Control of stem cell response and bone growth on biomaterials by fully non-peptidic integrin selective ligands.

In this communication we report that anchoring αvß3 or α5ß1 integrin-selective RGD peptidomimetics to titanium efficiently tunes mesenchymal stem cell response in vitro and bone growth in rat calvarial defects. Our results demonstrate that this molecular chemistry-derived approach could be successful to engineer instructive coatings for orthopedic applications.

Class I major histocompatibility complex enhancement by recombinant leukocyte interferon in the peripheral blood mononuclear cells and plasma of melanoma patients.

In vivo administration of escalation doses of recombinant alpha-interferon (IFN-alpha) during a phase I trial in malignant melanoma patients caused dose-dependent increases in the mRNA accumulation, synthesis, steady state cellular content, and plasma membrane expression of class I major histocompatibility complex molecules in peripheral blood mononuclear cells. In addition, circulating levels of class I molecules were also enhanced. These findings show that (a) antigenic enhancement by biomodifiers may occur in vivo, in humans and (b) the mechanism of class I major histocompatibility complex enhancement by IFN-alpha is similar in vitro and in vivo. Furthermore, because peripheral blood mononuclear cells of different melanoma patients display different susceptibility to IFN-alpha, the entity of their antigenic modulation may represent a useful parameter to evaluate the efficacy of different therapeutic regimens and/or assess the individual susceptibility to the molecular changes induced by IFN-alpha.

Low prevalence of selective human leukocyte antigen (HLA)-A and HLA-B epitope losses in early-passage tumor cell lines.

The down-regulation of human leukocyte antigen (HLA) class I molecules, especially the selective down-regulation of certain allelic products, is believed to represent a major mechanism of tumor escape from immune surveillance. In the present report, an original approach is described to precisely evaluate and classify HLA class I epitope losses in 30 cancer patients with malignant melanoma and lung, breast, endometrium, ovary, and colon carcinoma tumors. Early-passage tumor cell lines were established in culture from the corresponding metastatic tumor lesions obtained in each patient. Both the cell lines and the tumor lesions were compared, in their HLA-A and -B expression, to the peripheral blood mononuclear cells (PBMCs) obtained from the same patient (autologous PBMCs). On the basis of HLA-genotyping data, the appropriate monoclonal antibodies identifying mono- and poly-morphic HLA-A and HLA-B epitopes were selected from a panel of 34 antibodies for a total of 24 testable alleles. The selected antibodies were used not only in immunohistochemical assays on cryostatic tumor sections and cytospins of PBMCs but also in quantitative, sensitive flow cytometry assays on early-passage tumor cells and PBMC suspensions. With this latter method, a low overall HLA expression was detected in 26 tumor cell explants and a complete, generalized HLA-A, HLA-B, HLA-C loss in the remaining 4 cases. However, no complete, selective loss of any of the 45 tested HLA-A and HLA-B allomorphs was observed. Sequences from all of the HLA class I alleles could be detected at the genomic DNA level in tumor cells and tissues. At variance from the literature and the results of immunohistochemical experiments performed in parallel on the corresponding tumor lesions, the relative proportions of the various HLA epitopes were relatively preserved in each early-passage cell line/PBMC pair, and selective increases, rather than decreases, in the expression of polymorphic HLA epitopes had the highest prevalence and greatest magnitude. Our data suggest an alternative tumor stealth strategy in which up- and down-regulation are equally important. This alternative model of tumor-host interaction better fits the available models of tumor cell recognition by CTLs and natural killer cells bearing activatory and inhibitory receptors for HLA-A, HLA-B, HLA-C molecules.

Membrane compartmentalization of melanosomal gp75.

A melanosomal integral membrane glycoprotein of 75 kD (gp75) has been previously identified as the human homologue of the product specified by the murine brown locus. We presently report that this molecule may be susceptible to limited proteolysis and extrinsic radioiodination in intact, live cells. Consequently, it is suggested that its cellular location might include the plasma membrane and/or a cellular compartment easily accessible to proteases and to chemically catalyzed vectorial iodination. This is of interest in view of the potential applicative value of gp75 as a target for the radioimmunoscintography of melanoma lesions.

