Biotherapy of B-cell precursor leukemia by targeting genistein to CD19-associated tyrosine kinases

Implications for Src kinases in hematopoiesis: signal transduction therapeutics

Signal transduction therapeutics is now the dominant theme of drug discovery, and its most immediate impact will be in cancer therapeutics. Blood cell proliferation, differentiation, and activation are controlled by cytokines, whose receptors contain tyrosine kinase catalytic domains or recruit cytosolic tyrosine kinases. Among the most important cytosolic protein tyrosine kinases are the Src and Jak families. Receptor or cytosolic protein tyrosine kinases activate a similar set of intracellular signaling molecules. In blood cells, excessive tyrosine kinase activity is associated with either cancer or autoreactive diseases. Therefore, tyrosine kinases and their substrates serve as excellent candidates for drug intervention. Herceptin has been approved for use in breast cancer. Other agents, such as SU101 and CGP 57418B, are well into phase I-III trials. Newer, more selective tyrosine kinase inhibitors are being evaluated for future use in the treatment of hematologic and solid tumors as well as a wide range of inflammatory or autoimmune diseases.

Targeting Janus kinase 3 in mast cells prevents immediate hypersensitivity reactions and anaphylaxis

Janus kinase 3 (JAK3), a member of the Janus family protein-tyrosine kinases, is expressed in mast cells, and its enzymatic activity is enhanced by IgE receptor/FcepsilonRI cross-linking. Selective inhibition of JAK3 in mast cells with 4-(4'-hydroxylphenyl)-amino-6, 7-dimethoxyquinazoline) (WHI-P131) blocked the phospholipase C activation, calcium mobilization, and activation of microtubule-associated protein kinase after lgE receptor/FcepsilonRI cross-linking. Treatment of IgE-sensitized rodent as well as human mast cells with WHI-P131 effectively inhibited the activation-associated morphological changes, degranulation, and proinflammatory mediator release after specific antigen challenge without affecting the functional integrity of the distal secretory machinery. In vivo administration of the JAK3 inhibitor WHI-P131 prevented mast cell degranulation and development of cutaneous as well as systemic fatal anaphylaxis in mice at nontoxic dose levels. Thus, JAK3 plays a pivotal role in IgE receptor/FcepsilonRI-mediated mast cell responses, and targeting JAK3 with a specific inhibitor, such as WHI-P131, may provide the basis for new and effective treatment as well as prevention programs for mast cell-mediated allergic reactions.

Growth stimulation by serum in Entamoeba histolytica is associated with protein tyrosine dephosphorylation

Very little protein tyrosine phosphorylation was observed in growing (exponential-phase) Entamoeba histolytica cells by immunoblotting and quantitative immunofluorescence. After 1 h of serum deprivation, two proteins (42 and 38 kDa in SDS-PAGE) were tyrosine phosphorylated and two more proteins (96 and 63 kDa) also showed tyrosine phosphorylation when examined after 4 h of serum deprivation. Intense enhancements of anti-phosphotyrosine immunofluorescence levels were observed during this period of serum withdrawal. Membrane-associated tyrosine kinase activity reached a peak (3.5-fold increase) 1 h after serum deprivation and decreased thereafter reaching a basal level by 2 h of serum deprivation. Interestingly, tyrosine kinase activities remained unaffected by serum stimulation (2-60 min) of serum-deprived cells. Also, during this period of serum stimulation tyrosine phosphorylated proteins of serum-deprived cells were dephosphorylated. Tyrosine phosphatase activities were suppressed during serum deprivation and on serum addition to serum-deprived cells tyrosine phosphatase activities increased significantly. Our data attest that protein tyrosine phosphorylation was associated with growth inhibition of E. histolytica and serum stimulation of E. histolytica produced tyrosine phosphatase activation and protein tyrosine dephosphorylation.

Phytoestrogens. State of the art

A short overview of recent advances of phytoestrogen research is presented. Developments have particularly been made with regard to methods, food analyses, pharmacokinetics, receptor studies, mechanisms of action and effects on cancer. Most studies deal with isoflavones, but the interest in lignans is increasing as a result of a large rye project in the Nordic countries. The development of rapid time-resolved immunofluorescence assays in 20 μl plasma samples for enterolactone, genistein and daidzein has resulted in the initiation of many prospective studies on cancer risk using blood bank material.

Induction of apoptosis in breast cancer cells MDA-MB-231 by genistein

Breast cancer is the most common cancer among American women, whereas Asian women, who consume a traditional diet high in soy products, have a relatively low incidence. Genistein is a prominent isoflavonoid in soy products and has been proposed as the agent responsible for lowering the rate of breast cancer in Asian women. We investigated the effects of genistein on cell growth and apoptosis-related gene expression in breast cancer cells MDA-MB-231. We found up-regulation of Bax and p21WAF1 expressions and down-regulation of Bcl-2 and p53 expression in genistein-treated cells. Furthermore, DNA ladder formation, CPP32 activation, and PARP cleavage were observed after treatment with genistein, indicating apoptotic cell deaths. Flow cytometry with 7-amino actinomycin D staining showed that the number of apoptotic cells increased with longer treatment of genistein. From these results, we conclude that genistein inhibits the growth of MDA-MB-231 breast cancer cells, regulates the expression of apoptosis-related genes, and induces apoptosis through a p53-independent pathway. The up-regulation of Bax and p21WAF1 may be the molecular mechanisms by which genistein induces apoptosis, however, further definitive studies are needed. These results suggest that genistein may be a potentially effective chemopreventive or therapeutic agent against breast cancer.

Genistein is neuroprotective in murine models of familial amyotrophic lateral sclerosis and stroke

Amyotrophic lateral sclerosis (ALS), whether sporadic or familial (FALS), is a progressive, fatal neurodegenerative disorder involving the motor neurons of the cortex, brain stem, and spinal cord. In some studies, the male/female ratio of ALS patients was as high as 2 to 1. In FALS mice, disease onset and mortality were earlier among males than among females. This sexual dimorphism was due to estrogen, as treatment with genistein, a phytoestrogen, eliminated the observed sexual dimorphism in FALS mice. Genistein treatment also protected against oxygen singlet-induced cerebral damage in vivo. However, sexual dimorphism was not observed in this model of stroke; and genistein was equally effective in males and females. These data suggest that genistein has both estrogen-dependent and estrogen-independent neuroprotective activities and it should be investigated as a prophylactic agent against pathologic conditions such as ALS and stroke.

Rational design and synthesis of a novel anti-leukemic agent targeting Bruton's tyrosine kinase (BTK), LFM-A13 [alpha-cyano-beta-hydroxy-beta-methyl-N-(2, 5-dibromophenyl)propenamide]

In a systematic effort to design potent inhibitors of the anti-apoptotic tyrosine kinase BTK (Bruton's tyrosine kinase) as anti-leukemic agents with apoptosis-promoting and chemosensitizing properties, we have constructed a three-dimensional homology model of the BTK kinase domain. Our modeling studies revealed a distinct rectangular binding pocket near the hinge region of the BTK kinase domain with Leu460, Tyr476, Arg525, and Asp539 residues occupying the corners of the rectangle. The dimensions of this rectangle are approximately 18 x 8 x 9 x 17 A, and the thickness of the pocket is approximately 7 A. Advanced docking procedures were employed for the rational design of leflunomide metabolite (LFM) analogs with a high likelihood to bind favorably to the catalytic site within the kinase domain of BTK. The lead compound LFM-A13, for which we calculated a Ki value of 1.4 microM, inhibited human BTK in vitro with an IC50 value of 17.2 +/- 0.8 microM. Similarly, LFM-A13 inhibited recombinant BTK expressed in a baculovirus expression vector system with an IC50 value of 2.5 microM. The energetically favorable position of LFM-A13 in the binding pocket is such that its aromatic ring is close to Tyr476, and its substituent group is sandwiched between residues Arg525 and Asp539. In addition, LFM-A13 is capable of favorable hydrogen bonding interactions with BTK via Asp539 and Arg525 residues. Besides its remarkable potency in BTK kinase assays, LFM-A13 was also discovered to be a highly specific inhibitor of BTK. Even at concentrations as high as 100 micrograms/ml (approximately 278 microM), this novel inhibitor did not affect the enzymatic activity of other protein tyrosine kinases, including JAK1, JAK3, HCK, epidermal growth factor receptor kinase, and insulin receptor kinase. In accordance with the anti-apoptotic function of BTK, treatment of BTK+ B-lineage leukemic cells with LFM-A13 enhanced their sensitivity to ceramide- or vincristine-induced apoptosis. To our knowledge, LFM-A13 is the first BTK-specific tyrosine kinase inhibitor and the first anti-leukemic agent targeting BTK.

