Cell Adhesion Molecule 1 Contributes to Cell Survival in Crowded Epithelial Monolayers

Efficient intracellular drug delivery by co-administration of two antibodies against cell adhesion molecule 1

Cell adhesion molecule 1 (CADM1), a single-pass transmembrane protein, is involved in oncogenesis. We previously demonstrated the therapeutic efficacy of anti-CADM1 ectodomain monoclonal antibodies against mesothelioma; however, the underlying mechanism is unclear. In the present study, we explored the molecular behavior of anti-CADM1 antibodies in CADM1-expressing tumor cells. Sequencing analyses revealed that the anti-CADM1 chicken monoclonal antibodies 3E1 and 9D2 are IgY and IgM isotype antibodies, respectively. Co-administration of 3E1 and 9D2 altered the subcellular distribution of CADM1 from the detergent-soluble fraction to the detergent-resistant fraction in tumor cells. Using recombinant chicken-mouse chimeric antibodies that had been isotype-switched from IgG to IgM, we demonstrated that the combination of the variable region of 3E1 and the constant region of IgM was required for CADM1 relocation. Cytochemical studies showed that 3E1 colocalized with late endosomes/lysosomes after co-administration with 9D2, suggesting that the CADM1-antibody complex is internalized from the cell surface to intracellular compartments by lipid-raft mediated endocytosis. Finally, 3E1 was conjugated with the antimitotic agent monomethyl auristatin E (MMAE) via a cathepsin-cleavable linker. Co-administration of 3E1-monomethyl auristatin E and 9D2 suppressed the growth of multiple types of tumor cells, and this anti-tumor activity was confirmed in a syngeneic mouse model of melanoma. 3E1 and 9D2 are promising drug delivery vehicles for CADM1-expressing tumor cells.

The disordered extracellular matrix landscape induced endometrial fibrosis of sheep: A multi-omics integrative analysis

Endometrial fibrosis leads to the destruction of endometrial function and affects reproductive performance. However, mechanisms underlying the development of endometrial fibrosis in sheep remain unclear. We use transcriptomic, proteomic, and metabolomic studies to reveal the formation mechanisms of endometrial fibrosis. The results showed that the fibrotic endometrial tissue phenotype presented fewer glands, accompanied by collagen deposition. Transcriptomic results indicated alterations in genes associated with the synthesis and degradation of extracellular matrix components, which alter metabolite homeostasis, especially in glycerophospholipid metabolism. Moreover, differentially expressed metabolites may play regulatory roles in key metabolic processes during fibrogenesis, including protein digestion and absorption, and amino acid synthesis. Affected by the aberrant genes, protein levels related to the extracellular matrix components were altered. In addition, based on Kyoto Encyclopedia of Genes and Genomes analysis of differentially expressed genes, metabolites and proteins, amino acid biosynthesis, glutathione, glycerophospholipid, arginine and proline metabolism, and cell adhesion are closely associated with fibrogenesis. Finally, we analyzed the dynamic changes in serum differential metabolites at different time points during fibrosis. Taken together, fibrosis development is related to metabolic obstacles in extracellular matrix synthesis and degradation triggered by disturbed gene and protein levels.

Loss of function of ribosomal protein L13a blocks blastocyst formation and reveals a potential nuclear role in gene expression

Ribosomal proteins play diverse roles in development and disease. Most ribosomal proteins have canonical roles in protein synthesis, while some exhibit extra-ribosomal functions. Previous studies in our laboratory revealed that ribosomal protein L13a (RPL13a) is involved in the translational silencing of a cohort of inflammatory proteins in myeloid cells. This prompted us to investigate the role of RPL13a in embryonic development. Here we report that RPL13a is required for early development in mice. Crosses between Rpl13a+/- mice resulted in no Rpl13a-/- offspring. Closer examination revealed that Rpl13a-/- embryos were arrested at the morula stage during preimplantation development. RNA sequencing analysis of Rpl13a-/- morulae revealed widespread alterations in gene expression, including but not limited to several genes encoding proteins involved in the inflammatory response, embryogenesis, oocyte maturation, stemness, and pluripotency. Ex vivo analysis revealed that RPL13a was localized to the cytoplasm and nucleus between the two-cell and morula stages. RNAi-mediated depletion of RPL13a phenocopied Rpl13a-/- embryos and knockdown embryos exhibited increased expression of IL-7 and IL-17 and decreased expression of the lineage specifier genes Sox2, Pou5f1, and Cdx2. Lastly, a protein-protein interaction assay revealed that RPL13a is associated with chromatin, suggesting an extra ribosomal function in transcription. In summary, our data demonstrate that RPL13a is essential for the completion of preimplantation embryo development. The mechanistic basis of the absence of RPL13a-mediated embryonic lethality will be addressed in the future through follow-up studies on ribosome biogenesis, global protein synthesis, and identification of RPL13a target genes using chromatin immunoprecipitation and RNA-immunoprecipitation-based sequencing.

