Fig. 1: Accurate lymph node targeting using image-guided radiotherapy in a murine model of metastatic disease. | Nature Communications

Fig. 1: Accurate lymph node targeting using image-guided radiotherapy in a murine model of metastatic disease.

From: Delayed tumor-draining lymph node irradiation preserves the efficacy of combined radiotherapy and immune checkpoint blockade in models of metastatic disease

Fig. 1

A A luciferase-expressing B16F10 mouse melanoma cell line was used to generate a metastatic melanoma tumor model. The day of tumor IR (day 0) was defined as the day when tumors reached an average size of 80 mm3 (day 6 after cell injection). B Top: Representative image of a tumor-bearing mouse on the day of tumor IR. Bottom: Excised lymph nodes from the same mouse, DLNs on the left and contralateral NDLNs on the right, with the axillary lymph node on top and the inguinal lymph node on the bottom of each image. C Quantitative analysis of the presence of tumor cells in the DLNs on the day of tumor IR. Left: Fold change in the average radiance of the DLN compared to the contralateral NDLN. Dotted line indicates the cutoff value for tumor cell positivity, defined as a 300% increase in the signal over the NDLN (fold change >4). Each dot represents an individual mouse. Right: Quantitative representation of the mice with tumor cell positive DLNs on the day of tumor IR, using the cutoff value defined above. n = 5 mice. D CT image on the day of tumor IR. Orange arrows point to the axillary and brachial (top), and inguinal DLNs (bottom). Blue arrow indicates the tumor. E Radiotherapy treatment plans. Left: Tumor-only IR is performed using a rectangular 8 × 12 mm field, shown in blue. Right: Two additional circular 5 mm fields (in orange) are used to target the DLNs. F Mouse with depigmentation corresponding to area of skin exposed to IR during tumor and DLN IR, photographed on day 60 after delivering 15 Gy. G γH2AX staining performed 30 min after delivering 15 Gy. Top row: DLN, bottom row: contralateral NDLN. Left column: planning CT only, middle column: planning CT and tumor IR, and right column: planning CT, tumor IR and DLN IR. Representative sections from n = 1 mouse per treatment group, 6 lymph nodes per mouse. Source data are provided as a Source Data file. Figures A and D, created with BioRender.com, released under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International license.

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