State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, First Affiliated Hospital, Zhejiang University College of Medicine, Hangzhou, Zhejiang 310003, PR China.
Mol Cancer. 2011 Jul 12;10:82. doi: 10.1186/1476-4598-10-82.
Overexpression of the RON receptor tyrosine kinase contributes to epithelial cell transformation, malignant progression, and acquired drug resistance. RON also has been considered as a potential target for therapeutic intervention. This study determines biochemical features and inhibitory activity of a mouse monoclonal antibody (mAb) Zt/f2 in experimental cancer therapy.
Zt/f2 is a mouse IgG2a mAb that is highly specific and sensitive to human RON and its oncogenic variants such as RON160 (ED(50) = 2.3 nmol/L). Receptor binding studies revealed that Zt/f2 interacts with an epitope(s) located in a 49 amino acid sequence coded by exon 11 in the RON β-chain extracellular sequences. This sequence is critical in regulating RON maturation and phosphorylation. Zt/f2 did not compete with ligand macrophage-stimulating protein for binding to RON; however, its engagement effectively induced RON internalization, which diminishes RON expression and impairs downstream signaling activation. These biochemical features provide the cellular basis for the use of Zt/f2 to inhibit tumor growth in animal model. Repeated administration of Zt/f2 as a single agent into Balb/c mice results in partial inhibition of tumor growth caused by transformed NIH-3T3 cells expressing oncogenic RON160. Colon cancer HT-29 cell-mediated tumor growth in athymic nude mice also was attenuated following Zt/f2 treatment. In both cases, ~50% inhibition of tumor growth as measured by tumor volume was achieved. Moreover, Zt/f2 in combination with 5-fluorouracil showed an enhanced inhibition effect of ~80% on HT-29 cell-mediated tumor growth in vivo.
Zt/f2 is a potential therapeutic mAb capable of inhibiting RON-mediated oncogenesis by colon cancer cells in animal models. The inhibitory effect of Zt/f2 in vivo in combination with chemoagent 5-fluorouracil could represent a novel strategy for future colon cancer therapy.
RON 受体酪氨酸激酶的过表达有助于上皮细胞转化、恶性进展和获得药物耐药性。RON 也被认为是治疗干预的潜在靶点。本研究确定了一种小鼠单克隆抗体（mAb）Zt/f2 在实验性癌症治疗中的生化特征和抑制活性。
Zt/f2 是一种小鼠 IgG2a mAb，对人 RON 及其致癌变体（如 RON160，ED（50）=2.3nmol/L）具有高度特异性和敏感性。受体结合研究表明，Zt/f2 与 RON β 链细胞外序列中由外显子 11 编码的 49 个氨基酸序列的一个（些）表位相互作用。该序列对于调节 RON 的成熟和磷酸化至关重要。Zt/f2 不与配体巨噬细胞刺激蛋白竞争与 RON 的结合；然而，它的结合有效地诱导了 RON 的内化，从而降低了 RON 的表达并损害了下游信号转导的激活。这些生化特征为 Zt/f2 用于抑制动物模型中肿瘤生长提供了细胞基础。在 Balb/c 小鼠中作为单一药物重复给予 Zt/f2 导致表达致癌性 RON160 的转化 NIH-3T3 细胞引起的肿瘤生长部分抑制。经 Zt/f2 处理后，裸鼠中 HT-29 细胞介导的肿瘤生长也减弱。在这两种情况下，通过肿瘤体积测量均实现了约 50%的肿瘤生长抑制。此外，Zt/f2 与 5-氟尿嘧啶联合使用可增强体内 HT-29 细胞介导的肿瘤生长的抑制作用，约为 80%。
Zt/f2 是一种潜在的治疗性 mAb，能够抑制动物模型中结肠癌细胞的 RON 介导的致癌作用。Zt/f2 在体内与化疗药物 5-氟尿嘧啶联合使用的抑制作用可能代表未来结肠癌治疗的一种新策略。
