Radioactive iodine labeling of monoclonal antibody against Hsp90α and its use in diagnostic imaging in prostate cancer xenograft model

H.-W. Sun, R.-F. Wang, P. Yan, C.-L. Zhang, P. Hao, H. Ma, X.-Q. Chen

Department of Nuclear Medicine, Peking University First Hospital, Beijing, China. rongfu_wang@163.com

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• Oncology

OBJECTIVE: Heat shock protein (Hsp90) resides exclusively in the cytosol in normal cells, but is activated and then removes to the cell surface in tumor cells. The detecting upregulation or activation of Hsp90 is an early indicator of malignant behavior of cancer cells. Hsp90 has emerged as an important target for diagnosis or therapy of prostate cancer. In this study, we labeled Hsp90α specific monoclonal antibody (Hsp90α-mAb) with radioiodine Na131I and investigated its potential usage in diagnostic imaging of prostate tumor in xenograft mice model.

METHODS: Hsp90α-mAb was radioiodinated by using chloramine-T. The radiolabeling efficiency and radiochemical purity were assessed in vitro. 131I-Hsp90α-mAb was then injected into the nude mice bearing human prostate carcinoma. The planar gamma Imaging was performed at 3, 6, 9 and 12 h after injection.

RESULTS: The radiochemical purity of 131I-Hsp90α-mAb exceeded 95% after purification. This radiolabeled mAb was stable in human blood serum. In planar gamma imaging study, the prostate tumors in mice model were imaged clearly at 3h after injection of 131I-Hsp90α-mAb.

CONCLUSIONS: The results suggest that 131I-HSP90α-mAb could be a new promising molecular probe for diagnostic imaging of prostate tumors.

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