Production and characterization of the murine monoclonal antibody 2G10 to a human T4-tyrosinase epitope.

Employing as immunogen a short-term passaged, highly pigmented human melanoma cell line, we have produced the murine MoAb 2G10 of the IgG1 isotype. The antibody immunoprecipitated from 35S-methionine and 3H-glucosamine metabolically labeled human melanoma cells with a single-chain glycoprotein of 75 kD molecular weight. No such molecule could be precipitated from murine melanomas. To further investigate the fine specificity of the MoAb, immunochemical and immunohistochemical studies were performed. These studies demonstrated that MoAb 2G10 binds a significant fraction of tyrosinase activity from cell lysates, completely immunodepletes soluble cell extract of T4-tyrosinase molecules, and produces immunostaining patterns superimposable on those obtained with anti-T4-tyrosinase antibodies. Thus, MoAb 2G10 appears to recognize a human-specific determinant carried by either T4-tyrosinase or a closely related molecule. The functional relevance of this epitope remains to be evaluated.

Characterisation and protective capacity of monoclonal antibodies elicited in mice against protein epitopes of antibiotic-exposed Escherichia coli.

The binding capacity and the protective activity of three monoclonal antibodies (MAbs)-ARM 1-4, ARM 1-7 and ARM 2-2-obtained from spleen cells of mice immunised with Escherichia coli O6:K-pre-treated with sub-MIC of aztreonam were studied. The MAbs belonged to IgG1 isotype and showed different reactivity toward protein epitopes of E. coli in an immunoblotting assay. ARM 1-4 recognised epitopes on molecules of 30 kDa and 40 kDa. ARM 1-7 identified an epitope of a molecule of 41 kDa, and ARM 2-2 recognised epitopes of molecules of 15 kDa and 41 kDa. In ELISA the MAbs cross-reacted with E. coli O7:K-, E. coli O111:B4 and E. coli O128:K- with different binding affinity. Furthermore, the MAbs showed complement-dependent bactericidal activity. The MAbs displayed different protective capacities when given to mice 90 min before lethal challenges with 2 x LD50, 4 x LD50 and 8 x LD50 of E. coli strains. In all but one instance (ARM 1-4 versus E. coli O7:K-) it was not possible to correlate protective capacity with binding affinity of a MAb to a given bacterial cell. Therefore, the epitopes recognised by the MAb may be more closely associated with bacterial virulence than in binding to the bacterial cell.

Murine monoclonal antibody elicited with antibiotic-exposed Escherichia coli exerts protective capacity in experimental bacterial infections.

Escherichia coli pre-exposed to a sub-minimal inhibitory concentration (sub-MIC) of several antibiotics elicits an enhanced humoral response which is protective against challenges with untreated homologous and heterologous bacteria. To characterise the specificity of this response we produced murine monoclonal antibodies (MAbs) to aztreonam-treated E. coli O6:K-. This resulted in the identification of MAb MT 1F, of isotype IgG1, that recognised a 12-kDa protein component of the untreated bacterial cells. After passive transfer, the MAb displayed protective activity in mice infected with lethal doses of live E. coli O6:K- and E. coli O111:B4. In ELISA experiments the MAb cross-reacted with structures located on whole cells of E. coli O6:K-, E. coli O111:B4, E. coli J5 and Salmonella minnesota Re595 and it also exerted a bactericidal activity against live E. coli O6:K-. The modifications induced by antibiotic treatment may unmask bacterial epitopes that may elicit the production of MAbs endowed with protective capacity.

Saporin 6 conjugated to monoclonal antibody selectively kills human melanoma cells.

