The IGF1R/INSR Inhibitor BI 885578 Selectively Inhibits Growth of IGF2-Overexpressing Colorectal Cancer Tumors and Potentiates the Efficacy of Anti-VEGF Therapy

Clinical studies of pharmacologic agents targeting the insulin-like growth factor (IGF) pathway in unselected cancer patients have so far demonstrated modest efficacy outcomes, with objective responses being rare. As such, the identification of selection biomarkers for enrichment of potential responders represents a high priority for future trials of these agents. Several reports have described high IGF2 expression in a subset of colorectal cancers, with focal IGF2 amplification being responsible for some of these cases. We defined a novel cut-off value for IGF2 overexpression based on differential expression between colorectal tumors and normal tissue samples. Analysis of two independent colorectal cancer datasets revealed IGF2 to be overexpressed at a frequency of 13% to 22%. An in vitro screen of 34 colorectal cancer cell lines revealed IGF2 expression to significantly correlate with sensitivity to the IGF1R/INSR inhibitor BI 885578. Furthermore, autocrine IGF2 constitutively activated IGF1R and Akt phosphorylation, which was inhibited by BI 885578 treatment. BI 885578 significantly delayed the growth of IGF2-high colorectal cancer xenograft tumors in mice, while combination with a VEGF-A antibody increased efficacy and induced tumor regression. Besides colorectal cancer, IGF2 overexpression was detected in more than 10% of bladder carcinoma, hepatocellular carcinoma and non-small cell lung cancer patient samples. Meanwhile, IGF2-high non-colorectal cancer cells lines displayed constitutive IGF1R phosphorylation and were sensitive to BI 885578. Our findings suggest that IGF2 may represent an attractive patient selection biomarker for IGF pathway inhibitors and that combination with VEGF-targeting agents may further improve clinical outcomes. Mol Cancer Ther; 16(10); 2223-33. ©2017 AACR.

Pharmacological Profile of BI 847325, an Orally Bioavailable, ATP-Competitive Inhibitor of MEK and Aurora Kinases

Although the MAPK pathway is frequently deregulated in cancer, inhibitors targeting RAF or MEK have so far shown clinical activity only in BRAF- and NRAS-mutant melanoma. Improvements in efficacy may be possible by combining inhibition of mitogenic signal transduction with inhibition of cell-cycle progression. We have studied the preclinical pharmacology of BI 847325, an ATP-competitive dual inhibitor of MEK and Aurora kinases. Potent inhibition of MEK1/2 and Aurora A/B kinases by BI 847325 was demonstrated in enzymatic and cellular assays. Equipotent effects were observed in BRAF-mutant cells, whereas in KRAS-mutant cells, MEK inhibition required higher concentrations than Aurora kinase inhibition. Daily oral administration of BI 847325 at 10 mg/kg showed efficacy in both BRAF- and KRAS-mutant xenograft models. Biomarker analysis suggested that this effect was primarily due to inhibition of MEK in BRAF-mutant models but of Aurora kinase in KRAS-mutant models. Inhibition of both MEK and Aurora kinase in KRAS-mutant tumors was observed when BI 847325 was administered once weekly at 70 mg/kg. Our studies indicate that BI 847325 is effective in in vitro and in vivo models of cancers with BRAF and KRAS mutation. These preclinical data are discussed in the light of the results of a recently completed clinical phase I trial assessing safety, tolerability, pharmacokinetics, and efficacy of BI 847325 in patients with cancer. Mol Cancer Ther; 15(10); 2388-98. ©2016 AACR.

A Novel RAF Kinase Inhibitor with DFG-Out-Binding Mode: High Efficacy in BRAF-Mutant Tumor Xenograft Models in the Absence of Normal Tissue Hyperproliferation

BI 882370 is a highly potent and selective RAF inhibitor that binds to the DFG-out (inactive) conformation of the BRAF kinase. The compound inhibited proliferation of human BRAF-mutant melanoma cells with 100× higher potency (1-10 nmol/L) than vemurafenib, whereas wild-type cells were not affected at 1,000 nmol/L. BI 882370 administered orally was efficacious in multiple mouse models of BRAF-mutant melanomas and colorectal carcinomas, and at 25 mg/kg twice daily showed superior efficacy compared with vemurafenib, dabrafenib, or trametinib (dosed to provide exposures reached in patients). To model drug resistance, A375 melanoma-bearing mice were initially treated with vemurafenib; all tumors responded with regression, but the majority subsequently resumed growth. Trametinib did not show any efficacy in this progressing population. BI 882370 induced tumor regression; however, resistance developed within 3 weeks. BI 882370 in combination with trametinib resulted in more pronounced regressions, and resistance was not observed during 5 weeks of second-line therapy. Importantly, mice treated with BI 882370 did not show any body weight loss or clinical signs of intolerability, and no pathologic changes were observed in several major organs investigated, including skin. Furthermore, a pilot study in rats (up to 60 mg/kg daily for 2 weeks) indicated lack of toxicity in terms of clinical chemistry, hematology, pathology, and toxicogenomics. Our results indicate the feasibility of developing novel compounds that provide an improved therapeutic window compared with first-generation BRAF inhibitors, resulting in more pronounced and long-lasting pathway suppression and thus improved efficacy.

Efficacy and mechanism of action of volasertib, a potent and selective inhibitor of Polo-like kinases, in preclinical models of acute myeloid leukemia

Polo-like kinase 1 (Plk1), a member of the Polo-like kinase family of serine/threonine kinases, is a key regulator of multiple steps in mitosis. Here we report on the pharmacological profile of volasertib, a potent and selective Plk inhibitor, in multiple preclinical models of acute myeloid leukemia (AML) including established cell lines, bone marrow samples from AML patients in short-term culture, and subcutaneous as well as disseminated in vivo models in immune-deficient mice. Our results indicate that volasertib is highly efficacious as a single agent and in combination with established and emerging AML drugs, including the antimetabolite cytarabine, hypomethylating agents (decitabine, azacitidine), and quizartinib, a signal transduction inhibitor targeting FLT3. Collectively, these preclinical data support the use of volasertib as a new therapeutic approach for the treatment of AML patients, and provide a foundation for combination approaches that may further improve and prolong clinical responses.

BI 6727, a Polo-like kinase inhibitor with improved pharmacokinetic profile and broad antitumor activity

PURPOSE

Antimitotic chemotherapy remains a cornerstone of multimodality treatment for locally advanced and metastatic cancers. To identify novel mitosis-specific agents with higher selectivity than approved tubulin-binding agents (taxanes, Vinca alkaloids), we have generated inhibitors of Polo-like kinase 1, a target that functions predominantly in mitosis.

EXPERIMENTAL DESIGN

The first compound in this series, suitable for i.v. administration, has entered clinical development. To fully explore the potential of Polo-like kinase 1 inhibition in oncology, we have profiled additional compounds and now describe a novel clinical candidate.

RESULTS

BI 6727 is a highly potent (enzyme IC(50) = 0.87 nmol/L, EC(50) = 11-37 nmol/L on a panel of cancer cell lines) and selective dihydropteridinone with distinct properties. First, BI 6727 has a pharmacokinetic profile favoring sustained exposure of tumor tissues with a high volume of distribution and a long terminal half-life in mice (V(ss) = 7.6 L/kg, t(1/2) = 46 h) and rats (V(ss) = 22 L/kg, t(1/2) = 54 h). Second, BI 6727 has physicochemical and pharmacokinetic properties that allow in vivo testing of i.v. as well as oral formulations, adding flexibility to dosing schedules. Finally, BI 6727 shows marked antitumor activity in multiple cancer models, including a model of taxane-resistant colorectal cancer. With oral and i.v. routes of administration, the total weekly dose of BI 6727 is most relevant for efficacy, supporting the use of a variety of well-tolerated dosing schedules.

CONCLUSION

These findings warrant further investigation of BI 6727 as a tailored antimitotic agent; clinical studies have been initiated.

