Novel affibody molecules targeting the AXL extracellular structural domain for molecular imaging and targeted therapy of gastric cancer.

Gastric cancer (GC) has a poor prognosis and high mortality because it is often diagnosed at an advanced stage. Targeted therapeutics are considered an important class for advanced GC treatment. However, the fewer effective therapeutic targets and the poor coverage of the GC population limit the use of GC targeted therapies. Recent research suggests that the AXL receptor tyrosine kinase (AXL) plays an vital role in the survival and proliferation of GC cells, and blocking AXL pathway may be an effective strategy for targeted therapies. On the other hand, the affibody molecule, with its small size and faster penetration of tissue, has great potential in tumor imaging and targeted therapy. In this study, we report the novel AXL-binding affibody molecules (Z(AXL):239) screened by a phage-displayed peptide library. The Z(AXL):239 could specifically bind and interact with AXL proteins in vitro and in vivo, as demonstrated by surface plasmon resonance, co-immunoprecipitation, immuno-fluorescence co-localization, and near infrared fluorescent imaging. In addition, Z(AXL):239 affibody molecules could significantly inhibit the proliferative activity and induce apoptosis of AXL-positive GC cells by decreasing the phosphorylation levels of the PI3K/AKT1 and MEK/ERK pathway, leading to the suppression of the downstream nuclear protein c-myc. Moreover, Z(AXL):239 was found to have significant anti-tumor effects in AXL-positive GC transplantation tumor nude mouse models. In brief, we provide strong evidence that the novel Z(AXL):239 affibody molecules have great potential as a potent tumor-specific molecular imaging and targeted therapeutic agents for GC.