Harnessing engineered antibodies of the IgE class to combat malignancy: initial assessment of FcɛRI-mediated basophil activation by a tumour-specific IgE antibody to evaluate the risk of type I hypersensitivity

BACKGROUND

IgE antibodies, sequestered into tissues and retained locally by the high-affinity IgE receptor, FcɛRI, on powerful effector cells such as mast cells, macrophages and eosinophils, may offer improvements in the therapy of solid tumours. The chimeric antibody, MOv18 IgE, against the human ovarian carcinoma antigen, folate receptor α (FRα), is more effective than its IgG1 counterpart in xenograft models of ovarian cancer. Although MOv18 IgE binds to a single epitope on FRα and cannot cross-link IgE receptors on basophils, there remains a risk that components in the circulation of ovarian cancer patients might cross-link FRα-MOv18-IgE-receptor-FcɛRI complexes on basophils to cause type I hypersensitivity.

OBJECTIVE

To assess the propensity for MOv18 used in a therapeutic setting to cause FcɛRI-mediated type I hypersensitivity.

METHODS

As validated readouts of the potential for MOv18 to cause FcɛRI-mediated type I hypersensitivity we measured release of a granule-stored mediator from a rat basophilic leukaemia cell line RBL SX-38 stably transfected with human tetrameric (αβγ2) FcɛRI, and induction of CD63 on blood basophils from patients with ovarian carcinoma and healthy controls ex vivo.

RESULTS

Serum FRα levels were increased in ovarian cancer patients compared with healthy controls. MOv18 IgE alone, or in the presence of its antigen recombinant human FRα, or of healthy volunteer (n=14) or ovarian carcinoma patient (n=32) sera, did not induce RBL SX-38 cell degranulation. Exposure to FRα-expressing ovarian tumour cells at target-to-effector ratios expected within tumours induced degranulation. MOv18 IgE did not induce expression of CD63 in blood basophils from either healthy volunteers (n=6), or cancer patients, despite detectable levels of circulating FRα (n=5).

CONCLUSION AND CLINICAL RELEVANCE

These encouraging data are compatible with the hypothesis that, when ovarian carcinoma patients are treated with MOv18, FcɛRI-mediated activation of effector cells occurs within the tumour mass but not in the circulation mandating, with due caution, further pre-clinical studies.

Final follow up survey of the randomized Pbo-controlled study of oregovomab (Ov) as a consolidation treatment for advanced ovarian cancer (OC): Insights into surveillance approaches

5079

Background: Ov is a monoclonal antibody specific for CA125 currently in two phase III studies as a consolidation immunotherapy for OC. A five year outcome follow up for patients participating in the prior randomized phase II study used to design the current pivotal trials has been completed. An assessment of survival post relapse (SPR) as a function of identifiable risk factors, and implications for long term survival survey methodology were reviewed. Methods: OC patients with no evaluable disease post front-line chemotherapy were randomized to IV infusions of OV or Pbo Q4 wks × 3, then Q12 wks. At relapse, therapy was stopped and second-line Rx was initiated without restriction. All patients were surveyed quarterly for long term outcomes for a pre-specified 5 years from initial randomization. A Kaplan-Meier (KM) analysis of overall survival and Cox multivariate analysis of SPR was completed. Results: 145 randomized participants were followed, including 67 designated as the successful front-line (SFLT) subpopulation identified to have characteristics favorable for intervention with immunotherapy (basis of ongoing phase III program). At five years, 47% of Ov (n = 73) and 37% of Pbo (n = 72) patients were alive overall, and 56% of Ov (n = 34) and 32% of Pbo (n = 33) were alive in the SFLT population. KM estimates of median survival are 57.5 mo [44.5-non-estimable (ne)] for Ov and 48.6 mo [30.9-ne] for Pbo in the overall population and ne mo [50.5-ne] for Ov and 48.6 mo [24-ne] for Pbo (p = 0.11) in the subpopulation. For relapsed patients, improved survival post relapse was most associated (Cox regression p < 0.10) with lower CA125 velocity at relapse, treatment (Ov), and longer time to relapse. Conclusions: Survival data was consistent with previously reported time to relapse data in this study. For the SFLT, the 5 yr duration of survival survey and sample size were insufficient for a definitive outcome. However, results support the hypothesis that treatment with OvaRex may provide clinical benefit. The ongoing phase III studies will include a 10 year survival survey of 354 patients to definitively assess the impact of this treatment on long term survival.

