BCL2 correlate with an adverse outcome when associated with favorable and intermediate prognosis cytogenetics (FIPC), whereas low levels portend an adverse outcome when associated with unfavorable cytogenetics (UC). Because BCL2 function can be modulated by dimerization with family members, like BAX, or by phosphorylation by protein kinase C alpha (PKCalpha), we hypothesize that the relative expression of these proteins in primary leukemic cells might alter the prognostic impact of BCL2 expression. We therefore measured BAX and PKCalpha protein levels in peripheral blood mononuclear cell lysates from 165 newly diagnosed AML patients and correlated the expression of these proteins with BCL2 expression, patient survival, and remission induction success. Expression levels of BAX and PKCalpha were normalized against a control cell line, K562. BAX and PKCalpha expression levels were heterogeneous and did not correlate with the percentage of blasts in the sample (R2 = 0.01 and <0.01). The median expression of both was similar across FAB groups but the range was greater for M4. A similar distribution of expression was observed in all cytogenetic groups, except that patients with inversion 16 demonstrated lower levels of BAX. Individually, neither PKCalpha nor BAX expression was prognostic of response to induction therapy or survival. A similar outcome was obtained when patients were stratified by cytogenetics into FIPC and UC groups. However, the ratio of either BCL2:BAX (B2:BX) or PKCalpha*B2:BX (PK*B2:BX) was highly prognostic. Patients with FIPC and a lower ratio (less than median) of either B2:BX or PK*B2:BX had a significantly higher remission induction rate (88 versus 69%, P = 0.04) and longer survival (median: 141 versus 80.5 weeks, P = 0.007) compared with those with ratios more than median. For patients with UC, values of either B2:BX or PK*B2:BX below the median had an inferior response rate to induction therapy (35 versus 78%, P = 0.0006) and inferior survival outcomes (median survival: 11 versus 53 weeks, P = 0.00002). Interestingly, FIPC and UC patients with antiapoptotic ratios (defined as B2:BX or PK*B2:BX more than median) had identical response rates and survival outcomes. In multivariate analyses, the compound variables of cytogenetics and B2:BX, or PK*B2:BX were independent predictors of survival. These results suggest that expression levels of proteins that affect the functional status of BCL2 modify the prognostic impact of BCL2 and suggest that the role of apoptosis in different cases of AML varies independently in the different cytogenetic subgroups.

Caspase 2 and caspase 3 as predictors of complete remission and survival in adults with acute lymphoblastic leukemia

Dysregulation of apoptosis is an important mechanism in leukemogenesis. Caspases are cysteine proteases that play a major role in the activation of apoptotic pathways and chemotherapy-induced cell death. High levels of inactive, uncleaved caspase 2 and caspase 3 have recently been associated with poor survival in patients with acute myelogenous leukemia. We hypothesized a similarly significant role for caspase 2 and caspase 3 in patients with acute lymphoblastic leukemia. We determined levels of uncleaved caspase 2 and caspase 3 by quantitative Western blot analysis in peripheral blood samples of 45 adults with newly diagnosed ALL. We evaluated patient prognostic variables and caspase levels using multivariate logistic and Cox regression models to determine their impact on complete remission rate and overall survival probability. Levels of caspase 2 and, to a lesser degree, caspase 3 were highly associated with cytogenetic abnormalities, with lower levels in the diploid group (P = 0.016 and P = 0.10, respectively). No association between either caspase level and the percentage of bone marrow blasts was found. A high level of caspase 3 (>0.37 as determined graphically) was significantly associated with achieving complete remission (CR; P = 0.006). A multivariate logistic regression analysis including age, WBC count, percentage of peripheral and marrow blasts, hemoglobin, albumin, lactate dehydrogenase, bilirubin, and creatinine determined that a high level of caspase 3 was the most significant predictor of CR (P = 0.025, adjusted), with albumin the only other significant variable (P = 0.031). Caspase 2 levels were not associated with probability of CR. In a multivariate Cox model for survival, however, levels of caspase 2 above 0.37 were associated with a lower survival probability than were levels below that threshold (P = 0.064). High levels of caspase 3 may have a significant effect on achieving CR. Because of the limited power (n = 45) of our study, the significance of caspase 2 and caspase 3 on overall survival remains to be validated by further investigations.

Expression of Bcl-2-related genes in normal and AML progenitors: changes induced by chemotherapy and retinoic acid

The expression of Bcl-2 family members was examined in normal and leukemic hematopoietic cells. Immature hematopoietic progenitor cells (CD34+/33-/13-) did not express Bcl-2 but Bcl-XL, the majority of CD34 cells expressed Bcl-2, Bcl-XL and BAD, and normal promyelocytes (CD34-/33+) lacked expression of both Bcl-2 and Bcl-XL, while leukemic CD34+progenitors and promyelocytes expressed these anti-apoptotic proteins. In AML, Bcl-2 expression was higher on CD34+ than on all AML cells, however, expression of Bcl-2 or Bcl-XL did not predict achievement of complete remission. Surprisingly, low Bcl-2 content was associated with poor survival in a group of patients with poor prognosis cytogenetics. The anti-apoptotic BAD protein was found to be expressed in AML, but was phosphorylated in 41/42 samples. Phosphorylation was found at both sites, Ser 112 and Ser 136. During induction chemotherapy, Bcl-2 levels of CD34 cells increased significantly. In the context of evidence for small numbers of leukemic CD34+ cells expressing very high levels of Bcl-2 prior to therapy, this finding is interpreted as a survival advantage of Bcl-2 overexpressing progenitors and rapid elimination of cells with low Bcl-2. Bcl-2 and Bcl-XL were both expressed in minimal residual disease cells. Downregulation of Bcl-2 mRNA and protein was observed by ATRA and the combination of Ara-C, followed by ATRA, resulted in markedly increased cytotoxicity in HL-60 cells, as compared to Ara-C alone or ATRA followed by Ara-C. Implications of these findings for the development of new therapeutic strategies for AML are discussed.

