Whole-body bioluminescence imaging of T-cell response in PDAC models

Abstract

IntroductionThe location of T-cells during tumor progression and treatment provides crucial information in predicting the response in vivo.MethodsHere, we investigated, using our bioluminescent, dual color, T-cell reporter mouse, termed TbiLuc, T-cell location and function during murine PDAC tumor growth and checkpoint blockade treatment with anti-PD-1 and anti-CTLA-4. Using this model, we could visualize T-cell location and function in the tumor and the surrounding tumor microenvironment longitudinally. We used murine PDAC clones that formed in vivo tumors with either high T-cell infiltration (immunologically ‘hot’) or low T-cell infiltration (immunologically ‘cold’).ResultsDifferences in total T-cell bioluminescence could be seen between the ‘hot’ and ‘cold’ tumors in the TbiLuc mice. During checkpoint blockade treatment we could see in the tumor-draining lymph nodes an increase in bioluminescence on day 7 after treatment.ConclusionsIn the current work, we showed that the TbiLuc mice can be used to monitor T-cell location and function during tumor growth and treatment.

Harnessing bioluminescence for drug discovery and epigenetic research

“…These models combine the high sensitivity and real-time dynamics of bioluminescence for in vitro screening and in vivo imaging with the cellular resolution of lacZ or fluorescent reporters (Day et al, 1998;Contag et al, 2000). The everexpanding diversity of luciferin/luciferase systems provides the opportunity to visualise expression of more than one gene of interest in the same animal using luciferase proteins which either require different substrates for activation (Jones et al, 2017) or produce spectrally distinct luminescence signal (Mezzanotte et al, 2011;Gleneadie et al, 2023;McMorrow et al, 2023) (exemplified in Figure 1A, right-hand panel, red and green).…”

“…Using this technique, even a single cell could be detected (Kim et al, 2010;Iwano et al, 2018), with a linear relationship between cell number and signal over 5 logarithmic scales (Contag et al, 2000;Rehemtulla et al, 2000). As the tumour progresses studies have suggested that the luciferase signal begins to plateau, likely due to ongoing necrosis and the low oxygen content in tumour cores (Soling et al, 2004;Jurczok et al, 2008;McMorrow et al, 2023). Bioluminescence has been used extensively for in vivo (O'Farrell et al, 2013;Manni et al, 2019;Alsawaftah et al, 2021) and in vitro (Wang et al, 2006;Badr et al, 2011;Blanquart et al, 2011;Improgo et al, 2011) cancer drug screening, often using the same bioluminescent cancer cell lines for each stage of the study (Qian et al, 2005;Wang et al, 2006;Wang et al, 2023).…”

“…In addition to providing a valuable tool for the visualisation of cancer growth, progression and metastasis, bioluminescence has been harnessed to better understand cancer related processes such as metabolism (Indraccolo and Mueller-Klieser, 2016), apoptosis (Coppola et al, 2008), hypoxia (Miyabara et al, 2023), angiogenesis (Olmeda et al, 2017) and the immune response (McMorrow et al, 2023). This can help develop more targeted therapies and better predict response to treatment.…”

“…The location of T-cells during tumour progression is important for predicting the response to immunotherapy. To model this, a mouse line was generated with two bioluminescent reporters, CBG99Luc was expressed in all T-cells (under the control of the constitutive CD2 promoter) while PpyRE9 was only expressed in activated T-cells (regulated by the LCD2 promoter) (McMorrow et al, 2023). These mice were injected with pancreatic cancer cell lines known to have either high or low T-cell infiltration and the location and function of T-cells in and surrounding the tumour were visualised longitudinally using BLI.…”

“…These mice were injected with pancreatic cancer cell lines known to have either high or low T-cell infiltration and the location and function of T-cells in and surrounding the tumour were visualised longitudinally using BLI. Importantly, total bioluminescence stratified based on the two cell types and increased upon anti-PD1 and anti-CTLA-4 treatment, with more signal from activated T-cells in the tumour-draining lymph nodes (McMorrow et al, 2023). BLI has also been used in a recent study on the effect of inhibiting the histone demethylase, JMJD3, in prostate cancer.…”