Design, synthesis and validation of Axl-targeted monoclonal antibody probe for microPET imaging of human lung cancer.

摘要

Accumulating experimental evidence indicates that overexpression of oncogenic receptor tyrosine kinase, Axl, plays a key role in the tumorigenesis and metastasis of various types of cancer. The objective of this study was to design a novel imaging probe based on the monoclonal antibody, MAb173, for microPET imaging of Axl expression in human lung cancer. A bifunctional chelator, DOTA, was used to radiolabel MAb173 with 64Cu. The receptor binding affinity of 64Cu was evaluated in vitro with human lung cancer cell line. In vivo micro-PET imaging of the Axl-positive A549 xenograft model was carried out to evaluate the Axl targeting probe. In vitro cell uptake assay and flow cytometry analysis were performed to detect the expression level of Axl on A549 cells and the results showed that Axl probes were highly immunoreactive with A549 cells. Subsequently, Axl expression was further analyzed by Western Blot in various liver, breast, lung and Kaposi-sarcoma (KS) cancer cell lines, respectively. Identical to the two positive controls KS-SLK and KS-IMM, Axl is highly expressed in A549 cell line. For microPET imaging in the subcutaneous A549 model, the tumor demonstrated strong uptake compared with the uptake level of the control cell model, H249. Immuno-fluorescence staining also supported the in vivo micro-PET imaging results. Thus, 64Cu-DOTA-mAb173 could be used as a potential probe for noninvasive imaging of Axl expression, which can help us predict whether lung tumors will effectively respond to certain Axl-targeted therapeutic interventions, as well as monitor the corresponding response to therapy.