Pivanex, a histone deacetylase inhibitor, induces changes in BCR-ABL expression and when combined with STI571, acts synergistically in a chronic myelocytic leukemia cell line.

Chronic myelogenous leukemia (CML) is associated with the high TK activity chimeric protein BCR-ABL, known to contribute to cell tumorogenicity, resistance to apoptosis and differentiation. STI571, the TK inhibitor, is the current treatment for CML. One possible approach to overcome STI571 resistance appearing in some cases, involves the combination of histone deacetylase inhibitors (HDI) and STI571. We demonstrated that in K562, the CML cell line, pivaloyloxymethyl butyrate (Pivanex)-induced apoptosis, differentiation and reduced BCR-ABL protein levels and that the combination of Pivanex with STI571 acted synergistically. These data suggest the possible benefit of combining this HDI with STI571 for treatment of CML.

The interaction of hemin and bilirubin with the human red cell membrane.

The incubation of 0.5% suspension of fresh normal erythrocytes with hemin or bilirubin resulted in substantial hemolysis. The amount of hemolysis achieved depended on the concentration of the lytic agents. In each concentration maximum hemolysis was reached within half an hour. The hemolytic effect was somewhat dependent on temperature. Comparison with the hemolytic effect of hemin on mice (Chau, A.C. and Fitch, C.D. (1980) J. Clin. Invest. 66, 856-858) showed that although both cells undergo hemolysis by hemin, the behaviour of each red cell type is different. Centrifugation and fluorescence quenching of membrane embedded probe revealed that both hemin and bilirubin bind to the red cell membrane, hemin having higher affinity. The reaction was found to be hydrophobic and therefore independent of ionic strength. The high affinity of the membrane for hemin was shown by its ability to compete successfully with globin for hemin. Electron microscopy of the red cells which underwent hemolysis indicated cell damage and some membrane destruction. Red cell ghosts were totally disrupted when saturated with hemin. These results suggest an explanation for hemolytic events occurring in cases such as elevation of serum bilirubin or abnormalities leading to hemin release by hemoglobin.

Accumulation and drainage of hemin in the red cell membrane.

The subject of hemin intercalation in red cell membranes and the correlation of the accumulated hemin level with the membrane pathology was studied. Methods which made use of dioxan and octan-2-ol mixtures to quantitate small amounts of hemin in membranes were developed. Applying these methods, hemin levels were measured in the cytoskeleton and the remaining lipid core of various red cell membranes. The amount of hemin, in both membrane fractions, was higher in pathological cells of sickle cell anemia and beta-thalassemia as compared to normal circulating cells. Correlation exists between the amount of the membrane-accumulated hemin and the severity of the disease. The level of hemin in the membrane was found to be age dependent, old cells in circulation accumulating more hemin than young cells. The level of hemin in all cells tested was much lower than the amount found previously to cause immediate hemolysis when applied externally (Kirschner-Zilber, I., Rabizadeh, E. and Shaklai, N. (1982) Biochim. Biophys. Acta 690, 20-30). This was explained by the differences between the process leading to immediate lysis and membrane changes recognized as pathological by the in-vivo sequestration mechanism. In search of a physiological mechanism which may drain the cell membrane from the hazardeous hemin, albumin, the main serum protein, was found capable of serving as an efficient agent for extracting hemin trapped in red cell membranes. It is suggested that under normal conditions albumin extracts enough hemin to leave the erythrocyte with unharmful hemin amounts, however, under pathological conditions greater amounts accumulate leading to a shorter cell life span.

Bcl-2, Bcl-X, Bax, and Bak expression in short- and long-lived patients with diffuse large B-cell lymphomas.