Quantitative high-performance liquid chromatography-based detection method for calphostin C, a naturally occurring perylenequinone with potent antileukemic activity

Calphostin C is a potent inhibitor of protein kinase C and can induce Ca2+-dependent apoptosis in human ALL cells. Further development of calphostin C will require detailed pharmacodynamic studies in preclinical animal models. Therefore, we established a sensitive and accurate high-performance liquid chromatography (HPLC)-based quantitative detection method for the measurement of calphostin C levels in plasma. Extraction of calphostin C from plasma was performed by precipitation of plasma protein using acetonitrile and an aliquot of extracted supernatant was injected onto a Hewlett-Packard HPLC system constituting a 250x4 mm LiChrospher 100, RP-18 (5 microm) in conjunction with a 4x4 mm LiChrospher 100, RP-18 guard column (5 microm). The eluted compounds were detected by diode array detection set at a wavelength of 479 nm. Acetonitrile-water containing 0.1% trifluoroacetic acid and 0.1% triethylamine (70:30, v/v) was used as the mobile phase. The average extraction recovery from plasma was 97.3%. Good linearity (r>0.999) was observed throughout the concentration range of 0.05-40 microM for calphostin C in 50 microl of plasma. Intra- and inter-assay variabilities were less than 6% in plasma. The lowest detection limit of calphostin C in 50 microl plasma was 0.02 microM at a signal-to-noise ratio of approximately 3. The availability of this assay will now permit detailed pharmacodynamic and pharmacokinetic studies of calphostin C in vivo.

Poor treatment outcome of Philadelphia chromosome-positive pediatric acute lymphoblastic leukemia despite intensive chemotherapy

Children with Philadelphia (Ph) chromosome positive (+) acute lymphoblastic leukemia (ALL) represent a subgroup at very high risk for treatment failure. This study included 1322 children enrolled between 1988 and 1994 on CCG risk-adjusted studies for ALL who had centrally reviewed cytogenetic data. Thirty patients had a t(9;22) and are referred to as Ph+; 1292 were Ph-. 23 of these 30 patients were treated on the CCG-1882 high risk ALL protocol. The event-free survival (EFS) outcome in CCG-1882 was significantly worse for Ph+ compared with Ph- patients, with 4-year estimates of 11.3% (SD = 9.8%) and 73.4% (SD = 2.3%), respectively (p < 0.0001).

Isoflavone levels in soy foods consumed by multiethnic populations in Singapore and Hawaii

Concentrations and glucosidic conjugation patterns of isoflavones were determined in soy foods consumed by multiethnic populations in Singapore and Hawaii. Six raw and 11 cooked food groups traditionally consumed in Singapore and 8 food groups consumed in Hawaii were analyzed by reversed-phase high-pressure liquid chromatography with diode array detection. Mean total isoflavone levels varied between 35 and 7500 ppm, with the lowest values found in soy milk and burgers and the highest levels observed in soybean and its seeds and in supplements. Total isoflavone levels and conjugation patterns varied as a function of soybean variety, storage conditions, and food processing. A large contribution to the differences in total isoflavone content between food groups was due to the water content in foods and to leaching of polar analytes into the water phase during boiling. Soy protein drinks and traditional soy foods were found to possess very similar isoflavone amounts considering usual serving sizes.

Treatment outcome and prognostic factors for infants with acute lymphoblastic leukemia treated on two consecutive trials of the Children's Cancer Group

PURPOSE

Infants represent a very poor risk group for acute lymphoblastic leukemia (ALL). We report treatment outcome for such patients treated with intensive therapy on consecutive Children's Cancer Group (CCG) protocols.

PATIENTS AND METHODS

Between 1984 and 1993, infants with newly diagnosed ALL were enrolled onto CCG-107 (n = 99) and CCG-1883 (n = 135) protocols. Postconsolidation therapy was more intensive on CCG-1883. On both studies, prophylactic treatment of the CNS included both high-dose systemic chemotherapy and intrathecal therapy, in contrast to whole-brain radiotherapy, which was used in earlier studies.

RESULTS

Most patients (>95%) achieved remission with induction therapy. The most frequent event was a marrow relapse (46 patients on CCG-107 and 66 patients on CCG- 1883). Four-year event-free survival was 33% (SE = 4.7%) on CCG-107 and 39% (SE = 4.2%) on CCG- 1883. Both studies represent an improvement compared with a 22% (SE = 5.1%) event-free survival for historical controls. Four-year cumulative probabilities of any marrow relapse or an isolated CNS relapse were, respectively, 49% (SE = 5%) and 9% (SE = 3%) on CCG-107 and 50% (SE = 5%) and 3% (SE = 2%) on CCG-1883, compared with 63% (SE = 6%) and 5% (SE = 3%) for the historical controls. Independent adverse prognostic factors were age less than 3 months, WBC count of more than 50,000/microL, CD10 negativity, slow response to induction therapy, and presence of the translocation t(4;11).

CONCLUSION

Outcome for infants on CCG-107 and CCG- 1883 improved, compared with historical controls. Marrow relapse remains the primary mode of failure. Isolated CNS relapse rates are low, indicating that intrathecal chemotherapy combined with very-high-dose systemic therapy provides adequate protection of the CNS. The overall unsatisfactory outcome observed for the infant ALL population warrants the future use of novel alternative therapies.

Bruton's tyrosine kinase as an inhibitor of the Fas/CD95 death-inducing signaling complex

Bruton's tyrosine kinase (BTK) is a member of the Src-related Tec family of protein tyrosine kinases. Mutations in the btk gene have been linked to severe developmental blocks in human B-cell ontogeny leading to X-linked agammaglobulinemia. Here, we provide unique biochemical and genetic evidence that BTK is an inhibitor of the Fas/APO-1 death-inducing signaling complex in B-lineage lymphoid cells. The Src homology 2, pleckstrin homology (PH), and kinase domains of BTK are all individually important and apparently indispensable, but not sufficient, for its function as a negative regulator of Fas-mediated apoptosis. BTK associates with Fas via its kinase and PH domains and prevents the FAS-FADD interaction, which is essential for the recruitment and activation of FLICE by Fas during the apoptotic signal. Fas-resistant DT-40 lymphoma B-cells rendered BTK-deficient through targeted disruption of the btk gene by homologous recombination knockout underwent apoptosis after Fas ligation, but wild-type DT-40 cells or BTK-deficient DT-40 cells reconstituted with wild-type human btk gene did not. Introduction of an Src homology 2 domain, a PH domain, or a kinase domain mutant human btk gene into BTK-deficient cells did not restore the resistance to Fas-mediated apoptosis. Introduction of wild-type BTK protein by electroporation rendered BTK-deficient DT-40 cells resistant to the apoptotic effects of Fas ligation. BTK-deficient RAMOS-1 human Burkitt's leukemia cells underwent apoptosis after Fas ligation, whereas BTK-positive NALM-6-UM1 human B-cell precursor leukemia cells expressing similar levels of Fas did not. Treatment of the anti-Fas-resistant NALM-6-UM1 cells with the leflunomide metabolite analog alpha-cyano-beta-methyl-beta-hydroxy-N-(2, 5-dibromophenyl)propenamide, a potent inhibitor of BTK, abrogated the BTK-Fas association without affecting the expression levels of BTK or Fas and rendered them sensitive to Fas-mediated apoptosis. The ability of BTK to inhibit the pro-apoptotic effects of Fas ligation prompts the hypothesis that apoptosis of developing B-cell precursors during normal B-cell ontogeny may be reciprocally regulated by Fas and BTK.

