Characterisation of the mouse homologue of CD151 (PETA-3/SFA-1); genomic structure, chromosomal localisation and identification of 2 novel splice forms

Tetraspanin CD9: A friend or foe of head and neck cancer (Review)

Head and neck cancers are diverse and complex diseases characterised by unregulated growth of tumour cells in various parts of the head and neck region, such as in the buccal mucosa, floor of the mouth, tongue, oropharynx, hypopharynx, oesophagus, nasopharynx and salivary glands. Partial or total glossectomy, radiation or chemotherapy greatly affect patient quality of life. However, even following treatment, patients may relapse. Nicotine-derived nitrosamines and alcohol are the major etiological factors underlying this deadly disease. These compounds induce DNA damage that may lead to mutation in crucial genes, such as p53 and p21, which are important to regulate cell proliferation, thus leading to cancer. CD9 is a tetraspanin, which are a group of transmembrane proteins that have a role in cell motility and adhesion. The present review aimed to explore the role of CD9 in head and neck cancer. Epidermal growth factor receptor activity and cell proliferation are regulated by the CD9-integrin/CD9-transforming growth factor interaction. Hence, CD9 can play a dual role in various types of cancer.

Tetraspanins as regulators of the tumour microenvironment: implications for metastasis and therapeutic strategies

One of the hallmarks of cancer is the ability to activate invasion and metastasis. Cancer morbidity and mortality are largely related to the spread of the primary, localized tumour to adjacent and distant sites. Appropriate management and treatment decisions based on predicting metastatic disease at the time of diagnosis is thus crucial, which supports better understanding of the metastatic process. There are components of metastasis that are common to all primary tumours: dissociation from the primary tumour mass, reorganization/remodelling of extracellular matrix, cell migration, recognition and movement through endothelial cells and the vascular circulation and lodgement and proliferation within ectopic stroma. One of the key and initial events is the increased ability of cancer cells to move, escaping the regulation of normal physiological control. The cellular cytoskeleton plays an important role in cancer cell motility and active cytoskeletal rearrangement can result in metastatic disease. This active change in cytoskeletal dynamics results in manipulation of plasma membrane and cellular balance between cellular adhesion and motility which in turn determines cancer cell movement. Members of the tetraspanin family of proteins play important roles in regulation of cancer cell migration and cancer-endothelial cell interactions, which are critical for cancer invasion and metastasis. Their involvements in active cytoskeletal dynamics, cancer metastasis and potential clinical application will be discussed in this review. In particular, the tetraspanin member, CD151, is highlighted for its major role in cancer invasion and metastasis.

LINKED ARTICLES

This article is part of a themed section on Cytoskeleton, Extracellular Matrix, Cell Migration, Wound Healing and Related Topics. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-24.

Corticotropin (ACTH) regulates alternative RNA splicing in Y1 mouse adrenocortical tumor cells

The stimulatory effect of ACTH on gene expression is well documented and is thought to be a major mechanism by which ACTH maintains the functional and structural integrity of the gland. Previously, we showed that ACTH regulates the accumulation of over 1200 transcripts in Y1 adrenal cells, including a cluster with functions in alternative splicing of RNA. On this basis, we postulated that some of the effects of ACTH on the transcription landscape of Y1 cells are mediated by alternative splicing. In this study, we demonstrate that ACTH regulates the alternative splicing of four transcripts - Gnas, Cd151, Dab2 and Tia1. Inasmuch as alternative splicing potentially affects transcripts from more than two-thirds of the mouse genome, we suggest that these findings are representative of a genome-wide effect of ACTH that impacts on the mRNA and protein composition of the adrenal cortex.

CD151 in cancer progression and metastasis: a complex scenario

Originally identified as a molecular organizer of interacting proteins into tetraspanin-enriched microdomains, the tetraspanin CD151 has now been shown to be involved in tumour progression. Increasing evidence emerging from in vitro, in vivo and clinical analyses implicates this tetraspanin in supporting growth of various types of tumours at different levels. It affects both cell autonomous behavior and communication with neighboring cells and the microenvironment. CD151 regulates post-adhesion events, that is, cell spreading, migration and invasion including subsequent intravasation and formation of metastasis. Present on both neoplastic and endothelial cells, CD151 is engaged in promotion of tumour neovascularization. The molecular mechanism of CD151 in cancer is based on its ability to organize distribution and function of interacting proteins, ie, laminin-binding integrins (α3β1, α6β1 and α6β4), receptors for growth factors (HGFR, EGFR and TGF-β1R) and matrix metalloproteinases (MMP-7, MMP-2 and MMP-9), which indicates its importance in disease development. Results of clinical analyses of CD151 expression in different types of cancer and a large number of in vivo models demonstrate its impact on tumour growth and invasion and implicate CD151 as a valuable diagnostic and prognostic marker as well as a potential target for anti-cancer therapy.

Tetraspanins and vascular functions

Tetraspanins are multiple membrane-spanning proteins that likely function as the organizers of membrane microdomains. Tetraspanins associate with other membrane-bound molecules such as cell-adhesion proteins, growth factor receptors, and Ig superfamily members and regulate key cellular processes such as adhesion, migration, and fusion. Tetraspanins are widely expressed in vascular and haematopoietic cells and are involved in both physiological and pathological processes related to angiogenesis, vascular injury, thrombosis, and haemostasis. A wide body of evidence suggests that tetraspanins directly regulate the development and functions of the vascular system and the pathogenesis of vascular diseases. This article reviews current understanding of the roles of tetraspanins in vascular functions.