Long-term cure is now possible for approximately 50% of all patients with aggressive non-Hodgkin's lymphoma (NHL). Apoptosis-related proteins play an important role in the chemosensitivity or chemoresistance of tumors. We examined the role of Bcl-2 family proteins in aggressive NHL. We retrospectively selected two groups of patients by clinical outcome: 24 patients with chemoresponsive disease and long survival (median, 88 months); and 20 patients with chemoresistant disease and short survival (median, 8 months). The expression of the apoptosis-regulating proteins, Bcl-2, Bcl-X, Bax, and Bak, in the initial biopsy samples was examined with immunohistochemical methods. Specimens containing >10% immunostained tumor cells were considered immunopositive. An inverse association was found between length of patient survival and expression of Bcl-2, Bcl-X, and Bax. Bcl-2 was expressed in 75% of short-lived patients but in only 42% of the long-lived ones (P = 0.026). Bcl-X expression was also higher in the short-lived patients (40% versus 12.5%; P = 0.036). Unexpectedly, Bax expression was strongly associated with short survival (60% versus 21%; P = 0.008). Several combinations of protein expression, i.e., Bcl-2 with Bax, Bcl-2 with Bcl-X, and Bcl-X with Bax, were different between the groups: a positive expression of these proteins was found in the short-lived patients. Furthermore, a strong association was found between the expression of Bcl-2 and Bcl-X, suggesting that Bcl-X potentiates rather than replaces the effect of Bcl-2 in NHL. In diffuse large B-cell NHL, Bcl-2, Bcl-X, and Bax expression alone or in combination is associated with chemoresistance and shortterm survival.

Acute leukemia detection rate by automated blood count parameters and peripheral smear review.

INTRODUCTION: It is unclear what minimal criteria will identify all new cases of acute leukemia in adults in various settings. METHODS: To determine the adult acute leukemia detection rate of the various criteria, we recorded complete blood count (CBC) test results from consecutive patients with leukemia (130 hospitalized patients and 96 outpatients) and from consecutive patients without leukemia (34,827 hospitalized and 33,695 outpatients). RESULTS: Basic criteria for a reflex review (hemoglobin, platelets, and a five-part differential) detected 91% of new hospital leukemia patients (118 of 130) compared to 75% (72 of 96) outpatients. No cases were missed if we did reflex testing when there was either one of the basic criteria or an increased proportion of large unstained cells (LUC), but five cases were missed using the blast flag instead of the LUC. Adding the LUC to basic criteria resulted in the detection of all cases of acute leukemia. The cost of detection of one case of acute leukemia was 1029 and 425 peripheral smear reviews in hospital and outpatients, respectively. CONCLUSION: We conclude that basic criteria available on most hematology analyzers along with the LUC identify all adult patients with acute leukemia in both hospital and outpatient settings with minimal peripheral smear review rates.

Rapid alteration of c-myc and c-jun expression in leukemic cells induced to differentiate by a butyric acid prodrug.

The novel prodrug of butyric acid (BA), pivaloyloxymethyl butyrate, has been shown, in vitro, to induce differentiation and inhibit leukemic cell proliferation. The prodrug affects the cells in vitro at lower concentration and at least 100 times faster than does (BA). We have compared the ability of BA with that of its prodrug AN-9 to modulate the expression of the early regulating genes, c-myc and c-jun, in HL-60 cells. Exposure of HL-60 cells to the prodrug resulted in a decrease of c-myc and an increase of c-jun expression. The prodrug elicited this effect at lower concentrations and at least 100 times faster than BA. Since changes in the expression of c-myc and c-jun occur minutes after exposure of the cells to the prodrug, these genes are likely to play a major role in the early stages of the differentiation pathway.

Novel anticancer prodrugs of butyric acid. 2.

The antitumor activity of novel prodrugs butyric acid was examined. The in vitro effect of the compounds on induction of cytodifferentiation and on inhibition of proliferation and clonogenicity showed that (pivaloyloxy)methyl butyrate (1a) (labeled AN-9) was the most active agent. SAR's suggested that its activity stemmed from hydrolytically released butyric acid. In vivo, 1a displayed antitumor activity in B16F0 melanoma primary cancer model, manifested by a significant increase in the life span of the treated animals. Murine lung tumor burden, induced by injection of the highly metastatic melanoma cells (B16F10.9), was decreased by 1a. It also displayed a significant therapeutic activity against spontaneous metastases which were induced by 3LL Lewis lung carcinoma cells. Moreover, 1a has the advantage of low toxicity, with an acute LD50 = 1.36 +/- 0.1 g/kg (n = 5). These results suggest that 1a is a potential antineoplastic agent.