BI 2536, a potent and selective inhibitor of polo-like kinase 1, inhibits tumor growth in vivo

Fine-mapping of the cell-division cycle, notably the identification of mitotic kinase signaling pathways, provides novel opportunities for cancer-drug discovery. As a key regulator of multiple steps during mitotic progression across eukaryotic species, the serine/threonine-specific Polo-like kinase 1 (Plk1) is highly expressed in malignant cells and serves as a negative prognostic marker in specific human cancer types . Here, we report the discovery of a potent small-molecule inhibitor of mammalian Plk1, BI 2536, which inhibits Plk1 enzyme activity at low nanomolar concentrations. The compound potently causes a mitotic arrest and induces apoptosis in human cancer cell lines of diverse tissue origin and oncogenome signature. BI 2536 inhibits growth of human tumor xenografts in nude mice and induces regression of large tumors with well-tolerated intravenous dose regimens. In treated tumors, cells arrest in prometaphase, accumulate phosphohistone H3, and contain aberrant mitotic spindles. This mitotic arrest is followed by a surge in apoptosis, detectable by immunohistochemistry and noninvasive optical and magnetic resonance imaging. For addressing the therapeutic potential of Plk1 inhibition, BI 2536 has progressed into clinical studies in patients with locally advanced or metastatic cancers.

Tumor targeting properties of monoclonal antibodies with different affinity for target antigen CD44V6 in nude mice bearing head-and-neck cancer xenografts

The CD44 protein family consists of isoforms with tissue-specific expression, which are encoded by standard exons and up to 9 alternatively spliced variant exons (v2-v10) of the same gene. The murine MAbs U36 and BIWA-1, directed against overlapping epitopes within the v6 region of CD44, have previously been shown to efficiently target HNSCC. We herein report on the construction of 1 chimeric (BIWA-2) and 2 humanized (BIWA-4 and BIWA-8) derivatives of BIWA-1. Together with U36 and BIWA-1, these new antibodies were evaluated for affinity to the antigen in vitro as well as for biodistribution and efficacy in RIT using nude mice bearing the HNSCC xenograft line HNX-OE. As determined by surface plasmon resonance, the MAbs bound to CD44v6 with an up to 46-fold difference in affinity (K(d) ranging from 1.1 x 10(-8) to 2.4 x 10(-10) M) with the following ranking: mMAb U36 < hMAb BIWA-4 < hMAb BIWA-8 < mMAb BIWA-1 approximately cMAb BIWA-2. To evaluate their in vivo tumor-targeting properties, 2 MAbs with identical murine or human isotype were labeled with either (131)I or (125)I and administered simultaneously (50 microg/10 microCi each) as pairs showing a stepwise decrease in the difference in affinity: U36 vs. BIWA-1 (35.0-fold difference), BIWA-4 vs. BIWA-2 (14.0-fold) and BIWA-4 vs. BIWA-8 (4.0-fold). Biodistribution was assessed at 1, 2, 3 or 4 and 7 days after injection. Remarkably, for all 3 MAb pairs tested, the lower-affinity MAb showed a higher degree and specificity of tumor localization. The difference in tumor localization was more pronounced when the difference in affinity was larger. For example, 3 days after injection, the lower-affinity mMAb U36 showed a 50% higher tumor uptake than the higher-affinity mMAb BIWA-1, while blood levels and uptake in organs were similar. After labeling with (186)Re (300 or 400 microCi), the same MAb pairs showed RIT efficacy consistent with the biodistribution data: (186)Re-U36 was more effective than (186)Re-BIWA-1, (186)Re-BIWA-4 was slightly more effective than (186)Re-BIWA-2 and (186)Re-BIWA-4 and (186)Re-BIWA-8 demonstrated similar efficacy. Based on these data, we conclude that antibodies with markedly lower affinity to a given target antigen (e.g., U36, BIWA-4) may show superior tumor targeting in comparison with higher-affinity versions of these antibodies.

Identification of tumor antigens in renal cell carcinoma by serological proteome analysis

We have investigated the suitability of proteomics for identification of tumor-associated antigens. First, we compared the proteomes of nontumorous kidney and renal cell carcinoma (RCC) by two-dimensional gel electrophoresis (2-DE) and silver staining. Protein patterns were markedly different (approximately 800 spots in RCCs versus approximately 1400 spots in kidney). 2-DE immunoblotting revealed five RCC-specific spots, reproducibly reactive with RCC-patient but not healthy donor control sera. Two of these antigens were isolated by preparative 2-DE, and identified by Edman sequencing of tryptic peptides. The first antigen, smooth muscle protein 22-alpha (SM22-alpha), is an actin-binding protein of unknown function predominantly expressed in smooth muscle cells. In situ hybridization revealed that SM22-alpha is not expressed in the malignant cells but in mesenchymal cells of the tumor stroma. The second antigen represents carbonic anhydrase I (CAI), an isoform usually not expressed in kidney. Interestingly, a different isoform (CAXII) has previously been identified by serological expression cloning as an antigen overexpressed in some RCCs. In additional assays, antibodies to recombinant CAI or SM22-alpha were detected in sera from 3/11 or 5/11 RCC patients, respectively, whereas sera from 13 healthy individuals did not react. In conclusion, serological proteome analysis may be a new tool for the identification of tumor-associated antigens.

Identification of tumor antigens in renal cell carcinoma by serological proteome analysis

We have investigated the suitability of proteomics for identification of tumor-associated antigens. First, we compared the proteomes of nontumorous kidney and renal cell carcinoma (RCC) by two-dimensional gel electrophoresis (2-DE) and silver staining. Protein patterns were markedly different (approximately 800 spots in RCCs versus approximately 1400 spots in kidney). 2-DE immunoblotting revealed five RCC-specific spots, reproducibly reactive with RCC-patient but not healthy donor control sera. Two of these antigens were isolated by preparative 2-DE, and identified by Edman sequencing of tryptic peptides. The first antigen, smooth muscle protein 22-alpha (SM22-alpha), is an actin-binding protein of unknown function predominantly expressed in smooth muscle cells. In situ hybridization revealed that SM22-alpha is not expressed in the malignant cells but in mesenchymal cells of the tumor stroma. The second antigen represents carbonic anhydrase I (CAI), an isoform usually not expressed in kidney. Interestingly, a different isoform (CAXII) has previously been identified by serological expression cloning as an antigen overexpressed in some RCCs. In additional assays, antibodies to recombinant CAI or SM22-alpha were detected in sera from 3/11 or 5/11 RCC patients, respectively, whereas sera from 13 healthy individuals did not react. In conclusion, serological proteome analysis may be a new tool for the identification of tumor-associated antigens.

Identification and characterization of 9D7, a novel human protein overexpressed in renal cell carcinoma

With the objective of discovering novel tumor-associated antigens of the cancer/testis type, we compared the transcriptional profiles of renal cell carcinoma (RCC) and non-tumorous kidney and further screened for genes expressed in RCC and testis, but not other normal tissues. In a first step, a representational difference analysis library consisting of approximately 1,900 RCC cDNA clones was generated. Clones were then spotted onto filters and hybridized with cDNA probes derived from a testis-specific cDNA library, a pool of RCCs and a pool of 10 healthy normal tissues, respectively. Based on strong hybridization signals with both RCC and testis, but not normal tissue probes, 185 clones were sequenced and annotated. After EST-database comparison, 35 clones were selected for experimental analysis, including conventional and quantitative RT-PCR as well as Northern blotting. Clone 9D7 showed strong mRNA expression in RCC as well as in several other major tumor types. In normal tissues there was little or no mRNA expression with the exception of heart. 9D7 was cloned to full-size and found to represent a novel human gene containing 5 exons residing on chromosome 14. Alternative splicing within exon 1 generates 2 open-reading-frames consisting of 717 or 435 bp corresponding to predicted proteins of 239 or 145 amino acids. 9D7 shows high homology (227/239 amino acids or 95% identity) to a growth factor-inducible gene of Rattus norvegicus involved in apoptosis. In situ hybridization as well as immunohistochemical analysis using 9D7-specific antisera confirmed overexpression of 9D7 in RCCs as compared to normal kidney tissue.

