The cyclic VHCDR3-derived peptide (Rb9) from RebMab200 antibody, directed to a NaPi2B phosphate-transport protein, displayed anti-metastatic melanoma activity at 50–300 μg intraperitoneally injected in syngeneic mice. Immune deficient mice failed to respond to the peptide protective effect. Rb9 induced increased CD8+ T and low Foxp3+ T cell infiltration in lung metastases and high IFN-γ and low TGF-β in lymphoid organs. The peptide co-localized with F-actin and a nuclear site in dendritic cells and specifically bound to MIF and CD74 in a dot-blot setting. Murine bone-marrow dendritic cells preincubated with Rb9 for 6 h were treated with MIF for short time periods. The modulated responses showed stimulation of CD74 and inhibition of pPI3K, pERK, and pNF-κB as compared to MIF alone. Rb9 in a melanoma-conditioned medium, stimulated the M1 type conversion in bone marrow-macrophages. Functional aspects of Rb9 in vivo were studied in therapeutic and prophylactic protocols using a melanoma metastatic model. In both protocols Rb9 exhibited a marked anti-melanoma protection. Human dendritic cells were also investigated showing increased expression of surface markers in response to Rb9 incubation. Rb9 either stimulated or slightly inhibited moDCs submitted to inhibitory (TGF-β and IL-10) or activating (LPS) conditions, respectively. Lymphocyte proliferation was obtained with moDCs stimulated by Rb9 and tumor cell lysate. In moDCs from cancer patients Rb9 exerted immunomodulatory activities depending on their functional status. The peptide may inhibit over-stimulated cells, stimulate poorly activated and suppressed cells, or cause instead, little phenotypic and functional alterations. Recently, the interaction MIF-CD74 has been associated to PD-L1 expression and IFN-γ, suggesting a target for melanoma treatment. The effects described for Rb9 and the protection against metastatic melanoma may suggest the possibility of a peptide reagent that could be relevant when associated to modern immunotherapeutic procedures.

来自RebMab200抗体的环状VHCDR3衍生肽（Rb9）直接针对NaPi2B磷酸转运蛋白，在同系小鼠腹膜内注射50-300μg时显示出抗转移性黑色素瘤活性。免疫缺陷小鼠对肽的保护作用没有反应。Rb9诱导肺转移中CD8 + T增加和Foxp3 + T细胞浸润减少，淋巴器官中IFN-γ高和TGF-β低。该肽与F-肌动蛋白和树突状细胞中的核位点共定位，并在点印迹设置中特异性结合MIF和CD74。用Rb9预孵育6 h的鼠骨髓树突状细胞用MIF短时间处理。与单独的MIF相比，调节后的反应显示出CD74的刺激和pPI3K，pERK和pNF-κB的抑制。在黑色素瘤条件培养基中的Rb9，刺激了骨髓巨噬细胞的M1型转化。Rb9的功能方面体内使用黑色素瘤转移模型在治疗和预防方案中进行了研究。在两种方案中，Rb9均显示出显着的抗黑素瘤保护作用。还研究了人树突状细胞，显示出响应Rb9孵育的表面标志物表达增加。Rb9分别受到抑制（TGF-β和IL-10）或激活（LPS）条件的刺激或稍抑制的moDC。用Rb9和肿瘤细胞裂解物刺激的moDC获得淋巴细胞增殖。在来自癌症患者的moDC中，Rb9发挥免疫调节活性，具体取决于其功能状态。该肽可能抑制过度刺激的细胞，刺激活化和抑制能力差的细胞，或者引起很少的表型和功能改变。最近，MIF-CD74的相互作用已与PD-L1表达和IFN-γ相关联，提示黑色素瘤治疗的目标。针对Rb9所述的作用以及针对转移性黑色素瘤的保护作用可能表明，与现代免疫治疗程序相关的肽试剂可能具有相关性。