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Objective Through improving the potential of vascular endothelial growth factor receptor (VEGFR)-humanized mouse model (hKDR+/+) with C57BL/6N background to allow the growth of different mouse tumor cell lines, to establish novel tumor-bearing mouse models which can support in vivo tumorigenesis of different mouse tumor cell lines and be used to evaluate drugs targeting VEGFR. Methods Firstly, a method to evaluate the in vivo activity of antibody targeting VEGFR based on the hKDR+/+ humanized mouse model was established. Recombinant activating gene 1 (Rag1) knockout mice (Rag1-/-) were established using CRISPR/Cas9 technology. Then these Rag1-/- mice were crossed with hKDR+/+ mice to get a double gene modified homozygous hKDR+/+/Rag1-/- mouse model by screening. Finally, tumor cell lines derived from different mouse strains were tested on the double gene-modified mouse model to compare the differences in tumor growth. Results Antibodies designed for VEGFR showed significant anti-tumor activity in hKDR+/+ mice, which significantly reduced tumor volume and weight compared with the PBS group (P<0.01, P<0.05). The number of B cells and T cells in the peripheral blood of Rag1-/- mice and hKDR+/+/Rag1-/- mice decreased (P<0.05, P<0.001). Tumors were observed in hKDR+/+/Rag1-/-, Rag1-/-, wild-type, and hKDR+/+ mice after 7 d of inoculation of MC38 cells derived from C57BL/6 mice. Tumors were only observed in groups of hKDR+/+/Rag1-/- and Rag1-/- mice, but not in the wild-type and hKDR+/+ mice after 10 d of inoculation with CT26 cells derived from BALB/c mice. After 3 weeks of inoculation, the tumor volume of hKDR+/+/Rag1-/- mice was significantly larger than that of Rag1-/- mice (P<0.01). Conclusion Rag1 knockout mice were obtained and a novel hKDR+/+/Rag1-/- double genes modified mouse model was further screened. The tumor cell lines from different mouse strain origins were more prone to growth in mice with Rag1 gene deficiency. The results suggest that the reduced immune response of hKDR+/+ humanized mice will improve the capacity of supporting the growth of mouse tumor lines in the model. As a result, more tumor-bearing mouse models may be constructed for the evaluation of drugs targeting VEGFR in this way. [ABSTRACT FROM AUTHOR]