Identification of tumor antigens in renal cell carcinoma by serological proteome analysis

We have investigated the suitability of proteomics for identification of tumor-associated antigens. First, we compared the proteomes of nontumorous kidney and renal cell carcinoma (RCC) by two-dimensional gel electrophoresis (2-DE) and silver staining. Protein patterns were markedly different (approximately 800 spots in RCCs versus approximately 1400 spots in kidney). 2-DE immunoblotting revealed five RCC-specific spots, reproducibly reactive with RCC-patient but not healthy donor control sera. Two of these antigens were isolated by preparative 2-DE, and identified by Edman sequencing of tryptic peptides. The first antigen, smooth muscle protein 22-alpha (SM22-alpha), is an actin-binding protein of unknown function predominantly expressed in smooth muscle cells. In situ hybridization revealed that SM22-alpha is not expressed in the malignant cells but in mesenchymal cells of the tumor stroma. The second antigen represents carbonic anhydrase I (CAI), an isoform usually not expressed in kidney. Interestingly, a different isoform (CAXII) has previously been identified by serological expression cloning as an antigen overexpressed in some RCCs. In additional assays, antibodies to recombinant CAI or SM22-alpha were detected in sera from 3/11 or 5/11 RCC patients, respectively, whereas sera from 13 healthy individuals did not react. In conclusion, serological proteome analysis may be a new tool for the identification of tumor-associated antigens.

Safety and biodistribution of 99mTechnetium-labeled anti-CD44v6 monoclonal antibody BIWA 1 in head and neck cancer patients

The CD44 protein family consists of isoforms, encoded by standard exons and up to nine alternatively spliced variant exons (v2-v10), which are expressed in a tissue-specific way. Expression of v6-containing variants (CD44v6) has been related to aggressive behavior of various tumor types and was shown to be particularly high in squamous cell carcinoma (SCC). Therefore, CD44v6 might be a suitable target for radioimmunoscintigraphy (RIS) and therapy. The present study evaluates the novel high-affinity murine anti-CD44v6 monoclonal antibody (MAb) BIWA 1 for its safety and targeting potential in patients with SCC of the head and neck (HNSCC). Twelve HNSCC patients, who had planned to undergo resection of the primary tumor and neck dissection, were included. Preoperatively, 2, 12, or 52 mg of 99nTc-labeled MAb BIWA 1 was administered. RIS results obtained 21 h after injection were compared with palpation, computed tomography, and magnetic resonance imaging, with histopathology as the gold standard. Moreover, biodistribution of BIWA 1 was evaluated by radioactivity measurement in blood and bone marrow and in biopsies from the surgical specimen obtained 40 h after injection. The distribution of BIWA 1 in tumor biopsies was analyzed by immunohistochemistry. BIWA 1 integrity in the blood was assessed by high-performance liquid chromatography and related to soluble CD44v6 levels in serum samples. No drug-related adverse events were observed. Human antimouse antibody responses were observed in 11 patients. The diagnostic efficacy of RIS appeared to be comparable for the three BIWA 1 dose levels and for the four diagnostic methods. Besides activity uptake in tumor tissue, minimal accumulation of activity was observed in mouth, lungs, spleen, kidney, bone marrow, and scrotal area. Analysis of tissue biopsies revealed high uptake in tumors, with a mean value of 14.2+/-8.4% of the injected dose/kg tumor tissue and a mean tumor:blood ratio of 2.0+/-1.4 at 40 h after injection. Differences among the three dose groups were not statistically significant, although a trend toward lower uptake in the highest dose group was noted. Distribution of BIWA 1 throughout the tumor was heterogeneous for all dose groups, which might be related to the high affinity of the MAb. The mean biological half-life in blood (34.5+/-6.1 h) was not dose dependent. Extensive complex formation of BIWA 1 was observed in the 2-mg group, most probably with soluble CD44v6 present in the blood, and complex formation relatively diminished upon increase of the MAb dose. BIWA 1 is a promising MAb for targeting HNSCC because it can be safely administered to HNSCC patients, while it shows high and selective tumor uptake. However, BIWA 1 is immunogenic, and therefore a chimerized or humanized derivative of BIWA 1 with intermediate affinity will be used in future clinical trials.

Expression of CD44 isoforms on isolated bone marrow plasma cells and peripheral CD19+ B cells of patients with multiple myeloma and healthy individuals

The expression of certain isoforms of CD44 was shown to correlate with aggressiveness and metastatic potential of various tumour types. We analysed the expression of the adhesion molecule CD44 and its variant domains (v6, v7, v7/8, v10) on isolated bone marrow (BM) plasma cells and peripheral blood (PBL) CD19+ B cells of 21 patients with MM and 15 healthy donors. B cells and plasma cells were isolated by immunomagnetic sorting and analysed by two-colour flow cytometry. The expression of CD44 isoforms was significantly higher on PBL B cells of patients with MM than in healthy controls. The elevated expression of CD44 isoforms (v6, v7/8, v10) on PBL B cells correlated with reduced overall survival in MM. CD44 isoforms were more strongly expressed on "larger", activated B cells. Furthermore, CD44 isoforms were found to be simultaneously expressed with CD38hi and CD56 on both, B lymphocytes and plasma cells of patients with MM. The determination of CD44 isoforms on circulating B cells may be helpful in defining prognostically unfavourable subgroups in MM.

Poor diagnostic value of colonic CD44v6 expression and serum concentrations of its soluble form in the differentiation of ulcerative colitis from Crohn's disease

BACKGROUND

Increased expression of CD44v6 on colonic crypt epithelial cells in ulcerative colitis has been suggested as a diagnostic tool to distinguish ulcerative colitis from colonic Crohn's disease.

AIMS

To investigate colonic CD44v6 expression and serum concentrations of soluble CD44v6 (sCD44v6) in patients with ulcerative colitis and Crohn's disease.

METHODS

Colonic biopsy samples were obtained from 16 patients with ulcerative colitis, 13 with ileocolonic Crohn's disease, and 10 undergoing polypectomy. Serum samples were obtained from 15 patients with active ulcerative colitis, 20 with active Crohn's disease, and 20 healthy donors. Colonic CD44v6 expression was evaluated immunohistochemically by monoclonal antibody 2F10 and the higher affinity monoclonal antibody VFF18. Serum sCD44v6 concentrations were measured by ELISA.

RESULTS

2F10 stained colonic epithelium of inflamed ulcerative colitis and Crohn's disease samples in 80% and 40% of cases, respectively, and VFF18 in 95% and 87%, respectively. Both monoclonal antibodies displayed a sensitivity and specificity of 60% and 87% to differentiate ulcerative colitis from colonic Crohn's disease. Serum concentrations of sCD44v6 were lower in patients with ulcerative colitis (median 153 ng/ml; interquartile range (IQR) 122-211) compared with Crohn's disease (219; IQR 180-243) and healthy donors (221; IQR 197-241 (p = 0.002)). Its sensitivity and specificity to discriminate ulcerative colitis from Crohn's disease was 75% and 71%, respectively.

CONCLUSION

Colonic CD44v6 and serum sCD44v6 concentrations do not facilitate reliable differential diagnosis between ulcerative colitis and Crohn's disease.

Human interferon omega--a review

A single functional gene in the human genome codes for interferon omega (IFN-omega), a monomeric glycoprotein distantly related in structure to IFN-alpha and IFN-beta, but unrelated to IFN-gamma. IFN-omega is secreted by virus-infected leukocytes as a major component of human leukocyte interferon. The human class I IFN receptor complex which mediates the biological activity of IFN-alpha and IFN-beta also binds IFN-omega. Its specific activity in a standard in vitro antiviral assay system is 4 x 10(8) U mg-1; potent antiviral activity against several DNA and RNA viruses has been demonstrated. IFN-omega inhibits proliferation of a variety of tumor cell lines in vitro. The protein stimulates natural killer cell activity, enhances expression of major histocompatibility complex class I (but not class II) antigens and inhibits proliferation of lymphocytes stimulated with mitogens or allogeneic cells. IFN-omega is unrelated to IFN-alpha, -beta and -gamma in its antigenic properties, as it does not cross-react with antisera or monoclonal antibodies in immunoassays or antiviral neutralization bioassays. Antibodies induced in patients by long-term IFN-alpha 2 therapy that block IFN-alpha 2 activity do not inactivate IFN-omega. As IFN-omega, like other human IFNs, has a species-restricted biological activity, evaluation of its therapeutic potential will have to await clinical trials.