Pharmacology of CFTR chloride channel activity

Pharmacology of CFTR Chloride Channel Activity. Physiol. Rev. 79, Suppl.: S109-S144, 1999. - The pharmacology of cystic fibrosis transmembrane conductance regulator (CFTR) is at an early stage of development. Here we attempt to review the status of those compounds that modulate the Cl- channel activity of CFTR. Three classes of compounds, the sulfonylureas, the disulfonic stilbenes, and the arylaminobenzoates, have been shown to directly interact with CFTR to cause channel blockade. Kinetic analysis has revealed the sulfonylureas and arylaminobenzoates interact with the open state of CFTR to cause blockade. Suggestive evidence indicates the disulfonic stilbenes act by a similar mechanism but only from the intracellular side of CFTR. Site-directed mutagenesis studies indicate the involvement of specific amino acid residues in the proposed transmembrane segment 6 for disulfonic stilbene blockade and segments 6 and 12 for arylaminobenzoate blockade. Unfortunately, these compounds (sulfonylureas, disulfonic stilbenes, arylaminobenzoate) also act at a number of other cellular sites that can indirectly alter the activity of CFTR or the transepithelial secretion of Cl-. The nonspecificity of these compounds has complicated the interpretation of results from cellular-based experiments. Compounds that increase the activity of CFTR include the alkylxanthines, phosphodiesterase inhibitors, phosphatase inhibitors, isoflavones and flavones, benzimidazolones, and psoralens. Channel activation can arise from the stimulation of the cAMP signal transduction cascade, the inhibition of inactivating enzymes (phosphodiesterases, phosphatases), as well as the direct binding to CFTR. However, in contrast to the compounds that block CFTR, a detailed understanding of how the above compounds increase the activity of CFTR has not yet emerged.

Soyfoods, isoflavones and risk of colonic cancer: a review of the in vitro and in vivo data

Soy foods and soybean components have received considerable attention of late for their potential role in reducing cancer risk. Although the relationship between soy intake and the risk of breast and prostate cancer has been the focus of most interest, the relationship between soy intake and other cancers, including colorectal cancer, has also been studied. Several anti-carcinogens have been identified in soybeans, but most enthusiasm for the potential anti-cancer effects of soy undoubtedly stems from work involving soybean isoflavones. Isoflavones have a limited distribution in nature, and, for practical purposes, soyfoods are the only nutritionally relevant dietary source of these phytochemicals. Isoflavones are weak oestrogens but possess other potentially important biological attributes independent of their ability to bind to the oestrogen receptor. The isoflavone genistein inhibits the growth of most types of hormone-dependent and hormone-independent cancer cells in vitro, including colonic cancer cells. Several mechanisms for the in vitro anti-cancer effects of genistein have been proposed, including effects on signal transduction. A number of epidemiological studies, primarily of Asian origin, have examined the relationship between soy intake and the risk of colorectal cancer. Although these studies provide little support for a protective effect of soy, concerns have been raised about the completeness of the soy intake data, since soy was not the focus of these studies and most of this research was conducted prior to the recent interest in the anti-cancer effects of soy. The effect of soy/isoflavone intake has also been studied in rodents, but again these data are conflicting and provide only modest support for a protective effect. Although the relationship between soy intake and colonic cancer risk is certainly worthy of further investigation, there is, at the moment, very limited support for soy exerting a protective effect against this type of cancer.

Genistein inactivates bcl-2, delays the G2/M phase of the cell cycle, and induces apoptosis of human breast adenocarcinoma MCF-7 cells

The aim of this study was to identify the molecular mechanism of action of the isoflavone, genistein. Genistein at 0.15 mM caused MCF-7 apoptotic cell death, which was accompanied by cell cycle delay in the G2/M phase. Twenty-four hours post-treatment, 47.3% of the MCF-7 cells accumulated at G2/M, compared with 19.9% in the untreated controls. At 0.15 mM, genistein caused an increase in the steady-state levels of the wild-type tumour suppressor p53, which was attributed to stabilising the tumour suppressor protein, since p53 mRNA levels did not increase. Prior to the upregulation of p53, which became evident within 6 h of genistein treatment, there was increased bcl-2 phosphorylation at 30 min post-treatment. Although early changes (30-120 min) in the phosphotyrosine peptide patterns were not detected, after 24h, genistein inhibited phosphorylation of several peptides. These results suggest that genistein's dual roles of protein tyrosine kinase inhibitor and topoisomerase II inhibitor are essential for the initiation of apoptosis.

An anti-CD19 antibody coupled to a tetanus toxin peptide induces efficient Fas ligand (FasL)-mediated cytotoxicity of a transformed human B cell line by specific CD4+ T cells

Treatment of B cell lymphoma patients with MoAbs specific for the common B cell marker (CD20) has shown a good overall response rate, but the number of complete remissions is still very low. The use of MoAbs coupled to radioisotopes can improve the results, but induces undesirable myelodepression. As an alternative, we proposed to combine the specificity of MoAbs with the immunogenicity of T cell epitopes. We have previously shown that an anti-Ig lambda MoAb coupled to an MHC class II-restricted universal T cell epitope peptide P2 derived from tetanus toxin induces efficient lysis of a human B cell lymphoma by a specific CD4+ T cell line. Here we demonstrate that the antigen presentation properties of the MoAb peptide conjugate are maintained using a MoAb directed against a common B cell marker, CD19, which is known to be co-internalized with the B cell immunoglobulin receptor. In addition, we provide evidence that B cell lysis is mediated by the Fas apoptosis pathway, since Fas (CD95), but not tumour necrosis factor receptor (TNFr) or TNF-related receptors, is expressed by the target B cells, and FasL, but not perforin, is expressed by the effector T cells. These results show that B cell lymphomas can be 'foreignized' by MoAb-peptide P2 conjugates directed against the common B cell marker CD19 and eliminated by peptide P2-specific CD4+ T cells, via the ubiquitous Fas receptor. This approach, which bridges the specificity of passive antibody therapy with an active T cell immune response, may be complementary to and more efficient than the present therapy results with unconjugated chimeric anti-CD20 MoAbs.