All three receptors for vascular endothelial growth factor (VEGF) are expressed on B-chronic lymphocytic leukemia (CLL) cells.

B-chronic lymphocytic leukemia (B-CLL) cells have a long survival owing to an alteration in the normal pathways of apoptosis. CLL cells have been found to produce and secrete vascular endothelial growth factor (VEGF). In addition to its major role in angiogenesis, VEGF affects cell survival by interfering with apoptosis. The aim of the present study was to investigate the expression of the VEGF receptors VEGFR-1, VEGFR-2, and VEGFR-3 on B-CLL cells, singly and combined. B-CLL cells were isolated from peripheral blood drawn from patients with CLL. Total VEGF receptor, examined in 13 samples by flow cytometry was present in all cases with mean CD19+/VEGF+ expression of 76% (range 52-92%). Specific receptor expression, examined in 27 samples by immunocytochemical methods, was positive for VEGFR-1 in all 27 patients and for VEGFR-2 and VEGFR-3 in 26 (96%). These findings suggest that the VEGF transduction pathway may be very active in CLL cells, and both its paracrine and autocrine pathways may contribute to their enhanced survival.

Butyrate-induced differentiation in leukemic myeloid cells - in-vitro and in-vivo studies.

A study of the effects of three differentiating agents, butyric acid, retinoic acid and cytosine arabinoside on proliferation and differentiation of primary cultures, obtained from sixteen patients with myelo-proliferative disorder was conducted. The results showed that BA was an effective inhibitor of cell proliferation and inducer of cytodifferentiation. An acute non-lymphoblastic leukemia patient was treated with sodium butyrate. A temporary increase in differentiation-associated parameters were noted. However, the effects of SB were short-lived. The lack of clinical response led to the development of a BA prodrug pivaloyloxymethylbutyrate (AN-9). This prodrug was more potent in vitro than BA in the induction of cytodifferentiation and inhibition of cell proliferation.

Uptake of pivaloyloxymethyl butyrate into leukemic cells and its intracellular esterase-catalyzed hydrolysis.

UNLABELLED: Pivaloyloxymethyl butyrate (AN-9), a butyric acid (BA) prodrug, exhibited low toxicity and significant anticancer activity in vitro and in vivo. The purpose of this study was to elucidate the basis for AN-9 increased anticancer activity compared to BA, by studying the uptake of BA and AN-9 into the cells. METHODS: The uptake rate and level of [14C]-AN-9 and [14C]-BA, labeled on the carboxylic moiety of BA, into HL-60 and MEL leukemic cell lines was measured. The cells were filtered and the retained radioactivity was determined. The dependence of the uptake on the activity of cellular esterases and membrane fluidity was investigated. RESULTS: The uptake level in cells incubated with [14C]-AN-9 increased rapidly, peaked after 30 min in MEL and 1 h in HL-60 cells, and declined thereafter. This decline could be attributed to the hydrolysis of AN-9 by cellular esterases and catabolism of the released BA to CO2. In cells pretreated with an esterase inhibitor and incubated with [14C]-AN-9, the reduction of radioactivity was less precipitous. In cells exposed to [14C]-BA, the intracellular radioactivity level was low and unaffected by treatment with an esterase inhibitor. The uptake of [14C]-AN-9 decreased significantly at 4 degrees C compared to that at 37 degrees C. CONCLUSION: The higher potency of AN-9 compared to BA could be at least partially attributed to the more rapid uptake of the lipophilic AN-9 and the release of BA in the cells.

Effect of the cytostatic butyric acid pro-drug, pivaloyloxymethyl butyrate, on the tumorigenicity of cancer cells.

