Visualizing Efficacy of Antineoplastic Drug via Ratiometric Near-Infrared Fluorescence Imaging of Tumor-Associated Macrophage-Specific Nitric Oxide

Elevated nitric oxide (NO) within tumor-associated macrophages (TAMs) suggests a reduction of TAM-mediated tumoral immune tolerance. This cellular event could be a reliable indicator for efficacy evaluation of antineoplastic drugs. However, a suitable method for TAM-specific NO measurement is still lacking. In this work, a simple and fast efficacy evaluation method for antineoplastic drugs is established based on a ratiometric TAM-specific NO near-infrared (NIR) fluorescence probe TAM-Cy-NO. Molecular fluorescence probe Cy-NO for NO response was encapsulated in the TAM-targeting peptide (M2pep)-functionalized liposome to construct TAM-Cy-NO. After TAM enters through M2pep, Cy-NO reacts with NO specifically, resulting in a dose-dependent ratiometric fluorescence signal (I610/I815) change manner. Utilizing this strategy, we observed that PLX-3397, metformin, and ibrutinib triggered NO generation within TAM greater than that with sorafenib. Notably, metformin and ibrutinib promoted TNF-α and reduced PD-L1 expressions, which suggest reductions of TAM-mediated immunosuppression. As expected, these drugs delayed tumor progression in mice. This method provides a promising efficacy evaluation strategy for rapid screening of antineoplastic drugs.