[Table: see text]

A pilot phase 2 study of oregovomab murine monoclonal antibody to CA125 as an immunotherapeutic agent for recurrent ovarian cancer

This prospective, open-label, pilot phase 2 study examined the clinical and immunologic effects of oregovomab (OvaRex) in heavily pretreated patients with recurrent ovarian cancer (OC). Thirteen women were administered intravenous oregovomab (2 mg) at weeks 0, 2, 4, 8, and 12, followed by quarterly doses for up to 2 years or disease progression. Concomitant chemotherapy was not permitted. Eligibility criteria included recurrence after one or more platinum-based chemotherapy regimens, CA125 >35 U/mL, evaluable or measurable disease. Tumor burden was evaluated by physical or radiologic methods pretreatment, weeks 12, 24, and every 24 weeks thereafter. Immune responses, including antibodies and T cells to oregovomab and CA125, were demonstrated in over half the patients. Stabilization of disease and survival >2 years was observed in 3 of 13 patients and coincided with robust immune responses. Shrinkage of marker lesions was not observed; however, four patients showed decreases in CA125 levels. Treatment was well tolerated without serious adverse events or discontinuations due to therapy. This pilot study supports immunologic activity and safety of oregovomab in recurrent OC. Further study of this agent in the consolidation and adjuvant setting is ongoing to establish its clinical utility.

Phase I trial of a murine antibody to MUC1 in patients with metastatic cancer: evidence for the activation of humoral and cellular antitumor immunity

BACKGROUND

BrevaRex mAb-AR20.5 is a murine anti-MUC1 monoclonal antibody generated to induce MUC1 antigen-specific immune responses through the formation of immune complexes with circulating MUC1 and/or MUC1-expressing tumor cells that may target these immune complexes (IC) to receptors on dendritic cells (DCs).

PATIENTS AND METHODS

A phase I study focusing on safety and immunology evaluated 1, 2 and 4-mg doses. Seventeen patients with MUC1-positive cancers received intravenous infusions of the antibody over 30 min on weeks 1, 3, 5, 9, 13 and 17 of treatment.

RESULTS

mAb-AR20.5 was well-tolerated, not associated with dose-limiting toxicity, and did not induce hypersensitivity reactions. Overall, five of 15 evaluable patients developed human anti-mouse antibodies (HAMA), five developed anti-idiotypic antibodies (Ab2) and seven developed anti-MUC1 antibodies. Immune responses were most prominent in the 2-mg dose cohort for all parameters tested, and treatment-emergent MUC1-specific T-cell responses were detected in five of 10 evaluable patients treated with mAb-AR20.5.

CONCLUSIONS

The injection of a murine antibody to MUC1 induces MUC1-specific immune responses in advanced cancer patients. Anti-MUC1 antibody increases correlated with decrease or stabilization of CA15.3 levels (P=0.03). The 2-mg dose of mAb-AR20.5 showed strongest biological activity, and will be evaluated in future efficacy trials.

Immunotherapy with Fel d 1 peptides decreases IL-4 release by peripheral blood T cells of patients allergic to cats

BACKGROUND

Cells producing a T(H2)-cytokine profile play an important role in the onset and maintenance of atopic diseases, and therefore specific immunotherapy is aimed to induce a switch to cells producing a T(H1)- or T(H0)-cytokine profile. Recently, a novel form of immunotherapy making use of synthetic peptides from the major cat allergen Fel d 1 has been developed, but its mechanisms of action are unknown.

OBJECTIVES

We examined the effects of immunotherapy with Fel d 1 peptides on the response to bronchial provocation tests (PD20FEV1) with a standardized Fel d 1 cat extract on Fel d 1-specific serum IgE and IgG levels and in vitro IL-4 and IFN-gamma production.

METHODS

Patients allergic to cats received 6 weekly injections of 7.5 micro(g) (low dose), 75 micro(g) (medium dose), or 750 micro(g) (high dose) of Fel d 1 peptides (25 patients) or a placebo (6 patients).