Prepubertal genistein treatment modulates TGF-alpha, EGF and EGF-receptor mRNAs and proteins in the rat mammary gland

We have previously demonstrated that exposure to genistein early in life protects against chemically-induced mammary cancer in rats. To gain insight into the mechanism of action, we have investigated the expression of the EGF-signaling pathway in the mammary glands of 21 and 50 day old rats treated on days 16, 18, and 20 postpartum with 500 microg genistein/g body weight (B.W.) or an equivalent volume of the vehicle, dimethylsulfoxide (DMSO). This prepubertal genistein treatment up-regulated TGF-alpha and the EGF-receptor (EGFR), but not EGF, in mammary terminal ductal structures at day 21 postpartum. TGF-alpha, EGF and EGFR mRNA levels were similar in 21 day old control- and genistein-treated animals. At day 50 postpartum, mammary glands of genistein treated rats had more lobules and fewer terminal end buds (TEBs) and terminal ducts (TDs), i.e. they were more differentiated. TGF-alpha mRNA levels were down-regulated in TEB of proestrous and estrous females; EGF mRNA levels were down-regulated in TDs of proestrous, but not in estrous females; and EGFR mRNA levels were not altered in 50 day old proestrous or estrous female rats. EGFR immunostaining intensity was decreased in TEBs, but not in the total gland. EGF was increased in TEBs and TDs. TGF-alpha, EGF and EGFR were also observed in the stroma and fat pad, but genistein treatment did not alter the expression of these proteins in those locations. TGF-alpha, but not EGF and EGFR, immunostaining was observed in cell nuclei (not modulated by genistein), suggesting that this growth factor may act directly on nuclear events such as transcription and DNA replication. For comparative purposes, prepubertal diethylstilbestrol treatment was investigated and found to decrease EGFR immunostaining intensity and total IHC staining in all terminal ductal structures. We conclude that prepubertal genistein treatment directly stimulates TGF-alpha and EGFR to enhance mammary gland differentiation. This programs the differentiated cells for a down-regulated EGF-signaling pathway in TEBs and TDs of adult mammary glands. Reduced EGFR expression at time of carcinogen exposure may account for genistein programming against mammary cancer.

Genistein, a component of soy, inhibits the expression of the EGF and ErbB2/Neu receptors in the rat dorsolateral prostate

BACKGROUND

Epidemiological reports suggest that Asians consuming a diet high in soy have a low incidence of prostate cancer. In animal models, soy and genistein have been demonstrated to suppress the development of prostate cancer. In this study, we investigate the mechanism of action, bioavailability, and potential for toxicity of dietary genistein in a rodent model.

METHODS

Lobund-Wistar rats were fed a 0.025-1.0-mg genistein/g AIN-76A diet. The dorsolateral prostate was subjected to Western blot analysis for expression of tyrosine-phosphorylated proteins, and of the EGF and ErbB2/Neu receptors. Genistein concentrations were measured from serum and prostate using HPLC-mass spectrometry. Body and prostate weights, and circulating testosterone levels, were measured.

RESULTS

Increasing concentrations of genistein in the diet inhibited tyrosine-phosphorylated proteins with molecular weights of 170,000 and 85,000 in the dorsolateral prostate. Western blot analysis revealed that the 1-mg genistein/g AIN-76A diet inhibited by 50% the expression of the EGF receptor and its phosphorylation. In rats fed this diet, serum-free and total genistein concentrations were 137 and 2,712 pmol/ml, respectively. The free and total genistein IC50 values for the EGF receptor were 150 and 600 pmol/g prostate tissue, respectively. Genistein in the diet also inhibited the ErbB2/Neu receptor. Body and dorsolateral prostate weights, and circulating testosterone concentrations, were not adversely effected from exposure to genistein in the diet for 3 weeks.

CONCLUSIONS

We conclude that genistein in the diet can downregulate the EGF and ErbB2/Neu receptors in the rat prostate with no apparent adverse toxicity to the host. The concentration needed to achieve a 50% reduction in EGF receptor expression can be achieved by eating a diet high in soy products or with genistein supplementation. Genistein inhibition of the EGF signaling pathway suggests that this phytoestrogen may be useful in both protecting against and treating prostate cancer.

Targeted superantigens for immunotherapy of haematopoietic tumours

With the exception of childhood common acute lymphoblastic leukaemia (cALL), treatment of other hematopoietic B cell lineage tumours such as non-Hodgkin's lymphoma (B-NHL), adult ALL and multiple myeloma (MM) is unsatisfactory. Similarly, the therapeutic outcome of acute and chronic myeloid leukaemia (AML, CML) is frequently dismal. At the same time, leukaemia/lymphoma cells represent ideal targets for immunotherapy. The present review summarizes our preclinical experience with a novel type of cytotoxic T cell based immunotherapy for B-lineage and myeloid tumours. Staphylococcal enterotoxin-derived superantigens (SAgs) are among the most potent T cell activators known, linking the T cell receptor to HLA-DR on natural target cells. SAgs were genetically engineered to reduce DR binding and were then fused to Fab parts of tumour-directed monoclonal antibodies (mAbs). Using these "targeted" SAgs, highly efficient lysis of B-lineage (B-NHL, B-CLL, ALL, MM) and myeloid (AML, CML) tumour cells by T-cells was achieved in vitro and in an animal model. We are entering an interesting era of innovative cancer therapy based on novel man-made biotherapeutic agents.

Role of tyrosine kinases in induction of the c-jun proto-oncogene in irradiated B-lineage lymphoid cells

Exposure of B-lineage lymphoid cells to ionizing radiation induces an elevation of c-jun proto-oncogene mRNA levels. This signal is abrogated by protein-tyrosine kinase (PTK) inhibitors, indicating that activation of an as yet unidentified PTK is mandatory for radiation-induced c-jun expression. Here, we provide experimental evidence that the cytoplasmic tyrosine kinases BTK, SYK, and LYN are not required for this signal. Lymphoma B-cells rendered deficient for LYN, SYK, or both by targeted gene disruption showed increased c-jun expression levels after radiation exposure, but the magnitude of the stimulation was lower than in wild-type cells. Thus, these PTKs may participate in the generation of an optimal signal. Notably, an inhibitor of JAK-3 (Janus family kinase-3) abrogated radiation-induced c-jun activation, prompting the hypothesis that a chicken homologue of JAK-3 may play a key role in initiation of the radiation-induced c-jun signal in B-lineage lymphoid cells.

Antiviral protection and germinal center formation, but impaired B cell memory in the absence of CD19

Coligation of CD19, a molecule expressed during all stages of B cell development except plasmacytes, lowers the threshold for B cell activation with anti-IgM by a factor of 100. The cytoplasmic tail of CD19 contains nine tyrosine residues as possible phosphorylation sites and is postulated to function as the signal transducing element for complement receptor (CR)2. Generation and analysis of CD19 gene-targeted mice revealed that T cell-dependent (TD) antibody responses to proteinaceous antigens were impaired, whereas those to T cell-independent (TI) type 2 antigens were normal or even augmented. These results are compatible with earlier complement depletion studies and the postulated function of CD19. To analyze the role of CD19 in antiviral antibody responses, we immunized CD19(-/-) mice with viral antigens of TI-1, TI-2, and TD type. The effect of CD19 on TI responses was more dependent on antigen dose and replicative capacity than on antigen type. CR blocking experiments confirmed the role of CD19 as B cell signal transducer for complement. In contrast to immunization with protein antigens, infection of CD19(-/-) mice with replicating virus led to generation of specific germinal centers, which persisted for >100 d, whereas maintenance of memory antibody titers as well as circulating memory B cells was fully dependent on CD19. Thus, our study confirms a costimulatory role of CD19 on B cells under limiting antigen conditions and indicates an important role for B cell memory.