Potential Contribution of Cell Adhesion Molecule 1 to the Binding of SARS-CoV-2 Spike Protein to Mouse Nasal Mucosa

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) first infects the host nasal mucosa, where the viral spike protein binds to angiotensin-converting enzyme 2 (ACE2) on the mucosal cells. This study aimed at searching host cell surface molecules that could contribute to the infection in two views; abundance on host cells and affinity to the spike protein. Since the nasal mucosa is lined by respiratory and olfactory epithelia, and both express an immunoglobulin superfamily member cell adhesion molecule 1 (CADM1), whether CADM1 would participate in the spike protein binding was examined. Immunohistochemistry on the mouse nasal cavity detected CADM1 strongly in the olfactory epithelium at cell-cell contacts and on the apical surface but just faintly in the respiratory epithelium. In contrast, ACE2 was detected in the respiratory, not olfactory, epithelium. When mice were administered intranasally with SARS-CoV-2 S1 spike protein and an anti-CADM1 ectodomain antibody separately, both were detected exclusively on the olfactory, not respiratory, epithelium. Then, the antibody and S1 spike protein were administered intranasally to mice in this order with an interval of 1 hour. After 3 hours, S1 spike protein was detected as a protein aggregate floating in the nasal cavity. Next, S1 spike protein labeled with fluorescein was added to the monolayer cultures of epithelial cells exogenously expressing ACE2 or CADM1. Quantitative detection of fluorescein bound to the cells revealed that S1 spike protein bound to CADM1 with affinity half as high as to ACE2. Consistently, docking simulation analyses revealed that S1 spike protein could bind to CADM1 three quarters as strongly as to ACE2 and that the interface of ACE2 was similar in both binding modes. Collectively, intranasal S1 spike protein appeared to prefer to accumulate on the olfactory epithelium, and CADM1 was suggested to contribute to this preference of S1 spike protein based on the molecular abundance and affinity.

Possible Therapeutic Utility of anti-Cell Adhesion Molecule 1 Antibodies for Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a highly aggressive malignant tumor, and the effective therapeutic drugs are limited. Thus, the establishment of novel therapeutic method is desired. Considerable proportion of MPMs are shown to express cell adhesion molecule 1 (CADM1), and to use CADM1 to bind to and proliferate on the pleural mesothelial surface, suggesting that CADM1 is a possible therapeutic target. Here, anti-CADM1 ectodomain chicken monoclonal antibodies, 3E1 and 9D2, were examined for their possible therapeutic utility. The full-length form of CADM1 was expressed in eight out of twelve human MPM cell lines. MPM cell lines were cultured on a confluent monolayer of mesothelial MeT-5A cells in the presence of 9D2, the neutralizing antibody. 9D2 suppressed the cell growth of CADM1-positive MPM cells with the loss and aggregation of CADM1 molecules on the MPM cell membrane, but not of CADM1-negative MPM cells. Co-addition of 3E1, lacking the neutralizing action, enhanced the growth-suppressive effect of 9D2. The two antibodies were tested as drug delivery vectors. 3E1 was converted into a humanized antibody (h3E1) and conjugated with monomethyl auristatin E (MMAE), a tubulin polymerization inhibitor. When the resulting h3E1–MMAE antibody-drug conjugate (ADC) was added to the standard cultures of CADM1-positive MPM cells, it suppressed the cell growth in a dose-dependent manner. Co-addition of 9D2 enhanced the growth-suppressive effect of h3E1–MMAE ADC. Anti-CADM1 ectodomain antibodies were suggested to serve as both antibody drugs and drug vectors in the treatment of MPM.