Characterization of mice lacking the tetraspanin superfamily member CD151

The tetraspanin membrane protein CD151 is a broadly expressed molecule noted for its strong molecular associations with integrins, especially alpha3beta1, alpha6beta1, alpha7beta1, and alpha6beta4. In vitro functional studies have pointed to a role for CD151 in cell-cell adhesion, cell migration, platelet aggregation, and angiogenesis. It has also been implicated in epithelial tumor progression and metastasis. Here we describe the generation and initial characterization of CD151-null mice. The mice are viable, healthy, and fertile and show normal Mendelian inheritance. They have essentially normal blood and bone marrow cell counts and grossly normal tissue morphology, including hemidesmosomes in skin, and expression of alpha3 and alpha6 integrins. However, the CD151-null mice do show phenotypes in several different tissue types. An absence of CD151 leads to a minor abnormality in hemostasis, with CD151-null mice showing longer average bleeding times, greater average blood loss, and an increased incidence of rebleeding occurrences. CD151-null keratinocytes migrate poorly in skin explant cultures. Finally, CD151-null T lymphocytes are hyperproliferative in response to in vitro mitogenic stimulation.

CD151 enhances cell motility and metastasis of cancer cells in the presence of focal adhesion kinase

We have examined the role of the protein CD151 in cell motility, invasion and metastasis of cancer cells by using CD151-overexpressing cells prepared by transfection of CD151 cDNA into three cancer cell lines established from different origins; a human colon cancer RPMI4788, a human glioblastoma A172 and a human fibrosarcoma HT1080. Invasion into Matrigel and cell motility of all 3 CD151-overexpressing cancer cells were enhanced significantly when compared to control parental cells. Pulmonary metastasis of 2 metastatic CD151-overexpressing cancer cell lines, RPMI4788/CD151 and HT1080/CD151, was higher than that of control parental cells and was markedly inhibited by anti-CD151 monoclonal antibody (MAb), SFA1.2B4. To examine whether focal adhesion kinase (FAK) is associated with promotion of cell motility and invasion of cancer cells through CD151, we transfected human CD151 cDNA into FAK (+/+) or FAK (-/-) fibroblasts that were isolated from embryos in FAK-deficient mice and compared invasion into Matrigel and cell motility between each CD151-transfected cells and controls. The invasion into Matrigel and cell motility of CD151-transfected FAK (+/+) fibroblasts increased significantly above those of parental cells and were inhibited by anti-CD151 MAb, whereas those of CD151-transfected FAK (-/-) fibroblasts were not enhanced at all and were not blocked by anti-CD151 MAb. These findings indicate that the CD151 molecule enhances cell motility, invasion and metastasis of cancer cells and that FAK is needed for these events through CD151.

Differential tissue expression of epitopes of the tetraspanin CD151 recognised by monoclonal antibodies

CD151, a member of the tetraspanin family of cell membrane proteins, is widely expressed in epithelial, endothelial and muscle cells as well as platelets and megakaryocytes. Several monoclonal antibodies recognising CD151 in transfected cells and immunoprecipitating typical bands of 28 and 32 kDa from cell lysates have been produced. Surprisingly, these antibodies show different patterns of staining on tissue sections and on haemopoietic cells. Here we show that these differences are at least in part due to masking of certain epitopes in integrin/CD151 complexes. These data have important implications for the use of monoclonal antibodies in studies of the distribution and function of CD151. Of six monoclonal antibodies from four laboratories, 11B1 was found to be the most reliable for detection of CD151 in different cell and tissue contexts.

Transmembrane-4-superfamily proteins CD151 and CD81 associate with alpha 3 beta 1 integrin, and selectively contribute to alpha 3 beta 1-dependent neurite outgrowth

Proteins in the transmembrane-4-superfamily (TM4SF) form many different complexes with proteins in the integrin family, but the functional utility of these complexes has not yet been demonstrated. Here we show that TM4SF proteins CD151, CD81, and CD63 co-distribute with alpha3beta1 integrin on neurites and growth cones of human NT2N cells. Also, stable CD151-alpha3beta1 and CD81-alpha3beta1 complexes were recovered in NT2N detergent lysates. Total NT2N neurite outgrowth on laminin-5 (a ligand for alpha3beta1 integrin) was strongly inhibited by anti-CD151 and -CD81 antibodies either together ( approximately 85% inhibition) or alone ( approximately 45% inhibition). Notably, these antibodies had no inhibitory effect on NT2N neurites formed on laminin-1 or fibronectin, when alpha3beta1integrin was not engaged. Neurite number, length, and rate of extension were all affected by anti-TM4SF antibodies. In summary: (1) these substrate-dependent inhibition results strongly suggest that CD151 and CD81 associations with alpha3beta1 are functionally relevant, (2) TM4SF proteins CD151 and CD81 make a strong positive contribution toward neurite number, length, and rate of outgrowth, and (3) NT2N cells, a well-established model of immature central nervous system neurons, can be a powerful system for studies of integrin function in neurite outgrowth and growth cone motility.

The molecular characterisation of a novel tetraspanin protein, TM4-B(1)

TM4-B is a novel member of the Tetraspanin superfamily and displays characteristics typical of the superfamily. It bears significant homology to other superfamily members and is most similar to Tspan-1. This molecule is broadly expressed in most human tissues and cell lines including neural and bone marrow derived tissues. TM4-B was mapped to the q34 region on human chromosome 9.