Altered expression of retinoblastoma (RB) protein in acute myelogenous leukemia does not result from methylation of the Rb promotor

Prior studies demonstrated that expression of the retinoblastoma (RB) protein in acute myelogenous leukemia (AML) is heterogeneous with low expression conferring a poor prognosis. The molecular change(s) responsible for low RB expression in AML are unknown. Since methylation of the RB promoter has been shown to result in decreased expression we hypothesized that this might explain some cases of low RB expression in AML. To investigate this hypothesis Southern blotting and PCR sequencing after bisulfite conversion were used to study the methylation status of the RB gene promoter. DNA and protein lysates were prepared from the mononuclear cell fraction from peripheral blood or bone marrow samples from 46 patients with newly diagnosed AML. By Western blot 16, 22 and 8 patients had low, elevated and hyperphosphorylated patterns of RB expression respectively using previously defined criteria. The SacI endonuclease cuts a 5.7-kb or 6.8 -kb fragment, depending on polymorphism, containing the RB promoter, detected by the probe p123M1.8 that covers the RB promoter region and exon 1. The methylation sensitive endonuclease SacII cuts twice within a key hairpin loop structure in the RB promoter that contains binding sites for AP1, Sp1 and RBF1. Others have demonstrated that methylation within this hairpin loop can decrease RB mRNA transcription by up to 92%. Comparison of the SacI and SacI + SacII digestion fragments showed no evidence of methylation in the promoter region of RB in any of the patients studied. DNA from the promoter region of 11 patients with no/low RB expression was subjected to bisulfite conversion and PCR sequencing. No evidence of methylation was seen by this method either. These results suggests that hypermethylation of the RB promoter region is at best an infrequent event in AML and that RB promoter hypermethylation is not the predominant cause of the low levels of RB expression observed in 20% of AML patients.

Apoptosis. Molecules and mechanisms

This review of the molecules and pathways involved in programmed cell death (apoptosis) discriminates triggers of apoptosis (e.g. chemotherapy, radiation, Fas ligation), modulators of apoptosis (e.g. Bcl-2 family members, Bcl-2 interacting proteins, Apafs, IAPs, and Fas/FasL modulators including FLICE and FLIPs), effectors (caspases 1-13) and cleavage substrates (e.g. PARP). Special consideration is given to the structure-function relationship of Bcl-2 family members and to their post-transcriptional modification. Brief references are made to the role of apoptotic pathway in leukemias and lymphomas and to strategies of modulating apoptotic pathways.

Regulation of AML2/CBFA3 in hematopoietic cells through the retinoic acid receptor alpha-dependent signaling pathway

AML2 is a member of the acute myelogenous leukemia, AML family of transcription factors. The biologic functions of AML1 and AML3 have been well characterized; however, the functional role of AML2 remains unknown. In this study, we found that AML2 protein expressed predominantly in cells of hematopoietic origin is a nuclear serine phosphoprotein associated with the nuclear matrix, and its expression is not cell cycle-related. In HL-60 cells AML2 expression can be induced by all three natural retinoids, all-trans-retinoic acid (RA), 13-cis-RA, and 9-cis-RA in a dose-dependent manner. A synthetic retinoic acid derivative, 4HPR, which neither activates RA receptor (RAR) alpha nor retinoic X receptor alpha was unable to induce the expression of AML2. A RAR-selective activator, TTNPB, induced AML2 expression similar to RA. Our study further showed that AGN193109, a potent RARalpha antagonist, suppressed AML2 expression induced by RA and that a retinoic X receptor pan agonist AGN194204 had no effect on its expression. Taken together, these studies conclusively demonstrated that the expression of AML2 in HL-60 cells is regulated through the RARalpha-specific signaling pathway. Our study further showed that after all-trans-retinoic acid priming, AML2 expression could be augmented by vitamin D(3). Based on these studies we hypothesize that AML2 expression is normally regulated by retinoid/vitamin D nuclear receptors mainly through the RARalpha-dependent signaling pathway and that it may play a role in hematopoietic cell differentiation.

The prognostic impact of BCL2 protein expression in acute myelogenous leukemia varies with cytogenetics

BCL2 protein exerts an antiapoptotic effect on cells and decreases chemosensitivity. To determine whether BCL2 expression is prognostic of patient outcome in acute myelogenous leukemia (AML), we measured its level in 198 newly diagnosed, untreated AML patients by Western blotting using whole-cell lysates from low-density peripheral blood cells. BCL2 expression was not associated with the percentage of blasts (R2 = 0.10), French-American-British classification type, or cytogenetic abnormality. Smoothed martingale residual plots indicated that high BCL2 protein level was an adverse prognostic factor for patients with either favorable or intermediate prognosis cytogenetics [FIPC; inv(16), t(8:21), t(15:17), or diploid or insufficient metaphases] but was a favorable prognostic factor for patients with unfavorable prognosis cytogenetics (UC; -5, -7, +8, 11q23, Ph1, or miscellaneous changes). Patients with FIPC and high BCL2 (highest quartile) had a significantly shorter median survival (78 weeks versus not reached; P = 0.009) than did those with lower (lower three quartiles) levels of BCL2. Among those with UC, as BCL2 level decreased from the fourth quartile to the third or the combined first and second quartiles, the median survival decreased (from 94 to 45 or 17 weeks, respectively; P = 0.003). Lower expression of BCL2 in UC was associated with shorter remission duration (P = 0.05). In multivariate analyses performed using either overall or event-free survival as the end point, for either all patients or within either cytogenetic subgroup, BCL2 level was an independent prognostic factor. Similar analysis revealed that BCL2 level was an independent predictor of remission duration for UC patients as well. These data suggest that BCL2 is involved differently in different types (favorable versus unfavorable) of AML and that therapeutic strategies aimed at modulating BCL2 function may be more likely to work in patients with favorable cytogenetic abnormalities.