RESULTS

Six weeks after ending immunotherapy, posttreatment PD20FEV1 was not significantly different between the treated and placebo groups. However, in the medium- and high-dose groups there was a significant improvement between baseline and posttreatment days. IL-4 release was significantly reduced in the high dose-treated group (P <.005, Wilcoxon W test), whereas it was unchanged in the low or medium dose- and in the placebo-treated groups. In all groups, IFN-gamma, IgE, and IgG levels remained unchanged.

CONCLUSION

There was no correlation between the improvement of PD20FEV1 and the decrease in IL-4 production. These data suggest that peptide immunotherapy may act by shifting the Fel d 1-induced response of PBMCs in vitro from the T(H2)-like to the T(H0)-like phenotype.

Effects of peptide therapy on ex vivo T-cell responses

BACKGROUND

Peptide therapy targets T cells directly with short peptides containing multiple T-cell receptor epitopes. Murine studies suggest T-cell anergy as the mechanism of action; however, changes in T-cell cytokine profiles may be more relevant in human beings.

OBJECTIVE

We sought to study the effects of peptide therapy on ex vivo antigen-specific T-cell responses.

METHODS

Antigen-specific T-cell lines were generated from subjects enrolled in a double-blind, placebo controlled, two-dose study of the ALLERVAX CAT therapeutic, containing Fel d 1 peptides (ImmuLogic Pharmaceutical Corp., Waltham, Mass.) (n = 7, 8, and 7, respectively, for groups receiving placebo, 75 microg, or 750 microg). Each subject had three lines propagated before and after receiving peptide therapy; antigens used were cat hair extract, Fel d 1 peptides, and tetanus toxoid (negative control). Proliferative responses and cytokine generation from each line were assessed after two restimulations with antigen and autologous antigen-presenting cells.

RESULTS

The Fel d 1 peptide lines showed a dose-dependent decrease of IL-4 production (p = 0.02 and 0.025, respectively, for the 750 microg group vs both the 75 microg and placebo groups). IL-4 production from the cat hair allergen extract lines and interferon-gamma production from both the Fel d 1 peptide lines and cat hair allergen extract lines showed no statistically significant changes. The control tetanus toxoid lines showed no changes in cytokine production; there were no significant changes in proliferation with any of the antigens in any of the treatment groups. In the clinical arm of the trial, only the 750 microg dose of peptides produced a significant response.

CONCLUSIONS

Peptide therapy induces a significant, dose-dependent decrease in peptide-stimulated IL-4 production, consistent with either a shift in T-cell phenotype or peptide-specific T-cell tolerance.

Mouse mast cells that possess segmented/multi-lobular nuclei

Because in humans mast cells and basophils tend to possess nonsegmented and segmented/multi-lobular nuclei, respectively, nuclear morphology has been a major criterion for assessing the lineage of metachromatic cells of hematopoietic origin. Immature metachromatic cells with mono- and multi-lobular nuclei were both obtained when bone marrow cells from BALB/c mice were cultured for 3 weeks in the presence of interleukin-3. Analogous to the indigenous mature mast cells that reside in the peritoneal cavity and skin, both populations of in vitro-derived cells expressed the surface receptor c-kit, the chymase mouse mast cell protease (mMCP) 5, the tryptase mMCP-6, and the exopeptidase carboxypeptidase A (mMC-CPA). Immunogold electron microscopy confirmed the granule location of mMC-CPA and mMCP-6 in both populations of cells, and cytochemical analysis confirmed the presence of chymotryptic enzymes in the granules. Because mature mast cells possessing multi-lobular nuclei also were occasionally found in the skeletal muscle and jejunum of the BALB/c mouse, the V3 mouse mast cell line was used to investigate the developmental relationship of mast cells that have very different nuclear structures. After the adoptive transfer of V3 mast cells into BALB/c mice, v-abl-immortalized mast cells with mono- and multi-lobular nuclei were detected in the lymph nodes and other tissues of the mastocytosis mice that expressed c-kit, mMCP-5, mMCP-6, and mMC-CPA. These studies indicate that mouse mast cells can exhibit varied nuclear profiles. Moreover, the nuclear morphology of this cell type gives no insight as to its protease phenotype or stage of development.