Characterization of a high-affinity monoclonal antibody specific for CD44v6 as candidate for immunotherapy of squamous cell carcinomas

Variant isoforms of CD44, a family of cell-surface glycoproteins generated by alternative splicing and post-translational modifications, are expressed in a variety of human tumors and play important roles in tumor progression and metastasis formation. The murine monoclonal IgG1 antibody VFF18, specific for an epitope encoded by human CD44 variant exon 6, binds with high affinity to the recombinant protein (Kd = 1.7 x 10(-10) M) as well as to tumor cell lines in vitro, and is suitable for immunohistochemical analysis of human tumors. Screening of more than 500 tumor samples of different histogenesis showed that VFF18 most strongly and uniformly reacts with squamous cell carcinomas (SCC). Detailed analysis of 185 SCC (head and neck, lung, skin) confirmed reactivity of the antibody with 99% of the samples, with intense and homogeneous staining of the tumor cells in the majority of cases, whereas reactivity of VFF18 with normal tissues is limited to certain epithelia and activated lymphocytes. When radiolabelled VFF18 was administered to nude mice bearing human epidermoid carcinoma (A-431) xenograft, fast and selective tumor uptake of the radioimmunoconjugate with a maximum of 18% of the injected dose per gram of tissue was observed. Taken together, these data suggest that mAb VFF18 is a promising targeting vehicle for radioimmunotherapy of squamous cell carcinomas in humans.

Expression of CD44 isoforms in human skin cancer

In animal models, isoforms of CD44 (CD44v) containing sequences encoded by one or several of ten different exons (v1-v10) contribute to tumour metastasis. In certain human cancers, CD44v6 expression is associated with poor prognosis. This paper examines CD44v expression in skin carcinogenesis and skin cancer metastasis. CD44v expression was studied in basal cell carcinoma (BCC), squamous cell carcinoma (SCC), primary malignant melanoma (PMM), metastases of MM (MMM), benign melanocytic naevi (BMN) and normal skin (NS) by immunohistochemistry and reverse transcript polymerase chain reaction (RT-PCR). BCC, SCC and NS expressed several CD44v, including v6, albeit in different distributions and intensities. PMM, MMM and BMN expressed isoforms containing v7/8 and v10, but failed to express epitopes encoded by v5 or v6. Thus, different CD44 isoforms are found in human skin cancers and are modulated during carcinogenesis. However, we did not observe a correlation of CD44v6 expression with metastatic potential.

Expression of CD44 isoforms in human renal cell carcinomas

A series of 27 renal cell carcinomas 4 oncocytomas and 7 samples of tumour free kidney parenchyma were analysed immunohistochemically using eight different CD44 isoform-specific monoclonal antibodies. In normal kidney expression of CD44 isoforms (containing variant exons v6, v7/8 and v10) was found predominantly at the distal tubules. The majority of clear cell carcinomas investigated showed expression of variant exons v5, v7/8 and v10, but not v6. Lack of CD44v6 expression was confirmed by reverse transcription-polymerase chain reaction analysis. Carcinomas of the chromophilic cell type were almost completely devoid of CD44 expression, including the standard form CD44s. This study shows that there are statistically significant differences in the CD44 expression pattern of the two major histological subtypes of renal cell carcinomas (clear cell and chromophilic carcinomas). Moreover, the almost complete lack of CD44 expression in chromophilic carcinomas contrasts with carcinomas of other histogenetic origin investigated including stomach, breast and lung which express various CD44 isoforms abundantly.

Splice variants of the cell surface glycoprotein CD44 associated with metastatic tumour cells are expressed in normal tissues of humans and cynomolgus monkeys

Certain isoforms of the CD44 glycoprotein family play an essential role in the metastatic spread of tumour cells. Protein expression of such CD44 isoforms has also been observed in a variety of human malignancies. In this study, we compared the expression of exon v5- and v6-containing CD44 isoforms in normal human and cynomolgus monkey (Macacca fasciculata) tissues. Cloning and sequencing of cynomolgus CD44 exons v5 and v6 revealed a homology of 97% and 95%, respectively, between man and monkey. Two monoclonal antibodies (MAbs) directed against an epitope encoded by human exon v5 (VFF8) and an epitope encoded by exon v6 (VFF18) were used to determine expression of CD44 isoforms in man and monkey. Immunohistochemical screening of a representative profile of normal human and cynomolgus tissues revealed that expression of exon v5- and v6-containing CD44 isoforms was almost identical in the two species. Exon v6 staining was observed only in a subset of epithelial tissues, whereas v5 staining was additionally detected on certain non-epithelial tissues. These data suggest that cynomolgus monkey could serve as a system to test the usefulness of antivariant CD44 MAbs with regard to antibody-based tumour therapy.

Prognostic value of CD44 splice variant expression in ovarian cancer

In 44 ovarian cancers, CD44 variant (CD44v) expression was investigated immunohistochemically using a variant-specific polyclonal antibody. Patients with CD44v-positive carcinomas had a significantly shorter disease-free survival than patients with CD44v-negative tumors. Overall survival was also significantly reduced for stages III and IV of the International Federation of Gynecology and Obstetrics. Furthermore, a highly significant inverse correlation was observed between CD44v expression and preoperative platelet count. Urinary neopterin concentration, a marker of cell-mediated immunostimulation, did not differ between CD44v-positive and -negative ovarian cancer patients. Moreover, in seven ovarian carcinoma cell lines, modulation of CD44v expression was analyzed by living cell radioimmunoassay. Interferon-alpha, interferon-gamma, tumor necrosis factor, transforming growth factor-beta, all-trans retinoic acid and cisplatin did not affect CD44v expression.

Tumor necrosis factor (TNF)-dependent shedding of the p55 TNF receptor in a baboon model of bacteremia

We have tested the hypothesis that the tumor necrosis factor (TNF) plays a significant role in vivo in TNF receptor shedding and studied the release of TNF-binding protein 1 (TNF-BP1), the soluble fragment of the 55- to 60-kDa TNF alpha (TNF) receptor, in a baboon model of Escherichia coli bacteremia, using three different doses of bacteria in acute infection (8 h) experiments (n [animals] = 11) and a single dose in a subchronic infection (72 h) experiment. In the subchronic infection study, one group of animals (n = 6) was pretreated with a neutralizing murine monoclonal antibody to TNF (CB0006). Concentrations of TNF and TNF-BP1 in plasma were determined in specific, monoclonal antibody-based immunoassays. Untreated animals (n = 6) showed undetectable TNF concentrations (< 10 pg/ml at baseline), whereas TNF-BP1 levels in plasma were in the range of 2 ng/ml, similar to concentrations observed in humans. Infusion of bacteria resulted in a rapid, dose-dependent increase in plasma TNF concentrations that reached a maximal level after 2 h and returned to baseline within 6 h. TNF-BP1 concentrations also showed a dose-dependent increase to peak concentrations three- to fivefold above baseline within 2 h but, in contrast to TNF levels, remained significantly elevated for up to 48 h. In animals pretreated with antibody CB0006, circulating TNF was completely neutralized, and TNF-BP1 was significantly reduced. We conclude that TNF-BP1 is released in bacteremia and that release in vivo is partially dependent on the presence of TNF.

Expression of mutant p53 protein and CD44 variant proteins in colorectal tumorigenesis

Colorectal tumorigenesis evolves through a series of molecular genetic changes, providing putative markers for tumour progression. This study investigated the relation between expression of the tumour suppressor gene p53 and splice variants v5 and v6 of the cell adhesion molecule CD44 by immunohistochemistry on tissue samples of early adenomas (n = 12), late adneomas (n = 12), Dukes's A and B carcinomas (n = 21), and Dukes's C and D carcinomas (n = 22) and compared these results with expression of these proteins in normal colonic mucosa (n = 17). A statistically significant trend of increasing expression was seen for both p53 (p < 0.005) and CD44 variant exon v6 (p < 0.0005) in subsequent stages of this tumour progression model. High expression of CD44 v5 was seen in most colorectal neoplasms (83%-96%), independent of stage. A statistically significant correlation was present between p53 expression and expression of variant v6 of CD44 (p < 0.01). Both p53 expression and CD44 v6 expression in adenomas increased with the degree of dysplasia (p < 0.05). The results of this study show that mutant p53 protein and variant v6 of the CD44 glycoprotein are markers of tumour progression in colorectal cancer.

