CD98-Mediated Adhesive Signaling Enables the Establishment and Propagation of Acute Myelogenous Leukemia.

Acute myelogenous leukemia (AML) is an aggressive disease associated with drug resistance and relapse. To improve therapeutic strategies, it is critical to better understand the mechanisms that underlie AML progression. Here we show that the integrin binding glycoprotein CD98 plays a central role in AML. CD98 promotes AML propagation and lethality by driving engagement of leukemia cells with their microenvironment and maintaining leukemic stem cells. Further, delivery of a humanized anti-CD98 antibody blocks growth of patient-derived AML, highlighting the importance of this pathway in human disease. These findings indicate that microenvironmental interactions are key regulators of AML and that disrupting these signals with targeted inhibitors such as CD98 antibodies may be a valuable therapeutic approach for adults and children with this disease.

Combination Therapy for Ulcerative Colitis: Orally Targeted Nanoparticles Prevent Mucosal Damage and Relieve Inflammation.

Combination therapy is an emerging strategy that is under intensive preclinical investigation for the treatment of various diseases. CD98 is highly overexpressed on the surfaces of epithelial cells and macrophages in the colon tissue with ulcerative colitis (UC), which is usually associated with mucosal damage and inflammation. We previously proved that CD98 siRNA (siCD98)-induced down-regulation of CD98 in colitis tissue decreased the severity of UC to a certain extent. In an effort to further improve the therapeutic efficacy, we aim to simultaneously deliver siCD98 in combination with a potent anti-inflammatory agent, curcumin (CUR), using hyaluronic acid (HA)-functionalized polymeric nanoparticles (NPs). The resultant spherical HA-siCD98/CUR-NPs are featured by a desirable particle size (∼246 nm) and slightly negative zeta potential (∼-14 mV). The NPs functionalized with HA are able to guide the co-delivery of drugs to the targeted cells related to UC therapy (colonic epithelial cells and macrophages). Compared to either siCD98- or CUR-based monotherapy, co-delivery of siCD98 and CUR by HA-functionalized NPs can exert combinational effects against UC by protecting the mucosal layer and alleviating inflammation both in vitro and in vivo. This study shows the promising capability of the co-delivered siCD98 and CUR for boosting the conventional monotherapy via this novel nanotherapeutic agent, which offers a structurally simple platform for orally administered delivery of drugs to target cells in UC therapy.

Membrane protein 4F2/CD98 is a cell surface receptor involved in the internalization and trafficking of human ß-Defensin 3 in epithelial cells.

Human ß-defensins play a pivotal role in the innate immune response. Although expressed by and acting at epithelial surfaces, little is known about their specific interaction with epithelial structures. Here, we identify the transmembrane protein CD98 as a cell surface receptor involved in the internalization of human ß-defensin 3 (hBD3) in human epithelial A549 cells. CD98 and hBD3 extensively colocalize on the basolateral domain of A549. While verifying their direct binding by fluorescence resonance energy transfer and surface plasmon resonance, we mapped the interaction to CD98 residues 304-414, i.e. to the region known to interact with the proteins of intestinal bacteria during colonic invasion. Treatment of A549 cells with hBD3 dramatically reduces CD98 expression and conversely, knockdown of CD98 expression impairs hBD3 cell surface binding and internalization. Competition for bacterial binding to CD98 and downregulation of CD98 expression may represent novel mechanisms for the antibacterial activity of hBD3.

Antitumor activity of an anti-CD98 antibody.

CD98 is expressed on several tissue types and specifically upregulated on fast-cycling cells undergoing clonal expansion. Various solid (e.g., nonsmall cell lung carcinoma) as well as hematological malignancies (e.g., acute myeloid leukemia) overexpress CD98. We have identified a CD98-specific mouse monoclonal antibody that exhibits potent preclinical antitumor activity against established lymphoma tumor xenografts. Additionally, the humanized antibody designated IGN523 demonstrated robust tumor growth inhibition in leukemic cell-line derived xenograft models and was as efficacious as standard of care carboplatin in patient-derived nonsmall lung cancer xenografts. In vitro studies revealed that IGN523 elicited strong ADCC activity, induced lysosomal membrane permeabilization and inhibited essential amino acid transport function, ultimately resulting in caspase-3 and -7-mediated apoptosis of tumor cells. IGN523 is currently being evaluated in a Phase I clinical trial for acute myeloid leukemia (NCT02040506). Furthermore, preclinical data support the therapeutic potential of IGN523 in solid tumors.