Previously we have shown that pivaloyloxymethyl butyrate (AN-9), a pro-drug of butyric acid (BA), is a differentiation-inducing agent in a variety of cells. In this report, we demonstrate that AN-9 is a cytostatic but not cytotoxic agent in a myelomonocytic cell line (WEHI); thus, the cells were growth-arrested and differentiated. These late changes in the cells were preceded by changes in the expression of the early regulatory genes, c-myc and c-jun. Although initiation of all these events had already occurred after 1 h exposure to AN-9, the tumorigenicity of these cells tested in Balb/c mice was not affected. A marked reduction in the tumorigenicity of AN-9-treated cells was observed after 4 h of exposure. Exposure of the highly metastatic subclone of Lewis lung carcinoma (3LLD122) to AN-9 resulted in a very pronounced effect on the tumorigenicity of these cells tested in C57BL mice. Unlike WEHI cells, the tumorigenicity of 3LLD122 was almost completely diminished after 1 h of exposure. In both cell types a 10-fold higher concentration of BA did not affect the tumorigenicity of the cells as did AN-9.

Microvessel density in chemosensitive and chemoresistant diffuse large B-cell lymphomas.

Preliminary reports involving a number of different kinds of tumors have indicated that microvessel quantification may be useful in predicting disease outcome. The aim of this study was to examine the relationship between microvessel density (MVD) as a parameter of tumor angiogenesis and the response to chemotherapy in diffuse large B-cell (DLBC) lymphomas. A total of 36 DLBC lymphoma patients were evaluated, 23 of them with a chemosensitive; responsive disease (median survival 8y) and 13 with a chemoresistant, refractory disease (median survival 8 months). Microvessel quantification was performed by immunohistochemical staining, using monoclonal antibodies against factor VIII related antigen (F8RA) and against platelet/endothelial cell adhesion molecule-CD31. We found that F8RA stained a significantly higher number of blood vessels (about 2.5 times more) than CD-31; 7 samples were not stained with CD-31 but were positive for F8RA. There was no significant difference between the density of microvessel staining of the two groups. In the chemosensitive DLBC lymphomas positive for F8RA, the mean number of microvessels stained was 54.5 +/- 36.1 per microscopic field (200x) examined (range 6-149) whereas in the chemoresistant group the corresponding mean number was 43.1 +/- 25.5 (range 11-94). F8RA appears to be more sensitive for staining DLBC lymphomas microvessels than CD-31. Our data demonstrate that there is no correlation between tumor MVD and response to chemotherapy in patients with DLBC lymphomas.

A family with hereditary thrombocythaemia and normal genes for thrombopoietin and c-Mpl.

Hereditary thrombocythaemia (HT) is an inherited autosomal dominant disorder. Recent studies reported six different mutations, four within the thrombopoietin (TPO) gene and two within c-Mpl (TPO receptor) gene in six unrelated families with HT. This study investigated the molecular basis of hereditary thrombocythaemia in an Israeli-Jewish family. We screened the genes for TPO and c-Mpl by amplification and sequencing of all the corresponding exons including exon/intron boundaries and promoters. In addition, plasma levels of TPO and erythropoietin (EPO) were measured. No abnormality in the TPO/c-Mpl genes has been identified in affected HT family members. Plasma TPO and EPO levels were found to be normal/low or normal respectively in the individuals affected. In conclusion, lack of a molecular lesion within either TPO or cMpl genes indicate that HT may be caused by factors other than TPO-cMpl axis in this family.

Disintegration of red cell membrane cytoskeleton by hemin.

