Expression of cell adhesion molecule 1 in malignant pleural mesothelioma as a cause of efficient adhesion and growth on mesothelium

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.

Establishment of an experimental model of canine malignant mesothelioma organoid culture using a three-dimensional culture method

Canine malignant mesothelioma (cMM) is a rare and drug-resistant malignant tumor. Due to few patients and experimental models, there have not been enough studies to demonstrate the pathogenesis of the disease and novel effective treatment for cMM. Since cMM resembles human MM (hMM) in histopathological characteristics, it is also considered a promising research model of hMM. Compared with conventional 2-dimensional (2D) culture methods, 3-dimensional (3D) organoid culture can recapitulate the properties of original tumor tissues. However, cMM organoids have never been developed. In the present study, we for the first time generated cMM organoids using the pleural effusion samples. Organoids from individual MM dogs were successfully generated. They exhibited the characteristics of MM and expressed mesothelial cell markers, such as WT-1 and mesothelin. The sensitivity to anti-cancer drugs was different in each strain of cMM organoids. RNA sequencing analysis showed cell adhesion molecule pathways were specifically upregulated in cMM organoids compared with their corresponding 2D cultured cells. Among these genes, the expression level of E-cadherin was drastically higher in the organoids than that in the 2D cells. In conclusion, our established cMM organoids might become a new experimental tool to provide new insights into canine and human MM therapy.

Somatic mutations of CADM1 in aldosterone-producing adenomas and gap junction-dependent regulation of aldosterone production

Aldosterone-producing adenomas (APAs) are the commonest curable cause of hypertension. Most have gain-of-function somatic mutations of ion channels or transporters. Herein we report the discovery, replication and phenotype of mutations in the neuronal cell adhesion gene CADM1. Independent whole exome sequencing of 40 and 81 APAs found intramembranous p.Val380Asp or p.Gly379Asp variants in two patients whose hypertension and periodic primary aldosteronism were cured by adrenalectomy. Replication identified two more APAs with each variant (total, n = 6). The most upregulated gene (10- to 25-fold) in human adrenocortical H295R cells transduced with the mutations (compared to wildtype) was CYP11B2 (aldosterone synthase), and biological rhythms were the most differentially expressed process. CADM1 knockdown or mutation inhibited gap junction (GJ)-permeable dye transfer. GJ blockade by Gap27 increased CYP11B2 similarly to CADM1 mutation. Human adrenal zona glomerulosa (ZG) expression of GJA1 (the main GJ protein) was patchy, and annular GJs (sequelae of GJ communication) were less prominent in CYP11B2-positive micronodules than adjacent ZG. Somatic mutations of CADM1 cause reversible hypertension and reveal a role for GJ communication in suppressing physiological aldosterone production.

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.

Differential Expression of CADM1 in Gastrointestinal Stromal Tumors of Different Sites and with Different Gene Abnormalities

Gastrointestinal stromal tumor (GIST), the most common mesenchymal tumor of the human gastrointestinal tract, differentiating toward the interstitial cell of Cajal (ICC), arises predominantly in the stomach and small intestine. Small intestinal GISTs appear to have worse prognosis than gastric GISTs. In a pilot study of a cDNA expression chip using several GISTs, we found that Cell Adhesion Molecule 1 (CADM1), which could contribute to tumor growth and infiltration, is expressed more strongly in small intestinal GISTs than gastric GISTs. In the present study, we examined CADM1 expression in GISTs of different sites and with different gene abnormalities using a large number of gastric and small intestinal GISTs. First, immunoblotting confirmed significantly higher CADM1 expression in small intestinal GISTs with exon 11 c-kit mutation than gastric GISTs with exon 11 c-kit mutation. Real-time PCR also revealed that small intestinal GISTs with exon 11 c-kit mutation showed significantly higher CADM1 mRNA than gastric GISTs with exon 11 c-kit mutation. Although most small intestinal GISTs showed high CADM1 mRNA expression regardless of gene abnormality types, different CADM1 expression was detected between gastric GISTs with c-kit mutation and those with PDGFRA mutation. Immunohistochemistry showed that many small intestinal GISTs were CADM1-positive but most gastric GISTs CADM1-negative or -indefinite. In the normal gastric and small intestinal walls, immunoreactivity of CADM1 was detected only in nerves, but neither in gastric ICCs nor small intestinal ICCs, indicating that the high CADM1expression in small intestinal GISTs might be acquired during tumorigenesis. Different CADM1 expression between gastric and small intestinal GISTs might be related to different prognoses between them. Further functional experiments are needed to elucidate the role of CADM1 on GIST biology, and there is a possibility that targeting therapy against CADM1 has a preventive effect for tumor spreading in small intestinal GISTs.