Production and culture of HSVtk transduced suicidal lymphocytes induces variable changes in the lymphocyte subset composition

Allogeneic bone marrow transplant followed by donor lymphocyte infusion (DLI) is limited by T cell-mediated graft-versus-host disease (GVHD). A potential solution to alleviate uncontrolled GVHD is to create a controllable suicidal lymphocyte using retroviral transduction of the herpes simplex virus thymidine kinase gene (HSVtk) into the T cell graft. Should GVHD arise, the administration of ganciclovir (GCV) should eliminate the causal T cells. The culture conditions and expansion protocols required to produce suicidal lymphocytes may affect the composition of the T cell product. In this report we describe how T cells from individual donor samples respond to the same culture condition in highly varied ways. Among five donors, two demonstrated predominant expansion of CD4+ cells (with a decrease of CD8+), two donors resulted in predominately CD8+ cells, and one donor developed mainly dual positive CD8+/CD56+ cells. We observed a 20-fold expansion of T cells during the 14 day protocol. The function of the T cells was not affected by the transduction procedures (as tested by 51Cr release assays). In contrast to suicidal lymphocytes prepared using entire T cell populations, T cells pre-selected into CD3+/CD4+ or CD3+/CD8+ subpopulations prior to culture maintained their initial phenotype during the 14 day culture period, with little or no drift. Results from clinical trials using suicidal lymphocytes may be confounded by variance in lymphocyte subset compositions (LSC) and optimal use of suicidal lymphocytes may require separate culture and transduction to control the LSC delivered to the patient.

Expression and function of leptin receptor isoforms in myeloid leukemia and myelodysplastic syndromes: proliferative and anti-apoptotic activities

The receptor for the gene product of the obesity gene, leptin, was recently reported to be expressed on murine and human hematopoietic progenitor cells. Therefore, we studied the expression of the leptin receptor, OB-R, in normal myeloid precursors, human leukemia cell lines, and primary leukemic cells using reverse-transcriptase polymerase chain reaction. In normal hematopoiesis, OB-R was expressed in CD34(+) cells. Normal promyelocytes (CD34(-)33(+) and CD34(-)13(+)) expressed only very low levels of the short, presumably nonsignaling isoform. Both the long and short isoforms of OB-R were expressed in 10 of 22 samples from patients with newly diagnosed primary or secondary acute myeloid leukemia (AML), with a higher incidence of the long isoform in primary AML (87.6% v 28.6%; P =.01). The incidence of OB-R expression was higher in recurrent than in newly diagnosed AML (P <.001), and samples from four patients with refractory AML showed strong expression of both isoforms. Both OB-R isoforms were also expressed in newly diagnosed and recurrent acute promyelocytic leukemia cells but were essentially absent in samples of chronic or acute lymphocytic leukemia. In vitro growth of myeloid leukemic cell lines and of blasts from 14 primary AMLs demonstrated that recombinant human leptin alone induced low level proliferation, significantly (P <.05) increased proliferation induced by recombinant human granulocyte colony-stimulating factor, interleukin 3, and stem cell factor in a subset of AML and increased colony formation (P <.005). Also, leptin reduced apoptosis induced by cytokine withdrawal in MO7E and TF-1 cells. Serum leptin levels correlated only with body mass index (P <. 001) and gender (P =.03). Results confirm the reported expression of leptin receptor in normal CD34(+) cells and demonstrate the frequent expression of leptin receptors in AML blasts. While normal promyelocytes lack receptor expression, leukemic promyelocytes express both isoforms. We also demonstrate proliferative effects of leptin alone and in combination with other physiologic cytokines, and anti-apoptotic properties of leptin. These findings could have implications for the pathophysiology of AML.

Caspase 2 and caspase 3 protein levels as predictors of survival in acute myelogenous leukemia

Because caspase activation is an essential step in programmed cell death (apoptosis) and cytotoxic drug-induced apoptosis is mediated by caspase 2 and caspase 3, we hypothesized that caspase 2 and 3 levels predict clinical outcome in acute myelogenous leukemia (AML). Using quantitative Western blot analysis, we studied the levels of nonactivated (uncleaved) caspase 2 and 3 in peripheral blood low-density cells from 185 patients with newly diagnosed AML. We also measured the level of activated (cleaved) caspase 3 in 41 randomly selected samples from the 185 patients. Finally, we analyzed the effect of caspase 2 and 3 levels and other prognostic variables on patient survival using a multivariate Cox model. We found that median levels of nonactivated caspase 2 and 3 were higher in AML than in normal peripheral blood cells (P < .001 and P <.02, respectively). There was no association between caspase level and either the percentage of peripheral blasts or any specific type of leukemia cell cytogenetic abnormalities. When the effect of each uncleaved caspase was considered individually, a high level of uncleaved caspase 3 (P = .04), but not of caspase 2 (P = .16), was associated with decreased survival. Conversely, a high level of cleaved caspase 3 denoted improved survival and correlated with the inactivation of the DNA-repair enzyme poly(ADP-ribose) polymerase. Thus, cleaved caspase 3 could stimulate the apoptotic cascade further, and lack of its activation likely caused an accumulation of the uncleaved caspase. Although uncleaved caspase 2 level per se had no prognostic significance, the interactive effect of high levels of both uncleaved caspase 2 and 3 denoted very poor survival (P < .001) and had the largest effect of all prognostic variables (P < .001; estimated relative risk, 2.49; 95% confidence interval, 1.59 to 3. 90). Taken together, caspase 2 and caspase 3 protein levels obtained at diagnosis may constitute a reliable prognostic factor in AML.

Recommended guidelines for the treatment of chemotherapy-induced diarrhea

PURPOSE

Management of chemotherapy-induced diarrhea (CID) has customarily involved symptomatic treatment with opioids in conjunction with supportive care. Alternatively, patients refractory to conventional therapy have been given octreotide, a somatostatin analogue. Although this agent has been effective against CID, no widely accepted treatment guidelines that incorporate its use currently exist. An expert multidisciplinary panel was convened to formulate clinical practice guidelines for the treatment of CID.