CD147-CD98hc complex contributes to poor prognosis of non-small cell lung cancer patients through promoting cell proliferation via the PI3K/Akt signaling pathway.

BACKGROUND: It has been reported that CD147 and CD98 heavy chain (CD98hc) form a complex on the cell plasma membrane of several cancers; however, whether this complex exists in non-small cell lung cancer (NSCLC) cells and affects the prognosis of patients remains to be elucidated. METHODS: The expression of CD147 and CD98hc was assessed in tissue samples from 241 NSCLC patients and NSCLC cell lines. The correlation between CD147 and CD98hc expression and their association with the prognosis of NSCLC patients were analyzed. We also evaluated the impact of CD147 and CD98hc on the growth of NSCLC cells as well as Akt phosphorylation. RESULTS: Both CD147 and CD98hc were significantly upregulated in NSCLC cells, and their expression levels were significantly correlated (p < 0.001). Immunoflurenece staining and co-immunoprecipitation demonstrated that CD147 and CD98hc could form a complex on NSCLC cells. Compared with NSCLC patients with CD147-/CD98hc-, those with CD147+/CD98hc+ exhibited a significantly poor overall survival (OS) with a hazard ratio (HR) of 1.92 (p = 0.010), and a significantly increased risk of recurrence with a HR of 1.97 (p = 0.004). Also, we demonstrated that the proliferation of lung cancer cell lines was significantly affected by knockdown and force-expression of the CD147-CD98hc complex. Western blot analysis indicated that the phosphorylation of Akt in NSCLC cells was significantly affected by knockdown and overexpression of either or both CD147 and CD98hc. CONCLUSIONS: Our findings indicate that the CD147-CD98hc complex significantly contributes to poor prognosis of NSCLC patients through promoting cell proliferation via the PI3K/Akt pathway.

CD98 marks a subpopulation of head and neck squamous cell carcinoma cells with stem cell properties.

Patients with advanced head and neck squamous cell carcinomas (HNSCCs) are often treated with concomitant chemotherapy and radiotherapy, but only 50% is cured. A possible explanation for treatment failure is therapy resistance of the cancer stem cells (CSCs). The application of compounds specifically targeting these CSCs, in addition to routinely used therapeutics, would likely improve clinical outcome. We demonstrate that the previously described monoclonal antibody K984 recognizes the CD98 cell surface protein, which is specifically expressed by cells forming the squamous basal cell layer, the region where the squamous stem cells reside. Moreover, CD98 is highly resistant to the proteolytic enzymes required for CSC enrichment procedures. We show that CD98(high) cells, in contrast to CD98(low) cells, are able to generate tumors in immunodeficient mice, indicating that CD98(high) cells have stem cell characteristics. Furthermore, the CD98(high) subpopulation expresses high levels of cell cycle control and DNA repair genes, while the CD98(low) fraction shows expression patterns that represent the more differentiated cells forming the bulk of the tumor. CD98 is a promising CSC enrichment marker in HNSCC. Our data support the CSC concept in head and neck cancer and the potential relevance of these cells for treatment outcome.

Cyclophilin B induces integrin-mediated cell adhesion by a mechanism involving CD98-dependent activation of protein kinase C-delta and p44/42 mitogen-activated protein kinases.

Initially identified as a cyclosporin-A binding protein, cyclophilin B (CyPB) is an inflammatory mediator that induces adhesion of T lymphocytes to fibronectin, by a mechanism dependent on CD147 and alpha 4 beta 1 integrins. Recent findings have suggested that another cell membrane protein, CD98, may cooperate with CD147 to regulate beta1 integrin functions. Based on these functional relationships, we examined the contribution of CD98 in the pro-adhesive activity of CyPB, by utilizing the responsive promonocyte cell line THP-1. We demonstrated that cross-linking CD98 with CD98-AHN-18 antibody mimicked the responses induced by CyPB, i.e. homotypic aggregation, integrin-mediated adhesion to fibronectin and activation of p44/42 MAPK. Consistent with previous data, immunoprecipitation confirmed the existence of a heterocomplex wherein CD147, CD98 and beta1 integrins were associated. We then demonstrated that CyPB-induced cell adhesion and p44/42 MAPK activation were dependent on the participation of phosphoinositide 3-kinase and subsequent activation of protein kinase C-delta. Finally, silencing the expression of CD98 by RNA interference potently reduced CyPB-induced cell responses, thus confirming the role of CD98 in the pro-adhesive activity of CyPB. Altogether, our results support a model whereby CyPB induces integrin-mediated adhesion via interaction with a multimolecular unit formed by the association between CD147, CD98 and beta1 integrins.