Expression of cell adhesion molecule 1 in gastric neck and base glandular cells: Possible involvement in peritoneal dissemination of signet ring cells

AIMS

To determine cellular distribution of cell adhesion molecule 1 (CADM1), an immunoglobulin superfamily member, in the human oxyntic gastric mucosa, and to explore possible involvement in the development and peritoneal dissemination of signet ring cell (SRC) gastric carcinoma, which often develops in the oxyntic mucosa.

MAIN METHODS

Immunohistochemistry and double immunofluorescence were conducted on surgical specimens of normal and SRC-bearing stomachs and peritoneal metastatic foci of SRCs. KATO-III (lacking CADM1) and HSC-43 (expressing CADM1) SRC cell lines were cocultured on a Met-5A mesothelial or TIG-1 fibroblastic cell monolayer.

KEY FINDINGS

In the oxyntic gland, some neck and nearly all base glandular cells were CADM1-positive, and mucin 5AC-positive cells were CADM1-negative, while some mucin 6-positive neck cells were CADM1-positive. Foveolar-epithelial, parietal, and endocrine cells were CADM1-negative. CADM1 was negative in all SRC carcinomas that were confined within the submucosa (n = 11) and all but one of those invading deeper (n = 15). In contrast, peritoneal metastatic foci of SRCs were CADM1-positive in five out of eleven cases (P < 0.01). In the cocultures, exogenous CADM1 made KATO-III cells adhere more and grow faster on a Met-5A monolayer, not on TIG-1 monolayers. HSC-43 cells adhered more and grew faster on Met-5A than on TIG-1 monolayers, which were partly counteracted by a function-neutralizing anti-CADM1 antibody.

SIGNIFICANCE

Nearly all chief cells and a part of mucous neck cells express CADM1. SRC gastric carcinoma appears to emerge as a CADM1-negative tumor, but CADM1 may help SRCs develop peritoneal dissemination through promoting their adhesion and growth in the serosal tissue.

Modest Static Pressure Suppresses Columnar Epithelial Cell Growth in Association with Cell Shape and Cytoskeletal Modifications

Intraluminal pressure elevation can cause degenerative disorders, such as ileus and hydronephrosis, and the threshold is fairly low and constant, 20–30 cm H₂O. We previously devised a novel two-chamber culture system subjecting cells cultured on a semipermeable membrane to increased culture medium height (water pressure up to 60 cm H₂O). Here, we sought to determine how a continuous pressure load of ~30 cm H₂O affects proliferating epithelial cells with special interest in the link with cell morphology. We cultured several different cell lines using the low static pressure-loadable two-chamber system, and examined cell growth, cell cycle, and cell morphology. Madin–Darby canine kidney (MDCK) columnar epithelial cells were growth-suppressed in a manner dependent on static water pressure ranging from 2 to 50 cm H₂O, without cell cycle arrest at any specific phase. Two other types of columnar epithelial cells exhibited similar phenotypes. By contrast, spherical epithelial and mesenchymal cells were not growth-suppressed, even at 50 cm H₂O. Phalloidin staining revealed that 50 cm H₂O pressure load vertically flattened and laterally widened columnar epithelial cells and made actin fiber distribution sparse, without affecting total phalloidin intensity per cell. When the mucosal protectant irsogladine maleate (100 nM) was added to 50-cm-high culture medium, MDCK cells were reduced in volume and their doubling time shortened. Cell proliferation and morphology are known to be regulated by the Hippo signaling pathway. A pressure load of 50 cm H₂O enhanced serine-127 phosphorylation and cytoplasmic retention of YAP, the major constituent of this pathway, suggesting that Hippo pathway was involved in the pressure-induced cell growth suppression. RNA sequencing of MDCK cells showed that a 50 cm H₂O pressure load upregulated keratin 14, an intermediate filament, 12-fold. This upregulation was confirmed at the protein level by immunofluorescence, suggesting a role in cytoskeletal reinforcement. These results provide evidence that cell morphology and the cytoskeleton are closely linked to cell growth. Pathological intraluminal pressure elevation may cause mucosal degeneration by acting directly on this linkage and the Hippo pathway.