METHODS

The panel reviewed clinical data on the management of CID reported in the literature and analyzed currently available tools used to assess CID. Expert consensus was applied when published data were insufficient. Panel members also considered the effect of CID on quality of life and the cost-effectiveness and efficacy of different pharmacologic approaches. Effective resolution of CID and decreases in the need for supportive care or hospitalization were considered to be primary goals in the formulation of the guidelines.

RESULTS

The panel formulated suggested practice guidelines for the management of CID that detail recommendations for the assessment and evaluation of diarrhea and the sequence and duration of administration of specific pharmacologic agents.

CONCLUSION

The consensus of the panel was that standardized assessment and management of diarrhea is required to effectively control CID. The panel agreed that further data from a National Cancer Institute (NCI)-sponsored intergroup trial is required to determine the optimal dosage of octreotide and its cost in the treatment of cancer. The panel also agreed that further clinical research is warranted to address significant questions about the most effective way to assess and treat CID.

The role of apoptosis in the pathogenesis, prognosis, and therapy of hematologic malignancies

Apoptosis or programmed cell death is a cellular process involved in the regulation of cell proliferation. Alterations in the expression of apoptosis-related proteins are a common observation in hematologic malignancies. Moreover, increased expression levels of certain apoptosis-related proteins have been correlated with poorer clinical outcomes. Recent advances in the studies of the molecular events associated with the regulation of apoptosis have greatly improved our understanding of the etiology of human leukemias and myelodysplasias. Furthermore, these studies have helped identify proteins and cellular processes that are unique to leukemic cells and that could serve as therapeutic targets, diagnostic markers, and useful indicators of prognosis. Measurements of the levels of expression of apoptotic proteins could be used to help customize the therapeutic modalities that are most effective for each patient.

Low and maximally phosphorylated levels of the retinoblastoma protein confer poor prognosis in newly diagnosed acute myelogenous leukemia: a prospective study

A prior retrospective study suggested that the level of retinoblastoma protein (RB) expression was prognostic for survival in acute myelogenous leukemia (AML). Individuals with no/low RB protein expression were considered to have loss of RB function, and those with maximally phosphorylated (maxphos) RB were also felt to have nonfunctional RB. To confirm this, we prospectively investigated whether the level of RB expression was prognostic in AML in a larger cohort of patients. RB level was measured by Western blot and immunohistochemical analysis on peripheral blood samples from 210 newly diagnosed AML patients. Patients were divided into three groups based on the level of RB protein expression (i.e., no or low, elevated, and maxphos) or into two groups on the basis of presumed RB function, altered function (AF-RB, low and maxphos RB), versus normal function (NF-RB, elevated RB). By combined results of Western blot and immunohistochemical analysis, 20%, 65%, and 15% of patients had low, elevated, and maxphos RB, respectively. Most patients with acute promyelocytic leukemia (APL) with a French-American-British classification of M3 were in the low RB group, likely reflecting a lower proliferative rate of promyelocytes. Analysis was performed with and without these APL patients. The median survival was significantly shorter for both patients with low RB expression (48 weeks, P = 0.05, including APL patients; 34 weeks, corrected P = 0.008, with APL patients excluded) and maxphos RB expression (51 weeks, P = 0.007) compared to those with elevated RB expression (122 weeks including and 98 weeks excluding APL patients). Differences were greatest among patients with nonfavorable prognosis cytogenetics (median survival, 34 weeks versus 85 weeks; corrected P = 0.001 for AF-RB versus NF-RB). Remission duration was also significantly shorter for non-APL patients with AF-RB versus NF-RB (median survival, 36 weeks versus not reached; corrected P = 0.02). In multivariate analyses, including cytogenetics, performance status, age, antecedent hematological disorder, and RB status, with and without APL patients included, no/low and maxphos-RB protein expression were independent predictors for poorer survival. This prospective study confirms that the level of expression of RB is a strong prognostic factor in AML, with an inferior survival experience being associated with no/low RB and maxphos RB expression. Therefore, therapeutic decisions based on the level of RB expression may be indicated, and protocols to incorporate this are currently under development.

CECA-cyclophosphamide, etoposide, carboplatin and cytosine arabinoside--a new salvage regimen for relapsed or refractory acute myelogenous leukemia

In an effort to develop more effective therapy for patients with refractory or relapsed acute myelogenous leukemia (R-AML) we combined three drugs with proven activity in AML, that are not typically used in induction regimens, with cytosine arabinoside (ara-C). Twenty-five patients (3 primary refractory, 22 relapsed) were treated. Patients received 3 days of "CECA" therapy as follows: cyclophosphamide (CTX) 1 g/m2 i.v. over 2 hrs., etoposide (VP-16) 200 mg/m2 i.v. over 3 hr, carboplatin (CBP) 150 mg/m2 i.v. over 24 hours and ara-C 1 g/m2 over 2 hr. Peripheral circulating blasts cleared in 24 cases (96%), and marrow aplasia was achieved in 19 (76%). There were 3 complete remissions (CR), 1 patient died before day 14, 5 died aplastic 14 or more days from the start of therapy, 5 had primary resistant disease, and 10 had secondary resistance i.e., leukemia reappearing after developing aplasia and 1 was lost to follow up 6 weeks into therapy. Two of the patients achieving CR received allogeneic BMT in CR (at 18 and 22 weeks): one died of fungal infection on day 50 and the other, who had CNS involvement at relapse, is alive 24 months post transplant. Toxicity was tolerable: one patient each developed grade III diarrhea and mucositis, another had grade III cardiac toxicity, a fourth developed a grade IV bilirubin elevation. Single, 2, and 3 or more infectious episodes occurred in 10, 5 and 4 patients respectively. This regimen showed definite anti-leukemic activity: the 3 patients achieving CR were among 23 patients with a 1%, 10% or 20% expectation for second CR attainment. The CECA regimen should be investigated in better prognosis salvage groups.