Production of recombinant DTctGMCSF fusion toxin in a baculovirus expression vector system for biotherapy of GMCSF-receptor positive hematologic malignancies

The fusion toxin DTctGMCSF has been constructed by genetically replacing the native receptor-binding domain of diphtheria toxin (DT) with human granulocyte-macrophage colony stimulating factor (GMCSF). This recombinant fusion toxin preserves the catalytic (c) and membrane translocation (t) domains of DT and includes a sterically neutral peptide linker separating the toxin and growth factor domains. Previous work using DTctGMCSF produced in Escherichia coli has shown that this chimeric toxin is selectively cytotoxic to GMCSF receptor (R)-positive acute myeloid leukemia (AML) cells both in vitro and in vivo. Its clinical development has been hampered due to very low expression levels, requirements for solubilization with guanidine hydrochloride and subsequent refolding, and concerns about bacterial endotoxin contamination. These difficulties prompted us to investigate the utility of a baculovirus/insect cell expression system for the production of DTctGMCSF. Here, we report that a soluble form of DTctGMCSF can be produced in the baculovirus expression vector system (BEVS) and purified to homogeneity by column chromatography. The BEVS-derived DTctGMCSF fusion toxin caused apoptotic death in GMCSF-R-positive human AML cells at nanomolar concentrations. In contrast to the 100 microg/L yields of purified DTctGMCSF obtained from E. coli, the BEVS allows us to routinely generate 8-10 mg/L of purified DTctGMCSF. This increased capacity provided by the BEVS for the production of DTctGMCSF makes it now possible to obtain sufficient quantities to carry out preclinical and clinical trials. To our knowledge, this is the first report of the successful utilization of the BEVS for producing a therapeutic fusion toxin.

In vivo toxicity and pharmacokinetic features of B43(Anti-CD19)-Genistein immunoconjugate

B43(anti-CD19)-Genistein immunoconjugate targets genistein, a naturally occurring protein tyrosine kinase inhibitory isoflavone to the membrane-associated anti-apoptotic CD19-LYN complexes and triggers apoptotic cell death. In this preclinical study, the toxicity profiles of B43-Genistein as well as unconjugated genistein were evaluated in mice. B43-Genistein and genistein were administered either as single bolus injections or daily injections for 10 consecutive days via the intraperitoneal route to mice. Genistein was not toxic to mice at the highest dose of 40 mg/kg and no test article-related histopathological lesions were found in any of the 64 genistein-treated mice. B43-Genistein had a significantly longer elimination half-life and slower plasma and tissue clearance than unconjugated genistein. B43-Genistein was not toxic to mice at the highest single dose of 40 mg/kg or highest cumulative dose of 100 mg/kg and no test article-related histopathological lesions were found in any of the 108 mice treated with B43-genistein. To our knowledge, this is the first preclinical toxicity and pharmacokinetic study of a tyrosine kinase inhibitor-containing immunoconjugate.

The Croonian Lecture 1997. The phosphorylation of proteins on tyrosine: its role in cell growth and disease

The reversible phosphorylation of tyrosines in proteins plays a key role in regulating many different processes in eukaryotic organisms, such as growth control, cell cycle control, differentiation cell shape and movement, gene transcription, synaptic transmission, and insulin action. Phosphorylation of proteins is brought about by enzymes called protein-tyrosine kinases that add phosphate to specific tyrosines in target proteins; phosphate is removed from phosphorylated tyrosines by enzymes called protein-tyrosine phosphatases. Phosphorylated tyrosines are recognized by specialized binding domains on other proteins, and such interactions are used to initiate intracellular signaling pathways. Currently, more than 95 protein-tyrosine kinases and more than 55 protein-tyrosine phosphatase genes are known in Homo sapiens. Aberrant tyrosine phosphorylation is a hallmark of many types of cancer and other human diseases. Drugs are being developed that antagonize the responsible protein-tyrosine kinases and phosphatases in order to combat these diseases.

Large scale manufacturing of B43(anti-CD19)-genistein for clinical trials in leukemia and lymphoma

We have conjugated the murine monoclonal anti-CD19 antibody B43 to the tyrosine kinase inhibitor genistein to construct an effective immunoconjugate against CD19 antigen positive hematologic malignancies. The scaled-up production and purification of B43 antibody, genistein, and B43-Genistein immunoconjugate permitted the manufacturing of a highly purified clinical-grade B43-Genistein preparation. In clonogenic assays, B43-Genistein elicited selective and potent cytotoxicity against CD19 antigen positive human leukemia cells. To our knowledge, this work represents the first effort of producing a clinical-grade genistein immunoconjugate for treatment of B-lineage leukemia and lymphoma.

Mechanism for the suppression of the mammalian stress response by genistein, an anticancer phytoestrogen from soy

BACKGROUND

Soy products contain high levels of genistein, a phytoestrogen that is a potent inhibitor of cell proliferation and angiogenesis. Genistein has been found to inhibit the growth of carcinogen-induced cancers in rats and human leukemia cells transplanted into mice. The induction of stress proteins (e.g., glucose-related proteins and heat shock proteins) in tumor cells has been shown to protect them against programmed cell death; this stress response is inhibited by genistein. The mechanism(s) by which genistein affects certain stress response genes was explored in this study.

METHODS

Mammalian cell cultures were treated with azetidine, a proline analog, which elicits a stress response that includes the induction of the expression of glucose-regulated protein GRP78 and heat shock protein HSP70. The effects of azetidine and/or genistein treatment on cellular levels of grp78 and hsp70 messenger RNAs and proteins were measured by northern blot hybridization and western blot analyses, respectively, and the binding of nuclear factors to sequence motifs in the upstream (promoter) regions of these two genes were examined by electrophoretic mobility shift assays.

RESULTS

Genistein antagonized the binding of a specific transcription factor, nuclear factor-Y/CCAAT binding factor (NF-Y/CBF), to the CCAAT sequence element most proximal to the transcription start sites in the hsp70 and grp78 promoters; this CCAAT element was previously shown to be necessary for full-stress inducibility of both genes. Treatment of cells with genistein converted NF-Y/CBF into a nonbinding, transcriptionally inactive form.

IMPLICATION

The anticancer effects of genistein may be related to its ability to reduce the expression of stress response-related genes.

Stimulation of Src family protein-tyrosine kinases as a proximal and mandatory step for SYK kinase-dependent phospholipase Cgamma2 activation in lymphoma B cells exposed to low energy electromagnetic fields

Here, we present evidence that exposure of DT40 lymphoma B cells to low energy electromagnetic field (EMF) results in a tyrosine kinase-dependent activation of phospholipase Cgamma2 (PLC-gamma2) leading to increased inositol phospholipid turnover. B cells rendered PLC-gamma2-deficient by targeted disruption of the PLC-gamma2 gene as well as PLC-gamma2-deficient cells reconstituted with Src homology domain 2 (SH2) domain mutant PLC-gamma2 did not show any increase in inositol-1,4,5-trisphosphate levels after EMF exposure, providing direct evidence that PLC-gamma2 is responsible for EMF-induced stimulation of inositol phospholipid turnover, and its SH2 domains are essential for this function. B cells rendered SYK-deficient by targeted disruption of the syk gene did not show PLC-gamma2 activation in response to EMF exposure. The C-terminal SH2 domain of SYK kinase is essential for its ability to activate PLC-gamma2. SYK-deficient cells reconstituted with a C-terminal SH2 domain mutant syk gene failed to elicit increased inositol phospholipid turnover after EMF exposure, whereas SYK-deficient cells reconstituted with an N-terminal SH2 domain mutant syk gene showed a normal EMF response. LYN kinase is essential for the initiation of this biochemical signaling cascade. Lymphoma B cells rendered LYN-deficient through targeted disruption of the lyn gene did not elicit enhanced inositol phospholipid turnover after EMF exposure. Introduction of the wild-type (but not a kinase domain mutant) mouse fyn gene into LYN-deficient B cells restored their EMF responsiveness. B cells reconstituted with a SH2 domain mutant fyn gene showed a normal EMF response, whereas no increase in inositol phospholipid turnover in response to EMF was noticed in LYN-deficient cells reconstituted with a SH3 domain mutant fyn gene. Taken together, these results indicate that EMF-induced PLC-gamma2 activation is mediated by LYN-regulated stimulation of SYK, which acts downstream of LYN kinase and upstream of PLC-gamma2.