New insights into understanding the mechanisms, pathogenesis, and management of malignant mesotheliomas

Malignant mesothelioma (MM) is a relatively rare but devastating tumor that is increasing worldwide. Yet, because of difficulties in early diagnosis and resistance to conventional therapies, MM remains a challenge for pathologists and clinicians to treat. In recent years, much has been revealed regarding the mechanisms of interactions of pathogenic fibers with mesothelial cells, crucial signaling pathways, and genetic and epigenetic events that may occur during the pathogenesis of these unusual, pleiomorphic tumors. These observations support a scenario whereby mesothelial cells undergo a series of chronic injury, inflammation, and proliferation in the long latency period of MM development that may be perpetuated by durable fibers, the tumor microenvironment, and inflammatory stimuli. One culprit in sustained inflammation is the activated inflammasome, a component of macrophages or mesothelial cells that leads to production of chemotactic, growth-promoting, and angiogenic cytokines. This information has been vital to designing novel therapeutic approaches for patients with MM that focus on immunotherapy, targeting growth factor receptors and pathways, overcoming resistance to apoptosis, and modifying epigenetic changes.

Cell adhesion molecule 1 is a new osteoblastic cell adhesion molecule and a diagnostic marker for osteosarcoma

AIMS

An immunohistochemical screen for mouse embryos showed that cell adhesion molecule 1 (CADM1), which is an immunoglobulin superfamily member, was expressed in developing bones. Here, we determined the cell types expressing CADM1 and examined its usefulness in the differential diagnosis of osteosarcoma.

MAIN METHODS

Serial sections of murine developing mandibles were stained with anti-CADM1 antibody, by a coloring substrate reactive to alkaline phosphatase (ALP), a broad osteoblastic marker for preosteoblasts to osteoblasts, and by in situ hybridization for osteopontin (OPN), a marker for mature osteoblasts. CADM1 immunohistochemistry was also performed on human remodeling bones, osteosarcomas and other soft tissue tumors.

KEY FINDINGS

CADM1 immunohistochemistry for the mandible revealed that morphologically identifiable osteoblasts expressed CADM1 on their plasma membranes, but neither osteocytes nor bone lining cells did. At the mandibular margin, not only OPN-positive cells but also OPN-negative, ALP-positive cells were CADM1-positive, whereas inside the mandible, OPN-positive cells were often CADM1-negative. Clear membranous staining was detected in the majority of osteosarcomas (46/57), whereas only 13% (6/46) of the other soft tissue tumors were CADM1-positive (P<0.001).

SIGNIFICANCE

These results indicated that CADM1 was a novel osteoblastic adhesion molecule that is expressed transiently during osteoblastic maturation, and a useful diagnostic marker for osteosarcoma cells.

Activated leukocyte cell-adhesion molecule (ALCAM) promotes malignant phenotypes of malignant mesothelioma

INTRODUCTION

Cell-adhesion molecules play important roles involving the malignant phenotypes of human cancer cells. However, detailed characteristics of aberrant expression status of cell-adhesion molecules in malignant mesothelioma (MM) cells and their possible biological roles for MM malignancy remain poorly understood.