Clinical and immunologic effects of component peptides in Allervax Cat

Peptides have been designed to be T cell tolerogenic for the principal allergens of the cat. These have been administered in several dosage programs to cat-sensitive patients in multicenter blinded studies. In contrast to proteins in standard extracts, IgE sensitization to peptides is an uncommon event. Pretreatment prick tests with peptides will identify the occasional sensitized patient. Other side reactions consist of allergic symptoms occurring on the day of injections. These become less severe with subsequent injections and are easily treatable with antihistamines or bronchodilators, depending on the symptoms. Treatment with cat peptides ameliorated symptoms that occur upon exposure to cats 1-6 or more weeks later. A 2-week course of 4 injections is the most effective of the regimens so far tried. T-cell-active peptides offer a promising low-risk alternative for specific treatment of respiratory allergies.

Treatment of cat allergy with T-cell reactive peptides

We induced in allergic humans the counterpart of murine experimental T-cell tolerance. T-cell lines from cat-allergic humans were used to map T-cell epitopes for the principal allergen of cat dander, Fel d 1. Two peptides of 27 amino acids each were synthesized to contain the dominant epitopes (ALLERVAX CAT). After a safety trial, we carried out a blinded study of the dose required for efficacy. We randomly divided 95 cat-sensitive patients into placebo, 7.5 micrograms, 75 micrograms, and 750 micrograms groups. Patients received a subcutaneous injection weekly for 4 wk. Before and after treatment, patients were exposed in a room inhabited by live cats and scored by nose and lung symptoms. Baseline nasal and lung scores (+/-SEM) were 6.2 +/- 0.56 and 5.4 +/- 0.73 in the 750 micrograms group; 7.8 +/- 0.53 and 4.7 +/- 0.68 in the placebo group. Six weeks after treatment, scores adjusted for baseline differences were reduced in the 750 micrograms group: -2.3 +/- 4.9 and -2.3 +/- 0.59 compared with -0.84 +/- 0.50 and -0.85 +/- 0.62 in the placebo group. The 75 micrograms group showed intermediate effects and the 7.5 micrograms group no effect. Linear trend analysis indicated a significant dose response effect: p = 0.05 for nose and 0.03 for lung symptoms. Allergic side effects occurred an hour or more after the first 750 micrograms dose in 16 of 24 patients but required little or no treatment with one exception. T-cell reactive treatment peptides safely improved allergic responses to cats.

Comparison of the bronchodilatory effects of cetirizine, albuterol, and both together versus placebo in patients with mild-to-moderate asthma

BACKGROUND

Many potential users of the H1 antihistamine cetirizine are asthmatic and may be using inhaled albuterol. This study was conducted to assess the possible bronchodilatory effect of cetirizine in patients with mild-to-moderate asthma and to determine whether cetirizine interacts with albuterol.

METHODS

In a randomized, double-blind, placebo-controlled, crossover study, the effects on pulmonary function of 5, 10, and 20 mg oral doses of cetirizine with and without inhaled albuterol (180 micrograms) were determined in 12 patients at 11 time points over 8 hours. The primary measure of efficacy was forced expiratory volume in 1 second (FEV1).

RESULTS

Cetirizine with or without albuterol significantly increased FEV1, peak expiratory flow rate, and forced expiratory flow rate between 25% and 75% of vital capacity relative to baseline and placebo but did not have a significant effect on forced vital capacity. The effect of 20 mg of cetirizine on FEV1 was generally greater than that of 10 or 5 mg, but the difference was statistically significant only at the 30-minute time point (p < 0.05). All three cetirizine doses produced significantly greater increases than placebo in FEV1 and forced expiratory flow rate between 25% and 75% of vital capacity for 8 hours and in peak expiratory flow rate for 7 hours (p < 0.02). Albuterol alone had a significant effect on the four pulmonary function variables from 1 to 5 hours after baseline (p < 0.05), which is consistent with albuterol's recommended dosing frequency of every 4 to 6 hours. Albuterol alone increased FEV1 significantly more than 5 mg of cetirizine alone but not 10 mg or 20 mg of cetirizine alone at 60, 90, and 120 minutes after baseline, but all three doses of cetirizine increased FEV1 significantly more than albuterol 7 and 8 hours after baseline (p < 0.05), indicating that the bronchodilatory action of cetirizine lasts longer than that of albuterol. Cetirizine neither potentiated nor inhibited the bronchodilatory action of albuterol, but the two drugs appeared to have an additive bronchodilatory effect. None of the cetirizine treatments caused a worsening of pulmonary function, and all were well tolerated.