A novel human melanoma specific immunotoxin is described, which has been produced utilizing the murine monoclonal antibody (mAb) Ep2, IgG2a isotype, recognizing an epitope of the glycoprotein/proteoglycan high molecular weight-melanoma associated antigen. mAb Ep2 has been chemically conjugated by a disulphide bond, using the bifunctional reagent SPDP, to the plant toxin Saporin 6 (SAP) extracted from seeds of Saponaria officinalis. Cytotoxicity studies performed in vitro on melanoma cells have shown that Ep2/SAP immunotoxin efficiently kills antigen expressing cells and that its IC50 is approximately 1 x 10(-10) M, while not affecting the viability of antigen-negative melanoma cells at doses as high as 1 x 10(-7) M, therefore indicating a therapeutic index of Ep2/SAP immunotoxin higher than 1000. Kinetic studies have demonstrated that protein synthesis inhibition by Ep2/SAP is rapidly achieved, since a 90% reduction is observed within 3.1 h, and that this inhibitory activity is apparently first order with time. Furthermore, the cytotoxic activity of the immunoconjugate is not dependent, and is not influenced by, the presence in the culture medium of the lysosomotropic agent chloroquine.

Recombinant immune interferon down-regulates Ha-ras-1 proto-oncogene products in a human melanoma cell line.

The antiproliferative and antineoplastic effects of the interferons may result, at least in part, from changes in the expression and quantity of specific oncogene products. To explore this hypothesis we have determined the effect of interferons, including recombinant leukocyte (IFN-alpha), fibroblast (IFN-beta) and immune (IFN-gamma), on expression of the Ha-ras proto-oncogene in the human melanoma cell line Colo 38. While concentrations of up to 1000 U/ml of either IFN-alpha or IFN-beta did not affect the total amounts of Ha-ras products, IFN-gamma at concentrations ranging from 20 to 200 U/ml caused a dose- and time-dependent (48-96 hr) reduction (approximately 40%) in the accumulation of Ha-ras-1 mRNA and in the synthesis of the specific protein products. Downregulation of this proto-oncogene occurs prior to the antiproliferative effects of IFN-gamma and parallels similar IFN-gamma mediated changes in the expression of certain melanoma associated antigens. The present findings indicate that this experimental model may prove valuable in determining whether a direct relationship exists between the antiproliferative activity of specific interferons and the downregulation of oncogene expression.

Generation and characterization of the murine monoclonal antibody M-KID 2 to VLA-3 integrin.

Through the analysis of the antigenic phenotype of a recently established human renal carcinoma cell line (KJ29), we have demonstrated that alpha 3 subunit of the integrin family is selectively expressed by the plastic adherent cell subpopulation. Because of the scanty availability of monoclonal antibodies to this adhesion molecule, we have used KJ29 cell line as immunogen to raise novel murine monoclonal antibodies. We isolated an hybridoma secreting the mAb M-KID 2 of the IGg1k isotype that immunoprecipitates from intrinsically [35S]-Methionine labeled KJ29 cells, an heterodimer of 130/130 and 110/150 Kd, in reducing and nonreducing conditions respectively. This reactivity was completely abolished by immunodepletion of the cell extract with a polyclonal anti alpha 3 chain antiserum. Treatment of M-KID 2 immunoprecipitates with various solutions of pH ranging from 2 to 10.5, to dissociate alpha 3 from beta 1 chains, showed a retention of both alpha 3 beta 1 chains thus indicating that the epitope identified by mAb M-Kid 2 is likely to be constituted by the alpha 3 beta 1 heterodimer. Furthermore immunohistochemical studies on selected frozen and paraffin embedded tissues with mAb M-Kid 2 have provided staining pattern indicating the recognition of Vla-3. These findings demonstrate that mAb M-KID 2 can represent a valuable reagent for the study of Vla-3 integrin in normal and pathologic conditions.

Production and characterization of murine mAbs to the extracellular domain of human neu oncogene product GP185HER2.

