Tetraspanins are integral membrane proteins involved in a variety of physiological and pathological processes. In cancer, clinical and experimental studies have reported a link between tetraspanin expression levels and metastasis. Tetraspanins play a role as organizers of multimolecular complexes in the plasma membrane. Indeed each tetraspanin associates specifically with one or a few other membrane proteins forming primary complexes. Thus, tetraspanin-tetraspanin associations lead to a molecular network of interactions, the “tetraspanin web.” We performed a proteomic characterization of the tetraspanin web using a model of human colon cancer consisting of three cell lines derived from the primary tumor and two metastases (hepatic and peritoneal) from the same patient. The tetraspanin complexes were isolated after immunoaffinity purification using monoclonal antibodies directed against the tetraspanin CD9, and the associated proteins were separated by SDS-PAGE and identified by mass spectrometry using LC-MS/MS. This allowed the identification of 32 proteins including adhesion molecules (integrins, proteins with Ig domains, CD44, and epithelial cell adhesion molecule) (EpCAM), membrane proteases (ADAM10, TADG-15, and CD26/dipeptidyl peptidase IV), and signaling proteins (heterotrimeric G proteins). Importantly some components were differentially detected in the tetraspanin web of the three cell lines: the laminin receptor Lutheran/B-cell adhesion molecule (Lu/B-CAM) was expressed only on the primary tumor cells, whereas CD26/dipeptidyl peptidase IV and tetraspanin Co-029 were observed only on metastatic cells. Concerning Co-029, immunohistofluorescence showed a high expression of Co-029 on epithelial cells in normal colon and a lower expression in tumors, whereas heterogeneity in terms of expression level was observed on metastasis. Finally we demonstrated that epithelial cell adhesion molecule and CD9 form a new primary complex in the tetraspanin web.

Plasmodium sporozoites can enter host cells by two distinct pathways, either through disruption of the plasma membrane followed by parasite transmigration through cells, or by formation of a parasitophorous vacuole (PV) where the parasite further differentiates into a replicative exo‐erythrocytic form (EEF). We now provide evidence that following invasion without PV formation, transmigrating Plasmodium falciparum and Plasmodium yoelii sporozoites can partially develop into EEFs inside hepatocarcinoma cell nuclei. We also found that rodent P. yoelii sporozoites can infect both mouse and human hepatocytes, while human P. falciparum sporozoites infect human but not mouse hepatocytes. We have previously reported that the host tetraspanin CD81 is required for PV formation by P. falciparum and P. yoelii sporozoites. Here we show that expression of human CD81 in CD81‐knockout mouse hepatocytes is sufficient to confer susceptibility to P. yoelii but not P. falciparum sporozoite infection, showing that the narrow P. falciparum host tropism does not rely on CD81 only. Also, expression of CD81 in a human hepatocarcinoma cell line is sufficient to promote the formation of a PV by P. yoelii but not P. falciparum sporozoites. These results highlight critical differences between P. yoelii and P. falciparum sporozoite infection, and suggest that in addition to CD81, other molecules are specifically required for PV formation during infection by the human malaria parasite.

Tumor invasion and metastasis are major obstacles to clinical treatment that rely on cell migration. Here, we elucidate a mechanism of colon carcinoma cell migration that is supported by the cell surface tetraspanin Co-029 (tspan8), which is known to favor tumor progression and metastasis. This mechanism is unmasked by silencing of E-cadherin or its associated adapter molecule p120-catenin (p120ctn), and it involves a switch in signaling between the collagen-binding integrins α₁β₁ and α₂β₁. Direct interaction between E-cadherin and Co-029 was documented by chemical cross-linking and immunohistologic analysis of colon carcinomas. High expression of Co-029 and cytoplasmic delocalization of p120ctn were each associated with poor prognosis. Cell motility was reduced severely by antibody-mediated disruption of Co-029 only when p120ctn was silenced, suggesting that tumor progression may be hindered by Co-029 targeting. Our findings define a function for tetraspanin Co-029 as a modifier of cancer cell motility and reveal an adhesion signaling network implicated in progression and metastasis. Cancer Res; 70(19); 7674–83. ©2010 AACR.

Importance Olmsted syndrome is a genodermatosis characterized by painful and mutilating palmoplantar keratoderma (PPK) that progresses from infancy onward and lacks an effective treatment. It is most often caused by mutations in the transient receptor potential vanilloid 3 (TRPV3)gene. In animal models and keratinocyte cell lines, TRPV3 signaling leads to epidermal growth factor receptor (EGFR) transactivation. Objective To examine the possibility of blocking EGFR transactivation with the inhibitor erlotinib hydrochloride to treat PPK in patients with Olmsted syndrome due toTRPV3mutations. Design, Setting, and Participants In this case series, 3 patients from 2 unrelated families who hadTRPV3-mutation–associated PPK were treated with erlotinib from May 5, 2018, through May 13, 2019. Main Outcomes and Measures Clinical follow-up included evaluation of PPK progression, pain and interventions for pain, as well as erlotinib dose adjustment based on treatment effect, plasma levels, and tolerance. Results The 3 patients (2 brothers aged 15 and 17 years and a 13-year-old girl) had severe palmoplantar hyperkeratosis, intolerable pain with erythromelalgia, severe growth delay, anorexia, and insomnia, which had been progressing since infancy despite numerous therapies. Two patients were confined to wheelchairs owing to intense pain and joint restrictions because of hyperkeratosis. All patients experienced depression and did not engage in social activities. Within 3 months of initiating therapy with erlotinib, hyperkeratosis and pain disappeared. All patients were able to touch the ground with their feet, wear shoes, and walk. Anorexia and insomnia remitted and paralleled improved growth. In addition, the patients resumed social activities. These improvements were sustained across 12 months of treatment and follow-up. The doses of erlotinib used were lower than those used in oncology, and only mild to moderate adverse effects were noted. Conclusions and Relevance The findings of this study report improvement of PPK in patients with Olmsted syndrome caused byTRPV3mutations when treated with erlotinib. Targeting EGFR transactivation with erlotinib therapy may result in clinical remission in an orphan disease that lacks an effective intervention.

(2012). Targeting tetraspanins in cancer. Expert Opinion on Therapeutic Targets: Vol. 16, No. 10, pp. 985-997. doi: 10.1517/14728222.2012.712688