Proteins induced by recombinant equine interferon-beta 1 within equine peripheral blood mononuclear cells and polymorphonuclear neutrophilic granulocytes

Peripheral blood mononuclear cells (PBMC) and polymorphonuclear neutrophilic granulocytes (PMN) as well as embryonic equine dermal fibroblasts and the equine fibroblast line E. Derm which were used as controls, were treated with recombinant equine interferon-beta 1 (rEqIFN-beta 1) in vitro which induced the expression of different proteins in these cells. A 74 kDa protein was induced in PBMC and an 82 kDa protein was additionally found in the equine fibroblast E. Derm cell line following treatment with rEqFN-beta 1. Both proteins reacted with anti-mouse and anti-human Mx protein antisera in immunoblot tests. The 74 kDa and perhaps the 82 kDa components may thus represent equine 'Mxanalogous proteins'. The 74 kDa protein was only detected in PBMC of ten out of 20 horses examined. The induction of Mx protein in the horse by Type 1 interferon may therefore resemble that in the mouse, where Mx protein is involved in selective resistance to influenza virus. The influence of rEqIFN-beta 1 on protein expression in equine PBMC and PMN was monitored by metabolic labeling and 2-D gel electrophoresis. Proteins of 82, 74, 58 and 40 kDa were induced in PBMC following exposure to rEqIFN-beta 1. A constitutively expressed 35 kDa protein, however, was no longer demonstrable upon treatment with interferon. None of the proteins induced within PBMC was found in highly purified PMN treated with interferon. PMN exposed to rEqIFN-beta 1 synthesized four proteins in the range of 25 to 27 kDa. These proteins have not been described in interferon-treated PMN of any other species.

Kinetics of inhibition of replication of vesicular stomatitis virus in blood mononuclear cells of horses after in vitro and in vivo treatment with recombinant equine interferon-beta 1

Recombinant equine interferon-beta 1 (reqIFN-beta 1) induces an antiviral state in blood mononuclear cells (BMC) of horses. Maximal protection against replication of vesicular stomatitis virus is achieved 6 hours after treatment with IFN in vitro and in vivo. Duration of the protective effect depends on the dose of IFN in vitro and in vivo. Availability of reqIFN-beta 1 in cultures of BMC for up to 48 hours does not prolong the antiviral state. The protective effect on BMC after treatment with IFN has similar duration in vivo and in vitro. Monitoring of the effect of IFN in vivo is, thus, simplified because the antiviral state may be recorded by testing cells twice (ie, before and 6 hours after application of interferon). All further tests may be performed in vitro. Multiple administration of reqIFN-beta 1 do not prolong duration of the protective phases after each administration. Duration of the antiviral state depends only on the dose of reqIFN-beta 1.

Regulation of the expression of annexin VIII in acute promyelocytic leukemia

Annexin VIII is a calcium-dependent phospholipid-binding protein previously identified as a blood anticoagulant based on in vitro studies. However, the physiologic function of annexin VIII remains unknown. In acute promyelocytic leukemia (APL) the annexin VIII gene is highly expressed, but its expression is undetectable in the blasts of other acute leukemias. In the present investigation, we showed using the APL-derived NB4 cell line that expression of the annexin VIII gene is regulated at the transcription level during induced differentiation by all-trans retinoic acid (ATRA). The half-life of the annexin VIII mRNA is about 5 to 6 hours, as determined by using actinomycin D as a transcription inhibitor. Analysis of the expression of annexin VIII protein in NB4 cells and in APL samples showed a consistent expression of a predominant 36-kD protein and a weak 72-kD protein. After ATRA-induced differentiation of NB4 cells, the annexin VIII protein level reduced gradually, but a detectable level persisted even after 4 days of induction. Because annexin VIII mRNA becomes undetectable after 48 hours of ATRA induction, this result indicates that annexin VIII is a relatively stable protein. A multiple tissue Northern blot analysis was performed, and we found that annexin VIII is normally expressed in the placenta and the lung. Cellular localization of the annexin VIII protein was determined by immunofluorescence staining and subcellular fractionation. These results indicated that annexin VIII is predominantly localized to the plasma membrane. The annexin VIII is neither an extracellular protein nor associated with the cell surface suggesting that it does not play a role in blood coagulation in vivo. The plasma membrane localization and its property as a phospholipase inhibitor suggests that annexin VIII may have a role in the signal transduction pathway in the APL cells.

Expression of CD44 splice variants during lymphocyte activation and tumor progression

Recently, splice variants of CD44 have been described that confer metastatic potential to non-metastasizing rat pancreatic carcinoma and sarcoma cell lines. Using antibodies against variant CD44 (CD44v) sequences, we have examined the expression of variant CD44 glycoproteins on human lymphoid cells and tissues and in colorectal neoplasia. Lymphohematopoietic cells express low levels of CD44v glycoproteins. During the process of lymphocyte activation in vitro and in vivo, expression of CD44v glycoproteins is transiently upregulated. The reaction pattern of various antibodies indicates that these CD44 variants contain the domain encoded by exon v6, which is part of the variant that confers metastatic capability. In human colorectal neoplasia we observed overexpression of CD44 splice variants in all invasive carcinomas. Already at early stages of colorectal tumor progression exon v5 epitopes were overexpressed. Tumor progression was strongly related to expression of CD44 isoforms containing exon v6 encoded domains. The findings establish CD44 variants as tumor progression markers in colorectal cancer.

Expression of CD44 variant proteins in human colorectal cancer is related to tumor progression

Specific CD44 variant glycoproteins are overexpressed at particular stages of colorectal tumor progression. Some variants of the CD44 glycoprotein without exon v6 sequences appear at the earliest stage of tumorigenesis, i.e., in early adenomas. Expression of variants containing exon v6 sequences is largely restricted to the advanced stages of tumor development and in addition is more prevalent and intense in metastatic (Dukes C/D) than in nonmetastatic (Dukes A/B) carcinomas. The observation that CD44 variants containing a protein domain of CD44 that confers full metastatic potential to rat carcinoma and sarcoma cell lines is increasingly expressed during colorectal tumor progression indicates that this domain may have an important role in tumor progression and metastasis in humans. Information on v6 expression, which can be obtained by routine immunohistochemistry, may prove of important prognostic value, particularly in carcinomas (Dukes A and B) that have not yet given rise to detectable metastases.

CD44 splice variants: expression during lymphocyte activation and tumor progression

A recently described splice variant of CD44 has been shown to confer metastatic potential to non-metastasizing rat pancreatic carcinoma and sarcoma cell lines. Using antibodies raised against a bacterial fusion protein encoded by variant CD44 sequences, we have explored the expression of variant CD44 glycoproteins in human lymphoid cells and tissues, in non-Hodgkin's lymphomas, and in colorectal neoplasia. Normal lymphohematopoietic cells express barely detectable low levels of variant CD44 glycoproteins, while T lymphocytes, upon activation by mitogen or antigen, transiently upregulate expression of specific CD44 variant glycoproteins. The reaction pattern of various antibodies indicates that these CD44 variants contain the domain encoded by exon v6, which is part of the variant that in the rat confers metastatic capability. Interestingly, overexpression of v6 was also found in several aggressive, but not in low-grade, non-Hodgkin's lymphomas (NHL). In human colorectal neoplasia we also observed strong overexpression of CD44 splice variants in all invasive carcinomas and carcinoma metastasis. Interestingly, focal expression was already observed in adenomatous polyps, expression being related to areas of dysplasia. The findings establish CD44 variants as tumor progression markers in colorectal cancer.

