Abstract
CAR T cell therapies for solid tumours face additional challenges, resulting in limited efficacy compared to haematological malignancies. Overcoming obstacles such as trafficking to the tumour site, extravasation and proliferation within an immunosuppressive microenvironment remain challenging. The dynamics of these processes, the whole-body biodistribution and the minimum cell number required for tumour remission, are still not fully understood.Here, a compartmental model was established to characterise the dynamics of 99mTcO4- uptake by CAR T cells, enabling serial and non-invasive monitoring and quantitation of CAR T cell infiltration in a prostate cancer mouse model using single-photon emission computed tomography-computerised tomography (SPECT/CT).
An indirect labelling strategy was implemented by co-expressing the reporter gene hNIS with a second-generation PSMA targeting CAR. These CAR T cells can internalise the clinically relevant tracer technetium pertechnetate (99mTcO4-), facilitating the visualisation of CAR T cell biodistribution in cancer-bearing mice via SPECT/CT. The SPECT/CT images provided valuable insights into CAR T cell infiltration patterns and allowed the serial and real-time monitoring of CAR T cell proliferation in vivo non-invasively. Ex vivo immunohistochemistry analysis confirmed the observed infiltration patterns in vivo, revealing CAR T cells predominantly accumulating around tumour vasculature while absent from the tumour core. Tumour uptake, quantified from SPECT/CT images, correlated with the number of cells quantified by flow cytometry. To better comprehend the dynamics surrounding CAR T cell infiltration and proliferation, a two-compartment model was defined to characterise tracer behaviour in vivo, demonstrating a strong correlation between tracer flow from the bloodstream into the tumour and the number of infiltrating CAR T cells. This work serves as a proof of concept, laying the foundations for the further development of compartmental models as a tool for the non-invasive and in vivo quantitation of genetically modified cell therapies.
| Date of Award | 1 Sept 2024 |
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| Original language | English |
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| Supervisor | Sophie Papa (Supervisor) & Jane Sosabowski (Supervisor) |