METHODS

DNA microarray analysis was employed to identify aberrantly expressing genes using 20 MM cell lines. Activated leukocyte cell-adhesion molecule (ALCAM) expression in MM cell lines was analyzed with quantitative reverse transcription-polymerase chain reaction and Western blot analyses in 47 primary MM specimens with immunohistochemistry. ALCAM knockdown in MM cell lines was performed with lentivirus-mediated short hairpin RNA (shRNA) transduction. Purified soluble ALCAM (sALCAM) protein was used for in vitro experiments, whereas MM cell lines infected with the sALCAM-expressing lentivirus were tested for tumorigenicity in vivo.

RESULTS

ALCAM, a member of the immunoglobulin superfamily, was detected as one of the most highly upregulated genes among 103 cell-adhesion molecules with microarray analysis. Elevated expression levels of ALCAM messenger RNA and protein were detected in all 20 cell lines. Positive staining of ALCAM was detected in 26 of 47 MM specimens (55%) with immunohistochemistry. ALCAM knockdown with shRNA suppressed cell migration and invasion of MM cell lines. Purified sALCAM protein impaired the migration and invasion of MM cells in vitro, and the infection of sALCAM-expressing virus into MM cells significantly prolonged survival periods of MM-transplanted nude mice in vivo.

CONCLUSION

Our study suggests that overexpression of ALCAM contributes to tumor progression in MM and that ALCAM might be a potential therapeutic target of MM.

Adhesion molecule CADM1 contributes to gap junctional communication among pancreatic islet α-cells and prevents their excessive secretion of glucagon

Cell adhesion molecule-1 (CADM1) is a recently identified adhesion molecule of pancreatic islet α-cells that mediates nerve-α-cell interactions via trans-homophilic binding and serves anatomical units for the autonomic control of glucagon secretion. CADM1 also mediates attachment between adjacent α-cells. Since gap junctional intercellular communication (GJIC) among islet cells is essential for islet hormone secretion, we examined whether CADM1 promotes GJIC among α-cells and subsequently participates in glucagon secretion regulation. Dye transfer assays using αTC6 mouse α-cells, which endogenously express CADM1, supported this possibility; efficient cell-to-cell spread of gap junction-permeable dye was detected in clusters of αTC6 cells transfected with nonspecific, but not with CADM1-targeting, siRNA. Immunocytochemical analysis of connexin 36, a major component of the gap junction among αTC6 cells, revealed that it was localized exclusively to the cell membrane in CADM1-non-targeted αTC6 cells, but diffusely to the cytoplasm in CADM1-targeted cells. Next, we incubated CADM1-targeted and non-targeted αTC6 cells in a medium containing 1 mM glucose and 200 mM arginine for 30 min to induce glucagon secretion, and found that the targeted cells secreted three times more glucagon than did the non-targeted. We conducted similar experiments using pancreatic islets that were freshly isolated from wild-type and CADM1-knockout mice, and expressed glucagon secretion as ratios relative to baseline values. The increase in ratio was larger in CADM1-knockout islets than in wild-type islets. These results suggest that CADM1 may serve as a volume limiter of glucagon secretion by sustaining α-cell attachment necessary for efficient GJIC.

Tumor suppressor cell adhesion molecule 1 (CADM1) is cleaved by a disintegrin and metalloprotease 10 (ADAM10) and subsequently cleaved by γ-secretase complex

Cell adhesion molecule 1 (CADM1) is a type I transmembrane glycoprotein expressed in various tissues. CADM1 is a cell adhesion molecule with many functions, including roles in tumor suppression, apoptosis, mast cell survival, synapse formation, and spermatogenesis. CADM1 undergoes membrane-proximal cleavage called shedding, but the sheddase and mechanisms of CADM1 proteolysis have not been reported. We determined the cleavage site involved in CADM1 shedding by LC/MS/MS and showed that CADM1 shedding occurred in the membrane fraction and was inhibited by tumor necrosis factor-α protease inhibitor-1 (TAPI-1). An siRNA experiment revealed that ADAM10 mediates endogenous CADM1 shedding. In addition, the membrane-bound fragment generated by shedding was further cleaved by γ-secretase and generated CADM1-intracellular domain (ICD) in a mechanism called regulated intramembrane proteolysis (RIP). These results clarify the detailed mechanism of membrane-proximal cleavage of CADM1, suggesting the possibility of RIP-mediated CADM1 signaling.