Spectrin and actin were isolated and their oligomeric state after association with hemin at various conditions was studied. Intact cytoskeletons were prepared by Triton X-100 extraction of red blood cells and incubated with hemin and their stability analyzed by the appearance of dissociated proteins in the supernatant. The cytoskeletons dissociated in a time, temperature and hemin concentration-dependent manner. Following 18 hours incubation in the presence of 0.3 mM hemin there was no dissociation at 4 degrees C, while at the same hemin concentration after 2 hours complete dissociation of the cytoskeletons occurred at 37 degrees C. Microscopy indicated that the cytoskeletons incubated with hemin lost their "cell like" shapes in a time dependent manner. Hemin applied to intact cells also caused dissociation of their cytoskeletons as judged by the failure to separate integer cytoskeletons from red cells treated with hemin. From hemin-induced dissociation profiles of separated actin, spectrin and whole cytoskeletons under various conditions, a mechanism of cytoskeleton breakdown was analyzed, as a release of band 4.1 in the first step which is followed by spectrin dimerization and eventually dissociation of the entire cytoskeletons.

Proliferation-associated changes of Ca2+ transport in myeloid leukemic cell lines.

Proliferation-associated changes in calcium metabolism were investigated employing the promyelocytic HL-60 and monoblastic U-937 cell lines. The cells were stimulated to proliferate employing mitogenic factors as follows. 1) Transferrin or insulin: HL-60 cells were adjusted for growth in serum-free medium, and 24 h prior to the experiment, the cells were deprived of transferrin or insulin. The re-addition of either one of them stimulated cell proliferation as was evident by increased [3H]-tymidine incorporation activity. Cell proliferation was associated with an enhanced Ca2+ influx rate, measured by 45Ca2+ uptake activity. 2) Granulocyte-monocyte colony-stimulating factor (GM-CSF): addition of GM-CSF to proliferating or quiescent HL-60 cells resulted in increased cell proliferation, which was also accompanied by increased rate of Ca2+ influx. 3) Serum: HL-60 and U-937 were grown for 24 h in serum-depleted medium. Re-addition of serum to the cells was not associated with immediate or delayed change in calcium influx rate but rather with an immediate increase in the cytosolic free calcium concentration, measured employing the fluorescent probe, fura-2AM. This increase was independent of extracellular calcium, unaffected by verapamil, diltiazem, and lanthanum, and associated with enhanced 45Ca2+ efflux. Thus, in all three cases evoked cell proliferation was accompanied by quantitative changes in Ca2+ metabolism. While the transferrin-, insulin-, and GM-CSF-stimulated cell proliferation was accompanied by delayed increases in 45Ca2+ influx, the serum-stimulated cell proliferation was accompanied by an immediate elevation of free cytosolic Ca2+.

Bcl-2 expression correlates positively with serum basic fibroblast growth factor (bFGF) and negatively with cellular vascular endothelial growth factor (VEGF) in patients with chronic lymphocytic leukaemia.

A large proportion of B-chronic lymphocytic leukaemia (B-CLL) cells express the anti-apoptotic protein Bcl-2. Basic fibroblast growth factor (bFGF) has been shown to upregulate the expression of Bcl-2 in B-CLL cell lines. Vascular endothelial growth factor (VEGF) has been shown to enhance the survival of endothelial cells by upregulating the expression of Bcl-2. In the present study, we measured serum and cellular levels of bFGF and VEGF in 85 patients with CLL using a commercial quantitative sandwich enzyme immunoassay technique. Levels of Bcl-2 were also assayed concomitantly using Western blot analysis. The mean serum level of bFGF was 53.4 pg/ml (range 0-589) and that of VEGF 459.2 pg/ml (range 33-1793). The mean cellular level of bFGF was 158.3 pg/2 x 105 cells (range 0.8-841) and VEGF, 42.4 pg/2 x 105 cells (range 0-244). A high correlation was found between serum and cellular bFGF levels (P < 0.001), but not between the corresponding VEGF levels. Twenty-nine of 69 patients (42%) evaluated for Bcl-2 level, expressed it. The Bcl-2 level was positively correlated with the serum bFGF level (P = 0.007). However, surprisingly there was a negative correlation between Bcl-2 expression and intracellular VEGF level (P = 0.003). A positive correlation was also found between serum bFGF and disease follow-up time and log white blood cell count. These findings indicate that in CLL there is a correlation between angiogenesis-related factors and apoptosis-related protein expression, and elevated bFGF levels may account for the elevated Bcl-2 levels.