Phase I study of mitoxantrone plus etoposide with multidrug blockade by SDZ PSC-833 in relapsed or refractory acute myelogenous leukemia

PURPOSE

Expression of the multidrug resistance gene (MDR1) p170 protein is frequent in leukemic blasts from patients with relapsed acute myelogenous leukemia (AML). A phase I study using the nonimmunosuppressive MDR1 blocker SDZ PSC-833 (PSC) in combination with mitoxantrone (MITO) and etoposide (VP) was performed.

PATIENTS AND METHODS

Starting doses (LVL0) of MITO (3.25 mg/m2/d on days 1 and 3 to 6) and VP (210 mg/m2/d on days 1 and 3 to 5) were 40% of the maximal-tolerated dose (MTD) from a prior study. A 1.5-mg/kg loading dose of PSC was followed by a 120-hour continuous infusion of 10 mg/kg/d on days 2 to 6. Blood samples for PSC, MITO, and VP pharmacokinetics (PK) were taken on days 1 and 3, and samples for MDR1 expression were taken on day 0.

RESULTS

Severe mucositis developed in all patients at LVL0; therefore, MITO and VP doses were reduced to 2.5 and 170 mg/m2 (LVL-1) for the next seven patients, and this dose proved to be MTD. All LVL0 and three LVL-1 patients had transient elevations in the serum bilirubin level to > or = 4 mg/dL. Serum creatinine level increased to greater than 2 mg/dL in one case. There were no other grade 3 or 4 nonhematologic toxicities observed. The peripheral blood was cleared of leukemia in three LVL0 and four LVL-1 patients. The marrow was cleared of leukemic cells in one LVL0 and five LVL-1 patients, and a significant reduction in marrow leukemic infiltrate was observed in eight of 10. No patient achieved complete remission (CR), and all died of progressive disease (n = 8) or infection (n = 2). MDR1 expression was detected by fluorescent-activated cell sorter (FACS) analysis in five of seven cases. An elevated MDR1 mRNA level was detected by quantitative polymerase chain reaction (Q-PCR) in six of eight cases studied. Clearing of leukemia cells from the marrow occurred in four of six MDR1-positive and one of three MDR1-negative patients. Despite the fact that LVL0 doses had to be reduced due to toxicity, coadministration of PSC did not produce a consistent effect on MITO PK; however, it did repeatedly lead to increased levels of VP in the serum.

CONCLUSION

We conclude that PSC-MITO-VP is a tolerable regimen with antileukemic activity. Addition of PSC necessitated a 66% reduction in MITO and VP doses from a prior study without PSC.

Molecular study of hairy cell leukemia variant with biclonal paraproteinemia

We report an unusual case of hairy cell leukemia variant with IgA and IgG-lambda biclonal gammopathy exhibiting light chain and a surface immunoglobulin class different from that of the paraproteins. In addition, we documented by gene rearrangement study that the hairy cell leukemia variant clone appears independent from the paraprotein-producing cells. The kappa light chain was expressed on the surface of hairy cell leukemia variant cells. Southern blot analysis revealed rearrangement of the kappa-light-chain gene and germline configuration of lambda-light-chain gene. We observed significant clinical improvement and reduction in the leukemic infiltrate in the patient after treatment with 2-chlorodeoxyadenosine (2-CdA). The intensity of the rearranged kappa-light-chain gene band decreased with therapy and increased at relapse without significant change of the paraproteins. Previously reported cases of hairy cell leukemia variant with paraproteins are reviewed, and our patient's contribution to the understanding of this association is stressed.

Clinical and laboratory studies of 2-chlorodeoxyadenosine +/- cytosine arabinoside for relapsed or refractory acute myelogenous leukemia in adults

Previous studies in pediatric patients with acute myelogenous leukemia (AML) have suggested that 2-chlorodeoxyadenosine (2CdA) is an effective therapeutic agent. Santana et al (J Clin Oncol 1992; 10: 364-370) reported a CR rate of 8/17 (95% Cl 23-72%) in children with relapsed AML and a median first CR of 21 months. The activity of 2CdA in adults with relapsed or refractory leukemia was therefore investigated in a phase I study. In the phase II study, based on biochemical modulation rationale, 2CdA was combined with Ara-C for adults with relapsed AML to test the effectiveness of this combination therapy. In the phase I study 27 patients (25 AML and two MDS) with a median first CR duration of 21 weeks, received 2CdA at doses ranging from 5 to 13 mg/m2/day by continuous infusion (CI) for 7 days. In vitro and ex vivo pharmacologic studies performed to determine the effect of pretreatment with 2CdA on Ara-CTP accumulation in leukemic blasts demonstrated a 50-65% increase in the rate of Ara-CTP accumulation. Based on this biochemical modulation, 2CdA (12 mg/m2/day x 5 days by CI) was combined with Ara-C (1 g/m2/day over 2 h) in a phase II study. Seventeen patients (15 AML, two MDS) with relapsed AML (median 1st CR of 19 weeks) were treated. In the phase I study two patients died before the day 14 marrow (ED). Marrow hypoplasia developed in 16 of the remaining 25. Leukemic regrowth occurred in nine after a median hypoplastic period of 2 weeks (range 1-3 weeks). The other seven patients died with aplastic marrows, median duration of hypoplasia was 2 weeks, range 1-4 weeks. None achieved CR and the median survival was 10.5 weeks. Toxicity generally was mild except for three late occurring cases of grade III or IV renal dysfunction and two cases of tumor lysis syndrome. The MTD was 10.8 mg/m2/day x 7 days. In the phase II study two patients, both with AML, achieved CR (95% CI 1-33%). In both cases leukemia relapsed after 10 weeks and 17 weeks. There was one ED. Most (11/16) cleared their marrow although leukemic infiltrate regrew in six cases. Toxicity was generally mild, with two episodes of grade 2 GI bleeding, one episode of severe renal dysfunction and one case of grade 2 CNS toxicity. We conclude that as a single agent 2CdA at the MTD is a cytoreductive agent but is not sufficient to achieve CR in adults with relapsed AML. While combination of Ara-C with 2CdA increases the Ara-CTP uptake in these heavily treated patients this regimen does not appear to be an improvement over existing modalities.

