A Radioactive and Fluorescent Dual Modality Cysteine Cathepsin-B Activity-Based Probe for Cancer Theranostic

Abstract

AbstractPurpose:Cysteine cathepsin B (CTS-B) is a crucial enzyme that is overexpressed in numerous malignancies and contributes to the invasion and metastasis of cancer. Therefore, this study set out to develop and evaluate an activity-based multi-modality theranostic agent targeting CTS-B for cancer imaging and therapy.Methods:A CTS-B activity-based probe, BMX2, was synthesized and labeled efficiently with68Ga and90Y to produce68Ga-BMX2 for multi-modality imaging and90Y-BMX2 for radiation therapy. The affinity and specificity of the BMX2 binding with the CTS-B enzyme were determined by fluorescent western blot using recombined active human CTS-B enzyme (rh-CTS-B) and four cancer cell lines including HeLa, HepG2, MCF7, and U87MG with CA074 as CTS-B inhibitor for control. Confocal laser scanning microscope imaging and cell uptake measurement was also performed. Then in vivo PET imaging and fluorescence imaging were acquired on HeLa xenografts. Finally, the therapeutic effect of90Y-BMX2 was tested.Results:BMX2 could be specifically activated by rh-CTS-B and stably bound to the enzyme. The binding of BMX2 with CTS-B has a time-dependent and enzyme concentration-dependent manner. Although CTS-B expression varied between cell lines, all showed significant uptake of BMX2 and68Ga-BMX2. In vivo optical and PET imaging showed high tumor uptake of BMX2 and68Ga-BMX2 and accumulated for more than 24 hours. The90Y-BMX2 could significantly inhibit HeLa tumor growth.Conclusion:The development of68Ga/90Y-BMX2, a radioactive and fluorescent dual modality theranostic agent, demonstrated an effective theranostic approach for PET diagnostic imaging, fluorescence imaging, and radionuclide therapy of cancers, which may have a potential for clinical translation for cancer theranostic in the future.