Interaction of spectrin with hemin disaggregates spectrin associations.

Crude spectrin preparations were extracted from red cell membranes either in dimeric or tetrameric forms and incubated at 4 degrees C with hemin. The mixtures were subjected immediately or after 18 hours to nondenaturing electrophoresis. It was found that immediately after addition of 0.3 mM hemin, the fraction of spectrin complexed with other skeletal proteins, disaggregated to tetramer and dimer forms. After incubation for 18 hours at 4 degrees C most of the spectrin appeared in two additional bands which contained more hemin and migrated on the gels as molecular weight forms smaller than the dimers. Since SDS electrophoresis showed that spectrin subunits retained their integrity in these mixtures, it was concluded that hemin bound spectrin dissociates with time into monomers. It is suggested that there are pathophysiological implications to the disaggregation of spectrin complexes in the cytoskeleton by hemin.

Esterase inhibitors diminish the modulation of gene expression by butyric acid derivative, pivaloyloxymethyl butyrate (AN-9).

Pivaloyloxymethyl butyrate (AN-9) belongs to the family of acyloxyalkyl ester prodrugs of carboxylic acids which undergo intracellular hydrolysis to yield butyric acid (BA). We have previously shown that AN-9 and BA reduce the level of c-myc and enhance c-jun transcripts in HL-60 cells, and that the differentiation of these cells, induced by AN-9, is dependent on the presence of intracellular esterases. In this study we show that esterase inhibitors abolish the changes induced by AN-9 on c-myc and c-jun expression. In contrast, esterase inhibitors do not change the effects of BA on c-myc or c-jun. Interestingly, these inhibitors affect the modulation induced by both AN-9 and BA on the retinoblastoma tumor suppressor gene. These data suggest that AN-9 is indeed a prodrug of BA and that prior intracellular hydrolysis by esterases is material for AN-9 activity.

The role of calcium in differentiation of leukemic cell lines.

Increased calcium influx associated with differentiation of four human myeloid leukemic cell lines: HL-60, KG-1, U-937 and K-562, to either monocytic or granulocytic direction was demonstrated. Calcium influx was measured employing two methods; measurement of radioactive calcium influx rate at 4 degrees C and employing the fluorescent probe, fura-2 acetoxymethyl ester. The increase in Ca2+ influx was demonstrated with three chemically unrelated differentiation inducers: retinoic acid, 1 alpha, 25 dihydroxy vitamin D3 and dimethyl sulfoxide. Inhibitors of calcium uptake such as verapamil diltiazem and cromolyn, partially reduced differentiation, suggesting that differentiation of myeloid leukemic cell lines is dependent on the availability of extracellular calcium.

Derivatives of butyric acid as potential anti-neoplastic agents.

A novel derivative of butyric acid, pivalyloxymethyl butyrate (AN-9) has been shown, in vitro, to: (a) induce cytodifferentiation and inhibit the proliferation of leukemic cells; (b) inhibit the growth and formation of Lewis lung carcinoma colonies in semi-solid agar. AN-9 affect cells at about 10-fold lower concentration and at a faster rate than does butyric acid. The pivalyloxymethyl esters of propionic, isobutyric and valeric acids do not elicit effects similar to those of AN-9, while the isobutyryloxymethyl butyrate does, which strongly suggests that the activity of AN-9 stems from intracellular metabolic degradation of the pro-drug to butyric acid. In vivo, AN-9, increased the survival of mice in Lewis lung carcinoma primary cancer model and significantly decreased the number of lung lesions of the animals inoculated with highly metastatic cells, but did not affect their life span. Acute LD50 studies have shown that AN-9 possesses low toxicity. These results suggest that AN-9 is a potential anti-neoplastic agent as well as a tool for investigation of the differentiation induction mechanism.