The oncogene HER-2/neu encodes a transmembrane glycoprotein of 185 kDa (gp185HER-2) with tyrosine-kinase activity. Gene amplification and high levels of expression of gp185HER-2 have been found to correlate with poor clinical outcome in breast and ovarian carcinomas. Employing a somatic cell hybrid fusion protocol, which yields a high frequency production of hybridomas, we have analyzed the extent of the murine immune response to the gp 185 extracellular domain. In a single fusion experiment, using as immunogen NIH 3T3 cells expressing high levels of a transfected human HER-2 gene, we have generated mAbs, mainly of IgG1 isotype, displaying high affinity (10(7)-10(10) mol/L) to gp 185. Analysis of the epitope specificity has allowed the identification of five distinct groups of spatially related epitopes, each provided with different immunodominancy, and all resistant to formalin fixation. The use of inhibitor of N-linked glycosylation tunicamicyn has demonstrated that the mAbs bind to epitopes localized in the protein core of gp185HER-2. Because recent reports have shown that gp185HER-2 has a restricted expression in normal tissues and is homogenously detectable in metastatic foci of gp 185 + primary tumors, antibodies to this macromolecule, in addition to their prognostic value, may represent reagents for in vitro and in vivo diagnostic applications, as well as for the development of therapeutic strategies.

Antigenic modulation of metastatic breast and ovary carcinoma cells by intracavitary injection of IFN-alpha.

Antigenic modulation of major histocompatibility and tumour associated antigens was observed in neoplastic cells obtained from patients with pleural and abdominal effusions of breast and ovary carcinomas following a single intracavitary dose of 18 x 10(6) U recombinant IFN-alpha. This regimen resulted in antigenic modulation in seven out of 11 tested cases, suggesting a potential, although limited, responsiveness of at least a fraction of breast and ovary carcinoma cells to in situ biomodification with IFN-alpha.

Comprehensive analysis of photoreceptor gene expression and the identification of candidate retinal disease genes.

To identify the full set of genes expressed by mammalian rods, we conducted serial analysis of gene expression (SAGE) by using libraries generated from mature and developing mouse retina. We identified 264 uncharacterized genes that were specific to or highly enriched in rods. Nearly half of all cloned human retinal disease genes are selectively expressed in rod photoreceptors. In silico mapping of the human orthologs of genes identified in our screen revealed that 86 map within intervals containing uncloned retinal disease genes, representing 37 different loci. We expect these data will allow identification of many disease genes, and that this approach may be useful for cloning genes involved in classes of disease where cell type-specific expression of disease genes is observed.

Production and characterization of two immunotoxins specific for M5b ANLL leukaemia.

We describe the production and functional characterization of 2 monocytic-cell-lineage-specific immunotoxins constructed with saporin emitoxin (SAP) from Saponaria officinalis. Interest in the production of these immunotoxins, of possible clinical relevance, has been raised by the availability of 2 MAbs of high specificity for circulating monocytes and M5b ANLL, thus envisaging their potential use in bone-marrow purging. SAP emitoxin was selected on the basis of the low cytotoxicity in unconjugated form, as opposed to highly specific cytotoxicity and favourable pharmacokinetical properties in the conjugated form. SPDP conjugation produced immunotoxins which retained serological specificity and protein-synthesis-inhibitory activity. The 2 immunotoxins did not interfere with bone-marrow progenitor-cell growth in a CFU-GM colony assay. On the contrary, they were capable of killing monocytic cells selectively, as demonstrated in phenotypical and functional assays. Thus these 2 novel immunotoxins appear to be promising reagents in purging autologous bone marrow prior to transplantation in patients suffering from monocytic leukaemia.

Expression of the c-Kit receptor and its ligand SCF in non-small-cell lung carcinomas.

Increasing experimental evidence indicates that stem-cell factor (SCF) and its cognate receptor c-Kit may participate in the growth control of various solid human malignancies. In the present study, we have extended this analysis to non-small-cell lung carcinomas (NSCLC). The results of an immunohistochemical analysis demonstrated that c-Kit/SCF are expressed by 30%/58% of adenocarcinomas, 15%/37% of squamous-cell carcinomas and by 40%/30% of undifferentiated carcinomas respectively. In 15% of primary and 18% of metastatic tumors, co-expression of the receptor and its ligand was documented. Western-blot assays of tumor extracts demonstrated that both molecules exhibit features of the normal receptor and ligand. Since biologically active SCF is physiologically present in the bloodstream, our data indicate that SCF is available to c-kit-expressing NSCLC cells via autocrine, paracrine or endocrine mechanisms. Thus activation of c-Kit in these tumors may contribute critically to their progression.