Activated human lymphocytes and aggressive non-Hodgkin's lymphomas express a homologue of the rat metastasis-associated variant of CD44

A recently described splice variant of CD44 expressed in metastasizing cell lines of rat tumors, has been shown to confer metastatic potential to nonmetastasizing rat pancreatic carcinoma and sarcoma cell lines. Using antibodies raised against a bacterial fusion protein encoded by variant CD44 sequences, we have explored the expression of variant CD44 glycoproteins on human lymphoid cells and tissues and on non-Hodgkin's lymphomas. Normal lymphohematopoietic cells express barely detectable low levels of variant CD44 glycoproteins, whereas T lymphocytes, upon activation by mitogen or antigen, transiently upregulate expression of specific CD44 variant glycoproteins. The reaction pattern of various antibodies indicates that these CD44 variants contain the domain encoded by exon v6, which is part of the variant that in the rat confers metastatic capability. It is interesting that overexpression of v6 was also found in several aggressive, but not low-grade, non-Hodgkin's lymphomas.

Natural human tumor necrosis factor beta (lymphotoxin). Variable O-glycosylation at Thr7, proteolytic processing, and allelic variation

Natural human tumor necrosis factor beta (TNF-beta) purified from supernatants of a human B-lymphoblastoid cell line was found to be heterogeneous in molecular mass, with seven components resolved by gel electrophoresis. All components are N-glycosylated at Asn62; N-glycosylation does not contribute to heterogeneity. In addition, part of the molecules are O-glycosylated at Thr7; O-glycosylation is heterogeneous due to variable decoration with neuraminic acid. The four lower molecular mass forms are derived from the full-length protein by trypsin-like proteolytic cleavage in the N-proximal region; these clipped molecules lack O-linked carbohydrates. Two allelic variants differing in amino acid position 26 (threonine/asparagine) were identified.

"Discordant" influence of equine recombinant interferon-beta 1 on the cytotoxic capacity of equine polymorphonuclear neutrophils and peripheral blood mononuclear cells in vitro and in vivo

The influence of recombinant equine interferon-beta 1 (rEqIFN-beta 1) on mononuclear cells of peripheral blood (PBMC) and polymorphonuclear neutrophilic granulocytes (PMN) was tested under in vitro and ex vivo conditions. Treatment of equine PBMC with IFN in vitro enhanced the antibody-independent cytotoxicity (AICC) and antibody-dependent cytotoxicity (ADCC) while there was no significant effect on the cytotoxic capacity of PMN treated with rEqIFN-beta 1 in vitro. Ex vivo there was an increased capacity of AICC and ADCC upon single or multiple application of rEqIFN-beta 1 in PMN, only. Treatment with rEqIFN-beta 1 thus induced an increased cellular cytotoxicity in vitro and in vivo but in different populations of peripheral blood cells. In vivo rEqIFN-beta 1 causes a pronounced activation of PMN but not of PBMC as cytotoxic effector cells. This might be achieved indirectly, e.g., by cytokines produced by IFN-sensitive cells.

Constitutive production of interferon-alpha 2 by a human B-lymphoblastoid cell line

Human B-lymphoblastoid cell lines immortalized by Epstein-Barr virus constitutively produce low levels of acid-stable interferon (IFN) that differs in composition from IFN produced by the same cell type after virus induction. We use three approaches to study the constitutive IFN produced by the lymphoblastoid cell line, LuKII: (i) antiviral bioassays with a neutralizing monoclonal antibody; (ii) amino-terminal sequence analysis of the single protein obtained after purification of the IFN by immunoaffinity chromatography and reverse-phase HPLC; (iii) sequence analysis of cDNA clones obtained by screening a LuKII library with an IFN-alpha 2 probe. Our data show that more than 90% of the constitutive IFN results from expression of a single gene coding for IFN-alpha 2. The significance of these results is discussed.

Monitoring of effects induced by recombinant equine interferon-beta 1 in whole blood and separated fractions of peripheral blood of horses

Interferon is known to induce antiviral mechanisms and to exert immunoregulatory capacities on various cell types. The antiviral capacity of recombinant equine interferon-beta 1 (rEqIFN-beta 1) is most sensitively monitored by indirect quantitation of multiplication of vesicular stomatitis virus (VSV) in blood cells of horses. As few as 0.5 pg rEqIFN-beta 1/ml can be assessed by means of 90% reduction of VSV-replication in whole blood (w.b.) as well as in isolated mononuclear blood cells (MNC) in spite of individual variations. The immunoregulatory influence of 20-50 pg rEqIFN-beta 1/ml is sufficient to cause at least a 50% reduction of mitogen-induced lymphocyte proliferation in MNC, while higher concentrations are needed in w.b. Of the mitogens tested the best stimulation of proliferation on the equine lymphoid cells was obtained with staphylococcal enterotoxin B (SEB). Release of reactive oxygen species (ROS) from phagocytic cells in w.b. or from isolated polymorphonuclear cells (PMN) as monitored by chemiluminescence (CL) does not seem suitable for evaluation of rEqIFN-beta 1-induced immunoregulation as only very high rEqIFN-beta 1-concentrations (10(3)-10(4) pg/ml) result in a minute increase (up to 20%) of CL. Comparative studies on w.b. and isolated leukocyte fractions from identical specimens of individual horses suggest that monitoring of antiviral and distinct immunoregulatory capacities of rEqIFN-beta 1 can be performed on w.b. without loss of information and sensitivity as compared to isolated MNC.

Monoclonal antibodies to soluble human TNF receptor (TNF binding protein) enhance its ability to block TNF toxicity

A soluble extracellular fragment of the human 55-60 kDa tumor necrosis factor receptor (sTNF-R I), originally isolated from urine, binds both TNF-alpha and TNF-beta and blocks the activity of these cytokines in biological assays. Three monoclonal antibodies (mAbs) raised against sTNF-R I (TBP-1, -2 and -6) as well as a mAb developed by immunization with the intact receptor (H398) were analysed for their epitope specificities in ELISAs and for biological activity in cytotoxicity assays on murine L-M cells. TBP-2 and H398 bind to related epitopes on sTNF-R I; they compete with TNF-alpha for binding and block the protective effect of sTNF-R I in the bioassay. MAbs TBP-1 and TBP-6 recognize two further, independent epitopes; both bind sTNF-R I in the presence of an excess of TNF-alpha. Both TBP-1 and TBP-6 markedly enhance the ability of sTNF-R I to protect cells against the cytotoxic activities of TNF-alpha and TNF-beta, but have no activity in the absence of sTNF-R I. Fab fragments show much lower activity. We propose that the ability of certain mAbs to enhance the protective activity of sTNF-R is due to a steric hindrance phenomenon.

A method for the assay of "difficult" interferons exemplified with recombinant equine interferon-beta 1

We wished to assay recombinant equine interferon-beta 1 (rEqIFN-beta 1) but could not obtain satisfactory results with previously described methods. Therefore, we developed a yield-reduction assay, using primary horse peripheral blood mononuclear cells (PBMC) with vesicular stomatitis virus (VSV) for challenge, which proved consistently satisfactory and highly sensitive. It is suggested that this method of assay may be useful for IFNs from other animals where problems are encountered.

A monoclonal antibody-based enzyme immunoassay for quantitation of human tumor necrosis factor binding protein I, a soluble fragment of the 60 kDa TNF receptor, in biological fluids

Three hybridoma cell lines secreting monoclonal IgG antibodies specific for human tumor necrosis factor-binding protein I (TNF-BP I), the extracellular domain of the 60 kDa TNF receptor, were developed by fusion of spleen cells from mice immunized with TNF-BP I purified from urine. The antibodies recognize three different epitopes on TNF-BP I. Two of the antibodies were used to develop a two-site ('sandwich') enzyme immunoassay with horseradish peroxidase as the marker enzyme. The assay was able to measure TNF-BP I in serum, urine and cell culture supernatants with a sensitivity of about 200 ng/l and a precision better than 10%. TNF-BP I was detected in the serum of healthy individuals at a mean concentration of 2.1 +/- 1.0 micrograms/l (mean +/- standard deviation; range, 0.52-5.4 microgram/l, n = 42); no significant difference was seen in patients with chronic polyarthritis (2.3 +/- 0.79 micrograms/l; n = 15). Serum TNF-BP I was significantly elevated in patients with burns (6.5 +/- 1.7 micrograms/l; n = 10) and markedly increased in patients with renal failure (49 +/- 17 micrograms/l; n = 6). TNF-BP I was also detectable in urine from normal individuals (2.2 +/- 1.2 micrograms/l; range 0.78-4.3 micrograms/l; n = 16). Culture supernatants of several human tumor cell lines also contained TNF-BP I. The assay will be a useful tool to detect activation of the TNF receptor by the physiological ligands, TNF-alpha and TNF-beta, as well as transmodulation by other mediators in various pathological conditions.

