An Agonistic Antibody to EPHA2 Exhibits Antitumor Effects on Human Melanoma Cells

Abstract

Abstract. Background/Aim: EPH receptor A2 (EPHA2) is highly expressed in aggressive types of human cancer, and is expected to be an excellent target molecule for antibody treatments. In this study, we investigated the therapeutic potential of antibody to EPHA2 against melanoma in vitro. Materials and Methods: We generated three monoclonal antibodies (mAbs) to EPHA2 and examined cell-surface expression by flow cytometry. To investigate the ability to inhibit tumor cell migration therapy with mAbs to EPHA2, we performed a wound scratch assay and invasion assay. We investigated the therapeutic effects of immunotoxins consisting of toxin-conjugated EPHA2 mAbs. Results: All human melanoma cell lines studied expressed EPHA2. Like natural ligand ephrin-A1, one of EPHA2 mAbs, SHM16, inhibited metastatic behavior of cells, such as migration and invasion. In addition, drastic growth inhibition and cytotoxicity were found using immunotoxin-conjugated SHM16. Conclusion: These observations indicate a promising role for EPHA2 as a target in antibody treatments for melanoma, and demonstrate the potential therapeutic effects of an agonistic antibody to EPHA2.Melanoma is the most aggressive type of skin cancer. While melanoma accounts for fewer than 5% of all skin cancer cases, it is responsible for the large majority of deaths due to skin cancer. The type of treatment will depend not only on stage and location of the melanoma, but also on the patient's overall health. When melanoma has not grown deeper than the epidermis, it is usually treated by surgery (wide excision). When this is not possible, therapeutic options including injections of Bacille Calmette-Guerin (BCG) vaccine, interferon, or interleukin-2 (IL2) directly into the melanoma, radiation therapy, and chemotherapy (1, 2). The treatment of widespread melanoma has changed in recent years as newer forms of immunotherapy and molecularly-targeted drugs have been shown to be more effective than chemotherapy (3-6).Receptor tyrosine kinases (RTKs) transmit signals that regulate cell proliferation and differentiation, promote cell migration and survival, and modulate cell metabolism. They play critical roles in a wide range of biological processes, including embryonic development, growth of an organism, angiogenesis, synaptic plasticity, and oncogenesis (7-9). EPH receptors, the largest subfamily of RTKs, are involved in many biological processes including angiogenesis, tissue-border formation, cell migration, and axon guidance (10, 11). EPH receptors and their ephrin ligands are important mediators of cell-to-cell communication that regulate cell attachment to the extracellular matrix, cell shape and cell motility. They have been studied extensively for their roles in the developmental process. In recent years, EPH receptors and ephrins have been found to be integral players in cancer formation and progression. EPH receptor A2 (EPHA2) and ephrin-A1 are especially known to be involved in the development and maintenance of many types of solid tumors (12)(13)(14).EPHA2 was ori...

Targeting EphA2 in cancer

“…Decreased ligand-mediated receptor internalization and degradation, consequently enhancing protein stability, might help increase EphA2 amounts in malignant cells. An interesting consequence of EphA2 stimulation (by ligand or antibody) is EphA2 phosphorylation, internalization, and degradation [43][44][45]. After liganddependent induction, EphA2 aggregation occurs at the cell surface, followed by tyrosine phosphorylation, In the malignant state, loss of cell-cell contacts induces receptor-ligand interaction and degradation of EphA2.…”

“…Indeed, treatment with D2 scFv induced apoptosis and reduced cell proliferation in the lymphoma cell line. In addition, Sakamoto et al [43] showed that one of the EphA2 mAbs produced, SHM16, interacts with an EphA2 epitope differing from that affecting ephrin A1 binding to EphA2. SHM16 was clearly internalized in cells and inhibited malignant features in melanoma cells.…”

Ephrin Receptors (Eph): EphA1, EphA5, and EphA7 Expression in Uveal Melanoma—Associations with Clinical Parameters and Patient Survival

“…Accumulative clinical evidence has demonstrated that Eph receptors expression is associated with clinicopathological parameters important for patient management and prognosis in a variety of tumors [ 13 , 14 , 15 , 16 , 17 , 18 ]. Among others, there are reports about the role of Eph receptors in skin melanomas [ 19 , 20 ]. However, there is no comprehensive available data concerning the clinical significance of Eph receptors expression in uveal melanoma, whose biology is significantly different from skin melanomas.…”

Association of Age-Related Cataract With Skin Cancer in an Australian Population

“…26 Its downregulation and neutralization of the encoded protein have been associated with decreased migration and invasion of melanoma cells indicating its role in oncogenesis. 27,28 Epha2 knockout mice exhibit a greater susceptibility to chemically induced skin cancer, which suggests a tumor suppressor function of this gene, and its overexpression in tumor cells a likely compensatory mechanism to decrease cell proliferation. 29 Regardless of the mechanism, EPHA2 is involved in skin cancer.…”