Antibody-drug conjugate targeting CD46 eliminates multiple myeloma cells

Multiple myeloma is incurable by standard approaches because of inevitable relapse and development of treatment resistance in all patients. In our prior work, we identified a panel of macropinocytosing human monoclonal antibodies against CD46, a negative regulator of the innate immune system, and constructed antibody-drug conjugates (ADCs). In this report, we show that an anti-CD46 ADC (CD46-ADC) potently inhibited proliferation in myeloma cell lines with little effect on normal cells. CD46-ADC also potently eliminated myeloma growth in orthometastatic xenograft models. In primary myeloma cells derived from bone marrow aspirates, CD46-ADC induced apoptosis and cell death, but did not affect the viability of nontumor mononuclear cells. It is of clinical interest that the CD46 gene resides on chromosome 1q, which undergoes genomic amplification in the majority of relapsed myeloma patients. We found that the cell surface expression level of CD46 was markedly higher in patient myeloma cells with 1q gain than in those with normal 1q copy number. Thus, genomic amplification of CD46 may serve as a surrogate for target amplification that could allow patient stratification for tailored CD46-targeted therapy. Overall, these findings indicate that CD46 is a promising target for antibody-based treatment of multiple myeloma, especially in patients with gain of chromosome 1q.

Altered expression of autoimmune regulator in infant down syndrome thymus, a possible contributor to an autoimmune phenotype

Down syndrome (DS), caused by trisomy of chromosome 21, is associated with immunological dysfunctions such as increased frequency of infections and autoimmune diseases. Patients with DS share clinical features, such as autoimmune manifestations and specific autoantibodies, with patients affected by autoimmune polyendocrine syndrome type 1. Autoimmune polyendocrine syndrome type 1 is caused by mutations in the autoimmune regulator (AIRE) gene, located on chromosome 21, which regulates the expression of tissue-restricted Ags (TRAs) in thymic epithelial cells. We investigated the expression of AIRE and TRAs in DS and control thymic tissue using quantitative PCR. AIRE mRNA levels were elevated in thymic tissue from DS patients, and trends toward increased expression of the AIRE-controlled genes INSULIN and CHRNA1 were found. Immunohistochemical stainings showed altered cell composition and architecture of the thymic medulla in DS individuals with increased frequencies of AIRE-positive medullary epithelial cells and CD11c-positive dendritic cells as well as enlarged Hassall's corpuscles. In addition, we evaluated the proteomic profile of thymic exosomes in DS individuals and controls. DS exosomes carried a broader protein pool and also a larger pool of unique TRAs compared with control exosomes. In conclusion, the increased AIRE gene dose in DS could contribute to an autoimmune phenotype through multiple AIRE-mediated effects on homeostasis and function of thymic epithelial cells that affect thymic selection processes.

Excessive amounts of mu heavy chain block B-cell development

Antigen-independent B-cell development occurs in several stages that depend on the expression of Ig heavy and light chain. We identified a line of mice that lacked mature B cells in the spleen. This mouse line carried approximately 11 copies of a transgene of the murine heavy chain constant region locus, and B-lineage cells expressed excessive amounts of the intracellular μ heavy chain. B-cell development failed in the bone marrow at the pro/pre B-cell transition, and examination of other lines with various copy numbers of the same transgene suggested that deficiencies in B-cell development increased with increased transgene copy number. Expression of a transgenic (Tg) light chain along with the Tg μ heavy chain led to minimal rescue of B-cell development in the bone marrow and B cells in the spleen. There are several potential mechanisms for the death of pro/pre B cells as a consequence of excess heavy chain expression.

Autoimmunity and Klinefelter's syndrome: when men have two X chromosomes

Similar to other autoimmune diseases, systemic lupus erythematosus (SLE) predominately affects women. Recent reports demonstrate excess Klinefelter's among men with SLE and a possible under-representation of Turner's syndrome among women with SLE as well as a case report of a 46,XX boy with SLE. These data suggest that risk of SLE is related to a gene dose effect for the X chromosome. Such an effect could be mediated by abnormal inactivation of genes on the X chromosome as has been demonstrated for CD40L, or by genetic polymorphism as has been demonstrated for Xq28. On the other hand, a gene dose effect could also be mediated by a gene without an SLE-associated polymorphism in that a gene that avoids X inactivation will have a higher level of expression in persons with two X chromosomes.

Shared signaling networks active in B cells isolated from genetically distinct mouse models of lupus

Though B cells play key roles in lupus pathogenesis, the molecular circuitry and its dysregulation in these cells as disease evolves remain poorly understood. To address this, a comprehensive scan of multiple signaling axes using multiplexed Western blotting was undertaken in several different murine lupus strains. PI3K/AKT/mTOR (mTOR, mammalian target of rapamycin), MEK1/Erk1/2, p38, NF-kappaB, multiple Bcl-2 family members, and cell-cycle molecules were observed to be hyperexpressed in lupus B cells in an age-dependent and lupus susceptibility gene-dose-dependent manner. Therapeutic targeting of the AKT/mTOR axis using a rapamycin (sirolimus) derivative ameliorated the serological, cellular, and pathological phenotypes associated with lupus. Surprisingly, the targeting of this axis was associated with the crippling of several other signaling axes. These studies reveal that lupus pathogenesis is contingent upon the activation of an elaborate network of signaling cascades that is shared among genetically distinct mouse models and raise hope that targeting pivotal nodes in these networks may offer therapeutic benefit.

Outliers in RhD membrane integration are explained by variant RH haplotypes

BACKGROUND

Variations in a multipass transmembrane protein may affect its membrane integration. To study this effect, the systematic molecular characterization of variant D antigen density is a suitable model. Unlike most other membrane proteins, the expression of the D antigen is often determined by a single allele, because it occurs frequently in hemizygous form.