Hypoexpression and epigenetic regulation of candidate tumor suppressor gene CADM-2 in human prostate cancer

PURPOSE

Cell adhesion molecules (CADM) comprise a newly identified protein family whose functions include cell polarity maintenance and tumor suppression. CADM-1, CADM-3, and CADM-4 have been shown to act as tumor suppressor genes in multiple cancers including prostate cancer. However, CADM-2 expression has not been determined in prostate cancer.

EXPERIMENTAL DESIGN

The CADM-2 gene was cloned and characterized and its expression in human prostatic cell lines and cancer specimens was analyzed by reverse transcription-PCR and an immunohistochemical tissue array, respectively. The effects of adenovirus-mediated CADM-2 expression on prostate cancer cells were also investigated. CADM-2 promoter methylation was evaluated by bisulfite sequencing and methylation-specific PCR.

RESULTS

We report the initial characterization of CADM-2 isoforms: CADM-2a and CADM-2b, each with separate promoters, in human chromosome 3p12.1. Prostate cancer cell lines, LNCaP and DU145, expressed negligible CADM-2a relative to primary prostate tissue and cell lines, RWPE-1 and PPC-1, whereas expression of CADM-2b was maintained. Using immunohistochemistry, tissue array results from clinical specimens showed statistically significant decreased expression in prostate carcinoma compared with normal donor prostate, benign prostatic hyperplasia, prostatic intraepithelial neoplasia, and normal tissue adjacent to tumor (P < 0.001). Adenovirus-mediated CADM-2a expression suppressed DU145 cell proliferation in vitro and colony formation in soft agar. The decrease in CADM-2a mRNA in cancer cell lines correlated with promoter region hypermethylation as determined by bisulfite sequencing and methylation-specific PCR. Accordingly, treatment of cells with the demethylating agent 5-aza-2'-deoxycytidine alone or in combination with the histone deacetylase inhibitor trichostatin A resulted in the reactivation of CADM-2a expression.

CONCLUSIONS

CADM-2a protein expression is significantly reduced in prostate cancer. Its expression is regulated in part by promoter methylation and implicates CADM-2 as a previously unrecognized tumor suppressor gene in a proportion of human prostate cancers.

Cell adhesion molecule 1: a novel risk factor for venous thrombosis

Protein C (PC) deficiency increases the risk of venous thrombosis (VT) among members of Kindred Vermont II but fails to fully account for the inheritance pattern. A genome scan of the pedigree supported the presence of a prothrombotic gene on chromosome 11q23 (nominal P < .0001), with weaker support on chromosomes 10p12 (P < .0003) and 18p11.2-q11 (P < .0007). Resequencing of 109 genes in the linkage regions identified 5030 variants in a sample of 20 kindred members. Of 16 single nucleotide polymorphisms in 6 genes tested in the larger family set, only single nucleotide polymorphisms in cell adhesion molecule 1 (CADM1) associated with VT. Among the 8 CADM1 single nucleotide polymorphisms genotyped in the complete sample, rs6589488 was most strongly supported (P < .000007), but the association was limited to the PC-deficient subset of the sample (P < .000001). Haplotype analysis narrowed the region containing the causative variant to the coding region of the CADM1 gene. CADM1 gene expression analyzed in blood outgrowth endothelial cells cultured from family members was decreased compared with control subjects, lending phenotypic support to this conclusion. Finally, we have for the first time demonstrated CADM1 in endothelial cells, where it appears to be selectively involved in endothelial cell migration, suggesting a role in endothelial barrier repair.