Idarubicin cardiotoxicity: a retrospective study in acute myeloid leukemia and myelodysplasia

PURPOSE

To estimate the incidence of idarubicin (IDA)-related cardiomyopathy in acute myeloid leukemia (AML) and myelodysplasia (MDS).

PATIENTS AND METHODS

We analyzed a group of 127 AML/MDS patients who received IDA-based induction and postremission or salvage therapy and achieved a complete remission (CR) that lasted > or = 12 weeks for the development of IDA-related congestive heart failure (CHF). CHF was defined as definite if a resting left ventricular ejection fraction (LVEF) of < or = 45% measured by radionuclide ventriculogram (RV) accompanied the clinical diagnosis of CHF, which had to be made during or within 6 months of receiving IDA and for which no other cause was apparent; without RV confirmation, the diagnosis was considered probable. Patients who had RVs performed were evaluated for decreasing LVEF. Older age (> or = 70 years), prior/sequential anthracycline/mitoxantrone (anthraquinone) therapy, and cardiac disease/hypertension were evaluated as risk factors for the development of CHF.

RESULTS

One hundred fifteen patients were assessable (median age, 40 years; median dose, 96 mg/m2). Sixty-five had RVs performed during therapy; 43 had risk factors. The probability of IDA-related cardiomyopathy was 5% at a cumulative IDA dose of 150 to 290 mg/m2, with 18 patients receiving doses greater than 150 mg/m2. At a cumulative IDA dose of 150 mg/m2, the probability of a mild or greater asymptomatic decrease probability of a mild or greater asymptomatic decrease in LVEF (> or = 10% to a level < or = 50%) was 18%, whereas the probability of a moderate or greater asymptomatic decrease in LVEF (> or = 15% to a level < or = 45%) was 7%. No patient with asymptomatic LVEF decreases developed CHF. CHF was more frequent in patients with prior/sequential exposure to anthracyclines/mitoxantrone (P = .01).

CONCLUSION

In this patient group, IDA-related cardiomyopathy was uncommon with cumulative IDA doses of up to 290 mg/m2. Asymptomatic LVEF decreases were more frequent, but their predictive value for the development of CHF is unclear.

Analysis of CD7 expression in acute myelogenous leukemia: martingale residual plots combined with 'optimal' cutpoint analysis reveals absence of prognostic significance

Conflicting results exist regarding the prognostic importance of CD7 expression in acute myelogenous leukemia (AML). Differences in the method of determining CD7 positivity, the antibody used, the therapy administered, and the CD7 level used as a cutoff point to reduce it to a binary variable have all been postulated to account for the discordant findings. We determined the level of CD7 expression by flow cytometric analysis using the Leu9 monoclonal antibody in 331 patients with newly diagnosed AML and attempted to determine the impact of CD7 on AML prognosis. This study used the same methodology and antibody as three of the four studies that reported a positive association between CD7 expression and prognosis in AML. Optimal cutpoint analysis was used to divide the population into CD7-positive (CD7+) (>10.5% expression) and CD7-negative (CD7-) (< 10.5% expression) groups with the largest survival difference. At the optimal cutpoint, the difference in survival was not statistically significantly different (P = 0.068 uncorrected, P = 0.244 corrected for optimal cutpoint search). There was a marked imbalance in the distribution of favorable cytogenetic abnormalities [t(8;21), inversion 16, t(15;17)], with 95% segregating to the CD7- group. Analysis excluding patients with favorable cytogenetic abnormalities revealed no prognostic importance for CD7 expression (P = 0.24 uncorrected). The response rate (CR) and survival experiences of CD7+ and CD7- patients were similar with six different regimens. CD7 expression was not a significant independent prognostic factor in a Cox regression model that included cytogenetics as a predictive variable, but it was marginally significant when cytogenetics was excluded. We conclude that regardless of the antibody used, the therapy received, or the cutoff point selected to determine CD7 expression, CD7 is not associated with response rate, prognosis, or survival in AML. The 'optimal cutoff point analysis' utilized in this study has applicability to other biologic parameters as well.

Quantitative expression of proliferating cell nuclear antigen by western blot (PCNAWB) in peripheral blasts correlates with remission induction in patients with acute myelogenous leukemia

Proliferating cell nuclear antigen (PCNA) is a 36-kD nuclear protein that functions as a cofactor of delta DNA polymerase which is regulated in a cell cycle-dependent fashion. PCNA expression also increases when cells are actively engaged in DNA repair. We used Western blotting (WB) to measure the level of expression of PCNA in peripheral blasts of 36 adult acute myelogenous leukemia (AML) patients treated with Ara-C based induction regimens. PCNA levels correlated positively with the percentage of cells in S+G2M of the cell cycle. Logistic regression analysis revealed PCNA (beta = 4.5162; p = 0.0260) together with age (beta = 0.1777; p = 0.0364) as independent variables for remission induction: high PCNA levels were associated with poor response to induction therapy. PCNA expression was not, however, a predictor of survival in this subset of patients. We conclude that PCNA levels in this disease may be important for predicting response to Ara-C based remission induction chemotherapy.