Isolation and partial characterization of the human erythrocyte band 7 integral membrane protein

Monoclonal antibodies to the Mr 31,000 major integral membrane protein of the human erythrocyte band 7 region were used to identify the corresponding polypeptide chain and epitope-carrying fragments on immunoblots. Analysis of the erythrocyte membrane, membrane fractions, and cytosol revealed that the Mr 31,000 band 7 integral membrane protein is unique and not related to any of the other water-soluble or membrane-bound band 7 components. Cross-reacting proteins were identified in the membranes of other mammalian erythrocytes and in cell lines of epithelial and lymphoid origin. Proteolytic digestion of intact human erythrocytes or erythrocyte membranes demonstrated that the band 7 integral membrane protein has an intracellular domain larger than Mr 12,000; it does not have an extracellular one. One of the monoclonal antibodies was employed for the isolation of band 7 integral membrane protein by immunoaffinity chromatography; subsequent Edman degradation revealed a blocked N-terminus.

Human interferon omega 1: isolation of the gene, expression in Chinese hamster ovary cells and characterization of the recombinant protein

A gene encoding human interferon omega-1 (IFN-omega 1) was isolated from a cosmid library, sequenced and expressed in Chinese hamster ovary (CHO) cells under the control of an SV40-derived promoter/enhancer sequence. Culture supernatants of stably transfected cell clones contained biologically active IFN-omega 1 at concentrations up to 10 micrograms/l. Amplification of the expression vector containing a dhfr gene under methotrexate selection pressure resulted in yields up to 200 micrograms/l. Production of IFN-omega 1 was further enhanced 2- to 3-fold by propagation of the cells in the presence of n-butyrate. IFN-omega 1 was purified from culture supernatants by monoclonal antibody affinity chromatography. The resulting protein was at least 95% pure as determined by reverse-phase HPLC and size-exclusion HPLC. Sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed two bands of about the same intensity with apparent molecular masses of 24.5 and 22.5 kDa. Upon treatment with peptide:N-glycosidase F, both bands were shifted to lower molecular masses (20.5 and 18.5 kDa), indicating that CHO cell-derived IFN-omega 1 is glycosylated; Asn-78 was identified as the glycosylation site. Analysis of the carbohydrate moiety using glycosidases and lectins revealed the presence of biantennary complex oligosaccharides containing neuraminic acid. Amino acid sequencing showed that only about 40% of the molecules have the expected N-terminus, whereas the others carry two additional amino acids derived from the signal sequence. C-terminal amino acid sequencing using carboxypeptidase P demonstrated that the smaller form of the protein lacks nine amino acids. Disulfide bridges were shown to connect Cys residues 1 and 99 as well as 29 and 139, respectively, as in IFN-alpha. The specific antiviral activity of recombinant, glycosylated human IFN-omega 1 on human cells was 2.6 x 10(8) IU/mg, not significantly different from that of the authentic, human leukocyte-derived protein.

Natural human interferon-alpha 2 is O-glycosylated

Natural human interferon alpha 2 (IFN-alpha 2) was isolated from a preparation of partially purified human leucocyte IFN by monoclonal-antibody immunoaffinity chromatography. The purified protein had a specific activity of 1.5 x 10(8) i.u./mg; it was estimated to constitute 10-20% of the total antiviral activity of leucocyte IFN. N-Terminal amino-acid-sequence analysis identified the subspecies IFN-alpha 2b and/or IFN-alpha 2c, whereas IFN-alpha 2a was not detectable. The structure of natural IFN-alpha 2 was found to differ from that of its recombinant (Escherichia coli-derived) equivalent. First, reverse-phase h.p.l.c. showed that natural IFN-alpha 2 was significantly more hydrophilic then expected. Secondly, the apparent molecular mass of the natural protein determined by SDS/PAGE was higher than that of recombinant IFN-alpha 2; incubation under mild alkaline conditions known to eliminate O-linked carbohydrates resulted in a reduction of the apparent molecular mass to that of the recombinant protein. On sequence analysis of proteolytic peptides, Thr-106 was found to be modified. These results suggested that Thr-106 of natural IFN-alpha 2 carries O-linked carbohydrates. Reverse-phase h.p.l.c. as well as SDS/PAGE of natural IFN-alpha 2 showed that glycosylation is heterogeneous. For characterization of the carbohydrate moieties, the protein was treated with neuraminidase and/or O-glycanase and analysed by gel electrophoresis; in addition, glycopeptides obtained by proteinase digestion and separated by h.p.l.c. were characterized by sequence analysis and m.s. Further information on the composition of the glycans was obtained by monosaccharide analysis. The results indicate that natural IFN-alpha 2 contains the disaccharide galactosyl-N-acetylgalactosamine (Gal-GalNAc) linked to Thr-106. In part of the molecules, this core carbohydrate carries (alpha-)N-acetylneuraminic acid, whereas a disaccharide, probably N-acetyl-lactosamine, is bound to Gal-GalNAc in another proportion of the protein. Further glycosylation isomers are present in small amounts. As IFN-alpha 2 is the only IFN-alpha species with a threonine residue at position 106, it may represent the only O-glycosylated human IFN-alpha protein.

Production of tumor necrosis factors alpha and beta by human mononuclear leukocytes stimulated with mitogens, bacteria, and malarial parasites

Tumor necrosis factors alpha and beta (TNF-alpha and TNF-beta) are multifaceted polypeptide cytokines which may mediate some of the significant changes in cellular homeostasis which accompany the invasion of the mammalian host by viruses, bacteria, and parasites. Although it is well established that bacterial lipopolysaccharide is a potent inducer of TNF-alpha, there is still very little known of the types of agents which can trigger the production of TNFs in mononuclear leukocytes. Using an enzyme-linked immunosorbent assay for measuring TNF-alpha and TNF-beta, we examined the capacity of various T-lymphocyte and beta-lymphocyte mitogens as well as microbial components to stimulate production of these cytokines in culture. The mitogens phytohemagglutinin, concanavalin A, and pokeweed mitogen induced production of both TNF-alpha and TNF-beta, while whole-killed Staphylococcus aureus and Bordetella pertussis, like lipopolysaccharide, were potent inducers of TNF-alpha but failed to stimulate TNF-beta production. TNF-alpha production was detectable within 1 h after stimulation, while TNF-beta production was not detected until after 8 h of culture. The bacterial products tetanus toxoid, purified protein derivative, pertussis filamentous hemagglutinin, and pertussis toxin were all able to induce TNF-alpha and TNF-beta production. Disrupted (frozen-thawed) Plasmodium falciparum-infected erythrocytes were also potent inducers of TNF-alpha and TNF-beta. The results demonstrated that a wide variety of microbial components are inducers of TNF-alpha. Some may not only be more effective than lipopolysaccharide but can also induce TNF-beta production. Furthermore, evidence is presented showing that TNF-beta but not TNF-alpha production correlates with lymphoproliferation.

