A novel molecular probe 131I-K237 targeting tumor angiogenesis in human prostate cancer xenografts

Specific molecular probes are essential for the early diagnosis of prostate cancer. In addition, peptides have been shown to have numerous uses as diagnostic and therapeutic molecular probes. The K237 peptide binds to the vascular endothelial growth factor receptor with high affinity and specificity, and was predicted to have potential use as a probe in tumor angiogenesis. The overall aim of the present study was to assess the diagnostic potential of 131I‑K237 as a molecular probe for prostate cancer. The K237 peptide was radiolabeled with 131I using an Iodogen method. The radiolabeling efficiency and radiochemical purity were found to be 73.7 ± 3.2 and 96.7 ± 0.6%, respectively, which were determined using thin layer chromatography and high performance liquid chromatography in vitro. Cellular uptake and competition binding experiments were used to identify the affinity of 131I‑K237 to LNCaP prostate cancer cells. The binding ratio of 131I‑K237 to LNCaP cells in the experimental group was 95.8 ± 1.5%, whereas the binding ratios in the 5 kBq Na131I, 10 kBq Na131I, 15 kBq Na131I and PBS groups were 8.2 ± 0.4, 8.3 ± 0.2, 8.5 ± 0.2 and 0.0%, respectively. In addition, the binding ratio of 131I‑K237 to LNCaP significantly decreased with the increased dose of unlabeled K237. A total of 40 male BALB/c mice with LNCaP xenografts were used for biodistribution and single photon emission computed tomography imaging analysis. An image was obtained and tumors were visible from 2 h post injection of 131I‑K237. In conclusion, the results of the present study showed that 131I‑K237 had a high affinity for LNCaP cells and may be considered as a candidate diagnostic molecular probe for prostate cancer.