CONCLUSIONS

Cetirizine has a significant bronchodilatory effect in patients with mild-to-moderate asthma and can be used to treat concomitant conditions (e.g., allergic rhinitis) without concern that it will interfere with the bronchodilatory effect of albuterol or cause worsening of asthma by itself.

Cetirizine in patients with seasonal rhinitis and concomitant asthma: prospective, randomized, placebo-controlled trial

OBJECTIVE

This study explored the safety and efficacy of cetirizine for treatment of allergic rhinitis and asthma.

METHODS

Daily treatment for 6 weeks with cetirizine 10 mg (93 patients) was compared with placebo treatment (93 patients) in a randomized, double-blind parallel study of patients with allergic rhinitis and asthma. This multicenter study was started just before onset of the fall pollen season. Rhinitis and asthma symptoms were assessed twice daily; spirometry was performed weekly.

RESULTS

Placebo-treated patients experienced a worsening of rhinitis symptoms from baseline throughout the study, whereas cetirizine-treated patients had a significant improvement in rhinitis symptoms at week 1, which was maintained after onset of the pollen season. Asthma symptoms in the cetirizine group improved from baseline at week 1; symptoms were significantly better than in the placebo group for 5 of 6 weeks of the study. Pulmonary function did not worsen in patients taking cetirizine or placebo; there were no differences between treatments as determined by spirometry. Albuterol use was less frequent in the cetirizine-treated patients for every week of the study, but differences did not reach significance. Pseudoephedrine use was similar in both groups. More cetirizine-treated patients (90%) completed the trial than did placebo-treated patients (74%). Both treatments were well tolerated.

CONCLUSION

Cetirizine 10 mg daily is safe and effective in relieving both upper and lower respiratory tract symptoms in patients with seasonal allergic rhinitis and concomitant asthma.

Reversible expression of mouse mast cell protease 2 mRNA and protein in cultured mast cells exposed to IL-10

BALB/cJ mouse mast cells derived by culturing bone marrow progenitor cells in WEHI-3 cell-conditioned medium (BMMCW) do not contain mouse mast cell protease 2 (mMCP-2) mRNA, but these cells can be induced to express this transcript after exposure to rIL-10. To study the translation and granule accumulation of mMCP-2 in rIL-10-treated BMMC (BMMCW+IL-10), a rabbit antibody was developed to a synthetic peptide that corresponds to the novel amino acid sequence in mMCP-2 at residues 56 to 71. After affinity purification, this antibody, anti-mMCP-2(56-71) IgG, reacted in SDS-PAGE/immunoblots against a 28-kDa protein in BMMCW+IL-10 that had the N-terminal amino acid sequence of mMCP-2. As assessed immunohistochemically, mMCP-2 protein accumulated in the secretory granules of Kirsten sarcoma virus-immortalized mouse mast cells, BMMCW+IL-10, and the mucosal mast cells present in the jejunum of Trichinella spiralis-infected BALB/cJ mice. Time course analyses of the induction of mMCP-2 mRNA and protein in BMMCW+IL-10 revealed that these cells contain a high steady-state level of mMCP-2 mRNA 24 h after their exposure to rIL-10. Although a small amount of immunodetectable mMCP-2 protein is present in the cells treated for 24 h, large amounts of this protease are not obtained until 7 days of treatment of the cells with rIL-10. Time course analyses of the loss of mMCP-2 mRNA and protein in BMMCW+IL-10 revealed that the steady-state level of mMCP-2 mRNA decreased dramatically 24 h after rIL-10 was removed from the culture medium, but that the level of mMCP-2 protein did not decline measurably until day 5 of culture. The fact that the steady-state levels of mMCP-2 mRNA and protein in BMMC can both be reversibly altered by culturing these mast cells in the presence and absence of rIL-10 suggests that the phenotype of mast cells is not fixed. Rather, it is in a dynamic state regulated by the cytokine network to which mast cells are exposed in their different microenvironments.