A Fully-Human Antibody Specifically Targeting a Membrane-Bound Fragment of CADM1 Potentiates the T Cell-Mediated Death of Human Small-Cell Lung Cancer Cells

Small-cell lung cancer (SCLC) is the most aggressive form of lung cancer and the leading cause of global cancer-related mortality. Despite the earlier identification of membrane-proximal cleavage of cell adhesion molecule 1 (CADM1) in cancers, the role of the membrane-bound fragment of CAMD1 (MF-CADM1) is yet to be clearly identified. In this study, we first isolated MF-CADM1-specific fully human single-chain variable fragments (scFvs) from the human synthetic scFv antibody library using the phage display technology. Following the selected scFv conversion to human immunoglobulin G1 (IgG1) scFv-Fc antibodies (K103.1–4), multiple characterization studies, including antibody cross-species reactivity, purity, production yield, and binding affinity, were verified. Finally, via intensive in vitro efficacy and toxicity evaluation studies, we identified K103.3 as a lead antibody that potently promotes the death of human SCLC cell lines, including NCI-H69, NCI-H146, and NCI-H187, by activated Jurkat T cells without severe endothelial toxicity. Taken together, these findings suggest that antibody-based targeting of MF-CADM1 may be an effective strategy to potentiate T cell-mediated SCLC death, and MF-CADM1 may be a novel potential therapeutic target in SCLC for antibody therapy.

Expression of cell adhesion molecule 1 in human and murine endometrial glandular cells and its increase during the proliferative phase by estrogen and cell density

AIMS

Cell adhesion molecule 1 (CADM1) mediates interepithelial adhesion and is upregulated in crowded epithelial monolayers. This study aimed to examine CADM1 expression in the human endometrium of proliferative and secretory phases, and its transcriptional regulation in terms of estrogen stimuli and higher cellularity.

MAIN METHODS

CADM1 immunohistochemistry was conducted on endometrial tissues from women in their 40s and adult mice subcutaneously injected with estradiol following ovariectomy. Dual-luciferase reporter assays were conducted using human endometrial HEC-50B and HEC-1B cells and reporter plasmids harboring the human CADM1 3.4-kb promoter and its deleted and mutated forms. Cells were transfected with estrogen receptor α cDNA and reporter plasmids, and treated with estradiol before luciferase activity measurement.

KEY FINDINGS

Immunohistochemistry revealed that CADM1 was clearly expressed on the lateral membranes of the simple columnar glandular cells in the proliferative phase, but not in the secretory phase, from both women and the mouse model. The glandular cell density increased two-fold in the proliferative phase. Reporter assays identified three Sp1-binding sites as estradiol-responsive elements in the proximal region (from -223 to -84) of the transcription start site (+1) in HEC-50B cells. When the cell culture was started at eight-fold higher cell density, the CADM1 3.4-kb promoter was transactivated at a two-fold higher level in HEC-50B cells. This cell density effect was not detected for the CADM1 2.3-kb or 1.6-kb promoter.

SIGNIFICANCE

Two (proximal and distal) promoter regions are suggested to function additively to transactivate CADM1 in endometrial glandular cells that crowd in the proliferative phase.

The Role of Cell Adhesion Molecule 1 (CADM1) in Cutaneous Malignancies

Cell adhesion ability is one of the components to establish cell organization and shows a great contribution to human body construction consisting of various types of cells mixture to orchestrate tissue specific function. The cell adhesion molecule 1 (CADM1) is a molecule of cell adhesion with multiple functions and has been identified as a tumor suppressor gene. CADM1 has multifunctions on the pathogenesis of malignancies, and other normal cells such as immune cells. However, little is known about the function of CADM1 on cutaneous cells and cutaneous malignancies. CADM1 plays an important role in connecting cells with each other, contacting cells to deliver their signal, and acting as a scaffolding molecule for other immune cells to develop their immune responses. A limited number of studies reveal the contribution of CADM1 on the development of cutaneous malignancies. Solid cutaneous malignancies, such as cutaneous squamous cell carcinoma and malignant melanoma, reduce their CADM1 expression to promote the invasion and metastasis of the tumor. On the contrary to these cutaneous solid tumors except for Merkel cell carcinoma, cutaneous lymphomas, such as adult-T cell leukemia/lymphoma, mycosis fungoides, and Sézary syndrome, increase their CADM1 expression for the development of tumor environment. Based on the role of CADM1 in the etiology of tumor development, the theory of CADM1 contribution will desirably be applied to skin tumors according to other organ malignancies, however, the characteristics of skin as a multicomponent peripheral organ should be kept in mind to conclude their prognoses.