Tumor-associated macrophages (TAMs) are an essential component of the tumor microenvironment and are predominantly thought to have pro-tumor effects. Therefore, the development of imaging tracers targeting TAMs is important for tumor monitoring and therapeutic efficacy evaluation. A new study in PNAS reports the development of a nanobody-based immunotracer targeting CD163—a receptor predominantly expressed on macrophages—to non-invasively monitor macrophages in vivo. After developing and radiolabeling the anti-CD163 immunotracer, the investigators injected the tracer in naïve and tumor-bearing mice and performed micro-single-photon emission computerized tomography/computed tomography (μSPECT/CT) and micro-positron emission tomography (μPET)/CT imaging, which confirmed the specific targeting of macrophages and TAMs in mice. Importantly, in tumor-bearing mice treated with immunotherapy, the tracer was able to link TAM localization to therapy responsiveness. This tracer could become a useful tool to monitor TAMs and follow up immunotherapy responses in patients with cancer.
Original reference: Lauwers, Y. et al. Proc. Natl. Acad. Sci. USA 121, e2409668121 (2024)
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