High levels of constitutive WAF1/Cip1 protein are associated with chemoresistance in acute myelogenous leukemia

The WAF1/Cip1 gene product is an important regulator at the G1 checkpoint in the cell cycle. WAF1/Cip1 expression can be activated through p53-dependent and p53-independent pathways. The WAF1/Cip1 protein binds to cyclin-dependent kinase complexes and inhibits the kinase activity that is required for cell cycle progression. In this preliminary study, we analyzed with Western blot assays the steady-state levels of the WAF1/Cip1 protein in the leukemia cells of 100 untreated acute myelogenous leukemia (AML) patients. Normal bone marrow cells from six donors were used as a control. The results of these analyses showed that the levels of the WAF1/Cip1 protein were very low in normal marrow cells and in the leukemia cells of 83 AML patients. High levels of WAF1/Cip1 were detected in 17 patients; these patients with high WAF1/Cip1 levels were significantly less likely to achieve complete remission (41% versus 69%, P = 0.03) and were four times as likely to be resistant to therapy (47% versus 12%, P = 0.003) as patients with very low levels of WAF1/Cip1. Median survival was 38 weeks for patients having very low expression levels versus 11 weeks for patients having high expression levels (P = 0.04). The WAF1/Cip1 level was an independent predictor for response but not survival in a stepwise multivariate regression analysis. Southern blotting analyses did not detect deletion of the WAF1/Cip1 gene in the 12 negative WAF1/Cip1 AML samples tested. Also, the level of WAF1/Cip1 protein expression was not correlated with overexpression of cyclin D1, cyclin E, proliferating cell nuclear antigen, cyclin-dependent kinase 4, or p53 in the leukemia cells. However, the levels of cyclin D1, cyclin E, and cyclin-dependent kinase 4 were elevated in most of the AML samples compared with that in normal marrow. We hypothesize that high-level constitutively expressed WAF1/Cip1 in tumor cells may result in an indolent state that is refractory to chemotherapy drugs. We conclude that the WAF1/Cip1 expression level may be an important prognostic factor for response to therapy and survival in AML patients.

Growth-factor stimulation reveals two mechanisms of retinoblastoma gene inactivation in human myelogenous leukemia cells

Mutation or deletion of the retinoblastoma tumor suppressor gene (Rb) or abnormal Rb protein expression is found in many types of human solid tumors. Low or absent levels of Rb protein are usually found in the leukemic cells of patients with acute myelogenous leukemia (AML) who have an extremely poor prognosis. The absence of Rb protein in these AML cells could result from defects in the Rb gene or from abnormal cell cycle regulation that affects Rb expression. To test these possibilities and to examine whether a low level of Rb protein in AML cells could be up-regulated, we studied the effect that growth factors interleukin 3 (IL3) and granulocyte-macrophage colony stimulating factor (GM-CSF) had on the levels of Rb protein and Rb phosphorylation in AML cells from patients with low Rb or no Rb protein expression. We observed three responses to growth factor-stimulation in leukemic cells taken from patients with AML: (1) some AML cell samples entered a proliferative phase, and Rb protein levels increased with the appearance of normally phosphorylated forms of Rb protein and positive nuclear staining for Rb protein; (2) some AML cell samples became more proliferative, but the levels of Rb protein remained low or absent; and (3) some AML cell samples showed no response. These results indicate that at least two different mechanisms may be responsible for the lack of Rb protein in the leukemic cells of some patients with AML.

Levels of retinoblastoma protein expression in newly diagnosed acute myelogenous leukemia

The relationship between the level of retinoblastoma protein (RB) expression and the survival of 113 newly diagnosed acute myelogenous leukemia (AML) patients was studied. Western blotting was used to determine the level of RB protein present in peripheral blood leukemia cells and results were confirmed in 26 patients by immunohistochemistry. The leukemic cells from 22/113 AML patients (19%) contained RB protein at levels that were equal to or less than the level of RB observed in the mononuclear cell fraction of peripheral blood from normal individuals (Low RB). Levels of RB greater than that of normal blood (Elevated RB) were seen in 91 patients (81%). The median survival of patients with low RB was significantly shorter than that seen in patients with elevated RB, 12 weeks versus 40 weeks (P = .02). Remission induction frequency was 36% in low RB patients compared with 68% in AML patients with elevated RB (P = .01). Multivariate analysis showed that low RB protein level was an independent prognostic factor predictive or poor survival after allowing for other known prognostic factors. These data suggest that a low level of the RB protein at the time of diagnosis is associated with shortened survival in AML patients because of inferior response to conventional therapy. Monitoring of the RB level could identify a subgroup of AML patients with an extremely poor prognosis when treated with chemotherapy alone, who would be eligible for alternative therapeutic strategies.

Retinoblastoma protein expression is frequently altered in chronic lymphocytic leukemia

The detection of abnormalities at the retinoblastoma (RB) locus by cytogenetics, Southern blot, and fluorescence in situ hybridization studies suggests that the RB gene has a role in chronic lymphocytic leukemia (CLL). To further study this role, we determined the level of RB protein present in the mononuclear cell fraction derived from peripheral blood or bone marrow samples from 74 patients with CLL, by Western blotting. Compared to similarly prepared samples from the peripheral blood of normal individuals, the level of RB in CLL cells was less than normal in 42% of patients, equal to normal in 22% of patients, and in excess of normal in 36% of patients. Regardless of whether the source of the sample was blood or marrow or if the patients were untreated or previously treated, similar rates of low, normal, and elevated RB levels were observed. RB protein in the CLL patient samples was never phosphorylated. RB levels showed no correlation with the lymphocyte doubling time or with proliferating cell nuclear antigen levels. Low RB levels could arise from genetic alterations of the RB gene or altered regulation of expression. To determine which was occurring, we stimulated the cells from 27 CLL patients in culture with either phytohemagglutinin or pokeweed mitogen in an attempt to induce RB expression and phosphorylation. Among patients with low levels of RB, expression was induced in 46% (6 of 13), and phosphorylation of RB was seen in 31% (4 of 13). Increased expression of phosphorylated RB was induced in 80% (4 of 5) of patients with normal levels of RB and in 78% (7 of 9) of patients with high levels of RB. This study demonstrates that absent RB expression occurs commonly in patients with CLL. Intrinsic abnormalities of the RB gene may be present in those patients with low levels of RB that could not be stimulated by mitogens, while regulatory abnormalities located in trans to the RB gene may occur in the other half. Given the importance that RB levels play in other cancers, the prognostic implication of low RB levels should be studied in CLL.