Biosynthesis of HLA-C heavy chains in melanoma cells with multiple defects in the expression of HLA-A, -B, -C molecules.

Recent investigations have shown that malignant transformation may down-regulate the expression of class I HLA molecules, beta2-microglobulin (beta2m) and members of the antigen-processing machinery. In the present study, we HLA-genotyped and identified at a biochemical level the three (HLA-A25, -B8, -Cw7) class I alleles expressed by the previously described [D'Urso CM et al (1992) J Clin Invest 87: 284-292] beta2m-defective human melanoma FO-1 cell line and tested their ability to interact with calnexin, calreticulin and the TAP (transporter associated with antigen processing) complex. All these alleles were found to bind calnexin, but not calreticulin or the poorly expressed TAP complex, both in parental and beta2m-transfected FO-1 cells, demonstrating a complex defect of class I expression in FO-1 cells. In these conditions, Cw7 heavy chains interacted with calnexin more strongly than A25 and B8, and preferentially accumulated in the endoplasmic reticulum, in both a calnexin-associated and a calnexin-free form. In addition, they could be transported to the cell surface at low levels even in the absence of beta2m, without undergoing terminal glycosylation. These results establish a parallel between HLA-C and the murine Db and Ld molecules which have been found to be surface expressed and functional in beta2m-defective cells. They also demonstrate distinctive features of HLA-C molecules. We propose that the accumulation of several assembly intermediates of HLA-C might favour the binding of peptide antigens not readily bound by HLA-A and -B molecules in neoplastic cells with suboptimal class I expression.

Frequency of somatic and germ-line mosaicism in retinoblastoma: implications for genetic counseling.

Although mosaicism can have important implications for genetic counseling of families with hereditary disorders, information regarding the incidence of mosaicism is available for only a few genetic diseases. Here we describe an evaluation of 156 families with retinoblastoma; the initial oncogenic mutation in the retinoblastoma gene had been identified in these families. In 15 ( approximately 10%) families, we were able to document mosaicism for the initial mutation in the retinoblastoma gene, either in the proband or in one of the proband's parents. The true incidence of mosaicism in this group of 156 families is probably higher than our findings indicate; in some additional families beyond the 15 we identified, mosaicism was likely but could not be proven, because somatic or germ-line DNA from key family members was unavailable. Germ-line DNA from two mosaic fathers was analyzed: in one of these, the mutation was detected in both sperm and leukocyte DNA; in the other, the mutation was detected only in sperm DNA. Our data suggest that mosaicism is more common than is generally appreciated, especially in disorders such as retinoblastoma, in which a high proportion of cases represent new mutations. The possibility of mosaicism should always be considered during the genetic counseling of newly identified families with retinoblastoma. As demonstrated here, genetic tests of germ-line DNA can provide valuable information that is not available through analysis of somatic (leukocyte) DNA.

HLA-A, -B, -C genotyping and expression in human nonlymphoid tumor cell lines.

A combination of molecular genotyping and protein biochemistry methods was used to assess the HLA-A, -B, -C genotyping and expression of six tumor cell lines. Four cell lines had been previously HLA typed by conventional serologic methods. Two could not be typed by serology because deficient in the surface expression of HLA-A, -B, -C molecules. As shown herein, all the 25 alleles carried by the six tested cell lines were typed at the DNA level. In addition, discrepancies between the previous serologic and the present DNA typing results were detected in 9 of the 21 tested serologic specificities. Typing at the protein level by isoelectric focusing and allele-specific monoclonal antibodies confirmed the DNA typing data. Our results exemplify the limits of the serologic typing procedures and demonstrate that molecular methods are highly desirable to conduct functional experiments and identify HLA losses in neoplastic cells at single allele level.