Reversible expression of mouse mast cell protease 2 mRNA and protein in cultured mast cells exposed to IL-10

BALB/cJ mouse mast cells derived by culturing bone marrow progenitor cells in WEHI-3 cell-conditioned medium (BMMCW) do not contain mouse mast cell protease 2 (mMCP-2) mRNA, but these cells can be induced to express this transcript after exposure to rIL-10. To study the translation and granule accumulation of mMCP-2 in rIL-10-treated BMMC (BMMCW+IL-10), a rabbit antibody was developed to a synthetic peptide that corresponds to the novel amino acid sequence in mMCP-2 at residues 56 to 71. After affinity purification, this antibody, anti-mMCP-2(56-71) IgG, reacted in SDS-PAGE/immunoblots against a 28-kDa protein in BMMCW+IL-10 that had the N-terminal amino acid sequence of mMCP-2. As assessed immunohistochemically, mMCP-2 protein accumulated in the secretory granules of Kirsten sarcoma virus-immortalized mouse mast cells, BMMCW+IL-10, and the mucosal mast cells present in the jejunum of Trichinella spiralis-infected BALB/cJ mice. Time course analyses of the induction of mMCP-2 mRNA and protein in BMMCW+IL-10 revealed that these cells contain a high steady-state level of mMCP-2 mRNA 24 h after their exposure to rIL-10. Although a small amount of immunodetectable mMCP-2 protein is present in the cells treated for 24 h, large amounts of this protease are not obtained until 7 days of treatment of the cells with rIL-10. Time course analyses of the loss of mMCP-2 mRNA and protein in BMMCW+IL-10 revealed that the steady-state level of mMCP-2 mRNA decreased dramatically 24 h after rIL-10 was removed from the culture medium, but that the level of mMCP-2 protein did not decline measurably until day 5 of culture. The fact that the steady-state levels of mMCP-2 mRNA and protein in BMMC can both be reversibly altered by culturing these mast cells in the presence and absence of rIL-10 suggests that the phenotype of mast cells is not fixed. Rather, it is in a dynamic state regulated by the cytokine network to which mast cells are exposed in their different microenvironments.

Effects of cetirizine versus terfenadine in seasonal allergic rhinitis

The purpose of this study was to compare the efficacy and safety of cetirizine, 10 mg, once daily in the morning to terfenadine, 60 mg, BID in the treatment of seasonal allergic rhinitis. The multicenter, single-blind, parallel study involved 160 patients, who were all included in the safety and efficacy analysis. The results of the study showed that both cetirizine, 10 mg, QD and terfenadine, 60 mg, BID used for 1 week are safe and effective in the management of allergic rhinitis. By repeated measures analysis, cetirizine improved symptoms more than terfenadine for the treatment period of days four to seven. Standard Cochran-Mantel-Haenszel statistics test showed the relative degree of patient satisfaction to be higher in the cetirizine group.

The human serglycin gene. Nucleotide sequence and methylation pattern in human promyelocytic leukemia HL-60 cells and T-lymphoblast Molt-4 cells

The complete nucleotide sequence of the 16.7-kb human gene that encodes the peptide core (serglycin) of a secretory granule proteoglycan was determined, thus representing the first proteoglycan peptide core gene to be sequenced in its entirety. The exons, intron 1, and intron 2 comprised 7, 53, and 40% of the gene, respectively. Nineteen Alu-repetitive DNA sequences were interspersed in the gene, accounting for 28% of the total nucleotides in intron 1 and 40% of the nucleotides in intron 2. The nucleotide sequence was then used in an examination of the methylation pattern of the human serglycin gene in human promyelocytic leukemia HL-60 cells that contain serglycin mRNA and in T-lymphoblast Molt-4 cells that do not. With polymerase chain reaction methodology, 13 DNA probes of 250-880 base pairs in length were generated that corresponded to unique, non-Alu sequences spaced throughout the entire human serglycin gene. When blots containing genomic DNA digested with HpaII or MspI were examined with these genomic probes, it was discovered that the 5'-flanking region and intron 1 of the serglycin gene in HL-60 cells were both substantially less methylated than intron 2. In contrast, the entire serglycin gene in Molt-4 cells was highly methylated. Because hypomethylated genes generally are transcribed more efficiently than hypermethylated genes, the high level of serglycin mRNA in HL-60 cells probably is a consequence of the low level of methylation of intron 1 and the 5'-flanking region of the serglycin gene in these cells.