Neurotoxicity associated with fludarabine and cytosine arabinoside chemotherapy for acute leukemia and myelodysplasia

Neurological toxicity occurred in 8/219 patients treated with fludarabine (FAMP), 30 mg/m2 per day and cytosine arabinoside (Ara-C), 0.5 g/m2 per hour for 2-6 hours for 5 days, for new or relapsed acute leukemia or myelodysplasia. Two patients developed severe, progressive cerebral dysfunction that was ultimately fatal. This toxicity was similar to that seen with high-dose fludarabine therapy and was limited to patients with serum creatine > or = 2.0 mg/dl and age over 60 years, occurring in 2/9 such patients compared to 0/210 among the other patients (p < 0.005). Since FAMP is partially excreted by the kidney, toxicity in these two patients was likely due to receiving an effectively high dose of FAMP. Five patients developed peripheral neuropathy but there was no association with age, creatinine, dose of Ara-C, or number of courses. A patient, who also received intrathecal Ara-C, developed myelopathy. At this dose rate and duration of Ara-C peripheral neuropathy rarely arises, and cerebral toxicity is not seen. Neither toxicity was observed in 481 chronic lymphocytic leukemia patients treated with FAMP alone, by the same dose and schedule, suggesting that combination with Ara-C is important for the development of at least the peripheral neuropathy. The incidence of neurotoxicity with FAMP/Ara-C is low especially in comparison with high-dose Ara-C therapy (3 g/m2 over 2 hours). Cerebral toxicity can likely be decreased by dose reduction of FAMP in patients with increased creatinine and peripheral neuropathy decreased by detailed neurological examination before courses of FAMP/Ara-C.

Clinical implications of decreased retinoblastoma protein expression in acute myelogenous leukemia

The retinoblastoma (RB) protein levels in blast-enriched mononuclear fractions from the peripheral blood of 33 newly diagnosed patients with acute myelogenous leukemia were studied. Ten patients who had previously been treated were also analyzed, nine of whom had achieved prior complete remission. Low RB protein expression was found in 13 of 43 (30%) of the acute myelogenous leukemia patients as determined by Western blotting and immunochemical analysis. Of particular interest among the 20 newly diagnosed patients treated with the same therapeutic regimen, the median survival was 39 days for those with low RB protein expression compared to 333 days for those with high levels of RB protein expression in their leukemic cells (P less than or equal to 0.02). This preliminary study suggests that decreases of RB protein expression in peripheral blood of myeloid leukemic cells occur frequently and may be associated with shortened survival of acute myelogenous leukemia patients.

Chromosomal abnormalities in adult non-endemic Burkitt's lymphoma and leukemia: 22 new reports and a review of 148 cases from the literature

Tumour cell karyotypes from patients with Burkitt lymphoma (BL) or Burkitt's type leukemia (ALL3) were studied for correlation with survival, bone marrow and cerebral spinal fluid involvement (CSF), human immunodeficiency virus (HIV) serology, and for recurrent cytogenetic abnormalities. The records of 22 patients with BL from our institution and of 148 cases of BL and ALL3 reported in the literature with karyotypes were evaluated for clinical and cytological features. Overall survival was only 28 per cent and 88 per cent of deaths occurred within the first nine months after diagnosis. Those who survived at least 18 months were unlikely to relapse. Age and gender did not significantly affect survival. Patients presenting with advanced Ann Arbor stage, bone marrow or CSF involvement had lower survival rates. The association of translocations involving chromosome band 8q24 with this disease is confirmed. Sixty-two per cent of karyotypes had t(8;14)(q24;q32) translocations; the recognized variant translocations t(8;22)(q24;q11) and t(2;8)(p12;q24) affected 12 per cent and 9 per cent respectively. Seventeen per cent had abnormal karyotypes but no classic translocation. Patients with variant translocations had the poorest survival rates, and those with the classic t(8;14)(q24;q32) did the best. Despite a small sample size, the variant translocation t(8;22)(q24;q11) appeared to occur at an increased frequency in the patients with AIDS. In the entire group, recurrent involvement of chromosome regions 1q2, 6q11-14 and 17p1 suggests that alteration of genes at these loci, B Cell Growth Factor (BCGF) at 1q2 and p53 on 17p, may contribute to the development and progression of this tumour. Similarly, the frequent trisomies of chromosomes 7, 8, 12 and 18 may indicate an effect on tumour cell growth due to increased gene dosage. Trisomy 12 was found in eight tumours, five from patients with AIDS, suggesting that chromosome 12 has a site or gene whose allelic dosage is selected for in AIDS related lymphoma cells. Cytogenetic studies of adult Burkitt lymphoma and leukemia suggest several likely loci for gene alterations that in conjunction with myc translocations can lead to tumorigenesis.

Influence of vascular and transpulmonary pressures on endothelial vesicles in nonedematous and edematous lungs

We examined the effects of vascular and transpulmonary (Ptp) pressures on endothelial vesicles in nonedematous and edematous dog lungs by transmission electron microscopy (TEM). Edema was defined as a 30% increase in lung weight. Lungs were prepared for TEM by rapid freezing followed by freeze substitution. Using a random sampling procedure, the size and numerical density (Nv) of vesicles was obtained by standard morphometric techniques and the percentage of cytoplasm occupied by vesicles (Vv) calculated. Results show that at Ptp = 5 cm H2O, vascular pressure has no influence on the variables examined in nonedematous and edematous lungs. At Ptp = 25 cm H2O, increases in vascular pressure were associated with significant decreases in the percent cytoplasm occupied by vesicles for both series of experiments. When nonedematous lungs were compared to edematous lungs, we found increases in vesicle size, Nv, and the percentage of endothelial cell cytoplasm occupied by vesicles. The results confirm the increase in vesicles associated with edema. This result does not appear to be due to increased vascular pressure per se, although time related influences could be involved.