STUDY DESIGN AND METHODS

The D antigen density distribution of 530 CcDee, 475 ccDEe, and 514 ccDee random samples was established by flow cytometry. The molecular bases of samples with D antigen densities outside a bell-shaped peak was investigated.

RESULTS

The antigen densities of 499 CcDee, 437 ccDEe, and 480 ccDee samples formed bell-shaped peaks. Three, 10, and 12 samples, respectively, had decreased antigen densities and carried variant RHD alleles. Weak D type 19, RHD(I204T); weak D type 20, RHD(F417S); and the partial D DYU (also known as DQC), RHD(R234W) were new RHD alleles. Twenty-eight CcDee, 28 ccDEe, and 22 ccDee samples had increased antigen densities; 53 of them lacked a hybrid Rhesus box and were thus predicted to be RHD homozygous. Eight ccDee samples were predicted to be heterozygous despite a large relative dose of RHD to RHCE alleles in quantitative polymerase chain reaction. One of these samples was further investigated and carried an RHD-CE hybrid transcript characteristic for a -D- haplotype.

CONCLUSIONS

Unusual little and large RhD protein integration into the membrane could be traced to a host of distinct protein variants. Weak expression of D antigen was invariably associated with variant RHD alleles. Larger than normal D antigen density may often be caused by the presence of two D encoding alleles, which may be located in cis, and confounding zygosity testing that is solely based on gene copy number.

TLR4 gene dosage contributes to endotoxin-induced acute respiratory inflammation

Toll-like receptor (TLR)4 is critical for endotoxin recognition and cellular responses. Using Tlr4 transgenic mice, we investigated the influence of Tlr4 gene dosage on acute respiratory response to endotoxin. Transgenic mice expressing three, six, or 30 copies of Tlr4, control, and Tlr4-deficient mice received intranasal administration of lipopolysaccharide (LPS; 10 ug), and the airway response was analyzed by plethysmography, lung histology, cell recruitment, cytokine and chemokine secretion and protein leakage into the bronchoalveolar space. We demonstrate that overexpression of Tlr4 augmented a LPS-induced bronchoconstrictive effect, as well as tumor necrosis factor and CXC chemokine ligand 1 (keratinocyte-derived chemokine) production. Neutrophil recruitment, microvascular and alveolar epithelial injury with protein leak in the airways, and damage of the lung microarchitecture were Tlr4 gene dose-dependently increased. Therefore, the TLR4 expression level determines the extent of acute pulmonary response to inhaled endotoxin, and TLR4 may thus be a valuable target for immunointervention in acute lung inflammation as a result of endotoxins.

New insights on macrophage migration inhibitory factor: Based on molecular and functional analysis of its homologue of Chinese amphioxus

Macrophage migration inhibitory factor (MIF) is an intricate cytokine. Many questions about it are not fully resolved. In order to identify the role of MIF in Chinese amphioxus, its genomic organization, transcription pattern and enzymatic activity were studied. It's found that MIF has multi-copy gene number in the Chinese amphioxus genome and special transcription pattern in reproductive organs. Interestingly, the recombinant Bbt-MIF has tantomerase and redox activity, but fails to utilize GSH to reduce insulin instead of DTT, strikingly different from MIF in mammalian. All these results indicate that MIF gene must have undergone important changes in structure and function during the transition of invertebrate/vertebrate and might exert important role in this primitive species, which may be quite different from those found in vertebrate.

Only VpreB1, but not VpreB2, is expressed at levels which allow normal development of B cells

The surrogate light chain (SLC) consists of the polypeptides lambda5 and, in the mouse, either VpreB1 or VpreB2. SLC associates with BILL-Cadherin and other glycoproteins to form the pro-B cell receptor (pro-BCR) at the pre-BI cell stage, and with the immunoglobulin mu heavy chain to form the pre-BCR at the pre-BII cell stage. The function of the pro-BCR, if any, is unknown, whereas the pre-BCR is crucial for proliferative expansion of pre-BII cells. To shed light on the functional properties of VpreB1 and VpreB2 in vivo, mice with either one or two VpreB1, or one or two VpreB2, alleles have been investigated. We show that B cell development in mice with two VpreB1 alleles is indistinguishable from that of normal mice. In contrast, mice with two VpreB2 alleles show an approximately 1.6-fold increase in pre-BI and a 35% decrease in pre-BII cell numbers, while mice with only one VpreB2 allele show a reduction in B cell development manifested in a 2-fold enrichment in pre-BI cells and a 75% reduction in pre-BII cells. However, such a gene dosage effect is not observed for VpreB1. Our results suggest that the difference between VpreB1- and VpreB2-deficient mice is due to lower VpreB2 protein expression, thus limiting the formation of pre-BCRs and thereby the number of large, cycling pre-BII cells.

Insulin alleles and autoimmune regulator (AIRE) gene expression both influence insulin expression in the thymus

It is well established that the polymorphisms at the 5' of the insulin gene (IDDM2) confers susceptibility to type 1 diabetes, probably by modifying the level of insulin expression in the thymus that in turn influences immunological tolerance to insulin as self-antigen. AIRE is a transcription regulator which controls the expression of many peripheral antigens within the thymus, among them insulin. Results presented here confirm that insulin gene copies from both parental chromosomes are expressed in human thymus and that IDDM2 class III protective alleles are indeed associated with a higher level of insulin message expression. However, differences in insulin mRNA expression among different thymi were far wider than those determined by the class I and class III insulin gene alleles and maintained a clear correlation with AIRE expression. These results confirm the effect of IDDM2 alleles on insulin expression in the thymus, but suggest that the levels of AIRE may exert a stronger influence than IDDM2 alleles themselves.