Junctional adhesion molecule B interferes with angiogenic VEGF/VEGFR2 signaling

JAM2 predicts a good prognosis and inhibits invasion and migration by suppressing EMT pathway in breast cancer

OBJECTIVES

Large-scale epidemiological surveys have shown that patients with Down syndrome, which is caused by a chromosomal abnormality (an extra chromosome 21), are significantly less likely to develop solid tumors, including breast cancer, than those without. This feature has prompted the search for oncogenes located on chromosome 21. Junctional adhesion molecule 2 (JAM2), which is located on chromosome 21, is expressed at low levels in breast cancer and is associated with a good prognosis. These findings strongly suggest that JAM2 may be a potential oncogene suppressor in breast cancer. However, the role and function of JAM2 in breast cancer are not yet clear. Therefore, this study aimed to explore the biological functions and mechanisms of JAM2 in breast cancer.

METHODS

Several databases were used to explore JAM2 expression in breast cancer and to analyze its diagnostic and prognostic value in breast cancer. Changes in relevant markers were examined at the gene and protein levels using RT-qPCR and Western blot techniques, in addition, cell migration and invasion abilities were identified by scratch assays and transwell assays. Untargeted metabolomics, transcriptome sequencing and Luminex liquid suspension chip detection were performed in combination to study the mechanisms.

RESULTS

JAM2 is expressed at low levels in breast cancer, and patients with high JAM2 expression have a good prognosis, indicating that JAM2 has good clinical diagnostic and prognostic value. Overexpression of JAM2 can block the invasion and migration of breast cancer cells, and the mechanism may be that JAM2 inhibits the EMT pathway. Finally, combined multiomics analysis revealed that JAM2 may affect the immune microenvironment of breast cancer by influencing the secretion of CXCL9/10 from tumor cells.

Moderate Folic Acid Supplementation in Pregnant Mice Results in Altered Methyl Metabolism and in Sex-Specific Placental Transcription Changes

SCOPE

Many pregnant women have higher folic acid (FA) intake due to food fortification and increased vitamin use. It is reported that diets containing five-fold higher FA than recommended for mice (5xFASD) during pregnancy resulted in methylenetetrahydrofolate reductase (MTHFR) deficiency and altered choline/methyl metabolism, with neurobehavioral abnormalities in newborns. The goal is to determine whether these changes have their origins in the placenta during embryonic development.

METHODS AND RESULTS

Female mice are fed control diet or 5xFASD for a month before mating and maintained on these diets until embryonic day 17.5. 5xFASD led to pseudo-MTHFR deficiency in maternal liver and altered choline/methyl metabolites in maternal plasma (increased methyltetrahydrofolate and decreased betaine). Methylation potential (S-adenosylmethionine:S-adenosylhomocysteine ratio) and glycerophosphocholine are decreased in placenta and embryonic liver. Folic acid supplemented diet results in sex-specific transcriptome profiles in placenta, with validation of dietary expression changes of 29 genes involved in angiogenesis, receptor biology or neurodevelopment, and altered methylation of the serotonin receptor 2A gene.

CONCLUSION

Moderate increases in folate intake during pregnancy result in placental metabolic and gene expression changes, particularly in angiogenesis, which may contribute to abnormal behavior in pups. These results are relevant for determining a safe upper limit for folate intake during pregnancy.

Junctional adhesion molecule C (JAM-C) dimerization aids cancer cell migration and metastasis

Most cancer deaths result from metastasis, which is the dissemination of cells from a primary tumor to distant organs. Metastasis involves changes to molecules that are essential for tumor cell adhesion to the extracellular matrix and to endothelial cells. Junctional Adhesion Molecule C (JAM-C) localizes at intercellular junctions as homodimers or more affine heterodimers with JAM-B. We previously showed that the homodimerization site (E66) in JAM-C is also involved in JAM-B binding. Here we show that neoexpression of JAM-C in a JAM-C-negative carcinoma cell line induced loss of adhesive property and pro-metastatic capacities. We also identify two critical structural sites (E66 and K68) for JAM-C/JAM-B interaction by directed mutagenesis of JAM-C and studied their implication on tumor cell behavior. JAM-C mutants did not bind to JAM-B or localize correctly to junctions. Moreover, mutated JAM-C proteins increased adhesion and reduced proliferation and migration of lung carcinoma cell lines. Carcinoma cells expressing mutant JAM-C grew slower than with JAM-C WT and were not able to establish metastatic lung nodules in mice. Overall these data demonstrate that the dimerization sites E66-K68 of JAM-C affected cell adhesion, polarization and migration and are essential for tumor cell metastasis.

Angiogenic factor-driven inflammation promotes extravasation of human proangiogenic monocytes to tumours

Recruitment of circulating monocytes is critical for tumour angiogenesis. However, how human monocyte subpopulations extravasate to tumours is unclear. Here we show mechanisms of extravasation of human CD14^dimCD16⁺ patrolling and CD14⁺CD16⁺ intermediate proangiogenic monocytes (HPMo), using human tumour xenograft models and live imaging of transmigration. IFNγ promotes an increase of the chemokine CX3CL1 on vessel lumen, imposing continuous crawling to HPMo and making these monocytes insensitive to chemokines required for their extravasation. Expression of the angiogenic factor VEGF and the inflammatory cytokine TNF by tumour cells enables HPMo extravasation by inducing GATA3-mediated repression of CX3CL1 expression. Recruited HPMo boosts angiogenesis by secreting MMP9 leading to release of matrix-bound VEGF-A, which amplifies the entry of more HPMo into tumours. Uncovering the extravasation cascade of HPMo sets the stage for future tumour therapies.

