Therapy To Target Renal Cell Carcinoma Using ¹³¹I-labeled Human B7-h3 Monoclonal Antibody

Renal cell carcinoma（RCC） is the most common malignant tumor in the adult kidney. Clear-cell renal cell carcinoma subtype（cc RCC） is the most frequent, accounting for >80% of all RCCs. Radical surgery is the most effective treatment option for early stage RCC. The lack of any demonstrable efficacy from chemotherapy and radiation therapy in advanced RCC has led to poor suvival. Targeted agents against VEGF, VEGFR, or m TOR continue to play a crucial role in the management of metastatic cc RCC. Because of their limited clinical therapeutic effects and unique adverse reactions of targeted therapy, further application in clinical is limited. B7-H3 was identified as the most differentially expressed cell-surface tumor-specific endothelial marker, and it plays a critical role in potential tumor-targeted therapy.In this study, patients with cc RCC who underwent surgery for radical nephrectomy were included.We analyzed the relationship between B7-H3 and clinical characteristics.We aimed to assess the radiobiological effect of ¹³¹I-labeled human B7-H3 monoclonal antibody(¹³¹I-4H7) in nude mice with human cc RCC and evaluate the effect of ¹³¹I-4H7 on cc RCC treatment. The radiobiological activity and tumor uptake of ¹³¹I-4H7 was measured by tissue distribution assay, and its effect on tumor growth was measured by monitoring tumor size.This study consists of three parts.PartⅠExpression and clinical significance of B7-H3 in renal cell carcinomaObjective: To detect the expression level of B7-H3 in serum and tissue samples of renal cell carcinoma（RCC） patient, and analyze the relationship between B7-H3 levels and clinical factors.Methods: B7-H3 expression of serum was detected by using ELISA in RCC patients and healthy volunteers, and the correlation between B7-H3 levels and clinical factors was assessed. Furthermore, we evaluated the expression levels of B7-H3 in 126 cases of RCC, and analyzed the relationship bewteen B7-H3 expression and clinical pathologic features.Results: The levels of s B7-H3 expression in human RCC were significantly higher than those healthy volunteers（P<0.01）. The high levels of s B7-H3 in patients with RCC were found to be correlated with the clinical stage and lymph node metastasis. The expression levels of B7-H3 were higher in the samples of RCC than in samples of nomal renal tissues. Furthormore, 106 cases（80.95%） showed B7-H3 postive expression in tumor vascular endothelial cellsConclusion: The expression levels of s B7-H3 are significantly upregulated in serum of patients with RCC, indicating that B7-H3 dysregulation might be important in the progression of RCC. B7-H3 was highly expressed in the samples of RCC, especially in the tumor vascular endothelial cells, indicating that B7-H3 might play an important role in angiogenesis of RCC.PartⅡ Preparation and biological evalution of ¹³¹I labeling anti-B7-H3 monoclonal antibody 4H7Objective: B7-H3 plays a critical role in tumor angiogenesis and metastasis. We therefore aimed to assess the radiobiological effect of ¹³¹I labeled human B7-H3 monoclonal antibody(¹³¹I-4H7) in nude mice with human renal cell carcinoma（RCC）.Methods: Chloramine-T method was used for ¹³¹I labeling 4H7. Labeling efficiency, radiochemical purity and stability were estimated by using paper chromatography method. The activity and tumor uptake of ¹³¹I-4H7 was measured by tissue distribution assay and SPECT imaging after injection of ¹³¹I-4H7.Results: The labeling efficiency and radiochemical purity of ¹³¹I-4H7 were 61.64%, 98.4%, respectively. The in vivo distribution and elimination of ¹³¹I-4H7 were consistent with a first-order and two-compartment model, t1/2α=27.94 min, t1/2β=1634.74 min.The metabolism of ¹³¹I-4H7 mainly depend on liver and kidney.The tissue distribution assay and SPECT imaging showed that ¹³¹I-4H7 was markedly absorbed by the tumor and reached its maximal uptake rate（3.32%ID/g） at 24 hours. Compared with the Na¹³¹I group, the ¹³¹I-4H7 group show higher uptake of ¹³¹I at each time point.Conclusion: The labeling rate and radiochemical purity of ¹³¹I-4H7 is high, simple and the stability of ¹³¹I-4H7 is fine. ¹³¹I-4H7 is a promising agent of radioimmunoimaging and radioimmuotherapy for renal cell carcinoma. Part Ⅲ Therapy to target renal cell carcinoma using¹³¹I-labeled human B7-H3 monoclonal antibodyObjective: In this study, we aimed to assess the radiobiological effect of ¹³¹I-labeled human B7-H3 monoclonal antibody(¹³¹I-4H7) in nude mice with human renal cell carcinoma（RCC） and evaluate the effect of ¹³¹I-4H7 on RCC treatment.Methods: The effect of ¹³¹I-4H7, ¹³¹I-m Ig G, Na¹³¹I, and saline on tumor xenograft growth in nude mice on tumor growth was measured by monitoring tumor size and was evaluated by static micro positron emission tomography-computed tomography（PET-CT） at different time points（0, 7, 14, 21d） after intravenous injection of 18F-RGD.Results: Measurements showed that tumor development was significantly inhibited by ¹³¹I-4H7. At day 21, the group treated with ¹³¹I-4H7 showed a 48.81% inhibition of tumor growth. There was also a significant difference between the group injected with ¹³¹I-4H7 and that injected with ¹³¹I-m Ig G（22.41%）, which suggested that ¹³¹I-4H7 acted more significantly to suppress tumor growth than ¹³¹I-m Ig G（P<0.05）. At day 7, 14, and 21, micro PET-CT showed that the xenografted tumors uptake of 18F-RGD was significantly decreased in the group treated with ¹³¹I-4H7.Conclusion: Our results suggest that ¹³¹I-4H7 is markedly absorbed by the tumor and did suppress the development of RCC xenografted tumors in nude mice, which might provide a new candidate for antibody-mediated targeted radiotherapy in human RCC.