Abstract
Anti-HER2/neu antibody therapy has been reported to mediate tumor regression of HER2/ neu+ tumors. Here we demonstrated the expression of HER2 in a wide range of human melanoma cells including a primary culture and seven cell lines, and we further investigated whether HER2 could be served as a target for T cell mediated immunotherapy of human melanoma. Specific cytolytic activity of activated T cells (ATC) armed with anti-CD3 x anti-HER2 bispecific antibody (HER2Bi-Ab) against Malme-3M-luc cells was evaluated by bioluminescent signal generated by luciferase reporter which did not alter HER2 expression or proliferation ability of Malme-3M cells. Contrast with unarmed ATC, increased cytotoxic activity of HER2Bi-armed ATC against Malme-3M-luc cells was observed at effector/target (E/T) ratios of 1:1, 5:1, and 20:1. Moreover, HER2Bi-armed ATC expressed higher level of activation marker CD69 and secreted significantly higher level of IFN-γ than unarmed ATC counterpart at the E/T ratio of 20:1. In addition, compared with anti-HER2 mAb (Herceptin®) or unarmed ATC, HER2Bi-armed ATC showed remarkable suppression effect on Malme-3M-luc tumor cells. Furthermore, in melanoma tumor cell xenograft mice, infusion of HER2Bi-armed ATC successfully inhibited the growth of melanoma tumors. The anti-tumor effect of HER2Bi-armed ATC may provide a promising immunotherapy for melanoma in the future.
Highlights
Melanoma is an increasingly common and potentially dangerous type of skin and mucosal cancer associated with a poor prognosis
To detect HER2Bi-Ab bound to HER2+ or CD3+ cell, Malme-3M-luc or activated T cells (ATC) were incubated with HER2Bi-Ab (1 μg /ml) or a combination of OKT3 and Herceptin® (1 μg/ml, used as the negative control for HER2Bi-Ab) for 30mins; bound HER2 moiety of HER2Bi-Ab to Malme-3M-luc cells was evaluated using FITC-labeled goat anti-mouse IgG to detect the anti-CD3 moiety of the Bi-Ab; bound CD3 moiety of HER2Bi to ATC was evaluated by using FITC-labeled goatanti-human-IgG to detect the HER2 moiety of the Bi-Ab
After 18 hour incubation with HER2Bi-armed ATC or unarmed ATC, bioluminescence image signal expressed in photons per second was converted into living cell number and the cytotoxicity assays was calculated at the indicated E/T ratios
Summary
Melanoma is an increasingly common and potentially dangerous type of skin and mucosal cancer associated with a poor prognosis. Immunotherapies including vaccination and adoptive T cell therapy hold great promise [2], both of which have been targeted to tumor associated antigens such as MART-1, gp100, tyrosinase [3], MAGE family, BAGE, GAGE and gp75 [4,5]. Immunosuppressive molecule CD200 and immune checkpoint proteins such as CTLA-4, PD-1 and CD40 expressed on melanoma cells have been identified as possible immunotherapy candidates [6]. The success of Herceptin® in the treatment of breast cancer suggests its potential role in the treatment of melanoma expressing HER2, some evidence suggests that therapy targeting HER2 may not provide the benefit for patients with metastatic melanoma or as an adjuvant therapy for melanoma patients at high risk for recurrence [19]. In this study we demonstrated that HER2 could be served as a target for immunotherapy of human melanoma after confirmation of the expression of HER2 in human melanoma cells
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