Continuous release of secretory granule proteoglycans from a cell strain derived from the bone marrow of a patient with diffuse cutaneous mastocytosis

A human cell strain (designated HBM-M) that was derived from the bone marrow of a child with diffuse cutaneous mastocytosis was previously found to possess features that suggested it belonged in the mast cell/monocyte lineage. HBM-M cells synthesized approximately 150-Kd Pronase-resistant proteoglycans that were recognized by an antihuman secretory granule proteoglycan peptide core antibody. These cells also contained in relatively high abundance the same sized mRNA transcript that encodes the peptide core of proteoglycans that are normally localized to secretory granules of hematopoietic cells. However, unlike most other hematopoietic cells, HBM-M cells continuously released their newly synthesized 35S-labeled proteoglycans rather than retaining them in an intracellular storage compartment. Chondroitinase ABC, nitrous acid, and heparinase degraded approximately 76%, 17%, and 7%, respectively, of the HBM-M cell-derived 35S-labeled proteoglycans. As assessed by high performance liquid chromatography, 91% of the unsaturated 35S-labeled disaccharides generated by treatment with chondroitinase ABC were delta Di-4S. The remaining chondroitin sulfate 35S-labeled disaccharides appeared to be primarily a complex mixture of disulfated disaccharides. The 35S-labeled glycosaminoglycans that were not degraded by chondroitinase ABC migrated in two-dimensional cellulose acetate electrophoresis as if they were heparan sulfate or under-sulfated heparin. Thus, although the HBM-M cell-derived proteoglycans had some of the features of proteoglycans produced by normal human mast cells, the heparin-like and chondroitin sulfate glycosaminoglycans bound to the HBM-M cell proteoglycans were considerably less sulfated. Because the only human cell types that have so far been shown to synthesize proteoglycans that have heparin-like glycosaminoglycans bound to a protease-resistant peptide core are mast cells and basophilic leukocytes from patients with myelogenous leukemia, it is possible that the HBM-M cell is a mast cell progenitor cell.

Characterization of the human gene that encodes the peptide core of secretory granule proteoglycans in promyelocytic leukemia HL-60 cells and analysis of the translated product

Based upon the deduced amino acid sequence of a cDNA (cDNA-H4) that had been proposed to encode the peptide core of an eosinophil and a HL-60 cell secretory granule proteoglycan, a 16-amino acid peptide was synthesized. This peptide was then used to elicit rabbit antibodies for study of the translation and post-translational modification of this gene product in hematopoietic cells. When HL-60 cells were radiolabeled for 2 min with [35S]methionine, a protein that migrated in a sodium dodecyl sulfate-polyacrylamide electrophoresis gel with a Mr of 20,000 was immunoprecipitated with the IgG fraction of the anti-peptide serum. Kinetic experiments revealed that within 10 min this radiolabeled precursor protein was converted in HL-60 cells into an Mr approximately 150,000 chondroitin sulfate proteoglycan intermediate. After a 20-min to 1-h chase, this [35S]methionine- or [35S]sulfate-labeled proteoglycan intermediate lost its antigenicity, presumably due to proteolysis of its N terminus. A human genomic library was probed under conditions of high stringency with cDNA-H4 to isolate genomic clones that contain the gene that encodes this proteoglycan peptide core. This gene spans approximately 15 kilobases and consists of three exons. The first exon encodes the 5'-untranslated region of the mRNA transcript, as well as the entire 27-amino acid signal peptide of the translated molecule. The second exon encodes a 49-amino acid region of the peptide core, predicted to be the N terminus of the molecule after its proteolytic processing in the endoplasmic reticulum. The third exon encodes the remainder of the molecule, including its glycosaminoglycan attachment, serine-glycine repeat region. As assessed by S1 nuclease mapping and primer extension analysis, the transcription-initiation site in HL-60 cells for this gene resides 53 base pairs upstream from the translation-initiation site.