Salidiuretic action by genistein in the isolated, perfused rat kidney

The urinary isoflavonoid genistein inhibits membrane Na-K-Cl cotransporters at similar concentrations as furosemide, but the significance of this action is unknown. Genistein was therefore investigated in rats for its potential salidiuretic actions. In the isolated, perfused rat kidney, genistein induced a maximal salidiuretic action similar to that of furosemide but was 3 to 5 times less potent than furosemide in terms of active doses (natriuresis EC50, 237+/-92 versus 56+/-20 micromol/L for genistein and furosemide, respectively). Genistein and furosemide had no additive salidiuretic actions. Genistein had no significant effect on glomerular filtration rate but was able to significantly reduce renal vascular resistance with respect to vehicle isolated perfused kidney. Indomethacin (10 micromol/L), a blocker of prostaglandin biosynthesis, reduced salidiuresis and renal vasorelaxation by genistein. Subcutaneous genistein (15 mg/kg) induced a statistically significant increase in diuresis and natriuresis with respect to vehicle during the first 6 hours of administration in rats. In conclusion, genistein compares well with furosemide in vitro for its salidiuretic profile and potency in the isolated perfused rat kidney and is also natriuretic by the subcutaneous route in the rat. Further studies are required to investigate potential natriuretic and perhaps hypotensive actions of dietary genistein.

Derivatives of gallic acid induce apoptosis in tumoral cell lines and inhibit lymphocyte proliferation

The effect of gallic acid (3,4,5-trihydroxybenzoic acid) and its alkyl esters (methyl, propyl, octyl, and lauryl) has been studied on several tumoral and nontumoral cells. Three types of behavior have been observed; the first type is represented by the mouse B cell lymphoma Wehi 231 cell line in which death occurs according to the biochemical characteristics of classical apoptosis showing the DNA ladder fragmentation pattern. The second type is represented by the mouse fibroblast L929 cell line in which morphological characteristics such as cell shrinkage, chromatin condensation, and appearance of apoptotic bodies can be evidenced by microscopical observation. However, the typical DNA fragmentation is absent. Peripheral blood lymphocytes are representative of a third type of behavior. In a resting state they can withstand higher concentrations of these compounds. If the drug is washed, they proliferate normally upon the addition of the mitogen phytohemagglutinin (PHA). However, if the drug is added in the presence of PHA, a clear antiproliferative effect can be demonstrated. A special interest for these compounds stems from the fact that some of them are currently used as antioxidant food additives with the European Community codes E-310 (propylgallate), E-311 (octylgallate), and E-312 (laurylgallate).

The potential for immunoconjugates in lymphoma therapy

Contemporary combination chemotherapy offers curative treatment for 30% to 50% of patients with advanced-stage, aggressive non-Hodgkin's lymphomas (NHL). However, conventional therapies cure few patients with indolent lymphomas or relapsed lymphomas of any histology. Myeloablative chemoradiotherapy with bone marrow or stem cell transplantation can provide pro-longed disease-free survival for a minority (20% to 50%) of patients with relapsed NHL, but new treatment approaches are clearly needed. In recent years, several groups of investigators have provided preliminary evidence suggesting that monoclonal antibodies (mAbs), in unmodified form or conjugated to toxins, drugs, or radioisotopes, may offer another effective therapeutic modality for patients with relapsed lymphomas. This article reviews current immunotherapy of NHL using antibody immunoconjugates.

Apoptosis and acute lymphocytic leukemia in children

We examined in vivo spontaneous and prednisolone-induced apoptosis in peripheral blood samples of 23 children with ALL by flow cytometric and morphologic methods. There was no significant spontaneous apoptosis before the therapy. Six hours after prednisolone therapy, increased apoptosis was found in 19 of 23 cases. In one case, the apoptosis of blast cells could not be compared with the clinical data, because the patient died in sepsis during the induction therapy. In 18 of 22 evaluable cases, the in vivo apoptosis correlated with the decrease of leukemic blasts during the first 8 days of prednisolone monotherapy. In 20 of 22 children, a correlation was found between in vivo prednisolone-induced apoptosis and clinical outcome. The p53 gene expression was elevated in 2 of 10 patients. No elevation in the expression of bcl-2 gene was observed. In 6 of 23 cases, the glucocorticoid receptors were measured. The correlation of clinical responsiveness and gcR mRNA shows less parallelism than does the apoptosis correlation.

Partially purified soy hydrolysates retard proliferation and inhibit bacterial translocation in cultured C2BBe cells

Hydrolyzed soybean isolates SP-A and SP-B (Abbott Laboratories, OH), developed for use in enteral nutritional products, were tested in cultures of C2BBe cells, a colonic adenocarcinoma cell line with enterocytic differentiation, to evaluate effects on cell growth, maturation and ability to resist infection by enteric bacteria. SP-A delayed formation of confluent monolayers by 10 d compared with cells cultured without SP-A. SP-A also caused a retardation in the development of intercellular tight junctions as measured by transmonolayer electrical resistance (TER). SP-B had no effect on cell proliferation or TER of intestinal cell cultures. SP-A and SP-B enhanced the development of the brush border enzymes alkaline phosphatase and isomaltase over a 28 d period. By these criteria, SP-A and SP-B appear to affect intestinal epithelial cell development in culture. When C2BBe monolayers were exposed to the enteric bacteria, Salmonella typhimurium or Salmonella typhi, an inhibition of the passage of S. typhi was seen in cultures with SP-A and SP-B. No effect on the passage of S. typhimurium was seen with either soy isolate. Partially purified soy isolates therefore impart resistance to selected enteroinvasive bacteria. Addition of soy hydrolysates to the media of cultured intestinal cells may serve as a rapid and economical screening mechanism for preclinical trials that would test the therapeutic benefits of soybean isolates.

Phosphotyrosyl proteins in childhood rhabdomyosarcomas: phosphorylation of catenins and components of the insulin-like growth factor type I receptor signaling cascade

PURPOSE

Rhabdomyosarcomas (RMS) are heterogeneous in their clinical presentation, histology, and cytogenetics. The growth of some RMS cells has been found to be regulated by the tyrosine kinase insulin-like growth factor (IGF) type I receptor. However, RMS cells exhibit variable sensitivity to inhibitors of tyrosine kinases and IGF receptors. Collectively, these heterogeneous features suggest that differences exist in the growth regulatory pathways of RMS. The objective of this study is to identify active tyrosine kinase signal transduction pathways in embryonal and alveolar RMS cells.

METHODS

RMS tumor samples and cell lines representing both embryonal and alveolar histologic subtypes have been analyzed by immunoprecipitation and immunoblotting techniques to characterize phosphotyrosyl protein patterns and to identify tyrosine phosphorylated proteins.

RESULTS

RMS cells can be characterized based on the patterns of phosphotyrosyl proteins, including the phosphorylation status of the catenin-like protein Cas1 and the signal adapter protein SHC, and the activation of IGF type I receptor signaling cascades including the formation of SHC-GRB2 signal protein complexes and MAP kinase activation.

CONCLUSIONS

Rhabdomyosarcomas, especially the embryonal histologic subtype, are heterogeneous at the level of tyrosine kinase signal transduction. It will be important to characterize the growth regulatory pathways active in individual RMS tumors before targeting molecular therapies to this malignancy.