Molecular cloning and expression of human and rat tumor necrosis factor receptor chain (p60) and its soluble derivative, tumor necrosis factor-binding protein

Tumor necrosis factor-alpha (TNF-alpha), a protein released by activated macrophages, is involved in a wide variety of human diseases including septic shock, cachexia, and chronic inflammation. TNF binding protein (TNF-BP), a glycoprotein with high affinity to TNF-alpha isolated from urine, acts as an inhibitor of TNF-alpha by competing with the cell-surface TNF receptor. We report here the partial amino acid sequencing of human TNF-BP as well as the isolation, sequence, and expression of cDNA clones encoding a human and rat TNF receptor. The calculated Mr of the mature human and rat TNF receptor chains is 47,526 and 48,072, respectively. The extracellular ligand binding domain represents the soluble TNF-BP which is released by proteolytic cleavage. TNF-BP contains 24 cysteine residues and three potential N-glycosylation sites and shows sequence homology to the extracellular portions of TNF-R p80 chain and nerve growth factor receptor. Transfection of the human TNF receptor cDNA into mammalian cells resulted in increased binding capacity for TNF-alpha and increased reactivity with a monoclonal antibody directed against the human TNF receptor chain p60. When a stop codon was introduced into the cDNA at the site corresponding to the carboxyl terminus of TNF-BP, transfected cells secreted a protein that reacted with antibodies raised against natural TNF-BP.

Highly sensitive enzyme immunoassays for antibodies to human tumor necrosis factor (TNF-alpha) and lymphotoxin (TNF-beta)

Two 'inverse sandwich' enzyme immunoassays (ELISAs) were developed for the detection and quantification of antibodies to human tumor necrosis factor (TNF-alpha) and lymphotoxin (TNF-beta), respectively. In these one-step assays, antibodies present in the sample linked antigen which had been covalently coupled to horseradish peroxidase to antigen bound to a solid phase (microtiter plates). The limits of detection of the assays were lower than those of neutralization bioassays; antibodies to TNF-alpha and TNF-beta being detected at concentrations as low as 2 ng/ml and 0.5 ng/ml, respectively, and no cross-reactivity was observed. The advantages of these ELISAs over other assay methods currently in use for the detection of antibodies include: (i) the convenience of the microtiter plate format and its suitability for testing large numbers of samples; (ii) the absence of radioactive tracers and precipitation steps; (iii) the high stability of the reagents; (iv) the avoidance of second antibodies and, thus, the possibility of testing samples from various species without modification of the assay and (v) the ability to detect low-affinity antibodies due to the absence of competitive reactions. The assays may be used without modification for the detection of antibodies in serum samples from both man and laboratory animals as well as in other samples such as hybridoma supernatants.

Highly sensitive enzyme immunoassay for human lymphotoxin (tumor necrosis factor beta) in serum

We have developed a rapid, simple and highly sensitive 'sandwich' enzyme immunoassay (ELISA) for the detection and quantification of human lymphotoxin (= tumor necrosis factor beta) in serum. The assay, performed in microtiter plates, employs two monoclonal murine antibodies able to neutralize the cytotoxic activity of lymphotoxin. In a one-step procedure, antibody LTX-21 (IgG2b) coated on to the solid phase captures antigen present in the sample; subsequently antibody LTX-22 (IgG1), covalently coupled to horseradish peroxidase, labels the bound antigen. The assay is able to detect lymphotoxin spiked into human serum in concentrations as low as 7 pg/ml, whereas human tumor necrosis factor alpha does not cross-react even at 10(7)-fold higher concentrations. Only biologically active protein is recognized by the antibodies, since inactivation of lymphotoxin measured by bioassay results in a parallel decrease in immunoreactivity. Natural, glycosylated lymphotoxin shows the same reactivity as recombinant, unglycosylated protein. The assay will be useful for the quantification of endogenous human lymphotoxin in serum, other body fluids, and culture supernatants of human cells, and can also be used to monitor levels of recombinant human lymphotoxin in animal studies and clinical trials.

Purification and characterization of natural human interferon omega 1. Two alternative cleavage sites for the signal peptidase

Human interferon omega 1 (IFN-omega 1 = IFN-alpha II1) is a recently discovered protein structurally related to IFN-alpha and -beta; the biological activities of IFN-omega 1 and its physiological role are not known to date. We have purified IFN-omega 1 from preparations of human leukocyte IFN, derived from peripheral blood leukocytes induced with Sendai virus, by two sequential cycles of monoclonal antibody affinity chromatography. The resulting protein was at least 95% pure as determined by reverse-phase high performance liquid chromatography and showed an Mr of 24,500 upon sodium dodecyl sulfate-gel electrophoresis (theoretical Mr, 19,984). Amino acid sequence analysis revealed that only about 40% of the molecules have the NH2 terminus expected on the basis of the sequence similarity to IFN-alpha, whereas the others contain two additional amino acids. This difference probably results from variable cleavage of the pre-protein by the signal peptidase. No evidence for COOH-terminal heterogeneity was found. Essentially all IFN-omega 1 molecules are glycosylated; enzymatic deglycosylation resulted in a reduction of the Mr to 20,500. Experiments using several plant lectins indicated the presence of biantennary complex oligosaccharides containing neuraminic acid. Two major peaks were observed upon chromatofocusing, with isoelectric points of 8.1 and 8.5. The specific antiviral activity of purified IFN-omega 1 assayed on human cells was determined to be 2.7 x 10(8) IU/mg, similar to that of other human class I IFNs; potent antiviral activity was also observed on cells of bovine and ovine but not of equine or murine origin.

Recombinant equine interferon-beta 1: purification and preliminary characterization

Equine interferon-beta 1 (EqIFN-beta 1) was purified from extracts of recombinant Escherichia coli by sequential chromatography on hydroxylapatite, anion-, and cation-exchangers. The resulting protein was greater than 98% pure as determined by sodium dodecylsulfate gel electrophoresis, gel permeation HPLC, and reverse-phase HPLC. Amino-terminal amino acid sequencing revealed that essentially all molecules contained an additional amino-terminal methionine. The specific antiviral activity of EqIFN-beta 1 determined on equine dermal fibroblasts challenged with vesicular stomatitis virus (VSV) was approximately 5 X 10(8) U/mg. Less than 0.001% of this activity was observed in antiviral assays using human (A549), murine (L-M), ovine (SCP), or bovine (MDBK and BT) cells challenged with VSV or encephalomyocarditis virus. A series of monoclonal murine IgG antibodies were developed which neutralize the antiviral activity of EqIFN-beta 1. None of these antibodies nor rabbit antiserum to EqIFN-beta 1 were able to neutralize human IFN-beta; antiserum to human IFN-beta did not neutralize EqIFN-beta 1. Two of the monoclonal antibodies were used to establish a rapid one-step solid-phase enzyme immunoassay for EqIFN-beta 1.

Monoclonal antibodies and enzyme immunoassays specific for human interferon (IFN) omega 1: evidence that IFN-omega 1 is a component of human leukocyte IFN

Four hybridoma cell lines secreting monoclonal IgG antibodies to human interferon (IFN) omega 1 (= IFN-alpha II 1) were developed, using spleen cells of mice immunized with IFN-omega 1 and/or a novel hybrid interferon, IFN-omega 1/alpha 2. All antibodies (OMG-2, -4, -5, and -7) neutralize the antiviral activity of IFN-omega 1 and show distinct patterns of reactivity with the hybrid proteins, IFN-omega 1/alpha 2 and IFN-alpha 2c/omega 1. However, none of the antibodies is able to neutralize human IFN-alpha, confirming earlier observations that IFN-omega 1 and IFN-alpha are antigenically unrelated. The epitope specificities of the antibodies were further characterized in direct and competitive enzyme immunoassays (ELISAs). All binary antibody combinations were tested for their suitability for a two-site ("sandwich") ELISA for IFN-omega 1, using horse radish peroxidase as the marker enzyme. A configuration employing OMG-2 for antigen capture and OMG-7 as the detector antibody resulted in the highest assay sensitivity (approximately 10 pg IFN-omega 1/ml) and was studied further. This one-step assay is highly specific for IFN-omega 1 and does not recognize human IFN-alpha, -beta, and -gamma, thus allowing for determination of IFN-omega 1 levels in natural mixtures of human IFNs. Using this ELISA, it was found that IFN-omega 1 is present in IFN preparations derived from virus-induced human peripheral blood leukocytes and may constitute as much as 15% of the total leukocyte IFN activity. IFN-omega 1 was also detected at somewhat lower levels in preparations of human "lymphoblastoid" IFN.