Circulating myeloid cells can leave the vasculature to infiltrate tumours and are thought to contribute to tumour angiogenesis. Here the authors live image monocytes that migrate to xenograft tumours and map an extravasation cascade of human proangiogenic monocytes into the tumour.

Junctional Adhesion Molecules (JAMs): Cell Adhesion Receptors With Pleiotropic Functions in Cell Physiology and Development

Junctional adhesion molecules (JAM)-A, -B and -C are cell-cell adhesion molecules of the immunoglobulin superfamily which are expressed by a variety of tissues, both during development and in the adult organism. Through their extracellular domains, they interact with other adhesion receptors on opposing cells. Through their cytoplasmic domains, they interact with PDZ domain-containing scaffolding and signaling proteins. In combination, these two properties regulate the assembly of signaling complexes at specific sites of cell-cell adhesion. The multitude of molecular interactions has enabled JAMs to adopt distinct cellular functions such as the regulation of cell-cell contact formation, cell migration, or mitotic spindle orientation. Not surprisingly, JAMs regulate diverse processes such as epithelial and endothelial barrier formation, hemostasis, angiogenesis, hematopoiesis, germ cell development, and the development of the central and peripheral nervous system. This review summarizes the recent progress in the understanding of JAMs, including their characteristic structural features, their molecular interactions, their cellular functions, and their contribution to a multitude of processes during vertebrate development and homeostasis.

The role of JAM-B in cancer and cancer metastasis (Review)

The junctional adhesion molecule B (JAM-B) is a multifunctional transmembrane protein, which belongs to the immunoglobulin superfamily (IgSF). JAM-B is localized to cell-cell contacts and enriched at cell junctions in epithelial and endothelial cells, as well as on the surface of erythrocytes, leukocytes, and platelets. Recent research in this field has shown that JAM-B plays an important role in numerous cellular processes, such as tight junction assembly, spermatogenesis, regulation of paracellular permeability, leukocytic transmigration, angiogenesis, tumor metastasis and cell proliferation. This study provides a new research direction for the diagnosis and treatment of relevant diseases. In this review, we briefly focus on what is currently known about the structure, function, and mechanism of JAM-B, with particular emphasis on cancer.

Effect of junctional adhesion molecule-2 expression on cell growth, invasion and migration in human colorectal cancer

The junctional adhesion molecule (JAMs) family belongs to the immunoglobulin subfamily involved in the formation of tight junctions (TJ) in both endothelial and epithelial cells. Aberrant expression of JAM-2 is associated with cancer progression but little work has been carried out in discovering how this affects changes in cell behaviour. The present study aimed to examine the expression of JAM-2 in human colon cancer specimens and cell lines and its role in the development of colon cancer. JAM-2 expression in human colon cancer specimens (normal, n=75; cancer, n=94) and cell lines was analysed using quantitative real-time PCR and conventional RT-PCR. Colon cancer cells were stably transfected with a mammalian expression vector to overexpress JAM-2-Flag. The effect on growth, adhesion and migration following overexpression of JAM-2 was then investigated using in vitro models. TJ function was assessed using a trans-epithelial resistance assay (TER, with an EVOM voltammeter). JAM-2 was lowly expressed in colon cancer cells such as RKO, HT115. JAM-2 overexpression in RKO cells (RKO-JAM-2) and HT115 cells (HT115-JAM-2) showed retarded adhesion (P<0.05). An in vivo tumour model showed that RKO-JAM-2 had significantly reduced growth (P<0.05), invasion (P<0.05) and migration (P<0.05) as well as in HT115-JAM-2, except on proliferation and migration. Expression of JAM-2 resulted in a significant increase in TER and decrease in permeability of polarized monolayers (P<0.05). Further analysis of JAM-2 transcript levels against clinical aspects demonstrated that the decreasing JAM-2 expression correlated to disease progression, metastasis and poor survival. Taken together, JAM-2 may function as a putative tumour suppressor in the progression and metastasis of colorectal cancer.

Differential mouse-strain specific expression of Junctional Adhesion Molecule (JAM)-B in placental structures

The junctional adhesion molecule (JAM)-B, a member of the immunoglobulin superfamily, is involved in stabilization of interendothelial cell-cell contacts, formation of vascular tubes, homeostasis of stem cell niches and promotion of leukocyte adhesion and transmigration. In the human placenta, JAM-B protein is abundant and mRNA transcripts are enriched in first-trimester extravillous trophoblast in comparison to the villous trophoblast. We here aimed to elucidate the yet unexplored spatio-temporal expression of JAM-B in the mouse placenta. We investigated and semi-quantified JAM-B protein expression by immunohistochemistry in early post-implantation si tes and in mid- to late gestation placentae of various murine mating combinations. Surprisingly, the endothelium of the placental labyrinth was devoid of JAM-B expression. JAM-B was mainly present in spongiotrophoblast cells of the junctional zone, as well as in the fetal vessels of the chorionic plate, the umbilical cord and in maternal myometrial smooth muscle. We observed a strain-specific placental increase of JAM-B protein expression from mid- to late gestation in Balb/c-mated C57BL/6 females, which was absent in DBA/2J-mated Balb/c females. Due to the essential role of progesterone during gestation, we further assessed a possible modulation of JAM-B in mid-gestational placentae deficient in the progesterone receptor (Pgr(-/-)) and observed an increased expression of JAM-B in Pgr(-/-) placentae, compared to Pgr(+/+) tissue samples. We propose that JAM-B is an as yet underappreciated trophoblast lineage-specific protein, which is modulated via the progesterone receptor and shows unique strain-specific kinetics. Future work is needed to elucidate its possible contribution to placental processes necessary to ensuring its integrity, ultimately facilitating placental development and fetal growth.