Intestinal uptake and biliary excretion of the isoflavone genistein in rats

The intestinal absorption, biliary excretion and metabolism of genistein, a potent and specific protein tyrosine kinase inhibitor that occurs naturally in soy foods, was examined in anesthetized, adult female rats fitted with indwelling biliary cannulas. 4-14C-Genistein, when infused into the duodenum, was rapidly absorbed from the intestine, taken up by the liver and excreted into the bile as its 7-O-beta-glucuronide conjugate. Cumulative recovery of 14C-radioactivity in the bile over a 4-h period was 70-75% of the dose. When genistein was infused into the portal vein, it was also taken up efficiently by the liver, conjugated with glucuronic acid and transported into bile. However, portal blood collected after duodenal infusions of genistein contained mostly genistein 7-O-beta-glucuronide, suggesting that in vivo glucuronidation occurred in the intestinal wall rather than the liver. This was confirmed using everted intestinal sac preparations. Reinfusion of genistein 7-O-beta-glucuronide into the duodenum or into the mid small intestine resulted in its reappearance in the bile, albeit more slowly than when genistein was infused. Over a 4-h collection period, the cumulative recovery of 14C-radioactivity in bile was 27 and 70-75% of the administered dose for duodenal and ileal infusions, respectively. These data indicate that genistein is highly bioavailable in rats and because of its enterohepatic circulation may accumulate within the gastrointestinal tract.

Targeting signal transduction for disease therapy

With the advance in the molecular understanding of cancers and proliferative disorders new approaches to managing these diseases may become feasible. It has been recognized that a key feature of these diseases is the pathological alteration in the molecular machineries of signalling pathways. This recognition which began to emerge in the early 1980s induced us to explore the possibility of targetting the aberrant signalling pathways for disease therapy. I now present evidence for the validity of the approach.

Cellular Expression of Antiapoptotic BCL-2 Oncoprotein in Newly Diagnosed Childhood Acute Lymphoblastic Leukemia: A Children's Cancer Group Study

We found a marked variation in BCL-2 oncoprotein expression levels of primary leukemic cells from 338 children with newly diagnosed acute lymphoblastic leukemia (ALL). None of the high-risk features predictive of poor treatment outcome in childhood ALL, such as older age, high white blood cell (WBC) count, organomegaly, T-lineage immunophenotype, ability of leukemic cells to cause overt leukemia in severe combined immunodeficient (SCID) mice, presence of MLL-AF4, and BCR-ABL fusion transcripts were associated with high levels of BCL-2 expression. Overall, high BCL-2 levels were not associated with slow early response, failure to achieve complete remission, or poor event-free survival. High BCL-2 levels in primary leukemic cells predicted slow early response only in T-lineage ALL patients, which comprised approximately 15% of the total patient population. Even for this small subset of patients, the level of BCL-2 expression did not have a significant impact on the short-term event-free survival.

Cellular Expression of Antiapoptotic BCL-2 Oncoprotein in Newly Diagnosed Childhood Acute Lymphoblastic Leukemia: A Children's Cancer Group Study

We found a marked variation in BCL-2 oncoprotein expression levels of primary leukemic cells from 338 children with newly diagnosed acute lymphoblastic leukemia (ALL). None of the high-risk features predictive of poor treatment outcome in childhood ALL, such as older age, high white blood cell (WBC) count, organomegaly, T-lineage immunophenotype, ability of leukemic cells to cause overt leukemia in severe combined immunodeficient (SCID) mice, presence of MLL-AF4, and BCR-ABL fusion transcripts were associated with high levels of BCL-2 expression. Overall, high BCL-2 levels were not associated with slow early response, failure to achieve complete remission, or poor event-free survival. High BCL-2 levels in primary leukemic cells predicted slow early response only in T-lineage ALL patients, which comprised approximately 15% of the total patient population. Even for this small subset of patients, the level of BCL-2 expression did not have a significant impact on the short-term event-free survival.

Phyto-oestrogens and Western diseases

Incidences of breast, colorectal and prostate cancer are high in the Western world compared to countries in Asia. We have postulated that the Western diet compared to the semivegetarian diet in some Asian countries may alter hormone production, metabolism or action at the cellular level by some biochemical mechanisms. Our interest has been focused on two groups of hormone-like diphenolic phyto-oestrogens of dietary origin, the lignans and isoflavonoids abundant in plasma of subjects living in areas with low cancer incidence. The precursors of the biologically active compounds detected in man are found in soybean products, whole-grain cereal food, seeds, and berries. The plant lignan and isoflavonoid glycosides are converted by intestinal bacteria to hormone-like compounds. The weakly oestrogenic diphenols formed influence sex-hormone production, metabolism and biological activity, intracellular enzymes, protein synthesis, growth factor action, malignant cell proliferation, differentiation, cell adhesion and angiogenesis in such a way as to make them strong candidates for a role as natural cancer-protective compounds. Their effect on some of the most important steroid biosynthetic enzymes may result in beneficial modulation of hormone concentrations and action in the cells preventing development of cancer. Owing to their oestrogenic activity they reduce hot flushes and vaginal dryness in postmenopausal women and may to some degree inhibit osteoporosis, but alone they may be insufficient for complete protection. Soy intake prevents oxidation of the low-density lipoproteins in vitro when isolated from soy-treated individuals and affect favourably plasma lipid concentrations. Animal experiments provide evidence suggesting that both lignans and isoflavonoids may prevent the development of cancer as well as atherosclerosis. However, in some of these experiments it has not been possible to separate the phyto-oestrogen effect from the effect of other components in the food. The isoflavonoids and lignans may play a significant inhibitory role in cancer development particularly in the promotional phase of the disease, but recent evidence points also to a role in the initiation stage of carcinogenesis. At present, however, no definite recommendations can be made as to the dietary amounts needed for prevention of disease. This review deals with all the above-mentioned aspects of phyto-oestrogens.

Granulocyte-macrophage colony-stimulating factor receptor-targeted therapy of chemotherapy- and radiation-resistant human myeloid leukemias

Contemporary therapies for acute myeloid leukemia (AML) commonly fail to cure patients because of the emergence of drug resistance. Drug resistance in AML is multifactorial but can be associated with the overexpression of transmembrane transporter molecules, including P-glycoprotein (Pgp) or the multidrug resistance-associated protein (MRP), or associated with inactivation of the p53 tumor suppressor gene, as well as overexpression of the anti-apoptotic protein bcl-2. We are investigating if novel recombinant biotherapeutics can circumvent these resistance mechanisms to effectively treat refractory AML. To target the lethal action of diphtheria toxin (DT) to high affinity granulocyte-macrophage colony-stimulating factor (GMCSF) receptors on AML blasts, we have produced a recombinant chimeric fusion toxin, DTctGMCSF. Since DTctGMCSF enters and kills its target cells by unique mechanisms (GMCSF-receptor binding and protein synthesis inhibition) and is not similar in structure to Pgp or MRP substrates, we postulated that it would be an active agent against therapy-resistant AML. DTctGMCSF was selectively cytotoxic (IC50 1-10ng/ml) to GMCSF-receptor positive AML cells expressing the Pgp- or MRP-associated multi-drug resistant phenotypes, despite high level resistance to conventional chemotherapeutic agents. DTctGMCSF also efficiently killed AML cells deficient in p53 expression, as well as radiation-resistant AML cells and mixed lineage leukemia cells expressing high levels of bcl-2. In addition, DTctGMCSF killed > 99% of primary leukemic progenitor cells from therapy-refractory AML patients under conditions that we have previously found to not adversely affect the proliferative capacity or differentiation of pluripotent normal hematopoietic progenitor cells. DTctGMCSF may prove useful in treating myeloid leukemias that are otherwise resistant to a wide range of conventional therapies.