Cloning and characterization of the mouse gene that encodes the peptide core of secretory granule proteoglycans and expression of this gene in transfected rat-1 fibroblasts

A mouse liver genomic library was probed with a 450-base pair AccI----3' gene-specific fragment of a mouse bone marrow-derived mast cell proteoglycan cDNA to isolate 15-18-kilobase (kb) genomic clones containing the gene that encodes the peptide core of mouse secretory granule proteoglycans. Based on the nucleotide sequences of its 2.0-3.5-kb subcloned fragments, this mouse gene consists of three exons. The first exon contains 41 base pairs of untranslated nucleotides that are present in the 5' region of the transcript and also encodes the hydrophobic 25-amino acid signal peptide. The second exon encodes a 48-amino acid sequence that would be predicted to be the N terminus of the peptide core after the signal peptide has been removed in the endoplasmic reticulum. The third exon encodes a 79-amino acid sequence that includes the 15 amino acids immediately preceding an alternating serine-glycine 21-amino acid sequence for glycosaminoglycan attachment, and the subsequent C-terminal 43 amino acids; this exon also contains the 424 untranslated nucleotides present in the 3' region of the transcript. Primer extension and S1 nuclease protection analyses were performed to determine the transcription initiation site of the mouse gene. Rat-1 fibroblasts were cotransfected with the selectable marker pSV2 neo and a lambda clone (lambda MG-PG1) to obtain two rat-1 fibroblast cell lines that had the mouse secretory granule proteoglycan gene integrated into their genomes. RNA blot analysis of both cell lines revealed the presence of the 1.0-kb secretory granule proteoglycan peptide core mRNA transcript, indicating that lambda MG-PG1 contained the entire mouse secretory granule proteoglycan peptide core gene including some of the regulatory elements in its promoter region. The gene that encodes the peptide core of mouse secretory granule proteoglycans is the first proteoglycan gene to have its complete exon/intron organization determined and to be transfected and expressed in another cell type.

Molecular cloning of a cDNA that encodes the peptide core of a mouse mast cell secretory granule proteoglycan and comparison with the analogous rat and human cDNA

A cDNA that encodes a mouse secretory granule proteoglycan peptide core was isolated from a cDNA library prepared from nontransformed mouse bone marrow-derived mast cells (BMMC) using as a probe a 280-base-pair fragment of a rat cDNA that encodes the proteoglycan peptide core of rat basophilic leukemia (RBL)-1 cells. Based on the consensus nucleotide sequence and deduced amino acid sequence of the cDNA, the mouse BMMC proteoglycan peptide core is 16.7 kDa and contains a 21-amino acid glycosaminoglycan attachment region consisting of alternating serine and glycine residues. When the predicted amino acid sequence of the mouse BMMC proteoglycan peptide core was compared with the predicted amino acid sequences of the homologous molecules expressed in RBL-1 cells and in human promyelocytic leukemia HL-60 cells, the mouse-derived sequence was more closely homologous to the rat sequence than the human sequence except for the length of the serine-glycine repeat region. The N terminus was found to be a highly conserved region of the molecule in the three species, suggesting that this region is important for the structure, function, and/or metabolism of this family of proteoglycans. Nucleotide sequences within the 5' and 3' untranslated regions of the mouse, rat, and human proteoglycan cDNA were conserved. That similar sequences were also present in the corresponding regions of a cDNA that encodes a rat mast cell protease suggests that particular nucleotide sequences may be important for regulation of expression of those proteins that are destined to reside in secretory granules.

Cloning of alpha 2u globulin cDNA using a high efficiency technique for the cloning of trace messenger RNAs

An extremely high-efficiency technique is described for cloning double-stranded (ds) cDNAs in Escherichia coli. The method, which uses two synthetic oligonucleotide linkers rather than one, results in approx. 200--500 recombinant clones per ng of ds cDNA. This technique was used to clone a cDNA comprising 95% of the full length of the mRNA of alpha 2u globulin, a male rat liver protein, which represents approx. 1% of hepatic messenger RNA. The cloned probe was applied to study the complex hormone controls of alpha 2u globulin mRNA in male and female rats.