Expression of a soluble isoform of cell adhesion molecule 1 in the brain and its involvement in directional neurite outgrowth

Cell adhesion molecule 1 (CADM1), an immunoglobulin superfamily member, is expressed on superior cervical ganglion neurites and mediates cell-cell adhesion by trans-homophilic binding. In addition to the membrane-bound form, we have previously shown that a soluble form (sCADM1) generated by alternative splicing possesses a stop codon immediately downstream of the immunoglobulin-like domain. Here, we demonstrate the presence of sCADM1 in vivo and its possible role in neurite extension. sCADM1 appears to be a stromal protein because extracellular-restricted, but not intracellular-restricted, anti-CADM1 antibody stained stromal protein-rich extract from mouse brains. Murine plasmacytoma cells, P3U1, were modified to secrete sCADM1 fused with either immunoglobulin (Ig)G Fc portion (sCADM1-Fc) or its deletion form that lacks the immunoglobulin-like domain (DeltasCADM1-Fc). When P3U1 derivatives expressing sCADM1-Fc or DeltasCADM1-Fc were implanted into collagen gels, Fc-fused proteins were present more abundantly around the cells. Superior cervical ganglion neurons, parental P3U1, and either derivative were implanted into collagen gels separately, and co-cultured for 4 days. Bodian staining of the gel sections revealed that most superior cervical ganglion neurites turned toward the source of sCADM1-Fc, but not DeltasCADM1-Fc. Furthermore, immunofluorescence signals for sCADM1-Fc and membrane-bound CADM1 were co-localized on the neurite surface. These results show that sCADM1 appears to be involved in directional neurite extension by serving as an anchor to which membrane-bound CADM1 on the neurites can bind.

Role of the spermatogenic-Sertoli cell interaction through cell adhesion molecule-1 (CADM1) in spermatogenesis

Endocrine and local secretory factors have long been known to be required for spermatogenesis. Evidence has been accumulating in recent years indicating that direct contact between spermatogenic and Sertoli cells is also required for spermatogenesis. Cell adhesion molecules of various types have been found in the mammalian testis that are expressed in spermatogenic and/or Sertoli cells and involved in homophilic and/or heterophilic binding. We have cloned a novel cell adhesion molecule, cell adhesion molecule-1 (CADM1), also known as immunoglobulin superfamily 4A or spermatogenic immunoglobulin superfamily, from the mouse testis. CADM1 belongs to the immunoglobulin superfamily and is composed of three immunoglobulin-like domains, a transmembrane domain, and a short intracellular domain. In the seminiferous epithelium, CADM1 is expressed in intermediate spermatogonia through to early pachytene spermatocytes as well as in elongating spermatids--but not in round spermatids, mature spermatozoa, or Sertoli cells. One of the heterophilic binding partners of CADM1 has proven to be a poliovirus receptor, another member of the immunoglobulin superfamily that is expressed in Sertoli cells. Knockout mice for CADM1 develop male infertility due to defective spermatogenesis. These findings suggest that cell adhesion molecules between spermatogenic and Sertoli cells play essential roles in spermatogenesis.

Nerve-mast cell and smooth muscle-mast cell interaction mediated by cell adhesion molecule-1, CADM1

Mast cells are a native composer of connective tissue of the skin dermis and intestinal and respiratory mucosa. Independent lines of accumulated evidence indicate the existence of an intensive bidirectional crosstalk between mast cells and sensory nerves and suggest that mast cells and sensory nerves may be viewed as a functional unit, which could be of crucial importance in neuroimmunological pathways. Mast cells appear to have a property of influencing smooth muscle function via not only such nerve-mast cell effects, but also direct pathways. In bronchial asthma, mast cells infiltrate the airway smooth muscle layer, and interact directly with smooth muscle cells, suggesting pathogenic roles for mast cells in airway obstruction. Current studies on mast cell biology identified a novel adhesion molecule of mast cells, namely cell adhesion molecule-1, CADM1. This molecule is unique, because it serves as not only simple glue but also appears to promote functional communication between nerve and mast cells and between smooth muscle and mast cells.