A recombinant fusion toxin targeted to the granulocyte-macrophage colony-stimulating factor receptor

Human granulocyte-macrophage colony stimulating factor (GMCSF) and its high affinity receptor function to regulate the proliferation and differentiation of myeloid lineage hematopoietic cells, and may participate in the pathogenesis of many malignant myeloid diseases. We have used genetic engineering based on the elucidated molecular structures of human granulocyte-macrophage colony-stimulating factor and diphtheria toxin (DT) to produce a recombinant fusion toxin, DTctGMCSF, that targets diphtheria toxin to high affinity GMCSF receptors expressed on the surface of blast cells from a large fraction of patients with acute myeloid leukemia (AML). DTctGMCSF was specifically immunoreactive with antidiphtheria toxin and anti-GMCSF antiseras, and exhibited the characteristic catalytic activity of diphtheria toxin, catalyzing the in vitro ADP-ribosylation of purified elongation factor 2. The cytotoxic effects of DTctGMCSF were examined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-tetrazolium (MTT) bromide assay of cell viability and in vivo assays of protein synthesis inhibition. DTctGMCSF were specifically cytotoxic to human leukemia cell lines bearing high affinity receptors for human GMCSF with IC50 of 10(-9) to 10(-11) M. It was not toxic to mammalian hematopoietic cell lines lacking human GMCSF (hGMCSF) receptors. In receptor positive cells, cytotoxicity can be specifically blocked by a large excess of hGMCSF, confirming that its cytotoxicity is mediated through the hGMCSF receptor. THough DTctGMCSF inhibited granulocyte-macrophage colony formation by committed myeloid progenitor cells (CFU-GM), it did not significantly affect erythroid burst formation by committed erythroid progenitor cells (BFU-E), or mixed granulocyte-erythroid-macrophage-megakaryocyte colony formation by pluripotent multilineage progenitor cells (CFU-GEMM). DTctGMCSF holds promise for the treatment of myeloid lineage malignancies, and is a useful reagent to study hematopoiesis.

A Superantigen-Antibody Fusion Protein for T-Cell Immunotherapy of Human B-Lineage Malignancies

The bacterial superantigen staphylococcal enterotoxin A (SEA) is an efficient activator of cytotoxic T cells when presented on major histocompatibility complex (MHC) class II molecules of target cells. Our previous studies showed that such SEA-directed T cells efficiently lysed chronic B-lymphocytic leukemia (B-CLL) cells. Next, we made a mutated SEA–protein A (SEAm-PA) fusion protein with more than 1,000-fold reduced binding affinity for MHC class II compared with native SEA. The fusion protein was successfully used to direct T cells to B-CLL cells coated with different B lineage–directed monoclonal antibodies (MoAbs). In this communication, we constructed a recombinant anti-CD19-Fab-SEAm fusion protein. The MHC class II binding capacity of the SEA part was drastically reduced by a D227A point mutation, whereas the T-cell activation properties were retained. The Fab part of the fusion protein displayed a binding affinity for CD19+ cells in the nanomolar range. The anti-CD19-Fab-SEAm molecule mediated effective, specific, rapid, and perforin-like T-cell lysis of B-CLL cells at low effector to target cell ratios. Normal CD19+ B cells were sensitive to lysis, whereas CD34+ progenitor cells and monocytes/macrophages were resistant. A panel of CD19+ B-cell lines representing different B-cell developmental stages were efficiently lysed, and the sensitivity correlated with surface ICAM-1 expression. The anti-CD19-Fab-SEAm fusion protein mediated highly effective killing of tumor biopsy cells representing several types of B-cell non-Hodgkin's lymphoma (B-NHL). Humanized severe combined immune deficiency (SCID) mice carrying Daudi lymphoma cells were used as an in vivo therapy model for evaluation of the anti-CD19-Fab-SEAm fusion protein. Greater than 90% reduction in tumor weight was recorded in anti-CD19-Fab-SEAm–treated animals compared with control animals receiving an irrelevant Fab-SEAm fusion protein. The present results indicate that MoAb-targeted superantigens (SAgs) may represent a promising approach for T-cell–based therapy of CD19+ B-cell malignancies.

A comparative survey of leguminous plants as sources of the isoflavones, genistein and daidzein: implications for human nutrition and health

Over 80 taxa of mostly agriculturally important legumes were surveyed as sources of the metabolites, genistein and daidzein. Remarkably high concentrations (over 2 g.kg-1 dry weight) of the anticancer metabolite, genistein, were found in the leaves of Psoralea corylifolia (Indian bread root). All other legumes, with the exception of fermented soybean miso, had genistein levels < 400 mg.kg-1 dry weight. Concentrations of over 1 g.kg-1 dry weight and 0.95 g.kg-1 dry weight of the anticancer metabolite, daidzein, were found in the stems of the fava bean (Vicia faba) and roots of kudzu vine (Pueraria lobata), respectively. From this survey, our results indicate that the legumes, lupine (Lupinus spp.), fava bean, (Vicia faba), soybeans (Glycine max), kudzu (Pueraria lobata), and psoralea (Psoralea corylifolia), are excellent food sources for both genistein and daidzein. Miso, a fermented soybean product, is also a rich source of both isoflavones.

Inhibition of epidermal growth factor receptor-associated tyrosine kinase blocks glioblastoma invasion of the brain

OBJECTIVE

Glioblastoma multiforme is a malignant primary brain tumor associated with short patient survival despite aggressive treatment, in part because of its propensity to aggressively infiltrate into brain tissue. Glioblastoma multiforme is also unique because it is the only nonepithelial human tumor for which excessive activation of epidermal growth factor receptor (EGFR) has been consistently linked to tumor growth and patient survival, and EGFR activation promotes glioblastoma multiforme infiltration in vitro.

METHODS

Cocultures of human glioblastoma spheroids (derived from three separate patients) and fetal rat brain aggregates were examined for infiltration using confocal microscopy, in the presence of 0 to 100 mumol/L genistein, a tyrosine kinase (TK) inhibitor, and 3 mumol/L tyrphostin A25, a specific EGFR-TK inhibitor.

RESULTS

Infiltration (not attachment) was completely inhibited by genistein at 10 mumol/L, the IC20 for monolayer growth inhibition in two cell lines. Tyrphostin A25 at 3 mumol/L (the IC20 for monolayers) reduced invasion in a third cell line from 38.8 +/- 6.1% invasion-hour per hour (n = 5) to 2.9 +/- 1.2% invasion-hour per hour (n = 6) (P = 0.0002, two-tailed t test, 93% inhibition), and from 0.54 +/- 0.065% per hour (slope) to 0.028 +/- 0.018% per hour (P = 0.00001, 95% inhibition). Maximal percent invasion was reduced from 100 +/- 0 to 7.4 +/- 5.6% of the fetal rat brain aggregate. No change was detected in EGFR-associated tyrosine phosphorylation at those doses in monolayers by 32P immunolabeling, consistent with the known effects of low concentrations of TK inhibitors. An increase in expression of wild-type and truncated EGFR was demonstrated by Western blotting. Invasion was equally well inhibited by a monoclonal antibody to the high-affinity ligand binding domain of EGFR and not by antibody to an inactive domain.

CONCLUSION

Our observations support the role of EGFR activation as a determinant by which glioblastoma invades normal brain tissue, and we show that invasion can be effectively inhibited at much lower concentrations of TK inhibitors than are necessary for growth suppression.